A hydraulic coupling for use in undersea drilling and production operations is disclosed, having a male member with radially extending projections or fins configured to be received in a female member having corresponding grooves in its receiving chamber. Relative rotation of the members urges the male member inwardly and preferably compresses axially a metal seal between the leading face of the male member and an internal shoulder. This preloads the seal before the coupling is pressured up with hydraulic fluid. The rotation of the male member may be done manually or by remote actuation.

1. FIELD OF THE INVENTION
This invention relates in general to hydraulic couplings, and specifically to hydraulic couplings used in undersea drilling and production applications. More particularly, this invention involves a hydraulic coupling configured to urge the members together and axially compress a ring-shaped seal in the female member upon connection of the members.
2. DESCRIPTION OF THE RELATED ART
Subsea hydraulic couplings are old in the art. The couplings generally consist of a male member and a female member with sealed fluid passageways connected therebetween. The female member generally is a cylindrical body with a relatively large diameter longitudinal bore at one end and a relatively small diameter longitudinal bore at the other. The small bore facilitates connections to hydraulic lines, while the large bore seals and slidingly engages the male member of the coupling. The male member includes a cylindrical portion at one end having an outer diameter approximately equal to the diameter of the large bore of the female member of the coupling. The male member also includes a connection at its other end to facilitate connection to hydraulic lines. When the cylindrical portion of the male member is inserted into the large bore of the female member, according to various embodiments of the device, fluid flow is established between the male and female members.
In the past, various types of seals have been used between the male and female members of the coupling. For example, U.S. Pat. No. 4,694,859 discloses an undersea hydraulic coupling with a hollow, ring-shaped metal seal that is pressure energized to seal radially between the female member and the outer surface of the male member. Similarly, in U.S. Pat. No. 4,754,470 two metal seals are positioned between the circumference of the male member and central bore of the female member.
Another type of seal in an undersea hydraulic coupling is disclosed in U.S. Pat. No. 4,637,470. This patent shows a seal that is V-shaped in cross section and is compressed axially between the end or leading face of the male member and a shoulder in the bore of the female member. Belleville washers are used to provide a force between the members to maintain the seals in tight contact. This force is necessary to avoid leakage of hydraulic fluid if the members are slightly separated.
During use of hydraulic couplings, fluid pressure is exerted between the male and female members in such a way as to tend to separate them. The male and female members are typically attached to opposing manifold plates which are held together by bolts or hydraulic members attached to the plates. The male members are commonly attached to one plate while the female members are attached to an opposing plate so as to face the male members and align with them. Typically, groups of 10 or more coupling members are attached to each manifold plate. The manifold plates tend to warp or rock when coupling members are pressured up, thus causing the coupling members to separate slightly.
In the prior art, various approaches have been suggested to secure the male and female members of the coupling together. For example, lock sleeves have been used in so-called quick release couplings. In those type of couplings, a sleeve is pulled back from one member of the coupling to lock or release the coupling members together. Typically a ball and groove configuration is used.
Another approach, as disclosed in U.S. Pat. No. 4,637,470, uses Belleville washers to provide a force urging the numbers together.
Still another approach is that of U.S. Pat. No. 4,915,419 to Robert E. Smith III. This patent shows an apparatus for locking together simultaneously one or more male and female coupling members using a sliding lock plate. In the locked position, passages in the lock plate are configured to engage the circumference of the male and female coupling members and restrict axial movement of the members.

Undersea hydraulic coupling with axial preloading


An arrangement, and associated method, for cleaning and disinfecting an endoscope having an internal channel accessible via an opening. The arrangement includes: a support structure; at least one tray including at least one fixture arranged to maintain the endoscope in the desired position within the tray; a rack arranged to support the tray; a control unit arranged to control and operate the arrangement; a user interface connected to the control unit and arranged to make it possible for an operator to indicate the type of endoscope arranged in the tray; an optical device connected to the control unit and configured to confirm the type of endoscope arranged in the tray; a robotic device operated by the control unit and arranged to clean the at least one channel in the endoscope arranged in the tray; and a disinfector device arranged to enclose the tray and disinfect the endoscope.

During medical examination or treatment different surgical instruments and models of endoscopes are frequently used to take tissue samples, treat different areas within the human body and/or make it possible to visually inspect different areas with the human body.
Endoscopes, and other surgical instruments, are complex and expensive and therefor cleaned and disinfected after use such that each endoscope or other surgical instruments could be used a number of times.
However, the cleaning process of the complex endoscopes is complicated and requires that the interior, the channels and openings of the endoscopes are cleaned manually before the endoscope is disinfected. The manual cleaning involves manual handling of the contaminated used endoscopes and unfortunately expose the person involved for a potential risk of exposure to contaminants. Furthermore, the manual cleaning and handling of the complex endoscopes involves a risk that the cleaning is not performed correctly to ensure that the desired result after cleaning and disinfection is achieved.
It is therefore a need for an improved arrangement for cleaning and disinfection of endoscopes as well as an improved method for conducting the cleaning and disinfection to reduce the described problems.

Arrangement for cleaning and disinfection of endoscopes


Disclosed herein are methods and compositions for correction and/or mutation of genes associated with Parkinson's Disease as well as clones and animals derived therefrom.

Parkinson's disease (PD) is a neurodegenerative disease that afflicts approximately 4-6 million people worldwide. In the United States, approximately one to two hundred people per 100,000 have PD. Interestingly, the prevalence among Amish people is approximately 970 per 100,000 although the basis for this high rate, be it genetic or environmental, is not known. The prevalence of PD increases in the older population, with approximately 4% of people over the age of 80 suffering from this disease (Davie (2008) Brit Med Bull 86(1) p. 109), although 10% of patients are under 40 years of age (Kumari (2009) FEBS J 276(22) p. 6455).
Typically a patient diagnosed with PD is identified by several hallmark physical behaviors: bradykinesia, rigidity and rest tremor. Often these physical symptoms are asymmetric. Within the brain, PD is characterized by a progressive and profound loss of neuromelanin-containing dopaminergic neurons in the substantia nigra pars compacta with the presence of eosinophillic, intracytoplasmic and proteinaceous inclusions termed Lewy bodies in the surviving neurons (Davie, ibid and Kumari, ibid). By the time of death, this region will have lost 50-70% of its neurons as compared to an individual without PD.
Lewy bodies are α-synuclein reactive inclusions that are made up of made of several neurofilament proteins combined with proteolytic enzymes. Lewy bodies are found in PD, and a variant of dementia called Dementia with Lewy Bodies, but are not observed in any other neurological diseases.
It appears to have many factors can play a role in disease onset and/or progression of PD. In particular, genes including α-synuclein (PARK1/PARK4, SCNA), parkin (PARK 2), PARK 3, ubiquitin carboxy-terminal hydrolyase L1 (PARK5) etc.) and environmental factors such as exposure to heavy metals and certain pesticides are believed to contribute to PD.
Additionally, genetic mutations in the leucine rich repeat kinase 2 gene (LRRK2, also known as PARK8) has been identified to be involved in both familial and sporatic forms of PD. In fact, studies suggest that LRRK2 mutations may be responsible for between 5 and 13% of familial PD, and from 1 to 5% of sporadic PD. The protein itself is a large (>280 kD) multidomain protein containing the following known domains: armadillo (ARM), ankryn (ANK), LRR, Ras of complex proteins (ROC), C-terminal of ROC (COR), mitogen-activated protein kinase kinase kinase and WD40. Thus, LRRK2 contains several protein-protein interactive domains (ARM/ANK, LRR and WD40) suggesting that LRRK2 plays a role in protein complex formation (Kumari, ibid). Several clusters of mutations have been identified which fall across its length of the gene, with the majority of pathological mutations clustering in the enzymatic domains of the protein.
Specifically, the LRRK2 mutation G2019S has been suggested to play an important role in PD in some ethnicities. Although prevalence among Asians, South Africans and some Europeans (of Polish, Greek and German descent) is quite low, among Ashkenazi Jews and North African Arabs, the prevalence is from 37-40%. In the US and the rest of Europe, G2019S accounts for approximately 1-7% of familial PD and 1-3% of sporadic PD in Caucasians (Kumari, ibid). The mutation is autosomal dominant and the lifetime penetrance for the mutation has been estimated at 31.8%. The SNP responsible for this missense mutation in patients is annotated as rs34637584 in the human genome, and is a G to A substitution at the genomic level (6055G>A). The G2019S mutation has been shown to increase LRRK2 kinase activity, and is found in the within the activation domain of the protein (Luzon-Toro, (2007) Hum Mol Genet 16(17) p. 2031).
The α-synuclein protein is an 140 amino acid protein comprising three domains: an N-terminal amphipathic domain comprising repeats of KTKEGV (SEQ ID NO: 51), a central hydrophobic, non-amyloid domain, and an acidic C-terminal domain. Increased gene dosage of α-synuclein has been shown to be in and of itself, a toxic event that leads to PD. Gene duplications of α-synuclein, which lead to increased gene expression, causes rare cases Of autosomal dominant PD. The function of the α-synuclein gene (SNCA) in a wild type setting is still unclear, but it appears that it plays a role in the regulation of autophagy (Winslow and Rubensztein (2010, online publication) Autophagy 7:4, p 1-3). It appears that overexpression of the protein inhibits the secretory pathway by a loss of function of the Rabla protein which is involved in autophagasome formation at a very early stage of the autophagy process. This in turn may lead to the cellular pathologies observed in PD: abnormal protein aggregation, mitochondrial abnormalities, increased levels of reactive oxygen species and increased sensitivity to cell death (Winslow and Rubensztein ibid).
In addition to increased gene dosage of the wild type SCNA gene, three mutations have been found which are also associated with PD. The three mutations, A53T, A30P, and E46K are all localized in the N-terminal domain of the protein, and appear to exacerbate toxic fibril formation (Perkevi et al (2009) The Anatomical Record 292 (12): 1893). However, cellular and transgenic animal models expressing such mutants only partially recapitulate PD pathology. See, Dawson et al. (2010) Neuron 66(5):646-61. Individuals with PD caused by α-synuclein mutation have similar clinical and pathological features of their PD as patients with idiopathic PD, however the onset of symptoms occurs significantly than typically seen with other PD patients (Pankratz and Foroud (2004) Am Soc Exp Neu Ther 1:235-242).
Thus, there remains a need for the development of novel anti-PD strategies to model and treat PD based on investigation of LRRK2 and SCNA mutations.

