A magnetic field adjustment device for a superconducting magnet, wherein magnetic material shim mechanisms are arranged in an axial direction of an inside periphery of the cylindrical superconducting magnet, each of the magnetic material shim mechanisms including a combined shim tray (14 in FIG. 2) in which a plurality of divided shim trays (11 and 12) and shim tray spacers (13) inserted between the divided shim trays are rectilinearly coupled, and magnetic material shims (101) for magnetic field adjustments as are accommodated in the divided shim trays. The magnetic material shim mechanisms afford a high versatility of magnetic material shim arrangements, whereby a correctable range of a magnetic field uniformity can be widened.

1. Field of the Invention
This invention relates to a magnetic field adjustment device and a magnetic field adjustment method for a superconducting magnet as are chiefly employed for a magnetic resonance imaging equipment (hereinbelow, abbreviated to "MRI equipment").
2. Description of the Related Art
In an MRI equipment, a static magnetic field which has a high magnetic field strength and which is of high spatial uniformity and high temporal stability is needed, and hence, a superconducting magnet is often employed.
It is required of the superconducting magnet for the MRI equipment to generate a magnetic field region which exhibits a very high uniformity of, for example, within 3 ppm, near a magnetic field center. Therefore, the superconducting magnet is designed at a high precision. In actuality, however, a magnetic field uniformity in an actual diagnostic space worsens due to a manufacturing dimensional error in a process for producing the magnet, the influence of a magnetic material existing around a place where the magnet is installed, and so forth.
Therefore, the superconducting magnet includes means for making the fine adjustment (hereinbelow, termed "shimming") of a magnetic field. There is a passive shimming method in which magnetic material shims made of a magnetic material of high permeability are used as one means for performing the shimming. This method is such that the magnetic material shims in an appropriate quantity are arranged at an appropriate position, within the generated magnetic field of the superconducting magnet, and that the disorder of the highly uniform magnetic field of the superconducting magnet is corrected by utilizing a magnetic field generated by the magnetization of the magnetic material shims. (Refer to Patent Document 1 being JP-A-1-245154, and Patent Document 2 being JP-A-63-122441.)
The shimming based on a prior-art passive shimming method will be described with reference to FIGS. 13 and 14. FIG. 13 is a cut-away perspective view of a superconducting magnet for an MRI equipment as includes a prior-art magnetic field adjustment device. Referring to FIG. 13, numeral 21 designates the superconducting magnet which has a substantially cylindrical shape. Inside the superconducting magnet 21, a plurality of superconducting coils 22 are disposed substantially concentrically with the cylinder of the superconducting magnet 21, and they generate a static magnetic field in a uniform magnetic field space 23 to which a highly uniform magnetic field is to be outputted. The superconducting coils 22 are coils each of which is fabricated by winding a superconducting wire, and they are accommodated in a low-temperature container 24, together with liquid helium (not shown) which is a coolant required for holding these superconducting coils 22 in a superconducting state. The low-temperature container 24 is configured of a helium tank 25 in which the liquid helium and the superconducting coils are accommodated, a thermal shield 26 which serves to intercept thermal invasion from outside, and a vacuum tank 27 which holds the interior of this low-temperature container 24 in a vacuum state. Usually, a refrigerator (not shown) is connected to the low-temperature container 24 in order to suppress the consumption of the liquid helium.
Numeral 98 designates a magnetic material shim mechanism, which is fixed to the inside cylinder of the superconducting magnet 21. The magnetic material shim mechanism 98 is a mechanism for accommodating magnetic material shims therein so as to arrange them at the periphery of the uniform magnetic field space 23.
FIG. 14 shows the magnetic material shim mechanism 98. The magnetic material shim mechanism 98 is configured of the plurality of magnetic material shims 101, a shim tray 102 which accommodates the magnetic material shims 101 therein and which is fixed to the inside cylinder of the superconducting magnet 21, and shim spacers 103 and lids 104 which fix the magnetic material shims 101 within shim pockets. The shim tray 102 is formed of a nonmagnetic material, and it has a shim pocket structure for arranging the magnetic material shims 101 therein.
The magnetic material shims 101 are thin plates made of a magnetic material, for example, iron, and they have predetermined vertical and lateral dimensions so as to be accommodated in shim pockets. As the magnetic material shims 101, a plurality of sorts having different thicknesses are prepared. The quantity of the magnetic material which is arranged in each shim pocket is determined by the thicknesses and number of the magnetic material shims 101.
The shim tray 102 is formed with slits so that the lids 104 of snug fit type can be fixed. After the accommodation of the magnetic material shim 101 in the shim pocket, the shim spacers 103 made of a nonmagnetic material are packed into the shim pocket, and the lid 104 made of a nonmagnetic material is put on the shim pocket, whereby the magnetic material shims 101 are fixed within the shim pocket. The shim tray 102 has a mechanism for being fixed to the inside cylinder of the superconducting magnet 21, and it is fixed to the inside cylinder of the superconducting magnet 21 after the accommodation of the magnetic material shims 101. In this way, the magnetic material shims 101 are arranged on the magnet inside cylinder so as to correct the disorder of the magnetic field uniformity. The magnetic material shim mechanisms sometimes form part of the structure of inclined magnetic field coils in the MRI equipment.
The shimming which uses the magnetic material shim mechanisms is carried out by the following steps:
Initially, the superconducting magnet 21 is excited in a state where the magnetic material shims 101 are not mounted, and the magnetic fields of the uniform magnetic field space 23 are measured at a large number of points, so as to evaluate the uniformity of the magnetic field which the superconducting magnet 21 generates. In general, magnetic field strengths in a uniform magnetic field region are expressed as Formula (1) by employing a Legendre function expansion, and they are nominated by components based on (m, n) values. A (0, 0) component is a necessary uniform magnetic field component, and all the others are error magnetic field components which are nonuniform within the imaging region.
Subsequently, the arrangement of the magnetic material is designed in order to correct the nonuniformity of the magnetic field. The design is performed by a computation which optimizes the quantities of the magnetic material as is to be arranged in the respective shim pockets, so as to lessen the error magnetic field components to the utmost, on the basis of the measured magnetic fields at the large number of points. The result of the computation is outputted as a table in which the numbers of the magnetic material shims 101 to be attached into the respective shim pockets are listed. An operator attaches the magnetic material shims 101 on the basis of the table. When the attachment of the magnetic material shims 101 has been completed, the superconducting magnet 21 is excited and the magnetic fields of the uniform magnetic field space 21 are measured again, so as to reevaluate the uniformity of the generated magnetic field after the magnetic material shim correction.
Usually, it is difficult to bring the magnetic field uniformity into a target value by one time of execution. Therefore, the operations as stated above are repeated several times, whereby the magnetic field uniformity is gradually enhanced.
                                          B            z                                          (                          r              ,              θ              ,              ϕ                        )                          =                              ∑                          m              =              0                        ∞                                                                                ∑                              m                =                0                            n                                                                                r                n                                                                            P                  n                  m                                                                  (                                      cos                                                                                θ                                    )                                                                          {                                                                            A                      n                      m                                                                                cos                                                                    (                                                  m                                                                                ϕ                                                )                                                                              +                                                            B                      n                      m                                                                                sin                                                                    (                                                  m                                                                                ϕ                                                )                                                                                }                                                                        (        1        )            where:
Bz denotes a magnetic field at coordinates (r, θ, φ),
the coordinates (r, θ, φ) are indicated in FIG. 15, and
Anm and Pnm denote those coefficients of respective components which are determined depending upon a magnetic field shape.
With the prior-art magnetic material shim mechanism as stated above, the shim tray is a unitary molded article. Accordingly, there has been the problem that the positions of the magnetic material shims cannot be finely adjusted, and that the versatility of the magnetic material shim arrangements is low. Therefore, in a case where the uniformity of the magnetic field (hereinbelow, termed "rough magnetic field") generated by the superconducting magnet itself is inferior, it has been sometimes impossible to make the uniformity correction by the prior-art magnetic material shim mechanisms. Besides, the shim tray designed optimally for the rough magnetic field characteristic of a specified superconducting magnet type cannot be diverted to the uniformity adjustment of a superconducting magnet type having another rough magnetic field characteristic. It has accordingly been necessary to design the optimal shim tray every superconducting magnet type.

Magnetic field adjustment device and magnetic field adjustment method for superconducting magnet


When a voltage abnormality error signal from a drive control section is at a low level, a control section determines a normal state. When the voltage abnormality error signal has arisen to a high level, the control section does not immediately determine an abnormal state and instead measures a time in which the voltage abnormality error signal is at the high level. If the measured time does not exceed a predetermined error timer value (limit value) T, the control section ignores this abnormal state as a temporary voltage abnormality. If the time in which the voltage abnormality error signal is at the high level exceeds the error timer value T, the control section determines a serviceman call error (SC) as the occurrence of voltage abnormality.

