In known portable analog communication devices, even when a data signal is dealt with, the signal is always passed through a band-pass filter designed for filtering a voice signal and thus the data signal encounters an error due to group delay distortion. A portable analog communication device includes: an RF demodulator for demodulating a received RF signal; a first filter for filtering the output signal of the RF demodulator; a second filter having a low group delay; filter connection means for selecting the second filter when the RF signal is a data signal; and device selection means for selecting a device the output signal of the signal processing circuit is provided to depending on whether the RF signal is a voice signal or a data signal.

1. Field of the Invention
The present invention relates to a portable analog communication device having the capability of filtering voice and data signals which have been received or are to be transmitted.
2. Description of the Related Art
In a portable analog communication system, the frequency division multiplex technique is employed to utilize communication channels in a highly efficient manner. For example, in the case of the analog cellular telephone system of AMPS (Advanced Mobile Phone Service) serviced in North America, frequencies 869.04+0.03*n MHz are assigned to receiving channels while frequencies 824.04+0.03*n MHz (n=0 to 831) are assigned to transmitting channels. In such the system, the frequency bandwidth available for each voice communication channel is as narrow as 300-3400 Hz. Therefore, a filter is required to remove a high-frequency component from a signal. However, the known portable analog communication systems are designed for use in speech communication, and therefore the phase change caused by the filter is not taken into account in the design. In recent years, however, data communication using a modem has become popular, and a portable analog telephone device is now often used in data communication. However, the data rate via the portable analog telephone system is as low as 2400 bps. The low data rate mainly results from the following three factors. They are fading, hand-over, and group delay. The fading refers to a voltage (electric filed) variation in a received signal which occurs owing to interference between multiple radio waves propagating via multiple transmission paths. The fading is a problem inherent in the mobile communication. A sudden reduction in the electric field due to the fading causes a reduction in the signal-to-noise ratio, which in turn results in an increase in BER (bit error rate). In the case where the data is character data, the error will produce an incorrect character in the received data. The hand-over refers to the operation of automatically switching a telephone call when a portable telephone moves from a service area of a base station to an adjacent service area. The data lost during a switching time period is transmitted again.
The improvement of the problem associated with the group delay will be discussed below. First, a group delay caused by a filter will be discussed. In the case of a first-order LPF (low pass filter) shown in FIG. 10, the current I passing through the filter can be written as: EQU I=(Vin-Vout)/R=Vout/(1/j.omega.C)
where Vin denotes the input voltage (in V), Vout the output voltage (in V), R the resistance, C the capacitance, and .omega. the angular frequency (in rad/s). From the above equation, the transfer function T(j.omega.) can be obtained as follows: EQU T(j.omega.)=Vout/Vin=1/(1+j.omega.CR) (1)
If cutoff frequency .omega.o=1/CR is introduced into the above equation, then the characteristics associated with amplitude .vertline.T(j.omega.).vertline., phase .angle.T(j.omega.), and group delay .tau.(j.omega.) are given as follows: EQU .vertline.T(j.omega.).vertline.=1/.sqroot.(1+(.omega./.omega.o).sup.2)(2) EQU .angle.T(j.omega.)=-arctan((.omega./.omega.o)) (3) EQU .tau.(j.omega.)=-d[.angle.T(j.omega.)]/d.omega. (4)
The cutoff frequency o refers to a frequency at which a 3-dB reduction occurs in the amplitude .vertline.T(j.omega.).vertline.. Filters cause a change not only in the amplitude characteristic .vertline.T(j.omega.).vertline. but also in phase characteristic .angle.T(j.omega.). In the case of the above specific example, as can be seen from equation (3), a delay of 90 occurs for .omega.>>.omega.o. A great phase delay occurs near the cutoff frequency .omega.o. The group delay .tau.(j.omega.) is obtained by differentiating the phase .angle.T(j.omega.) with respect to the angular frequency .omega., and thus the group delay .tau.(j.omega.) indicates the degree of change in phase. Therefore, the group delay becomes large near the cutoff frequency .omega.o. The group delay becomes approximately 500 .mu.sec at .omega.o with respect to the delay for DC (0 Hz). A greater attenuation can be obtained by increasing the number of stages constituting a filter. However, the variation in phase and the group delay also increase with the number of stages. The transfer function is usually represented using a complex variable s. Thus, equation (1) becomes: EQU t(s)=1/(s+1) (5)
This is the general expression of the first-order LPF.
FIG. 11 is a block diagram of the receiver section of a known portable analog telephone device having the capability of data/facsimile communication. In this figure, 1a denotes an RF demodulator which demodulates a received signal in a baseband signal; 2 denotes an audio frequency band-pass filter which extracts a signal component in an audio frequency band 300-3400 Hz from a baseband signal and selectively outputs the resultant signal; 3a denotes a voice signal processing circuit called a de-emphasis/expander that performs a predefined receiving operation; and 4a is a selection switch for selecting a device the output signal of the voice signal processing circuit 3a is provided to. In speech communication, the output of the voice signal processing circuit 3a is connected to a loudspeaker circuit 5 via the switch 4a. In data/facsimile communication, the switch 4a provides the output signal of the voice signal processing circuit 3a to a modem 7 and further to a personal computer 9 via a transceiver 8 with an RC-232 and V.28 communication interface. The processing described above is controlled by a central processing unit 6. A portable analog telephone device includes an interface terminal for interfacing an external device such as a headphone or an optional device usually called a hands-free adapter. A user can also use the interface terminal when performing data/facsimile communication.
Now, the operation will be described with reference to the figures. A portable analog telephone device such as that shown in FIG. 11 has been originally designed for use in speech communication. Therefore, the audio frequency band-pass filter 2 is designed without taking into consideration the group delay distortion within the passband. Instead, much consideration about the amplitude attenuation characteristic outside the passband is taken in the design so as to minimize the influence on adjacent channels. As a result, group delay distortion of 3 to 5 ms usually occurs within the audio frequency band. Among the overall group delay which occurs in the audio frequency circuits, the majority of the group delay occurs in the audio frequency band-pass filter 2. On the other hand, in data/facsimile communication, the group delay distortion which occurs on a transmission channel has a great influence on the characteristics of a data signal. If the group delay distortion becomes large to a level which can no longer be neglected with respect to the data bit rate, interference between data bits occurs, which causes distortion in the signal. As a result, incorrect reception due to a data error occurs.
FIG. 12 is a block diagram of a transmitter section employed in a known portable analog telephone device having the capability of data/facsimile communication. As shown in FIG. 12, a voice signal, which is given in the form of an electric signal via a microphone 11, is directed via a switch 4b to an audio frequency band-pass filter 10, which in turn extracts a signal having frequency components in the range from 300 to 3400 Hz and outputs the resultant signal to a voice signal processing circuit 3b including a preemphasis circuit, a compressor and a limiter. The voice signal processing circuit 3b also includes a filter for removing harmonic components and thus extracting a low-frequency component from the input signal. This filter is designed to have a large cutoff frequency and to be of rather low order so that the group delay in the audio frequency range (300 Hz to 3.4 kHz) becomes low enough. The output signal of the filter is then modulated by an RF modulator 1b and is output as an RF signal. When data/facsimile communication is performed, the data output from a personal computer 9 is input to a modem 7 via a transceiver 8 with an RC-232/V.28 communication interface. The output signal of the modem is directed via the switch 4b to the audio frequency band-pass filter 10. After that, the signal is passed through the same path as the voice signal and is finally output as an RF signal. The switch 4b, the audio frequency band-pass filter 10, the voice signal processing circuit 3b, and the RF modulator 1b are all controlled by the central processing unit 6. In the transmitter section, as in the receiver section, the audio frequency band-pass filter 10 is designed with a great consideration on the amplitude attenuation characteristic outside the passband. As a result, group delay distortion of 3 to 5 ms usually occurs within the audio frequency band range from 300 to 3400 Hz.
In the known portable analog telephone device, as described above, when data/facsimile communication is performed, data is passed through the same signal path as the existing path designed to process a voice signal. As a result, the data signal encounters group delay distortion which can cause an error in the data.

Portable analog communication device with selectable voice and data filters


A liquid droplet ejecting unit is disclosed wherein plural liquid droplet ejecting sub-units are provided which are arrayed in a direction substantially perpendicular to a conveying direction of a recording medium. Further, plural valves are provided which connect the respective liquid droplet ejecting sub-units and a liquid feed path. The valves comprise a valve body having an inlet port and an outlet port, and a floating member. The floating member is larger in radius than the inlet port and smaller in radius than the outlet port and has a lower specific gravity that the liquid. Thus, the floating member is floated in the liquid in the valve body and capable of closing the inlet port. An image forming apparatus using such a liquid droplet ejecting unit is also disclosed.