Methods and compositions for gene correction

Whitehead Institute for Biomedical Research


A method and apparatus for accurately determining the count per unit volume of particles, such as red blood cells, suspended in a fluid containing at least one undesirable interference particle, such as air bubbles. A predetermined volume of fluid containing the first and second particles is passed through the a flow cytometer which produces a forward light scattering pattern that is detected and measured. The volume and index refraction of each of the first and second particles is determined. The first and second particles are discriminated in accordance with their respective indices of refraction and the total count and volume of particles is corrected to provide the count per unit volume of red blood cells.

1. Field of the Invention
This invention is directed to a method and apparatus for accurately determining the count per unit volume of particles suspended in a fluid containing one or more undesirable particles. More particularly, the invention pertains to determining the count per unit volume of blood cells in a flow cytometric system wherein the count is corrected for air bubbles present in the blood suspension medium.
2. Description of the Prior Art
The use of flow cytometry for counting blood cells has been increasing over the past several years. A fundamental consideration in the accuracy of blood cell counting is that the suspension of blood cells, if allowed to sit unmixed, will become spatially inhomogeneous due to sedimentation or sticking to the container walls. This occurs due to the fact that the blood cells are in general denser than the fluid they are suspended in and may also have an electrostatic interaction with the walls of the container. This inhomogeniety may interfere with the accuracy of the blood cell counting.
In order to solve this problem, the suspension of blood cells is mixed prior to the cells being passed through the counting mechanism. However, if the suspension is mixed, air bubbles will be introduced into the fluid which may interfere with the accuracy of the blood cell count. This interference is generally caused by the trapped air increasing the fluid volume measured by the system which erroneously lowers the cell count and also by small air bubbles which may be counted as cells erroneously increasing the cell count.
Heretofore, there has not been a system for solving the substantial problems in counting blood cells in a flow cytometer. At present, if the suspension is sampled during or shortly after mixing, error due to air is introduced and if counting is delayed to remove the air, cell loss due to sedimentation or sticking to the container walls is observed.

Method and apparatus for determining the count per unit volume of particles


A control module comprises a thermal detection module and a protection module. The thermal detection module receives temperature data of a particulate matter filter and determines a temperature based on the temperature data. The protection module selectively reduces output of an engine when the temperature is greater than a temperature threshold. A method comprises receiving temperature data of a particulate matter filter and selectively reducing output of an engine when a temperature based on the temperature data is greater than a temperature threshold.

The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Vehicles may include exhaust after-treatment devices such as particulate matter (PM) filters and catalysts to reduce emissions. In a diesel engine, the PM filter may be referred to as a diesel particulate filter (DPF). Engine control systems may fail to accurately diagnose when there is excessive thermal energy in the exhaust. In some circumstances, excessive thermal energy may damage components of the vehicle.

This patent is subject to a terminal disclaimer.

Thermal detection and protection of vehicle hardware


A load balancing mechanism (10) disclosed includes an arm (12) including first and second arm portions (14,26). A support post (22) is rotatable about its vertical axis A and supports arm (12) by first arm portion (14) for pivotal movement in a vertical plane and also for rotational movement about axis A. First arm portion (14) includes parallel spaced members (16,16') defining a parallel linkage arrangement. A piston and cylinder balancing arrangement (38) connects post (22) and first arm portion (14) allowing upward and downward pivotal movement of arm (12) and is responsive to such upward and downward pivotal movement to provide balancing of a load thereon. The second arm portion (26) can be longitudinally moved relative to a second mount (32) to increase or decrease the length of arm (12) without having to change the force applied via balancing arrangement (38) to maintain balancing of the load.

Conventional load balancing mechanisms are used by a worker to handle equipment such as heavy air driven tools or to aid in placement for mounting of parts in assembly line type operations, etc. These load balancing mechanisms supply supporting forces in a vertical direction to counter gravitational force for supporting a given load and also structure to resist torque and vibration associated with certain tool operations. Typical load balancing mechanisms include a two-piece articulated arm of a straight cross section pivotally connected to a support post about which the arm is rotatable. The arm is pivotal for movement in a vertical plane and also rotatable about an axis of rotation horizontally displaced from an axis of the support post. A hinged connection allows the two sections of the arm to be selectively moved by a worker for placement of a load located at a distal end of one of the arms within the reach of the articulated arm.
In this conventional arrangement of the load balancing mechanism, deflection is created in the support post by the weight of the arm. This deflection is increased by the application of a load on the arm. This deflection establishes a "home" position, due to the combined effect of deflection of the axis of rotation and the axis of rotation being displaced from the axis of the support post, which is at a lowest elevational position for the arm about the post. The arm drifts to this "home" position if left uncontrolled or unattended. This drift is further exaggerated by the hinged construction of the articulated arm and makes controlling the arm mandatory.
The straight cross sectional shape of the articulated arm also necessitates applying a greater lifting force to the arm to counter the weight of any given load applied to the end of the arm as the greatest bending movement occurs at the connection of the support post and arm.


An assembled pump compressor arrangement of an air-conditioning system having a housing enclosing an impeller with a thrust collar positioned thereon. The arrangement includes a tool for applying torque to the impeller having an outer cylindrical element and a plurality of arcuate sections. The arrangement further includes a releasable clamp for interconnecting the arcuate sections and the outer cylindrical element with the impeller clamped between the outer cylindrical element and the arcuate sections. A torque bar is provided which extends through the outer cylindrical element in a spaced relation to the impeller through which the torque is applied to effect disassembly of the high-speed thrust collar and removal of the impeller from the housing of the air-conditioning system.

A centrifugal compressor pump having an impeller driven at a high speed by a motor drivingly connected thereto by gearing supported by hydrodynamic and thrust bearings positioned within a rigid sealed housing of an air-conditioning system, is generally known in the art and manufactured by York International (Model LTMN). In order to prolong the operational condition of such air-conditioning system, it is necessary to periodically inspect and/or replace the high-speed thrust bearing collar and high-speed thrust bearings as parts associated therewith. Such thrust bearing collar is threaded into right-hand threads of a high-speed shaft and into left-hand threads of a pinion gear, making replacement of parts typical involved in disassembly and reassembly of the compressor costly and time-consuming and requiring rigging of heavy equipment with frequent damage and/or rupture of parts. It is therefore an important object of the present invention to provide for inspection and periodic replacement of the high-speed thrust bearing collar and the bearings of the foregoing referred to centrifugal compressor type of air-conditioning system by personnel in a more rapid and less costly manner with little likelihood of damage and/or rupture of parts.

Operational maintenance of air-conditioning installations

The United States of America as represented by the Secretary of the Navy


Provided are an electrode catalyst layer for a polymer electrolyte fuel cell, which is capable of improving drainage property and gas diffusion properties and capable of high output, and a polymer electrolyte fuel cell provided with the same. An electrode catalyst layer (2, 3) bonded to a polymer electrolyte membrane (1) includes a catalyst (13), carbon particles (14), a polymer electrolyte (15) and fibrous material (16), in which the electrode catalyst layer (2,3) has a density falling within a range of 500 mg/cm3 to 900 mg/cm3, or has a density falling within a range of 400 mg/cm3 to 1000 mg/cm3, and the mass of the polymer electrolyte (15) falls within a range of 10 mass % to 200 mass % with respect to the total mass of the carbon particles (14) and the fibrous material (16).

In recent years, a fuel cell has attracted attention as the effective solution for environmental problems and energy problems. In the fuel cell, a fuel such as hydrogen is oxidized using an oxidizing agent such as oxygen, and the chemical energy associated therewith is converted into electric energy.
Depending on a type of electrolyte, the fuel cell is classified into an alkaline fuel cell, a phosphate fuel cell, a polymer fuel cell, a molten-carbonate fuel cell, a solid oxide fuel cell and the like. The polymer electrolyte fuel cell (PEFC) is expected to be applied as a portable power source, a stationary power source, and an automotive power source because it operates at a low temperature with high power density, and is capable of being reduced in size and weight.
The polymer electrolyte fuel cell (PEFC) has a membrane electrode assembly in which a polymer electrolyte membrane, which is an electrolyte membrane, is sandwiched between a pair of electrodes including a fuel electrode (anode) and an air electrode (cathode). By supplying a fuel gas containing hydrogen to the fuel electrode side and an oxidant gas containing oxygen to the air electrode side, electricity is generated by the following electrochemical reaction.Anode: H2→2H++2e−  (1)Cathode: ½O2+2H++2e−→H2O  (2)
The anode and the cathode respectively have a laminated structure of an electrode catalyst layer and a gas diffusion layer. The fuel gas supplied to an anode-side electrode catalyst layer becomes protons and electrons by the electrode catalyst (reaction 1). The protons pass through the polymer electrolyte and the polymer electrolyte membrane in the anode-side electrode catalyst layer and move to the cathode. The electrons pass through an external circuit and moves to the cathode. In a cathode-side electrode catalyst layer, protons, electrons, and the oxidant gas supplied from the outside are reacted to produce water (reaction 2). In this way, electricity is generated by the electrons passing through the external circuit.
Currently, a fuel cell that exhibits high power characteristics is desired to lower the cost of the fuel cell. However, since a lot of water is generated during the high power operation of the fuel cell, water floods on the electrode catalyst layer and the gas diffusion layer to cause flooding in which gas supply is inhibited. When flooding occurs, there is a problem that the power of the fuel cell drops remarkably.
For solving this problem, in PTLs 1 and 2, a catalyst layer containing carbons with different particle diameters or carbon fibers has been proposed.