1. Field of the Invention
The present invention relates to an image forming. apparatus having a fixing device for fixing a developer image on a recording medium by means of self-heating of a heating member based on loss of an eddy current caused in the heating member by applying a radio-frequency magnetic field generated by a coil to the heating member.
2. Description of the Related Art
In an image forming apparatus using digital technology, generally known as an electronic copying machine, an original table on which an original is placed is exposed. An image signal corresponding to a reflection light amount from the original table is obtained from a CCD (charge-coupled device) line sensor. A laser beam corresponding to the image signal obtained from the line sensor is radiated on a photosensitive drum, and thus an electrostatic latent image is formed on a peripheral surface of the photosensitive drum. The electrostatic latent image is changed to a visible image by adherence of a developer (toner) which is (negatively) charged in advance. A paper sheet is fed to the photosensitive drum in accordance with the timing of rotation of the photosensitive drum, and the visible image (developer image) on the photosensitive drum is transferred onto the paper sheet. The paper sheet with the transferred developer image is fed to a fixing device.
The fixing device comprises a heating roller and a pressing roller put in pressure contact with the heating roller. The paper sheet is inserted between both rollers, and while the sheet is being conveyed, the developer image on the sheet is fixed by the heat of the heating roller.
An example of a heat source for the heating roller is an induction heater. The induction heater comprises a coil contained within the heating roller, and a radio-frequency generating circuit for supplying a radio-frequency current to the coil.
The radio-frequency generating circuit comprises a rectifier circuit for rectifying an AC power supply voltage, and a switching circuit for converting an output voltage (DC voltage) of the rectifier circuit to a radio-frequency power with a predetermined frequency. The coil is connected to an output terminal of the radio-frequency generating circuit (an output terminal of the switching circuit).
When the radio-frequency generating circuit is operated, a radio-frequency current is supplied to the coil, and the coil generates a radio-frequency magnetic field. The radio-frequency magnetic field is applied to the heating roller, and an eddy current is produced in the heating roller. The heating roller emits heat by itself based on a loss of the eddy current, and the developer image on the paper sheet is fixed by the heat.
In the case of the fixing device using the above-described induction heater, there are such error statuses as IGBT abnormality, voltage abnormality, circuit failure, and coil breakage.
In the case of the fixing device using the induction heater, however, the range of a voltage margin of an induction heater unit side circuit is narrower than that of a voltage margin of the image forming apparatus body. Thus, compared to a case where a conventional heater is used, the frequency of error statuses relating to voltage variations increases and the control may be disabled.
The present invention has been made in consideration of the above circumstances, and the object of the invention is to avoid a control-disabled state by properly coping with an error status in accordance with a voltage variation.
The present invention provides an image forming apparatus for forming an image, including a fixing device having a coil in a heating roller and causing the coil to generate a radio-frequency magnetic field, thereby producing an eddy current in the heating roller and fixing a developer image on a recording medium by means of self-heating of the heating roller based on an eddy current loss, the apparatus comprising: receiving means for receiving a voltage abnormality error signal from the fixing device; time-measuring means for measuring a reception time of the voltage abnormality error signal when the receiving means has received the voltage abnormality error signal; confirmation means for confirming whether the reception time measured by the time-measuring means exceeds a predetermined limit value; first control means for executing a control to ignore the voltage abnormality when the conformation means has confirmed that the limit value is not exceeded; and second control means for executing a control to perform an error process for the occurrence of voltage abnormality, when the confirmation means has confirmed that the limit value is exceeded.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.

Image forming apparatus having fixing device for fixing developer image on recording medium by induction-heating heat roller


An apparatus, system, and method are disclosed for teaching sequencing principles. An educational toy is provided with a plurality of panels that interlock with each other in a sequential pattern to form a multi-sided enclosure. A coded element may be represented on at least one of the panels. The coded element may be an element in a series forming a sequence to indicate the sequence pattern of the various panels. The sequence code or pattern to open the multi-sided enclosure is encrypted in the structural design of the various panels. Additional educational material may be represented on the various panels. In addition, an object containing educational material thereon may be included in the interior of the multi-sided enclosure.

1. Field of the Invention
This invention relates to educational toys and more particularly relates to educational toys for teaching sequencing principles.
2. Description to the Related Art
Toys generally provide entertainment for children during important development years. Often parents and educators utilize toys to teach children educational principles. Certain toys can be designed to target the educational needs and the developmental skills of specific developmental age groups. In certain instances, traditional toys may be altered to include specific educational elements intended to advance a child's capabilities. Such improvements can significantly contribute to the child's overall development and can increase the child's capacity for continued learning.
A traditional toy that has amazed and entertained audiences of all ages for more than one hundred years is the Japanese puzzle box. The puzzle boxes are wooden boxes traditionally decorated with geometric designs. Typically, the puzzle boxes have been used as jewelry boxes or "secret boxes" to guard special items. From the outer surface, the puzzle boxes appear to be completely enclosed because the boxes have no hinges, no locks, and no lids or coverings. Consequently, the user must learn a special sequence code designed specifically for each puzzle box prior to opening the box.
The sequence code to open the box is encrypted in the structural design of the side panels of the puzzle box. More specifically, the side panels are designed to uniquely engage adjacent side panels. As a result, the side panels may only be removed in a particular order because specially designed side panels block or prevent the removal of earlier inserted side panels.
For example, a side panel typically comprises grooves configured to slideably receive lips of an adjacent side panel. The grooves facilitate sliding the side panel in a particular direction relative to the adjacent side panels. The side panels generally slide or move in different directions and in various ways. Side panels may include one or more holes and/or one or more corresponding protrusions to complicate the sequence code of the puzzle box. The holes and protrusions create built-in stops to hold the side panels in place. The uniquely formed side panels, consequently, allow the puzzle boxes to have a distinct sequence code, or panel order, in order to completely assemble or disassemble a particular puzzle box.
The puzzle boxes, however, have various disadvantages from an educational perspective. Because the puzzle boxes typically contain geometric markings, the side panel sequence may be difficult to learn or distinguish, dramatically increasing the difficulty level of the toy. As a result, small children fail to benefit from the elements of problem solving and perseverance that motivate young adults with more advanced skills to decode the puzzle. In addition, the puzzle boxes only focus on one educational skill: correctly assembling the various panels to form a box. Other skills such as sequencing, counting, reading, communication, and the like are completely neglected.
From the foregoing discussion, it should be apparent that a need exists for an apparatus, system, and method that improve the traditional puzzle box in order to teach educational principles. Beneficially, such an apparatus, system, and method would teach sequencing principles as a multi-sided enclosure is assembled and disassembled. Additionally, various panels of the multi-sided enclosure would include educational material and coded elements to supplement the educational impact of the toy.

Apparatus, system, and method for teaching sequencing principles


A method and passive device for the coherent combination of two amplified and/or spectrally broadened optical beams using at least one bidirectional optical component (A1, A2), the device includes an amplitude division ring interferometer having optical splitting and recombining elements disposed so as to receive an incident optical beam (S0) and to split it spatially into a first secondary input beam (H1) and a second secondary input beam (H2), optical guiding elements disposed so as to define an optical path in the form of a ring in the interferometer, the at least one bidirectional optical component being disposed on the optical path of the ring interferometer, the splitting and recombining elements being disposed in such a way as to receive and to recombine spatially, temporally and coherently the first secondary output beam (H1″) and the second secondary output beam (H2″), so as to form a coherent output beam.