1. Field of the Invention
The present invention generally relates to an image forming technique. More particularly, the present invention pertains to a liquid droplet ejecting unit in which plural liquid droplet ejecting sub-units that eject droplets of a liquid fed through a common liquid feed path from nozzles onto a recording medium are arrayed in a direction perpendicular to the conveying direction of the recording medium; an image forming apparatus including this liquid droplet ejecting unit; and a valve that is provided in a vertically extending liquid flow path along which the liquid is fed downward.
2. Description of the Related Art
A structure has conventionally been devised in which a long inkjet recording unit (liquid droplet effecting unit) having a recording region of the width of a recording medium or longer (the length in a direction perpendicular to the conveying direction of the recording medium) and plural short sub-units (liquid droplet ejecting sub-units) having a recording region shorter than the width of the recording medium are arrayed in the widthwise direction of the recording medium.
In the above structure, when the sub-units are connected together via a common ink feed path and a suctioning operation for suctioning the ink from the nozzles is performed on a per sub-unit basis, there is a tendency that a suctioning pressure acts on the remaining sub-units in which no suctioning operation is performed, via the ink feed path. For this reason, a negative pressure occurs due to the ink being caused to flow backward in the remaining sub-units in which no suctioning operation is performed, and thus air is suctioned from the nozzles so that air bubbles are formed, whereby a satisfactory resumption action is prevented.
It has conventionally been proposed to provide a check valve at the ink feed port of an inkjet recording head unit (for example refer to JP-A No. 2002-307716, JP-A No. 4-341854, and JP-A No. 2004-58675). Therefore, in the above-mentioned structure, it might be imagined that formation of air bubbles could be prevented by providing a check valve at the ink feed port of each sub-unit so as to prevent the ink from being caused to flow backward in the other sub-units.
However, in the above-mentioned JP-A No. 2002-307716, JP-A No. 4-341854, and JP-A No. 2004-58675, the specific gravity of a spherical member that opens and closes the check valve is selected to be about equal to that of the ink. For this reason, the spherical member remains submerged in the ink except during a suctioning operation, and after the suctioning operation is started, the spherical member is displaced in following the flow of the ink so as to close the check valve. Obviously, this check valve has poor readiness of the checking operation. Thus, a time lag occurs between when the suctioning operation is started and when the check valve is closed, and there is a problem such that air bubbles occur as a result of ink flowing backward during the time lag.
Meanwhile, it is possible to improve the readiness of the check valve for the checking operation by previously causing the spherical member to be biased in the direction of backward flow of the ink, by means of a spring or the like, as in the case of an ordinary check valve. However, in such a case, there is another problem that an increased pressure loss is caused due to an increase in the load of an opening operation when the ink is fed in a normal direction.

Liquid droplet ejecting unit, image forming apparatus and valve


A device and method of forming the device that includes a first substrate having a cavity on a bottom surface of the first substrate and MEMS components formed on the first substrate and in the cavity; a second substrate having an upper surface; a first metal bond that extends around a perimeter of the cavity and forming a first connection between the bottom surface of first substrate and the upper surface of the second substrate; a second metal bond that extends around a perimeter of the first metal bond and spaced from the first metal bond, the second metal bond forming a second connection between the bottom surface of the first substrate and the upper surface of the second substrate; where the MEMS components are hermetically sealed between the first and second substrates. A getter agent can be between the first and second metal bonds.

Products collectively called microelectromechanical systems (MEMS) devices are usually small, lightweight devices on the micrometer to millimeter scale, which may have mechanically moving parts and often movable electrical power supplies and controls, or they may have parts sensitive to thermal, acoustic, or optical energy. Because of their moving and sensitive nature, MEMS devices are physically and atmospherically protected. Consequently, MEMS devices are usually placed on or in a substrate and contained with a housing or package, which is configured to shield the MEMS components against ambient and electrical disturbances and conditions, and against stress; however, this is optional.
A microelectromechanical systems (MEMS) device integrates one or more mechanical elements, sensors, actuators, or the like together with associated electronics on a common substrate. The manufacturing approach for a MEMS device aims at using batch fabrication techniques similar to those used for other microelectronics devices. MEMS devices can thus benefit from mass production and minimized material consumption to reduce the manufacturing cost, while trying to exploit well controlled integrated circuit technology.
Examples of MEMS devices include mechanical sensors, pressure sensors including microphone membranes, and inertial sensors such as accelerometers coupled with the integrated electronic circuit of the chip. The mechanically moving parts of a MEMS device are fabricated together with the sensors and actuators in the process flow of the electronic integrated circuit (IC) on a semiconductor chip. The mechanically moving parts may be produced by an undercutting etch during the IC fabrication. Examples of specific bulk micromachining processes employed in MEMS sensor production to create the movable elements and the cavities for their movements are anisotropic wet etching and deep reactive ion etching.
Another example is a digital infrared (IR) temperature sensor made in a silicon chip, which includes a thermopile (multiple thermocouple elements) of bismuth/antimony or constantan/copper pairs on a sensor membrane suspended in a cavity created by anisotropic silicon wet etching through a grid of holes. The cavity is closed by laminating another membrane over the membrane to protect the sensors.
One of the problems associated with the formation of these MEMS devices is that during the temperature ramp to bond together two substrates, water and other material that was adsorbed on the substrate surfaces is released, thereby interfering with the sealing target pressure for the MEMS device. Accordingly, for high vacuum MEMs devices, such additional pressure that results from the release of water and other material can cause premature failure.
For some wafer-level packaging applications, a heating step may be performed before bonding to drive the adsorbed water from the substrate surfaces. However, for applications with low temperature bond metallurgies (e.g., gold and indium), heating the wafer before forming the bond can result in premature intermetallic formation, thereby interfering with or preventing hermetic sealing by the bond lines.

Package moisture control and leak mitigation for high vacuum sealed devices


A circuit and method of reducing noises for improving quality of display in a liquid crystal display (LCD) system. The LCD system includes an LCD panel and at least one lamp. In operation the LCD system is supplied with a vertical synchronization signal and a horizontal synchronization signal. In one embodiment, the method comprises the steps of determining a lamp driving frequency for the at least one lamp responsive to the horizontal synchronization signal, and generating a lamp driving signal with the lamp driving frequency to be received by the at least one lamp for producing light, wherein the following formulae (1) and (2) are satisfied:

An liquid crystal display (LCD) apparatus includes an LCD panel formed with liquid crystal cells and pixel elements with each associating with a corresponding liquid crystal cell and having a liquid crystal capacitor (hereinafter "CLC") and a storage capacitor (hereinafter "CST"), a thin film transistor (TFT) electrically coupled with the CLC and CST. These pixel elements are substantially arranged in the form of a matrix having a number of pixel rows and a number of pixel columns. Typically, a plurality of gate signals (scanning signals), generated in response to a horizontal synchronization signal and a vertical synchronization signal, are sequentially applied to the number of pixel rows for sequentially turning on the pixel elements row-by-row. When a gate signal is applied to a pixel row to turn on corresponding TFTs of the pixel elements of a pixel row, a plurality of source signals (data signals) for the pixel row, associated with an image signal to be displayed, are simultaneously applied to the number of pixel columns so as to charge the corresponding CLC and CST of the pixel row for aligning states of the corresponding liquid crystal cells associated with the pixel row to control light transmittance therethrough. By repeating the procedure for all pixel rows, all pixel elements are supplied with corresponding source signals of the image signal, thereby displaying the image signal thereon. The display of the image signal is in generally controlled by the horizontal synchronization signal and the vertical synchronization signal. Typically, in one period of the vertical synchronization signal, all rows are successively scanned once. The number of times a pixel element of a pixel column is scanned in a second is the frequency of the vertical synchronization signal.
Since liquid crystal molecules in the liquid crystal cells themselves do not emit light, an LCD system usually uses a backlight module or a backlight to illuminate the liquid crystal panel so as to produce an image. A backlight includes lamps, such as cold cathode fluorescent lamps (hereinafter "CCFL"), hot cold cathode fluorescent lamps (hereinafter "HCFL"), external electrode fluorescent lamp (hereinafter "EEFL"), or like, for producing light. These lamps are typically powered by a DC-to-AC inverter. The inverter in turn is powered by another power source such as an LCD power supply. The DC-to-AC inverter converts a DC voltage into a high AC voltage (500-2000 V) for driving the lamps, and regulates light-on and light-off times of the lamps for adjusting the brightness of the liquid crystal panel. To reduce interference noises into circuits of the LCD system from the lamps, all lamps are usually driven in the same period and synchronized with each other.
However, interference noises between signals driving the lamps and the horizontal and vertical synchronization signals may exist and generate a so-called "ripple phenomenon" on a screen of the LCD system, which degrades the displaying quality of the LCD system. For example, if a burst mode inverter is used in a conventional LCD system as the DC-to-AC inverter, when the burst signal frequency of the burst mode inverter is equal or near the frequency of the vertical synchronization signal or its harmonics, a large interference noise will be generated periodically. This periodic noise will appear and disappear on the display screen and generate the ripple phenomenon. For instance, if the frequency of the vertical synchronization signal is 60 Hz, when the burst signal frequency of the burst mode inverter is in harmonics of 60 Hz such as 60 Hz, 120 Hz, 180 Hz, 240 Hz . . . , significant noise will result. The burst signal frequency is often preferably set to be about 150 Hz or higher to avoid being close to the harmonics or flicker perceived by human eyes. However, the tolerance of the burst mode frequency could be big due to tolerances of temperature-dependent components, including especially capacitors, the inverter controller IC. Therefore, the burst mode frequency is not as stable as one would like and the ripple phenomenon is very much a concern.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.

Circuit and method for improving image quality of a liquid crystal display

Abstract: f          lamp                =                                                                              2                                    n                                -                1                            m                                                  H              sync                                +          δ                                    (        1        )                                          and                                                                                H              sync                        /            m                          ≥        δ        ≥        0                            (        2        )            where Hsync is the frequency of the horizontal synchronization signal in unit of (Hz); flamp is the lamp driving frequency for the lamp driving signal in unit of (Hz); m, n=1, 2, 3, . . . , an integer; and δ indicates the permissible error of the lamp driving frequency.


High-power, diode-pumped solid state (DPSS) pulsed lasers are preferred for applications such as micromachining, via drilling of integrated circuits, and ultraviolet (UV) conversion. Nd:YVO4 (vanadate) lasers are good candidates for high power applications because they feature a high energy absorption coefficient over a wide bandwidth of pumping wavelengths. However, vanadate has poor thermo-mechanical properties, in that the material is stiff and fractures easily when thermally stressed. By optimizing laser parameters and selecting pumping wavelengths and doping a concentration of the gain medium to control the absorption coefficient less than 2 cm−1 such as the pumping wavelength between about 910 nm and about 920 nm, a doped vanadate laser may be enhanced to produce as much as 100 W of output power without fracturing the crystal material, while delivering a 40% reduction in thermal lensing.

