The channels of A-EUTRA component carriers on which the mobile station devices of EUTRA do not stand by are configured without almost changing the conventional EUTRA channel configurations. A wireless transmitting apparatus, which performs radio transmission to a plurality of wireless receiving apparatuses by assigning one or more component carriers to a downlink, includes a control channel element processing section 17 for performing, for each component carrier, processing of changing a structure of downlink control channel used to transmit control data for each wireless receiving apparatus. The control channel element processing section 17 associates the modulated symbols output from a downlink control channel processing section 16, with control channel element indexes, rearranges resource element groups constituting control channel elements, and outputs them to a multiplexing section 19.

The 3rd generation (hereinafter, referred to as "3G") Evolved Universal Terrestrial Radio Access (hereinafter, referred to as "EUTRA" or "LTE") and the 3G EUTRA network (Evolved Universal Terrestrial Radio Access Network), of cellular mobile communication have been conventionally studied in 3GPP (3rd Generation Partnership Project).
Further, the study of the 4th generation (hereinafter, referred to as "4G") radio access (Advanced EUTRA: hereinafter, referred to as "A-EUTRA" or "LTE-A") and the 4G network (Advanced EUTRAN), of cellular mobile communication have been started in 3GPP. In A-EUTRA, supporting wider band than EUTRA, and compatibility with EUTRA are studied, and it is proposed that a base station device for A-EUTRA communicates with a mobile station device for EUTRA in all the plurality of frequency bands (hereinafter, referred to as "component carriers") constituting the frequency band of A-EUTRA. That is, it is proposed that all the component carriers have a function capable of transmitting channels with the same configuration as that of EUTRA. On the other hand, in order to introduce a new technology, it is also simultaneously studied to set component carriers which do not have the compatibility with EUTRA and with which only the A-EUTRA can perform communication.
An OFDM (Orthogonal Frequency Division Multiplexing) system that is multi-carrier transmission has been adopted as a downlink in EUTRA. Further, a single-carrier communication system of a DFT (Discrete Fourier Transform)-spread OFDM system that is single-carrier transmission has been adopted as an uplink in EUTRA.
FIG. 15 is a view showing a schematic configuration of a downlink radio frame in EUTRA. In FIG. 15, the horizontal axis is time domain and the vertical axis is frequency domain. The downlink radio frame includes a plurality of Physical Resource Block (PRB) pairs. This physical resource block (PRB) pair is the unit of radio resource assignment and the like, and is made up of a frequency band of a predetermined width (PRB bandwidth) and a time zone (two slots=one subframe). Basically, one physical resource block (PRB) pair includes two physical resource blocks (PRBs) (PRB bandwidth×slots) continuous in time domain.
One physical resource block (PRB) includes 12 subcarriers in frequency domain, and 7 OFDM (Orthogonal Frequency Division Multiplexing) symbols in time domain. A system bandwidth is the communication bandwidth of the base station device. In time domain, there are a slot including 7 OFDM symbols, a subframe including two slots, and a radio frame including 10 subframes. Also, the unit made up of one subcarrier and one OFDM symbol is referred to as a resource element. Further, a plurality of physical resource blocks (PRBs) in accordance with the system bandwidth are allocated in the frequency direction in the downlink radio frame.
In each subframe, at least a downlink shared data channel used for the transmission of information data and system information and a downlink control channel used for the transmission of control data are allocated. The radio resource assignment of the downlink shared data channel is represented by the control data transmitted on the downlink control channel.
Although illustration is omitted in FIG. 15, a downlink pilot channel used for the channel estimation of the downlink shared data channel, the downlink control channel, and the like is allocated at predetermined resource element positions dispersed in the frequency direction and in the time direction in the unit of one resource element.
Although illustration is omitted in FIG. 15, because a broadcast channel used for the transmission of system information is allocated in the time domain and frequency domain defined in advance, the mobile station device, before starting the communication with the base station device, can receive the channel. Specifically, the channel is allocated in first to fourth OFDM symbols of a second slot of a first subframe of a radio frame in time domain, and in the center 72 subcarriers of the system bandwidth in frequency domain.
The system information includes the information necessary for the base station device and the mobile station device to communicate with each other, and is periodically transmitted toward an unspecified number of mobile station devices using the broadcast channel and the downlink shared data channel. Also, the items of the system information allocated in the broadcast channel and the downlink shared data channel are different, and the system information allocated in the broadcast channel includes a system bandwidth, radio frame number and the like. The system information allocated in the downlink shared data channel includes the transmission power control information of the uplink and downlink, and transmission mode information, and the like.
Also, the downlink control channel and the downlink shared data channel are not together allocated in the same OFDM symbol. The downlink control channel includes a plurality of uplink radio resource assignment information, downlink radio resource assignment information, and transmission power command information.    Non-patent document 1: 3GPP TS36.211-v8.4.0(2008-09), Physical Channels and Modulation (Release 8)

Wireless communication system, wireless transmitting apparatus, wireless receiving apparatus, wireless transmission method, and wireless reception method


A rotary snow tiller, for grooming the snow covering of ski slopes, which advances in a traveling direction along the ski slope, and has a frame; a shaft fitted with teeth and rotated with respect to the frame about an axis crosswise to the traveling direction; and an actuating device for imparting a reciprocating movement to the shaft with respect to the frame.

Known rotary snow tillers for grooming ski slopes normally advance in a traveling direction along the ski slope, and comprise a frame; and a toothed shaft rotated with respect to the frame about an axis crosswise to the traveling direction.
Such known rotary snow tillers have proved particularly effective in grooming ski slopes. The snow covering, however, varies considerably with weather conditions, snowfall and, particularly, daily variations in temperature. In the case of a steep temperature swing on either side of zero degrees, the snow covering forms an icy surface crust which, when particularly thick, impairs performance, in terms of quality grooming, of these known rotary snow tillers.

Rotary snow tiller and ski slope grooming method


A method for access network signaling protocol interworking for user authentication includes receiving, from a node in an access network, a message formatted according to a signaling protocol of the access network and containing an authentication payload formatted according to an authentication protocol. The method further includes, in response to receiving the message, formulating a message formatted according to a signaling protocol of a cellular network, the message including the authentication payload formatted according to the authentication protocol. The method further includes forwarding the message formatted according to the signaling protocol of the cellular network to a node in the cellular network that implements the authentication protocol, the message including the authentication payload formatted according to the authentication protocol.

When a user seeks to connect to a non-3GPP access network, the user (e.g. a mobile device) may need to be authenticated with the 3GPP core network to access services, such as VoIP calling, that require core network elements. In one example, the access network may be a trusted or untrusted Wi-Fi network from the perspective of the core network, which may affect some of the parameters used for authentication.
One example of an authentication protocol that could be used to authenticate access network users to the core network is extensible authentication protocol (EAP). For example, EAP authentication can be used between the access network (e.g. a Wi-Fi access gateway (WAG)) and an AAA server in the core network if the signaling protocol used by the access and core networks to carry the authentication information is the same. However, access networks often use different signaling protocols, such as RADIUS, to carry authentication information than protocols, such as Diameter, used by AAA servers. In light of the different protocols and network nodes involved, there exists a need for seamlessly authenticating Wi-Fi and other non-3GPP access network users to cellular networks that use a different signaling protocol to carry authentication information.

This patent is subject to a terminal disclaimer.

Methods, systems, and computer readable media for providing access network signaling protocol interworking for user authentication


An infusion bottle having a partial section of its bottom wall which bulges outward in a cup-like manner and which can be pierced in the region of its bottom wall by an infusion spike. A cup-shaped cover cap is provided which can be placed thereon from the outside and connected in liquid-tight manner. The cover cap has a cover bottom with a central region which can be removed. A clamping ring for the infusion spike is located between the cover bottom and the bottom wall of the bottle. The clamping ring is in the form of an O-ring and has an inside diameter which is smaller than the diameter of the central region. The clamping ring contacts the bottom wall of the bottle and the cover bottom with initial tension and has an outside diameter which is greater than that of the central region.

The present invention relates to a plastic infusion bottle having a partial section of its bottom wall which bulges outward in the manner of a cup and which can be pierced in the region of its bottom by an infusion spike. The partial section and a cup-shaped cover cap, which can be placed thereon from the outside, are connected in liquid-tight manner. The cover cap has a cover bottom with a central region which can be removed. The cover cap also has a clamping ring for the infusion spike placed between the cover bottom and the bottom. The clamping ring is essentially an O-ring having an internal diameter which is smaller than the diameter of the central region.
Such an infusion bottle is known from German Patent No. DE-OS 41 03 041. This infusion bottle is made of polyethylene or polypropylene. An elastic lip is provided in the downward hanging mouth of the infusion bottle to allow a conical infusion spike to be fixed in position. The lip snugly surrounds the infusion spike with radial tension initially. For recycling purposes, the entire closure cap, including the lip, is produced from a uniform thermoplastic material. Such infusion bottles have unsatisfactory properties because it is difficult to obtain a sufficiently firm seat. Moreover, it is difficult to satisfactorily mount and handle the customary infusion spikes whose diameter varies within a minimum range of 4-5.6 mm. Leakages in the transition region between the clamping ring and the closure cap are frequent. The infusion solution in the infusion bottle can therefore, during the removal, pass the clamping disk in the edge region and leak past the inserted infusion spike.
There remains a need for the further development of infusion bottles of the aforementioned type that provide a proper seating and fit with respect to infusion spikes having a wide range of diameters. Moreover, there remains a need for the further development of infusion bottles of the aforementioned type that are capable of being easily recycled.


