A photolithography method, including the steps of: S1) depositing, on the upper surface of a wafer, a chemically-amplified resist; S2) exposing the resist to a sensitizing radiation through a mask, to generate acid compounds in the exposed regions; S3) heating the resist, to have the acid compounds react with dissolution-inhibiting groups; and S5) developing the resist; and including, after step S3, a step of neutralization, S4, of the acid compounds which have not reacted at step S3.

1. Technical Field
The present disclosure relates to a photolithography method, and more specifically to a photolithography method using a chemically-amplified resist.
2. Discussion of Related Art
In certain integrated circuit manufacturing technologies corresponding to particularly high integration levels, sensitizing radiations in the deep ultraviolet range at a wavelength smaller than or equal to 250 nm have to be used during photolithography steps. For example, KrF excimer lasers are used for 248-nm wavelengths and ArF excimer lasers are used for 193-nm wavelengths. Current resists, for example resists of novolak/naphtoquinone diazide type, cannot be used for such wavelengths since they absorb the radiation and the resist is not sensitized across its entire thickness. A solution is to use chemically-amplified resists.
Chemically-amplified resists are materials capable of generating an acid compound in regions exposed to a radiation, for example, an ultraviolet radiation, and to change solubility in a development solution, by reaction with the acid compound, in exposed regions with respect to non-exposed regions.
Chemically-amplified resists comprise polymer chains intrinsically soluble in a determined development solution, generally an alkaline development solution. Resists soluble in an alkaline development solution for example comprise polymer chains supporting —OH or —COOH functions. The polymer chains are made insoluble in the development solution by dissolution inhibitors incorporated in the resist. Such dissolution inhibitors for example are groups bonded to the polymer chains by acid functions —OH and —COOH of these chains. The dissolution-inhibiting groups for example are hydrophobic groups in the case where the development solution is an aqueous solution. Chemically-amplified resists further comprise precursors of compounds capable of deactivating dissolution inhibitors. Such resists are called chemically-amplified resists since a same precursor produces a compound capable of deactivating several dissolution inhibitors.
In the case where a KrF excimer laser is used as sensitizing radiation source, resists having as a backbone a polyhydroxy styrene functionalized by lateral groups are generally used. In the case where a radiation source with a sensitization of lower wavelength is used, for example, an ArF excimer laser, resists having an alicyclic, monocyclic, or polycyclic hydrocarbon structure are preferably used, compounds comprising aromatic groups and many unsaturated bonds having too high a radiation absorption to enable the creation of high-resolution patterns.
The precursors of compounds capable of deactivating dissolution inhibitors for example are acid compound precursors.
Such chemically-amplified resists are for example formed of 95% of polymer chains and 5% of acid compound precursors. Acid compound precursors for example are onium salts, for example triphenylsulfonium salts or iodonium salts. Sulfonates may also be used, for example, imidosulfonates or oximesulfonates, diazodisulfones, disulfones, or o-nitrobenzyl sulfonates.
FIGS. 1A-1C and 2A-2B illustrate successive steps of a conventional photolithography method using a chemically-amplified resist of the above-described type.
FIG. 1A is a cross-section view illustrating a step of deposition, on the upper surface of a wafer 1, of a chemically-amplified resist layer 3. The resist deposition step may be preceded by a step of deposition of a coupling agent, for example, hexamethyldisilazane (HMDS), intended to improve the bonding of resist 3 to the upper surface of wafer 1. The resist deposition is then performed by centrifugation of the resist dissolved in a solvent. Once deposited, the resist is dried and submitted to a heating enabling to increase its density and to relax the stress present therein.
After the resist has been deposited, as illustrated in FIG. 1B, the resist is exposed to a sensitizing radiation. The resist exposure is performed through a mask 5 enabling to define exposed regions 7 and non-exposed regions 9 of the resist. In exposed regions 7 of the resist, the sensitizing radiation causes the generation of acid compounds by the acid compound precursors.
After the resist exposure, at the step illustrated in FIG. 1C, the resist is heated. The heating of the resist causes a reaction between the acid compounds, generated during the exposure step, and the polymer chain dissolution-inhibiting groups. The resist heating temperature to cause the reaction between acid compounds and dissolution-inhibiting groups depends on the group activation energy. This temperature is generally greater than approximately 90° C., and preferably ranges between 100 and 140° C. An acid compound for example reacts with a few hundreds of dissolution-inhibiting groups. When attacked by acid compounds, the dissolution-inhibiting groups separate into polymer chains. The reaction causes a degassing and a rearrangement of the polymer chains, which results in a decrease in the thickness of exposed regions 7 of the resist, as shown in FIG. 1C. During this resist heating step, the polymer chains, partially or totally freed of their dissolution-inhibiting groups, become soluble again into the alkaline development solution.
During the step of heating after exposure, acid compounds diffuse towards the non-exposed resist regions. To limit this parasitic diffusion phenomenon, a solution is to use chemically-amplified resists having dissolution inhibiting groups of low activation energy. The resist heating temperature can thus be decreased, for example, to a value approximately ranging from 80 to 90° C.
It should be noted that the acid compounds photogenerated in the resist regions exposed to the sensitizing radiation must absolutely not be neutralized before having been able to play their dissolution inhibitor deactivation role. All possible precautions are thus taken to avoid for the exposed and non-developed resist to be contaminated by alkaline compounds, amines, or organic compounds. The steps illustrated in FIGS. 1A to 1C are thus carried out under an atmosphere protected from such contaminants. In particular, these steps are carried out in photolithography equipment capable of filtering compounds such as alkaline compounds, amines, or organic compounds. The content of such compounds in the atmosphere is further strictly controlled in the clean room area where the photolithography equipment is installed, and where wafers covered with exposed and non developed resist may be momentarily stored.
A next step comprises developing the resist. This may performed according to one or the other of the variations illustrated in FIGS. 2A and 2B.
In the case of FIG. 2A, the resist has been developed in an aqueous alkaline tetramethyl ammonium hydroxide (TMAH) solution, for example, at a 2.38% concentration. The polymer chains of the exposed regions have recovered, after the resist heating, their solubility in the alkaline development solution. After development, only non-exposed resist regions 9 remain on the upper surface of the wafer, exposed regions 7 having been removed.
In the case of FIG. 2B, the resist has been developed in an organic solvent, for example, a solvent comprising methyl-n-amyl ketone or butyl acetate. In this case, the lack of solubility of the polymer chains having recovered their —OH and —COOH functions in an organic solvent is used. The polymer chains of the non-exposed regions are not soluble in an aqueous solution, since they substantially support as many dissolution inhibiting groups as originally, but are soluble in an organic solution. The exposed regions are not soluble in an organic solution. As illustrated in FIG. 2B, after the step of development of the resist by an organic solvent, only exposed regions 7 of the resist then remain on the upper surface of the wafer.
U.S. Patent Application Publication No. 2004007382 describes a photolithography method of the above-described type using a chemically-amplified resist and comprising two additional steps after the step of resist development by an aqueous solution. After development, the resist regions which were protected by the mask on exposure to the sensitizing radiation remain at the surface. The first additional step comprises exposing the resist to a second sensitizing radiation, without using any mask. The second additional step comprises neutralizing the acid compounds generated in the resist at the second exposure thereof. These two additional steps enable to avoid the flowing of the resist after development, in etching and ion implantation steps during which the wafer is brought to a temperature capable of reactivating the diffusion of residual photogenerated acid compounds and their reaction with dissolution-inhibiting groups, which makes the resist less resistant. Such a resist flow may result in altering the size of the etched or implanted patterns.
The use of chemically-amplified resists supporting dissolution-inhibiting groups of low activation power, to limit the parasitic diffusion of acid compounds during the heating step however raises a new issue. Indeed, in such resists, acid compounds are capable of reacting with dissolution-inhibiting groups in the absence of any heating, that is, at ambient temperature, even if this decreases the reaction kinetics. Now, a non-negligible time that cannot be shortened always elapses between the end of the heating step and the beginning of the development step. Such delays between steps within the photolithography equipment may result in a parasitic diffusion of acid compounds. Further, for practical reasons, associated with the organization of an integrated circuit manufacturing plant, several hours, or even several days, may elapse between the end of the step of heating after exposure and the beginning of the development step. Acid compounds then risk continuing to react in uncontrolled fashion with dissolution-inhibiting groups, even in the absence of any heating. As a result, the size of the exposed regions of the resist layer risks becoming too small with respect to the expected size. Another consequence is that acid compounds diffuse towards the non-exposed regions of the resist, and react in these regions with dissolution-inhibiting groups. The longer the waiting time before development, the less the dimensions of the resist patterns remaining on the upper surface of the wafer will correspond to the dimensions of the patterns of the initial mask. If the differences between dimensions of the resist patterns and the dimensions of the mask patterns are too large, for example, if these differences correspond to more than 10% of the dimensions of the smallest patterns of the mask, all the steps of the photolithography method will have to be resumed.
There thus is a need for a photolithography method using chemically-amplified resists providing resist pattern dimensions after development which substantially corresponds to the dimensions defined on the mask used during the resist exposure, or dimensions taking into account a given intentional dimensional shift between the dimensions defined on the mask and those reproduced in the resist, whatever the delay or the waiting delay between the end of the heating step after exposure and the beginning of the development step.

