A bandgap reference circuit with curvature compensation. The circuit includes a first current mirror that mirrors the current conducted by the bandgap reference. A difference between the gate-to-source voltages in the two legs provides a first mirrored current with non-linear temperature stability. This first mirrored current is again mirrored by a second current mirror in which the mirror transistors also have differing gate-to-source voltages, with the current from this second current mirror coupled to the bandgap reference to compensate for curvature in the CTAT current over temperature.

This invention is in the field of voltage and current reference circuits as used in integrated circuits. Embodiments are directed to curvature compensation in reference circuits of the bandgap reference type.
The powerful computational and operation functionality provided by modern integrated circuits has enabled the more widespread distribution of computing power in larger-scale systems. One example of such distributed electronic functionality is the so-called "Internet of Things" (IoT) contemplates the widespread deployment of electronic devices as sensors and controllers, with networked communications among those devices. Modern smartphones and wearables also deploy computational and operational functionality into a large number of distributed nodes; implantable medical devices constitute another type of distributed functionality. Many of these applications necessitate the use of batteries or energy scavenging devices to power the integrated circuits. As such, many modern integrated circuits are called upon to be "power-aware", designed to consume minimal power during operation and standby.
Voltage and current reference circuits are important functions in a wide range of modern analog, digital, and mixed-signal integrated circuits, in order to optimize the performance of such circuits as operational amplifiers, comparators, analog-to-digital and digital-to-analog converters, oscillators, phase-locked loops and other clock circuits, and the like. This optimization is especially important for power-aware applications in which power consumption can be a dominating factor in circuit and system design. As well known in the art, voltage and current reference circuits ideally generate their reference levels in a manner that are stable over variations in process parameters, power supply voltage levels, and operating temperature.
FIG. 1 illustrates "bandgap" reference circuit 10, constructed in the conventional manner. In this example, p-channel metal-oxide-semiconductor (PMOS) transistor 6p, with its source at the Vdd power supply voltage, serves as a current source to two bipolar transistor branches to which its drain is connected through resistor 7. One branch is formed by resistor 9a connected between resistor 7 and the emitter of p-n-p transistor 8a, while the other branch is formed by resistor 9b connected between resistor 7 and resistor 11, which in turn is connected to the emitter of p-n-p transistor 8b. Typically, transistor 8b will have an emitter area that is some multiple N:1 of the emitter area of transistor 8a, so that the currents conducted by the two transistors are similarly ratioed. The bases and collectors of transistors 8a, 8b are connected to the Vss reference level. This construction of reference circuit 10 is common in complementary metal-oxide-semiconductor (CMOS) integrated circuits, as bipolar p-n-p transistors 8a, 8b are typically present as parasitic devices in the CMOS structure. In this conventional arrangement, the emitter of transistor 8a is connected to one input of amplifier 15, while the other input of amplifier 15 is connected to the node between resistors 9b and 11. The output AMPOUT of amplifier 15 is connected to the gate of transistor 6p.
According to this construction, the output voltage AMPOUT from amplifier 15 is based on one parameter that varies in a manner complementary to absolute temperature (CTAT) combined with another parameter that varies proportionally with temperature (PTAT). The CTAT parameter in this circuit is the base-emitter voltage of transistor 8a, and the PTAT parameter is the difference in the base-emitter voltages of transistors 8a, 8b, which is reflected as the voltage drop across resistor 11. The sum of these two voltages is thus constant over variations in temperature, at least to a first approximation, and appears at the drain of transistor 6p as output voltage VBG. This output voltage VBG is typically at about the bandgap voltage of the semiconductor (e.g., 1.2 volts for silicon), and as such reference circuit 10 is thus commonly referred to in the art as a "bandgap reference circuit". Additional transistors (not shown) are typically mirrored with PMOS transistor 6p to establish and provide output currents that are similarly stable over variations in temperature. Reference circuit 10 can be made "self-biased" by biasing amplifier 15 with a copy of the current conducted by transistor 6p, in which case the circuit will be relatively insensitive to variations in the Vdd power supply voltage.
However, the base-emitter voltages of bipolar transistors 8a, 8b are not exactly linear over temperature because of non-linear temperature behavior in the bipolar junction transistor (BJT) saturation current. The combination of the CTAT base-emitter voltage with the PTAT difference in base-emitter voltages is thus often insufficient to attain the desired temperature stability of the reference voltage. This variation of base-emitter voltage (Vbe) over temperature is generally referred to as the "curvature" of Vbe, referring to the curve in the Vbe vs. temperature characteristic from the linearly CTAT ideal.
FIG. 2 illustrates a simplified schematic of reference circuit 10′ including curvature compensation according to one conventional technique. Reference circuit 10′ is constructed similarly as reference circuit 10 described above in connection with FIG. 1, but with n-channel MOS (NMOS) transistor 6n in place of PMOS transistor 6p. In this conventional reference circuit 10′, curvature compensation is provided by resistor 13, which is formed in an n-type well in the integrated circuit; in contrast, resistors 9a, 9b, 11 are typically formed in polycrystalline silicon. Because of its formation in an n-well, resistor 13 will exhibit a non-linear temperature coefficient, and thus the collector currents will develop a non-linear voltage across resistor 13. The non-linearity of this voltage drop across resistor 13 tends to compensate for the non-linearity of Vbe over temperature. While this curvature compensation is relatively easy to design and implement, without requiring significant modifications to existing circuits, the n-well realization of resistor 13 introduces additional process sensitivity, specifically sensitivity to variations in n-well sheet resistance, which is a difficult parameter to control over typical process windows. This approach to curvature compensation is thus typically less robust than required for good yield and performance.
Another conventional approach for curvature compensation involves the introduction of a non-linear bias current to cancel out the non-linearity of Vbe over temperature. Filanovsky et al., "BiCMOS Cascaded Bandgap Voltage Reference", IEEE 39th Midwest symposium on Circuits and Systems, Vol. 2 (IEEE, 1996), pp.943-946describes this approach as carried out by a translinear current polynomial circuit to produce a current that is PTAT to the third degree (i.e., proportional to T3), and a current that is PTAT to the fourth degree. These currents are added with the collector current in the reference circuit to compensate for non-linearities. However, this approach necessitates the formation of cascaded bipolar transistors, and thus not conducive to implementation in CMOS technologies (in which the collectors of parasitic bipolar devices are all connected to the substrate).
Another approach to curvature compensation is described in U.S. Pat. No. 6,255,807, incorporated herein by reference. According to this technique, an additional amplifier gain stage is added to the reference circuit, and adds non-linearity into the feedback loop. While this technique provides good curvature compensation, the additional amplifier stage requires significant chip area to implement, and consumes additional power that renders it less than optimal for power-aware applications.
By way of further background, U.S. Pat. No. 9,104,217, issued Aug. 11, 2015, commonly assigned herewith and incorporated herein by reference, describes a reference circuit with curvature compensation implemented by way of a translinear circuit that draws a non-linear current from the bipolar collector currents, and that can be realized by MOS transistors.

Bandgap reference circuit with curvature compensation


Current usage from a battery in an implantable cardiac device is tracked. The apparatus includes a battery current sensor having multiple current ranges. The current sensor produces a first signal representative of current drawn from a battery. A current range selector selects a current range for the battery current sensor and produces a second signal representative of the current range. An accumulator accumulates the first signal based on the second signal over time to generate an output signal representing usage of the battery.

An implantable cardiac device is a medical device that is implanted in a patient to monitor electrical activity of the heart and to deliver appropriate electrical and/or drug therapy, as required. Implantable cardiac devices include, for example, pacemakers, cardioverters and defibrillators. The term "implantable cardioverter defibrillator" or simply "ICD" is used herein to refer to any implantable cardiac device.
An ICD employs a battery to power its internal circuitry and to generate electrical therapy. The electrical therapy can include, for example, pacing pulses, cardioverting pulses and/or defibrillator pulses.
When a battery is manufactured, its energy capacity is known. Specifically, it is known how many Ampere-Hours of energy the battery can deliver. Based on the known battery energy capacity and based on predicted usage, battery life can be predicted and a replacement interval established. With this approach, a conservative margin in remaining battery life is observed to prevent device failure due to a depleted battery. Alternatively, actual battery usage can be tracked, and the device can be replaced when the actual remaining energy capacity of the battery falls below a predetermined threshold. This second approach of tracking battery usage and replacing a device when replacement is actually required is preferred since it reduces unnecessary device replacements. It could, also, be used to inform the physician of unexpected battery depletion or excessive current drain that might be a sign of malfunction.
Conventional methods for tracking battery usage use estimation techniques to determine how much energy is left in the battery. As previously mentioned, the estimation techniques are not accurate and require observation of conservative margins. Other conventional systems measure battery voltage and use the voltage measurement as an indicator of how much energy is left in the battery. This method is problematic because of unexpected drops and hikes in voltage within the battery circuit which can lead to inaccurate battery life predictions.
What is needed is a better and more accurate system and method for keeping track of the battery usage, so that the end-of-life of the battery can be predicted with greater precision.

Battery charge indicator for implantable pacemakers and defibrillators


Compositions for and methods of increasing the number of neutrophils in a pediatric subject and stimulating the immune system of a pediatric subject.