Electrode catalyst layer and polymer electrolyte fuel cell


A method for producing caramel having a high content of fructose oligosaccharides and caramel product produced thereby is disclosed which comprises mixing sucrose and an organic acid in a ball mill for approximately 0.5 to 4 hours, heating to a temperature of 130.degree.-160.degree. C. for 0.5 to 15 minutes and cooling quickly to produce a caramel product. The ball milling reduces crystallinity and intimately mixes the sucrose and organic acid, lowering the thermolization temperature. The product contains a high proportion of fructose oligosaccharides (D.P. .about.3-10).

Fructose oligosaccharides have nutritional advantages in animal and human diets. These oligosaccharides modify intestinal bacteria and in particular are effective in increasing the proportion of bifidobacteria in the digestive tract of animals. Thus, caramels containing a high proportion of fructose oligosaccharides are more nutritional.
Caramels are products obtained by heating glucose (or other reducing sugars), or sucrose. Typically, the carbohydrates may be heated either dry or with water, either alone or after addition of acid or base or nitrogen compounds, either in a batch or continuous process. The time generally required to achieve caramelization is several hours, typically from 3 to 9 hours.
The composition of caramels has been studied previously and caramels prepared from sucrose have been shown to contain small amounts of oligosaccharides, predominantly glucose disaccharides.
According to the present invention, it has been discovered that a caramel product may be prepared having a high content of fructose oligosaccharides wherein sucrose and an organic acid are milled prior to thermolysis. The milled product is subsequently heated at a temperature of about 5.degree. to 25.degree. C. above the melting point temperature for approximately 0.5 to 15 minutes, and cooled rapidly. The caramel product formed contains a high proportion of fructose oligosaccharides.
Canadian Patent No. 733,457 is directed to a continuous process of producing caramelization by heating sucrose and citric acid to a temperature of 120.degree.-150.degree. C. for approximately 1-10 minutes, however, there is no disclosure that the sucrose and citric acid are to be milled for several hours.
U.S. Pat. No. 2,594,538 also discloses a method of making caramel with sucrose and orange juice acid (citric acid) by heating at a temperature of preferably 120.degree. C. The patent does not disclose mixing the reactants in a mill.
Heretofore there has not been a method for producing caramel compositions containing fructose oligosaccharides. Thus, a need exists for the preparation of caramel which contains a high content of fructose oligosaccharides.

Process for producing caramel having a high content of fructose oligosaccharides and caramel product produced thereby


A device for releasing volatile substances, including a container that contains a solid substrate impregnated with volatile substances and a clamping element. The device also includes at least two retaining arms of the solid substrate. The arms extend substantially from the center of the container and towards the larger exterior edge of the container. The device allows the deformation of the solid substrate to be contained since the arms force the solid substrate to maintain the position thereof in contact with the arms.

The use of air fresheners for vehicles has been a growing market in recent years. There are different technologies for this application which are based on the same domestic use technologies. For example, devices with a bottle and a wick, membrane devices, etc., the majority with a clamping element to fix the device to the ventilation screen of the air conditioning system of the vehicle.
A technology which has been growing considerably recently consists of a system which has a solid gel which contains a volatile substance. This system has a minimal construction: an open container in which the gel has been poured prior to being made solid, a peelable barrier sheet to prevent the evaporation of the product prior to the first use and a clamping element.
The clamping element is often placed in the center of the container to allow the device to be assembled in the center of the screen. Thus the container has a central part, usually cylindrical in which the clamping element is fixed. This means that the device is sold with the clamping element unassembled in order to allow the removal of the barrier sheet.
A significant problem with the use of these types of devices based on gel is linked to the fact that the gel progressively contracts when the volatile substance is released. This contraction is not homogenous over the entire volume of the gel since only one side of the gel is exposed to the atmosphere, generally the rear part of the device, that is to say, the part that is oriented towards the ventilation screen. Thus, this side of the gel contracts first, which can cause the bending of the gel in the direction of the screen.
This is critical if the bending is so significant that the gel ends up contacting the plastic ventilation screen, or the dashboard of the vehicle since the most commonly used plastics for manufacturing the screen or the dashboard are selected for the mechanical and aesthetic characteristics thereof, but they have very poor resistance to perfumes.
Therefore, the contact between the gel and the plastic of the vehicle may cause discoloration of the plastic, the separation or the appearance of bubbles or creases in the coating of the plastic. If this occurs, the only solution is to replace the damaged parts which may be expensive.
This phenomenon is made even more difficult to solve because there are a very high number of usage configurations of the product since there are a wide number of designs of the screen, different ways of fixing the device on the same screen and different environmental conditions for the evaporation (heating, air conditions, ultraviolet light system, etc.).
Therefore, the object of the present invention is to provide a device for releasing volatile substances for vehicles having a gel deposit which limits the deformation of the gel during the evaporation.

Device for releasing volatile substances


An integrated electrostatically-controlled micromechanical gyroscope with a rotor encompassed within a rotor cavity and electrostatically spun within the cavity. The gyroscope includes a plurality of axial electrostatic rotor actuators above and below the rotor for controlling the axial and tilt position of the rotor within the cavity, and a plurality of radial electrostatic actuators spaced circumferentially around the rotor for controlling the radial and tilt position of the rotor within the cavity. The position of the rotor within the cavity is then resolved to determine the external forces acting on the rotor.

Mechanical gyroscopes with a spinning rotor or flywheel are used in many autonomous vehicles such as airplanes, satellites, and missiles. Because in most of these applications space is at a premium, it is desirable to have gyroscopes as small as possible, while retaining sufficient accuracy for the application. In addition, particularly for space vehicles, weight is a major concern.
Gyroscopes for these applications typically employ a rotated disc or sphere that rotates on mechanical or hydrodynamic bearings. The required number of parts and tolerances between the parts dictates the smallest possible size that can be attained using machining fabrication processes. The motor used to spin the rotor, and the sensors and actuators used to control the position of the rotor, then must be made commensurate in size with the rotor; the motor must be large enough to develop the torque necessary to control the mass of the rotor.
The rotor rotational rate of these gyros is typically on the order of only 50,000 rpm in order to limit the kinetic energy so that the rotors can be properly contained, and minimize problems associated with catastrophic rotor failure. However, it is desirable to spin the gyroscope rotors at the highest possible rate because the accuracy of the gyroscope is related to the rotor rotational velocity. In addition, the relatively large rotor mass creates a relatively high demand for power in these gyroscopes, both to spin the rotor and control its position. Accordingly, there is a great need for a much smaller gyroscope having very high rotor rotational speed and decreased power demand.
There are other applications for gyroscopes, such as in guided automobiles, that do not place such a premium on gyroscope size, weight, or power demands, although these are always concerns. However, to make the use of gyroscopes practical for such devices, there cost must be minimal. The present day machined gyroscopes require at least some manual machining steps, cleaning and assembly. Accordingly, gyroscopes to date have been essentially custom produced devices that are extremely expensive and so not practical for myriad desired uses.

Electrostatically controlled micromechanical gyroscope


A heterojunction power device includes a substrate; a III-nitride semiconductor region over the substrate; a source operatively connected to the semiconductor region; a drain operatively connected to the semiconductor region; a gate between the source and drain and over the semiconductor region. The source is in contact with a first portion located between the source and gate and having a two dimensional carrier gas. The drain is in contact with a second portion located between the drain and gate and having a two dimensional carrier gas. At least one of the first and second portions has a trench having vertical sidewalls and formed within the semiconductor region; mesa regions extend away from each sidewall of the trench. The two dimensional carrier gas is located alongside the mesa regions and the trench. At least one of the source and drain is in contact with the respective two dimensional carrier gas.