1. Field of the Invention
The present invention relates to a device and a method for the coherent combination of two optical beams transformed by optical components limited in energy and/or in average power and/or in peak power. Especially, the invention relates to a device and a method for the coherent combination of two optical beams amplified, for example, by two independent optical amplifiers. The invention also relates to a device and a method for the coherent combination of two optical beams spectrally broadened by two independent spectral broadening devices. The invention also relates to a device and a method for the coherent combination of two optical beams amplified and spectrally broadened, for example, by two non-linear optical amplifiers.
2. Description of the Related Art
It is searched to develop optical beams, and in particular energy laser beams with higher and higher peak power and/or average power while having an optical beam with an excellent spatial quality. It is also searched to develop reduced-volume devices based on the use of integrated optical components, such as an optical fiber amplifier, or a spectral broadening device based on a hollow capillary fiber, or on a large core (LMA or large mode area) fiber, or on small core fibers having particular dispersive properties. However, these optical components are limited in energy and/or in average power and/or in peak power. Different devices have been proposed to distribute the energy of a beam between several independent optical components, each optical component being limited in energy and/or in average power and/or in peak power. The difficulty is then to coherently recombine the different beams so as to preserve their spatial, spectral, temporal qualities, while increasing their energy, average power, peak power. In the case of the optical amplification, a first technique to obtain a high energy optical beam consists in amplifying a beam by two successive amplification stages. Starting from an oscillator generating initial pulses in the domain of 10 pJ to 1 μJ, a pre-amplifier allows obtaining pulses with intermediate energies of 10 nJ to a few μJ. A second optical power amplifier is necessary to reach the energies of 10 μJ to a few mJ required for most of the applications. However, the optical amplification in a non-linear optical medium is liable to generate non-linear effects (self-phase modulation . . . ) responsible for a deterioration of the optical quality of the amplified beam and more precisely of the temporal (ultra-short pulse) and/or spectral properties of the optical beam. Moreover, the high average power amplification may deteriorate the spatial properties of the beam (single-mode beam) due to the thermo-optical effects.
Another way to obtain a high energy and/or high power and/or high peak power beam is to use several sources or several independent amplifiers and to combine the beams coming from these different sources or from these different amplifiers. However, in order to preserve all the qualities of the laser beam, the recombination of the different beams must non only allow the spatial and temporal superimposition thereof, but also a coherent recombination, i.e. with a phase difference stable over time. The coherent combination of amplified laser beams is a very promising technique for the development of high energy and/or high average power and/or high peak power laser systems. However, the relative phases of different beams may fluctuate rapidly. The most difficult technical problem posed by the coherent recombination is to maintain a constant relative phase between different optical beams.
The coherent recombination of several optical beams has nevertheless been made by means of either passive or active devices.
The publication "Laser beam combining for High-Power, high-radiance sources", of T. Y. Fan, IEEE Journal of selected topics in Quantum Electronics, vol. 11, n° 3, 2005, indicates the fundamental conditions required to perform a recombination of laser beams (control of the power, relative phase, polarization, amplitude and alignment of each beam to be combined) and describes different methods for the coherent combination of optical beams, in order to obtain a high average power beam with spatial, temporal, spectral and almost-ideal polarization qualities.
The patent document U.S. Pat. No. 5,307,369 (D. E. Kimberlin) describes a passive system for the coherent combination of two amplifiers placed inside a common resonant cavity divided into two sub-cavities by a semi-reflective mirror. This device is similar to a double optical counter-reaction oscillator, a part of the beam emitted by the first laser amplifier being injected in the sub-cavity of the second laser amplifier, and vice versa. The output combined laser beam is a result of multiple coherent reflections occurring in the laser cavity. This device allows doubling the average power of a continuous laser beam or of synchronized laser pulses emitted by the two lasers. However, the differences of optical paths between the two sub-cavities induce phase-shifts that limit the stability of the passive device and the output power.
The passive combination appearing limited, various active devices for the coherent recombination of optical beams have been proposed. The active recombination is based on a direct or indirect measurement of the relative phase between the optical beams to be combined and on the introduction of a phase-shift actively controlled by a feedback loop on each optical beam. An active device for coherent recombination generally takes a part of the beam before or after recombination to extract therefrom a measurement of the phase-shift between the optical beams and adapts in real time the relative phase on each beam by means of an acousto-optic modulator, a piezoelectric mirror, or by adjustment of the optical pumping power.
Thus, for the amplifiers, an active device for coherent combination is generally used [Wei Liang, Naresh Satyan, Firooz Aflatouni, Amnon Yariv, Anthony Kewitsch, George Rakuljic, and Hossein Hashemi, "Coherent beam combining with multilevel optical phase-locked loops," J. Opt. Soc. Am. B 24, 2930-2939 (2007); T. Shay, V. Benham, J. T. Baker, A. D. Sanchez, D. Pilkington, and C. A. Lu, IEEE J. Sel. Top. Quantum Electron. 13, 480 (2007)]. The coherent combination has been shown in continuous and almost-continuous regime, and recently in femtosecond regime [cf. the publications L. Daniault, M. Hanna, L. Lombard, Y. Zaouter, E. Mottay, D. Goular, P. Bourdon, F. Druon, and P. Georges, "Coherent beam combining of two femtosecond fiber chirped-pulse amplifiers," Opt. Lett. 36, 621-623 (2011) and Enrico Seise, Arno Klenke, Jens Limpert, and Andreas Tünnermann, "Coherent addition of fiber-amplified ultrashort laser pulses," Opt. Express 18, 27827-27835 (2010)].
However, the active devices for coherent recombination are complicated because they need a real-time feedback electronic system whose implementation is difficult and expensive.
The power increase of the active devices for coherent recombination toward higher energies and/or average powers thus remains problematic.

Device and passive method for the coherent combination of two amplified and/or spectrally broadened optical beams


An apparatus as method for identifying, locating, and retrieving a downhole tool from a borehole. A controller is lowered into the borehole and is capable of detecting a signal from the tool. The signal can be broadcast from the tool, can be generated in response to a signal from the controller, or can be reflected from a controller signal. The controller processes the signal to identify the location and heading of the controller from the tool, and to guide the controller toward the tool. When the controller is moved proximate to the tool, a catch mechanism can be activated to connect the tool and controller housing. The tool is then dislodged for further operation, or is retrieved to the borehole surface.

The present invention relates to the field of well tools located downhole in a borehole. More particularly, the invention relates to an apparatus and method for locating and for retrieving downhole well tools.
Logging tools and other devices are run downhole in boreholes to investigate subterranean structures and to perform different exploratory and production operations. Logging tools are typically lowered into a borehole with a wireline which provides a structural connection to surface equipment and further provides a conductor for transmitting power and electrical signals. Wirelines are subject to failure due to wear and to binding forces exerted by the borehole wall against the tool. When a wireline separates from a logging tool in a vertical or inclined borehole, gravity pulls the tool lower within the borehole. Accordingly, the last known location of the logging tool may not accurately reflect the final resting location of the tool. Such location may be particularly difficult to locate in multilateral wells having multiple borehole branches.
Rig down time caused by a lost logging tool is costly. Wireline failure can strand a logging tool thousands of feet downhole in borehole, and abandonment of a million dollar logging tool is not economic. Loose logging tools impede further rig operations, and drilling rig time on offshore wells can cost over one hundred thousand dollars per day. This cost is increased by the travel time required by well contractors specializing in tool retrieval. When a tool is lost in a well, such well contractors may travel for one or more days to reach the borehole site before the tool retrieval operations can begin. Although certain of these costs can be avoided by effective equipment maintenance, logging tools are also lost due to tool sticking, formation collapse, and other causes unrelated to the wireline.
The process of locating and retrieving a lost tool (known as a "fish") is known as "fishing". Casing collar search tools are sometimes successful in locating lost tools. Alternatively, fishing operations are typically conducted by lowering a drill string into the borehole until the drill string lower end contacts the lost tool. Such contact places weight on the lost tool and reduces the weight on the drill string. If the tool is lodged in the borehole, the drill string weight can further drive the tool into the geologic formations. The reduction in drill string weight is monitored to identify contact with the downhole tool, however the weight reduction is almost imperceptible in deep boreholes requiring a long drill string. Additionally, false weight readings can occur in deviated and horizontal wells as the drill string contacts the borehole wall.
After the lower end of the drill string has located the downhole tool, an "overshot" is attached to the tool for retrieval to the borehole surface. Overshots typically comprise a coiled steel ribbon which is lowered over a tool. The overshot constricts to grip the tool as the drill string and overshot are withdrawn from the borehole. Overshots are effective when the tool is stuck in the borehole and the wireline is still attached to the tool. In such circumstances, the wireline guides the overshot over the tool end so that an effective grip can be achieved. However, overshots are difficult to operate when the tool has parted from the wireline and the tool location is unknown.
Accordingly, a need exists for an improved system for locating and retrieving tools downhole in a borehole. The system should be easy to deploy and to operate, and should be sufficiently flexible to handle different lost tool conditions.


In a method for generating a periodic training signal comprising cyclically expanded training symbols for a transceiver which transmits data via a data transmission channel using a predetermined number N of modulated carrier signals an address pointer for addressing a starting address in a memory is calculated for each training symbol on the basis of cyclic expansion parameters and, starting from the calculated starting address, 2*N stored samples of a transformed training symbol are read cyclically from the memory.