Photolithography method using a chemically-amplified resist


A condenser microphone provided with a battery compartment having a coil spring electrode is adapted to: extend a return stroke of the coil spring electrode; prevent high frequency current from penetrating into the microphone from the coil spring electrode to suppress the occurrence of noise; and prevent the coil spring electrode from generating mechanical noise. The condenser microphone includes: a body case into which a condenser microphone unit is incorporated; a battery compartment provided in the body case; a coil spring electrode that is provided at an end of the battery compartment, and pushed and compressed by an electrode of a battery by the battery being inserted therein; and a conductive cushion that is disposed within the coil spring electrode, and can contact with the coil spring electrode while being compressed together with the coil spring electrode at least when the coil spring electrode is compressed.

1. Field of the Invention
The present invention relates to a condenser microphone, and in particular relates to the structure of a power supply battery housing part and more specifically to the structure of an electrode.
2. Related Background of the Invention
Since the impedance of a microphone unit is extremely high, a condenser microphone incorporates therein an impedance converter comprised of an FET (field effect transistor) as a main body, thereby reducing the output impedance. A power supply is required for driving the impedance converter. The power supply includes a phantom power supply, which is an external power supply, and a built-in power supply comprised of a battery, which is housed in a battery compartment within the microphone.
The sound signal converted by the condenser microphone unit is impedance-converted by the impedance converter and then passes through a power module part that includes a low cut circuit, an output circuit, and the like, to be output as a microphone output. This microphone output is input into an external circuit via an output cable comprised of a balanced shielded cable. The output cable is constructed so as to be removably connected to the microphone body by a standardized three-pin type microphone connector, e.g., a connector defined by EIAJ RC-5236 "Latch-Lock Type Round Connector for Acoustic Equipment". The three-pin type microphone connector is commonly used with a first pin as ground, a second pin as the hot side of a signal and a third pin as the cold side of a signal. The connector of the microphone body is a male connector, the cable side connector is a female connector, and the both connectors are engaged so that the microphone body is electrically connected to the output cable. To the first pin of the cable side connector a connection end which is an extended part of a shield outer jacket of the microphone cable is connected, and two core wires of the microphone cable are connected to the second pin and third pin, respectively.
If the microphone body or the output cable is irradiated with strong electromagnetic waves and then the electromagnetic waves directly penetrate into the microphone body, or travel through the output cable and penetrate into the microphone body via the connector, these are demodulated by the impedance converter or other circuitry to be output from the microphone as audio frequency noise. In particular, as in recent years, as mobile phones have spread widely, a mobile phone is often used in the vicinity of a microphone and electric waves of the mobile phone more often penetrate into the microphone, thus presenting a serious problem of noise generation caused by high frequencies used in the mobile phone.
The condenser microphone includes a battery compartment for a built-in power supply as described above, and the existence of this battery compartment causes penetration of high frequency electromagnetic waves from the outside. Hereinafter, the reason will be described with reference to an example of a conventional condenser microphone shown in FIG. 3A and FIG. 3B.
In FIG. 3A and FIG. 3B, a body case 10 of a microphone is an approximately cylindrical member, and a part of the peripheral wall of an intermediate portion in the axial direction of the cylinder is removed to form a partially cylindrical shape. In the body case 10, end plates 14 and 16 serving also as an electrode receptacle are fixed to both ends of the portion formed into the partially cylindrical shape, respectively, and an interior space of the partially cylindrical shape of the body case 10 partitioned by the end plates 14 and 16 serves as a battery compartment 12. The battery compartment 12 is capable of housing a dry cell used for the built-in power supply, e.g., one AA dry cell 20. To the end plate 16, an electrode plate 17 formed so as to receive the positive electrode of the dry cell 20 is mounted, and to the other end plate 14, there is mounted a coil spring electrode 18 for pressing the dry cell 20 toward the electrode plate 17, the coil spring electrode 18 being in contact with the negative electrode of the dry cell 20. The outer diameter of the coil spring electrode 18 decreases sequentially from the base toward the tip, the coil spring electrode 18 is allowed to sink into one plane when being pushed by the negative electrode of the dry cell 20, and thereby a large return stroke can be obtained.
The tip (at the left end in FIG. 3A and FIG. 3B) side of the body case 10 partitioned by the end plate 16 is a microphone unit incorporating part 30, and into this microphone unit incorporating part 30 a non-illustrated condenser microphone unit is to be incorporated. The inner periphery of one end of a connector sleeve 28 is fitted around the outer periphery of the back end side of the body case 10, resulting in the connector sleeve 28 being added to the body case 10. At the back end side of the body case 10, a microphone side output connector 40 comprised of a male connector is incorporated into the connector sleeve 28. The output connector 40 includes, behind the end plate 14, a connector base 24 fitted into and fixed to the connector sleeve 28, and connector pins 26 passing through this connector base 24 and being fixed thereto. The output connector 40 is the above-described standardized three-pin type connector, so there are three connector pins 26, however, two pins are illustrated in FIG. 3A and FIG. 3B and the rest pin is hidden behind the two pins. Each connector pin 26 extends in parallel with the axis of the body case 10 and connector sleeve 28. A female-type cable side connector provided at one end of a non-illustrated output cable is coupled to the output connector 40. The cable side connector is fitted into the output connector 40 along the inner peripheral face of the connector sleeve 28, each connector pin 26 of the output connector 40 fits into each receptacle hole of the cable side connector, and thereby the microphone is electrically connected to an external circuit via the output cable.
A cylindrical cover 22 is fitted around the outer periphery of the connector sleeve 28. The cover 22 is movable in the axis direction of the body case 10 while sliding along the outer peripheral face of the connector sleeve 28, and as shown in FIG. 3A, the battery compartment 12 is opened by sliding the cover 22 to the back end side of the body case 10, and as shown in FIG. 3B, by sliding the cover 22 toward the front end side of the body case 10, most of the body case 10 is covered so as to close the battery compartment 12. As shown in FIG. 3A, while the battery compartment 12 is opened, the dry cell 20 can be inserted and removed. As shown in FIG. 3B, the cover 22 covering most of the body case 10 functions also as a grip of the microphone.
As apparent from the above description, the output connector 40 of the microphone exists close to the battery compartment 12, and to this output connector 40 the output cable is connected. Since the battery compartment 12 is constructed so as to be opened and closed with the cover 22 in order to insert and remove a battery and the output connector 40 is constructed so as to insert and remove the cable side connector, there is a gap required for opening and closing or inserting and removing in the battery compartment 12 as well as in the output connector 40. The existence of this gap causes the penetration of high frequency electromagnetic waves into the microphone as described above.
Moreover, the dry cell 20 which is the built-in power supply is grouped into size D, size C, and size AA, however, for example, even with the same AA type, the size thereof differs depending on the manufacturer or the kind of cells. Accordingly, the battery compartment 12 is designed assuming the maximum size among these, and electrical connection needs to be maintained surely even if a dry cell of the smallest size is inserted. Then, the electrode which the negative electrode of the dry cell 20 contacts with is designed so as to obtain a large return stroke as the coil spring electrode 18. In addition to this, the output connector 40 is disposed adjacent to the battery compartment 12, and there is a gap around this output connector 40 as described above, thus providing a portion with poor shielding against the electromagnetic waves. For this reason, the coil spring electrode 18 positioned in the vicinity of the output connector 40 acts as a coil, and the electromagnetic waves that penetrated from the periphery of the output connector 40 are captured by the coil spring electrode 18 and are detected by circuitry in the microphone and output as a noise.
Furthermore, there is also a drawback in case of using a microphone by hand, where a shock is often applied to the microphone due to various causes, such as hitting the microphone against something or dropping it, and the coil spring electrode 18 vibrates every time, thereby causing mechanical noise.
Various kinds of improvements for preventing the mechanical noise of the coil spring electrode have been proposed. For example, stuffing the interior of the coil spring electrode with sponge for restraining the vibration is carried out.
Moreover, a structure is proposed in which a free end of a coil spring electrode is folded back toward the base end side, and while a battery is not inserted in a battery compartment, the tip of the fold-part is in contact with a substrate of the battery compartment by a biasing force of the coil spring electrode, thereby preventing a resonance vibration of the coil spring electrode (e.g., see Patent Document 1).
Furthermore, a structure is proposed in which a bulging part is provided at one end side of a battery compartment so that the coil spring electrode can be forcibly fixed without generating a gap between a holding part that is provided at the one end side of the battery compartment in order to hold the coil spring electrode, and the base of the coil spring electrode held by this holding part (e.g., see Patent Document 2).    [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-178735    [Patent Document 2] Japanese Patent Application Laid-Open No. 58-130362


A hookah is disclosed wherein the stem connects internally to a bottle. A gauge positioned on the stem depicts an indication level with a crown portion of the hookah bottle. When the indication level has been reached, the stem connection point—which may or may not be visible—has been reached.