Power semiconductor devices are the core of all power electronics systems. It has been evaluated that at least 50% of the electricity consumption in the world occurs in systems that contain power devices [1]. Two main quantities characterize power devices in terms of the range of applications. These are (i) current rating in an on-state operation; (ii) breakdown voltage in an off-state operation. Another parameter is the on-state resistance, Ron, as this directly associates the power device to its on-state power consumption. The lower the Ron the lower the power conduction losses are. A trade-off exists between the maximum voltage sustainable in the off-state (i.e. breakdown voltage, BV) and on-state resistance. Consequently, devices with a relatively high breakdown voltage suffer from a high on-state resistance. So far, silicon (Si) has been the main semiconductor of choice for power devices. Given its versatility and ease of manufacture, Si has been adopted in power device technologies, particularly to cover a wide range of power applications from few volts to 10 kV of breakdown voltage. However, Si has a small bandgap (Eg=1.12 eV) which leads to it being able to sustains less volts per centimetre (cm) before failure (critical Electric field) than a wide bandgap semiconductor device. This results in a waste of semiconductor area for a rated voltage.
Wide bandgap materials, such as Gallium Nitride (GaN), have the benefit to have a higher critical electric field. Furthermore, Aluminium Gallium Nitride (AlGaN)/GaN hetero-structure based devices such as High Electron Mobility Transistors (HEMTs) have been proven to have a much better Ron vs BV trade-off compared to equivalent silicon counterparts. This is due to main properties: (i) their piezoelectric nature which gives very high charge density (e.g. 1e13 cm−2) confined at the AlGaN/GaN interface, and (ii) the above mentioned higher critical electric field (˜3 MV/cm).
A basic AlGaN/GaN HEMT (also known as Hetero-structure Field-Effect-Transistor (HFET) or Modulation FET (MODFET)) is based on a conductive channel formed at the AlGaN/GaN interface being formed on a horizontal plane and connecting to ohmic source and drain contacts. A Schottky gate contact placed on top of the hetero-structure along the source-to-drain distance modulates the charge in the channel [2].
A HEMT structure is schematically shown in FIG. 1 and is a normally-on or Depletion-mode device, i.e. a channel 105 is already formed when zero bias is applied on a gate terminal 110. In power electronics applications normally-off operation is preferable as it is safer and also allows for simple gate drive circuits. Several technologies have been proposed so far to obtain normally-off (or Enhancement Mode) devices. Among these the fluorine-based plasma treated gate [3], recessed gate [4] p-doped gate [5], and insulated gate [6] or combination of these (in [7] a combination of fluorine implantation and partially recessed gate is proposed). These solutions have demonstrated to be effective in guarantying a normally-off operation by depleting the portion of the channel underneath the gate contact 110 at zero bias.
FIG. 2 shows a schematic representation of a HEMT in which an insulated gate technology is used. The insulated-gate technology provides a solution to the normally-on issue as it provides a stable and high value (>1.5V) for the threshold voltage as well as low leakage current through the gate contact. Variations to the basic structure as shown in FIG. 2 featuring a partially recessed insulated gate 205 in the AlGaN layer 215 have been proposed with the aim to improve the channel mobility [7], increase and better control the threshold voltage via the formation of an inversion channel into a p-doped GaN layer 210 along the sidewalls of a trench [8, 9].
GaN-based transistors, independently of the technology used for obtaining normally-on or -off operation, often show poor reliability when biased to high voltages for prolonged periods. This is due to existence of surface and bulk traps which get activated when the off-state high voltage stress is applied on the devices for a prolonged time. As a result, the electrons are captured from the 2DEG layer into the traps leading to a very undesirable increase in the on-state resistance. This is known in the field as 'the current collapse' or dynamic Ron, which is assumed to be higher than the static Ron. Possible solutions to reduce the trapping mechanisms include control of the P-type carbon doping [10], quality and nature of the buffer layer thickness [11], and p-type ohmic contact in the GaN bulk region [12]. No one of these approaches, however, has so far demonstrated a complete 'collapse-free' operation of the GaN devices.
Three-dimensional geometries with periodical trenches within the gate region have been previously proposed for normally-on [13] and normally-off transistors [14]. Both [13] and [14] however describe the benefits of a three-dimensional trench of the gate region leaving the source-to-gate and gate-to-drain distances left planar.
Periodical trenches along the source-to-drain distance with vertical and lateral AlGaN/GaN hetero-structure have been discussed in [9]. However, the direction of the current flow in the suggested structures is only two-dimensional.
It would be desirable to have GaN-based transistors with good current scaling. The scaling of the technology in current at the moment is limited to the lateral configuration. In fact, the present devices are limited to 100 A, with most of the devices being competitive under 20 A. The limitation in current is given by (i) limited surface conduction on account of the lateral flow of the current and (ii) wasted area due to the placement of all terminals and metal tracks at the surface.
It is an object of the present invention to address the poor current scaling and current collapse issues discussed above and concomitantly disclose a device with lower specific on state resistance, Ronsp (the specific Ronsp=Ron×A where A is the surface active area).


Described are preferred vapor recovery canisters which are useful in on-board vehicle fuel vapor recovery systems. The preferred canisters incorporate thermal management of solid adsorbent with phase change materials to improve both adsorptive and desorptive capacity of the canisters. Also described are preferred encapsulation members for use in the vapor recovery canisters.

The present invention relates generally to vapor recovery canisters and in particular to on-board fuel vapor recovery canisters incorporating means for thermal management of a solid adsorbent during fueling and purging cycles so as to increase the respective adsorptive and desorptive capacities of the canister during such cycles.
As further background, during vehicle refueling operations, fuel vapor is displaced from the fuel tank by entering fuel. To prevent the displaced fuel vapors from entering the atmosphere, they are typically adsorbed in a vapor recovery canister. Such canisters are fluidly coupled to the fuel tank, and receive the fuel vapors as they are displaced. An adsorbent material contained within the canister adsorbs the fuel vapors, and a cleansed gas stream exits the canister. After the fueling operation, the adsorbent is loaded with fuel vapor, which can be desorbed as a vapor in a purge cycle and recovered for later combustion. A variety of such systems have been proposed, and for additional general background on vapor recovery systems, reference can be made for example to U.S. Pat. Nos. 5,272,873; 5,299,545; 5,235,955; 5,207,808; 5,143,041; 5,209,210; 5,156,178; 5,194,075; and 5,305,807.
The process of fuel vapor adsorption involves the condensation of the vapor on the surface of the solid adsorbent, an operation which produces heat. This compromises the efficiency of adsorption as fueling progresses because the efficiency of vapor condensation decreases with increasing adsorbent temperature. One way to address this problem might be to increase the amount of solid adsorbent in the canister. Unfortunately, this necessitates an increase in the size of the overall canister device, a result desirably avoided. Moreover, during purge operations, the passage of a gas such as ambient air through the adsorbent bed causes cooling of the bed, leading to a concomitant decrease in desorption efficiency. To address this problem, the purge gas might be heated; however, such a measure involves increased investment in both equipment and energy, and is preferably also avoided.
In light of this background there exist needs for improved vapor recovery canisters and methods which increase vapor recovery capacity without the need to increase the amount of solid adsorbent. An improved vapor recovery canister and method would desirably both increase loading capacity during a fueling operation and facilitate the removal of fuel as a vapor during a purge cycle. The present invention addresses these needs.

Thermally-managed fuel vapor recovery canister


A semiconductor structure includes a semiconductor substrate, a first doped region, a second doped region and a dielectric. The first doped region and the second doped region respectively has an aspect ratio and a dopant concentration uniformity along a depth in the semiconductor substrate. The dielectric is between the first doped region and the second doped region. The dopant concentration uniformity is within 0.2% and the aspect ratio of the semiconductor substrate is greater than about 10.

Semiconductor device is widely adopted in various applications. The geometry is trending down rapidly as user's demands increase on the performance and functionality. For example, a compressor with frequency conversion in the market is expected to be capable of reducing on-resistance, performing high speed switching and implementing with high breakdown voltage. In order to fulfill the requirements, the compressor needs to be equipped with several structures such as super junction.
The super junction structure is constructed by alternately arranging an n type impurity area and a p type impurity area constituting a p-n column pair. Usually, several processes, such as multiple etching, implanting and driving-in, are involved in constructing the p-n column pair. However, the implanted area is etched that shapes the impurity region into a jagged contour, which is unable to perform the function of the super junction. Thus, a structure or a method for forming the p-n column pair is still in great demand.

Semiconductor structure and manufacturing method thereof

TAIWAN SEMICONDUCTOR MANUFACTURING COMPANY LTD.


A method is described of managing nodes in a computer cluster comprising: each node repeatedly broadcasting a cluster summary message; a cluster coordinator node identifying failed nodes by analysing cluster summary messages received from other nodes in the cluster; and the cluster coordinator node broadcasting an updated cluster organization status, if failed nodes are identified. In at least preferred embodiments, the broadcasts can be transmitted using an ad-hoc wireless network.

A computer cluster is a parallel or distributed system that comprises a collection of interconnected computer systems or servers that is used as a single, unified computing unit. Members of a cluster are referred to as nodes or systems. The cluster service is the collection of software on each node that manages cluster-related activity. The cluster service sees all resources as identical objects. Resources may include physical hardware devices, such as disk drives and network cards, or logical items, such as logical disk volumes, TCP/IP addresses, entire applications and databases, among other examples. By coupling two or more servers together, clustering increases the system availability, performance and capacity for network systems and applications.
Clustering may be used for parallel processing or parallel computing to simultaneously use two or more CPUs to execute an application or program. Clustering is a popular strategy for implementing parallel processing applications because it allows system administrators to leverage already existing computers and workstations. Because it is difficult to predict the number of requests that will be issued to a networked server, clustering is also useful for load balancing to distribute processing and communications activity evenly across a network system so that no single server is overwhelmed. If one server is running the risk of being swamped, requests may be forwarded to another clustered server with greater capacity. For example, busy Web sites may employ two or more clustered Web servers in order to employ a load balancing scheme. Clustering also provides for increased scalability by allowing new components to be added as the system load increases. In addition, clustering simplifies the management of groups of systems and their applications by allowing the system administrator to manage an entire group as a single system.
Clustering may also be used to increase the fault tolerance of a network system. If one server suffers an unexpected software or hardware failure, another clustered server may assume the operations of the failed server. Thus, if any hardware of software component in the system fails, the user might experience a performance penalty, but will not lose access to the service.
Known cluster services include Microsoft Cluster Server (MSCS), designed by Microsoft Corporation for clustering for its Windows NT 4.0 and Windows 2000 Advanced Server operating systems, and Novell Netware Cluster Services (NWCS), among other examples. For instance, MSCS supports the clustering of two NT servers to provide a single highly available server. Clustering Services are built-in to Microsoft Windows Server 2003.
Clustering may also be implemented in computer networks utilizing storage area networks (SAN) and similar networking environments. SAN networks allow storage systems to be shared among multiple clusters and/or servers. The storage devices in a SAN may be structured, for example, in a RAID configuration.
In order to detect system failures, clustered nodes may use a heartbeat mechanism to monitor the health of each other. A heartbeat is a signal that is sent by one clustered node to another clustered node. Heartbeat signals are typically sent over an Ethernet or similar network, where the network is also utilized for other purposes.
Failure of a node is detected when an expected heartbeat signal is not received from the node. In the event of failure of a node, the clustering software may, for example, transfer the entire resource group of the failed node to another node. A client application affected by the failure may detect the failure in the session and reconnect in the same manner as the original connection.
Interconnects, switches or hubs used for heartbeat message exchanges in a cluster are subject to failures. When such interconnects, switches or hubs fail, cluster integrity is lost as the membership of the cluster becomes unknown. Each node or a set of nodes will then try to re-form the cluster separately. If this were allowed to occur, there would be the potential to run the same application in two or more different locations and to corrupt application data because different instances of an application could end up simultaneously accessing the same disks. This problem becomes more complicated for large clusters because interconnects, switches or hubs are physically separate hardware devices and pin-pointing their failure is quite difficult and sometimes impossible for the cluster nodes.
Currently, redundant interconnects and a quorum device like a lock disk or quorum server are often used to manage such situations.