1. Field of the Invention
The invention relates to a method and an apparatus for generating a periodic training signal, particularly for an XDSL transceiver.
2. Description of the Prior Art
In modern telecommunication, data transmission at high bit rates on a subscriber line is playing an increasingly large role, since ever more applications, such as video or online gaming, require bi-directional data communication at ever greater data rates.
For transmitting digital data via a transmission channel, a series of modulation techniques for coding and modulating analogue signals which are routed to a reception apparatus via the transmission channel are known.
A technique which is recently becoming more and more significant is "multicarrier data transmission", which is also known as "Discrete MultiTone" (DMT) transmission or as "Orthogonal Frequency Division Multiplexing" (OFDM) transmission. Multicarrier transmission is suitable particularly for data transmission via transmission channels which add linear distortion. In comparison with single-carrier data transmission, advantages also arise with regard to the flexibility when matching the data rate or the transmission spectrum to the transmission channel or to the disturbance environment. Multicarrier transmission is used in conductor-based systems, for example, but also in the radio sector, for broadcast systems and for accessing data networks. Examples of DMT transmission applications are digital broadcast radio (DAB=Digital Audio Broadcast) and digital television (DVB=Digital Video Broadcast), or alternatively mobile radio applications.
An example of a representative of DMT transmission is ADSL technology, ADSL standing for "Asymmetric Digital Subscriber Line", that is to say the digital asymmetric subscriber line via a normal telephone line. ADSL denotes a technology which allows a bit stream at a high bit rate to be transmitted from a control centre to a subscriber and allows a bit stream at a low bit rate to be transmitted from the subscriber to a control centre. This technology makes use of the telecommunication line for conventional telephone services (that is to say voice transmission) and at the same time for data transmission. Besides ADSL technology, there are also further representatives of "xDSL technology", for example the broadband subscriber line (VDSL=Very High speed Digital Subscriber Line), where the frequency range for data transmissions extends up to 17 MHz. There are also plans for VDSL2 applications, which use even higher frequency ranges.
DMT transmission systems use a multiplicity of carrier frequencies, with the data stream to be transmitted being broken down into a large number of parallel substreams which are transmitted using frequency-division multiplexing. These substreams are also called single carriers. For modulation, the transmitted signal is made up of a large number of sinusoidal signals, with every single sinusoidal signal being modulated both in terms of amplitude and in terms of phase. This produces a multiplicity of quadrature-amplitude-modulated (QAM) signals. For DMT transmission, Inverse Fourier Transformation (IFT) is used in the transmitter and Fourier Transformation (FT) is used in the receiver. Fast and efficient signal processing algorithms exist both for the IFT and for the FT.
A problem which accompanies very broadband DMT transmission, in particular, arises as a result of the fact that the usable frequency range in VDSL extends up to 17 MHz and in planned VDSL2 applications extends up to 30 MHz. However, this wide frequency range also contains frequency bands for other services, such as the frequency bands for medium-wave and short-wave broadcast radio or the frequency ranges for amateur radio. Depending on the physical position, the subscriber terminals for the DMT transmission may be subject to interference from these services which use the same frequency range as the DMT transmission. This is referred to as "RFI interference", RFI standing for "Radio Frequency Interference". This RFI interference is narrowband interference for the very broadband frequency range used for DMT transmission, since these interfering RFI frequency ranges have a width of typically just a few kilohertz.
If a narrowband interfering signal of this type is overlaid on the DMT received signal, this has a negative effect on the demodulated DMT received signal. In this case, interference arises not just for the values (carrier frequencies) in the direct vicinity of the centroid frequency of this interference. Carrier frequencies (or user channels) for the DMT received signal which are at a much greater distance from this interfering frequency are also subject to interference.
Besides bandwidth-limited interfering signals, the transmitted modulated signal is also attenuated, linearly distorted and can be overlaid by other extraneous signals. Particularly crosstalk interference may arise when an adjacent line pair or a physically adjacent transmission channel is likewise used to transmit DMT signals. In such a case, the interference takes effect through crosstalk of the entire bandwidth for the DMT signal. Since xDSL, for example, involves a large number of line pairs being routed in a form bundled next to one another, a plurality of sources of crosstalk interference normally arise at the same time, and these have an adverse effect on a modulated analogue signal which is to be transmitted. In such an FEXT (Far End Cross Talk=crosstalk at the other end of the line) environment, it is desirable to take measures to improve the signal quality of the relevant received signals.
In addition to the sources of crosstalk interference and RFI interference, which are relatively easy to describe, the received signal is also usually subject to stochastic noise.
FIG. 1 shows a DMT transmission system based on the prior art.
Digital data DS to be transmitted are first of all supplied to an encoder CD via a serial-parallel converter SPW. Depending on the quality or on a measured signal-to-noise ratio for the single carriers in the multicarrier data transmission, a configuration for a QAM symbol is chosen for each single carrier. The configuration stipulates the number of bits which can be transmitted by a QAM symbol. Thus, a particular number of bits can be transmitted for each single carrier using a QAM channel, which can be represented by a respective complex frequency value. FIG. 2 shows the configuration for a 16 QAM encoder.
The encoder CD associates the data block to be transmitted, which has a particular number of bits, with the single carriers as QAM symbols. The relevant frequency values of this data block for transmission, or else called DMT symbol or DMT frame, can be combined to form a complex frequency vector D (fμ) FIG. 3 schematically shows the spectrum of a DMT signal modulated with N carrier signals.
In this case, the frequencies fμ correspond to the respective single-carrier frequency. A typical VDSL transmission method uses, by way of example, N=4096 carriers at a respective distance of Δf=4.3125 KHz from one another, which exhausts a frequency range or transmission bandwidth of 0-17664 MHz. This frequency vector D(μ), where μ subsequently indicates the frequencies fμ of the single carriers, is subjected to Inverse Fourier Transformation, which is illustrated by the function block IFFT in FIG. 1. The Inverse Fourier Transformation provides a real signal vector in the time domain with M=2·(N+1) components. FIG. 4 shows a block diagram of a conventional IFFT unit based on the prior art.
A buffer buffer-stores the real signal vector, which is expanded by a "guard interval" GI (cyclic prefix). The guard interval GI provides a cyclic expansion for the DMT frame. The guard interval GI fills the intervals of time at which DMT frames are successively sent. The signal which has been encoded from the digital data and subjected to Inverse Fourier Transformation has a spectrum with a periodicity of the relevant inverse sampling frequency T=1/fA.
The digitally filtered data signal to be transmitted is converted to analogue using a digital-analogue converter DAW and is bandwidth-limited by an analogue filter AF1.
This analogue bandwidth-limited transmitted signal A(t) is supplied to a line driver LT for amplification and is then passed to an appropriate transmission channel CH. In the case of xDSL, this is a two-wire telephone line, for example. Interfering influences which can adversely alter the modulated analogue signal are illustrated in FIG. 1 as an additionally injected noise signal R(t) as a model. This noise signal R(t) is injected additively.
At the receiver end, the modulated analogue received signal Z(t) which is subject to interference is first of all subjected to analogue filtering AF2 and is then converted to a discrete-time digital received signal Z(tk) by an analogue-digital converter ADW at the sampling frequency fA. This digital discrete-time received signal Z(tk) is digitally filtered in a digital filter DF2, is then buffer-stored in a buffer and is divested of the guard interval GI. A device for Fourier Transformation FT is used to convert the received signal into a received signal vector E(fμ).
Without disadvantageous influences as a result of the signal processing and particularly as a result of the channel frequency response, the received signal vector E(fμ) provides precisely the same complex frequency values as have been produced at the transmission end by the Inverse Fourier Transformation IFFT. In a practical system, however, this is never entirely the case. To eliminate the influences of the frequency response of the transmission channel CH, a frequency range equalizer EF is provided which weights the complex entries in the received signal vector E(fμ) with equalization coefficients. These equalization or filter coefficients eliminate precisely the effects which are brought about by the transmission channel CH, which is characterized by its transfer function C(f). The equalization filter EF therefore has a filter function which corresponds to the inverse of the channel transfer function C(f). The equalization filter EF thus provides at least one partial signal improvement as a result of the compensation for the measurable channel effects.
The equalized received signal is processed in a decision-maker unit E which associates the frequency values which have the greatest probability of being transmitted with the corresponding received and equalized frequency values and decodes the single QAM signals. To recover the transmitted data DS, parallel-serial conversion PSW is then performed and is output as received data DE.
FIG. 5 shows the cyclic expansion of a DMT symbol. Following the Inverse Fast Fourier Transformation, each symbol comprises 2*N samples, where N is the number of carrier signals used in the DMT modulation method. For cyclic expansion, the first LCS samples are appended to the DMT symbol as a cyclic suffix and the last LCP samples are added before the DMT symbol as a cyclic prefix, as illustrated in FIG. 5. In the case of DMT, the channel is equalized using the guard interval which is formed by the cyclic prefix. By inserting this safety interval between two successive transmitted symbols, the channel memory is completely switched off, which means that the intersymbol interference ISI decreases. The cyclic suffix is required in the case of VDSL in order to perform "Digital Duplexing". In the case of "Digital Duplexing", the transmitted and received signals in the two transceivers are shifted relative to one another such that no symbol limit in the transmitted signal interferes with the FFT of the received signal. This means that a VDSL system operating "digital duplexing" does not require an echo cancellation unit.
In addition, VDSL transceivers perform windowing of the cyclically expanded DMT symbol, as illustrated in FIG. 6. In this case, a predetermined number (β) of samples from the start and at the end of the cyclically expanded DMT symbol is multiplied by a window function in order to form the spectrum for the transmitted signal. This involves the sidebands of the DMT signal being lowered, so that interference for other frequency bands is minimized. The lowering of the sidebands in the case of VDSL is necessary in order to observe the permitted power spectrum density. In ADSL transceivers, no windowing of the cyclically expanded DMT symbol is performed.
In the case of transceivers based on the VDSL standard or the VDSL-2 standard, the cyclic continuation of the discrete multitone signal is switched on right at the start of the training phase. Switching on the cyclic continuation or the cyclic expansion right at the start of the training phase allows the complexity of the hardware of the VDSL transceiver to be kept relatively low, since it is not necessary to alter the data transmission rates at a later time. In addition, switching on the cyclic continuation during the actual training phase allows the transmitted signal to be constantly overlaid with or multiplied by a window function, so that the sidebands are lowered.
However, the result of switching on the cyclic continuation right at the start of the training phase in conventional VDSL transceivers is that the cyclically continued DMT signals can be used to train the equalizers and other adaptive signal processing blocks at the receiver end only with difficulty and with poor performance.
FIG. 7A shows a training signal which comprises a sequence of cyclically expanded training symbols, each cyclically expanded training symbol comprising a cyclic prefix (CP) and a cyclic suffix (CS).
FIG. 7B shows the associated time signal for a very simple example in which the signal is modulated merely with a carrier signal. The carrier signal is sinusoidal. As can be seen from FIG. 7, the boundaries between the cyclically expanded training symbols, i.e. times t0, t1, t2, t3, have signal discontinuities or sudden amplitude changes which prevent optimum setting of the equalizers. For digital duplexing, however, the provision of a cyclic prefix (CP) is indispensable in VDSL transceivers.
In ADSL transceivers based on the prior art, the equalizers and the other adaptive signal processing blocks are able to be set by virtue of the cyclic continuation not being switched on at the start of the training phase. Only at a later time is the cyclic continuation switched in within the training phase in ADSL transceivers. This is possible because ADSL transceivers have an echo cancellation unit and do not use digital duplexing. In addition, a window function is not normally used to lower the sidebands. This is normally done in ADSL transceivers using digital filters. Changeover from a training phase without cyclic continuation to a training phase with cyclic continuation increases the circuit complexity within ADSL transceivers substantially, however.