Of the many proud traditions of Ottoman culture, few have achieved the world-wide fame of hookah smoking. Once confined to the Middle East and Near East regions, the hookah's notoriety was invigorated by Napoleon's invasion of Egypt and the stream of curious Westerners that followed thereafter. Painters, such as Eugene Delacroix and Jean-Leon Gerome, when depicting Oriental styles typically included a hookah as a symbol of the depicted culture. The hookah was elevated from a regional curiosity to a universal symbol of sophistication.
The hookah, which has maintained a constant popularity in the Middle East, presently enjoys in American culture a unique, niched function. Hookah smoking combines community and relaxation into a single event. Rarely does one witness a group smokers crowded about a single cigarette, cigar, or pipe. Though hookahs are often designed with a single smoke outlet; the presence of multiple hoses, each capable of simultaneous use, emanating from a single smoking instrument is unique to the hookah. Multiple hose hookahs form the centerpieces of hookah clubs in which hookah smokers gather to unwind and converse with other community members. A hookah combines fashion, art, and function into a single device.
A basic hookah includes a bottle, a stem, at least one hose with a mouthpiece, and a bowl. The hookah bowl holds the hookah tobacco, frequently "massell." Massell is a mixture of tobacco, molasses, and often a flavor or fruit extract. The molasses and fruit extract add a substantial amount of moisture to the massell that is missing in conventional tobacco. This added moisture makes massell more sensitive to the elements relative to conventional tobacco; prolonged exposure to air evaporates much of the moisture of massell and reduces its flavor. When properly protected, massell allows a smoker a more recreational, flavored smoke than the tobacco of cigars, cigarettes, pipes, and the like. An experienced hookah smoker will know to loosely distribute massell into a pile within the hookah bowl to allow heat to evenly circulate through the pile.
The heat that ignites the massell derives from coals positioned above the hookah bowl. The coals and massell preferably never contact one to the other. A common method of placing coals proximate to the massell involves spreading a foil upon the top of a hookah bowl, punching holes in the foil, and then placing the coals onto the foil. The heat from the lighted coals travels through the holes in the foil to ignite portions of the massell. Particulates from the massell travel in the smoke created by the ignition down through the hookah bowl into the hookah pipe.
The hookah stem is the body of a hookah and is usually fabricated from brass, tin, or stainless steel. The stem transports the massell smoke from the bowl to the hookah bottle, which is a cavern containing water. The bottle of the hookah is typically fabricated of glass or plastic and tends to be the most expressive portion of the hookah, ranging from translucent to wildly-colored. Within the cavern of the hookah bottle, the massell smoke is cooled by the water within. The cooled massell smoke then returns to the stem, though not through the same entrance by which the massell smoke enters the bottle. From the stem, the massell smoke travels through the hose and out of the mouthpiece.
There are presently two prominent versions of hookah structures: the Lebanese style and the Egyptian style. Although the aficionado will explain that there are many differences between the two styles, the practical layman would quickly note the obvious difference: the connection point between the stem and the hookah bowl. The Egyptian style hookah pipe tapers upward into what is generally referred to as a male connection. The Egyptian style hookah bowl includes a female connection which receives the pipe's male connection. In the Lebanese style hookah the bowl has the tapered male connection and the pipe has the female connection to accept the Lebanese style hookah bowl. In both styles, to allow a more airtight connection a collar is generally added to fit around the male connection.
One generally constant theme of hookahs is the point of affixation between the bottle and the stem: the stem attaches to the bottle at the bottle's rim. The stem can affix in numerous ways. The stem may rest on the top of the bottle, the stem may attach via interference fit to the top of the bottle, the stem may be screwed on the bottle either internally or externally, or the stem may sit on the bottle using only gravity.


A device for use in actuating a valve to control the flow of fluids through a flow tube comprises a stationary ring surrounding the flow tube, the ring having an inner diameter greater than an outer diameter of the flow tube. An interior of the ring and an exterior of the flow tube have complementary screw threads. At least three actuators are equally circumferentially spaced along an exterior of the ring. When activated an actuator induces a screw thread on the interior of the ring to engage a screw thread on the exterior of the flow tube such that the flow tube is moved in an axial direction relative to the ring.

Various types of valve apparatus are used in various wellbore types (e.g., subsea, platform, land-based) to control fluid flow through tubing or conduits disposed therein. One such valve is referred to as a subsurface safety valve, or simply as a safety valve, and it provides a "fail-safe" mechanism for closing the wellbore to prevent the uncontrolled release of hydrocarbons or other downhole fluids. Such safety valves are typically actuated in emergency situations, such as blowouts, to provide a pressure barrier (oftentimes in cooperation with blowout preventers) and safeguard local personnel, equipment, and the environment.
U.S. Pat. No. 4,161,219 discloses a safety valve configuration that employs a flapper valve that is spring-biased towards a position closing a fluid passageway in the safety valve body, and a flow tube that is movable between a first position yielding the biasing spring of the flapper valve to open the flapper valve and a second position permitting the biasing spring of the flapper valve to close the flapper valve. The flow tube is also spring biased towards the second position that releases the flapper valve, but the flow tube is normally urged towards the first position in which the flapper valve is opened by the application of hydraulic fluid pressure from the surface. In the event of an emergency, such as a blowout, the hydraulic fluid pressure is reduced to permit the spring bias of the flow tube to urge the flow tube towards its second position, thereby releasing the flapper valve so that its biasing spring urges the flapper valve towards the position closing the fluid passageway.
It is commonly believed today that most of the remaining oil and gas reserves of considerable substance are located in so-called "deep water" or "ultra-deep water" subsurface formations. Such formations may lie underneath 7,000 feet or more of water and up to 30,000 feet or more beneath the seafloor. Some industry experts predict that by the year 2015, 25% or more of offshore oil production will be sourced from deepwater wellbores. As deepwater wells are drilled to greater depths, they begin to encounter extreme high pressure, high temperature conditions (i.e., having an initial reservoir pressure greater than approximately 10 kpsi (69 Mpa) or reservoir temperature greater than approximately 300° F. (149° C.)) that constitute one of the greatest technical challenges facing the oil and gas industry today. As a result, materials that have been used for many years now face unique and critical environmental conditions for which they may not be suitable.
A clear example of such material challenges is found in hydraulic fluids, which are used in a number of downhole applications including safety valve actuation as described above. Hydraulic fluids will suffer a breakdown or stagnation when exposed to high temperatures over time (safety valves can sit dormant downhole for decades) that severely compromises the hydraulic properties of such fluids, rendering them incapable of functioning for their intended hydraulic purposes. Additionally, hydraulically-actuated safety valves are subject to seal failure over time that reduces their performance and reliability.
Therefore, a need exists for a means of reliably actuating valves such as safety valves in downhole environments, for example, in the high pressure, high temperature environments of deepwater wellbores.

Linear actuation system in the form of a ring


A method for defending a computer system comprising a DNS server against a DoS or a DDoS attack directed at said DNS server comprises replacing the address of said system provided by a user to a client software with an alternative address, wherein said address is replaced by a software agent associated with said user, such that said client software is capable of connecting with said system.

Distributed denial-of-service attack (DDoS attack) is an attempt to make a machine or network resource unavailable to its intended users. It generally consists of the efforts of one or more people to temporarily or indefinitely interrupt or suspend services of a host connected to the Internet.
One common method of denial-of-service (DoS) attack involves saturating the target machine with external communications requests, such that it cannot respond to legitimate traffic, or responds so slowly as to be rendered essentially unavailable. Such attacks usually lead to a server overload. In general terms, DoS attacks are implemented by either forcing the targeted computer(s) to reset, or consuming its resources so that it can no longer provide its intended service or obstructing the communication media between the intended users and the victim so that they can no longer communicate adequately.
A "denial-of-service" attack is characterized by an explicit attempt by attackers to prevent legitimate users of a service from using that service. There are two general forms of DoS attacks: those that crash services and those that flood services.
A DoS attack can be perpetrated in a number of ways. The five basic types of attack are:                Consumption of computational resources, such as bandwidth, disk space, or processor time;        Disruption of configuration information, such as routing information;        Disruption of state information, such as unsolicited resetting of TCP sessions;        Disruption of physical network components;        Obstructing the communication media between the intended users and the victim so that they can no longer communicate adequately.
Perpetrators of DDoS attacks typically target sites or services hosted on high-profile web servers such as banks, credit card payment gateways, etc.
A distributed denial of service attack (DDoS) occurs when multiple systems flood the bandwidth or resources of a targeted system, usually one or more web servers. These systems are compromised by attackers using a variety of methods.
Malware can carry DDoS attack mechanisms, such as MyDoom, the DoS mechanism of which was triggered on a specific date and time. This type of DDoS involves hardcoding the target IP address prior to release of the malware and no further interaction is then necessary to launch the attack.
DDoS tools, such as the well-known Stacheldraht, use classic DoS attack methods centered on IP spoofing and amplification like smurf attacks and fraggle attacks (also known as bandwidth consumption attacks). Newer tools can use DNS servers for DoS purposes.
The term "DDoS" refers to DoS attacks launched using many systems simultaneously to launch attacks against a remote host.
DDoS attacks have become more frequent against financial institutions, such as banks and have been known to disrupt their activity and that of their customers. Such attacks are open directed against the DNS server of the institution, thereby preventing the resolution of the hostname to which a customer's web browser is directed. It is therefore clear that it would be desirable to provide means by which regular activities of such institutions, as well as of any other body facing the same malicious attacks, could be maintained in spite of all the attacks.
It is an object of the present invention to provide a system and a method which enable a system that finds itself under a DDoS attack directed against its DNS server to continue functioning in spite of the attack.
It is another object of the invention to provide software means associated with the client software available to a customer, which are suitable to prevent or limit the difficulty of the customer in reaching the desired host.
Other objects and advantages of the invention will become apparent as the description proceeds.


Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for receiving, by the one or more processors, user input, the user input indicating an assignment of a particular task by a first user to a second user, the first user being a user of a product that provides the particular task; determining, by the one or more processors, that the second user is a non-user of the product and, in response: appending product promotion data to an electronic document, the product promotion data providing a summary of task-based action data that is associated with the second user; and transmitting the electronic document to the second user.

Mobile computing continues to grow quickly as mobile computing devices, such as smart phones, add more power and more features. Users of such devices launch various applications, including task-based or task-centric applications, through the mobile computing devices. The task-based applications can assist a user of the mobile computing device in organizing tasks that the user is interested in.