Method of managing nodes in computer cluster

Hewlett-Packard Development Company, L.P.


A thin film transistor array panel including a substrate, a gate line and a gate-layer signal transmitting line of a gate driving circuit portion formed on the substrate, a gate insulating layer formed on the gate line and the gate-layer signal transmitting line and having a first contact hole exposing a portion of the gate-layer signal transmitting line, a semiconductor layer formed on the gate insulating layer, a data line including a source electrode, and a drain electrode formed on the gate insulating layer and the semiconductor layer, a data-layer signal transmitting line of the gate driving circuit portion formed on the gate insulating layer and connected to the gate-layer signal transmitting line through the first contact hole, a pixel electrode connected to the drain electrode, and a passivation layer formed on the data line, the drain electrode, and the data-layer signal transmitting line of the driving circuit portion. The data line, the drain electrode, and the data-layer signal transmitting line have a triple-layered structure including a lower layer, an intermediate layer, and an upper layer. The lower layer is made of a same layer as the pixel electrode.

(a) Technical Field
The present disclosure relates to a thin film transistor array panel for a liquid crystal display and a manufacturing method thereof.
(b) Discussion of the Related Art
A liquid crystal display (LCD) includes a pair of display panels having field generating electrodes and polarizers, and a liquid crystal layer interposed between the two display panels. A field generating electrode generates an electric field on the liquid crystal layer. The arrangement of liquid crystal molecules in the liquid crystal layer varies as the intensity of the electric field changes, thereby changing the polarization of light passing through the liquid crystal layer. A polarizer blocks or transmits the polarized light appropriately to make bright and dark regions, thereby displaying desired images.
One of the display panels includes a plurality of pixels having switching elements and a plurality of display signal lines, and a gate driver having a plurality of stages transmitting gate signals to gate lines of the display signal lines to turn on/off the switching elements of the pixels.
Each stage of the gate driver is connected to one of the signal lines, and the stage receives a gate on/off voltage and a clock signal, and transmits the inputted gate on/off voltage and clock signal to the signal line connected thereto.
The gate driver may be integrated with the substrate, and then the gate lines may extend to connect to the gate driver directly. Here, for connecting gate wires of the gate driver and data wires of the gate driver, contact holes exposing the gate wires are formed. The data wires are connected to the gate wires through the contact holes using a connecting member which may be made of Indium Tin Oxide (ITO).
Alternately, if the gate driver is formed outside of the substrate, pad portions, which connect the gate on/off signal lines to the stages of the gate driver, are required for transmitting the gate on/off voltage to the stages of the gate driver. Here, for connecting the pad portions to the signal lines, contact holes exposing the signal lines are formed, and then the signal lines are contacted to the stages of the gate driver through the contact holes using a connecting member which may be made of ITO.
As the lengths of the signal lines increase along with the LCD size, the resistance of the lines increase, causing a signal delay or a voltage drop. In response to the increased resistance, wiring is made from of a material having a low resistivity, such as aluminum (Al). When Al is used in wiring, signal lines may have a multi-layered structure including an Al layer and another layer. However, if the signal lines including Al contact with the ITO used in pixel electrodes or connecting members of an LCD directly, then the Al may become oxidized or corroded.
The thin film transistor array panel of a liquid crystal display includes a plurality of thin layers such as a gate layer, a data layer, and a semiconductor layer. The thin layers are respectively patterned by photolithography processes using separate photo-masks. However, when adding one additional mask, various steps such as exposing, developing, and cleansing are repeated, and thereby manufacturing time and cost significantly increase.
Accordingly, there is a need for a thin film transistor array panel with improved resistance to oxidation or corrosion and a method of manufacturing the same which can reduce the time and expense of manufacturing.

Thin film transistor panel and manufacturing method thereof


A multipurpose handle and workpiece attachment tool (10, 12, 14) has a handle (16) and a workpiece (18). The handle has a grip portion (20) at a first end and a first attachment portion (22) at a second end. The workpiece has a second attachment portion (24) adapted to engage the first attachment portion of the handle. The first attachment portion has a sleeve (26) with an opening (30) which can receive the second attachment portion. The sleeve has a clip-lock aperture (32) and a cam-lock aperture (34), and there is a cam clamping lever (28) pivotally connected to the sleeve. The cam clamping lever has an eccentric cam surface (36) which can be moved into and out of the cam-lock aperture by operating the cam clamping lever. The second attachment portion has a first spring loaded button (38a, 38b, 42a) which is spring biased to move into the clip-lock aperture when the first and second attachment portions are engaged, and also has a cam engaging surface (40) against which the eccentric cam surface is pressed when the cam clamping lever is operated. In this way, the handle and the workpiece assume a locked configuration.

There has been a long felt need in the camping and outdoor recreational markets for a multipurpose handle and workpiece attachment tool which is strong, reliable and easy to operate under a wide range of conditions, and that can function as an axe, saw and shovel, as well as a hammer and a hook.
Known multipurpose handle and workpiece attachment tools utilize a variety of different mechanisms or assemblies for attaching a common handle to a selected workpiece. In many cases, the mechanisms involve components, such as hitch pins and thumb screw bars, which are separate from either the handle or the workpiece, and need to be fitted to the tool after the handle and workpiece are attached together.
In other cases, where no such separate components are utilized, the handle and selected workpiece have built-in structures which enable them to be attached together, but these generally result in a limited range of tools and in their effectiveness being limited due to structural constraints.

Multipurpose handle and workpiece attachment tool


Methods and systems for automatically inspecting a wire-wrapped well screen are provided. A camera may capture an image of a portion of the screen including at least two facing edge portions of adjacent wraps of wire defining a slot therebetween. A thickness of the slot may be determined based on the image, for example, by calculating a distance between the facing edge portions. The camera may be moved relative to the screen to measure slot thickness at several sample locations along a length of the screen. The screen may also be rotated relative to the camera to measure slot thickness at sample locations at different angular offset locations around the screen. Slot thickness measured at the sample locations may be analyzed to generate an inspection report that could be supplied to a customer with the well screen.

1. Field of the Invention
Embodiments of the present invention generally relate to well screens and more particularly to inspection of slot thickness between adjacent wraps of wire on wire-wrapped well screens.
2. Description of the Related Art
In the drilling of oil and gas wells, a wellbore is formed in a formation and typically lined with a string of steel pipe commonly referred to as casing. In a process generally referred to as well completion, a string of tubular elements and various pieces of equipment required to enable safe and efficient fluid production are assembled downhole, often within the casing. As part of the well completion process, the casing is typically perforated to allow fluids to flow from an adjacent portion of the formation into the wellbore. In many cases, these formation fluids include undesirable particles, such as sand, that may result in inefficient production if not screened from the production flow.
Producing sand along with well fluids can result in premature failure of production equipment (e.g., artificial lift equipment). Further, collections of sand (sand bridges) formed in the casing or tubulars may impede and eventually obstruct flow of the production fluids. Sand production may also cause erosion or compaction of the surrounding formation which may lead to casing failure. Casing failure in or around a producing zone may lead to loss of the well. Therefore, the control of sand flow from formations is one of the most critical problems in well completion. In some cases, to control sand, a well screen is placed in the wellbore and the surrounding annulus is packed with gravel of a specific size designed to prevent the passage of formation sand into the production flow. The primary objective of this "gravel pack" is to prevent the flow of formation sand, while causing minimal impairment to well productivity.
One type of well screen commonly used for gravel pack applications, as well as stand-alone sand control applications, is a wire-wrapped well screen. A wire-wrapped well screen is typically formed by helically wrapping wire having a controlled profile around a length of perforated base pipe. The thickness of the continuous slot formed between adjacent wraps of the wire is controlled to be small enough to retain the gravel placed behind the screen (or any material to be screened from the production fluid), yet minimize any restriction to flow of the production fluid. Therefore, it is highly desirable that the thickness of this slot (commonly referred to as the slot gauge) be maintained as uniform as possible. Wire-wrapped well screens may be relatively long (often several tens of feet), while the wrapped wire and slot thickness may be relatively small (often less than 0.1 inches and 0.01 inches, respectively). Thus, current processes for manufacturing wire-wrapped well screens yield a product with tens of thousands of slots (i.e., portions of the continuous slot between adjacent wire wraps) to inspect.
Despite the fact that the thickness of slots between adjacent wire wraps may be the most critical attribute of a wire-wrapped screen, the large number of slots makes inspecting each slot economically impractical using conventional measurement techniques. For example, conventional inspection techniques include manually sliding a feeler gauge (e.g., a metal leaf of a known thickness) into the slot or manually using an optical scope to measure slot thickness, both of which are time consuming and prone to human error. To save time, a relatively small set of sample slots may be measured and statistical techniques may be applied to determine an average slot thickness, minimum/maximum slot thickness, and the like. However, the relatively small set of sample slots may be insufficient as there may be relatively long sections of the continuous slot between slot samples that are not inspected.
Accordingly, what is needed is an improved method for inspecting wire-wrapped screens to measure slot thickness between adjacent wire wraps, preferably, an automated system that allows for faster inspection than conventional manual inspection techniques.