A laser amplifies light by concentrating an external source of energy into light waves of a particular wavelength and direction so that resulting light waves are spatially and temporally aligned, or in phase. A laser medium may be a gas, a liquid, or a solid state material such as a crystal. A crystal laser medium may be doped with atoms of another material to alter the properties of the laser medium.
As is well known to those skilled in the art, basic operating principles of a laser are understood to be as follows: when a laser medium is energized, electrons within atoms comprising the laser medium are temporarily elevated to a higher atomic energy level, a process called pumping absorption. When high-energy electrons return to a lower energy state, the atom emits light at a wavelength determined by the separation between the two energy levels. This process is called stimulated or spontaneous emission, and visible light emitted during the emission process is referred to as fluorescence. To achieve amplification at a particular wavelength, the number of stimulated emission events must exceed the number of stimulated absorption events, a condition called a population inversion that requires maintaining more electrons at the upper energy level than at the lower level. This population inversion is achieved by "pumping" the laser with an external source of energy, such as an electric current or another laser beam. By containing a lasing medium in a box, or cavity, with light-reflective interior surfaces, light waves produced by stimulated emission resonate within the cavity and reinforce one another to form a coherent, collimated beam. A portion of the coherent laser beam thus produced is permitted to escape through one end of the cavity. A pulsed laser beam may be generated by periodically interrupting a continuous beam. Typical pulse repetition frequencies exceed 100,000 pulses per second, or 100 kHz.
Laser pumping efficiency is expressed by a "quantum defect" level, defined as the percentage of pumping energy lost. Excess energy resides in the laser medium as heat. The quantum defect percent is given byq=(1−ωs/ωp)*100,in which ωs is a frequency associated with the laser energy transition and ωp is the pumping light frequency. Thus, a low quantum defect is desirable. In the case of a lasing material pumped by an intense light source, excited state absorption (ESA) reduces pumping efficiency. A factor γ=[1+(δv/Δv)2]−1 is used to measure overlap between emission and absorption lines, in which δv is the frequency difference between the emitting transition and the absorbing transition, and Δv is the full line-width at half intensity of the pumping diode spectrum. A small value of γ corresponds to a low probability of an ESA transition and a high efficiency pumping scheme with respect to ESA.
High-power, diode-pumped solid state (DPSS) pulsed lasers, with power levels on the order of tens of Watts, are preferred for applications such as micromachining, via drilling of integrated circuits, and ultraviolet (UV) conversion. Neodymium:Yttrium Vanadate (Nd:YVO4) and Neodymium:Gadolinium Vanadate Nd:GdVO4 lasers, made with Nd3+-doped Vanadium Oxide (VO4) crystals are good candidates for high power applications because they feature a high energy absorption coefficient over a wide bandwidth of pumping wavelengths. However, vanadate has poor thermo-mechanical properties, compared with other crystal candidates (e.g., Neodymium:Yttrium Aluminum Garnet, or Nd:YAG) in that the material is stiff and fractures easily when thermally stressed. Vanadate fractures under 53 MPa of pressure, while Nd:YAG crystals used in conventional lasers can withstand pressures as high as 138 MPa. Thus, Nd:YAG allows for a correspondingly larger maximum pump power than does vanadate.
In general, power absorbed by a lasing medium decreases exponentially from the point of entry, according to P=Po(1−e−αL), where Po is applied pump power, α is the absorption coefficient, and L is the length of the crystal rod. If pump power is absorbed preferentially along one axis of a crystal lattice, the absorption coefficient in the direction of that axis is larger. The high power pumping produces a high temperature gradient and associated tensile stress, which may cause asymmetric "thermal lensing" effects or crystal fracture, especially serious for asymmetric absorptions. A symmetric absorption coefficient indicates that pump energy is absorbed equally in all directions, which can expend the heat along the gain medium and in turn reduce excessive thermal stress in the crystal. The inherent structure of the Nd:YVO4 crystal unit cell, having a dimension along the optic axis c=6.2 Å that differs from equivalent dimensions perpendicular to the optic axis, a=b=7.1 Å, results in asymmetric absorption.
Thermal lensing relates to a generally undesirable phenomenon in high power solid state lasers in which heat from excess energy absorption raises the material temperature and distorts the index of refraction of the laser crystal. This distortion results in an effective "lens," in which the focal length varies inversely with absorbed pump power. Excessive thermal lensing is detrimental to solid state laser performance because of beam distortion and reduced laser conversion efficiency. Proper control of thermal lensing in the lasing material (e.g., by lowering the quantum defect level) is therefore a critical factor in high power laser engineering.
Complications such as thermal lensing have thus far limited the power output of vanadate DPSS lasers in TEM00 mode to less than 30 W. Limitations caused by thermal lensing and thermal fracture are described in Peng, Xiaoyuan; Xu, Lei; and Asundi, Anand; Power Scaling of Diode-Pumped Nd:YVO4 Lasers, IEEE Journal of Quantum Electronics, Vol. 38, No. 9, 1291-99, September 2002.
Factors influencing inhomogeneous absorption, thermal lensing, and fluorescence lifetimes include doping concentration and physical dimensions of the laser crystal, as well as pumping wavelength and polarization. A typical pumping wavelength used with vanadate crystals is 808 nm, and typical doping concentrations are 0.2% at.-0.5% at., while values below 0.1% at. are difficult to achieve with the degree of control afforded by current manufacturing processes. Typical crystal rod lengths range from 7 mm-15 mm.
Vanadate crystal is an anisotropic material, in which the pump energy absorption, and therefore the laser gain, is polarization-dependent, absorbing some polarized waves more readily than others. A change in the polarization state of the pump laser beam, in response to temperature fluctuations (thermal effects), or random shifts in the polarization direction, may therefore contribute further to inhomogeneous absorption. It may be advantageous to force the pump laser beam to be either polarized in a certain direction or de-polarized to control this effect.
A 40% reduction in thermal lensing effects is reported by Dudley et al., (CLEO 2002 Proceedings) by pumping at 880 nm directly into the upper energy level of the laser transition, rather than at the traditional 808 nm wavelength. This reduction in thermal lensing effects is thought to result from a decrease in the quantum defect level from 24% to 17%, rather than from improved absorption symmetry, because the directional components of the absorption coefficient still differ by a factor of three. However, the absorption bandwidth that a pump delivers at 880 nm is only 2.5 nm compared to commercial products that offer a 4 nm bandwidth.
McDonagh et al., Optics Letters, Vol. 31, No. 22, Nov. 15, 2006 published results for a high-power Nd:YVO4 laser with 0.5% at. Nd3+ doping, pumped at 888 nm. With reference to FIG. 1, lasing wavelengths for Nd:YVO4 normally include 914.5 nm, 1064 nm, and 1342 nm. As published by A. Schlatter, et al., Optics Letters, Vol. 30, No. 1, Jan. 1, 2005, when operating Nd:YVO4 for emission at 914.5 nm, a neodymium ion behaves as a quasi-three-level system. The low laser energy level Z5 is only 433 cm−1 above the ground state, a condition that results in a high lower-state population of 5% at room temperature. Therefore, Schlatter concludes that there is difficulty in achieving Nd:YVO4 lasing at 914.5 nm because a very bright pumping light source is needed to overcome the high threshold caused by a high population in the state of 433 cm−1.
FIGS. 2, 3, 4, and 5 illustrate certain limitations of vanadate crystals. A primary limitation is maximum pump power, which is the amount of pump energy that may be delivered to a crystal before it fractures. FIG. 2 is a plot comparing calculated maximum pump power levels 100 and measured maximum pump power levels 102 for a doped vanadate crystal, 3 mm×3 mm×5 mm, with a pump beam radius of 0.4 mm. Dependence of fracture-limited pump power on crystal properties is well established. In this case, crystal dimensions, pump beam radius, pump wavelength, and laser-active ion doping concentration determine the power operating range of the laser device. FIG. 2 compares calculated results with three experimental data points 104, indicating the pump power at which vanadate crystals actually fractured for various doping concentrations. The calculation used to predict the curve shown in FIG. 2 is a three-dimensional finite element model that simulates thermal effects of pumping a doped crystal by solving Fourier's heat conduction equation. FIG. 2 shows that low doping concentrations are desirable to prevent fracture, with 0.3% at. doping concentration 106 being optimal, allowing a maximum pump power of 37 W. FIG. 3 shows that, for an applied pump power of 30 W, just under the maximum from FIG. 2, the predicted output power 108 achieved by pumping a vanadate laser with a 0.5% doping concentration is optimized at 9 W. Results in FIGS. 2 and 3 were obtained using a diode laser pump at the conventional pumping wavelength of 808 nm.
FIGS. 4 and 5 show spatial distributions of pump power along the length of a 15 mm vanadate crystal rod that serves as a lasing gain medium. Solid curve 110 and dotted curve 112 trace, at various points along the length of the rod (a-cut), respectively, average power absorbed for polarization in the a-axis direction and average power absorbed for polarization in the c-axis of the crystal rod. An ideal crystal rod exhibits symmetric power absorption, in which both the solid and dotted curves are flat lines that coincide along the full length of the rod. The vanadate crystal rod has asymmetric power absorption with, on average, more power absorbed for polarization in the c-axis direction. Furthermore, when pump power is applied to the ends of a lasing gain medium, more power is absorbed close to the ends, while less power reaches the center, a condition referred to as "end-bulging" 120. This applies to both c- and a-axes; however, more extreme end-bulging 122 occurs in the c-direction. A reduction in end-bulging 124 and a reduction in asymmetry 126 both occur when the doping level increases from 0.3% at. (FIG. 5) to 0.5% at. (FIG. 4). The integrated temperature gradient on the cross section of the lasing crystal is greater in the c-axis direction than in the a-axis direction.