A system and method is provided for controlling clock skew to meet timing constraints for a semiconductor integrated circuit. On-chip self-tuning circuits can be connected to each latch in the integrated circuit for controlling clock skew. Each self-tuning circuit delays a clock signal that is input to a latch when the clock skew does not satisfy the timing constraint for that latch. The self-tuning circuit repeatedly delays the clock signal until the clock skew is satisfied or until the delay becomes greater than or equal to a predetermined threshold. The delayed clock signal is then pushed to other latches in the integrated circuit until all the timing constraints for the integrated circuit are satisfied.

The present invention is generally related to timing in an integrated circuit. In particular, the present invention is related to controlling clock skew in an integrated circuit.
In modern, high-performance digital circuits, precise timing is of paramount importance. Slight clock uncertainties can cause momentary, spurious signals which can become magnified as they propagate through a complex digital circuit, often with unpredictable and disastrous results. If such uncertainties are not carefully controlled, they can quickly lead to catastrophic failure or inoperativeness of the digital circuit.
Tiny differences in clock outputs coupled with propagation delays across the complex web of conducting pathways (or traces) on a printed circuit board are one source of timing uncertainty. The source of timing uncertainty effects are well-known to those of ordinary skill in the art, and is typically referred to as clock skew.
Broadly speaking, clock skew is the difference in time delay from a clock input to each of its loads. Clock skew includes the delay arising from the propagation of signals in a printed circuit board across various traces to respective components, which use clock signals as inputs.
For example, FIG. 3 shows that MY_CLK takes 4 ns to travel to a clock input for FF1, but MY_CLK takes 12 ns to travel to a clock input for FF2. In this case, there is a 8 ns clock skew for FF2. The clock skew for FF2 must satisfy the timing constraint for FF2 in order for FF2 to timely latch the data from FF1. If the delay between FF1 and FF2 is greater than the clock skew for FF2, then the clock skew for FF2 satisfies the timing constraint for FF2, and FF2 will latch the data from FF1 on a MY_CLK pulse. If the delay between FF1 and FF2 is less than the clock skew for FF2, then FF2 will latch the DATA input on a MY_CLK pulse, as if FF1 were not in the circuit.
Clock skew places limitations on the speed and performance of high-speed digital devices and must be taken into account in the design of such devices. As clock frequencies are increased aggressively in high performance designs, clock skew constraints become increasingly stringent. In GHz-clocked microprocessors, clock skews are often required to be smaller than 50 ps.
It may be possible to design a clock network having close to zero skew using CAD tools during the design of an integrated circuit. However, uncontrollable manufacturing processing, voltage and temperature (PVT) variations, which generally cannot be accounted for during the design of an integrated circuit, can cause clock skew to reach unacceptable levels. The PVT variations can be as large as 25%, causing significant clock skew. Therefore, on-chip circuitry is needed for controlling clock skew.
The present invention provides a method and on-chip circuitry for controlling clock skew to satisfy timing constraints for a semiconductor integrated circuit.
In one respect, the present invention includes a self tuning circuit comprising the following: a flip flop connected to a delay path and having a flip flop clock input; a first up-counter connected to the flip flop and having a first up-counter output; a second up-counter connected to the flip flop and the output of the first up-counter, wherein the second up-counter includes a second up-counter output; and an on-purpose delay element connected to the second up-counter output. The on-purpose delay element possesses a clock input and a clock output. The clock output is connected to a latch and the flip flop clock input, and the on-purpose delay element is operable to receive a clock signal on the clock input and transmit either a delayed clock signal or a non-delayed clock signal to the latch and flip flop clock input.
The on-purpose delay element is operable to delayed the clock signal when clock skew for the latch fails to satisfy a delay path timing constraint for that latch. Also, the on-purpose delay element is operable to transmit a non-delayed clock signal when the clock skew satisfies the timing constraint for the latch.
In another respect, the present invention provides a method of controlling clock skew for a plurality of latches in a semiconductor integrated circuit. The method includes the following steps: determining whether clock skew for a first latch satisfies a timing constraint; when the timing constraint is not satisfied, delaying a clock signal latching the latch by one time unit; and pushing the delay to a second latch connected to the first latch. The step of delaying a clock signal can further include repeatedly delaying a clock signal by one time unit and counting each time unit. The clock signal is repeatedly delayed until the timing constraint is satisfied or the total number of counted time units is equal to 2n where n is the number of bits in an n-bit up counter counting each time unit.
The present invention provides a self-tuning circuit and method for controlling clock skew to satisfy timing constraints for a semiconductor integrated circuit. Due to circuit imperfections caused during manufacturing, design techniques for meeting timing constraints may be insufficient for satisfying stringent timing constraints. The present invention accounts for manufacturing imperfections by providing an on-chip solution for controlling clock skew to satisfy circuit timing constraints.

Parallel push algorithm detecting constraints to minimize clock skew

Hewlett-Packard Development Company L.P.


In an output buffer apparatus including a main-buffer circuit including a plurality of first transistors each connected between a first power supply terminal and an output terminal and a plurality of second transistors each connected between a second power supply terminal and the output terminal, and a pre-buffer circuit including a plurality of first pre-drivers each driving one of the first transistors in accordance with a data signal and a plurality of second pre-drivers each driving one of the second transistors in accordance with the data signal, a plurality of first sequential circuits are provided for receiving first impedance adjusting signals in synchronization with the data signal to turn ON the first pre-drivers, and a plurality of second sequential circuits are provided for receiving second impedance adjusting signals in synchronization with the data signal to turn ON the second pre-drivers.

1. Field of the Invention
The present invention relates to an output buffer apparatus capable of adjusting the output impedance thereof.
2. Description of the Related Art
In a computer system, as the speed of a central processing unit (CPU) has increased, the propagation speed of signals between semiconductor devices and the propagation speed of signals between printed circuit boards have also increased. Note that microstrip lines or coaxial cables are used as transmission lines for transmitting high frequency signals.
When the frequency of transmitted signals is low, the wavelength of the transmitted signals is relatively large with respect to the length of the transmission line, so that the phases of the transmitted signals are approximately the same within the transmission line. Therefore, even when reflection noise is generated at a terminal of the transmission line due to a discrepancy between the output impedance of an output buffer apparatus and the characteristic impedance of the transmission line, since the phase of the reflection noise is the same as those of the transmitted signals, the transmitted signals are hardly distorted.
On the other hand, when the frequency of transmitted signals is high, the wavelength of the transmitted signals is relatively small with respect to the length of the transmission line, so that the phases of the transmitted signals are different from each other within the transmission line. Therefore, when reflection noise is generated at the terminal of the transmission line due to a discrepancy between the output impedance of the output buffer apparatus and the characteristic impedance of the transmission line, since the reflection noise may affect the transmitted signals, the transmitted signals are remarkably distorted.
In order to suppress the above-mentioned reflection noise, a terminal processing is carried out so that the characteristic impedance of the transmission line is brought close to an impedance at a signal transmitter side terminal, i.e., an output buffer of a first device or an impedance at a signal receiver side terminal, i.e., an input buffer of a second device which is connected via a transmission line to the first device.
Note that the terminal processing is divided into a parallel terminal processing where a resistance corresponding to the characteristic impedance is connected between the signal receiver terminal (the input buffer) and a power supply terminal (or the ground terminal) and a serial terminal processing where the output impedance of the signal transmitter side terminal (the output buffer) is brought close to the characteristic impedance of the transmission line.
In the above-mentioned serial terminal processing, a semiconductor chip including the output buffer is subject to environmental temperature, power supply voltage, manufacturing process and the like, so that the output impedance of the output buffer per se is subject to the environmental temperature, the power supply voltage, the manufacturing process and the like. Therefore, a prior art output buffer apparatus has been known to include an impedance adjusting circuit (see: JP-A-2002-94366). The output buffer apparatus is constructed by a main-buffer circuit including a plurality of P-channel MOS transistors each connected between a power supply terminal and an output terminal and a plurality of N-channel MOS transistors each connected between the ground terminal and the output terminal and a pre-buffer circuit including a plurality of first pre-drivers each driving one of the P-channel MOS transistors in accordance with a pull-up impedance adjusting signal and a data signal and a plurality of second pre-drivers each driving one of the N-channel MOS transistors in accordance with a pull-down impedance adjusting signal and the data signal. This will be explained later in detail.
In the above-described prior art output buffer apparatus, however, since the impedance adjusting signals are supplied to the pre-buffer circuit in asynchronization with the data signal, the output signal at the output terminal may be changed in the middle of data "1" or "0", i.e., the output signal at the output terminal is distorted, thus deteriorating the quality thereof.

Output buffer apparatus capable of adjusting output impedance in synchronization with data signal


Light in each of a series of very small areas arranged in a row is subjected to color separation and color mixing into a very small portion of light. There are provided columnar concave lenses CC1 corresponding to columnar convex lenses CV1 formed in a lattice pattern, dichroic mirrors DM1, DM2 each associated with the concave lenses CC1, mirrors M1 each associated with the dichroic mirrors DM2, and a liquid crystal panel main body LP disposed in contact with this optical element. Pixels LR, LG, LB in the liquid crystal panel main body LP are disposed so as to correspond in position to the mirrors M1, the dichroic mirrors DM2 and the mirrors M2, respectively.

