A method for reducing aliasing effects in scanning beam microscopy, comprises generating a plurality of successive images of the same object, wherein each image is shifted in the vertical direction with respect to the preceding one by a sub-pixel distance and then averaging all the images together.

When designing a beam scanning microscope, there is a trade-off between various operational parameters. A particularly important relationship is that between the size of the beam spot used to scan the surface, and the resolution of the microscope: the smaller the beam spot size, the higher is the resolution. Since the resolution is one of the most important features of a microscope, all systems are designed to have smallest possible beam spot size. Usually a small beam spot size is maintained even with large field of view.
When a two dimensional image of secondary electrons (SE) or back-scattered electrons (BSE) is produced, the pixel dimensions should be smaller than the spot size in order to reconstruct the information properly (Nyquist sampling theorem). If an improper ratio between the pixel size and the spot size is employed, and the information contains high frequency components, the information will be undersampled and aliasing effects will be generated. Aliasing errors, which are well known in the art, are exemplified in FIG. 1A, which is a scanning electron microscope (SEM) image of a photoresist on a silicon wafer. The aliasing errors are especially obvious at the fringes of the dark squares in the image, which are unequal in their intensity (Moire fringes). As a result, the squares appear contorted. In contrast, FIG. 1B, which is an image of the same object taken according to the invention, as more fully described below, is essentially free from aliasing effects. This is apparent from the equal light distribution along the fringes of the dark squares in the image. As a result, the squares appear undistorted.
In all beam scanning devices, where the beam is scanned either in a raster manner or in a bi-directional manner, the sampling is carried out in a different way in the different axes. Along the horizontal (fast) scanning axis, the pixel size is defined by determining a specific sampling time. Thus the pixel size in this axis is defined by the sampling time interval, multiplied by the beam linear speed. In the horizontal axis the actual spot size is smeared during the sampling time. A proper match of the sampling bandwidth, as known and easily carried out by the skilled person, usually compensates for proper sampling of the data. In the vertical axis, on the other hand, the pixel dimension is defined by the vertical distance that the beam travels from a given scanning line to the next one. When the pixel dimension in the vertical direction exceeds a proper ratio of the spot size in this direction, undersampling phenomena may occur (for object information that has high frequency components in the vertical direction).
There are two common ways to overcome aliasing effect. The first way involves generating an image with sufficient number of pixels at all fields of view, i.e., increasing the number of pixels in the vertical and horizontal direction. This method is discussed in detail in "New Generation Scanning Electron Microscope Technology Based On The Concept Of Active Image Processing", [Esikahu Oho et al, Scanning Vol. 19 483-488, 1997]. This method, also called "active image processing", for removing the effects of aliasing errors, employs a procedure by which a large amount of data is acquired, and is then reduced by averaging into new pixel data. This procedure is efficient to remove aliasing errors, but presents other substantial drawbacks, inasmuch as when using this method one is required to generate larger and larger images the bigger the field of view is, which is a major disadvantage when further image processing is required.
The second method involves increasing the spot size to match it to the sampling pixel size. This can be done symmetrically or asymmetrically, by increasing the spot size in one direction more than in the other. This can be done very simply by defocusing the beam or by more complicated electron optics means. The major drawback of this method is that it either reduces the actual depth of focus of the system (in the first case), or involves a complicated control over the beam shape electron optics (in the second case). Moreover, it requires increasing spot size in a non-symmetrical way in the two axes.
It is therefore clear that the art has not yet provided a simple and efficient way to overcome the aforesaid drawbacks and to eliminate aliasing effects in scanning beam microscopy.
It has now been found that by increasing the number of pixels in the vertical direction, by generating a plurality of successive images of the same object, wherein each image is shifted in the vertical direction by a distance smaller than the distance between two lines, and then averaging all the images together, a substantial reduction of the aliasing effect can be obtained. This method, which is explained in more detail below, further has the advantage of providing an enhanced signal-to-noise ratio, which would not be obtained by using the above prior art methods of modifying the electron beam shape or defocusing. Furthermore, the method of the invention avoids enlarging the pixel number in both vertical and horizontal directions, which is necessary for the above-described method of Oho et al.
Therefore, the method of the present invention avoids expenses in terms of computer power and scanning ability and expenses in terms of beam shaping means associated with the various prior art methods, while at the same time, maintaining the focus and even reducing the signal-to noise ratio.
It is therefore an object of the present invention to provide a method for eliminating the undersampling effect in scanning beam microscopes, without the need to defocus the beam, or to generate large format images.
It is another object of the invention to provide apparatus for eliminating such undersampling effects.
Other objects of the invention will become apparent as the description proceeds.