A method hydrofluorinates an olefin of the formula: RCX=CYZ to produce a hydrofluoroalkane of formula RCXFCHYZ or RCXHCFYZ, where X, Y, and Z are independently the same or different and are selected from the group consisting of H, F, Cl, Br, and C1-C6 alkyl which is partially or fully substituted with chloro or fluoro or bromo; and R is a C1-C6 alkyl which is unsubstituted or substituted with chloro or fluoro or bromo. The method includes reacting the olefin with HF in the vapor phase, in the presence of SbF5, at a temperature ranging from about −30° C. to about 65° C. and compositions formed by the process.

This disclosure relates to novel methods for preparing fluorinated organic compounds, and more particularly to methods of producing fluorinated hydrocarbons.
Hydrofluorocarbons (HFCs), in particular hydrofluoroalkenes or fluoroolefins, such as tetrafluoropropenes (including 2,3,3,3-tetrafluoro-1-propene (HFO-1234yf or 1234yf)) have been disclosed to be effective refrigerants, fire extinguishants, heat transfer media, propellants, foaming agents, blowing agents, gaseous dielectrics, sterilant carriers, polymerization media, particulate removal fluids, carrier fluids, buffing abrasive agents, displacement drying agents and power cycle working fluids. Unlike chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), both of which potentially damage the Earth's ozone layer, HFCs do not contain chlorine and, thus, pose no threat to the ozone layer.
In addition to ozone depleting concerns, global warming is another environmental concern in many of these applications. Thus, there is a need for compositions that meet both low ozone depletion standards as well as having low global warming potentials. Certain fluoroolefins are believed to meet both goals. Thus, there is a need for manufacturing processes that provide halogenated hydrocarbons and fluoroolefins that contain no chlorine that also have a low global warming potential.
One such HFO is 2,3,3,3-tetrafluoro-1-propene (HFO-1234yf or 1234yf). The preparation of HFO-1234yf starting from CQ2=CCl—CH2Q or CQ3-CCl═CH2 or CQ3-CHCl—CH2Q may include three reaction steps, as follows:
(i) (CQ2=CCl—CH2Q or CQ3-CCl═CH2 or CQ3-CHCl—CH2Q)+HF→2-chloro-3,3,3-trifluoropropene (HCFO-1233xf or 1233xf)+HCl in a vapor phase reactor charged with a solid catalyst;
(ii) 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf)+HF→2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb or 244bb) in a liquid phase reactor charged with a liquid hydrofluorination catalyst; and
(iii) 2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb)→2,3,3,3-tetrafluoropropene (HFO-1234yf) in a vapor phase reactor;
wherein Q is independently selected from F, Cl, Br, and I, provided that at least one Q is not fluorine.
The hydrofluorination of 1233xf to 244bb is usually conducted in the presence of fluorinated SbCl5 at temperatures above 70° C.; otherwise the catalyst will freeze. Under these conditions, the 1233xf is not completely converted to 244bb because of equilibrium limitations, especially at higher temperatures. As a result, significant amounts of 1233xf are present in the product formed. Since the boiling points of 1233xf and 244bb are only about 2° C. apart, separation of these two species is difficult and expensive.
Moreover, the presence of 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) in the reaction starting materials, such as HCFC-244bb feedstock, can lead to dramatically reduced conversion of HCFC-244bb to HFO-1234yf. In addition, the 2-chloro-3,3,3-trifluoropropene copresence in the starting material, when subjected to dehydrochlorination, can lead to the formation of trifluoropropyne and oligomers, which can produce tar. This result is disadvantageous from the standpoint of a reduced yield of the desired product. Therefore, there is a need for a better catalytic reaction to achieve a higher conversion of 1233xf to 244bb to avoid and/or minimize the need for purification.
The present invention fulfills that need.

This patent is subject to a terminal disclaimer.

Method for preparing 1,1,1,2,2-pentafluoropropane


A method is provided of calculating the structure of an inhomogeneous sample in which an electron beam is used to cause excitation of x-rays from the sample under known conditions of beam energy and geometry with respect to the sample. Notably the beam current is unknown. Measured x-ray intensity data for the sample corresponding to one or more sets of beam conditions and beam currents are firstly obtained, together with comparative x-ray intensity data for samples having known structures. A beam current factor for each beam condition is estimated and effective x-ray intensity data for each of the sets of conditions are then calculated using the measured and comparative x-ray intensity data and the beam current factor. The structure of the sample is then calculated for each of the sets of conditions using the effective x-ray intensity data. Predicting x-ray intensity data are produced corresponding to the calculated structure and compared with the effective x-ray intensity data. These steps are repeated using revised beam current factors until the predicted and effective x-ray intensity data achieve a predetermined similarity condition.

One important method of analysing inhomogeneous samples, such as multiple thin layers on a substrate, involves exposing a specimen to a beam of electrons and measuring the emitted x-ray spectrum. Provided the electron beam is sufficiently energetic to penetrate through the layers and reach the substrate, then characteristic x-rays are generated from elements in both the substrate and the various layers and these contribute to the total x-ray spectrum seen by an x-ray detector.
FIG. 1 shows a typical situation where a 10 keV electron beam is incident on a layered sample with three layers of different thickness on a substrate. Many electron trajectories are shown and x-rays may be generated at any point along the electron trajectory as a result of ionisation of atoms. X-rays are emitted in all directions and if an x-ray detector is positioned above the sample, then x-rays emitted towards the detector will provide signals representative of the elements present in the regions excited by the electron beam. In the arrangement of FIG. 1, x-rays will emerge from all three layers and from the substrate. In FIG. 2, the same sample is exposed to a lower energy electron beam. In this case, the electrons only penetrate into the top two layers so there will be no signal from the lowest layer and the substrate. In general, if a series of x-ray spectra are acquired at different incident electron beam energies, typically between 2 keV and 20 keV, then the corresponding spectra will exhibit characteristic x-ray peaks that vary according to the thicknesses and the compositions of the various layers, and indeed the substrate.
Given a particular electron beam energy, the characteristic intensity for a particular element within a multi-layered sample can be expressed as a "k-ratio". A "k-ratio" is the ratio of the x-ray intensity received for a particular element from the structure (counts per second recorded from a characteristic x-ray emission series such as K, L or M) to that obtained from a flat bulk specimen of pure element under the same experimental conditions. As the name suggests, a k-ratio is dimensionless. Taking this ratio avoids having to know the x-ray detector collection efficiency as a function of energy. By measuring a series of k-ratios, it is sometimes possible to deduce the thicknesses and compositions of the various layers in a multi-layer specimen. Whether this is possible or not depends upon the x ray data, the extent to which information is known about the sample and experimental conditions, and the number of unknowns.
If NE elements in total occur in one or more of the layers or in the substrate and there are NL layers with thickness T1, T2 . . . TNL, and layer L contains concentration CLj of element j, and the substrate contains concentration CSj of element j then the predicted k-ratio for element i at incident electron beam energy E0 can be written as Equation 1 below:—ki=fi(E0, T1, T2, . . . TNL, C11, C12, . . . C1NE, C21, C22 . . . C2 NE, . . . CNL 1, CNL 2, . . . CNL NE, CS1, CS2, . . . CS NE)   Equation 1:where fi is a non-linear function of the layer thicknesses and the compositions of the layers and substrate. Several equations of this form cover the measured element intensities at this one beam energy E0.
There may be more than one equation for a particular element if measurements are made on more than one x-ray emission series for this element (e.g. K or L or M emissions). Measurements may also be taken at further values of the beam energy and in general there will be M of these non-linear equations for k-ratios. The function in Equation 1 typically involves integrations and non-linear functions and in general it is not possible to "invert" the set of equations and write down a formula that expresses the thickness or compositions for any one layer in terms of a set of measured k-ratios. Therefore, to determine a set of thicknesses and compositions ("layer variables") from a set of x-ray measurements, it is known to use a modelling approach where the parameters of the model are adjusted to find a set of ki that are a "best-fit" to the measured k-ratios (see for example, Chapter 15 in "Numerical Recipes in C", Second Edition, W.H. Press et al, Cambridge University Press 1999). Thus, a computer program is used to make iterative guesses at the thickness and composition of the layers to find a set that is a close fit with the k-ratios measured from x-ray spectra (see for example, J. L. Pouchou. "X-ray microanalysis of stratified specimens", Analytica Chimica Acta, 283 (1993), 81-97. This procedure has been made available commercially in the software product "Stratagem" by SAMx, France). The computer program will make a test at each iteration to see if the guesses are not changing significantly between iterations, in which case "convergence" is achieved. Unfortunately in some cases, it is impossible to find a best-fit set of thicknesses and compositions because the measured k-ratios do not reveal enough differences in intensity to resolve the source of the individual contributions to x-ray intensity. In this case, the computer program iterations will fail to converge on a unique solution. Such problems can sometimes be resolved by choosing different x-ray emission series, different beam energies or constraining the range of possible solutions by providing information on some of the thicknesses or compositions where this is known beforehand.
Although there are some guidelines for the choice of beam energies and x-ray series (see for example, J. L. Pouchou, "X-ray Microanalysis of Thin Films and Coatings", Microchim. Acta 138, 133-152 (2002)), in general it is difficult to prove that a given type of sample can always be analysed successfully by this technique except by extensive experimentation in the hands of an expert.
A further practical difficulty arises in obtaining measured k-ratios. With a given beam current incident on the multilayered specimen, the x-ray intensity for an elemental line is measured by recording x-ray counts in a known time interval. A pure element standard is then placed under the beam and the x-ray intensity is measured. The ratio of the two intensities is the measured k-ratio. If a pure element standard is not available for the element in question, then a compound standard could be used or a pure standard from a different element. In that case, a correction is required to convert the measured intensity to that which would have been obtained from a pure standard of the element in question. Besides the inconvenience of having to have both specimen and standard accessible on the same specimen stage, a critical requirement is that the beam current and incident electron energy must be identical for the measurements on the specimen and standard. In some specialised instruments, it is possible to obtain a direct measure of incident electron beam current and this can be used in principle to make a correction if a different current is used for specimen and standard measurement provided the beam current measuring equipment is correctly calibrated. However, in general, analysis instruments are not provided with apparatus which is able to accurately measure the beam current since such apparatus is costly and also takes time to stabilize.
For the conventional case of analysis of a homogeneous bulk material, it is well known that analysis is possible without the use of standards or beam current measurements, provided all unknown elements emit lines that can be measured and the total concentration is assumed to be 100%. However, as pointed out previously (J. L. Pouchou. "X-ray microanalysis of stratified specimens", Analytica Chimica Acta, 283 (1993), 81-97): "Contrary to the case of conventional analysis of homogeneous microvolumes, it is not easy in the case of stratified specimens to work with no standard at all, because this would require to know very accurately the beam current and the solid angle of detection." Furthermore, in some electron beam instruments such as cold field emission scanning electron microscopes, beam current fluctuations make comparative measurements difficult (e.g. R. Gauvin, "Quantitative X-Ray Microanalysis of Heterogeneous Materials Using Monte Carlo Simulations", Microchim Acta 155, 75-81 (2006)).
Thus, there are two undesirable problems with the electron-excited x-ray analysis of inhomogeneous materials such as multilayered materials: the difficulty of determining the feasibility of performing me required analysis and the difficulty of measuring k-ratios using the same equivalent beam current. The problem of determining feasibility has been addressed in our previous patent application, the contents of which are incorporated herein by reference in their entirety (WO2007/132243).
One technique for overcoming the beam current difficulty for some specific situations has been described where measurements of film and substrate element line intensities are used to form a ratio which is independent of beam current (Raynald Gauvin, Quantitative X-Ray Microanalysis of Heterogeneous Materials Using Monte Carlo Simulations, Microchim Acta 155, 75-81 (2006)). This ratio can be used in a calibration curve method to determine either the thickness of a single pure element film on dissimilar pure element substrate or the diameter of a pure element sphere on a dissimilar pure element substrate. However, since the ratio involves different element x-ray lines, the detector efficiency does not cancel as it does for a k-ratio and a calibration factor has to be determined for each application.