The present invention relates to an optical element with a color processing section, and its manufacturing methods and its application to a liquid crystal panel, a liquid crystal display device, and a solid-state imaging device.
FIG. 12 is a schematic diagram illustrating a conventional liquid crystal display device. As shown in FIG. 12, the conventional liquid crystal display device comprises a reflective plate RF provided near a lamp LM, a screen SC provided on the opposite side the reflective plate RF with respect to the lamp LM, a liquid crystal panel LCP1 provided between the lamp LM and the screen SC, a condenser lens CL provided between the lamp LM and the liquid crystal panel LCP1, and a projection lens LNS provided between the liquid crystal panel LCP1 and the screen SC.
In the liquid crystal display device shown in FIG. 12, light from the lamp LM falls on the liquid crystal panel LCP1 via the condenser lens CL, and an image displayed on the liquid crystal panel LCP1 is projected onto the screen SC through the projection lens LNS.
A liquid crystal display device of this type is simple in construction.
FIG. 13 is a schematic diagram illustrating another conventional liquid crystal display device. As shown in FIG. 13, this liquid crystal display device comprises a dichroic mirror (interference filter) DM11 for reflecting blue light B; a dichroic mirror DM12 for reflecting green light G; a mirror M11; a mirror M12 associated with the dichroic mirror DM11; a mirror M13 associated with the mirror M11; a dichroic prism DP provided between a combination of the dichroic mirror DM12 and the mirrors M12, M13, and a projection lens LNS; and liquid crystal panels LCP2 provided between the combination of the dichroic mirror DM12 and the mirrors M12, M13, and the dichroic prism DP; the dichroic mirrors DM11, DM12 and the mirror M11 being located on the opposite side of the reflective plate RF with respect to lamp LM.
In the liquid crystal display device shown in FIG. 13, light from the lamp LM is subjected by the dichroic mirrors DM11, DM12 to color separation into blue light B, green light G and red light R. The blue light B, the green light G and the red light R are each directed to a respective one of the liquid crystal panels LCP2, and are subjected by the dichroic prism DP to color mixing. Then, an image displayed on the liquid crystal panel LCP2 is projected on a screen SC by the projection lens LNS.
FIG. 14 is a schematic diagram illustrating still another conventional liquid crystal display device. As shown in FIG. 14, this liquid crystal display device comprises a mirror M14 provided at the opposite side of the reflective plate RF with respect to lamp LM; a dichroic mirror DM13 for reflecting green light G, recieved from the mirror M14; a dichroic mirror DM14 for reflecting blue light B; a mirror M15 associated with the dichroic mirror DM13; a dichroic mirror DM15 for reflecting blue light B, recieved from the dichroic mirror DM14; a dichroic mirror DM16 for reflecting red light R, received from the mirror M14; a condenser lens CL and a liquid crystal panel LCP2 provided between the mirror M15 and the dichroic mirror DM15; a condenser lens CL and a liquid crystal panel disposed between the dichroic mirrors DM14, DM15; and a condenser lens CL and a liquid crystal panel disposed between the dichroic mirror DM14 and the mirror M14.
In the liquid crystal display device shown in FIG. 14, light from the lamp LM is subjected by the dichroic mirrors DM13, DM14 to color separation into green light G, blue light B and red light R. The blue light B, the green light G and the red light R are directed to respective ones of the liquid crystal panels LCP2, and are subjected by the dichroic mirrors DM15, DM16 to color mixing. Then, an image displayed on the liquid crystal panel LCP2 is projected on a screen SC by a projection lens LNS.
The brightness of the image projected on the screen in these liquid crystal display devices is not lowered because it is unnecessary to use red, green and blue color filters of for respective pixels of the liquid crystal panel LCP2.
Incidentally, "Large Screen Projection Display" pp 164.about., February, 1991, the Journal of the Institute of Television Engineers of Japan, describes a liquid crystal display of this type representative of the prior art.

Color liquid crystal display device having three dichroic mirrors per pixel


A gun-aiming device includes a base mount for attaching to a gun barrel having first and second orthogonally arranged passages, a sighting element having a stem portion with an annular groove and a head portion attached to one end of the stem portion with the stem portion removably mounted in the first passage of the base mount such that the head portion extends above the base mount for use in aiming the gun, and a yieldable biasing arrangement disposed in the second passage of the base mount for releasably engaging the annular groove of the stem portion of the sighting element at any location about the stem portion so as to provide a quick release snap-fit type of latching of the stem portion of the sighting element in the first passage of the base mount. A plurality of sighting elements being interchangeable with one another are provided. The sighting elements have respective head portions of different sizes and colors for respectively adapting the gun-aiming device to different distances and backgrounds.

1. Field of the Invention
The present invention generally relates to hunting and trap shooting equipment and, more particularly, is concerned with a gun-aiming device.
2. Description of the Prior Art
Game hunting and trap shooting are widely popular activities practiced by thousands of sportsmen in the United States. For optimum results, the sportsman needs equipment which is readily adaptable to a variety of circumstances.
Specifically, for both game hunters and trap shooters, sighting aids are of obvious importance in obtaining maximum shooting efficiency, whatever the particular type of gun selected. Numerous sighting aids have been devised for attachment to a variety of gun types. Some of these include components which are attached on or built directly into the gun barrel itself.
One typical threaded sighting element is seen in FIG. 1. This sighting element, generally designated 10, has a head portion 12 attached to one end of a threadable stem portion 14. The stem portion 14 is mountable in the threaded upwardly opening passage 16 of the gun barrel 18. One drawback of this construction is that after repeated use the threads on the stem and barrel aperture will wear down or become stripped, thereby loosening up the gunsight device and diminishing its effectiveness in sighting a target.
Various non-threaded removable gunsight devices have been proposed to overcome the drawback of the prior art gunsight device of FIG. 1. Representative examples of these non-threaded removable gunsight devices are the ones disclosed in U.S. patents to Adams (U.S. Pat. No. 4,008,536), Ferraro (U.S. Pat. No. 5,016,381) and Pickle (U.S. Pat. No. 5,016,382). While these non-threaded gunsight devices overcome the drawback of the threaded gunsight, they substitute other drawbacks in its place. These drawbacks are overly complex constructions, too many parts with differently shaped and angled surfaces requiring machining to close tolerances and thus costly fabrication, and tedious procedures for installing and removing the sighting element of the gunsight devices. Further, a number of movements, both angular and rotational, are required to position the particular sighting element in place for aiming the gun and then for removal of the sighting elment from its seat. Obviously, such construction and assembly of components are rather complicated and costly.
Additionally, hunters often paint their sighting element, specifically the head portion, a particular color to assist them in certain weather conditions or for specific types of game. Generally, for differing weather or hunting conditions, with respect to the sighting element of FIG. 1 the hunter will paint the head portion a corresponding color rather than removing the sighting element itself and inserting a different prepainted element, because of the limited durability of the threaded passage 16. Also, this permanent type of sighting element provides for only one size of head portion for aiming the gun, precluding such variations in size as may be needed for variations in distance of game hunted.
Consequently, a need exists for a gun-aiming device of simple construction which provides for quick mounting and removal of a particular sighting element from its base mount and for choice in color and size of the most suitable sighting element for particular hunting or trap shooting conditions.


A swivel device for coupling a back reamer to a plastic pipe to be drawn through a hole has a swivel shaft that extends into a tubular body and engages a bearing. At one side of the bearing an O-ring seals between the shaft and the body. A grease supply path extends past the bearing to a grease chamber on the bearing side of the O-ring and thence via a duct, to a grease chamber on the other side of the O-ring.

The present invention relates to drilling apparatus, and, in particular, to apparatus for use in drilling underground, e.g. drilling under highways for the purpose of installing components such as cables, ducts and pipes.
It is known to use a process called "directional drilling" to install services in sensitive areas where open cut techniques cannot be used such as under runways, motorways, rivers and railways. A small diameter hole is first bored under the crossing using a boring head and drill string made up of steel tubes through which a bentonite slurry known as "Mud" is pumped at high pressure. The boring head is then replaced with a back reamer behind which is connected, via a swivel, the plastic pipe (or other component) to be installed. The drill string is then rotated and pulled back, whilst mud is again pumped through the rods and out of jets in the reamer. The rotating reamer enlarges the hole, whilst the mud cools it and stabilises the opening. The pipe is thus pulled back under the crossing. If, however, the swivel seizes up, the plastic pipe is wound up and irreparably damaged, and the crossing is abandoned, wasting costly time and materials.
A conventional swivel has a tubular body portion into which a swivel shaft extends, there being a bearing to facilitate relative rotation. There is a lip seal intended to exclude mud and other debris from the, bearing. Grease is normally pumped into the swivel before each shot, but because the seal is orientated to keep mud out rather than grease in, this tends to lift the lip of the seal off the swivel shaft and allow ingress of grit. The seal immediately starts to deteriorate and allows more debris to pass. When this reaches the bearing, the eventual destruction of the bearing, and hence the swivel, is inevitable. Common practice is to throw swivels away and replace them before they fail. Thus, an improved sealing arrangement is desirable.
The bearings are also subject to large forces. In order to make them better able to stand up to the forces, larger bearings may be used. But this requires larger housing spaces to be provided in the swivel devices, leading to many practical problems. It is also known to use two or more angular contact bearings, stacked one behind another along the swivel shaft, with a backing nut behind the last one. But this is not very effective.

Handlemaker Road, Marston Trading Estate


A processor circuit is provided in a coherent optical receiver module. The processor receives a series of electrical signals over a time period, representative of a series of optical signals received at instants of time within the time period. Each of the electrical signals is indicative of a respective one of a plurality of points on an IQ plane, each of the points being spaced from one of a plurality of predetermined points in the IQ plane by a corresponding one of a plurality of distortion values. In addition, the processor circuit calculates one or more perturbative coefficients based on one or more of the distortion values and determines data from the series of electrical signals based on the perturbative coefficient.