Each of blades of a multi-blade centrifugal blower is provided with a taper portion, which is arranged at an inside periphery at least at the side of one rotation-shaft-direction end of the blade and tapers from the side of other rotation-shaft-direction end of the blade toward the side of the one rotation-shaft-direction end. The taper portion is positioned at a rotation-direction front side with respect to a back portion disposed at the side of the other rotation-shaft-direction end of the blade. Each of inlet angles throughout the taper portion is set in a range from 55° to 74°. Therefore, air flowing speed at an outlet of an impeller wheel is uniformed throughout the blade width. Work capacity and efficiency of the impeller wheel are increased, while noise is reduced.

A general multi-blade centrifugal blower is shown in FIG. 23. An impeller wheel 7a of the blower is accommodated in a casing 7b, and provided with multiple blades 71 which are arranged around the central line 70 of a rotation shaft (not shown) of the blower. The blower sucks air through a suction portion 74 disposed at the side of one rotation-shaft-direction end of the blower, and blows air toward a diameter-direction outer side of the blower.
The impeller wheel 7a is provided with a large inner/outer diameter ratio and a large blade width (which is dimension in rotation shaft direction of impeller wheel 7a). Therefore, the space which is between the adjacent blades 71 and near the suction portion 74 will become an inefficacious zone, where air flowing direction abruptly varies from the rotation shaft direction to the diameter direction to cause a large eddy so that a main air flow does not flow.
Various proposals are made in order to decrease the inefficacious zone and uniform the outlet (of impeller wheel) air flowing speed throughout the blade 71 for the sake of work-capacity increase, efficiency improvement and noise reduction.
In a multi-blade centrifugal blower with reference to JP-61-107000A, the blade is provided with a cross section shape which is inclined from the side of a boss portion (i.e., main plate) toward the side of a support ring (i.e., side plate) in a direction contrary to a rotation direction of the impeller wheel, in order to exert a force in the rotation direction to air to reduce the inefficacious zone.
In a multi-blade centrifugal blower with reference to JP-2001-115997A, a main plate and a side plate are sequentially twisted, in a state where a blade outlet portion of the side of the main plate is positioned at a rotation-direction front side with respect to the blade outlet portion of the side of the side plate. Thus, an inlet angle and an outlet angel which are different from each other are provided.
In a multi-blade centrifugal blower with reference to JP-4-5500A , the blade of the side of a side plate is bent in the rotation direction with respect to the rotation shaft direction of the blower. That is, a bend portion is provided.
However, in the multi-blade centrifugal blowers with reference to JP-61-107000A and JP-2001-115997A, fluid inflow from the rotation shaft direction is not considered, so that little fluid flows into the space which is between the adjacent blades and near the suction portion. Therefore, the improvement effect is petty.
In the multi-blade centrifugal blower with reference to JP-4-5500A, the bend portion deteriorates operation performance and noise even though the fluid inflow from the rotation shaft direction is considered.


A multi-stage solar power device includes a light-permeable base plate, a plurality of light-condensing plates, a heat-conducting tube, at least one gas turbine, a gas inlet tube and a gas outlet tube. The light-condensing plates include a plurality of arcs with different length. The light-condensing plates are spaced from each other and arranged under the light-permeable base plate to define a plurality of light-reflecting chambers. The heat-conducting tube has first and second ends and extends through the light-reflecting chambers. At least one gas turbine is disposed in the heat-conducting tube. The gas inlet tube has first and second sections. The first section protrudes from the light-permeable base plate, and the second section extends through the light-permeable base plate. The gas outlet tube has one end protruding from the light-permeable base plate, as well as an other end extending through the light-permeable base plate.

1. Field of the Invention
The present invention generally relates to a multi-stage solar power device and, more particularly, to a multi-stage solar power device that uses solar power to drive a generator or other devices for electricity generation.
2. Description of the Related Art
In a conventional method to drive a gas turbine, a combustion chamber filled with an oil fuel is configured at a front section of the gas turbine. Then, the oil fuel in the combustion chamber is burned to generate a gas with high temperature/high pressure for driving blades of the gas turbine.
However, the above gas turbine driving method is performed on complex equipments and requires a great deal of electricity or fuel consumption. Particularly, when the gas turbine is connected to a generator for electricity generation, the gas turbine has to operate under a high temperature for a long period of time. As a result, a lot of energy is consumed and a significant amount of waste gas is generated, leading to environmental pollution.

National Pingtung University of Science & Technology


A composition and method for suppressing pain and irritation of tissue uses an anti-irritant in an effective amount to suppress pain and irritation temporarily when applied topically to the skin, mucosa, or the eye. The anti-irritant is a natural or non-nutritive sweetener. The composition can contain an edible acid such as citric acid and ascorbic acid from fresh lemon juice to provide a pH of about 2.0 to 4.0 and an anti-irritant, such as sodium saccharine. The composition can be used to treat cuts, scratches and abrasions on the skin and for applying a pharmaceutical agent to the skin, mucosa or eye without irritation. The acidic composition can further be used to remove or loosen calculus deposits from the teeth without burning or irritation of the gums.