Method of calculating the structure of an inhomogeneous sample

Oxford Instruments Nonotechnology Tools Unlimited


The present invention relates to a package for a high-frequency device, in which the characteristic impedance can be matched while a gap between the casing and each terminal is maintained wide enough to avoid contact. In the package for a high-frequency device, each metallic terminal is hermetically fixed to a conductive casing and is electrically insulated from the conductive casing by glass. Each metallic terminal extends in parallel with a side wall of the conductive casing while it is separated from the side wall. Each metallic terminal is also flanked by a pair of conductive protruding portions that are formed on a side wall of the conductive casing and extend in the longitudinal direction of each metallic terminal. The conductive protruding portions are formed on either side of each metallic terminal and serve to match the characteristic impedance.

1. Field of the Invention
The present invention generally relates to packages for high-frequency devices, and, more particularly, to a package for a high frequency device that can perform impedance matching around each terminal in a package for a photo detector device such as PIN-PD (PIN photodiode) used for optical communication.
In recent years, as the transmission rates in optical communication have been becoming higher, there has been an increasing demand for packages that perform accurate characteristic impedance matching and accordingly have excellent transfer characteristics and reflection characteristics at high frequency and over a wide area.
Conventionally, a package for a high-frequency device normally uses ceramics as an insulator, because matching the characteristic impedance is relatively easy with ceramics. Since a metal wiring pattern is normally formed on the ceramics by metal plating, the characteristic impedance of signal lines formed by a Au plating film that is much thinner than the insulator can be easily calculated in a so-called parallel-plate-type arrangement.
However, a package using ceramics as an insulator is costly, and, therefore, there has been a demand for inexpensive packages using glass as an insulator. Still, the characteristic impedance needs to be accurately matched in packages using a glass insulator, as in packages using a ceramic insulator.
2. Description of the Related Art
FIG. 1 is a schematic perspective view of a package for a high-frequency device provided with glass insulators. In this figure, a metallic terminal 34 is fixed to a side wall of a metallic casing 31 by a glass piece 35, and extends along the side wall of the metallic casing 31 in a dual-in-line arrangement.
Although only one metallic terminal 34 is shown in this figure, a plurality of pairs of metallic terminals are actually fixed to the metallic casing 31. An optical fiber attachment portion 33 through which optical fibers for inputting and outputting light are attached to the metallic casing 31 is also formed on the front wall of the metallic casing 31. The metallic casing 31 is placed and fixed onto a stem 32 for mounting an optical device and peripheral circuits.
However, the above package having glass insulators is not provided with a mechanism for characteristic impedance matching, resulting in poor transfer characteristics and reflection characteristics at high frequency. More specifically, since each of the terminals that function as signal lines is much thicker than an Au plating film, the characteristic impedance can be calculated in the parallel-plate-type arrangement only if the gap between the casing and each terminal is very narrow, for instance, 0.1 mm. However, it is difficult to narrow the gap between the casing and each terminal to 0.1 mm, and matching the characteristic impedance is accordingly difficult. Furthermore, if the gap between the casing and each terminal is narrowed to 0.1 mm, there will be a strong possibility of short-circuiting due to contact between them.
A general object of the present invention is to provide packages for high-frequency devices, in which the above disadvantages are eliminated.
A more specific object of the present invention is to provide a package for a high-frequency device that performs accurate characteristic impedance matching while maintaining the gap between the casing and each terminal wide enough to avoid contact.
The above objects of the present invention are achieved by a package for a high-frequency device, comprising:
a plurality of metallic terminals that are insulated from a conductive casing by glass and are hermetically fixed to the conductive casing, each of the plurality of metallic terminals extending in parallel with a side wall of the conductive casing and being separated from the side wall; and
conductive protruding portions that are formed on either side of each metallic terminal and extend in the longitudinal direction of each metallic terminal, each pair of conductive protruding portions serving to match characteristic impedance.
With the conductive protruding portions that are formed on either side of each metallic terminal and extend in parallel with each metallic terminal, the gap between the conductive casing and each metallic terminal can be made wider than in a conventional package. For instance, the gap between the conductive casing and each metallic terminal can be as wide as 0.5 mm, and the possibility of contact between the conductive casing and each metallic casing can be reduced. Thus, the characteristic impedance can be accurately matched.
The above and other objects and features of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings.


A process for purifying and preparing highly pure acarbose from acarbose-containing fermentation broth. The acarbose is purified through steps of alcohol precipitation, a strongly acidic cation exchanger chromatography and an immobolized enzyme affinity chromatography. Acarbose is generally applied in treating diabetes.

1. Field of the Invention
The present invention relates to a process for manufacturing a highly pure acarbose, and particularly to a process which uses alcohol for precipitation and separation, and a strong cation exchange chromatography and an immobilized enzyme affinity chromatography for manufacturing a highly pure acarbose to treat diabetes.
2. Description of the Related Art
Acarbose,
O-4,6-Dideoxy-[[[1S-(1α,4α,5α,6α)]-4,5,6,-trihydroxy-3-(hydroxymethyl)-2-c yclohexen-1-yl]amino]-α-D-glucopyranosyl-(1→4)-O-α-D-glucopyranosyl-(1→4)-D-glucose,C25H43NO18,Mw 645.63, is an oligo-derivative. Acarbose inhibits the activity of α-glucosidase at the edge of the small intestine by invertibility for slowly turning complex carbohydrates and disaccharide into glucose, which can be absorbed by humans, to decrease concentration of triglycerol and insulin in blood and blood sugar.
In the early 1970s, acarbose could improve the ratio of meat and fat, so it was used as an additive in feed for animals such as pigs. Recently, researches have found that acarbose controls the blood sugar of NIDDM and decreases the insulin value after eating, for preventing diabetic carbiovascular complications. However, acarbose cannot directly change insulin resistance. Acarbose only has a few aftereffects, such as abdominal distension, borborygums and diarrhea, which go away after a period of treatment, and hardly affect health. The glucobay of the Bayer was first approved in 1995 by FDA. So far, acarbose is primarily manufactured using Actinoplanes sp. or Streptomyces glaucescens.
The DOH of Taiwan adjusts the adjusting blood sugar material to be health food. Further, Easterners eats polysaccharide which differs from the fat eaten by Westerners. Therefore, acarbose not only treats diabetes, but can also be used in diet food.
U.S. Pat. No. 4,062,950 sets forth a recover and purification process for manufacturing acarbose, and discloses that acarbose-containing fermentation broth is discolored by anion resins or activated carbons in the acidic condition, and that acarbose are absorbed by activated carbons in the neutral condition and are eluted by ethyl alcohol solution or acetone solution in the acidic condition. The elute passes through the cation exchange chromatography, and acarbose are finally washed by the acid or base solution. The eluted liquid is counteracted and concentrated in the vacuum, and acarbose with 85% purity is precipitated by the organic solvent. The high purity of the acarbose can be manufactured if the exchange chromatography uses celluloses as a matrix. Further, the liquid is concentrated and precipitated by the organic solvent to get a highly pure acarbose. The process is complicated because the process must use activated carbons for absorbing and the exchange chromatography process repeated many times for purification of acarbose.
U.S. Pat. No. 4,174,439 mixes cation and anion exchange resin into acarbose-containing fermentation broth to absorb acarbose and elutes the acarbose by deionized water. The carbose solution is processed twice by a cation and anion exchange resin and is eluted by hydrochloric acid, and is processed with a neutralizing treatment by an anion exchange resin and frozen until dry to acarbose with 52-58% purity.
Further, U.S. Pat. No. 4,666,776 and U.S. Pat. No. 4,767,850 improve U.S. Pat. No. 4,174,439 to use strong cation exchange resin, be washed by hydrochloric acid, be processed by a neutralizing treatment with an anion exchange resin and frozen until dry to get acarbose with 79-82% purity.
The above methods of purifying the acarbose all repeat the anion and cation exchange chromatography to get the acarbose solution and finally use cation exchange chromatography to get a high concentration of acarbose. However, it is difficult to achieve a purity of acarbose sufficient for use as a medical drug.
U.S. Pat. No. 4,904,769 discloses a method in which impure acarbose passes through a weak cation exchange chromatography containing carbonyl, cellulose, and dextran with specific temperature and pH values to get acarbose with a 90% purity. The process is complicated and uses a weak ion exchange chromatography in an expansive process, resulting in high manufacturing costs.
Finally, WO 99/07720 discloses taking an impure acarbose manufactured by U.S. Pat. No. 4,174,439, U.S. Pat. No. 4,666,776 and U.S. Pat. No. 4,767,850, which passes through a strong cation exchange chromatography containing non-aromatic to get highly pure acarbose, and the processes are typically complicated with high manufacturing costs.