In fiber optic communications, nonlinearity is a behavior of an optical signal between a transmitter and a receiver in which the optical signal received at the receiver deviates from its normal course and does not vary in direct proportion to the optical signal transmitted at the transmitter. In the art, this is known as perturbation. Examples of nonlinearities include intrachannel nonlinearities, stimulated Brillouin scattering (SBS), stimulated Raman scattering (SRS), four wave mixing (FWM), self-phase modulation (SPM), cross-phase modulation (XPM), and intermodulation. Nonlinear mitigation techniques are used to simulate the normal course of the optical signal and are key to correcting for perturbation and thereby improving capacity and performance in future optical communications.
Back propagation is a technique that may be used to mitigate nonlinear effects in fiber optic links in fiber optic communications. Back propagation simulates error backward down the fiber optic link to address the non-linear effects within the received optical signal. However, back propagation is very computationally intensive.
Optical nonlinear mitigation using perturbative pre- or post-distortion may be used to increase the reach of optical signals in fiber optic communications. The perturbation induced by the fiber optic link is typically calculated using non-linear perturbation distortion coefficients (Cm,n) and the known or recovered transmitted data. The non-linear perturbation coefficients are typically calculated using known fiber optic link parameters, such as pulse width, inverse of symbol rate, the transmission distance, dispersion map, fiber type, amplifier spacing, and fiber nonlinear parameters.
Optical nonlinear mitigation techniques using perturbative pre- or post-distortion algorithms have been shown to be as effective in mitigating optical nonlinear effects in a fiber link as digital back propagation. Given the non-linear perturbation distortion coefficients (Cm,n), the perturbative pre-distortion algorithm is computationally simpler than back propagation.
However, determining and/or measuring fiber optic link parameters used in the current systems to calculate the non-linear perturbation distortion requires human intervention which may be time consuming and expensive. Additionally, the results of the determinations and measurements may be inaccurate. Further, any change in the fiber optic link parameters requires additional determinations and measurements with the current systems. Therefore, methods and systems are needed to determine non-linear perturbation distortion coefficients automatically at the optical receiver, and ideally without knowledge and/or use of the fiber link parameters.

System and method for determining nonlinear mitigation perturbative distortion coefficients using a received optical signal


In accordance with embodiments disclosed herein, there is provided systems and methods for tracking the mode of processing devices in an instruction tracing system. The method may include receiving an indication of a change in a current execution mode of the processing device. The method may also include determining that the current execution mode of the received indication is different than a value of an execution mode of a first execution mode (EM) packet previously-generated by the IT module. The method may also include generating, based on the determining that the current execution mode is different, a second EM packet that provides a value of the current execution mode of the processing device to indicate the change in the execution mode for an instruction in a trace generated by the IT module. The method may further include generating transactional memory (TMX) packets having n bit mode pattern in the packet log. The n is at least two and the n bit mode indicates transaction status of the TMX operation.

An instruction tracing system (ITS) is a tracing capability, which provides a software execution control flow trace. The trace output is in the form of packets of variable sizes. A decoder may use the packets, along with the associated instruction bytes, to reconstruct the execution flow of the software that was traced.

Tracking mode of a processing device in instruction tracing systems


A new scintillating optical fiber is used in an array as a scintillator plate for imaging with high energy radiation, particles and the like. The scintillating optical fiber has an inner plastic core fiber which is transparent to visible radiation and has an index of refraction of about 1.45 or greater. The inner plastic core fiber has a plastic cladding material which has an index of refraction less than that of the inner plastic core fiber. The inner plastic core fiber contains a polymeric matrix material; a metal moiety; and an organic fluorescent material. The scintillator plates are useful in producing high efficiency and high resolution radiographic systems for x-ray medical diagnosis or non-destructive inspection as well as non-destructive inspection with thermal neutrons. In medical x-ray applications, such as mammography, the need for lower doses of x-rays for a given image quality is met and exceeded by the higher detection efficiency of the scintillator plates and their associated electronic read-out system.

1. Field of the Invention
This invention relates to optical fiber scintillators for use in detecting x-rays, .gamma.-rays, thermal neutrons, and the like. More particularly, this invention relates to improved, high efficiency, high spatial resolution optical fiber arrays for use as scintillator plates in radiographic imaging systems and particularly real-time imaging systems.
2. Description of Related Art
Conventional radiographic imaging systems which are used medically for diagnosis and industrially for inspection, typically contain a detector which is a combination of an inorganic phosphor screen with a photographic film or with an image intensifier, photo-electric detector. When it is necessary to view the image instantaneously, i.e., in real-time, the image intensifier, photo-electric detector is used in combination with suitable monitor system. Such inorganic phosphor screens which are used extensively for high energy photon imaging suffer from the compromise between detection efficiency and spatial resolution. This compromise is the consequence of the low interaction probability of the high energy photon within the phosphor screen thickness to produce scintillation light. When the interaction probability is increased by increasing the thickness of the screen, spatial resolution of the incident high energy photons suffers since the isotropically produced scintillation light is spread over a larger area. Loss in spatial resolution is further exacerbated by light scatter due to the granularity of such thick phosphor screens. Thus, screens are manufactured to be as thin as possible without unduly limiting sensitivity.
In an attempt to overcome the inherent limitations of conventional phosphor screens, fiber optic scintillator plates have been devised for real time imaging systems. Such a plate is described in Brown, U.S. Pat. No. 4,415,810 and in the publication "High-Density Glass Scintillator for Real-Time X-Ray Inspection" by Placious et al. in MATERIALS EVALUATION, Vol. 49, No. 11, pp. 1419-21, November, 1991. Brown discloses a device for imaging penetrating radiation which includes a multiplicity of contiguously disposed fiberoptic tubes each of which is made of a very small diameter with an inner core material composed of scintillating material and a cladding glass about the inner core to serve as a reflector and a third and outer layer which is light absorbing to absorb stray light from the inner core. The specific scintillating material disclosed is a glass formulation containing lithium and cesium. Brown discloses that the device may be used in the electron image detection system of U.S. Pat. No. 4,096,381. Placious et al. disclose a formulation for terbium-activated radioluminescent glass which produced a glass scintillator with excellent x-ray imaging detection characteristics.
Two studies have been published relating to the use of scintillating optical fiber arrays for x-ray imaging. Scintillating optical fiber arrays for high resolution x-ray imaging over 5 keV was disclosed by E. Bigler and F. Polack in APPLIED OPTICS; Vol. 24, No. 7; pp. 994-997; 1 Apr. 1985. Bigler et al. disclose an x-ray image detector having a 10 - 5 .mu.m resolution for 5 keV x-rays in which the detector consists of an array of optical fibers, the core of which has been replaced by a high-index fluorescent material. In practice, the optical fibers were an array of microtubes filled with a liquid scintillator, i.e., a benzene or toluene solution of an organic fluorescent material. Other scintillating materials suggested for investigation included glasses, plastics and gels. A study of the physics of scintillating fiber optics and their applications in radiographic systems was disclosed by H. Shao, D. W. Miller and C. R. Pearsall in IEEE TRANSACTIONS ON NUCLEAR SCIENCE; Vol. 38, No. 2; pp. 845-857; April, 1991. In their study, Shao et al. used Tb.sub.2 O.sub.3 -based scintillating fiber optic arrays and concluded that scintillating fiber optic arrays are superior to the phosphor screen at all x-ray energies except low energy (i.e., below 90 keV).
Organic plastic scintillators have been used for scintillation counting of high energy particles and radiation and is described in Chapter 9 of THE THEORY AND PRACTICE 0F SCINTILLATION COUNTING by J. B. Birks, 1964, Pergamon Press, Oxford. In particular, on pages 339 and 340, Birks reviews various attempts to incorporate compounds containing heavy elements into plastic scintillators, in order to increase .gamma.-ray absorption coefficient, without causing too great a deterioration in scintillation efficiency due to impurity quenching. Illustrative of organic plastic scintillators which are free of heavy metal elements, are the plastic scintillators disclosed in Shimizu et al., U.S. Pat. No. 4,495,084 and the high temperature plastic scintillators of Simonetti, U.S. Pat. No. 4,713,198.
Quench-resistant fluors for liquid scintillation counting have been disclosed by S. W. Wunderly and J. M. Kauffman in APPL. RADIAT. ISOT.; Vol. 41, No. 9; pp. 809-815; 1990; INT. J. RADIAT. APPL. INSTRUM.; Part A. Wunderly et al. disclose fluors which are diaryl derivatives of fluorene or 2,2'-bifluorene and which were considered to be the most efficient fluor systems studied, particularly when chemically quenched in a non-aqueous system, or quenched with water in an emulsifier-containing system.
Radiation sensitive optical fibers and their use as detectors are disclosed in Koechner, U.S. Pat. No. 4,788,436. Koechner discloses an optical fiber sensitive to nuclear radiation which includes a thin filament core formed of a plastic scintillator material which scintillates in the presence of nuclear radiation, and an optical cladding material around the optical fiber. The specific scintillator materials disclosed by Koechner is polyvinyltoluene or polystyrene which are doped with organic scintillator material.
While scintillator plates of fiber optic arrays have improved the resolution of real-time radiographic systems, there continues to be a need to improve the efficiency of the plate in detecting x-rays, .gamma.-rays and thermal neutrons, so as to at least equal the efficiency of screen/film systems without compromise of resolution. This need is particularly important in the area of medical diagnostics and treatment wherein exposure of the patient to high energy radiation is to be minimized. There is an additional need for a fiber optic plate with improved efficiency in exclusively detecting thermal neutrons without detecting spurious .gamma.-rays or x-rays.