Automated optical inspection of wire-wrapped well screens


A technique includes communicating data between a host computer and a peripheral device. The peripheral device is docked to the host computer, and the communicating comprises using a wired mode of communication. The technique includes detecting undocking of the peripheral device from the host computer; and in response to the detection of the undocking, automatically transitioning from using the wired mode of communication to using a wireless mode of communication to communicate data between the host computer and the peripheral device.

A portable computing device, such as a tablet computer, may have an associated Bluetooth keyboard that is wirelessly paired to the computing device. In this manner, a radio of the keyboard may communicate with a radio of the computing device for purposes of communicating input from the keyboard, such as key strokes, trackpad movements, and so forth.

Controlling a mode of communication between a host computer and a detachable peripheral device


A method for communication includes setting respective overbooking ratios for multiple categories of data traffic, and assigning respective bandwidth allocations to a plurality of connections for transmitting the data traffic in one or more of the categories over a network. The data traffic from the connections is coupled into respective queues, such that each of the queues is associated with one or more of the connections. Respective weights are computed for the queues responsively to the bandwidth allocations and to the overbooking ratios of the categories of the data traffic to be transmitted on the connections that are associated with each of the queues. A multiplexer multiplexes among the queues responsively to the respective weights so as to transmit the data traffic from the connections over a link in the network.

Network service providers frequently aggregate communication traffic from multiple sources for transmission over a shared, high-bandwidth link. Service providers commonly overbook their available bandwidth in order to maximize utilization of this costly resource. In other words, the sum of the bandwidth that the service provider makes available to all traffic sources may exceed the actual bandwidth available on the shared link. Most of the time, the traffic sources generate less than their full bandwidth allocation, so that the aggregated traffic volume is less than the shared link capacity, and all of the traffic is transmitted over the shared link at the rate at which the traffic is generated by the sources. During periods of peak demand, however, the aggregated traffic volume may exceed the shared link capacity. In this case, at least some of the traffic must be buffered, and frames may be dropped if the buffer overflows.
To determine how bandwidth is to be shared during periods of heavy demand, service providers typically define multiple classes of services, with different bandwidth allocations and priorities. Each class of service (CoS) may have a committed information rate (CIR), which the service provider guarantees to provide, and an excess information rate (EIR), which the service provider provides on a best-efforts basis. (Some classes of service may have only a CIR allocation, or only an EIR allocation.) Each connection served by the service provider belongs to a specific class of service (CoS), which may be specified in a service level agreement (SLA) between the service provider and the customer making the connection. In aggregating traffic for transmission over the shared link, the service provider attempts to ensure that all traffic within the CIR of each connection is transmitted. The service provider then divides any remaining capacity among the connections according to their EIR allocations.
Service providers generally try to allocate their available bandwidth fairly among their customers. For this purpose, incoming data packets arriving from different sources are queued, and the traffic aggregator multiplexes among the queues in accordance with a fair scheduling scheme. Different weights may be assigned to different queues in order to permit different sources to receive different relative shares of the available capacity. Various fair scheduling schemes are known in the art. In Fair Queuing, for example, if there are N active queues at any given time, each queue receives 1/N of the available bandwidth. In Weighted Fair Queuing (WFQ), different queues may have different service shares according to their relative weights. In some applications of WFQ, including some embodiments of the present invention that are described hereinbelow, each source or connection has its own queue, an ill-behaved source (generating more than its fair share of traffic) will only punish itself and not other sources. Weighted Round Robin (WRR) scheduling operates on similar principles.
U.S. Pat. No. 6,157,654, whose disclosure is incorporated herein by reference, describes a method for adaptively assigning queue service weights to an ATM traffic management controller in order to reduce service weight update calculations. The queue weight configuration is performed using a reconfigurable weighted fair queuing controller, wherein bandwidth requirements for each queue may be changed in response to connection setup and release values.

Automated weight calculation for packet networks


Even in a case where light sources at an optical transmission-side and an optical reception-side are made into a common light source, a optical transmission function and an optical reception function are enabled to be used at a time.

In recent years, a digital coherent optical transmission technique has been put into practice, and a high-reliable long-distance large-capacity transmission accommodating various ultra high-speed client signals in an ultra high-speed single wavelength channel having a speed equal to or more than 100 Gbit/s has been realized.
A block configuration diagram of a generally-available digital coherent optical transmission/reception device is shown in FIG. 11. The generally-available digital coherent optical transmission/reception device is implemented with an optical transmission light source 10000 and an optical reception light source 20000. A control unit 50000 respectively adjusts the optical output powers of the optical transmission light source 10000 and the optical reception light source 20000, thus optimizing the transmission and reception property.
The light which is output from the optical transmission function light source 10000 is optically modulated by the optical modulation device 30000, and is output as an output signal light. The light which is output from the optical reception light source 20000 interferes with an optical signal which is input into the optical reception device 40000 as a local oscillation (LO: Local Oscillator) light.
In this case, the wavelength of the light which is output from the optical reception light source 20000 interferes with the optical signal which is input into the optical reception device 40000, and therefore, the wavelength needs to be the same as the wavelength of the input optical signal. The digital coherent optical transmission/reception device uses a wavelength variable light source as the light source at the reception side, thereby changing the wavelength of the LO light in accordance with the wavelength of the input optical signal. Therefore, in a case where a wavelength division multiplexing (WDM: Wavelength Division Multiplexing) optical signal is input, a particular wavelength can be selectively received from the WDM signal.
On the other hand, in the digital coherent optical transmission/reception device, the demand for reducing electric power consumption and reducing the size is increasing. As a technique for reducing electric power consumption and reducing the size of the digital coherent optical transmission/reception device, for example, a technique has been suggested to make the optical transmission function light source and the optical reception function light source into a common light source, and reduce the light source implemented on the digital coherent optical transmission/reception device.
PTL 1 discloses an optical communication transmission/reception device in which an optical switch switches an output light from a light source into an optical transmission circuit or an optical reception circuit, and in which an optical split circuit splits the output light from the light source into an optical transmission circuit and an optical reception circuit, although this is not a digital coherent optical transmission/reception device.

Optical transmission/reception device, optical communication system and optical transmission/reception method

Abstract: An optical transmission/reception device according to the present invention includes optical split means for splitting the light from the optical output means into a first split light and a second split light, optical power adjustment means for respectively adjusting the optical power of the first split light and the optical power of the second split light, optical transmission means for modulating the first split light whose optical power is adjusted, and outputting the modulated first split light as a first optical signal, optical reception means for receiving the second split light whose optical power is adjusted and a second optical signal given from an outside by causing the second split light and the second optical signal to be interfered with each other, and control means for controlling the optical power adjustment means in accordance with an optical property of the output light.


Disclosed herein is a liquid crystal display device in which a plurality of electrodes is provided on one of a plurality of substrates with a liquid crystal layer interposed therebetween and liquid crystal molecules configuring the liquid crystal layer are driven by an electric field generated between the pair of electrodes, wherein the one substrate has an alignment film which contacts the liquid crystal layer to regulate an alignment direction of the liquid crystal molecules and is provided so as to cover at least one of the pair of electrodes, and wherein the thickness of the alignment film is larger than that of at least one of the electrodes contacting the alignment film.

1. Technical Field
The present invention relates to a liquid crystal display device using a lateral electric field drive system and an electronic apparatus including the same.
2. Related Art
In order to realize a wide viewing angle of a liquid crystal display device, a system for generating an electric field in a liquid crystal layer toward a substrate direction and controlling alignment of liquid crystal molecules (hereinafter, referred to as a lateral electric field system) is known. Examples of the lateral electric field system include an in-plane switching (IPS) system and a fringe-field switching (FFS) system.
In general, in a lateral electric field liquid crystal display device, a pair of electrodes for driving a liquid crystal layer is provided on one of a pair of substrates having the liquid crystal layer interposed therebetween. In a FFS liquid crystal display device, one of a pair of electrodes is provided in the vicinity of the surface of a liquid crystal side of a substrate and an alignment film is formed thereon. This alignment film is formed by coating an organic material such as polyimide on one electrode and performing a rubbing process of rubbing the organic material with a rubbing cloth. However, one electrode includes a plurality of band-shaped electrodes with gaps provided therebetween. In addition, since a surface of the substrate on which the alignment film is formed has a fine step difference, a step difference portion is formed in the alignment film due to the step difference. Accordingly, a rubbing process is non-uniformly performed on the step difference portion and the other points and thus light leakage or decrease in alignment regulating force occurs.
Accordingly, a method of forming an alignment film by an optical alignment process using an optical reactive polyimide as an alignment film has been suggested (see, for example, JP-2004-206091). In this alignment process, polarized ultraviolet rays are irradiated onto the surface of the optical reactive polyimide such that an alignment direction according to polarization is formed without being influenced by the fine step difference.
However, even in this alignment process, the following problems occur. That is, in the optical alignment process, the alignment regulating force of liquid crystal molecules due to the alignment film is small and it is difficult to uniformly perform the alignment process. In addition, productivity is low compared with the rubbing process using the rubbing cloth.