Method and apparatus for generating a periodic training signal


In a method for manufacturing an electron tube including a front substrate and a back substrate, a wiring and an electrode are formed on the front substrate and/or the back substrate. A component is mounted on the front substrate and/or the back substrate. A ring-less getter is mounted on at least one of the front substrate, the back substrate and the component. A vessel is assembled and sealed so that the front substrate faces the back substrate. A light is irradiated on the ring-less getter from outside of the sealed vessel, thereby activating the ring-less getter.

Referring to FIGS. 20 and 21, structure and function of a conventional fluorescent display device having a getter will be described. FIGS. 20 and 21 show cross sectional views of the conventional fluorescent display device, respectively. In FIGS. 20A and 20B, reference numerals 70, 71 and 72 represent a side substrate, a first substrate and a second substrate, respectively, which constitute a vacuum vessel of a fluorescent display device.
Referring to FIG. 20A, a supporting member 74 is fixed to an insulation layer 73 formed on the second substrate 72, wherein a metal vessel 75 having getter material 76 filled therein is attached to the supporting member 74. When a laser beam is irradiated from outside of the second substrate 72 onto a bottom of the metal vessel 75, the getter material 76 is evaporated to thereby form a getter film on the first substrate 71 (e.g., see, Japanese Patent Laid-Open Publication No. 11-260262).
In this case, the metal vessel 75 is usually made of a nickel-plated steel vessel of a ring shape. The getter material 76, e.g., made of Ba, Al or Ni, is filled into the vessel 75. This type of getter is usually called as a ring-shaped getter.
Referring to FIG. 20B, a vessel 77 accommodating ball-shaped getter material 78 therein is installed at an opening part of the first substrate 71. When a selective heating is applied on the getter material 78 by employing a selective heating unit, e.g., a laser unit, the getter material 78 is activated (e.g., see, Japanese Patent Laid-Open Publication No. 10-64457).
In FIGS. 21A and 21B, reference numerals 80, 81 and 82 represent a side substrate, a first substrate and a second substrate, respectively, which constitute a vacuum vessel of a fluorescent display device. Referring to FIG. 21A, powder type getter material 83 is filled in a recessed portion formed in the second substrate 82. When a laser beam is irradiated on the getter material 83 from outside of the second substrate 82, the getter material 83 is evaporated to thereby form a getter film on the first substrate 81 (e.g., see, Japanese Patent Laid-Open Publication No. 5-114373).
Referring to FIG. 21B, a getter material layer 84 is formed on the second substrate 82 by employing, e.g., deposition technique. When a laser beam is irradiated on the getter material layer 84 from outside of the second substrate 82, the getter material layer 84 is evaporated to thereby form a getter film on the first substrate 81 (e.g., see, Japanese Patent Laid-Open Publication No. 5-114373). Besides a deposition technique, a paste coating technique for coating a paste mixed with getter material may also be employed to form the getter material layer 84 (e.g., see, Japanese Patent Laid-Open Publication No. 2-177234).
In a conventional fluorescent display device as shown in FIGS. 20A and 20B, there is needed a vessel accommodating getter material or a supporting member for supporting the vessel. An opening to attach the vessel to a substrate is also needed. Accordingly, fabrication cost of the vessel increases. The attachment of the vessel to the substrate is not technically easy. There is a limitation in an accommodating place of the vessel, e.g., the substrate in FIG. 20B. Further, since a considerable space is necessary for attachment of the vessel, a dead space increases, the dead space being a space which is not useful in a display function thereof.
In FIG. 20A, the vessel 75 of a particular shape and the supporting member 74 to attach the getter should be installed between the substrates 71 and 72. As a result, the size thereof becomes large and the structure thereof becomes complex; and the handling and attachment thereof become difficult. Especially, the handling or attachment of a thin fluorescent display device, e.g., having a space between two facing substrates smaller than 1.4 mm becomes difficult. Even if the attachment thereof is possible, since a distance between the getter material 76 and the first substrate 71 is small, evaporated getter material does not diffuse far away. Therefore, a getter film formed on the substrate 71 has small area and it is impossible to obtain full getter effect.
Since the fabrication cost of the vessel of a particular shape is high and the handling burden thereof is considerable, the manufacturing cost of the fluorescent display device becomes expensive. Further, spaces for the vessel of a ring shape and a getter attachment member become large, thereby entailing limitations in providing slim and small fluorescent display device.
In FIG. 20B, the thermal expansion coefficient of the first substrate 71 should be set as about equal to that of the vessel 77; and the first substrate 71 and the vessel 77 should be attached closely to each other to prevent the vacuum level of a vacuum vessel of the fluorescent display device being lowered. Therefore, it is necessary to fabricate the vessel 77 and an opening of the substrate attaching the vessel 77 in a high accuracy.
Referring to FIG. 21A, since a recessed portion should be formed in the second substrate 82, the substrate fabrication cost becomes high. Further, since the getter material to be filled in the recessed portion is powder, handling thereof is not easy and the filling procedure thereof is burdensome. Since the forming place of the recessed portion is limited within the substrate and a thin glass substrate of about 1 mm thickness is used in a thin fluorescent display device, the depth of the recessed portion is limited in view of the fact that a vacuum vessel thereof should be strong enough to endure an atmospheric pressure applied thereto. Accordingly, it is difficult to fill the recessed portion with the getter material in an amount required to form the getter film.
In the conventional fluorescent display device as shown in FIG. 21B, an expensive deposition unit is necessary for forming the getter material layer 84; and in forming the getter material, the patterning thereof is difficult. Further, since it is difficult to form the getter material layer 84 by employing a deposition technique on a component other than the substrate, the formation place of the getter material layer 84 is limited in the substrate.
Since the getter material layer 84 formed by employing a deposition technique is thin, the glass substrate may be locally over-heated depending on a radiation time duration of a laser beam irradiated thereon, thereby entailing a development of a crack in the substrate; and it is difficult to form the getter material layer in an amount required to form a getter film.
In the conventional fluorescent display device as shown in FIG. 21B, a paste coating technique instead of the deposition technique may be employed. However, when employing the paste coating technique, an expensive paste coating unit is needed; the pattering procedure in forming the getter material layer is difficult; and it is difficult to form the getter material layer on a component other than the substrate. Further, in this case, a mixture other than the getter material in the paste may be evaporated to thereby produce unnecessary gas.
For example, in manufacturing a fluorescent display device, e.g., made of an acryl, even if the paste is formed by employing a solvent such as one which is thermally decomposed in sealing and exhaust procedures, the adhesion force of the getter material is not sufficient. Accordingly, the getter material may be detached due to evaporation of the getter material or the vibration thereof.

Electron tube and a method for manufacturing same


A food cutting device includes a housing and a cutting mechanism, wherein a feeding port is arranged at one side of the housing, and a discharging port is arranged at the other side of the housing; the cutting mechanism includes a cutting portion and a push-pull portion for controlling reciprocating movement of the cutting portion; the cutting portion includes a sliding component, a first cutter and a plurality of second cutters; the sliding component is slidably connected with the housing; both the first cutter and the second cutters are located on the side of the sliding component close to the feeding port, and are detachably connected with the sliding component; and the first cutter is parallel to a sliding direction of the sliding component, and is not parallel to the second cutters. The food cutting device can meet various cutting requirements of people and is efficient.

An important part in processing of food such as meat and vegetables is to cut food raw materials into desired shapes. At present, food is cut mainly by hand or through a food cutting machine in this industry. However, the efficiency of manual cutting is too low, which is not conducive to large-scale production. An existing food cutting machine is complex in structure, relatively complicated in operation, and higher in manufacture cost. In addition, the existing food cutting machine can only cut the food into slices or shreds because of the single function.


An apparatus for removing snow and ice from a roof includes a plurality of heating panels fastened to a rooftop surface. Each heating panel is formed from water-impermeable material and includes top and bottom surfaces formed from heat-resistant material. A plurality of elongated thermal-conductive heating elements are sandwiched medially of the top and bottom surfaces. A control panel is electrically coupled to one of the heating panels and a power cord is electrically coupled to an external power supply source. The present invention further includes a mechanism for electrically coupling the heating panels to each other and a mechanism for removably attaching the heating panels to the roof. A thermal sensor is operably connected to the control panel and the heating panels for monitoring an operating temperature of the heating elements.