High efficiency, high resolution, real-time radiographic imaging system


An image recording apparatus comprises: a printer to form an image onto a recording medium; and a blank forming device to form blanks in the peripheral edge portions of the image formed on the recording medium. The blank forming device sets the blank amount in the front edge portion of the image to be smaller than the blank amount in the back edge portion or sets the blank amount of the image on the scan starting side to be smaller than the blank amount of the image on the scan end side. Even if various tolerances regarding the apparatus, copy transfer paper, conveying apparatus, and the like occur, the image is not deviated out of the paper and the toner image which is not copy transferred onto the photo sensitive drum does not remain and does not make the inside of the apparatus dirty. The effective usable region for image formation can be widened even in the two-sided mode and the multi-mode.

1. Field of the Invention
The present invention relates to a method of making a blank in an apparatus for forming an image onto a recording medium.
2. Related Background Art
As an example of such a kind of image recording apparatus, a laser beam printer (hereinafter, abbreviated as an LBP) will be described. FIG. 16 shows an example of conventional LBP apparatuses disclosed in U.S. Pat. Nos. 4,059,833, 4,175,851, and the like. Reference numeral 1 denotes a laser driving circuit; 2 indicates a laser beam emitting device; 3 a polygonal mirror; 4 a photo sensitive drum; 5 a primary charger; 6 a developing device; 11 a copy transfer paper; 13 a conveying roller; 14 a registration roller; 15 a copy transfer charger; 16 a separating charger; 17 a cleaner; 20 a cassette; and 21 a paper feed roller.
An image signal which is given from a host computer is transmitted through the laser driving circuit 1 and actuates the laser beam emitting device 2. A laser beam emitted from the laser beam emitting device 2 scans on the surface of the photo sensitive drum 4 by an optical system (not shown) and polygonal mirror 3, so that a latent image is formed onto the drum 4. The toner is transferred onto the surface of the drum 4 in accordance with the latent image and is developed by the developing device 6. The developed image on the drum 4 is transferred onto the copy transfer paper 11 by the copy transfer charger 15. The image transferred paper 11 is then separated from the drum 4 by the separating charger 16. Thereafter, the surface of the drum 4 is cleaned by the cleaner 17 for preparation in the next use. The paper 11 is picked up from the cassette 20 by the paper feed roller 21 and is conveyed by the conveying roller 13 and is fed to the registration roller 14 section. In the inoperative mode, the registration roller 14 abuts on the front edge of the paper 11 and is driven at a proper timing when the front edge of the toner image on the drum 4 coincides with the front edge of the copy transfer paper, thereby preventing that the positional relation between the toner image on the drum 4 and the paper 11 is deviated.
However, the position of the toner image on the drum 4, the position of the front edge of the paper 11, and the like, that is, the relative positional relation between the toner image on the drum 4 and the paper 11 cannot help fluctuating within a predetermined range due to errors of the attaching positions of various parts constructing the apparatus and errors of the generating timings of control signals which are caused due to an error of a reference clock frequency.
Therefore, when an image signal from the host computer is intended to be fully recorded onto the whole paper, the toner corresponding to the peripheral edge portion of the paper of the toner image on the drum 4 is not transferred but remains on the drum 4. Therefore, the untransferred toner is dispersed into the apparatus and the primary charger 5, copy transfer charger 15, separating charger 16, and the like are polluted. Thus, when the apparatus is used for a long time, there occurs a problem on quality such as image variation, stripe, or the like.
On the other hand, there is also a case where the copy transfer paper is hard to be separated from the drum and the paper jam occurs.
To prevent such problems, in general, for the image signal from the host computer, the signal corresponding to the presumed peripheral edge portion of the paper is forcedly cut on the LBP side and a blank is formed.
FIG. 17 shows an example of a timing chart to form a blank in the conventional apparatus.
A front edge signal of the image signal which is given from the host computer is transferred to the laser beam emitting device 2 through the laser driving circuit 1 after an elapse of .tau..sub.0 seconds from a laser signal reference such as vertical sync signal VSYNC indicative of the start of one screen, horizontal sync signal HSYNC indicative of the start of one line, or the like. The signal from the front edge signal of the image signal to the back edge signal after an elapse of .tau..sub.i seconds is written onto the drum 4.
As the horizontal sync signal HSYNC, a beam detecting signal BD which is generated when the reference position of the laser beam which is scanned is detected is used.
A blank is formed by cutting the signal by only the amount of .tau..sub.b seconds in response to the front and back edges of the image signal. That is, at the front edge of the image signal, the signal in a range from .tau..sub.0 seconds after the laser signal reference to (.tau..sub.0 +.tau..sub.b) seconds is cut. At the back edge, the signal in a range from (.tau..sub.0 +.tau..sub.i -.tau..sub.b) seconds after the laser signal reference to (.tau..sub.0 +.tau..sub.i) seconds is cut.
After an elapse of .tau..sub.1 seconds from the laser signal reference, the driving of the registration roller 14 is started so that the front edge of the image signal coincides with the front edge of the paper 11. The value of .tau..sub.1 is calculated by the following equation. ##EQU1## where, l.sub.1 (mm): distance from the laser writing position on the photo sensitive drum 4 to the copy transfer position,
l.sub.0 (mm): distance from the registration roller 14 to the copy transfer position, PA1 v (mm/sec): peripheral velocity of the drum 4.
FIG. 16 shows an example of l.sub.0 <l.sub.1. However, when l.sub.1 <l.sub.0, there is a relation of .tau..sub.1 <.tau..sub.0. In the formation of the blank in the foregoing conventional example, the front and back edges of the image signal have been cut by only the same length .tau..sub.b.
FIG. 18 is a diagram showing a state in which the blanks and image signal formed as mentioned above are shown on presumed paper.
That is, FIG. 18 shows the image signal obtained by synthesizing the image signal given from the host computer and the blank signal forcedly formed on the LBP side by giving the concept of a bit map. Blanks A, B, C, and D are formed in correspondence to the front, back, left, and right edges of the presumed paper, respectively. W denotes a paper width in the main scan direction of the laser beam and L indicates a paper length in the subscan direction of the laser beam or in the rotating direction of the drum 4.
The dimensions of the blanks are set such that A (mm)=B (mm) or C (mm)=D (mm) in correspondence to the blank signal .tau..sub.b.
A practical example will now be described hereinbelow. In the example, the blanks having the dimensions of A=B=C=D=2.5 (mm) are formed. Actually, since there is an error of oscillating frequency of the quartz oscillator as a reference of a clock signal on signal control, the values of the blanks have errors. The blank errors are obtained by multiplying a predetermined ratio to the time (distance) (t.sub.0 seconds in the case of the front edge A and (.tau..sub.0 +.tau..sub.i -.tau..sub.b) seconds in the case of the back edge B) from the laser signal reference to each blank signal on the timing chart of FIG. 16. However, in general, since .tau..sub.0 <<.tau..sub.i and .tau..sub.b <<.tau..sub.i, the error of the blank in the edge portion in which the distance from the laser signal reference is larger increases more.
Table 1 shows an example in the case where the paper size is set to the A4 size (W=210 mm, L=297 mm), the distance between the laser signal reference VSYNC and the front edge of the image is set to 5 mm, the distance between the laser signal reference HSYNC and the left edge of the image is set to 10 mm, the reference blank amount is set to 3.5 mm, and the error of the control signal is set to .+-.0.2%.
TABLE 1 ______________________________________ (unit: mm) A B C D ______________________________________ Blanks on 3.5 .+-. 0.1 3.5 .+-. 0.6 3.5 .+-. 0.1 3.5 .+-. 0.5 image signal ______________________________________
On the other hand, the blank width on the final print is influenced by the factors of errors from the ideal image position (a magnification error which is caused by the optical system when a latent image is formed by the laser, a registration error and oblique movement amount regarding the conveyance of the paper, and the like) and by dimension errors of the paper itself, so that it will be obvious from Table 2 that a side having no blank exists on the paper with a certain probability.
TABLE 2 ______________________________________ (unit: mm) Synthe- Tolerance concerned sized Width Obli- value of Magni- que Size of blank fica- Regis- Move- of tole- on tion tration ment paper rances print ______________________________________ A -- 0 .+-. 2.0 0 .+-. 0.7 -- 0 .+-. 2.2 3.5 .+-. 2.3 B 0 .+-. 3.0 0 .+-. 2.0 0 .+-. 0.7 0 .+-. 0 .+-. 3.8 3.5 .+-. 4.4 1.0 C -- 0 .+-. 2.0 0 .+-. 1.0 -- 0 .+-. 2.3 3.5 .+-. 2.4 D 0 .+-. 2.1 0 .+-. 2.0 0 .+-. 1.0 0 .+-. 0 .+-. 3.3 3.5 .+-. 3.8 1.0 ______________________________________
The actual variations of the tolerances have a normal distribution. The overlap of the various tolerances is not given by the simple sum but is given by the square of the sum of the values which are obtained by squaring each tolerance. On the other hand, the reason why the "magnification" and "paper size" of the sides A and C have no tolerance is because those sides are used as reference sides to measure the tolerances. That is, all of the "magnification", "registration", and "oblique movement" in Table 2 are the amounts which are measured by the image on the final print and the specified values are predetermined to limit those amounts. The "magnification" is measured by using the paper edge (left edge C in the example) on the reference side in the main scan direction of the laser beam and the paper edge (edge A in the example) on the reference side in the subscan direction as references. Since the paper is fed on the basis of the front edge A and either the right or left paper edge (left edge C in the example) as references, the errors are accumulated at the paper edges on the opposite sides, respectively. Therefore, in general, the synthesized values of the tolerances at the front edge A and back edge B or at the left edge C and right edge D differ.
However, since the blanks on the image signal are formed such that A=B and C=D, there are the following inconveniences.
(1) In certain paper edge portions (front edge A and left edge C in the example), the signal is cut more than it is needed, thereby narrowing the signal region which can be effectively used.
(2) On the contrary, in the other paper edge portions (back edge B and right edge D in the example), the blanks lack and there occurs a case where the toner image is not transferred but remains onto the photo sensitive drum 4.
In the case of using the LBP as a conventional line printer, in general documents, blanks are frequently formed in the peripheral edge portions of the paper. Therefore, such inconveniences are not so serious. However, in the case of handling image information as in the case of using the LBP as an output printer of an electronic file or image reader, or the like, it is demanded to write information on the whole region of the paper. The signal region which can be effectively used must be widened as large as possible and a consideration must be paid such that no toner image remains on the photo sensitive drum 4. Such considerations lack in the conventional blank formation.
On the other hand, in U.S. patent application No. 779,107 and the like, there has been disclosed an image recording apparatus having the functions to print on both sides of a copy transfer paper and to print on a single side of a copy transfer paper a plurality of times. In such an apparatus, the running accuracies of the papers differ in the printing operations of the first and second surfaces due to the difference of the paths of the paper or the like. Therefore, there is a case such that although blanks are formed on the first surface, no blank is formed on the second surface, so that the image is deviated out of the paper.
Particularly, in the case of transferring by using the copy transfer roller, there is a drawback such that the toner remaining on the drum without being transferred is deposited onto the copy transfer roller, so that the back surface of the next copy transfer paper becomes dirty or the like.