Liquid crystal display device and electronic apparatus


A control circuit of a digital control power circuit is provided. The control circuit includes a feedback controller configured to generate a digital duty command value such that a digital feedback value corresponding to an output voltage of the digital control power circuit is close to a target value thereof, a pulse generator configured to generate a pulse signal having a duty ratio corresponding to the digital duty command value, a non-linear controller configured to correct a pulse width of the pulse signal when a variation in the output voltage is detected, and a driver configured to drive a switching device of the digital control power circuit depending on the pulse signal.

In order to generate a voltage lower or higher than a given input voltage, a power circuit such as a DC/DC converter (switching regulator) is used. The power circuit includes an analog control-type power circuit and a digital control-type power circuit. In the analog control-type power circuit, an error between an output voltage of the power circuit and a target value of the power circuit is amplified by an error amplifier, and then a duty ratio of switching is controlled depending on an output of the error amplifier, thereby stabilizing the output voltage to the target vale. In the digital control-type power circuit, an output voltage of the power circuit is converted into a digital value by an A/D converter, and then a duty ratio of a switching transistor is controlled through digital signal processing.
The digital control-type power circuit (digital control power circuit) is not greatly restricted in a control algorithm, so that a degree of freedom of design is high, and there is also advantage that a control scheme or a set value of an output voltage can be changed by software. Further, there is an advantage that can hold the history of various types of data as digital values on the occasion of a long-term operation.
FIG. 1 is a block diagram of a digital control power circuit. A power circuit 100r includes an output circuit 102 and a control circuit 200r. The output circuit 102 includes a switching transistor M1, an inductor L1, a rectifying device D1, and an output capacitor C1.
An A/D converter 202 converts a feedback voltage VFB corresponding to an output voltage VOUT into a digital feedback value DFB. An error detector 212 of a feedback controller 210 generates an error signal DERR indicating an error between the digital feedback value DFB and a target value DREF. A compensator 214 generates a duty command value DDUTY which is changed such that the error signal DERR is close to zero. A pulse generator 220 generates a pulse signal SPWM having a duty ratio corresponding to the duty command value DDUTY. A driver 230 switches the switching transistor M1 depending on the pulse signal SPWM.
FIG. 2 is an operational waveform view of the power circuit 100r of FIG. 1. When a load current IOUT is rapidly increased at a time t1, the charge of an output capacitor C1 is discharged, so that the output voltage VOUT is reduced. There is a delay τ1 until the variation in the output voltage VOUT appears in a sampled feedback value DFB. Further, when the variation in the output voltage VOUT appears in the feedback value DFB, the error signal DERR is increased, but there is a calculation delay τ2 until the error signal DERR is reflected into a duty ratio of the pulse signal SPWM. In addition, due to a delay (not shown in FIG. 2) of the compensator 214, the duty ratio follows the error signal DERR later.
In this manner, since the power circuit 100r samples the output voltage VOUT at a predetermined sampling rate, the power circuit 100r is discontinuously controlled and may have low responsiveness compared with an analog control power circuit which does not require sampling and thus can be continuously controlled. In the example of FIG. 2, after the feedback voltage VFB is lowered, the duty ratio is finally varied at a third pulse P3. That is, there is a great response delay τDELAY, which cannot be neglected, from a time at which the feedback voltage VFB varies to a time at which the duty ratio of the pulse signal SPWM increases, and thus, a variation in the output voltage VOUT is increased.

Digital control power circuit, control circuit thereof, control method, and electronic device using the same


An electro-optic deflector 51 has an electro-optic material body 519 through which an optical beam 46 is passed. The deflector has no more than three longitudinal electrodes, of which no more than two electrodes 511, 512 have arcuate transverse cross-sections. The electrodes are arranged to create an electric field substantially transverse to a direction of the optical beam to deflect the optical beam passing between the electrodes. The electro-optic deflector has particular application in a Q-switched laser for generating sub-nanosecond optical pulses.