Infants and children are exposed to a variety of pathogens, and consequently, the incidence of infectious diseases peaks in the first 4 years of life. Newborns are generally protected by antibodies received through the placenta before birth and subsequently through breast milk after birth; yet newborns do not have mature immune systems and are often incapable of mounting an effective immune response. Indeed, on a cellular level, infants have a decreased ability to concentrate leukocytes where necessary. (Maternity and Gynecologic Care, Bobak, Jensen, Zalar, Fourth Edition, p. 470) Consequently, newborns are not able to limit invading pathogens due to a generalized hypofunction of their inflammatory and immune mechanisms. As such, improving the immune response in infants and/or children would provide an opportunity to reduce the incidence of infections and to maintain or improve the overall health of pediatric subjects.
The infant gut microflora is rapidly established in the first few weeks following birth, and it has a great impact on an infant's immune system. The nature of this intestinal colonization is initially determined by the host's early exposure to environmental sources of microbes as well as to the health of the infant. Whether the infant is breast-fed or formula-fed also has a strong influence on the intestinal bacterial population.
Human milk contains a number of factors that may contribute to the growth and population of the gut microflora of infants. Among these factors is a complex mixture of more than 130 different oligosaccharides that reach levels as high as 8-12 g/L in transitional and mature milk. Kunz, et al., Oligosaccharides in Human Milk: Structure, Functional, and Metabolic Aspects, Ann. Rev. Nutr. 20: 699-722 (2000). These oligosaccharides are resistant to enzymatic digestion in the upper gastrointestinal tract and reach the colon intact, where they then serve as substrates for colonic fermentation.
Because cow's milk and commercially available infant formulas that are based on cow's milk provide only trace amounts of oligosaccharides, prebiotics can be used to supplement the diet of formula-fed infants. Prebiotics have been defined as non-digestible food ingredients that beneficially affect the host by selectively stimulating the growth and/or activity of one or a limited number of cells in the colon that can improve the health of the host.
Because both the interaction among dietary components and among the microflora of the intestinal ecosystem are very complex, the matrix of an infant formula or other pediatric nutritional supplement may influence the effectiveness of prebiotics and oligosaccharides when such ingredients are provided as supplements in the diet of a formula-fed infant. Moreover, the type and concentration of proteins used in a formula matrix may also modulate the intestinal microbiota. (Boehm et al., Structural and Functional Aspects of Prebiotics Used in Infant Nutrition, The Journal of Nutrition.) Because human milk is the preferred source of infant nutrition, it is desirable to provide a formula matrix that mimics the qualities of human milk by allowing for effective supplementation of prebiotics and oligosaccharides as functional food ingredients.
Accordingly, it would be beneficial to provide a nutritional composition for pediatric subjects comprising a nutritional supplement that stimulates the immune system, wherein the supplement is provided in a formula matrix that does not inhibit the beneficial effects of the supplement. Furthermore, it would be beneficial to provide methods for enhancing and improving the immune response of a pediatric subject via administration of a nutritional composition that is well-tolerated by pediatric subjects.

This patent is subject to a terminal disclaimer.

Compositions for enhancing immune function in a pediatric subject


A glove donning and removal apparatus for donning, a glove sandwiched between a pair of upper and lower feed sheets is advanced towards a glove dispensing opening. Grabber arms expand the glove hand opening to enable a user to easily insert a hand into the hand opening. For removal, secondary top and bottom feed rolls having adhesively coated top and bottom feed sheets are moved towards a glove removal opening. The adhesive-coated top and bottom feed sheets cooperate to strip a glove from a user's hand when the hand is placed on a glove removal surface in the glove removal opening.

The present invention relates to a glove donning and removal apparatus.
Disposable gloves have been utilized in the health care industry, food handling industry and elsewhere for many years. In many instances, disposable gloves are preferred over the current standard practice of washing hands for at least two minutes with an appropriate disinfectant which can ultimately compromise skin integrity and lead to skin infection and/or abrasion. In health care, the use of gloves by a heath care provider protects a patient from any contaminants that may reside on the health care provider. Of course, they also protect the heath care provider from possible contamination resulting from handling a patient.
While disposable gloves are preferred and utilized by most health care providers, special precautions must be taken to insure that the gloves are not contaminated by the user as they are being donned and that other stored gloves are not contaminated or touched by the user. Additionally, precautions must be taken during the glove removal process to ensure that the hands of a user do not contact the outer surface of the glove and become exposed to any contamination thereon and that removal of the glove does not splatter or aerosolize contaminated matter. Lastly, used disposable gloves must be disposed of safely.
It is desirable to provide a glove donning and removal apparatus that maintains the cleanliness of the gloves until they are utilized, assists a user in donning and removing a glove, prevents contamination of a glove during the donning process, prevents a user's hand from contacting the outer or working surface of a glove during the removal process, and immediately encases or seals a used glove for disposal after the glove has been removed.


A facility for determining article influence and author authority based upon cites of the author's articles by other authors is described. Authors post new articles to their blog covering one or more memes, which describe the content of the article. The facility determines other web pages that share the same memes as the articles to form a context set, and then identifies those authors, called stakeholders, that commonly cite posts from web pages within the context set. Stakeholders are those with some knowledge about a particular topic that also write articles on the topic. Articles cited by stakeholders are considered more influential than those that are not cited, and a frequently cited author will have more authority for a given meme than one who is largely ignored, as indicated by receiving few article citations.

In the past, publishers generally produced written media at significant expense, working with a team of authors and editors to produce content on a particular topic. For example, magazines generally have a well-defined topic and are written by authors that are knowledgeable about the topic, and are edited to ensure the quality of the content. Posting written content through web logs (blogs) on the Internet has reduced the cost of producing and distributing written works to near zero, so that today anyone with a computer and an Internet connection can be a publisher of content. As a result, there has been an explosion in the number of authors producing web logs (blogging), and the number of posts by authors to those blogs.
The dramatic increase in the number of authors and the ease of distribution facilitated by blogging has given rise to a broad range of quality among blogs, as no publisher or team of editors typically reviews blog content. Readers are now faced with the problem of wading through numerous blogs to identify content that is worthwhile to read. Similarly, authors of blogs are interested in rising above the noise generated by the other blog authors. Authors want posts to their blogs to be widely read and carefully considered, particularly where the author has a high level of authority on the topics being written about.

Assessing author authority and blog influence


A recording medium including a resin substrate having a first thermal expansion coefficient, a center hole, a first surface, and a second surface opposite to the first surface, a recording layer formed on the first surface of the resin substrate and having a recording region, an inner nonrecording region formed inside the inner periphery of the recording region, and an outer nonrecording region formed outside the outer periphery of the recording region, and a protective layer formed on the second surface of the resin substrate except an inner peripheral region having a predetermined range from the center hole, the recording region, and the outer nonrecording region. The thermal deformation suppressing layer has a second thermal expansion coefficient smaller than the first thermal expansion coefficient.