Image recording forming blanks in peripheral edges


A zoom optical system includes first through fourth lens groups having negative-positive-negative-positive optical powers. Assuming that a curvature radius of an object-side lens surface of a negative lens element in the first lens group is r1, a curvature radius of an image-side lens surface of the negative lens element in the first lens group is r2, a focal length of the third lens group is f3, a focal length of the entirety of the optical system at the wide angle end is fw, a focal length of the entirety of the optical system at the telephoto end is ft, and an average refractive index of positive lens elements in the second lens group is nd2p, the zoom optical system satisfies the conditional expressions:0<(r1+r2)/(r1−r2)<1.0−0.9<f3/√{square root over ( )}(fw×ft)<−0.41.6<ndp2.

1. Field of the Invention
The present invention relates to a zoom optical system for use in an optical unit or a like device, and more particularly to a zoom optical system having a zoom ratio of about two to five times, as well as an image sensing device incorporated with the zoom optical system, and a digital apparatus loaded with the image sensing device.
2. Description of the Related Art
In recent years, digital cameras are rapidly spread, and are widely used not only as means for inputting images into a personal computer, but also as a tool for keeping photos, as well as conventional silver halide cameras. In particular, digital cameras whose zoom ratio is about three times are widely spread in the aspect of a compact size and superior usability. As the digital cameras are widely spread, a demand for a miniaturized zoom lens is increased. Miniaturization in this context embraces miniaturization both in the size of an optical unit in use, and the size of the optical unit in a lens barrel collapsed condition. Also, since the number of pixels of an image sensor is being increased year by year, there is a demand for higher optical performance. Further, there is a demand for high optical performance, as compared with a conventional arrangement, in an apparatus such as a cam recorder primarily used in recording moving images, considering a still image photographing function and a demand for compatibility with high definition devices.
As a zoom lens system capable of satisfying the aforementioned demands, a three-group zoom lens is widely known, wherein a first lens group having a negative optical power, a second lens group having a positive optical power, and a third lens group having a positive optical power are arranged in this order from the object side toward the image side, as disclosed in e.g. US2005/0259334A1 (hereinafter, called as "D1"). The three-group zoom lens has a reduced error sensitivity resulting from decentering, and is feasibly producible, in addition to high optical performance at a relatively small size.
There is also known a four-group zoom lens, wherein a first lens group having a negative optical power, a second lens group having a positive optical power, a third lens group having a negative optical power, and a fourth lens group having a positive optical power are arranged in this order from the object side, as disclosed in e.g. U.S. Pat. No. 7,042,651B2 (hereinafter, called as "D2"). The four-group zoom lens is advantageous in miniaturizing the optical system, without unduly increasing the optical power of the second lens group or the moving amount of the second lens group, by distributing a zooming load to the second lens group and the third lens group while partially overlapping the moving ranges of the second lens group and the third lens group at the time of zooming.
In the zoom optical system disclosed in D1, the zooming load is concentrated to the second lens group. This necessitates securing the moving distance of the second lens group depending on an intended zoom ratio, or increasing the optical power of the second lens group without increasing the moving distance of the second lens group in order to attain the intended zoom ratio. The former arrangement may obstruct miniaturization of the optical system, and the latter arrangement may make it difficult to correct various aberrations resulting from increasing the optical power. In the zoom optical system disclosed in D1, a meniscus lens element is used as a lens element in the first lens group. Accordingly, the thickness of the optical axis direction of the first lens group may be unduly increased, which may obstruct miniaturization of the optical unit in a lens barrel collapsed condition.
The zoom optical system disclosed in D2 has not sufficiently accomplished miniaturization. The zoom optical system in D2 has a great distortion aberration at a wide angle end.

Zoom optical system, image sensing device, and digital apparatus


Novel tools and techniques are provided for testing a data connection (e.g., network connection and/or packet-based service connection) and determining a performance condition of the data connection. The data connection may depend on conditions of an access network and/or a local area network. In some embodiments, a local performance test device may be in communication with an access network and/or a local area network. The local performance test device may receive a request to test the access network and/or the local area network. The local performance test device may further be configured to analyze the access network and/or the local area network to determine whether a data connection issue is occurring on the access network and/or the local area network. Once the local performance test device determines where a performance issue is occurring, the local performance test device may send the result of the test to a requesting device.

The performance of a data connection (which might include, without limitation, a network connection, and/or a packet based service connection, or the like) for an end user is typically determined by the performance of a service provider network (and/or an access network) and/or a local area network of an end user.
Traditionally, users that questioned the performance of an end user's network connection relied on a test server hosted in the service provider network or hosted in another network (e.g., the Internet, an access network, a core network, a third party network, and/or the like) to perform test measurements and determine performance of the network. These test servers hosted in the network could return network performance information. However, these test servers hosted in the network could not determine whether a particular performance issue was occurring on a customer's local area network, a device communicatively coupled to the local area network, an access network or some other network, or a node in one or more of such networks. Thus, a user could not determine which data or network connection (i.e., a customer's local area network, an access network, a service provider network, a third party network, a packet-based service network, and/or the like) needed to be improved and/or repaired.
Hence, there is a need for more robust and scalable solutions for testing an access network and/or a local area network, and for allowing a user to test an access network and/or a local area network to determine whether a performance issue is occurring in an access network and/or a local area network.


Apparatus for igniting a main gas mixture to be burnt in a combustion chamber includes conduit systems for separately feeding an oxygen-bearing gas and a combustible gas into an ignition region. At least a part of at least one of the conduit systems is formed as an electrical heating resistance thereby to raise the temperature of the gas component flowing therein so that when the components are mixed in the ignition region, ignition of the ignition gas mixture will occur, thereby igniting the main gas mixture. The apparatus also includes means for detecting the temperature of the heated gas component or components flowing through the conduit systems, and/or the temperature of the gas mixture ignited in the ignition region.

It has been found that, under certain conditions, it may be difficult to ignite a combustible gas mixture, for example a gas mixture comprising hydrogen and air. This is particularly the case when the combustible gas mixtures are under high pressure.
An example which may be mentioned in this connection is the hydrogenating gasification of solid carbon. It is necessary for the hydrogen which is used as the gasification agent to be raised to a temperature which is suitable for gasification, and which may be 900.degree. C. for example depending on the nature of the coal to be gasified. Conventional heating means, for example heat exchangers, are not normally sufficient to achieve such a temperature. Consequently, a part of the hydrogen must be burnt in order to reach the required temperature level.
Previously proposed methods of igniting such a gas mixture have been found to be unsatisfactory from the point of view of reliability, in particular in regard to safety requirements. If for example hydrogen, methane, heating or fuel gas or the like are mixed, individually or in mixture with each other, with an oxygen-bearing gas such as air, in most practical cases it is necessary to ensure that the reaction between the constituents of the mixture and therefore combustion occurs at the location of the mixing operation, under controllable conditions, as otherwise there is the danger that the combustible mixture may undergo combustion in a manner which is uncontrolled in respect of time and/or location and/or amount and/or speed, as by exploding.


A trailer hitch facilitates coupling between a towing vehicle and a trailer where their respective coupling members are in close proximity, but not exact registration. The hitch is capable of being disengaged from a retracted locked position and of being moved forward relative to the trailer as well as in a lateral direction to permit ready coupling of the trailer and towing vehicle. After coupling is completed, the towing vehicle exerts rearward force against the hitch, causing the hitch to abut and be centered by a centering frame. An automatic latching mechanism completes the coupling by locking the hitch in retracted position. A back-up pin type lock precludes accidental uncoupling.

This invention relates to improvements in trailer hitches and especially to hitches used in situations where repeated hitching and unhitching operations must be made quickly, easily, and safely.
During a hitching operation, difficulty in the past centered around coupling the draft member of the trailer to the hitching means of the tractor. Where registration of the draft member and the hitching means was not precise, the operator was faced with either jockying the towing vehicle or moving the trailer to effect alignment. Both of these alternatives proved difficult and time consuming.
The prior art discloses a number of attempts towards remedying the problem. Demarest, U.S. Pat. Nos. 2,820,649 and 2,871,029, as well as Lyons U.S. Pat. No. 3,860,267 and Allen U.S. Pat. No. 4,042,254, show coupling mechanisms which permit hitching a towing vehicle to a trailer where they are merely in reasonably close proximity, rather than in precise alignment.
There is, however, considerable room for improvement.