The present invention is directed to a process and composition for treating the surface of the skin or other tissue. More particularly, the invention is directed to a process and composition for suppressing pain topically on the eye, skin or mucosa tissue.
Many substances are commonly applied to the skin, mucosa tissue and to other tissue of humans and animals to treat the surface of the skin or tissue. Typical examples of compositions that are applied to the skin include cosmetics, sunscreens and the like. Other compositions often include a pharmaceutical agent such as an antibiotic or bactericide for treating the surface of the tissue.
Topically applied compositions are generally in the form of liquids, creams, lotions and gels. In many instances, the compositions that are applied topically contain various components, which inherently cause irritation and inflammation when applied to the skin or the mucosa. The occurrence and frequency of the irritation can vary depending on the person, the specific components in the composition and the various components present.
Common symptoms of irritation from topically applied compositions include itching, stinging, burning, tingling, tightness, redness and swelling. The irritation can be due to the direct effect on the skin or the mucosa of the active ingredient or the carrier or in response to the immune system directly toward the chemicals alone or in combination with the skin components.
Many ingredients used in topically applied products are known irritants or are potentially irritating, especially for certain people with some allergies or sensitivities. Ingredients which can act as irritants include solvents, fragrances, preservatives, propellants, and pharmaceutical agents. Examples of common topical compositions, which can cause irritation, include exfolients and skin renewal agents, antiperspirants, antihistamines, anti-inflammatory agents, skin protective agents, insect repellants and sunscreens. Where more than one irritant compound is present, the effects can be additive. In addition, various components can interact with each other to cause irritation which might not occur when used alone.
Various efforts have been proposed to attempt to find methods and compositions for reducing or eliminating irritation caused by the topical application of various compositions. For example, one such method attempts to reduce the irritation caused by hydroxy acids and keto-acids in topically applied products by adding a strong alkali base metal such as sodium or potassium hydroxide. The effect of the hydroxide is to raise the pH and to reduce the acidity of the composition. However, this approach has the disadvantage of reducing the effectiveness of the hydroxy acid to penetrate the skin and to reduce the effectiveness of the acid. Other hydroxides and organic amines have also been proposed to adjust the pH of the composition. However, raising the pH using these bases also reduces the effectiveness of the composition.
A further example of methods reducing irritation caused by topically applied compositions is disclosed ion U.S. Pat. No. 5,716,625 to Hahn. This patent discloses the use of a strontium metal cation to reduce irritation. It is proposed that the cation interacts with the epidermis nerve cells to prevent or counteract the sensation of irritation by interfering with the irritation inducing components of the skin cells. The strontium cation is proposed to alter the ability of the epidermal cells to depolarize by blocking or interfering with ion channel or pump operation or by altering the transmembranal action potential. It has also been proposed that the strontium cation acts to inhibit or modify the action of skin cell protease or other irritation inducing components.
The human skin and mucosa tissue presents a complicated structural and sensory environment. The skin contains nerves and highly specific sensory cells that are specialized. These cells are developed to differentiate the stimuli leading to specific sensation such as pain. In addition, nerves in the skin are responsive to native or foreign chemicals such as proteases, prostaglandins, complement system molecules, allergens and the like. Agents that are effective in combating one stimulus are often ineffective against another stimulus.
Many pharmaceutical agents when applied topically produce a burning sensation, especially when applied to a cut or sensitive tissue. For example, various eye drops containing a pharmaceutical agent when applied to the eye result in a painful burning of the eye.
Accordingly, there is a continuing need in the industry for a method of reducing or eliminating the pain associated with the topical application of various components.
The present invention is directed to a process and composition for inhibiting pain and irritation caused by topically applied compositions. More particularly, the invention is directed to a process for treating tissue with a composition and temporarily suppressing pain of the tissue being treated.
Accordingly, a primary object of the invention is to provide a process for treating skin with a composition where the composition contains an effective amount of an anti-irritant.
Another object of the invention is to provide a process for treating cuts in the skin with a composition containing an effective amount of an anti-irritant to temporarily suppress pain and irritation of the cut.
A further object of the invention is to provide a process for introducing a solution onto the surface of the eye substantially without pain or irritation.
A still further object of the invention is to provide a process for treating mucosa with a composition containing a pharmaceutical agent and an effective amount of an anti-irritant.
Another object of the invention is to provide a process for temporarily suppressing pain and irritation by topically applying a composition containing an effective amount of an anti-irritant.
A further object of the invention is to provide a method and composition for removing calculus from tooth surfaces substantially without irritation to the gums and the tooth using an acidic solution and an effective amount of an anti-irritant.
Another object of the invention is to provide a solution containing an active component for applying topically to the skin or mucosa, where the solution contains a pain suppressing amount of saccharine.
Another object of the invention is to provide an ophthalmological solution containing a pain suppressing amount of a natural or synthetic non-nutritive sweetener.
A further object of the invention is to provide a process for topically treating skin or mucosa with a solution having a pH of about 4.0 or less and a pain and irritation suppressing amount of a synthetic sweetener.
The objects and advantages of the invention are basically attained by providing a process for treating tissue of an animal with at least one bioactive compound by providing an aqueous medium of at least one bioactive compound and at least one sweetener. The sweetener is included in an effective amount to block pain receptors temporarily in animal tissue. The aqueous medium is applied to the tissue of the animal in an effective amount to treat the tissue with the bioactive compound and to suppress pain and irritation of the tissue.
The objects of the invention are further attained by providing a process for removing calculus and other deposits from the surface of the teeth of an animal comprising the steps of: providing an aqueous medium containing an edible acid in an amount to form a solution having a pH of about 6.0 or less and at least one sweetener in an amount to suppress irritation of gum tissue. The aqueous medium is applied to the surfaces of the teeth for an effective amount of time to substantially remove calculus and deposits from the teeth.
The objects and advantages of the invention are also attained by providing a process for temporarily suppressing pain receptors and reducing irritation of the tissue of an animal comprising the steps of: providing an aqueous medium of at least one bioactive compound and at least one sweetener. The sweetener is present in an effective amount to suppress the pain receptors of the tissue and to reduce pain and irritation to the tissue caused by the aqueous medium. The tissue is contacted with the aqueous medium in an amount to treat the tissue with the bioactive compound substantially without irritation to the tissue.
The objects of the invention are further attained by providing a solution comprising a carrier, at least one bioactive component and a pain and irritation suppressing amount of a non-nutritive sweetener.
The objects, advantages and other salient features of the invention will become apparent from the following detailed description of the invention.
The present invention is directed to a process for temporarily suppressing pain and irritation by applying a composition containing an anti-irritant to the skin, mucosa, eye or other tissue. More particularly, the invention is directed to a process and composition for topically delivering a composition to a specific site on a patient where the composition contains an anti-irritant in an amount to inhibit irritation to the delivery site.
The composition of the invention in preferred embodiments contains at least one active component such as a biologically active agent, a suitable vehicle or carrier, and an anti-irritant. Preferably, the composition is an aqueous solution. Alternatively, the composition can be a dispersion, emulsion, gel, lotion or cream containing a vehicle for the various components. Typically, the primary vehicle is water. The vehicle can include other materials, such as alcohols, glycerin, mineral oils with various emulsifiers or dispersing agents as known in the art to obtain the desired consistency and viscosity.
The invention is primarily directed to a composition containing an anti-irritant agent that is capable of suppressing the pain receptors in the tissue to inhibit pain and irritation to the area being treated topically with the composition. It has been found that various natural and particularly synthetic non-nutritive sweeteners are able to provide a temporary suppression of pain and irritation to the area being treated. Although not completely understood, it is believed that the natural sweeteners and particularly the synthetic, non-nutritive sweeteners are able to block the pain receptors at the site on the tissue being treated. Patients using the compositions of the invention, when applied topically to skin, mucosa or the eye, experience a reduction in pain and irritation than would otherwise occur and without numbness or loss of feeling to the treated area.
In preferred embodiments of the invention, the anti-irritant is a synthetic non-nutritive sweetener included in the composition in an effective amount to suppress or inhibit pain and inhibit irritation caused by topically applying the composition to the skin, mucosa or other tissue. The synthetic, non-nutritive sweetener can be a commercially available sweetener such as saccharine and the salts thereof, aspartame, cyclamates, and the salts thereof, acetesulfone K, and mixtures thereof. In preferred embodiments, the non-nutritive sweetener is sodium saccharine obtained commercially as a food sweetener, such as the product available under the trademark Sweet-N-Low. The commercially available food sweeteners typically include a bulking and dispersing component such as dextrose. However, the bulking and dispersing components of the commercial sweeteners do not interfere with the anti-irritant effect of the sweetener. Sodium saccharine is generally preferred since it is readily soluble in water.
In further embodiments, the anti-irritant is a natural sweetener such as a monosaccharide, disaccharide or polysaccharide. Suitable natural monosaccharide sweeteners include glucose, fructose, arabinose, xylose, ribose, mannose, galactose, dextrose, sorbose, sorbitol, mannitol, and mixtures thereof. Suitable disaccharides include, sucrose, lactose, maltose and cellobiose. The polysaccharides can include partially hydrolyzed starch, dextrin, stevioside or corn syrup salts. The natural sweeteners can be used in combination with one or more non-nutritive sweeteners.
The composition of the invention includes a carrier capable of solubilizing or dispersing the anti-irritant and the active ingredient. Generally, the carrier is water, although other pharmaceutically acceptable carriers can be used depending on the intended use of the composition. The carrier can include various co-solvents, dispersing agents or emulsifiers as known in the art. In one embodiment, the carrier is water substantially in the absence of emulsifiers or dispersing agents. The carrier can also contain various thickening or gelling agents to obtain the desired consistency or viscosity.
In embodiments of the invention, the vehicle for topical application to the skin can include various alcohols, glycols such as glycerin, lipid materials such as fatty acids, mineral oils, phosphoglycerides, collagen, gelatin and silicone based materials. The vehicles used for compositions for treating mucosa are limited primarily by the toxicity of the vehicle to the tissue.