1. Field of the Invention
The present invention relates to a recording medium having a resin substrate.
2. Description of the Related Art
As a method of increasing the recording density of an optical disk, examinations have been made on increasing the numerical aperture (NA) of an objective lens and shortening the wavelength of a laser to be used. In a 3.5-inch magneto-optical disk drive being used at present, the numerical aperture of an objective lens is 0.55. By increasing the numerical aperture of the objective lens up to 0.70, the size of a beam spot can be reduced from about 1.0 μm as a conventional size to 0.78 μm. A similar effect can be obtained by shortening the wavelength of a laser to be used. By changing a laser having a wavelength of 650 nm being used at present into a blue-violet laser having a wavelength of 405 nm, the conventional beam spot size can be reduced from about 1.0 μm to 0.65 μm. As a result, the marks on the optical disk can be shortened and the track pitch can be narrowed to thereby allow high-density recording.
In the case of applying such means for allowing high-density recording, it is known that the margin to the warpage of a resin substrate due to its thermal deformation not particularly becoming a problem in the prior art is reduced. This is due to the fact that even if the warpage of a single-layer resin substrate is the same in level, optical aberration becomes likely to occur because of the increasing of the numerical aperture or the shortening of the wavelength, causing a perturbation of the shape of a beam spot and therefore largely interfering with stable recording and reproducing operations. Further, regarding the problem of optical aberration due to the increasing of the numerical aperture, the optical aberration is sensitive to variations in thickness of the conventional resin substrate having a thickness of 1.2 mm, causing an extremely large amount of optical aberration due to variations in thickness of the resin substrate.
Therefore, it is essential to reduce the thickness of the substrate in the case of using an objective lens having a high numerical aperture. However, when the thickness of the substrate is reduced, the warpage due to thermal deformation tends to become large, so that optical aberration due to the warpage instead becomes likely to occur. In a conventional 3.5-inch magneto-optical disk, a recording layer is formed on a first surface of a transparent resin substrate in the range of 18 to 42 mm along the radius of the substrate from the center thereof. This recording layer and a second surface of the resin substrate as an incident surface for a laser beam are coated with organic protective films.
Japanese Patent Laid-open No. Hei 11-16211 discloses a method of suppressing the warpage of a resin substrate by forming a thermal deformation suppressing film having a thermal expansion coefficient smaller than that of the resin substrate on the second surface of the resin substrate in the same radial range as that of the recording layer formed on the first surface of the resin substrate to thereby suppress the thermal deformation of the resin substrate. However, in the case of applying this method to a polycarbonate substrate being widely used for an optical disk, moisture is absorbed into the polycarbonate substrate from a position where the recording layer and the thermal deformation suppressing film are not formed.
The moisture once absorbed into the polycarbonate substrate is hard to expel to the atmosphere with the medium configuration that the substrate is closed by the recording layer and the thermal deformation suppressing film as moisture resistant materials. Accordingly, when a sudden rise in temperature occurs, the moisture is expelled to the boundary between the polycarbonate substrate and the recording layer. As a result, there is a possibility of corrosion of the recording layer. This problem is remarkable particularly in a substrate formed of polycarbonate resin or amorphous polyolefin resin having low birefringence and low saturated moisture absorbance as applied to an optical disk for high-density recording. The moisture absorbed or gas contained in such a resin is generated from the boundary between the recording layer and the resin substrate and the boundary between the thermal deformation suppressing film and the resin substrate by a sudden rise in ambient temperature. As a result, the recording layer and the thermal deformation suppressing film are separated from the resin substrate by the pressure of the moisture or gas generated, causing a semispherical dilation on the substrate, resulting in recording and reproducing errors. This phenomenon is due to the fact that the moisture absorbed in such a resin having low saturated moisture absorbance is hard to move therein, so that the moisture or gas is prone to be expelled to the nearest boundary.
There is another problem of loss in optical characteristics. That is, although the thermal deformation suppressing film is transparent, there is a power loss of the laser beam due to reflection or absorption because the thermal deformation suppressing film is formed on the incident surface for the laser beam. The power loss of the laser beam causes a reduction in the margin to high-speed recording and reproduction by high-speed rotation of the optical disk. To cope with the corrosion of the recording layer and the loss in optical characteristics, Japanese Patent Laid-open No. Hei 1-292639 discloses a medium configuration that a thermal deformation suppressing film is formed on the second surface of a resin substrate in the radial range from the innermost circumference of the substrate to a position corresponding to the inner periphery of a recording region of a recording layer formed on the first surface of the substrate in such a manner that the thermal deformation suppressing film does not overlap the recording region.
This medium configuration in the prior art will now be described more specifically with reference to FIG. 1. Reference numeral 2 generally denotes a recording medium. The recording medium 2 includes a transparent resin substrate 4 having first and second surfaces opposite to each other. A recording layer 6 is formed on the first surface of the resin substrate 4. The resin substrate 4 has a center hole 5. A thermal deformation suppressing film 8 is formed on the second surface of the resin substrate 4 in the radial range from the center hole 5 to a position corresponding to the inner periphery of a recording region of the recording layer 6. Accordingly, the thermal deformation suppressing film 8 does not overlap the recording region of the recording layer 6. With this configuration that the thermal deformation suppressing film 8 is formed radially inside of the recording region, the resin substrate 4 is not closed by the recording layer 6 and the thermal deformation suppressing film 8 at the recording region, thereby preventing the corrosion of the recording layer 6. Furthermore, since the thermal deformation suppressing film 8 is formed outside the incident region for a laser beam, there is no problem of optical loss.
However, in this configuration that the thermal deformation suppressing film 8 is formed so as to radially range from the center hole 5 to the inner periphery of the recording region of the recording layer 6, the thermal deformation suppressing film 8 comes into contact with a reference plane of a spindle 12 in an optical disk drive as shown by an arrow 14, causing separation of the thermal deformation suppressing film 8 from the substrate 4. As a result, dust is prone to generate and the flatness of a contact portion between the recording medium 2 and the reference plane of the spindle 12 is lost to result in difficulty of stable recording and reproducing operations. This problem of separation of the thermal deformation suppressing film 8 may be solved by coating an organic protective film so as to cover the thermal deformation suppressing film 8.
However, the contact portion between the thermal deformation suppressing film 8 and the reference plane of the spindle 12 is a ring-shaped region at the innermost circumference of the substrate, so that a high peripheral speed of the substrate cannot be obtained in using a rotary applicator for coating the organic protective film, and it is therefore difficult to coat the organic protective film with a uniform thickness. Further, there is a problem in durability of the thermal deformation suppressing film in the case that it is not coated with the organic protective film. For example, daily cleaning of the laser beam incident surface of the optical disk by a user is carried out by using a cleaning agent containing alcohol and a wiping cloth or soft paper in many cases.
If the adhesion of the thermal deformation suppressing film to the resin substrate is low, separation of the thermal deformation suppressing film by the work of wiping off the cleaning agent is prone to occur. To verify this fact, the adhesion of the thermal deformation suppressing film was evaluated by a wipe test. More specifically, an SiN film having a thickness of 165 nm as the thermal deformation suppressing film was formed on a polycarbonate substrate by sputtering to evaluate the adhesion of the SiN film by the wipe test. The wipe test was made by wiping the SiN film with a swab impregnated with ethanol until the SiN film was separated off. In this wipe test, a load of 100 g was applied to the swab and wiping speed was set to 500 mm/min. Thus, the above-mentioned disk cleaning work is replicated. As the result of this wipe test, the SiN film was separated off by five reciprocating stokes of the swab. This result shows the necessity of the organic protective film for the thermal deformation suppressing film.
There is another problem in coating the organic protective film. In forming the thermal deformation suppressing film, the deposition of projecting foreign matter in or on the thermal deformation suppressing film is unavoidable. In a conventional coating method for the organic protective film, a line defect due to the projecting foreign matter appears on the organic protective film. The line defect extends from the projecting foreign matter toward the outer circumference of the organic protective film.


This invention relates to a method of growing a nitride semiconductor layer by molecular beam epitaxy comprising the steps of: a) heating a GaN substrate (S) disposed in a growth chamber (10) to a substrate temperature of at least 850xc2x0 C.; and b) growing a nitride semiconductor layer on the GaN substrate by molecular beam epitaxy at a substrate temperature of at least 850xc2x0 C., ammonia gas being supplied to the growth chamber (10) during the growth of the nitride semiconductor layer; wherein the method comprises the further step of commencing the supply ammonia gas to the growth chamber during step (a), before the substrate temperature has reached 800xc2x0 C.