Purification process for manufacturing a high pure acarbose


There is provided a semiconductor device. The semiconductor device includes a lower electrode, a contact connected to the lower electrode to have a double trench structure, a phase change material layer accommodated in the double trench to cause a phase change between a crystalline state and an amorphous state in accordance with a change in heat transmitted by the contact, and an upper electrode connected to the phase change material layer.

1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing the same.
2. Description of the Related Art
A phase change memory is a memory that uses a difference in resistance between materials in accordance with a phase change and is one of next generation memory semiconductors that has the advantage of a flash memory in which stored information is not erased although power is not supplied and the advantage of a dynamic random access memory (DRAM) in which stored data is erased when power is not supplied, however, processing speed is high.
The phase change memory has an access time at least 1,000 times faster than that of the flash memory that is a representative non-volatile memory and can operate at a low voltage of no more than 2 to 5 V like the DRAM.
Also, it is possible to read and write data fast in the phase change memory like in a static random access memory (SRAM). Since the phase change memory has a relatively simple cell structure, it is possible to reduce the size of a device to the size of a DRAM device.
Also, since not a memory device using storage of charges but a difference in resistance between materials in accordance with a phase change is used, it is possible to write down and erase information no less than 1010 times without being affected by cosmic radiation or electromagnetic wave.
FIG. 1 is a sectional view illustrating the structure of a conventional phase change memory.
As illustrated in FIG. 1, a phase change memory 10 includes a lower electrode 12, a contact 14, a phase change material layer 16, and an upper electrode 18.
The temperature of the phase change material layer 16 is changed by the amount of current that flows in the contact 14. In accordance with the change in temperature, the alignment of the atoms or molecules of the phase change material layer 16 is changed into an amorphous state having no regularity or a crystalline state having regularity to obtain 1 and 0 through the lower electrode 12 and the upper electrode 18. The signal is 0 when the alignment is in the crystalline state and is 1 when the alignment is in the amorphous state. Information is processed while repeating the states.
As illustrated in FIG. 1, in the conventional phase change memory 10, since the contact 14 is connected to the phase change material layer 16 only through the top surface thereof, the heat generated by the contact resistance of the contact 14 is transmitted to the phase change material layer 16 based on the top surface of the contact 14 in the radiation direction (the arrow of FIG. 1).
Therefore, a program region 15 that functions as a memory is limited to a partial region as illustrated in FIG. 1, the amount of generation of heat is determined by the area of the top of the contact, the distribution of heat is not uniform all over the phase change material layer 16, and heat transmission time is long.
When heat distribution is not uniform and it takes a long time to transmit heat like the conventional phase change memory 10, a switching time for which the phase change material layer 16 changes from an amorphous state to a crystalline state or from the crystalline state to the amorphous state increases so that the operation speed of a memory becomes low.


A wireless speaker unit includes a radio transceiver oscillator which provides timing signals to a pulse width modulator and to a sample rate controller that provides a variable oversampling signal to a delta sigma modulator. The variable oversampling signal determined by a sampling rate of the digital audio signal.

The present invention relates to high quality audio and, more particularly, a wireless speaker system for reproducing high quality multichannel audio.
A home theater system typically comprises one or more signal sources, such as a digital versatile disc (DVD) player, a BLU-ray™ disc (BD) player or broadcast receiver; a display unit; an audio video control receiver (AVR); and multiple speaker units. An audio processor which may be integrated in the AVR or located elsewhere in the system converts analog or digital signals received from the signal source to an appropriate form for transmission to the speaker units. A home theater system may employ wired connections between the audio processor and the speaker units in which analog signals, which may be converted by an audio processor from digital data received from the signal source, are commonly amplified by the AVR and transmitted to the speaker units. However, it can be difficult or impractical to route wires to remote speakers once a room has been finished and the wires can be unsightly and subject to damage when exposed along a wall or routed under a carpet. For this reason, home theater systems often utilize wireless signal paths between the AVR and the speaker units. Digital data, including converted analog signals from a signal source, are packetized and multiplexed into a transport data stream by the audio processor of the AVR. An AVR transceiver modulates a carrier with the transport data stream and transmits the modulated carrier to a transceiver located in each wireless speaker unit making up the system. In the speaker unit, the digital audio data is separated from the carrier and converted to an analog signal or a succession of pulses which are amplified and transmitted to the speaker.
Surround sound, a technique for enhancing the perception of the spatial origin of sound by adding audio channels which are selectively output by speakers that, at least partially, encircle the listener is a common feature of home theater systems. Six channel surround sound audio; exemplified by Dolby Digital®, Dolby Pro Logic II™, DTS™, and SDDS™ surround sound audio; is the standard surround sound audio component of digital broadcast and music and the most common surround sound system for both commercial and home theaters. Six channel surround sound audio systems, known as 5.1 ("five point one") surround sound systems, utilize five full bandwidth channels; a front left channel, a front right channel, a center channel, and, respective, left and right surround channels; each reproduced by a corresponding speaker. In addition, the 5.1 surround sound system includes one low-frequency effects channel, the point one (0.1) channel, which is reproduced by a subwoofer. Increasingly, manufacturers of home theater systems are adapting an eight channel (7.1) surround audio system with a standard front or center speaker, a subwoofer and four surround speakers. Whereas a 5.1 surround sound system combines both surround and rear channel audio into two channels, a 7.1 surround system splits the surround and rear channel audio into four distinct signals with sound effects directed to left and right channels through speakers to the sides of the listener plus two rear surround channels to the listener's left-rear and right-rear. High end home theater systems, such as 11.1 surround sound systems, with even greater numbers of speakers are contemplated. While wireless digital communication between the AVR and the speakers eliminates problems relating to routing wires, it typically increases the cost of the system because each remote speaker unit must have its own power supply, transceiver to receive the radio frequency signal from the AVR; digital-to-analog converter (DAC) to accurately convert the digital audio signals transmitted by the AVR to an analog signal or a high frequency sequence of pulses and, to provide a signal to drive the speaker, an amplifier to amplify the analog signal or pulses.
What is desired therefore, is an economical wireless speaker unit which produces high quality audio.


Disclosed herein is an illuminating apparatus for rendering lighted images of different shapes in different directions. The illuminating apparatus comprises a lamp fixture, a perforated dish affixed to the lamp pipe, a lamp shade affixed over the perforated dish, and a dome cover affixed on top of the lamp shade. The lamp fixture comprises a light bulb socket, a lamp pipe, and a lamp base. A light bulb is affixed to the light bulb socket and enclosed within the lamp shade. The dome cover comprises multiple inscriptions. The lamp shade comprises a layered mesh. The layered mesh may comprise wires crossing at right angles. On lighting the light bulb, the light passes through the perforations of the perforated dish, the inscriptions of the dome cover, and between the wires of the layered mesh, thereby rendering the lighted images of the different shapes in different directions.

This invention, in general, relates to the field of illuminating apparatuses. More specifically, this invention relates to an illuminating apparatus for providing lighted images of different shapes in different directions.
Illuminating apparatuses are used for lighting indoor and outdoor spaces. Most illuminating apparatuses provide light without shapes or images. It is desirable to have an illuminating device that renders images and shapes, for example the shape of a cross. The cross is a religious symbol of Christianity. The cross is generally seen as a representation of the crucifixion of Jesus. Along with having religious significance, the cross also holds aesthetic value. Hence it is desirable to have an apparatus that renders light in the shape of the cross. Moreover, illuminating apparatuses typically provide illuminated images of fixed unalterable shapes. Other apparatuses that provide light in patterns may only be viewed from a specific side or from particular range of angles.
Hence, there is a need for an illuminating apparatus that renders multiple lighted images of different shapes which are visible in different directions.


The EVADE (Externally Vented Aerosol and Droplet Evacuation) system is designed to treat collected aerosols with ultraviolet radiation and exposure to ozone gas to prevent the spread of COVID or other infectious pathogens. The system uses an externally vented central vacuum system which produces up to 280 CFM of vacuum flow to facilitate collection of potentially contaminated oral aerosols and droplets generated by instrumentation of any type within the medical, dental or any other field which generates said aerosols. The aerosols are collected within a mirrored chamber, reflecting UVC light in all directions and exposing the aerosols to ozone before moving through HEPA particle filtration and out of the environment through the exhaust of a central vacuum system.