Following the first operation of a laser in 1960, techniques were quickly developed to generate intense optical pulses (R W Hellwarth in 'Advances in Quantum Electronics'. Columbia Univ Press, New York, p 334-341, (1961) under heading, 'Control of Fluorescent Pulsations'). A simplest and most widely used arrangement involves use of an optical modulator as a component within a laser oscillator to switch the resonance, or 'Q', of a resonator from 'low' to 'high' after the laser medium has been excited. In this way, a round-trip gain of the oscillator is quickly changed from <1 (below threshold) to >>1 (well above threshold), causing fast build-up and emission of an intense optical pulse. If required, this excitation and switching process can be repeated, in some cases at kHz rates (e.g. U.S. Pat. No. 4,761,786, 'Miniaturized Q-Switched Diode Pumped Solid-State Laser', Baer T M, 2 Aug. 1988).
This Q-switching technique typically allows optical pulses from miniature lasers in the nanosecond (˜10-50 ns) duration range to be generated with thousands of times the intensity of a non-Q-switched laser beam. The intense pulses are used in a very wide range of commercial and scientific applications, as well as for much research. For example, established applications of the laser pulses include: distance ranging, remote mapping, air-speed measurement, precision marking (metal and non-metal surfaces), fine cutting of refractory materials (gem stones, semiconductors, ceramics, etc), stimulating chemical reactions and measuring fluorescence decay (e.g. via 'excite and probe' techniques).
Where short intense laser pulses (in the ˜10 ns duration range) are required, high speed phase modulators based on Pockels effect solid-state electro-optic (E-O) materials have been widely used in the Q-switch. In a most successful arrangement, the Q-switch comprises a Pockels effect modulator in combination with a polarising element. An electric field, applied by electrodes to the E-O material of the modulator, induces a change in refractive index proportional to the electric field strength. This change in refractive index produces a phase difference between orthogonal polarisation components in the laser radiation field, and a high optical loss at the polariser results. Removing the electric field from the modulator removes the optical loss at the polariser i.e. the Q of the laser can be rapidly switched low and high by switching the E-O modulator voltage on and off (Koechner W. 'Solid-State Laser Engineering', Ch 8 Q-Switching. p 469-519. (1998), 5th Edition. Publ by Springer-Verlag, NY, ISBN 3-540-65064-4).
In an alternative scheme Zayhowski ('Diode-Pumped Microchip Lasers Electro-Optically Q-Switched at High Pulse Repetition Rates'. Optic Letters. p 1201-3, Vol 17, No 17, 1 Sep. 1992, and U.S. Pat. No. 5,381,431, 'Picosecond Q-Switched Microlasers', 10 Jan. 1995) disclosed a novel arrangement that eliminates the polariser and allows miniaturisation by using an E-O phase modulator in the form of a variable thickness optical etalon. In this case, E-O crystal faces are finely polished parallel and made partially reflecting at the selected laser wavelength. By application of a voltage, a resultant small change in refractive index is used to change effective reflectivity (feedback) of the modulator into the miniature laser resonator of which it is a part. In this way, the resonator Q can be switched high/low by application of a controlled voltage step to the E-O crystal. In practice, this coupled laser resonator is very difficult to implement as many factors must be favourable if reliable and consistent performance is to be achieved, for example problems arise because the Q of the 3-element etalon (which comprises the resonator) is sensitive to temperature distribution (pump power/gain), the required mechanical alignment of parts is very high, the change in Q is sensitive to voltage (Q-switch circuit), and the laser operating wavelength (longitudinal mode) may 'hop' under switching conditions. For these reasons and others, the arrangement is believed not to have been implemented outside of a laboratory environment and not to be practicable.
Rather than generating a phase difference between orthogonal polarisation components, the Pockels effect in an E-O material can be used to produce fast optical modulation by beam deflection. Such a gradient deflector 10 is illustrated in FIG. 1, where by generating a small gradient of the refractive index, from no−Δn to no+Δn, across an input beam 11, an output beam 12 is deflected i.e. the modulator acts like a weak optical prism (Fowler V J. Buhrer C F, and Bloom L R, Proc IEEE (Corres). 1964, February 1964). Referring to FIG. 2, in 1968, Lotspeich described the use of a quadrupole electrode arrangement 20 to generate a necessary field and resultant refractive index gradient in a potassium dihydrogen phosphate (KDP) type E-O material (Lotspeich J F, 'Electrooptic Light-Beam Deflection', IEEE Spectrum, p 45-52, February 1968). FIG. 2 is a cross-sectional schematic diagram of a quadrupole array of parallel-rod electrodes 21 to produce a linear variation of refractive index in an x direction within a KDP-type electro-optic material. The proper crystallographic orientations of the <001> and <110> directions are indicated. This deflector type of E-O modulator was proposed for use as an alternative practical laser Q-switch in 1979 (Ireland C L M, 'Some Design Considerations and Applications of a Fast Crystal Deflector', in Proc IV Quantum Electron Conf Edinburgh, pp 87-91, 1979. Pub Wiley, NY (1980)) and a Q-switch, following a design similar to that of FIG. 2 using lithium tantalate (LiTaO3) as the E-O material, was subsequently demonstrated (Friel G. J. Conroy R S, Kemp A. J, Sinclair B D and Ley J M, 'Q-Switching of a Diode-Pumped Nd:YVO4 Laser Using a Quadrupole Electro-Optic Deflector', Appl Phys B, Vol 67, p 267-270 1998).
In principle, the E-O deflector type Q-switch has a number of important advantages over the longer established phase difference type. Unlike the latter, the E-O deflector type Q-switch does not rely on a polariser element to complete the switch. This offers the potential of simplicity of design (single component), greater optical efficiency (reduced optical loss for the resonator in the high-Q state) and reduced optical length (miniaturisation). In the last case, miniaturisation is critical to achieve the shortest pulses from a Q-switched laser, since pulse length scales with resonator (optical) length, provided that good hold-off of the resonator round-trip gain is maintained by the Q-switch in its off (low-Q) state.
Although it has potential advantages as a Q-switch, the deflector type modulator has weaknesses and limitations and it is an objective of this invention to provide key improvements and developments that at least mitigate them. A specific objective is to provide a Q-switch suitable for miniaturisation and use in generating very short, high energy, Q-switched laser pulses e.g. pulses of >10 μJ in the ˜100-1000 ps range. Such pulses are very attractive for many applications e.g. (i) for increasing measurement resolution in applications like ranging, aerial mapping and fluorescence diagnostics, and (ii) significantly to improve fine processing results in materials interactions/modification—see for example US 2005150880, 14 Jul. 2005 to Gu and Smart which teaches the clean breaking of memory links in semiconductor circuits.
To achieve short optical pulses it is well known that a laser resonator requires, (i) a high gain laser material e.g. crystal Nd:YAG, Nd:YVO4 or Nd:GdVO4, (ii) to be excited by a high power source such as a focused beam from a laser diode, and (iii) to use a very short optical resonator. The principles have been widely discussed—see for example, Koechner (1998) ibid and 'Theory of the Optimally Coupled Q-Switched Laser', Degnan J J, IEEE Journal of Quant Electronics, Vol 25, No 2, pp 214-20, (1989). In the case of generating very short duration (i.e. ˜100-1000 ps range) pulses, it is expected that the resonator optical length correspondingly must be very short and in the ˜5-15 mm range and the deflector Q-switch, located within the resonator, necessarily be only a few millimeters long i.e. of optical length typically <10 mm.
Since the first operation of the laser, new E-O materials have been identified or developed. In particular, recently rubidium titanyl phosphate (RTP) has become available with some attractive characteristics for use in optical modulators (Lebiush E, Lavi R, Tsuk Y. Angert N, Gachechiladze A, Tseitlin M, Zharov A. and Roth M. in: Proc of the Topical Meeting on Adv Solid-State Lasers, Davos, Switzerland, Trends in Optics & Photonics, Vol 34, p 6370, (2000)). The best E-O materials are single crystals, usually difficult to grow in high optical quality and are thus expensive to produce in usable size. They are often fragile and require specialist skills to work to the required optical standards/tolerances i.e. manufacturing yield can be poor.
Referring to FIG. 1, the beam deflection ΔΦ of a modulator based on an E-O material exhibiting the Pockels effect depends on the crystal aspect ratio (L/W), the appropriate E-O coefficient (r) for the material, and the electric field (E) in the appropriate direction at the aperture limit through the relationship:ΔΦ˜(L/W)·no3·r·E  (1)
Here no is the refractive index in the appropriate direction of the E-O crystal 13, and L·no the optical length. The E-O effect is weak and high electrical field strengths (E typically ˜100-2000V/mm) are required to achieve a useful optical effect. For example, with RTP, LiTaO3 or LiNbO3 the E-O coefficient r is ˜30 pm/V and no is ˜2, so that a deflector of ×10 aspect ratio requires a field in the 300V/mm range to provide a milliradian beam deflection. When used as a Q-switch of a high gain laser, the modulator needs to provide a deflection comparable to the laser beam divergence when switching the resonator between low- and high-Q, so as to inhibit losing in the low-Q state. For a miniature solid-state laser with a TEMoo mode beam this angle is typically in the range of a few milliradians (e.g. 2-10 milliradians).
With a sustained high applied electric Field, materials can develop internal crystal damage—ferroelectric domain reorientation and/or ion migration; the latter leading to what appears as 'grey-tracks' in the high field region(s) of the crystal. In addition, the high drive power coupled with the finite conductivity of the material leads to heating that can adversely affect the optical quality of the crystal, distorting the transmitted laser beam via thermo-optic effects if not adequately dissipated.
Many E-O materials exhibit a reverse piezoelectric effect ('Analysis of the Acoustic Transients in the Pulse Response of the Linear Electro-Optic Effect'. Veeser H, Bogner U, and Eisenmenger W, Phys Stat Sol (a). Vol 37, p 161-70, 1976). When a pulsed high electric field is applied in these materials it leads to the generation of acoustic waves and resonances, which if not adequately damped, distort and aberrate the optical beam being modulated.
A further complication affecting modulator design is that, to different degrees, E-O materials exhibit optical absorption at laser wavelengths. This comprises a normal (small) linear absorption component and sometimes, under high optical fields, a significant non-linear absorption component e.g. due to the Raman effect ('Solid-State Raman Laser Generating < Ins Multi-Kilohertz Pulses at 1096 nm', Pearce S. Ireland C L M, and Dyer P E, Optics Comm Vol 260, p 680-6, 2006). The latter shows up as a power loss via acoustic phonon generation from the optical beam and results in additional heat generation in the Q-switch. If not adequately dissipated, the heat leads to laser beam distortion and aberration via thermo-optic effects.
These difficulties mean that it is most advantageous to design E-O modulators for Q-switches to use short duration voltage pulses of as low amplitude as possible, and include a means of good heat dissipation from the E-O material in their mounting, particularly in the case of high repetition-rate and/or high average laser power applications.
Finally, to different degrees, E-O materials are susceptible to induced optical damage at high laser power densities. A laser damage threshold typically ranges from a few ×10 MW/cm2 to several ×1 GW/cm2 depending on the material and its purity, and this effect greatly limits the choice of E-O materials for practical use in laser applications. The recently grown E-O material RTP and some isomorphs (e.g. KTP in high resistivity form) have relatively good damage resistance to laser intensity and are good candidates in this respect for use in a laser Q-switch
For a deflector type laser Q-switch, the prior art comprises a uniform (undistorted) beam deflection using a single E-O crystal with a quadrupole electrode arrangement to produce a near linear electric field gradient in the material as illustrated in FIG. 2. Lotspeich (1968) taught that an optimum quadrupole configuration comprised four electrodes 21 each with a hyperbolic profile running in the beam direction over the length of the crystal 22, suitably orientated to exploit the maximum E-O effect for the particular material. A cross-section of the Lotspeich arrangement with KDP as the E-O material is shown in FIG. 2. In this case, a beam propagating in the z-axis direction, into the plane of FIG. 2, is deflected in the x-z plane when voltage is applied as shown to the quadrupole electrodes 21. FIGS. 3a and 3b illustrate Q-switched laser resonators 30 in which a Nd:YAG crystal 31 is pumped by a pump diode 32 through an optical fibre 33. Pump light emergent from the fibre is focussed onto a first end face of the Nd:YAG crystal by a focussing lens 34. This first face of the Nd:YAG crystal is coated to be highly reflective at the laser wavelength and transmissive at the pump wavelength. Laser light emergent from a second end face of the Nd:YAG crystal passes though a first end face of the E-O material deflector 20. Laser light emergent from a second end face of the deflector 20 is incident on a partially reflective mirror 35. In use, an angle change ΔΦ imposed on the beam by the deflector allows the beam deflector to be used as a Q-switch for the laser resonator 31, 20, 35, either, as in FIG. 3a, using an applied voltage V0 to switch the resonator Q (i.e. effectively alignment of the mirror 35) from low to high, or, as shown in FIG. 3b, from high to low.
As noted previously, in effect, the deflector 20 acts as a small angle optical prism where the angle ΔΦ can be turned on/off in a controlled manner by applying the voltage V0 and electric field to the crystal. The optical switching speed is as fast as the electric field switching speed which is primarily determined by the electrical capacitance of the Q-switch i.e. to achieve a fast deflector requires a low capacitance and high driving current (see p 76-80 in 'Electro-Optic and Acousto-Optic Scanning and Deflection', Gottlieb M, Ireland C L M, and Ley J M, in Optical Engineering Series, Pub 1983 by Marcel Dekker Inc; NY. ISBN:0-8247-1811-9).
Since electrodes 21 of hyperbolic profile are very difficult to fabricate. Ireland (1979) calculated the effect on field linearity of replacing hyperbolic electrodes by simpler cylindrical electrodes in the quadrupole configuration. He showed that, with an appropriate choice of radius, cylindrical electrodes could be used without introducing a severe field distortion which, otherwise, would have led to optical aberration being impressed on the beam. In this case, the estimated wavefront aberration was ˜λ/2 (where λ was the optical wavelength), and was at least no worse than that calculated due to the grinding and positional errors of the electrodes in the fabrication of the device. Using LiNbO3 as the E-O material, Ireland (1979) reported beam deflection experiments validating his design.
Whether based on prior-art hyperbolic or the simpler cylindrical shape, the quadrupole electrode arrangement for a deflector Q-switch is very difficult to manufacture, and becomes particularly so as the deflector size is scaled-down into the millimeter range. In the 'wings' 23 (region of highest electric field—see FIG. 2) of the crystal 209, the thickness becomes very small (i.e. significantly less than 1 mm) and breakage during fabrication readily occurs in this area. When attempting further miniaturisation of the Q-switch, the required electrode grinding and positional tolerances translate into progressively tighter control of dimensions i.e. the tolerances move into the few microns range. Such alignment is extremely difficult to achieve in the case of four electrodes 21, which not only must be aligned relative to the appropriate axes of the E-O crystal 209, but to each other. For these reasons, the miniaturisation of the prior-art is severely limited. An additional important constraint of the prior-art is the difficulty of mounting the shaped E-O crystal to provide good heat removal and acoustic damping without inducing stress or breakage when employed as a laser Q-switch.
It is an object of the present invention at least to ameliorate the aforesaid disadvantages in the prior art.