The anti-irritant is preferably dissolved in the carrier in an amount to provide the desired anti-irritant effect. The amount of the anti-irritant will depend on the particular anti-irritant being used, and the active ingredient responsible for the irritation since some active ingredients are more likely to cause irritation. The sensitivity of the intended tissue being treated also determines the amount of the anti-irritant in the composition.
In one embodiment of the invention, the anti-irritant is a non-nutritive sweetener and particularly the commercially available sodium saccharine. The sodium saccharine is included in the amount of about 10% to about 40% by weight based on the total weight of the composition. Generally, the sodium saccharine is included in the amount of 15% to about 30% based on the total weight of the composition. Commercially available saccharine products sold as ready-to-use sugar substitutes contain about 60% by weight saccharine, with the remaining amount made up of dextrose and other bulking, dispersing and anti-caking agents. These commercially available sodium saccharine products are used in amounts, typically about 25% to 35% by weight, to provide similar saccharine concentrations in the final product. Other non-nutritive sweeteners such as aspartame and cyclamates and salts thereof are used in similar amounts as the saccharine. In further embodiments, the non-nutritive sweetener is included in an amount to form a saturated solution.
The natural sweeteners, such as sucrose, are included in the composition in the amount of about 15% to 30% by weight based on the total weight of the composition. Generally, the natural sweetener forms a saturated solution. In preferred embodiments, the anti-irritant is an artificial non-nutritive sweetener to avoid the stickiness associated with topical applications of natural sweeteners.
The composition also contains an active compound which can be at least one bioactive ingredient in an amount to provide effective treatment of the patient in need thereof. The bioactive ingredient can be, for example, an antifungal, anti-inflammatory, antibiotic, analgesic, immunosuppressive agent, and mixtures thereof. The anti-inflammatory agents can be steroidal, non-steroidal or salicylates. Examples of anti-inflammatory agents include ibuprofen and acetaminophen. The suitable antibiotics can include aminoglycosides, cephalosporins, macrolides, monobactrams, penicillins, quinolines, sulfonamides and tetracyclines as known in the art. Examples of immunosuppressive agents include cyclosporin, azathioprine and Rho(D)immune globulin. These active ingredients are intended to be exemplary of suitable pharmaceutically active components. It will be understood that other bioactive ingredients can be used that are capable of inducing a desired response or treating a particular condition. The amounts of the active compounds in the composition are standard concentrations for topically applied components as known in the art.
In further embodiments, the composition includes a pharmaceutically acceptable or edible acid to adjust the pH below 7.0, and generally below about pH 6.0. Suitable acids include, for example, citric acid, acetic acid, ascorbic acid, malic acid, adipic acid, fumaric acid, and mixtures thereof. In embodiments of the invention, the acid functions as a bioactive compound for certain topical applications. In preferred embodiments, the acid is in the form of a citrus juice from lemons, limes, oranges, grapefruits, tangerines, tangelos, and mixtures thereof. Generally, the citrus juice is fresh squeezed juice or juice obtained from reconstituted concentrate. The most preferred citrus juice is fresh lemon juice. In further embodiments, the composition can contain a mixture of citric acid and ascorbic acid.
The acid, which can be a citrus juice, is included in an amount to provide a solution having a pH of about 2.0-6.5, depending on the desired pH for the tissue being treated. In embodiments, the composition has a pH of about 2.0-3.0 for some topical applications to the skin and mucosa. Fresh lemon juice, for example, typically has a pH of about 2.3 to 2.4.
Acidic solutions are known to generally produce a burning and irritating effect when applied to sensitive tissue such as scratches or cuts on the skin, mucosa and the eye. It has been found that the anti-irritants of the invention, and particularly sodium saccharine, has an anti-irritant effect on tissue to inhibit the irritation caused by the acid. Moreover, pH measurements of acid solutions containing varying amounts of sucrose and/or sodium saccharine have shown that the sucrose and sodium saccharine do not significantly alter the pH of the acidic solution. One aspect of the invention is based on the use of an anti-irritant agent without significantly adjusting the pH of the acidic solution. In embodiments of the invention, the pH of the composition is adjusted as necessary to dissolve a desired compound. For example, certain compounds are stable or soluble only in acid or alkaline solutions. The anti-irritant of the invention enables acidic or alkaline solutions containing compounds that are insoluble or unstable at neutral pH. The solutions can be applied to the skin or mucosa tissue substantially without irritation.
The composition of the invention is generally an aqueous solution containing an active ingredient for applying topically to the skin, mucosa or the eye. Compositions for applying topically to the skin preferably contain an antibiotic, antibacterial agent, analgesic or anti-inflammatory, and an anti-irritating amount of a natural or artificial sweetener. The composition is particularly suitable for treating minor cuts, scratches, and abrasions on the skin substantially without irritation. It has been found that an aqueous solution containing 25% to 35% by weight sodium saccharine and an acid, such as ascorbic, citric or acetic acid, can be applied to scratches and minor cuts on the skin substantially without irritation. The sodium saccharine is believed to provide a temporary suppression of the nerve endings on the skin to prevent or reduce the irritation. It has also found that lemon juice having a pH of about 2.5 containing about 30% by weight sodium saccharine can be applied to minor skin cuts substantially without the irritation normally associated with an acidic solution applied to a cut.
In a further embodiment, the composition is an aqueous ophthalmic preparation for treating the eyes where the preparation contains an effective amount of an anti-irritant. Generally, the ophthalmic preparation is an aqueous solution diluted to the desired concentration with a physiological saline solution containing potassium chloride, sodium chloride and glucose. In further embodiments, the ophthalmic preparation is a lactated Ringer""s solution. The ophthalmic preparation can be administered in the form of drops to the eye to reduce the discomfort associated with dryness and to aid in the healing of injured conjunctival and corneal tissue. The solution can contain a suitable buffering agent, surfactant and an anti-irritant amount of a natural or non-nutritive sweetener. The ophthalmic solution preferably contains at least one pharmaceutical agent.
The buffering agent is a pharmaceutically acceptable component to adjust the pH of the solution in the desired range. Suitable buffering agents include the combination of citric acid and a citrate. Other acids such as lactic, maleic and succinic acid can be used. Phosphate salts such as monosodium dihydrogenphosphate, disodium monohydrogenphosphate, monopotassium dihydrogenphosphate, dipotassium monohydrogen-phosphate, and mixtures thereof can also be used. The surfactants can be, for example, polyoxyalkylene derivatives such as the surfactants sold under the trademarks Tween-80, Tween-60 and Tween-40. The ophthalmic composition generally is adjusted to a pH of about 6.0-7.0. In further embodiments, the pH can be adjusted to below 6.0 without irritation.
The ophthalmic preparation preferably contains about 15% to 30% by weight of a non-nutritive sweetener to serve as an anti-irritant. Sodium saccharine is the preferred anti-irritant for use in ophthalmic preparations. The ophthalmic preparation preferably includes a pharmaceutical agent in standard amounts commonly delivered to the eye by topical application. The preparation is generally applied to the eye or ocular cavity by applying drops to the surface of the eye. The ophthalmic preparation preferably includes a pharmaceutical agent or active compound commonly used in ophthalmic solutions. For example, the ophthalmic solution can contain an anti-inflammatory agent, antibiotic, vasoconstrictor, antifungal, or the like, in conventional concentrations.
In a further embodiment of the invention, the composition is an oral composition effective in removing plaque and calculus deposits from the surface of teeth. Calculus deposits are generally formed of calcium phosphate and calcium carbonate that adhere to the tooth surfaces and are typically associated with inflammation and bleeding of the gums. Calculus deposits are frequently a primary cause of receding gums.
The oral composition of the invention is preferably an aqueous solution containing an edible acid and an anti-irritant. The oral composition can be used as a mouthwash or rinse or as a dentifrice in combination with brushing or other mechanical cleaning of the teeth. The edible acids generally include, for example, citric acid, ascorbic acid, acetic acid, tartaric acid, maleic acid, fumaric acid, and mixtures thereof. The acid is included in an amount to provide a pH of less than 7.0, and generally about 2.0 to 6.0, and preferably about pH 5.5 to 6.0. In a preferred embodiment, the oral composition is fresh lemon juice. In an embodiment, the oral composition has a pH of about 3.04.0. In further embodiments, the oral composition contains a mixture of citric acid and ascorbic acid in amounts to provide a pH of less than 6.0 and generally about 5.5 to 6.0.
The anti-irritant in the oral composition is preferably a non-nutritive sweetener. The preferred anti-irritant is sodium saccharine in the amount of about 20% to 30% by weight. Alternatively, the anti-irritant can be sucrose, glucose, fructose or mixtures thereof, aspartame or cyclamates. In further embodiments, the oral composition can contain a flavoring agent, a fluoride source, anti-carie agent, antibacterial agent, humectant, emulsifier, bleaching agent or solubilizing agent. Although the oral composition is preferably an aqueous solution, the solution can contain up to 20% by weight of a cosolvent, such as ethyl alcohol.
Suitable flavoring agents include natural or synthetic flavors or oils. The natural flavors include citrus oils, such as lemon oil, lime oil, grapefruit oil, fruit essences, peppermint oil, spearmint oil, clove oil, bay oil, eucalyptus oil, cinnamon oil, and wintergreen oil.
In embodiments of the invention, the oral composition is preferably an aqueous composition applied to the tooth surface either alone or in combination with mechanical application. In one embodiment of the invention, the oral composition contains fresh lemon juice and sodium saccharine having a pH of about 2.0 to 4.0. This oral composition is applied to the calculus deposits with a soft dental brush or proxy brush to brush the composition onto the calculus deposits and between the teeth for a sufficient amount of time to remove the calculus deposits. Generally, the oral composition is applied followed by neutralizing the acid in the mouth and on the tooth surface. Neutralizing the acids can be by rinsing with water or other mouth rinse to wash and remove the acid from the tooth surfaces. Alternatively, a commercially available dentifrice, such as tooth paste, can be used by brushing to neutralize and remove the acid from the tooth surfaces. Typically, the oral composition at a pH of about 2.0-4.0 effectively removes the calculus deposits without the need for mechanical abrasion or cleaning. The composition for applying directly to the tooth surfaces can include a pH adjusting agent or buffer to raise the pH to at least 5.0, and alternatively to at least pH 5.5, to reduce the effects of the acid on the enamel and dentin surfaces of the tooth. Regular cleaning of the tooth surfaces with the oral composition have shown to remove substantial amounts of calculus deposits on the teeth and to loosen the deposits. In some instances, the calculus deposits are completely removed. In other instances, the deposits are loosened so that they can be easily removed by a dentist or hygienist during routine cleaning by mechanical action. The composition is also found to be effective in preventing or reducing the amount of the calculus deposits which normally form on the teeth. A suitable oral composition is an aqueous solution containing an edible acid in an amount to provide a pH of about 2.0 to 6.0, generally about pH 5.5 to 6.0, and about 20% to about 30% by weight of an anti-irritant, such as sodium saccharine.