1. Field of the Invention
This invention relates to a molecular beam epitaxy (MBE) method for the epitaxial growth of Group III nitride semiconductor materials such as, for example, GaN or other members of the (Ga, Al, In)N material family.
2. Description of the Related Art
The epitaxial growth of Group III nitride semiconductor materials on a substrate can be effected by molecular beam epitaxy (MBE) or by chemical vapour deposition (CVD) which is sometimes known as Vapour Phase Epitaxy (VPE).
CVD (or VPE) takes place in an apparatus which is commonly at atmospheric pressure but sometimes at a slightly reduced pressure of typically about 10 kPa. Ammonia and the species providing one or more Group III elements to be used in epitaxial growth are supplied substantially parallel to the surface of a substrate upon which epitaxial growth is to take place, thus forming a boundary layer adjacent to and flowing across the substrate surface. It is in this gaseous boundary layer that decomposition to form nitrogen and the other elements to be epitaxially deposited takes place so that the epitaxial growth is driven by gas phase equilibria.
In contrast to CVD, MBE in carried out in a high vacuum environment. In the case of MBE as applied to the GaN system, an ultra-high vacuum (UHV) environment, typically around 1xc3x9710xe2x88x923 Pa, is used. Ammonia or another nitrogen precursor is supplied to the MBE chamber by means of a supply conduit and a species providing gallium and, possibly, indium and/or aluminium are supplied from appropriate sources within heated effusion cells fitted with controllable shutters to control the amounts of the species supplied into the MBE chamber during the epitaxial growth period. The shutter-control outlets from the effusion cells and the nitrogen supply conduit face the surface of the substrate upon which epitaxial growth is to take place. The ammonia and the species supplied from the effusion cells travel across the MBE chamber and reach the substrate where epitaxial growth takes place in a manner which is driven by the deposition kinetics.
At present, the majority of growth of high quality GaN layers is carried out using the metal-organic chemical vapour deposition (MOCVD) process. The MOCVD process allows good control of the growth of the nucleation layer and of the annealing of the nucleation layer. Furthermore, the MOCVD process allows growth to occur at a V/III ratio well in excess of 1000:1. The V/III ratio is the molar ratio of the group V element to the Group III element during the growth process. A high V/III ratio is preferable, since this allows a higher substrate temperature to be used which in turn leads to a higher quality GaN layer.
At present, growing high quality GaN layers by MBE is more difficult than growing such layers by MOCVD. The principal difficulty is in supplying sufficient nitrogen during the growth process; it is difficult to obtain a V/III ratio of 10:1 or greater. The two commonly used sources of nitrogen In the MBE growth of nitride layers are plasma excited molecular nitrogen or ammonia.
GaN has a lattice constant of around 0.45 nm. There is a lack of suitable substrates that, are lattice-matched to GaN, so GaN is generally grown onto either a sapphire substrate or a silicon carbide substrate. There is a large mis-match between the lattice constant of GaN and the lattice constant of sapphire or silicon carbide, and there is also a considerable difference in thermal properties, such as the thermal expansion coefficient, between the GaN layer and the substrate. It is therefore necessary to provide a thin initial nucleation layer on the substrate in order to grow a high quality GaN layer on sapphire or silicon carbide.
I. Akasaki and I. Amano report, in xe2x80x9cJapanese Journal of Applied Physicsxe2x80x9d Vol. 36, pp5393-5408 (1997), that a thin AlN layer, deposited at a low growth temperature, can be used as a nucleation layer to promote the growth of a GaN layer by metal organic chemical vapour deposition (MOCVD) process on a sapphire or silicon carbide substrate. U.S. Pat. No. 5,290,393 discloses the use of a GaN nucleation layer, again deposited at a low growth temperature, for promoting the growth of a GaN layer using MOCVD.
U.S. Pat. No. 5,385,862 discloses a further method of growing a single crystal GaN film on a sapphire substrate using MBE. In this method, a nucleation layer is grown on the substrate at a growth temperature of 400xc2x0 C. or lower. Furthermore, the V/III ratio of this method is very small, being less than 5:1, so that the subsequent GaN layer is restricted to a growth temperature of lower than 900xc2x0 C. GaN layers grown by this method have electron mobilities at room temperature of less than 100 cm2Vxe2x88x921sxe2x88x921.
Further prior art methods of growing GaN on a sapphire or silicon carbide substrate are reported by Z. Yang et al in xe2x80x9cApplied Physics Lettersxe2x80x9d Vol. 67, pp1686-1688 (1995), and by N. Grandjean et al in xe2x80x9cApplied Physics Lettersxe2x80x9d Vol. 71, p240-242 (1997). In both of these methods a GaN nucleation layer is initially grown on the substrate, after which the GaN layer is grown.
Although the provision of a nucleation layer does reduce the effect of the lattice and thermal mis-match between a GaN layer and a sapphire or silicon carbide substrate, the effects of the lattice and thermal mis-match are not eliminated completely. Moreover it is difficult and time-consuming to optimise the nucleation layer so as to obtain the highest possible quality GaN, and the step of growing the nucleation layer adds to the complexity of the growth process. It is accordingly desirable to use a GaN substrate for the growth of an epitaxial GaN layer.
A GaN substrate for use in the epitaxial growth of GaN can have two possible formsxe2x80x94a GaN substrate can be a xe2x80x9cfree-standingxe2x80x9d substrate or a xe2x80x9ctemplatexe2x80x9d substrate. A free-standing GaN substrate consists solely of GaN, and is formed by, for example, a GaN crystal. A template GaN substrate consists of a thick epitaxial layer of GaN grown on a base substrate of, for example, sapphire or silicon carbide. The thick epitaxial layer is grown on the base substrate by any suitable technique, such as metal-organic vapour phase epitaxy (MOVPE) or hydride vapour phase epitaxy (HVPE). Compared with the nucleation layers mentioned above, the epitaxial layer of a GaN template substrate is much thicker than a nucleation layer, for example having a thickness in the range 5 xcexcm-100 xcexcm.
M. Kamp et al report, in xe2x80x9cMat Res Soc Procxe2x80x9d, Vol. 449, p161 (1997), the growth of a GaN layer by MBE on a free-standing GaN substrate. They obtain good quality GaN, having a photoluminescence (PL) linewidth with a FWHM of 0.5 meV and a dislocation density in the range 102 to 103 cmxe2x88x922. However, Kamp et al achieve a growth temperature of only 750xc2x0 C.
WO 97/13891 discloses a method of epitaxial growth of a nitride semiconductor layer (GaN or Ga(Al,In)N) on a single crystal GaN or Ga(Al,In)N. This document is primarily directed to the way in which the substrate is produced, and teaches disposing a solution of Ga or Ga,Al,In in a heated nitrogen atmosphere so as to grow a bulk crystal of GaN or Ga(Al,In)N.
Once the bulk crystal has been grown, it is used as the substrate in an epitaxial growth process. The document speculates that it would be possible to grow an epitaxial layer on the substrate by MBE in the temperature range 500-900xc2x0 C. however, the document contains no teaching as to how an MBE growth temperature for GaN of 900xc2x0 C. could be achieved.
The growth of GaN on a GaN template substrate has been reported by, for example, W. C. Hughes et al in xe2x80x9cJ. Vac. Sci. Technol Bxe2x80x9d Vol. 13, p1571 (1995). In this report, GaN is grown by MBE with plasma excited molecular nitrogen used as the source of nitrogen for the MBE growth process. Other reports of the MBE growth of GaN on a GaN template substrate have been made by E. J., Tarsa et al in xe2x80x9cJournal of Applied-Physicsxe2x80x9d, Vol. 82, p5472 (1997); by H. Sakai et al in xe2x80x9cJapanese Journal of Applied Physicsxe2x80x9d, Vol. 34, L1429 (1995); by M. A. Sanchez-Garcia at al in xe2x80x9cPhys. Stat. Sol.(a)xe2x80x9d, Vol. 176, p447 (1999); by S. Kurai et al in xe2x80x9cPhys. Stat. Sol.(a)xe2x80x9d, Vol. 176, p459 (1999): and by A. Rinta-Moykky et al in xe2x80x9cPhys. Stat. Sol.(a)xe2x80x9d, Vol. 176, p465 (1999). In each of these reports, plasma excited molecular nitrogen was used as the source of nitrogen for the MBE growth process.
A first aspect of the present invention provides a method of growing a nitride semiconductor layer by molecular beam epitaxy (MBE) comprising the steps of: heating A GaN substrate disposed in a growth chamber to a substrate temperature of at least 850xc2x0 C.; and growing a nitride semiconductor layer on the GaN substrate by molecular beam epitaxy at a substrate temperature of at least 850xc2x0 C., ammonia gas being supplied to the growth chamber during the growth of the nitride semiconductor layer; wherein the method comprises the further step of commencing the supply ammonia gas to the growth chamber during step (a), before the substrate temperature reaches 800xc2x0 C. The present invention thus provides a method of growing a high quality layer of a nitride semiconductor by MBE. Commencing the supply of ammonia gas to the substrate during the step of heating the substrate, before the substrate temperature reached 800xc2x0 C., prevents thermal decomposition of the substrate (which would otherwise occur at substrate temperatures above 800xc2x0 C.). The substrate temperature during the growth of the nitride semiconductor layer may be in the range 850xc2x0 C. to 1050xc2x0 C.
The substrate temperature during the growth of the nitride semiconductor layer may be in the range 850xc2x0 C. to 1050xc2x0 C.
The method may comprise the further step of reducing the substrate temperature to a temperature below 800xc2x0 C. after the nitride semiconductor layer has been grown while maintaining the supply of ammonia gas to the growth chamber.
The method may comprise the further step of maintaining the substrate at a substrate temperature greater than 850xc2x0 C. for a predetermined time before growing the nitride semiconductor layer, ammonia gas being supplied to the growth chamber during the predetermined time. This allows the substrate to be out-gassed, thereby removing impurities from the substrate before the start of the growth process.
The substrate temperature may be maintained in the range 850xc2x0 C. to 1050xc2x0 C. during the predetermined time.
The predetermined time may be 30 minutes or less.
Ammonia gas may be supplied to the growth chamber during the entire duration of step (a).
The nitride semiconductor layer may be a GaN layer. The substrate may be a freestanding GaN substrate, or it may alternatively be a GaN template substrate. The use of a GaN substrate eliminates the lattice and thermal mis-match that occurs when, for example, a GaN layer is grown on a sapphire or silicon carbide substrate.
The method may comprise the further step of growing at least one (Al,Ga,In)N semiconductor layer on the nitride semiconductor layer. Thus, the present invention enables a high-quality (Al,Ga,In)N electronic or opto-electronic device to be manufactured.
A second aspect of the invention provides a nitride semiconductor layer grown by a method as defined above.
A third aspect of the present invention defines a semiconductor device comprising a nitride semiconductor layer as defined above.
Preferred embodiments of the present invention will now be described by way of an illustrative example with reference to the accompanying figures which:


A three-dimensional (3D) display panel has a plurality of rows and a plurality of columns, and each of the rows has at least one sub-row. The 3D display panel includes at least one first group and at least one second group arranged on the first row. The first group and the second group respectively have a first color region, a second color region and a third color region. The first color region and the second color region of the first group as well as the third color region and the first color region of the second group are arranged on one sub-row, while the third color region of the first group and the second color region of the second group are arranged on another sub-row.

Field of the Disclosure
The invention relates to a three-dimensional (3D) display panel and a driving method thereof.
Description of Related Art
At present, three-dimensional display technologies can be roughly categorized into auto-stereoscopic technologies that allow a viewer to directly watch images with naked eyes and stereoscopic technologies that require the viewer to wear specially designed glasses. According to the operational principle of an auto-stereoscopic display device, a fixed barrier is utilized to control images received by left and right eyes of the viewer. On account of visual characteristics of human eyes, when images with the same content but different parallax are respectively captured by the viewer's left and right eyes, the images that seem to be superposed may be perceived as a stereoscopic image. In general, cylindrical lenses are required to be configured on the display panel of the auto-stereoscopic display device, such that the right-eye and left-eye images displayed on the display panel can be respectively sent to the right and left eyes of the viewer.
To prevent the light corresponding to a left-eye signal from entering the right eye or prevent the light corresponding to a right-eye signal from entering the left eye, whether a light shielding region for blocking the entry of said light occupies a sufficient area in the auto-stereoscopic display should be taken into consideration, and thereby the crosstalk issue at a vertical viewing angle can be resolved to a better extent.

Three-dimensional display panel and driving method thereof


Provided are method and apparatus for maintaining an air interface inactive state. The method includes: receiving an RRC uplink notification message sent by a UE, the RRC uplink notification message carrying information notifying that the UE is out of coverage of a serving cell under a source secondary node; performing, based on the RRC uplink notification message, a migration operation of a related high-level configuration of a PDU session anchored to the source secondary node by the UE, a migration target node being a target secondary node or a current master node; and sending an RRC downlink reply message to the UE after performing the migration operation of the high-level configuration, and maintaining the UE in a dual-connectivity or single-connectivity air interface inactive state.