Method for reducing aliasing effects in scanning beam microscopy


A method, system and article of manufacture for providing a spy-resistant keyboard. The spy-resistant keyboard provides a user with additional protection against unauthorized observers while the user is interfacing with a system implementing the spy-resistant keyboard. The keyboard may include a number of tiles with a number of user-selectable characters randomly associated with each tile. A spy-resistant keyboard may also include a number of movable tiles with user-selectable characters. Before a user selects a user-selectable associated with one of the tiles, all the user-selectable characters in the tiles are at least blanked to avoid unauthorized viewing of a chosen tile.

One of the most popularly used and simple methods for providing access to computer systems, secure areas, financial transaction systems and others is by password entry through a keyboard or keypad. A visual display unit is often associated with such systems. For example, a standard method for password entry routinely used for various access control situations is the entry of alphanumeric password characters through a standard keyboard or a numeric keypad. Normally, the user's key entry is not revealed on the screen directly. Rather, an asterisk "*", or some other character is displayed in response to each entry of a password character.
The use of touch screens or "soft keyboards" in conjunction with computer system displays has increased significantly. For example, touch screens employing the use of a conventional soft keyboard are commonly used with tablet personal computers, personal digital assistants (PDAs), laptop computers, wireless devices, electronic whiteboards (e.g., Smartboards) and other such devices. Furthermore, conventional soft keyboards are also being used with systems that require the use of physically large display devices, such as a system that employs the use of a large plasma screen or projection monitor. The use of a touch screen employing a soft keyboard often eliminates the need to use inconvenient physical keyboards. At the very least, touch screens employing soft keyboards may be used in an advantageous manner with limited space devices.
A conventional soft keyboard functions like a physical keyboard, except that users touch an on-screen image-map to type input information. FIG. 1 illustrates a display 10 that includes a conventional soft keyboard 20. The display 10 shown in FIG. 1 also includes a password entry region 30 that includes a user input field 40. The display 10 may be used in conjunction with a variety of devices, such as computer systems, secure access systems, financial transaction systems, and others.
As is further illustrated in FIG. 1, the conventional soft keyboard 20 includes various keys that may be used to enter text similar to a traditional keyboard. In the case of the display 10, a user simply touches a desired alphanumeric character represented by one of the keys 50 in order to enter information into the user input field 40. For example, a user may enter a series of alphanumeric characters in the user input field 40, and then press the "enter" key in order to gain permissible access to a system the display 10 is interfaced with.
Whether a password is entered via a conventional hardware keyboard, or a conventional soft keyboard, it is possible that an unauthorized person may observe the sequence of key entries processed through the keyboard and make a quick guess about the content of the entered password. While the frequent change of authorized passwords can prevent this possibility to some extent, an unauthorized person can still exploit access to a system before the password is changed. In addition, in many systems such as automatic teller machines, a user's password or pass code is usually infrequently changed.
Conventional soft keyboards, such as the conventional soft keyboard 20 used in conjunction with the display 10, are even more susceptible to unauthorized viewing by one or more observers than a conventional hardware keyboard. This is because an interface such as a conventional soft keyboard depicted on a display is often intrinsically observable. One or more observers watching a user enter characters via a soft keyboard can easily reconstruct text that has been entered. This is a problem exacerbated by the general operational characteristic of a soft keyboard. In particular, as is known, when a user enters text with a soft keyboard, letters, numbers and/or symbols interfaced with provide a highlighting effect so the user knows a selected key has been properly chosen. For example, depressing a key on a soft keyboard may cause the selected key to momentarily illuminate or highlight so that it is obvious to the user that the key has been selected. Even without this visual feedback, an observer could still watch the physical actions of the user to determine what has been typed. The unauthorized watching of selected keys on a soft keyboard or the like is an activity known as shoulder surfing.
Naturally, a user typing on a conventional soft keyboard may take precautions that make it more difficult for one or more unauthorized observers to obtain an entered password or other such security related text. For example, a user may physically obscure the display so that one or more unauthorized observers cannot see the conventional soft keyboard as alphanumeric data is entered thereby. However, this can be difficult when using displays in places and locations that make blocking inconvenient, or when the display is physically larger than a user's body.
In the case where the display is physically larger than the user's body, it may be impossible to conceal the input of a password or other such security related text from one or more unauthorized observers. Therefore, when a conventional soft keyboard is employed on a display, and the display is so large that it makes it impossible to block others from viewing a user's use of the conventional soft keyboard, any text that is input using the soft keyboard is intrinsically at risk of being compromised.
Alternatively, or in combination with a blocking strategy, a user may attempt to confuse one or more unauthorized observers by quickly adding and deleting characters that are not part of a password or security code being entered via a conventional soft keyboard. However, this technique usually increases the number of mistyped passwords and generally does not add much security against one or more unauthorized observers. Moreover, taking intentional actions to protect one's password is time consuming and therefore generally undesirable.