1. Technical Field
This invention relates to a heating apparatus and, more particularly, to an apparatus for removing snow/ice from a roof.
2. Prior Art
During winter time, a substantial amount of snow may accumulate on the roof of a building. Some of the snow on the roof may melt and then freeze to ice along the gutters, forming "ice dams". As the ice in the gutters or eaves builds up, any water accumulating at the lower portion of the roof may be forced back and up and may get under the shingles of the roof, thereby leading to leaks if the ice is not removed from the roof. It is known to throw salt pellets onto the roof to assist in melting some of the snow or ice from the roof. However, the salt pellets are small and dissolve after only melting a small area at the upper portion of the snow, and thus are ineffective at melting the ice dams formed at the lower or shingle level of the snow and ice on the roof, since the lower layers of ice may be thick and/or may be beneath a substantial amount of snow.
It is also known to place a number of salt pellets into a mesh netting, such as a nylon stocking or the like, and throw the salt pellets and netting onto the roof. Because there is a substantial amount of salt pellets within the mesh netting, all of the salt pellets do not dissolve before they melt a substantial amount of the snow or ice in the area in which they were placed. However, the mesh netting only melts down to the level of the roof and does not melt any ice along the roof, since the mesh netting does not slide along the incline of the roof. Also, after the salt pellets have dissolved, the mesh netting is left on the roof and may clog the eves or the down spouts if not removed.
In some situations, a person may chisel at the snow or ice and/or shovel the snow or ice off the roof manually, either independent of any other ice removal technique or after placing salt pellets onto the roof to melt at least some of the snow and ice. Such an approach is very difficult and dangerous to accomplish because the person shoveling or chiseling the snow must be at or on the rooftop where they may easily slip and fall.
Accordingly, a need remains for an apparatus for removing snow/ice from a roof in order to overcome the above-noted shortcomings. The present invention satisfies such a need by providing a roof heating apparatus that is easily installed, convenient and effective, and eliminates the hazardous task of removing the ice or snow manually. Such an apparatus increases the life span of a roof by ensuring the integrity of the roof shingles is not diminished by the extreme temperatures created by the ice. An individual can either install and remove the apparatus once a year or install it once and leave it on the roof permanently.

Apparatus for removing snow/ice from a roof


A dynamic load damping apparatus is employed in a hydraulic steering system control circuit of an aircraft. The dynamic load damping apparatus is positioned in the hydraulic steering system control circuit in parallel with a control valve of the control circuit that functions as the hydraulic fluid source of the control circuit and an actuator that controls movements of a nose gear of the aircraft. The dynamic load damping apparatus dampens loads transmitted to the hydraulic actuator that controls the steering movements of the nose gear on the aircraft.

Hydraulic actuators are used in controlling the steering movements of an aircraft nose gear. These hydraulic actuators are often subjected to heavy loads from the nose gear of the aircraft travelling over a surface when taxiing to and from a runway and when traveling down a runway on aircraft takeoff and aircraft landing.
Various different hydraulic steering system control circuits have been developed to dampen the loads transmitted to the hydraulic actuator that controls the steering movements of the nose gear of an aircraft. Many of the existing hydraulic steering control circuits have complicated constructions that contribute to the costs involved in manufacturing the hydraulic steering system control circuits and in maintaining the hydraulic steering system control circuits.


An exposure apparatus for transferring a pattern on a mask onto a photosensitized substrate by exposure, having an illumination optical system, a mask stage for moving the mask and a substrate stage for moving the substrate. An attenuator is disposed between the light source and the photosensitized substrate for attenuating the illumination beam with a variable attenuator rate. A controller controls the output power of the light source and attenuator of the illumination beam such that the exposure energy approaches a predetermined desired value. A stage controller controls the velocities at which the mask stage and the substrate stage are moved for scanning according to the difference between the exposure energy measured by the sensing system and the predetermined desired value.