A 5G system supports single-connectivity (SC) and dual/multiple-connectivity (DC/MC) configuration and operation functions for user equipment (UE). In the SC mode, only one data transmission channel is provided for the UE over each of the air interface and the network-side. In the DC/MC mode, two or more data transmission channels are provided for the UE over each of the air interface and the network-side. For example, in the DC mode, two separate wireless connections (air interface data transmission channels) can be established and maintained between the UE and two NG-RAN base stations simultaneously over the air interface. One base station is referred to as the master base station (master node, MN) and the other base station is referred to as the secondary base station (secondary node, SN). Two separate network-side connections (network data transmission channels) can be established and maintained between the MN and a user-plane network element node UPF of the core network and between the SN and this UPF simultaneously over the NG interfaces. However, only the MN can establish an NG-C connection with a control-plane network element node AMF of the core network and maintain the NG-C connection. The related architecture is shown in FIG. 1. The UE in dual-connectivity configuration and operation can enter the RRC_INACTIVE state. The dual-connectivity operation combined with the RRC_INACTIVE state has the advantage that both the MN and the SN on the network-side can maintain their respective contexts for dual-connectivity communication configuration simultaneously, thereby avoiding the phenomenon where the network-side and the terminal UE fall back to single-connectivity configuration and operation and then may return to dual-connectivity operation through configuration. The related architecture is shown in FIG. 2.
The process for the UE and the network-side to enter and exit from the RRC_INACTIVE state without changing current serving MN and SN for the UE can be supported by a current standard protocol. However, when the UE moves away from the cell coverage of the current serving MN and SN, for example, when the MN performs handover or the SN changes, maintaining the UE in the RRC_INACTIVE state cannot be supported effectively by the current standard protocol.

Air interface inactive state maintaining method and device


The present invention discloses a power control method and apparatus. The power control method of the present invention includes: when a service runs in a first-standard communication system, determining a transmit power P1 of the first-standard communication system; determining that the transmit power P1 is higher than or equal to a threshold value P2 of power interference of the first-standard communication system to a second-standard communication system; use a power lower than P1 to send data on an interference frequency of the first-standard communication system. According to the power control method in the present invention, a signal transmit power of the interfering frequency of the first-standard communication system can be reduced when it is determined that the first-standard communication system will cause interference to the second-standard communication system, thereby reducing the interference of the first-standard communication system to the second-standard communication system.

With the development of mobile communications technologies, an existing 2nd generation (2nd Generation, 2G) communication network gradually evolves into a 3rd generation (3rd Generation, 3G) network and even to a 4G network. As the evolving process takes a long time, a situation where the 2G network, the 3G network and the 4G network coexist occurs.
In the prior art, to efficiently use spectrums of the 2G network, a 900 MHz spectrum of a global system for mobile communications (Global System for Mobile communications, GSM) network is reframed (Reframing) to be used in a universal mobile telecommunications system (Universal Mobile Telecommunications System, UMTS) network. To ensure normal running of the existing 2G network, the prior art proposes using a UMTS bandwidth lower than the standard spectrum bandwidth 5 MHz, for example, 4.2 MHz or 4.6 MHz, on the 900 MHz spectrum.
At present, in a situation where a low bandwidth is used, a protection bandwidth between frequencies of two different types of networks (for example, the GSM and the UMTS) is insufficient. In this case, signals of a first network (for example, the GSM) may cause high interference to a second network (for example, the UMTS).

Power control method, apparatus and system


Towing adjustment and coupling techniques may include a retentive lateral trailer adjustment device of a trailer (1) configured to provide lateral adjustment of the trailer (1). In some embodiments, a trailer (1) may include a coupler element (3) and at least one retentive lateral adjustment device configured to provide adjustment in a lateral direction (8) of the coupler element (3). Embodiments may have configurations directed to couplers such as a gooseneck hitch, a fifthwheel hitch, and a pull-type or tongue hitch. Embodiments may also provide a fore-aft position indicator (44) with or without a fore-aft position sensor (50) through which proper positioning of a source of tow power (54) relative to a trailer (1) may be facilitated in a fore-aft direction (7). Corresponding methods are included as embodiments of the invention.

Traditional towing technologies have incorporated various types of coupling devices, which may traditionally be referred to as a hitch or hitches, for the coupling of a trailer to a source of towing power. Hitches may generally be considered implements in a broad field potentially including a coupling portion associated with a source of towing power and a coupling portion associated with the trailer to be towed. A hitch configuration may be generally considered as having portions that are associated with the "tow-side" and portions that are associated with a "towed-side".
Hitch technology can include various hitch configurations, and may include gooseneck configurations, fifth wheel configurations, bumper pull or tongue configurations, pintle configurations, as well as other hitch configurations. The hitch may have one or more couple portions such as one or more receivers, inserts, pins, balls, rings, hooks, bars, tubes, bumpers, plates, plugs, tongues, or other such couplings. In order to affect a coupling of the portions of the hitch, each portion of the hitch may need to be aligned so that a coupling may be established. The task of coupling the couple portions of a hitch, and the alignment of such portions, is traditionally accomplished in some fashion by adjusting the position of one or both of the couple portions. The task of adjusting couple portions of hitches, however, may not have been conventionally facilitated for the various hitch configurations. As but one example, a traditional pull-type trailer may have a tongue hitch portion or a bumper or receiver portion at the towed-side and a ball hitch portion at the tow-side. These may require alignment of the tongue or coupler element and the ball to establish the coupling. Other hitch configurations and trailer types, can also require alignment of coupling portions to establish the coupling and allow towing.
In a typical hitch coupling process, the source of tow power may be initially positioned in a fore-aft direction to bring the tow-side hitch portion and the tow-side couple portion (such as a ball) within an acceptable distance of the towed-side hitch portion and the towed-side couple portion (such as a tongue). An initial tow-side adjustment may involve a rough alignment in a lateral direction (a direction roughly perpendicular to the typical direction of towing). The relative positions of the ball and tongue and the vertical distance between the hitch portions may be potentially considered as part of the initial tow-side adjustment. To establish the coupling, an adjustment of the towed-side hitch portion may follow the initial positioning of the source of tow power. This may even be followed by subsequent steps of attempted adjustment from the tow-side until an acceptable alignment of the tow-side and towed-side hitch portions is achieved and hitch coupling is established. This adjustment process can apply to each of the various hitch and trailer configurations, such as gooseneck, fifth wheel, bumper/receiver, A-frame types (including but not limited to industry standard class I, II, III, IV and V configurations), coupler-ball, and pintle configurations as may be used for various trailer body types, including but not limited to: camper bodies, van bodies, horse trailer bodies, flat beds, agricultural use bodies, car haulers, and all other commercial and recreational bodies.
As mentioned, after achieving a first gross adjustment or perhaps an initial positioning of the tow-side (which in some instances can involve several adjustments of the source of tow power), a second adjustment is often made to the towed-side hitch portion. In some hitch configurations, the towed-side hitch portion, and potentially the trailer itself, may be physically forced by one or more individuals to provide lateral and/or vertical adjustment of the towed-side hitch portion. Often this only works on hard, smooth, flat, and fairly level surfaces. The individuals may also interpose themselves between the source of tow power and the trailer during these adjustments, creating a potentially dangerous situation. In some hitch applications, a vertical jack may be provided for vertical adjustment of the towed-side hitch portion. Sometimes, the individuals involved may provide visual or audible guidance to an individual controlling the source of tow power during the adjustment from the tow-side. Again, this sometimes-difficult process can create a dangerous situation.
In some hitch configurations, positioning of the tow-side hitch portion is only approximate in that additional lateral and vertical adjustment may be required of either or both the tow-side and the towed-side hitch portions to achieve coupling. The additional lateral and vertical adjustment of the tow-side and the towed-side hitch portions of conventional technologies may be a time-consuming and inconvenient. Individuals controlling the source of tow power may be inexperienced, delays can occur, and risks can be created. Some trailers may be simply too heavy for manual lifting and lateral adjustment by individuals, potentially resulting in a failure to initially couple the hitch portions and possibly creating further risks or strains to individuals. Environmental factors can also affect the hitch coupling process. Terrain conditions can affect the positioning of the source of tow power during the coupling process. Sometimes, after an adjustment of the source of tow power has been made the source of tow power, such as a truck or other vehicle, may adjust under its own weight, a result potentially due to mud, snow, mechanical, or other conditions. Wind or unintended forces applied to the vehicle could also cause the vehicle to move from an adjusted position.
In all of the foregoing, the conventional technologies can suffer from various drawbacks. Some hitch and trailer configurations may provide a wheel at or near the towed-side hitch portion to allow lateral adjustment of such portion. Even with this type of an arrangement, drawbacks such as accuracy, time to achieving hitch coupling, and dangers and strains to individuals during the adjustment process can remain. This wheel-type technology can also suffer unintended adjustment. This type of unintended adjustment may even be generated by an unintended movement of the trailer, such as movement created by external forces corresponding to wind or an errant force applied by an individual or vehicle, or even as a result of lower frictional forces and the weight of the trailer. Forces may be generated by potential energy, tensions or elastic movements of wheels, axles, or other portions of the trailer, and may further manifest themselves as torque applied to or from portions of the trailer after or during such a process. The wheel-type technology may also not optimally maintain the intended position of the towed-side hitch portion or the intended trailer position, under some conditions and may require additional adjustments of one or both of the tow-side and towed-side hitch portions. These conditions may also exist during vertical adjustment of the towed-side hitch portion, and lateral positioning may not be maintained during vertical adjustment of the towed-side hitch portion. Wheel-type technology may also be difficult to use for heavy trailers and it is not usually even available for heavier commercial flat bed, pintle-type trailers or for gooseneck or fifth wheel-type trailers in either a commercial or a recreational context.
Other systems have attempted to address positioning as well. These technologies may include one or more plates or other elements that are laid upon the ground surface and upon which a wheel or other support element of the trailer rests. Some of the existing technologies can still require physical adjustment such as pushing, pulling, or lifting the towed-side hitch portion. They can also need to be stored for use when hitch coupling is established, potentially creating additional inconvenience. Plates can need to be placed underneath supporting elements of the trailer, adding further complication and steps to the hitch coupling process. Existing systems may even lack refined adjustment capability. Some existing systems have attempted to address lateral adjustment of one or more hitch portions during the coupling process. V-pan or guidance elements may lack the ability to maintain or be responsive to positioning of the tow-side and towed-side hitch portions, especially if unintended movement of the towed-side hitch portion or trailer occurs as described above. They may lack full adjustment capabilities and can still require multiple steps for adequate alignment, perhaps two actions at once such as the act of pushing or pulling the trailer laterally while simultaneously lowering the trailer onto the ball. Some systems may be associated with the source of tow power, thereby potentially reducing the availability of certain sources of tow power or requiring removal and/or reconfiguration of the source of tow power.