Process and composition for temporarily suppressing pain


A foam generator is configured such that liquid contents pumped by an internal pressure as a result of directly compressing an inverted compression receptacle, having the liquid contents stored therein, are mixed with air in a gas-liquid mixing chamber and, at the same time, directly discharged in the form of foam. That is, direct compression of the inverted compression receptacle allows the liquid contents to be instantly discharged in the form of foam, thereby further improving product responsiveness.

In general, a foam generator mixes liquid contents stored in a receptacle with air in an air and liquid mixing chamber and then forms and discharges uniform foam liquid through a filtration net. Such a foam generator is used for various purposes, such as shampoos, hair cosmetics, or cleansers used in bathrooms, kitchens, and restrooms.
A conventional foam generator is used to mix liquid contents with an appropriate amount of air and to extrude the mixture in the form of foam. In products to which such a foam generator is applied, a receptacle must be filled with compressed gas, making it technically difficult to manufacture the receptacle. The receptacle must be shaken whenever the receptacle is used. Also, in the state in which the product receptacle is inclined, the liquid filling the receptacle cannot be ejected in the form of foam, and only the compressed gas is ejected.
In order to solve the above problem, a foaming pump assembly that appropriately mixes liquid contents with external air and ejects the mixture in the form of foam without filling the foaming pump assembly with compressed air or without shaking the foaming pump assembly is disclosed in Korean Registered Utility Model No. 20-0169773 (Title of the Device: Air valve device of foam generator).
As shown in FIG. 1, the foaming pump assembly disclosed in Korean Registered Utility Model No. 20-0169773 includes a cap 1 coupled to the neck of a receptacle A having (liquid) contents stored therein in a screw coupling manner, a cylinder body 2 fixed in the cap 1, the cylinder body 2 having an air cylinder 2a having a negative pressure hole 2b formed therein and a long cylindrical liquid cylinder 2c integrally formed at the center of the lower part of the air cylinder 2a such that the (liquid) contents are introduced into the liquid cylinder 2c, a nozzle 3 installed to the cap 1 so as to be supported by the cap 1 such that one end thereof can be movable into the cylinder body 2, the nozzle 3 having an outlet 3a, through which foam is ejected, an air piston 4 having an upper part fixed to the inner circumference of the nozzle 3 and the outer circumference of a lower end disposed in tight contact with the inner circumference of the air cylinder 2a such that the air piston 4 presses the lower part of the air cylinder 2a and expands the upper part of the air cylinder 2a when the nozzle 3 is pushed, a liquid piston 6 disposed between a coil spring 5 provided at the lower part of the liquid cylinder 2c of the cylinder body 2 and the air piston 4 for elastically supporting the nozzle 3 upward and guiding the compressed air and the contents to the upper part of the air piston 4, and a ball 8 located at the bottom part of the liquid cylinder 2c of the cylinder body 2 for selectively opening and closing a liquid suction port 7. A filtration net 9 for filtering foam is disposed in the nozzle 3.
In the conventional foaming pump assembly, when the nozzle 3 is repeatedly pushed, the (liquid) contents filling the receptacle A are suctioned/pumped through the liquid cylinder 2c. At the same time, air is ejected from the air cylinder 2a. As a result, foam is generated. The foam is uniformly filtered through the filtration net 9 and is then ejected to the outside through the outlet 3a in the nozzle 3.
In the conventional foaming pump assembly, however, not only the structure for compressing and discharging air but also the structure for mixing suctioned liquid contents with the air and discharging the mixture in the form of foam are more complicated than necessary, whereby assembly productivity is lowered and costs are also increased. In addition, it is necessary for a user to receive foam discharged through the outlet 3a in the nozzle 3 with one hand while repeatedly pushing the nozzle 3 with another hand, which is inconvenient.