Many infectious diseases including COVID-19 have a significant potential for spread through orally generated aerosols. This invention is within CPC A61L employing UVC, ozone and HEPA filtration and external discharge of potentially contaminated oral aerosols and droplets generated during patient contact in medical, dental or any such settings which may generate such aerosols. The disclosure relates generally to the handling of potentially infectious oral aerosols, and more particularly, to an improved solution for collection and treating of human aerosols by collection and treatment using ultraviolet radiation, exposure to ozone and removal of said materials from the immediate environment.
Devices exist which use Ultraviolet (UV) and ozone (O3) for air purification and sterilization and are known to have a successful history. Ultraviolet radiation with a wavelength near the absorption peaks of molecules of DNA and proteins of pathogens is effective in their destruction. Ozone is bio destructive, causing bacteria, viruses, fungi and other pathogens to undergo cellular degradation and destruction. Many existing systems additionally rely on HEPA filtration to treat the air which is then recirculated into the environment from which it is collected. Even though UVC and HEPA filtration without ozone is highly effective, re-introducing aerosols treated in this fashion into the occupied environment carries risks if filtration fails or the UVC bulb loses effectiveness or fails. These systems do not include ozone due to the toxic effects which the introduction of ozone into an occupied environment would have upon the respiratory system of humans. The addition of ozone provides a higher rate of destruction of pathogens and external venting of the treated aerosols eliminates the potential for spread of the collected pathogens.
Dental procedures which involve a dental handpiece, ultrasonic scaler and/or 3 way air/water spray syringes generate aerosols and droplets which may contain saliva and other patient fluids. If dispersed in the treatment room, these potentially infectious aerosols and droplets create a hazard to the dental professionals and other patients within the office environment if inhaled or transferred through surface contact within the treatment area.
Other existing solutions which collect and treat generated aerosols produce distracting noise pollution. Airflow can also be a limiting factor in the effectiveness of other systems in collecting the generated aerosols. Other solutions also occupy valuable floor space within the treatment room, and reintroduce the collected air into the treatment room through heated exhaust. Floor space is at a premium in most medical/dental treatment rooms. Making room for an additional piece of equipment can be difficult. Most patients and dental staff also prefer to avoid introducing more ambient noise into the treatment area. The exhaust air from other systems can increase the ambient temperature of the treatment room. If a part of the filtration system fails, such as the UVC bulb, or the filters become clogged, air flow is reduced or contaminants are reintroduced into the treatment environment.

EVADE system (Externally Vented Aerosol and Droplet Evacuation System)


A molded plastic fence having a unitary front fence section and a unitary rear fence section is provided. The unitary front fence section and the unitary rear fence section are coupled together to form a fence without visible molding artifacts. To emulate a traditional wooden fence, the fence sections preferably include various fence elements such as posts, slats and rails. The fence elements on each fence section typically have a planar member with an inner side and a raised edge extending from the inner side. The molding artifacts are disposed on the inner sides of the fence elements. The unitary front fence section and a unitary rear fence section are coupled with the raised edges engaging each other. In this configuration the molding artifacts are hidden from view and the fence elements appear as solid.

1. Field of the Invention
This invention relates to molded plastic fences and, more specifically, to a molded plastic fence having both a front section and a rear section each having an inner side, wherein all molding artifacts, e.g. ribs, ejection pin marks, etc., are disposed on the front and rear fence section inner sides, and wherein the front and rear fence sections are joined together and enclose the inner sides whereby a visually sealed fence section is created.
2. Background Information
Plastic fences are used in many locations for decorative fences. Such decorative fences were originally assembled from wood. Wooden fences had the advantage of being generally uniform on both the front and back sides and were, therefore, visually pleasing. Wooden fences, however, were also expensive, heavy, and subject to degrading when exposed to weather. Plastic fences could be molded, generally, into the shape of wooden fences and were inexpensive, light, and weather resistant. Plastic fences, however, included molding artifacts, e.g. ribs, ejection pin marks, etc., which were visually unattractive.
Such molding artifacts were generally placed on the "back" side of the plastic fence in an attempt to keep the molding artifacts hidden from view. While molding artifacts on the rear side of a fence could not be seen from the front, such molding artifacts were still clearly visible when an observer moved to the side of the fence. In an attempt to further hide the molding artifacts, fence elements, e.g. posts, slats and rails, were molded as deep C-shaped channels wherein the molding artifacts were disposed at the bottom of the channel. This shape helped hide the molding artifacts from observers standing to the side of such fences. However, observers behind such deep channel fences, e.g. a person in a yard looking at such fences lining a sidewalk, could still see the molding artifacts in the deep channels. Further, the fact that the fence elements can be observed as not being solid further detracts from the fence's attractiveness.


Plasma processor including: reaction chamber having a base for placing a wafer; a source radio-frequency power supply outputting high frequency radio-frequency power into the reaction chamber to ignite and maintain plasma; a first bias radio-frequency power supply and a second bias radio-frequency power supply, the first bias radio-frequency power supply outputting a first radio-frequency signal with first frequency, the second bias radio-frequency power supply outputting a second radio-frequency signal with second frequency higher than the first frequency, the first radio-frequency signal and the second radio-frequency signal being superimposed to form a periodical first compound signal that is applied to the base; and a controller configured for tuning at least one of amplitude, frequency, average voltage or phase of the first radio-frequency signal and of the second radio-frequency signal, such that the first compound signal experiences three consecutive stages in each cycle: falling stage, flat stage, and rising stage.

Vacuum processing apparatuses are widely applied in the semiconductor industry, among which plasma processing apparatuses and chemical vapor deposition apparatuses are dominant ones. The plasma processing apparatus generates plasma by radio-frequency coupled discharge, and then performs processing such as deposition and etching with the plasma.
In a plasma etching process, two radio-frequency power supplies are generally used: a source radio-frequency power supply and a bias radio-frequency power supply. The source radio-frequency power supply outputs a high frequency radio-frequency power (e.g., 60 MHz) to excite gas to generate plasma, mainly used for controlling concentration of the plasma. The bias radio-frequency power supply outputs a low frequency radio-frequency power (e.g., 2 MHz or 13 MHz), mainly used for controlling ion energy in the plasma to bombard a substrate. Plasma concentration and ion bombardment energy have a significant impact on etching rates. Therefore, a method for improving plasma concentration and ion bombardment energy has been always pursued in the industry. The importance of such a method is prominent in high aspect ratio (HAR) etching applications. Plasma concentration is mainly controlled by the source radio-frequency power supply, such that the plasma concentration is usually improved by increasing power of the source radio-frequency power supply. Enhancement of the ion energy in the plasma to bombard the substrate is mainly implemented by increasing the sheath voltage on the substrate surface, which can be achieved by two ways: 1) increasing power of the bias radio-frequency power supply to improve sheath voltage on the substrate surface. The ions in the plasma are accelerated in the sheath(s) to bombard the substrate; the larger the sheath voltage is, the greater the ion bombardment energy is. However, increasing power of the bias radio-frequency power supply will have some negative impacts, for example, the heat dissipation system of the chamber will become more complex, and the service life of chamber parts will be shortened due to stronger bombardment. 2) increasing the ratio of sizes of the upper and lower electrodes of the chamber. The sheath voltage on the substrate is associated with the sizes of the upper and lower electrodes (i.e., a showerhead and an electrostatic chuck) in the plasma processing chamber. The larger the ratio of the sizes of the upper and lower electrodes is, the greater the value of the sheath voltage is. However, change of the sizes of upper and lower electrodes is constrained by the volume of the chamber; particularly when the volume of the chamber is fixed, it is hard to freely change the sizes of the upper and lower electrodes. Therefore, this approach has a relatively poor flexibility.
Accordingly, the industry still lacks a novel method of boosting ion energy in plasma to bombard a substrate. Such a method is beneficial to a high aspect ratio etching process.

ADVANCED MICRO-FABRICATION EQUIPMENT INC. CHINA


A polygon rendering circuit for a computer color graphics system comprising an edge stepper which steps along edges of an input polygon to determine the span of the polygon along each scan line intersected by the polygon. The coordinate values of the edges on each scan line are determined to sub-pixel resolution such that only those pixels whose centers lie within the true polygon edges (within the span width) must be drawn. Processing efficiency is improved and bandwidth is minimized by passing only those edges of the polygon which are new to that polygon and by computing the Z values in the same manner as, and in parallel with, the X values. Improved results are also possible in accordance with the technique of the invention, for since adjacent polygons compute the same edge by stepping, there can be no gaps between polygons due to round-off errors.