A voltage controlled emitter-coupled multivibrator in which a frequency range of an oscillating signal and a frequency within the frequency range can be adjusted. An emitter-coupled multivibrator is provided with an emitter follower buffer having first and second transistors, a gain stage having third and fourth transistors which are cross-coupled through the first and second transistors, and a current source connected to emitters of the third and the fourth transistors, and generates first and second oscillating frequency signals. An outputting section compares a first voltage level of the first oscillating signal with a second voltage level of the second oscillating signal and outputs a compared signal having a predetermined voltage level. A controlling section outputs a controlling current which controls an amount of a current which flows through the current source of the emitter-coupled multivibrator. The oscillating frequency and the oscillating frequency range can be adjusted by inputting two controlling voltages via the controlling section. Therefore, the oscillating signal which has a wide range of frequencies from a low frequency to a high frequency can be obtained.

1. Field of the Invention
The present invention relates to a voltage controlled emitter-coupled multivibrator, and more particularly to a voltage controlled emitter-coupled multivibrator which can determine an oscillating frequency range and adjust the height of a frequency within the determined frequency range.
2. Description of the Prior Art
A voltage controlled oscillator is utilized in a phase locked loop (PLL) or a frequency combining apparatus, and particularly in the PLL for identifying the frequency of an outputting signal with a predetermined frequency. An example of the voltage controlled oscillator used in the PLL is disclosed in U.S. Pat. No. 4,749,961 (issued to Kato et al., on Jun. 7, 1988). Most voltage controlled oscillators make an oscillation by charging or discharging a capacitor through switching the amount of current controlled by an inputting voltage. The EC multivibrator is one of a relaxation oscillator using symmetric charging and discharging with respect to a timing capacitor connected between emitters of a differential gain stage.
FIG. 1 is a block diagram illustrating the constitution of the conventional EC multivibrator voltage controlled oscillator 10. In the conventional EC multivibrator voltage controlled oscillator 10, a gain stage 11 is comprised of a pair of first and second transistors Q1 and Q2. First and second transistors Q1 and Q2 are cross coupled through an emitter-follower buffer stage 12. First and second transistors Q1 and Q2 of gain stage 11 have equal load resistors R1 and R2 with clamping diodes D1 and D2, and are clamped to IV.sub.BE (=0.7) by clamping diodes D1 and D2. The emitters of first and second transistors Q1 and Q2 are biased by current sources I.sub.1 and are coupled through a timing capacitor C.sub.1.
The operation of the conventional EC multivibrator voltage controlled oscillator 10 having the above described constitution, will be explained.
Since first and second transistors Q1 and Q2 of gain stage 11 are combined by first and second transistors Q3 and Q4 of emitter follower buffer stage 12, either first or second transistor Q1 or Q2 (but not both) is on at any one time. In this manner, timing capacitor C.sub.1 is alternately charged with equal but opposite currents.
First, assuming for the moment that first transistor Q1 is off and second transistor Q2 is on, at the emitter of second transistor Q2 a total current of 2I flows, where one-half of the current is forced through timing capacitor C.sub.1. At this time, V.sub.B4 =V.sub.CC -V.sub.BE (FIG. 2A), V.sub.E4 =V.sub.B1 =V.sub.CC -V.sub.BE (FIG. 2D), and V.sub.B3 =V.sub.CC (FIG. 2B) when ignoring the base current of first transistor Q3, V.sub.E3 =V.sub.B2 =V.sub.CC -V.sub.BE (FIG. 2C) and V.sub.E2 =V.sub.CC -V.sub.BE (FIG. 2E).
Since first transistor Q1 is off, the current I charging timing capacitor C.sub.1 is obtained from the emitter of second transistor Q2. This current I causes the voltage level V.sub.E1 at the emitter of first transistor Q1 to decline at a constant slope of I/C.sub.1 until the voltage level at the emitter of first transistor Q1 becomes equal to V.sub.CC -3V.sub.BE, as illustrated in FIG. 2F. At this time, first transistor Q1 is on.
When first transistor Q1 is on, first diode D1 is on, V.sub.B3 =V.sub.CC -V.sub.BE (FIG. 2B), and V.sub.E3 =V.sub.B2 =V.sub.CC -2V.sub.BE (FIG. 2C) and second transistor Q2 is off. When second transistor Q2 is off, V.sub.B4 =V.sub.CC (FIG. 2A), V.sub.E4 =V.sub.B1 =V.sub.CC -V.sub.BE (FIG. 2D) and V.sub.E1 =V.sub.CC -2V.sub.BE (FIG. 2F). At this time, timing capacitor C.sub.1 discharges in the opposite direction with constant current I through second transistor Q2. When V.sub.E1 =V.sub.CC -3V.sub.BE (FIG. 2F), the oscillator is changed into its prior state to oscillate a constant frequency signal (V.sub.E2 -V.sub.E1 in FIG. 2G) through the operation.
However, in the above-mentioned conventional EC multivibrator voltage controlled oscillator, the oscillating frequency range cannot be established and the oscillating frequency cannot be adjusted.

Voltage controlled emitter-coupled multivibrator


A multibeam semiconductor laser array including n pieces of mutually independently drivable semiconductor laser elements which are arranged with a distance r between the elements in such a manner that light leaving centers of respective laser beams emitted from the semiconductor laser elements are aligned on a straight line. In the multibeam semiconductor laser array, the distance r is determined according to the following equation when a light emitting wave length of each of the semiconductor laser elements is expressed as .lambda. and a divergence angle of the laser beam in a direction of the straight line is expressed as .theta..sub.1 : ##EQU1## where n is an integer equal to or more than 2, .pi. is a circle ratio, I is an interlacing period which is a natural number mutually prime to n, and k is a spot diameter correction coefficient which is a real number in the range of 1.4 .ltoreq.k.ltoreq.1.8.