Foam generator for inverted compression receptacles


A radiation hardened memory element includes at least two delay elements for maintaining radiation hardness. In an example, the memory element is an SRAM cell. Both delays are coupled together in series so that if either one of the delays fails, a delay will still be maintained within the SRAM cell. The critical areas of the delays may be positioned so that a common line of sight cannot be made between each delay and a circuit node.

Static Random Access Memory (SRAM) is often used in the cache of a CPU and in digital processing circuits where speed is an important requirement. In contrast to Dynamic Random Access Memory (DRAM), SRAM does not need to be periodically refreshed.
An SRAM includes arrays of individual SRAM cells. Each SRAM cell is addressed and accessed so that it may be "read" from or "written" to. Each SRAM cell includes a pair of cross-coupled inverters that are each used to store either a "high" or "low" voltage level. The cross-coupled inverters are coupled with a pass gate, such as a transistor to bit lines, that allows the cross-coupled inverters to be read from or written to. Unfortunately, in radiation environments, such as space and aerospace, the data state held by these cross-coupled inverters and other transistors are susceptible to upset from radiation events.
Because SRAM cells are made from semiconductor materials, such as silicon, a radiation event, such as a particle strike, may induce charge. This charge, or glitch, if large enough, may cause a node within the cross-coupled inverters to change state. If the state change results in a bit-flip or a change in state of the SRAM cell, it is referred to as a Single Event Upset (SEU) or a soft error.
One method that circuit and system designers use to prevent radiation events from causing an SEU in an SRAM is to introduce a delay element in the feedback loop between the two cross coupled inverters of an SRAM cell. For example, one SRAM cell 10, in a six transistor configuration, is illustrated in FIG. 1. SRAM cell 10 includes inverter 12 cross-coupled with inverter 14. Inverter 12 includes Field Effect Transistor (FET) 16 coupled with FET 18. Inverter 14 includes FET 20 coupled with FET 22. The coupled drains of FETs 16 and 18 are coupled to a delay 24. The delay 24 is coupled to the gates of FETs 20 and 22 and it is enabled and disabled by respective delay and bypass signals communicated at delay input 25.
The SRAM cell 10, in operation, is written to and read from by data (bit) lines 26 and 28, FETs 30 and 32 (pass gates), and enable (write) input 34. When SRAM cell 10 is to be read, an enable signal is communicated to enable input 34 and it is used to open a conduction path between the drain and source terminals of FETs 30 and 32. The voltage stored by the cross-coupled inverters at nodes 36 and 38 is then communicated respectively to data lines 26 and 28. The voltages on data lines 26 and 28 are data signals, where the data signal on signal line 28 is an inverse of the data signal on signal line 26. Throughout the read, active delay 24 is enabled.
When the SRAM cell 10 is to be written to, the enable signal is communicated to enable input 34 and active delay 24 is disabled. Output drivers, also coupled to bit lines 26 and 28, are used to drive the voltages at nodes 36 and 38. For example, if the voltage at node 36 is "low" and a "high" value is to be written, a "low" voltage is communicated by the output driver to node 38. The "low" voltage at node 38 is used to drive the gates of FETs 16 and 18 so as to set the voltage at node 36 "high". After the SRAM cell 10 is written, a disable signal may be communicated to disable input 34 and the SRAM cell 10 will store the voltage at nodes 36 and 38 until a write operation is performed again. Throughout the write, active delay 24 is disabled.
Without delay 24, the SRAM cell 10 would be more vulnerable to radiation events, including particle strikes. For example, if a state change occurs on one of the nodes within SRAM cell 10, it could propagate through the SRAM cell 10. The delay 24, however, prevents an SEU by delaying the state change from propagating around the feedback element until the charge deposited from the SEU is dissipated.
An example of SEU prevention is demonstrated as follows. If the voltage at node 38 is "low", for example, an SEU induced state change may cause the voltage at node 38 to go "high". This "high" voltage will drive node 36 "low". Delay 24, however, will continue to hold the gates of FETs 20 and 22 "high" so that node 38 returns "low". Delay 24 effectively delays the switching, or response time, of the cross-coupled inverters. If the response time is greater than the time it takes for the radiation induced charge to dissipate (i.e., the recovery time), the SRAM cell 10 has been effectively radiation hardened. When the delay signal is communicated to input 25, the delay is enabled and the response time of cross-coupled inverters 12 and 14 is increased. Alternatively, when a bypass signal is communicated to input 25, the response time is decreased. The bypass signal is generally used to decrease the delay of the SRAM cell 10 when it is being written to. The delay and bypass signals are used to optimize both the write speed and radiation hardness of the SRAM cell.
Active delay 24 generally includes elements that are used to increase or decrease the delay time of the cross-coupled inverters 12 and 14. For example, as shown in FIG. 1B, active delay 24 may include a FET 46 coupled with a resistance, such as a resistor 48. The FET 46 and resistor 48 may be coupled to receive the delay and bypass signals. When a bypass signal is communicated, the voltage at node 36 may be propagated through FET 46 (bypass path) to the gates of FETs 20 and 22. If a delay signal is communicated, however, FET 46 may close and the voltage at node 36 will be delayed for a finite amount of time by resistor 48 (delay path). The response time of the SRAM cell 10 may be tailored by adding additional elements to the delay or bypass paths of the active delay 24.
Despite the effectiveness of current active delay schemes in current SRAM cells, an SRAM cell may be vulnerable to radiation events that affect multiple nodes within the SRAM cell. For example a proton strike may induce a multiple node state change in an SRAM cell. A proton strike may cause interactions with silicon nuclei that result in an effect known as heavy ion recoil. This heavy ion recoil can travel through multiple nodes within the SRAM cell. Therefore, it would be desirable to design an SRAM cell, or other memory element, that is optimized to prevent single event and soft error phenomena from multiple node state change events.

Radiation-hardened memory element with multiple delay elements


Disclosed is a new desiccant composition containing calcium chloride and a modified starch, preferably a modified corn starch. The composition contains from about 5 to about 95 percent calcium chloride and from about 5 to about 95 percent starch.

1. Field of Invention
This invention relates to desiccant containers. More specifically, this invention relates to a composition of material for use in a desiccant container comprising a combination of calcium chloride and starch.
2. Prior Art
Desiccant containers which absorb water vapor, water, liquids and the like are well known in the art. Generally, these containers are comprised of a water or water vapor permeable packaging material formed from fibrous or film products securely sealed together at the edges of the packaging. The packaging material encapsulates a desiccant material, such as silica gel. The volume of water or water vapor absorbed by the desiccant container is generally determined by the absorbent capacity of the desiccant material contained within the container.
One type of desiccant container absorbs both water vapor and liquid water by permitting both to pass through the packaging material to be absorbed by the desiccant material. In some circumstances, the packaging material for this type of product dissolves to permit the desiccant material contained within the desiccant container to have direct contact with the liquid.
Another type of desiccant container absorbs water vapor but not liquid water. The packaging material for this type of desiccant container is designed to prevent water absorbed within the desiccant container as water vapor from being released from the desiccant container in the form of liquid water.
There are many common products that are utilized as desiccating agents. Among the most common used include silica gel, calcium sulfate, calcium fluoride, activated charcoal, molecular sieves, lithium chloride, calcium chloride and other such products. A common list of these drying agents is contained, for example, in Kirk-Othmer, Encyclopedia of Chemical Technology, Volume 7, pages 378-398. Common desiccating agents for use in conventional desiccant containers are also disclosed in U.S. Pat. No. 5,114,003, which discloses the use of a montmorillonite clay, silica gel, molecular sieve, calcium oxide, calcium sulfate and calcium chloride. The use of silica gel, alumino silicate, alumina, activated charcoal and molecular sieves as desiccating agents are disclosed in U.S. Pat. No. 4,464,261.
Commercial grade calcium chloride is a widely used desiccant due to its low cost and high degree of hygroscopicity. Calcium chloride compacted in the form of particles or beads is used as a drying agent, for example, in U.S. Pat. No. 3,923,944.
Mixtures and combinations of other materials have been combined with calcium chloride to form desiccating products. For example, polyethylene glycol was mixed with calcium chloride to form a desiccant product in U.S. Pat. No. 3,779,936. In addition, U.S. Pat. No. 3,334,468 discloses the use of sodium chloride or sodium carbonate with calcium chloride. Further, the combination of calcium chloride with magnesium, lithium or ammonium salts is disclosed, for example, in U.S. Pat. No. 3,885,926. The use of calcium chloride with a metal, for example, iron fillings, is disclosed in U.S. Pat. No. 1,798,862. Further, the use of activated carbon with calcium chloride as a desiccant product is disclosed in U.S. Pat. No. 2,027,093.
U.S. Pat. No. 3,390,511 discloses the use of calcium chloride placed on a carrier material for use as a gas dryer desiccant. The preferred material that is utilized as the carrier for the calcium chloride is sodium chloride. See also, U.S. Pat. No. 3,334,468. The desiccant product in U.S. Pat. No. 3,390,511 preferably comprised about 90 to 97 percent sodium chloride as the carrier and about 10 to about 3 percent calcium chloride. In addition, sodium dichromate and trisodium phosphate in minor amounts may be included in the product. While the preferred carrier for the calcium chloride was sodium chloride, other disclosed carriers included sugar, potassium chloride, potassium nitrate, sodium nitrate and starch. See column 3, line 33. The percentage of calcium chloride used in this product was 10 percent or less, because the major component of the product was the carrier.
One of the problems in the utilization of calcium chloride as a desiccating agent is that when the water is absorbed, it forms a liquid mixture on the surface of the calcium chloride. This is discussed in U.S. Pat. No. 3,334,468. With conventional desiccant products this liquid may leak which can cause problems, for example, if the desiccant product is used in storage containers.
While these references disclose the use of calcium chloride as a desiccant either alone or combined with a number of different compositions, there is still the need for improved desiccant products utilizing calcium chloride.
Therefore it is an object of this invention to disclose a desiccant composition containing calcium chloride as its major component.
It is a still further object of this invention to disclose a desiccant composition containing calcium chloride mixed with a significant amount of starch to form the desiccant composition.
It is a still further object of the invention to disclose a desiccant composition contained within a packaging material, wherein the desiccant composition is a combination of calcium chloride and starch, preferably a modified starch.
It is a still further object of this invention to disclose a desiccant composition containing calcium chloride where water absorbed by the calcium chloride does not leak from the desiccant container.
It is a still further object of this invention to disclose a desiccant composition contained within a packaging material wherein the desiccant composition prevents leakage of water from within the package by use of a starch, preferably a modified starch.
These and other objects and features of the present invention will become apparent to those skilled in the art from a consideration of the following detailed description, drawings and claims. The description, along with the accompanying drawings, provides a selected example of the construction of the product and process to illustrate the invention.