1. Field of the Invention
The present invention relates to polygon rendering circuitry of a computer graphics system, and more particularly, to a circuit for determining, to sub-pixel resolution, the coordinates of points along respective edges of a polygon on each scan line covered by the polygon and for filling in the display pixels within the polygon for display.
2. Description of the Prior Art
Prior art raster graphics systems generally contain two distinct parts: a graphics transformation engine that transforms and lights the geometric description of a scene in accordance with the user's viewpoint and a renderer that paints the transformed scene onto a display screen. As is well known, the geometric description of the scene may comprise a combination of a plurality of polygons having an arbitrary number of sides. In other words, the 3-dimensional image to be displayed has been described as a surface composed of polygons of differing shadings. As used herein such a "polygon" refers to an ordered set of vertices V[1] . . . V[N] where N is the vertex count for the polygon. These vertices specify the N edges of the polygon, which are line segments E[1] . . . E[N] with end points made up of respective vertices V[1] . . . V[N]. For example, line segment E[1] may have end points V[1] and V[2], while line segment E[2] has end points V[2] and V[3]. Such polygons may be identified by the graphics transformation engine as a sequence of graphics primitives including information such as the coordinates (X,Y,Z) of the vertices of each polygon as well as the shading information for each of the vertices and instructions which are processed in the graphics transformation engine for all pixel-level rendering computations.
Such geometric representations of a scene greatly facilitate the processing by a graphics transformation engine which is necessary for rendering the pixel image data to the display screen. The graphics transformation engines typically perform many tasks on such data including graphics context management, matrix transformation calculations, spline tessellation and lighting model computations. The transformation engines may also control vector and polygon rendering hardware. However, such computations are generally quite complex and time-consuming and require much processing power. The resulting processing difficulties significantly limit the speed by which images may be rendered in conventional raster graphics systems.
Despite such problems, workstation users are demanding ever-increasing performance and image quality from graphics workstations. This demand produces a corresponding appetite for computing power. One of the most compute-intensive functions of a graphics workstation, besides processing by the graphics transformation engine, is the process of scan conversion, where vector and polygon end points are transformed into pixels on a raster scan display and the pixels appropriately shaded. During the 1980's, a number of 3-D workstations were introduced with hardware scan converters that performed smooth color shading, but all such workstations provided fairly low performance and/or limited feature sets. As a result, designers of such systems often compromised by approximating the correct colors for each pixel by linearly interpolating the colors across each polygon face without correctly accounting for the effect of perspective and by using a simplified polygon sampling method. However, such compromises have been found to cause problems when used in conjunction with advanced features of the type desired for modern day graphics workstations.
Graphics workstations of the 1990's require scan converters which make no such compromises. The increasing complexity of user images requires scan converters capable of generating color, Z (depth), and texture map parameter values in perspective for each pixel in every vector and polygon at a sustained 50M pixels/second (or greater) rate, with peak rates approaching at least 100M pixels/second. Until recently, this level of performance was out of reach due to the complexity of the perspective interpolation algorithms. Indeed, the complexity of perspective-corrected interpolation and texture mapping precluded their hardware implementation, and typically, the correct shading was approximated by implementing linear interpolation of color and Z. However, due to advances in graphics workstation hardware, perspective interpolation and texture mapping are now possible without sacrificing the 100M pixels/second peak rate. For example, a high speed perspective interpolation system is described in U.S. patent application Ser. No. 07/493,189, which was incorporated above by reference, while a high speed texture mapping system is described in U.S. patent application Ser. No. 07/494,706, filed Mar. 16, 1990 and entitled "Method and Apparatus for Generating Textured Graphics Primitives in Frame Buffer Computer Graphics Systems."
Different techniques exist for determining which pixels inside a polygon will be rendered to the display screen by the rendering circuitry. For example, the incrementing fractions interpolation technique permits calculation of the x axis value along the scan line without solving the X=M*Y+C (which requires a multiplication) for each value of Y in the direction perpendicular to the scan line. This is accomplished by computing the line differential, slope M, as a constant equal to (X.sub.end -X.sub.s)/(Y.sub.end -Y.sub.s). Once M has been computed, successive X,Y points can be generated by repeatedly incrementing Y by 1 and adding M to X. All X values are rounded to the nearest integer by adding 0.5 to the initial X value and truncating each X result. However, such a division is generally slow and is prone to round-off errors. Moreover, the fractional part of M and X must have a precision at least equal to the screen precision to be guaranteed of hitting the correct end point. These problems were earlier solved by the present inventor by extending the Bresenham algorithm to polygon rendering.
In particular, the present inventor described in an article entitled "A Fast Shaded-Polygon Renderer", Proceedings of SIGGRAPH '86, Computer Graphics, Vol. 20, No. 4 (August 1986), pp. 95-101, a one-chip VLSI implementation of a shaded-polygon renderer. The polygon renderer described therein takes advantage of an extension to Bresenham's vector drawing algorithm to interpolate four axes (for red, green, blue and Z) across a polygon in addition to the X and Y values. Such a method has provided rendering speeds suitable for interactive manipulation of solids.
As noted above, for most methods of image synthesis, the image is generated by breaking the surfaces of the object into polygons. The color and intensity at each vertex may then be calculated and the results drawn into a frame buffer while interpolating the colors across the polygon. This is known as Gouraud shading. The color information can be calculated from light source data or computed with thermal or stress analysis. The interpolation of coordinate and color (or intensity) across each polygon, on the other hand, is accomplished by interpolating the coordinate and color of each quantized point (pixel) on the edges of the polygon and subsequently interpolating from edge to edge to generate the fill lines. If hidden surface removal with a Z buffer is required, then the depth (Z) value for each pixel must also be calculated. Also, since color components can vary independently across a surface or set of surfaces, red, green, and blue intensities must be interpolated independently. Thus, for a general purpose graphics system, a minimum of 6 different parameters (X, Y, Z, Red, Green, and Blue) must be independently calculated when drawing polygons with Gouraud shading and interpolated Z values. In the aforementioned article, the present inventor teaches extending the line-drawing algorithm proposed by Bresenham to six axes so that the values of X, Y, Z, Red, Green, and Blue may be determined for polygon rendering.
The polygon renderer of that system begins the polygon fill process by reading an instruction and a pointer out of an external dual-ported RAM. The instruction indicates what kind of figure (polygon or vector) is to be drawn and if a line type pattern is to be used. The pointer indicates the location of the first edge data packet for the polygon, and each packet contains a pointer to the next packet. The first pointer is passed to an EDGE functional block. The EDGE block builds up an ordered list of active edges (in the order to be used) and then reads the data packets of the first two edges to be drawn. As they are read, they are passed to a SETUP block and then on to the interpolator. When the interpolator finishes one scan line of each edge, the packets are passed back to the EDGE block. The EDGE block dynamically maintains an active edge list, adding edges as the current scan line reaches them and deleting edges as they are completed. The EDGE block also re-sorts the order of the active edge list whenever two edges cross. This permits the drawing of non-planar, concave, twisted polygons which may contain holes.
As the interpolator steps along each edge in such a polygon rendering system, the output is sampled by a FILL block. The FILL block saves the starting and ending points of each edge's contribution to the scan line. From these values, it generates fill vectors which are passed on to a SETUP block. The FILL block also keeps track of whether or not each edge is just starting or ending so as to properly handle vertices. This polygon fill process will now be described with respect to FIG. 1.
FIG. 1 illustrates a polygon to be rendered and the first four lines of pixels drawn. The pixels in the edge are represented with circles and the pixels making up the fill lines are shown as squares. In this example, once the setup for Edge 1 is complete, its packet of data is sent to the interpolator and the first row of pixels in the edge is drawn. Then the packet is sent to the EDGE block which compares its X and Y values to verify that the third edge does not yet have to be activated. After Edge 2 is set up, its first pixel is drawn and its packet is sent on to the EDGE block. Then, the next horizontal row of pixels in Edge 1 is drawn, followed by the next pixel in Edge 2. As shown, for the second and each subsequent fill line, Edge 1 has several pixels drawn per line, while Edge 2 has only one. The fill line (Fill 1) is then drawn between the inside pixels of each edge. While Fill 1 is being set up, the two edges are again incremented in the Y direction and the next row of pixels in the edges is drawn. The process is repeated for each scan line in the polygon.
Excellent results have been achieved with the abovementioned polygon rendering system. However, since multiple steps sometimes must be used for generating the edge at each scan line, the edge forming process has been found to take a substantial portion of the polygon fill time. Moreover, since the extended Bresenham algorithm renders polygon edges by drawing pixels which lie closest to the true edges, adjacent polygons may overlap or underlap, whereby pixels from backfacing polygons can be seen through gaps between adjacent polygons due to round-off errors. It is desired to minimize this processing time for the edges. It is also desired to precisely identify the edge for each scan line using a very precise point sampling algorithm such that there need only be one pixel for each edge and all pixels therebetween are fill pixels which may be readily interpolated in an efficient manner by the interpolator. In other words, an improved technique for identifying the edges of polygons is desired so that only pixels actually within the polygon edges will be drawn, problems with overlap and underlap will be avoided, and less processing time will be necessary for forming the edges during the polygon rendering process.
Akeley et al. describe in an article entitled "High-Performance Polygon Rendering", Computer Graphics, Vol. 22, No. 4, August 1988, a polygon rendering system architecture for real-time display of shaded polygons. Akeley et al. compute the Y coordinates of the polygon edges to 1/8 pixel tolerance and then correct all depth and color component iterations to the nearest pixel center, which are then iterated in full-pixel steps. Akeley et al. use an Edge Processor to iterate along the top and bottom edges of the trapezoid so as to generate at each iteration the top and bottom coordinates of a single span. Color and depth values are computed using changes in Y to 1/8 pixel accuracy. The slope is then used to iterate to the nearest pixel center. Accordingly, the final span definition comprises the corrected initial color and depth values, the color and depth slopes, the integer X and Y value of the bottom pixel, and the span length.
FIG. 2 shows a polygon ABCD which is rendered in accordance with the technique of Akeley et al. As shown, the polygon ABCD is broken into trapezoids, and the interstitial points X' and X" are determined. The polygon is then filled by using the slope of the edges to iterate with to the nearest pixel center from the edge intersection with the next line. Thus as with the extended Bresenham algorithm, the nearest pixel center is identified as part of the polygon, irrespective of whether that pixel is inside or outside of the polygon being drawn.
The system of Akeley et al. also provides very fast polygon fill rates. However, the system of Akeley et al. requires the determination of the interstitial points X' and X" and only allows the points along the edges to be determined to 1/8 pixel accuracy. Moreover, the polygon is filled by determining the nearest pixel center to each edge and then filling all points in between. As noted above, this approach can result in undesirable polygon overlap and/or a "peek-through" effect wherein gaps are left around the edges of the polygon. Thus, although Akeley, et al. can quickly calculate the edges, their system still has the overlap and underlap problems referred to above.
Accordingly, an improved polygon rendering technique is desired wherein processing speed and accuracy may be enhanced while polygon overlap and undesired "peek-through" effects may be eliminated. The present invention has been designed for this purpose.

Polygon renderer which determines the coordinates of polygon edges to sub-pixel resolution in the X,Y and Z coordinates directions