1. Field of the Invention
The present invention relates to a laser beam light source used to write an image by means of light beams in a digital copying machine, a laser beam printer and the like and, in particular, to a multibeam semiconductor laser array serving as a light source which is able to perform simultaneous image writing by a plurality of laser beams and a multibeam laser printer which is constructed by use of such a multibeam semiconductor laser array.
2. Description of the Related Art
In a laser beam printer, a laser beam from a semiconductor laser is irradiated on a rotary polyhedral mirror called a polygon scanner, and the beam reflected from the rotary polyhedral mirror is then irradiated on the surface of a charged photoreceptor which is moving at a constant speed. Rotation of the rotary polyhedral mirror causes the laser beam to scan in a direction perpendicular to the moving direction of the photoreceptor. Since the laser beam is modulated according to the image to be output, there is formed an electrostatic latent image on the photoreceptor and the electrostatic latent image is developed to provide a visible toner image.
However, in the above-mentioned laser beam printer, distances between the scanning lines of the laser beam must be set narrow enough in order to enhance the fineness of an output image. Also, in order to output the image at a high speed, the scanning speed must be increased. The most important problem in improving the image fineness and speed of the laser beam printer is that the rotatory speed of the polygon scanner is limited.
In order to solve the above-mentioned problem, a multibeam scanning system which scans on an image plane at the same time by means of a plurality of laser beams is already known. In this multibeam scanning system, of course, a plurality of laser beam spots must be sufficiently near to each other in a direction (which will be hereinafter referred to as a subsidiary scanning direction) perpendicular to a direction of scanning (which will be hereinafter referred to as a main scanning direction) by a polygon scanner. For this purpose, efforts have been made to manufacture a plurality of semiconductor lasers such that they are near to each other. At present, a semiconductor laser array is made on an experimental basis in which the semiconductor lasers are closely spaced down to a distance of 10 .mu.m (see, for example, Japanese Patent Unexamined Publication No. Hei. 2-39583, R. L. Thornton et al., "Properties of closely spaced independently addressable lasers fabricated by impurity-induced disordering", Appl. Phys. Lett. 56(17), 1623-1625 (1990) and the like).
However, even if the plurality of semiconductor lasers are closely spaced around 10 .mu.m by employing the techniques respectively disclosed in the above-mentioned Japanese Patent Unexamined Publication and the like, such distance is not sufficient to scan leaving no spaces in the subsidiary scanning direction. As means for making up for such insufficiency, there has been proposed a method which can scan the above-mentioned unscanned spaces in the subsidiary scanning direction by means of interlaced scanning (see Japanese Patent Examined Publication No. Hei. 1-45065). Also, there has been proposed a multibeam scanning optical system using a semiconductor laser array including a plurality of semiconductor lasers spaced 10 .mu.m from each other.
In FIG. 1, an example of interlaced scanning is shown. In this example, interlaced scanning is carried out by two laser beams L1 and L2. In FIG. 1, d.sub.x designates a laser spot diameter to be defined electrophotographically (which is hereinafter referred to as an electrophotographic spot diameter). The electrophotographic spot diameter is not a optically defined laser spot diameter existing on an image plane A1, but it means a diameter of a spot occurring when an electrostatic latent image formed on the image plane A1 by a laser is developed. A distance r.sub.3 between the centers of two spots B1 and B2 formed on the image plane A1 by the two laser beams L1 and L2 is 3d.sub.x.
Since subsidiary scanning is performed by 2d.sub.x in each main scanning, as shown in FIG. 1, in the first scanning a second scanning line is scanned by the laser beam L2, and in the second scanning a first scanning line is scanned by the laser beam L1 and a fourth scanning line is scanned by the laser beam L2. In this manner, the following scanning lines are scanned sequentially without leaving any scanning lines between them. In other words, although some of scanning lines are left unscanned in each scanning, the line scanned in a certain scanning time is jumped in the next scanning time, so that all of the scanning lines are scanned with no lines left unscanned in the long run.
In order to prevent duplicate scanning and to prevent occurrence of unscanned lines in the interlaced scanning, the following three conditions must be satisfied:
1) The subsidiary scanning must be executed by nd.sub.x with respect to the number of laser beams n in one main scanning.
2) The distance r.sub.3 between the two laser beams on the image plane must be an integral multiple of the electrophotographic spot diameter d.sub.x.
3) When an integer obtained by dividing the spot center distance r.sub.3 by the spot diameter d.sub.x is called an interlacing period I, the interlacing period I must be mutually prime to the number of laser beams n (the greatest common measure between them is 1).
Further, the smallest distance between the scanning lines is referred to as a scanning line pitch which is designated by p in FIG. 1. In general, p=d.sub.x. The spot diameter of the laser beam is generally defined by a diameter which allows the light amplitude to be 1/e (1/e.sup.2 in power) of that of the spot center. The thus defined spot diameter is hereinafter referred to as an optical spot diameter and is designated by d.sub.o.
In the laser beam printer, an image is formed according to an electrophotographic process. However, when the image obtained according to the electrophotographic process is examined, it is preferred to define a spot diameter which is different from the above-mentioned optical spot diameter. That is, a spot diameter of an image finally obtained when a laser beam having a certain light intensity distribution is used is defined as the electrophotographic spot diameter d.sub.x of the laser beam.
In FIG. 2, there is shown a relationship between the optical spot diameter and the electrophotographic spot diameter. In this figure, the light amplitude on the main light ray of the laser beam is normalized to 1. While the optical spot diameter d.sub.o is a diameter in which the light amplitude is 1/e (1/e.sup.2 in power) of that of the spot center, the electrophotographic spot diameter d.sub.x is a diameter in which the light amplitude is x times of that of the spot center (x.apprxeq.0.7, when converted to a power ratio, approximately 0.5) (see "Examination on Tone Reproduction in Laser Xerography" proposed by Tanaka, the 6th Color Engineering conference, p. 77-p. 80 (1989)) Here, a ratio of the optical spot diameter d.sub.o to the electrophotographic spot diameter d.sub.x is referred to as a spot diameter correction coefficient k, and k is defined as follows: EQU k=d.sub.o /d.sub.x
The value of k varies according to the processes of electrophotography used. In a process of reversal development in which a toner is attached to a light exposed area, 1.4.ltoreq.k.ltoreq.1.6 is desirable. On the other hand, in a process of forward development in which the toner is attached to a light exposed area, 1.5.ltoreq.k.ltoreq.1.8 is desirable.
The laser beam printer basically employs an image forming method based on the electrophotographic process and, of course, a light source used in the laser beam printer must be able to allow a photoreceptor for electrophotography to emit a wave length having a practical sensitivity. In recent years, compact disc players have been mass produced so that the costs of AlGaAs semiconductor lasers having a light emitting wave length of 0.78 .mu.m used in the compact disc players have been reduced. Due to this, the development of photoreceptors for electrophotography in conformity with the above light emitting wave length has been advanced and at present photoreceptors having sufficient performance are being practically used. Partly because a photoreceptor having a sensitivity to a light with a long wave length is generally apt to be unreliable, at present, it can well be said that there exist almost no photoreceptors which have a practical sensitivity to the light having a wave length longer than 0.78 .mu.m. From this point of view, it can be said that a semiconductor laser used in the laser beam printer should be able to emit a light having a wave length shorter than approximately 0.8 .mu.m. Practically, it is desired to emit a light having a further shorter wave length and thus an AlGaInP semiconductor laser which is able to emit a light with a wave length of the order of 0.68 .mu.m is more suited for the laser beam printer.
In the semiconductor laser array to be used in the above-mentioned applications, however, a plurality of semiconductor laser elements are disposed very closely to each other and, therefore, it is difficult to arrange collimators individually with respect to each semiconductor laser element. From this point of view, every laser beam light must be focused on an image plane with the same optical system. Using the optical configuration, however, it is almost impossible to independently change a spot diameter and a spot distance on the surface to be scanned. This makes it critical for optical conditions to be set in such a manner that a proper interlaced scanning can be performed.
Also, it seems that, according to the above-mentioned interlaced scanning, even if the image forming spot distance is set to be wide on the image plane, no problem arises provided that a proper interlacing period is selected. However, in fact, if the image spot distance is set to be wide and a great interlacing period (which is hereinafter referred to as an interlacing period of higher order) is employed, then very high mechanical precision is required of a scanning device. Description will be given below of reasons for such very high mechanical precision:
As shown in FIG. 3 (a), when the image plane is scanned by a spot B, that is, when the number of semiconductor laser elements n=1 and the interlacing period I=1, if it is assumed that a scan pitch p must be within a certain error .DELTA.p, then a tolerance .delta..sub.o of a speed in the subsidiary scanning direction can be expressed by the following equation: EQU .delta..sub.o =.DELTA.v/v=.DELTA.p/p
where v and .DELTA.v denote the subsidiary scanning speed and the error of v, respectively.
FIG. 3 (b) shows a case in which the number of semiconductor laser elements n=3 and the interlacing period I=2. Assuming that a tolerance of the speed is .delta..sub.n,I when the number of semiconductor laser elements is expressed as n and the interlacing period is expressed as I, then the tolerance of the speed in this case, .delta..sub.3,2 =.DELTA.p/3p=.delta..sub.o /3. Accordingly, the tolerance of the speed is reduced to 1/3 when compared with that obtained in the case of FIG. 3 (a).
As shown in FIG. 3 (c), when the number of semiconductor laser elements n=4 and the interlacing period I=5, then there is obtained the tolerance .delta..sub.4,5 =.DELTA.p/16p=.delta..sub.o /16. This means that the required a precision increases more than one decade compared with the case shown in FIG. 3 (a).
In the above discussion, description has been given of the tolerance of the speed in the subsidiary scanning direction. Besides the tolerance of the speed in the subsidiary scanning direction, similar problems occur in the accuracy of the optical system and the dimensional accuracy of the semiconductor laser array. In addition, when the image forming spot distance is set to be wide and a high order interlacing period is employed, then the required number high speed memories, which are expensive, to control the interlaced scanning are increased.

Multibeam semiconductor laser array and multibeam laser printer


A luminaire comprising lamellae holding means, a light source, and a set of lamellae comprising a plurality of (inclined) lamellae. The set of lamellae extends at least partially over a light emission window. The lamellae have a reflective front surface facing towards the light source, said front surface being designed to partially reflect light to the exterior and partially transmit light, for example in that the lamellae are diffusely translucent or have a perforated surface. The set of lamellae is provided with light converging means, for example a Fresnel lens, which optionally are integrated in the lamellae to prevent the luminaire becoming too bulky.

Such a luminaire is known from KR2009083546. The known luminaire has a high-brightness LED illumination module as the light source to obtain uniform luminance of the plurality of reflecting lamellae. The lamellae holding means is embodied as a concave reflector for gathering the light and is installed in the longitudinal direction as an inner side of a housing. The lamellae are provided in a row in an inclined orientation alongside a longitudinal direction of the luminaire inside a space enclosed by the housing. Especially for luminaries having high brightness light sources, said uniform luminance is difficult to obtain. In the known luminaire said uniform luminance is obtained by an increased size of each lamella more remote from the light source, thus enabling each lamella to intercept part of the light of the diverging light beam that has passed lamellae closer to the light source. A first part of the light emitted by the light source impinges on the reflective surface of the adjacent lamella and is reflected to the exterior through the light emission window. A second part of the light emitted by the light source propagates alongside said adjacent lamella and partially impinges on the next lamella and partially propagates to yet another lamella. It is a disadvantage of the known luminaire that the lamellae are mutually different, as their dimensions increase with increasing distance from the light source lamellae. This has the disadvantage that the luminaire is relatively expensive because relatively much material is required for its construction and because the lamellae have no (same) standard size. It is another disadvantage of the known luminaire that it is relatively bulky, resulting in the additional disadvantage that the known luminaire is relatively difficult to build into false ceilings where only relatively little space is available.