1. Field of the Invention
The present invention relates to an exposure apparatus for use in a photolithographic process for fabricating semiconductor devices, liquid crystal displays or others.
2. Description of the Related Art
Among various types of exposure apparatuses used for fabricating semiconductor devices and the like, exposure apparatuses, in which a pattern on a reticle (or mask) is transferred onto each of shot areas on a photoresist-coated wafer (or glass plate, etc.) by exposure, are generally provided with an illuminance control mechanism for ensuring that the exposure on each shot area will fall into an acceptable exposure range. The illuminance control mechanism used in such an exposure apparatus is primarily composed of two parts. One is an illuminance distribution control mechanism for suppressing unevenness in the illuminance distribution in an illumination area on the reticle. The other is an exposure control mechanism for maintaining the accumulated exposure in each shot area on the wafer at an appropriate exposure level.
In this regard, one of the most commonly used types of exposure apparatuses is the one-shot exposure type of projection exposure apparatus using the step-and-repeat technique (such as a stepper). In the one-shot exposure type of exposure apparatus, shot areas on the wafer are sequentially positioned at the exposure location, and the pattern on the reticle is transferred through a projection optical system onto the shot area positioned at the exposure location, by performing the one-shot exposure operation, when both the reticle and the wafer is held stationary. For the one-shot exposure type of projection exposure apparatus, the illuminance distribution control may be performed by intermingling a large number of light beams from the corresponding number of light source images by using an optical integrator (such as a fly-eye lens) disposed in the illumination optical system. Further, in a typical one-shot exposure type of projection exposure apparatus, since the exposure is performed on each shot area when the wafer is held stationary, the accumulated exposure in each shot area may be determined by a procedure comprising the steps of: branching out a part of the exposure illumination beam to obtain a monitor beam; continuously receiving the monitor beam during the actual exposure time so as to generate an electrical signal converted from the received beam; integrating the electrical signal to derive an integrated value; and scaling the integrated value by an experimentally determined scale factor.
Thus, the exposure control mechanism for the one-shot exposure type of projection exposure apparatus may be easily constructed. As an example, it may comprise: a photodetector (integrator sensor) for receiving the monitor beam; integrator means for integrating the detection signal produced from the integrator sensor; and control means for controlling either the intensity of the illumination beam or the exposure time such that the difference between the integrated value obtained from the integrator means and the desired value may be reduced.
In this relation, note that there have been proposed and used various sophisticated illumination methods in order to improve resolution and focal depth of the projection exposure apparatus, in particular for a very fine periodical pattern. Those methods include "modified light source method" which uses an illumination-system-aperture-stop comprising a number of openings arranged eccentrically to the optical axis of the illumination system (such as disclosed in U.S. patent application Ser. No. 791,138 filed on Nov. 11, 1991) and "annular illumination method" which uses an illumination-system-aperture-stop having an annular shape. Even when an illumination-system-aperture-stop is replaced with another having a different shape, the actual illuminance on the surface of the wafer may be monitored with precision if the photosensitive surface of the integrator sensor is positioned in a detection plane which is substantially conjugate to the surface of the wafer. Therefore, by controlling an appropriate parameter, such as the exposure time, in such a manner that the integrated value obtained through the integration of the detection signal from the integrator sensor may be converged to a predetermined desired value, the accumulated exposure on each shot area on the wafer can be made to fall into an acceptable range with ease.
More recently, as larger and larger patterns are used for the chips of semiconductor devices, it has become desirable to develop a projection exposure apparatus which is capable of projecting a much larger pattern onto a wafer with a higher efficiency. In order to satisfy this desire, one requirement is to ensure that the distortion will be kept below an acceptable limit over the entire region of an exposure area. Thus, engineer's attention has been drawn to the so-called step-and-scan type of projection exposure apparatus because it is highly effective for suppressing distortion over the entire region of a large exposure area. In the step-and-scan type of projection exposure apparatus, the wafer is stepped to sequentially position the shot areas on the wafer to the scanning start location, and the reticle and the wafer are moved in synchronism with each other and relative to the projection optical system for scanning, so as to serially transfer the pattern on the reticle onto each shot area on the wafer. The step-and-scan type of projection exposure apparatus is a development of the so-called slit-scan type of projection exposure apparatus (such as an aligner), in which a conventional 1:1 projection optical system is used and the reticle and the wafer are moved in synchronism with each other for scanning so as to serially transfer the pattern on the reticle onto the entire region on the surface of the wafer.
A typical illuminance distribution control mechanism (forming a part of illuminance control mechanism) for use in the slit-scan type or the step-and-scan type of projection exposure apparatus may comprise an optical integrator as with the one-shot exposure type of projection exposure apparatus. Where such an optical integrator comprises fly-eye lenses, the entrance surface of each lens element of the final-stage fly-eye lens is positioned in a plane optically conjugate to the plane of the pattern bearing surface of the reticle. Also, the illumination area on the reticle for the scanning exposure has an elongate rectangular shape or an elongate arc shape (this illumination area is referred to as the "slit-like illumination area" hereinafter), so that it is preferable for obtaining a higher illumination efficiency that each lens element of the final-stage fly-eye lens has a cross section of an elongate rectangular shape similar to that of the slit-like illumination area.
On the other hand, a typical exposure control mechanism for use in the scanning exposure type of projection exposure apparatus differs from those for use in the one-shot exposure type of projection exposure apparatus. In the scanning exposure type of projection exposure apparatus, each shot area on the wafer is scanned by the slit-like exposure field having its width (size in the scanning direction) smaller than the length (size in the scanning direction) of the shot area. Therefore, the control of the accumulated exposure in each shot area has to be performed such that the accumulated exposure in the slit-like exposure field may be kept at a constant level at all points on the wafer. If accumulated exposures at different points on the wafer have different values, it means that there is unevenness in the accumulated exposure in each shot area, which provides the same error as the unevenness in the illuminance within the illumination area experienced in the one-shot exposure type of projection exposure apparatus.
For the one-shot exposure type of projection exposure apparatus, one method of controlling the accumulated exposure is to operate the shutter to control the exposure time. For the scanning exposure type of projection exposure apparatus, however, the accumulated exposure at a particular point on the wafer can not be controlled by the operation of the shutter because each shot area is serially exposed by scanning. Therefore, for the scanning exposure technique, the accumulated exposure is controlled by, for example, scanning the reticle and the wafer at controlled, constant velocities. However, any method based on the control of the scanning velocities is not capable of fine adjustment of the accumulated exposure by means of time adjustment. Thus, for the scanning exposure technique, it is required to perform continuous illuminance control during the exposure operation on each shot area, so as to obtain illuminance stability with time. In relation to the illuminance control for the one-shot exposure technique, as one of the known methods for keeping illuminance at a constant level, continuous monitoring of the intensity of the illumination beam and feedback the monitored results to the power supply for the exposure light source is often performed so as to control the input power supplied to the exposure light source from the power supply. This technique is called the "constant-illuminance-control" technique.
Further, there have been proposed other methods of adjusting the quantity of light of the illumination beam by using neutral density filters, or using a mechanism including a pair of shading gratings disposed one on the other wherein the overlaps between the lines of these gratings are adjustable (U.S. Pat. No. 5,191,374).
Moreover, in recent years, there has been developed a technique for enhancing focal depth for a given pattern by reducing the numerical aperture (N.A.) of the illumination optical system and hence the ratio of the numerical aperture of the illumination optical system to that of the projection optical system (i.e., the coherence factor (.sigma.-value)).
When constant-illuminance-control technique mentioned above is used to perform the control for keeping the illuminance at a constant level, the following relation must be fulfilled in order to obtain an acceptable exposure: EQU P=E(L/V), or PV=EL
where:
E stands for the illuminance on the wafer established by the illumination beam (or the energy incident on unit area on the wafer per unit time); PA0 V stands for the scanning velocity of the wafer; PA0 L stands for the width of the slit-like exposure field on the wafer measured in the scanning direction; and PA0 P stands for the sensitivity (or the exposure energy per unit area) of the photoresist on the wafer. PA0 e.sub.0 stands for the desired value of the illuminance.
It is assumed that the width of the slit-like exposure field L is fixed and the sensitivity P of the photoresist may be of any given value. In such a case, acceptable exposures for, photoresists of different sensitivities may be achieved if either the scanning velocity V of the wafer or the illuminance E of the illumination beam is adjustable.
Therefore, as one method, the control of the accumulated exposure may be performed by adjusting the illuminance E of the exposure illumination beam. In such a case, it is required to measure the illuminance on the wafer with a short measuring time and precisely by means of an illuminance unevenness sensor (such as a photodetector), and control the output power of the light source for the illumination beam, or the attenuation of the illumination beam established by the attenuation unit disposed on the path of the illumination beam path, or other appropriate factors.
FIGS. 28(a) and 28(b) show photosensitive areas of two different conventional illuminance unevenness sensors provided on the wafer stages. FIG. 28(a) shows an example in which an illuminance unevenness sensor has a slit-like photosensitive area. In FIG. 28(a), there is shown an exposure field 402 having an elongate rectangular shape, extending in the non-scanning direction (the Y-direction) and substantially inscribed in a circular shaped effective exposure field 401 of a projection optical system. The slit-like photosensitive area 403 of the illuminance unevenness sensor has an elongate rectangular shape and extends in the scanning direction. The photosensitive area 403 is moved in the non-scanning direction along a solid line arrow in the figure to scan the exposure field 402, so as to detect any illuminance unevenness in the non-scanning direction. The length DA of the photosensitive area 403 is greater than the width LA of the exposure field 402 in order to complete the exposure measurement in the exposure field 402 with a single pass scan. FIG. 28(b) shows an example in which an illuminance unevenness sensor has a pinhole-like photosensitive area. In FIG. 28(b), the pinhole-like photosensitive area 404 is moved two-dimensionally as shown by the scan lines 405 in the figure to scan the exposure field 402, so as to measure the exposure distribution over the entire exposure field 402.
Unfortunately, it is not always possible to cause the accumulated exposure at each point on the wafer to fall into an acceptable range in a scanning exposure type of projection exposure apparatus, by using a constant-illuminance-control technique commonly used in the one-shot exposure type of projection exposure apparatus. More particularly, exposure light sources include electric-discharge lamps (such as a mercury-vapor lamp) and laser sources (such as excimer lasers and harmonic generators of YAG lasers). All of these types of light sources require considerably high input power, resulting in a drawback that it is difficult to adjust the illuminance of the illumination beam with high resolution and with high response speed by controlling only the input power supplied to the exposure light source.
This may not be a problem in the one-shot exposure type of exposure apparatus, in which even when the illuminance of the illumination beam from the exposure light source produces a stepwise variation, the accumulated exposure can be made to fall into an acceptable range with ease by merely controlling the shutter to adjust the exposure time in response to the variation. However, in the scanning exposure type of exposure apparatus, it is difficult to adjust the accumulated exposure by controlling the shutter because the exposure operation is continuously performed.
In view of the foregoing, it is a first object of the present invention to provide an exposure apparatus of the scanning exposure type in which even when the setting resolution in the input power supplied to an exposure light source is relatively low, the accumulated exposure on a photosensitized substrate can be made to fall into an acceptable range.
It is a second object of the present invention to provide an exposure apparatus of the scanning exposure type in which even when the setting resolution in the input power supplied to an exposure light source is relatively low, the illuminance of the illumination beam may follow the desired value with high response speed and with precision, with the result that the accumulated exposure on a photosensitized substrate can be made to fall into an acceptable range with ease.
With regard to a third object of the present invention, in the case where the exposure light source comprises an electric-discharge lamp utilizing an arc-discharge, such as a mercury-vapor lamp, there may occur variations in the illuminance of the illumination beam due to power supply noises, as well as there may occur such variations in the illuminance of the illumination beam known as "arc fluctuations" depending on the conditions of the convection of the gas filled in the tube of the electric-discharge lamp. These illuminance variations (fluctuations) are relatively small in amplitude. However, if such variations include high frequency components, a constant-illuminance-control technique for controlling the input power to the electric-discharge lamp may not follow the variation.
Therefore, when illuminance variations having high frequencies occur due to power supply noise during the scanning exposure operation of one shot area, the accumulated exposures at some points on that shot area may not fall into an acceptable range. This constitutes one of the factors in a reduced yield of the final products of semiconductor devices and the like. Even when a laser source such as an excimer laser (krypton-fluorine excimer laser, argon-fluorine excimer laser, etc.) or a harmonic generator of YAG laser is used as the exposure light source, the output of the light source may produce variations having high frequencies for some reason, so that the accumulated exposures at some points in each shot area may not fall into an acceptable range. Therefore, even when a laser source is used as the exposure light source, some kind of mechanism for suppressing illuminance fluctuations is required.
In the case where the quantity of light of the illumination beam is adjusted using neutral density filters, the adjustment can be made only in a stepwise manner by changing the filters. Further, the technique using a pair of shading gratings described above has a drawback that the dynamic range for continuously adjusting the quantity of light is narrow.
Further, in the case where the quantity of light of the illumination beam is adjusted by controlling the numerical aperture (N.A.), there has been a drawback that the illuminances on the reticle and on the wafer established by the illumination beam are lowered when the numerical aperture is reduced.
In view of the foregoing, it is a third object of the present invention to provide an exposure apparatus of the scanning exposure type in which even when an illumination beam outputted from an exposure light source produces illuminance variations which are smaller than a predetermined proportion of the normal illuminance and of high frequencies, the accumulated exposure on a photosensitized substrate can be made to fall into an acceptable range with ease.
In relation to the third object above, the present invention provides an exposure apparatus which is capable of highly suppressing the illuminance unevenness of the illumination beam (i.e., the unevenness in the accumulated exposure in each shot area), as well as capable of continuously adjusting accumulated exposure on the photosensitized substrate with a wide dynamic range for adjustment.
Also, in relation to the third object above, the present invention provides an exposure apparatus which is capable of preventing any reduction in the illuminances on the reticle and on the wafer established by the illumination beam, even when the numerical aperture of the illumination optical system is reduced, i.e., the ratio of the numerical aperture of the illumination optical system to that of the projection optical system, or the coherence factor (.sigma.-value), is reduced.
With regard to a fourth object of the present invention, arc fluctuations described above may appear as illumination variations at frequencies of about 30 Hz, for example. When arc fluctuations start appearing, the previous relationship between the input power supplied to the electric-discharge lamp and the illuminance of the illumination beam is no longer maintained, so that an ordinary constant-illuminance-control operation, in which the input power supplied to the electric-discharge lamp is controlled based on the actually measured illuminance, can not ensure that the accumulated exposure on a wafer will fall into an acceptable range.
Therefore, if arc fluctuations start appearing during the scanning exposure operation of a shot area, the accumulated exposures at some points in that shot area may no longer fall into an acceptable range. This constitutes another of the factors in a reduced yield of the final products of semiconductor devices and the like.
In view of the foregoing, it is a fourth object of the present invention to provide an exposure apparatus of the scanning exposure type in which even when the illumination beam outputted from the exposure light source produces fluctuations in its illuminance, the accumulated exposure on a photosensitized substrate can be made to fall into an acceptable range.
Further, where a sensor having an elongate, slit-like photosensitive area 403 which is longer than the width of the exposure field 402 in the scanning direction (FIG. 28(a)) is used for measuring the illuminance within the exposure field, a high processing speed may be obtained but a large space for the sensor is required on the wafer stage, which is an inconvenient drawback. In addition, the use of such elongate, slit-like photosensitive area has another drawback that the measurement may be made only with low accuracy because the long photosensitive area tends to result in high unevenness in the sensitivity of the sensor. On the other hand, where a sensor having a pinhole-like photosensitive area 404 (FIG. 28(b)) is used for this purpose, only a small space for the sensor is required on the wafer stage but a low processing speed results because the number of the measurement points must be large.
In view of the foregoing, it is a fifth object of the present invention to provide an exposure apparatus of the scanning exposure type, having an illuminance unevenness measurement means which provides rapid measurement and requires only a small space.