A semiconductor laser device has an active layer which is divided into two regions in the direction of a resonator, i.e., a light-amplifying region and a saturable absorber region. The light-amplifying region and the saturable absorber region are produced to allow the semiconductor laser device to be in a bistable state. For the light-amplifying region and the saturable absorber region respectively, p-electrodes are separately and independently formed. N-electrodes are provided in relation to the p-electrodes. From one of the p-electrodes, a current which is modulated with noise added thereto is injected.

1. Field of the Invention
The present invention relates to a semiconductor laser, a semiconductor laser driver and a method of driving a semiconductor laser. In particular, the present invention relates to a semiconductor laser, a semiconductor laser driver and a method of driving a semiconductor laser reducing feedback-induced noise by a modulated optical output.
2. Description of the Background Art
Semiconductor lasers are superior in monochromaticity and directivity and can provide a necessary spot size which is small enough to read a pit on an optical disk, and are accordingly used as a light source for the optical disk. For such a high-density recording medium as DVD (Digital Versatile Disk) having a multi-layer structure, a high output of at least 8 mW is necessary for reading and thus conventional red semiconductor lasers cannot be used for the high-density recording medium.
A nitride semiconductor laser with a short wavelength and a high output power is appropriate for the high-density recording medium like the DVD, and thus development of the nitride semiconductor laser, which is to be used as an effective laser for a laser pickup device instead of the red semiconductor laser, is being in progress.
With such a pickup device, light emitted from a laser is reflected from a surface of a disk which is a recording medium or from an optical system, and then the emitted light is partially returned to the laser. The light returned to the laser is called "feedback light." The feedback light and the light emitted from the laser interfere with each other, resulting in noise generation when information is reproduced.
An effective method for reducing "feedback-induced noise" is to periodically change the intensity of an optical output and thereby reduce the coherency of the semiconductor laser. An optical output with its light intensity periodically changed is hereinafter referred to as "modulated optical output."
In order to produce the modulated optical output, a technique of intentionally causing "self pulsation" of the laser is generally employed. The self pulsation can be caused by providing, for example, the laser with such a special structure as described below.
Around a gain region within an active layer that is called light-amplifying region, a region having a light-absorbing effect that is called saturable absorber region is formed. Accordingly, on carriers in the active layer and oscillating light, the Q-switching effect is exerted by the saturable absorber region to cause the self pulsation.
Thus, a constant current equal to or larger than a lasing threshold can be injected into the active layer of the laser with the above-described structure so as to intentionally cause the self pulsation and thereby obtain a modulated optical output.
FIG. 11 is a cross-sectional view exemplarily showing a structure of a conventional self-pulsating semiconductor laser.
The conventional self-pulsating semiconductor laser device shown in FIG. 11 includes, on an n-type GaAs substrate 103, an n-type GaAs buffer layer 104, an n-type AlGaInP cladding layer 105, a GaInP active layer 106, a p-type AlGaInP cladding layer 107, a p-type GaInP intermediate layer 108 and a p-type GaAs contact layer 109 that are deposited successively in this order.
P-type AlGaInP cladding layer 107, p-type GaInP intermediate layer 108 and p-type GaAs contact layer 109 constitute a stripe ridge 110, and n-type GaAs buried layers 111 and 112 are provided respectively on lateral sides of ridge 110. A p-electrode 101 is provided on the front side of the device and an n-electrode 102 is provided on the back side thereof that are not divided.
This device has ridge 110 in cladding layer 107 located on active layer 106 so as to produce regions into which currents of different amounts respectively are injected, and thus saturable absorber regions 114 and 115 are provided around a light-amplifying region 113 (gain region) to achieve the self pulsation.
Here, a current is injected from p-electrode 101 through the inside of ridge 110 into the active layer 106 and then passed to n-electrode 102. The current is chiefly injected into a region directly below the ridge that accordingly functions as a light-amplifying region 113 while a smaller amount of current is injected into regions 114 and 115 that accordingly function as saturable absorber regions. In this way, the self pulsation is caused.
For such a device, various parameters of the device structure that can cause the self pulsation, for example, the width of the ridge structure and the thickness of the cladding layer, should be determined. Moreover, unless the device is precisely produced to satisfy the determined conditions, the self pulsation is impossible to achieve.
A conventional nitride semiconductor laser device is shown next that has a region into which a smaller amount of current is injected, i.e., saturable absorber region, as the conventional device shown in FIG. 11.
FIG. 12 is a cross-sectional view showing a structure of the conventional nitride semiconductor laser device disclosed in Japanese Patent Laying-Open No. 2000-286504.
The conventional nitride semiconductor laser device shown in FIG. 12 is produced by depositing, on a sapphire substrate 121, an n-type contact layer 122 of GaN having a thickness of 4.5 μm, an n-type cladding layer 123 of AlbGa1−bN having a thickness of 0.8 μm, an active layer 124 having a multiple quantum well structure, a p-type cladding layer 125 of AlaGa1−aN having a thickness of 0.8 μm, n-type current-constricting layers 126 and 127 of AlcGa1−cN, and a p-type contact layer 128 of GaN having a thickness of 0.05 μm.
P-type cladding layer 125 is constituted of a flat portion 125a formed to cover a surface of active layer 124 and a two-stripe portion constituted of a lower stripe portion 125b and an upper stripe portion 125c protruding upward from the central part of flat portion 125a. The top surface of the two-stripe portion contacts p-type contact layer 128 and the lateral sides thereof contact n-type current-constricting layers 126 and 127. Here, the width of upper stripe portion 125c is made smaller than the width of lower stripe portion 125b.
On n-type contact layer 122, an n-electrode 129 is formed. On p-type contact layer 128, a p-electrode 130 is formed. In active layer 124, well layers of InxGa1−x N having a thickness of 8 nm and barrier layers of InyGa1−yN having a thickness of 16 nm are stacked alternately. In the device structure shown in FIG. 12, n-type current-constricting layers 126 and 127 made of AlcGa1−cN has a refractive index which is made smaller than that of p-type cladding layer 125 made of AlaGa1−aN (0<a<c≦1) and thereby a real-refractive-index waveguide structure is implemented.
This conventional nitride semiconductor laser device efficiently uses, as a saturable absorber region, the region into which a smaller amount of current is injected. Then, the ridge is formed so that the width of the ridge for current injection and the width of a region where a transverse mode of laser light spreads are different from each other. Neither P-electrode 130 nor n-electrode 129 is divided. P-electrode 130 is formed on the top surface of p-type contact layer 128 while n-electrode 129 is formed on the top surface of n-type contact layer 122 and they are provided as a pair of electrodes.
According to the above-discussed method, a region into which a smaller amount of current is injected is used as the saturable absorber region. Alternatively, a saturable absorber region and a light-amplifying region may be provided in advance in fabricating the device. In this case, the carrier lifetime and the differential gain are adjusted by adding impurities so as to satisfy the parameter conditions for causing the self pulsation and accordingly, a layer serving as the saturable absorber region and a layer serving as the light-amplifying region are produced. Such a conventional self-pulsating semiconductor laser is shown in FIG. 13.
FIG. 13 is a cross-sectional view showing a structure of a self-pulsating semiconductor laser device disclosed in Japanese Patent Laying-Open No. 8-204282.
The conventional self-pulsating semiconductor laser device shown in FIG. 13 includes an n-electrode 141, an n-type GaAs substrate 142, an n-type AlGaInP cladding layer 143, an n-type AlGaInP saturable absorber layer 144, an n-type AlGaInP cladding layer 145, an AlGaInP active layer 146, a p-type AlGaInP cladding layer 147, a p-type AlGaInP saturable absorber layer 148, a p-type AlGaInP cladding layer 149, n-type GaAs current-blocking layers 150 and 151, a p-type GaAs contact layer 152 and a p-electrode 153.
This laser device has saturable absorber layers 144 and 148 in itself that have the light-absorbing effect, and carriers in these saturable absorber layers 144 and 148, and carriers and oscillating light in active layer 146 which is a light-amplifying region cooperate with each other to cause self-pulsation. The laser satisfying the self-pulsating condition can produce an optical output with a periodical change in intensity, which is achieved by injection of direct current into the light-amplifying region.
When the above-discussed method is used to cause the self pulsation, however, the composition of the device and conditions of the structure thereof are limited. For example, in order to fabricate saturable absorber layers 144 and 148 and active layer 146 which is a light-amplifying region by adding impurities thereto, the carrier lifetime and the differential gain of the saturable absorber regions and the light-amplifying region should be adjusted.
According to the methods as described above, the intensity of an optical output is periodically changed by using the self pulsation. There is another method for producing a modulated optical output, which is specifically a high-frequency superimposition method according to which a current modulated by the high frequency is injected. For example, according to a technique disclosed in Japanese Patent Laying-Open No. 60-35344, pulsed lasing is caused by superimposing a modulation current of high frequency on an operating current near a lasing threshold of a laser.
FIG. 14 illustrates operational characteristics of the conventional semiconductor laser disclosed in Japanese Patent Laying-Open No. 60-35344.
In FIG. 14, (a) indicates an injection-current to optical-output characteristic curve of the conventional semiconductor laser, with the horizontal axis representing an injection current and the vertical axis representing an optical output produced according to the injection current. To the semiconductor laser having such an injection-current to optical-output characteristics, a current modulated in a range between a current value smaller than a lasing threshold Ith and a current value higher than the lasing threshold Ith as indicated by (b) in FIG. 14 is injected, so that an optical output of the semiconductor laser is modulated as indicated by (c) in FIG. 14.
In this case, it is unnecessary to cause the self pulsation state and thus unnecessary to form a structure having the saturable absorber region and light-amplifying region in fabricating the device. Moreover, the amplitude of the modulation current to be injected can be increased to increase the amplitude of a resultant modulated optical output.
There is a further method of producing a modulated optical output, according to which a semiconductor laser in a bistable state with a light-amplifying region and a saturable absorber region is provided and a current or voltage to be applied to the saturable absorber region is varied.
FIG. 15 shows characteristics of an injection current injected into a light-amplifying region vs. an optical output of a conventional semiconductor laser in a bistable state.
As shown in FIG. 15, the conventional semiconductor laser in the bistable state exhibits hysteresis characteristics in the relation between the injection current and the optical output. The solid line indicated by A is herein referred to as lower hysteresis path and the dotted line indicated by B is herein referred to as upper hysteresis path.
Referring to FIG. 15, as a current is injected into the light-amplifying region only, the optical output increases from P4 through P1 along the path indicated by A. At this time, the carrier density in the saturable absorber region increases because of absorption of light generated in the light-amplifying region, and accordingly, the light-absorbing effect in the saturable absorber region decreases.
Then, as the amount of a current injected into the light-amplifying region increases, the light-absorbing effect reaches saturation. Then, when the injection current attains IthON, the optical output suddenly increases from P1 to P2. This IthON is herein referred to as rising threshold of hysteresis.
Then, as the amount of the injection current is decreased, the optical output gradually decreases from P2 through P3 along the path indicated by B, since the saturable absorber region cannot immediately recover the light-absorbing effect and thus the optical output does not dramatically decrease. At this time, as the carrier density as well as the optical output decrease, the light absorbing effect of the saturable absorber region is recovered.
Then, as the amount of the injection current injected into the light-amplifying region is decreased, the light-absorbing effect is sufficiently recovered so that the optical output sharply decreases from P3 to P4 when the injection current reaches IthOFF. IthOFF is herein referred to as falling threshold of hysteresis.
The shape of the hysteresis paths changes according to voltage application or current injection to the saturable absorber region. When a voltage is applied to or a current is injected into the saturable absorber region, the carrier density increases and the light-absorbing effect decreases. Then, the whole hysteresis shifts to a region where the injection current is lower, so that IthON decreases. In this way, by increasing/decreasing the light-absorbing effect of the saturable absorber region, the lasing threshold can be changed. A conventional driving method of this type as described above is shown in FIGS. 16 and 17.
FIG. 16 is a schematic cross-sectional view showing a structure of a conventional semiconductor laser device in a bistable state disclosed in Japanese Patent Laying-Open No. 2-137383.
The conventional bistable semiconductor laser shown in FIG. 16 is a transverse-mode-controlled semiconductor laser of AlGaAs/GaAs formed on a GaAs substrate. One of electrodes of the laser is divided to provide a light-amplifying region 161 and a saturable absorber region 162 in an active layer 163. Then, according to voltages V1 and V2 applied to saturable absorber region 162, a lasing threshold current injected into light-amplifying region 161 is varied. In other words, a bias current IB applied to light-amplifying region 161 is set to an intermediate value of lasing thresholds according to voltages V1 and V2, and a signal voltage V which changes between V1 and V2 is applied to saturable absorber region 162.
FIG. 17 shows an injection current—optical output characteristic curve of the conventional bistable semiconductor laser shown in FIG. 16.
Since saturable absorber region 162 which is a loss for oscillating light is provided in active layer 163, the optical output non-linearly increases at a current value, when a current is injected into light-amplifying region 161 only. This lasing threshold current Ih1 or Ih2 changes according to the amount of light absorbed in saturable absorber region 162. The threshold current decreases as the amount of absorbed light increases. When the voltage applied to the saturable absorber region increases from V1 to V2 (V1<V2), the amount of absorbed light in saturable absorber region 162 accordingly increases so that the lasing threshold current decreases from Ih1 to Ih2.
Thus, as shown in FIGS. 16 and 17, a certain bias current IB (Ih2<IB <Ih1) is injected into light-amplifying region 161 while a signal voltage V changing from V1 to V2 is applied to saturable absorber region 162, so that the lasing threshold current varies between Ih1 and Ih2 to produce a modulated optical output P.
The conventional art shown in FIGS. 11-13 according to which a modulated optical output is produced by using self pulsation has a problem that the composition and structure of the device are limited in fabricating the device.
If the composition in fabricating the device is utilized to provide a saturable absorber region and a light-amplifying region, the ratio between the saturable absorber region and the light-amplifying region in terms of carrier lifetime as well as in terms of differential gain must be adjusted. However, the range of parameters satisfying the self pulsation condition is narrow so that the freedom of fabrication is lessened. In particular, the nitride semiconductor laser shown in FIG. 12 confronts a serious problem that the value of the differential gain cannot be changed to a great degree due to characteristics of the nitride.
In general, the balance of the carrier density between the saturable absorber region and the light-amplifying region determines whether the semiconductor laser enters a self-pulsating state or bistable state. The balance can be adjusted by using the ratio in terms of the length in the direction of the resonator, the ratio in terms of the carrier lifetime and the ratio in terms of the differential gain, between these regions. In a laser in the self-pulsating state, the carrier lifetime of the light-amplifying region should be longer than that of the saturable absorber region and the differential gain of the light-amplifying region should be smaller than that of the saturable absorber region. Then, it is necessary that the ratio in terms of the differential gain and the ratio in terms of the carrier lifetime are in specific ranges respectively.
Specific values of these parameters vary depending on characteristics of a semiconductor. For a nitride semiconductor laser, the ratio of the differential gain between the saturable absorber region and the light-amplifying region must be made larger than that of a GaAs-based red semiconductor laser for example. It is noted that, if there is a greater difference between the saturable absorber region and the light-amplifying region in terms of the gradient of a gain characteristic curve with respect to the carrier density, namely the differential gain, the self pulsation is more easily caused.
More specifically, a greater gradient of a gain characteristic curve with respect to the carrier density in the saturable absorber region makes it possible to change the carrier density with less absorption of light. Accordingly, the carrier density can be changed easily. A great change in carrier density in the saturable absorber region causes a change in light-absorbing effect. For the nitride semiconductor laser, however, it is extremely difficult to provide different differential gains respectively of the saturable absorber region and the light-amplifying region due to characteristics of the nitride.
FIG. 18 shows gain characteristic curves in a saturable absorber region and a light-amplifying region of semiconductor lasers. The solid line represents gain characteristics of a GaAs semiconductor laser and the broken line represents gain characteristics of a GaN semiconductor laser.
Carriers of the GaN semiconductor laser have a larger effective mass than that of carriers of a red semiconductor laser. Regarding the GaN semiconductor laser, as shown in FIG. 18, the difference in gradient between the section of the gain characteristic curve in the saturable absorber region (absorbing region) and that in the light-amplifying region (gain region) is smaller than that of the GaAs semiconductor laser which is a red semiconductor laser. Therefore, the ratio between differential gains respectively in those regions represented by the inclination of the gain characteristic curve is approximately 1 and thus the laser cannot satisfy the self-pulsating condition. Moreover, the nitride semiconductor laser including the GaN semiconductor laser has a problem that it is difficult to change the differential gain by addition of impurities, in contrast to the red semiconductor laser.
For the reason above, it is difficult to produce the nitride semiconductor laser by adjusting the carrier lifetime and the differential gain so as to allow the saturable absorber region and the light-amplifying region to satisfy the self-pulsating condition. No method has been found to surely cause the self pulsation.
In addition, as shown in FIG. 12, when the ridge is provided in the structure of the nitride semiconductor laser so as to produce regions into which different amounts of currents are injected and thereby produce a saturable absorber region and a light-amplifying region, numerous and detailed conditions in terms of the structure, such as the width and thickness of the ridge, the thickness of the multi-layer along the boundary of the ridge, the thickness of the cladding layer and etching conditions, must be optimized. Moreover, technique for precisely fabricating the device under the resultant conditions is necessary.
Then, in order to achieve the self pulsation by the structure as shown in FIG. 12, many conditions should be defined first. Even if the conditions are established, there remains a problem that the yield of products is poor due to unsatisfactory technique of fabricating the devices. Thus, regarding the nitride semiconductor laser, there has been no method for manufacturing a laser device producing the self-pulsating state.
Regarding the method as shown in FIG. 14 that is a high-frequency superimposing method for obtaining a modulated optical output without using the self-pulsating state, a great amplitude of a modulation current to be injected is necessary for producing an optical output with an amplitude required for achieving the effect of reducing noise. A resultant problem is that, when a great optical output which is necessary to be applied to a pickup device for a high-density recording medium is produced, power consumption and generated heat increases.
Further, regarding the method as shown in FIG. 15 of increasing/decreasing the voltage to be applied to the saturable absorber region of a bistable semiconductor laser and increasing/decreasing the resistance thereof so as to adjust the lasing threshold of the laser and thereby produce a modulated optical output, it is necessary to apply a voltage or current of a large amplitude to the saturable absorber region in order to produce an optical output of a large amplitude which is enough to reduce feedback light. However, if the voltage or current of a large amplitude is applied to the saturable absorber region, a high voltage or current must be applied accordingly.
Then, when a modulated optical output is to be produced by the method as shown in FIG. 15, it is likely that the saturable absorber region saturates and thus an optical output has a small change in intensity. As a result, the optical output has a small amplitude and further, a pulsed optical output is hard to produce. Accordingly, the coherence is difficult to reduce, which lowers the effect of removing feedback-induced noise.
The problems of conventional techniques discussed above are summarized as follows.
For such a high-density recording medium as DVD which has a multi-layer structure, an output of at least 8 mW is required even for reading. Therefore, conventional GaAs-based self-pulsating semiconductor lasers cannot be used for such a medium.
Instead of the conventional semiconductor lasers, a nitride semiconductor laser is now being developed for use as a next-generation device. Although the nitride semiconductor laser produces a high output, this laser is difficult to produce due to a narrow range of conditions for achieving the self-pulsating state. For a conventional semiconductor laser having a ridge in its structure for providing a saturable absorber region and thereby producing the self-pulsating state, it is difficult to specify conditions of the structure. Moreover, the self-pulsating state cannot be produced unless the device is precisely fabricated, and thus the yield is poor.
For a conventional semiconductor laser into which an injection current modulated to be temporarily lower than the lasing threshold is injected so as to obtain a pulsed optical output, if the maximum value of the current is increased for producing an optical output having an amplitude which is large enough to reduce feedback-induced noise, the amplitude of the modulation current must be increased, resulting in a problem of a greater load on a modulating circuit.
Moreover, for a conventional semiconductor laser for which a voltage to be applied to the saturable absorber region of the semiconductor laser in the bistable state is increased/decreased in order to modulate an optical output, the lasing threshold of the laser must be switched with a wide range for producing a high optical output necessary for a pickup device of a high-density recording medium. Then, as the lasing threshold is increased, the value of current to be injected into the light-amplifying region should be increased.