A system for obtaining collective decisions from multiple control sources. The system is able to produce a single command from these control sources. Each control source corresponds to a behavior and each responds to inputs to produce a command. The system employs a piece-wise constant preference profile composed of zones, spikes, and clamps which compress the amount of the amount of data required to process behavior preferences. The system sorts commands according to command values in a chart to produce a total profile which represents the combination of profiles of the command values for multiple behaviors. The peak zone in the total profile is then used to produce a desired response to the multiple commands. The system allows behaviors to be combined through command fusion rather than subsumption. The piece-wise constant representation allows behavior commands to be combined after they have been passed through a standard control system. This permits behaviors to use any derivative of the control source's variable that is appropriate for their function. The system has a bounded arbitration time so that control loop stability will not be disrupted by the arbitration process. The system also incorporates a method for smoothing behavior switching transients.

1. Technical Field
This invention relates to control systems, and more particularly to systems for representing and combining multiple concurrent control commands to produce coherent action.
2. Discussion
Sensor based intelligent real-time control systems are used in a variety of applications. These include autonomous, air, land, and underwater vehicles. Also such control systems are found in sensor steering, missile guidance, vehicle actuator control systems and process control systems. The central task of such control systems is to combine a variety of sensory inputs to obtain a reasonable control decision.
There is an emerging class of control systems, sometimes called fuzzy controllers, or behavior-based control systems in which control actions are computed from the collective votes of many independent control procedures or rules. These procedures or rules are sometimes referred to as behaviors. For example, in a vehicle control system, one behavior may perform obstacle avoidance, and another behavior may perform target tracking. While both behaviors may issue commands for turning the vehicle, these commands may or may not agree. Thus, it is necessary for a control architecture to represent and combine the behavior commands in such a way that a single action may be discerned from the collective preferences of multiple behaviors.
Many techniques have been developed for the purpose of combining commands from multiple, simple, control laws or decision rules. One technique is called the subsumption architecture. See Brooks, R. A., "A Layered Intelligent Control System for a Mobile Robot," in ISSR; Third International Symposium of Robotics Research, Gouvieux, France, October, 1985.
In the subsumption architecture, simple finite-state machines can inhibit or subsume the output of others. This provides a means to incrementally assemble a complex real-time control system from many simple behaviors. However, the combination scheme used in subsumption does not allow behaviors to express preferences and does not provide a means to combine alternative concerns from different behaviors.
Later work in behavior-based control allowed behaviors to place commands in an array, and other behaviors could alter these commands if they had suitable priority. See Payton, D. W., "An Architecture for Reflexive Autonomous Vehicle Control," in IEEE International Conference on Robotics and Automation, San Francisco, Calif., April 7-10, 1986, pp. 1838-1845. In this system, each command could be assigned a unique function that would define how new commands would be combined with the existing array entry. A behavior could thus overwrite a previous command, yielding the same effect as in subsumption. Alternatively, the array entry could be updated with the average, the maximum, or the minimum of the new command and the current entry value. Still, this technique did not allow for the combination of preferences from behaviors.
Later, a technique was developed that allowed the combination of discrete preferences from behaviors. See Rosenblatt, J. K. and Payton, D. W., "A Fine-grained Alterative to the Subsumption Architecture for Mobile Robot Control," in International Joint Conference on Neural Networks, Washington, D.C., June 1989, pp. 317-324.
This technique quantizes steering commands into discrete values. Behaviors vote on their preference for each command choice. By summing up the preferences from all behaviors for each choice, the one choice with maximum preference will prevail. However, the discrete representation of this approach has a fundamental limitation when applied to control systems. All behavior commands must be expressed in terms of the same derivative of the selected control variable. Thus, commands from a behavior that controls heading cannot easily be combined with commands from another behavior that controls turn rate. Both behaviors must be constrained to using the same control derivative in order for their commands to be combined. This can often make the design of individual behaviors awkward and difficult. The discrete representation also imposes limits on the resolution of control commands. If a given set of control command values is available for voting by the behaviors, then command values that lie between those that are given are not easily attained.
Another approach to combination of commands from multiple behaviors is discussed in the article by R. Arkin, "Motor Schema Based Navigation for a Mobile Robot: An Approach to Programming by Behavior," in IEEE Conf. on Robotics and Automation, March, 1987, pp. 264-271. Unlike the approach used in subsumption, each behavior in Arkin's approach provides a command vector that represents a desired heading and velocity. Arkin sums these vectors to yield a final command vector that presumably will satisfy the needs of the contributing behaviors. However, the result of summing vectors is entirely different from the result of finding the maximum preference. If a vector to go left is summed with a vector to go right, the result will be a vector to go straight ahead. This could end up conflicting with the desires of both behaviors.
Another area of related research is that of fuzzy logic as applied to control systems. See Lee, C. C., "Fuzzy Logic in Control Systems: Fuzzy Logic Controller-Part I," IEEE Systems, Man and Cybernetics, 20(2), 1990, pp. 404-418; and Lee, C. C., "Fuzzy Logic in Control Systems: Fuzzy Logic Controller, Part II," IEEE Systems, Man, and Cybernetics 20(2), 1990, pp. 419-435. In fuzzy controllers, commands are represented in terms of a range of preferences for a set of discrete command values. Special combination rules are used to combine the preferences from different control rules. Once these preferences have been combined, a process called "defuzzification" is employed. This process extracts a single command from the range of command preferences. Several defuzzification methods exist. The most common method is the "center of area" method. This method generates a command at the center of gravity of the preference distribution. This method can generate commands that are between the discrete preference values, but it has the disadvantage of possibly generating commands that lie at the lowest point of a preference distribution if that point is between two peaks of a bi-modal distribution.
Another method known as the "max criterion" method selects the command with the highest overall preference. This entire process is performed upon a set of discrete command choices. The use of discrete choices resembles the use of discrete preferences in the methods described above in the Payton et al. and Rosenblatt et al. articles discussed above. However, fuzzy controllers do not allow both positive and negative preferences to be expressed by behaviors. This is important because negative preferences allows the establishment of disjoint control options. For example, a vehicle may be commanded to go either left or right, while that it may not go straight ahead. Also, fuzzy logic does not permit the combination of behavior commands that have been expressed in terms of different derivatives of a given control variable.
Accordingly, it would be desirable to provide a system for combining commands from multiple simple control laws or decision rules which allows behaviors to express preferences, and also allows the combination of concerns from different behaviors. It would also be desirable to provide a technique for allowing a combination of preferences from behaviors. It would further be desirable to provide a system which is not constrained to using the same control derivative in order for commands to be combined, but instead which permits the combination of behavior commands that have been expressed in terms of different derivatives of a given control variable. Further, it would be desirable to provide such a system in which, if a preference to go left is summed with the preference to go right, the dominant preference will still be either to go left of right and not to go straight ahead. Also, it would be desirable to provide a control system having the above characteristics which allows both positive and negative preferences to be expressed by behaviors.

System and method for processing commands from a plurality of control sources


A node for a communications network has a converter for digitizing at a receiver clock rate a received optical signal received over an optical link from an optical transmitter at a source node, a framer for detecting frames and a forward error correction part for correcting errors in the payload of the frame. An error rate in the received payload part is monitored and a processor sends, according to the monitored error rate, a request to the optical transmitter to adapt a length of the transmitted forward error correction part and to adapt a clock rate of the transmission of the frame if FEC length is reduced or FEC is disabled. This can enable power saving, when less FEC information is being sent.

Communications networks such as optical networks often employ error correction. Such optical networks typically use wavelength division multiplexing (WDM) or dense wavelength division multiplexing (DWDM) to increase transmission capacity. In WDM and DWDM networks, a number of optical channels are carried in each fiber at disparate wavelengths. Network capacity is based on the number of wavelengths, or channels, in each fiber and the bandwidth, or size of the channels. In WDM, DWDM and other optical networks, arrayed waveguide gratings (AWGs), interleavers, and/or fibergratings (FGs) can be used to add and drop traffic at network nodes and to multiplex and demultiplex traffic at network nodes. To enable reconfiguring the wavelength paths to be dropped or added at different nodes, network nodes having optical switches can be provided, known as all optical ROADM (Reconfigurable Optical Add Drop Multiplexer) nodes.
It has been appreciated that DWDM does not provide its own overhead for management nor protection schemes to recover from equipment failures. DWDM involves more network elements than earlier point to point optical links. Such elements, such as-optical amplifiers, multiplexers, and demultiplexers—and dispersion compensation units, can bring reliability concerns and warrant monitoring. As a result, the G.709 Optical Transport Network, or OTN standard was generated by the International Telecommunication Union Telecommunication Standardization (ITU-T) to provide management functionality for DWDM optical networks. OTN involves adding a frame of overhead information, (also called a digital wrapper), some to the front of the signal as a header, and some such as FEC (Forward Error Correction) as a trailer appended to the rear. The FEC can extend optical span distances by reducing bit error rates (BERs).
FEC is one of the most attractive features provided by G.709 Hierarchy. It allows the receiver to detect and correct errors and therefore permits the transmission of data along "disturbed" paths or to reach a longer distance than an equivalent signal without this feature. Therefore the FEC can improve the quality of the transmission but its deployment has a cost.

Communications network using adaptable FEC