An integrated circuit for indicating the angular position of a rotating crankshaft corrected for crankshaft acceleration and deceleration. The circuit counts crankshaft markers spaced at equal angles about the crankshaft to produce a coarse grain position of the crankshaft. The circuit computes the time for the crankshaft to rotate to a series of incremental positions between contiguous markers and extrapolates a plurality of fine grain incremental positions of the crankshaft as a function of prior changes in velocity of the crankshaft. The coarse grain position is added to a fine grain position to produce a real time position of the crankshaft. A digital position bus communicates the real time crankshaft position. The circuit also computes both the velocity of the crankshaft after detecting each marker and the average acceleration of the crankshaft between contiguous markers for output over a digital velocity bus and a digital acceleration bus.

Modern engine control systems use a microprocessor to monitor critical engine parameters, such as engine speed and load, to achieve precise control of ignition timing. In known ignition timing control systems, a read only memory (ROM) stores a map or table of spark advance firing angles as a function of engine speeds and loads. After reading the current engine speed and load, the microprocessor performs a table lookup to obtain the ignition advance angle at which a spark plug should be fired. The microprocessor must also track crankshaft angular position so that spark firing can be triggered at the crankshaft angle corresponding to the spark advance angle determined by the table lookup.
To track a rotating crankshaft, it is known to monitor a disk secured to the crankshaft where the disk includes a number of teeth or markers spaced at equal angles around the periphery of the disk. Counting markers provides a coarse measure of the angular position of the crankshaft which, in turn, allows spark firing at the proper angle in the engine cycle. It is also known to provide higher resolution or fine crankshaft position signals between two adjacent teeth by extrapolating or predicting a plurality of positions based on the elapsed time of the immediately preceding marker interval.
If the crankshaft rotated at a constant velocity, predicting the fine angular increments during each subsequent marker interval would be a straightforward linear extrapolation from the previous marker interval. However, the crankshaft of a running engine experiences transient accelerations and decelerations which distort the crankshaft positions predicted using a linear extrapolation system. U.S. Pat. No. 4,814,704 recognizes the problem of predicting crankshaft position in the presence of these transient variations in crankshaft speed but simply resynchronizes upon arrival of a new crankshaft marker, thereby correcting the error which was introduced during its linear extrapolation.
U.S. Pat. No. 4,081,995 discloses an apparatus and method for extrapolating the angular position of a rotating crankshaft using a nonlinear or exponential down counter to approximate acceleration conditions. Using the exponential down counter results in reduced extrapolation errors over linear extrapolation techniques; however, significant errors still arise with the position approximation technique described in U.S. Pat. No. 4,081,995.

Angular position extrapolation of a rotating crankshaft corrected for crankshaft acceleration and deceleration

Automotive Integrated Electronics Co., Inc.


An opportunity to assist with remediation of a file at a remote particular host device is identified. One or more remediation techniques are identified that can be applied to assist with remediation of the file at the particular host device. In one aspect, one or more remediation scripts are identified from a plurality of remediation scripts for remediation of the file and provided to the particular host device for execution on the particular host device. In another aspect, a remediation tool is identified and launched on a computing device remote from the particular host device with operations of the remediation tool applied to resources of the particular host device. In another aspect, at least a portion of the remediation techniques are remotely initiated to be performed locally at the particular host device.

The Internet has enabled interconnection of different computer networks all over the world. The ability to effectively protect and maintain stable computers and systems, however, presents a significant obstacle for component manufacturers, system designers, and network operators. Indeed, each day thousands of new threats, vulnerabilities, and malware are identified that have the potential of damaging and compromising the security of computer systems throughout the world. Antivirus, antispyware, and other antimalware products and solutions have been developed. Some traditional antimalware products employ a host-centric approach in which the bulk of the functionality of the antimalware tool is installed onto the host, with the antimalware tool occasionally downloading an update of remediation tools, virus definition files, and other content to keep the antimalware tool abreast of newly discovered malware and other developments. The antimalware tool can then screen objects, processes, downloads, and other events on the host machine to determine whether malware exists on the host, per the content received from the updater, as well as attempt to remediate the malware using functionality available at the host-based antimalware tool. In some cases, the host-based antimalware tool can further attempt to remediate any malware discovered on the host by attempting, for instance, to quarantine or remove the file from the host.
Like reference numbers and designations in the various drawings indicate like elements.


A scanning method in a wireless local area network (WLAN), a station supporting the scanning method, and a new type of interworking information element format including information about a distribution system (DS) are disclosed. In the scanning method, information about a DS is included in a beacon frame or a probe request frame/frame response frame. Such information about the DS may be included in a network type field of, for example, an interworking information element. In an active scanning method, a user equipment (UE) may specify its DS type by transmitting a probe request frame including DS information such as the DS type or the like. In a passive scanning method, the UE may select a suitable AP by using DS information such as a DS type included in the beacon frame or the like. The DS type may be information indicating whether a DS is a wireless network such as a mesh network or any other wired network.

Recently, diverse wireless communication technologies are under development in line with the advancement of information communication technology. Among them, a wireless local area network (WLAN) is a technique allowing mobile terminals such as personal digital assistants (PDAs), lap top computers, portable multimedia players (PMPs), and the like, to wirelessly access the Internet in particular service providing areas such as homes, offices, or aircraft based on a radio frequency technology.
The early WLAN technique supported the rate of 1˜2 Mbps through frequency hopping, spread spectrum, infrared communication, and the like, by using a 2.4 GHz frequency based on IEEE 802.11. Recently, the advancement of wireless communication technology allows supporting of a maximum rate of 54 Mbps by applying orthogonal frequency division multiplex (OFDM) technology and the like to the WLAN. Further, IEEE 802 has developed a wireless communication technique for improving quality of service (QoS), allowing compatibility of access point (AP) protocols, achieving security enhancement, making radio measurement or radio resource measurement, allowing wireless access in vehicular environment, ensuring fast roaming, establishing a mesh network, performing inter-working with external network, performing wireless network management, and the like, and put those techniques into practical use, or are still developing them.
In the WLAN system, a user equipment (UE), a non-AP station performs a scanning method to search for an accessible AP. The scanning method is a method for acquiring a list of candidate APs to be combined in a combining method, a follow-up method, and information about each AP.
The scanning method includes two types of method. A first scanning method is a passive scanning method which uses a beacon frame transmitted from an AP. In this method, a UE, which wants to become a member of a particular extended service set (ESS), receives beacon frames the APs periodically transmit to acquire a list of candidate APs transmitting beacon frames including the same service set ID (SSID) as the ID of the ESS to be connected and information about each candidate AP.
The second method is an active scanning method. In this method, a UE, which wants to become a member of a particular ESS, first transmits a probe request frame. The probe request frame includes an SSID to be connected. Respective APs receive the probe request frame, and if the APs have the same SSID as that included in the received probe request frame, they transmit a probe response frame to the UE. Accordingly, the UE can acquire a list of candidate APs based on the received probe response frames.
If, however, the UE is located in a hotspot, a list of candidate APs that can be acquired through the scanning method is so huge that overhead of the UE gradually increases in the scanning method. For example, in the passive scanning method, the number of scanned beacon frames including the same SSID as received is considerably increased to cause overhead. Also, in the active scanning method, the number of probe response frames with respect to the transmitted probe request frame is drastically increased, increasing overhead with respect to the scanning method as much.
However, with all the possibility of increasing overhead with respect to the scanning methods, information provided by the current scanning methods falls short of providing sufficient information regarding a network to be connected by the UE. In particular, with types of distribution systems (DSs) diversified, when the UE desires to access an external network, not the WLAN, to use services provided therefrom, the UE needs sufficient information about the access network (AN), but the current scanning methods fail to meet the need for the information about such DSs or AN.