Semiconductor laser, semiconductor laser driver and method of driving semiconductor laser reducing feedback-induced noise by modulated optical output


The present invention is a method and apparatus which provides a shared modem resource to PCs connected through a local area network and to off-network PCs. In particular, the present invention is an intelligent LAN modem node which combines the attributes of a local area network node, an intelligent operating personal computer and one or more modems constructed in a dedicated fashion. The LAN modem node operates as a standalone node on a LAN to allow the shared resources of modem communication for the other PCs on the network and off-network PCs without tying up any of the PCs on the network for modem communications. The LAN modem node allows the PCs on the LAN to communicate with off-LAN devices such as mainframe computers, off-site printers, minicomputers, other local area networks and the like. The LAN modem node also gives off-LAN personal computers access to network resources.

Modem (modulator/demodulator) communications is a well known method of asynchronous serial data communications between two computers or other types of electronic equipment. In a typical environment, a modern modem is connected to a local personal computer (PC) through a serial communications link. The modem is then connected through a public telephone network to a remote location in which a corresponding modem is also connected. The corresponding modem is also connected to a remote computer such as a personal computer through a serial communications link. This allows direct communication between the local personal computer and the remote personal computer over the telephone network. The two modems handle the conversion of digital data into voice band signals for transmission through the telephone network in a full duplex fashion following a variety of CCITT telecommunications standards.
A local area network (LAN) connects a number of personal computers and peripherals together for sharing information and resources. LANs can be connected in a variety of topologies (star, bus, token ring, etc.), operate at different speeds and protocol levels (Ethernet, Arcnet, etc.) use a variety of packet protocols IPX (Internetwork Packet Exchange), TCP/IP (Transmission Control Protocol/Internet Protocol), etc.), all under the control of a variety of network operating systems (Novell Netware, UNIX, etc.).
Typically a PC connected to a LAN communicates with off-LAN computers through a dedicated modem attached only to that PC. The dedicated modem communication does not go through the LAN but rather from the PC through the modem, over a telephone network to the remote computer. Software has been made available which allows a second PC on the network to communicate through the LAN to the modem attached to the first PC for communication to an off-LAN computer having its own dedicated modem. That software allows the second PC to use the modem attached to the first PC to communicate to the off-LAN or remote computer by transferring control and data information over the LAN to the modem attached to the first PC to accomplish the remote communication. This is a cumbersome and expensive method of sharing modem communication through a LAN because the first PC having the modem attached is effectively unavailable for users while modem communication with a non-modem-PC is in effect.
There is therefore a need in the art for special purpose intelligent LAN modem nodes which allow PCs on a LAN to share modem resources for off-LAN communications and which also allows off-LAN PCs access to network resources without tying up any PCs on the network.

Intelligent local area network modem node


Disclosed is an optical inspection system for inspecting the surface of a substrate. The optical inspection system includes a light source for emitting an incident light beam along an optical axis and a first set of optical elements arranged for separating the incident light beam into a plurality of light beams, directing the plurality of light beams to intersect with the surface of the substrate, and focusing the plurality of light beams to a plurality of scanning spots on the surface of the substrate. The inspection system further includes a light detector arrangement including individual light detectors that correspond to individual ones of a plurality of reflected or transmitted light beams caused by the intersection of the plurality of light beams with the surface of the substrate. The light detectors are arranged for sensing the light intensity of either the reflected or transmitted light.

The present invention relates to apparatus and methods for inspecting the surface of a substrate such as reticles, photomasks, wafers and the like (hereafter referred to generally as photomasks). More particularly, the present invention relates to an optical inspection system that can scan such a substrate at a high speed and with a high degree of sensitivity.
Integrated circuits are made by photolithographic processes, which use photomasks or reticles and an associated light source to project a circuit image onto a silicon wafer. The presence of defects on the surfaces of the photomasks is highly undesirable and adversely affects the resulting circuits. The defects can be due to, but not limited to, a portion of the pattern being absent from an area where it is intended to be present, a portion of the pattern being present in an area where it is not intended to be, chemical stains or residues from the photomask manufacturing processes which cause an unintended localized modification of the light transmission property of the photomask, particulate contaminates such as dust, resist flakes, skin flakes, erosion of the photolithographic pattern due to electrostatic discharge, artifacts in the photomask substrate such as pits, scratches, and striations, and localized light transmission errors in the substrate or pattern layer. Since it is inevitable that defects will occur, these defects have to be found and repaired prior to use. Blank substrates can also be inspected for defects prior to patterning.
Methods and apparatus for detecting defects have been around for some time. For example, inspection systems and methods utilizing laser light have been introduced and employed to various degrees to scan the surface of substrates such as photomasks, reticles and wafers. These laser inspection systems and methods generally include a laser source for emitting a laser beam, optics for focussing the laser beam to a scanning spot on the surface of the substrate, a stage for providing translational travel, collection optics for collecting either transmitted and/or reflected light, detectors for detecting either the transmitted and/or reflected light, sampling the signals at precise intervals and using this information to construct a virtual image of the substrate being inspected. By way of example, representative laser inspection systems are described in U.S. Pat. No. 5,563,702 to Emery et al., U.S. Pat. No. 5,737,072 to Emery et al., U.S. Pat. No. 5,572,598 to Wihl et al., and U.S. Pat. No. 6,052,478 to Wihl et al., each of which are incorporated herein by reference.
Although such systems work well, there are continuing efforts to improve their design to provide greater sensitivity and faster scanning speeds. That is, as the complexity of integrated circuits has increased, so has the demand on the inspection process. Both the need for resolving smaller defects and for inspecting larger areas have resulted in much greater magnification requirements and in much greater speed requirements, for example, in terms of number of pixels (picture elements) per second processed.
In view of the foregoing, there is a need for improved inspection techniques that provide increased scanning speeds.

Multiple beam inspection apparatus and method