The present disclosure relates to a method for monitoring oxygen level of an environment. The method comprises receiving at least one image of the environment comprising plurality of users from a capturing device. Then, at least one region of interest of each of the plurality of users is detected in the at least one image. A video plethysmographic waveform is generated by analyzing the at least one region of interest. Further, Peripheral Capillary Oxygen Saturation (SPO2) based on the video plethysmographic waveform is determined. Thereafter, oxygen level of the environment is determined by averaging the SPO2 level of each of the plurality of users. The determined oxygen level of the environment is compared with predefined oxygen level of the environment and an appropriate action is performed based on the comparison.

Oxygen concentration in the atmosphere needs to be around 20% of the total air volume for humans to breathe effectively. If the oxygen level decreases, humans face problems such as increase in heart rate, increase in respiration rate, fatigue, emotional upset, nausea, vomiting, etc.
It is observed that the oxygen level drops severely under various scenarios, such as, high altitude, underground places, places with concentrated gathering of people, etc. For activities like mineral excavation, miners need to go inside the mines which are deep underground pocket mostly having very low oxygen level. An example of a place having high concentration of people may be a theater or a movie hall.
Currently, there exist several approaches to detect the oxygen level in a place. However, the existing mechanisms are based on sensors which directly measure the oxygen level in a particular area or place. These sensors need to be spread across a place and placed at appropriate positions so as to get a right value. In many scenarios, like in the case of a mine, numerous such sensors need to be used to and are at times difficult to cover the whole area.
Alternatively, there exist few other mechanisms of detecting worker or person health condition which are indicative of oxygen level in that surrounding. However most of these mechanisms are intrusive in nature. Systems collect physiological parameters of the worker through wired or wireless means and then derive the condition of the person/worker based on such data.

Method and a system for monitoring oxygen level of an environment


A component mounting method for successively mounting electric components on a printed circuit board, which method comprises the steps of recognizing the position of an electric component retained by a suction nozzle by the effect of a suction force; recognizing the predetermined mounting position on a printed circuit board or any other suitable substrate, at a location spaced a predetermined distance from the printed circuit board; mounting the electric component after the latter has been aligned with the predetermined mounting position on the printed circuit board; and recognizing, through the suction nozzle, the electric component to determine if the electric component has been mounted properly after the suction nozzle has been elevated to a position spaced a predetermined distance upwardly from the printed circuit board. In the event that the latter has been mounted incorrectly, information indicative of an incorrect mounting of the electric component is recorded in a control data.

1. Field of the Invention
The present invention generally relates to the mounting of electric component parts successively on a printed circuit board by the utilization of a suction force for picking up electric component parts.
2. Description of the Prior Art
In order for an electric component to be mounted on a printed circuit board so accurately and so correctly as to allow the electric component to assume a predetermined position on the printed circuit board, the conventional practice makes use of a vision sensing system including video cameras for recognizing the position of the printed circuit board at which the electric component is to be actually mounted and also for recognizing the position of the electric component retained by the mounting head. When the component mounting apparatus is in operation, the system is cyclically sequenced to cause the video camera in the mounting head to recognize the position on the printed circuit board at which an electric component is to be mounted; then to cause the mounting head to be moved to a component supply station to pick up the electric component; to cause the video camera, fixed installed at a predetermined position on the path of travel of the electric component from the component supply station towards the component mounting station, to recognize the position of the electric component being transported towards the mounting station; to cause the electric component to be actually mounted so as to assume the predetermined position on the printed circuit board which has been recognized by the video camera; and finally to cause the video camera in the mounting head to recognize the position on the printed circuit board at which the next suceeding electric component is to be mounted.
According to the above discussed prior art component mounting method, the recognition of the electric component having been retained by the suction nozzle and the recognition of the mounting position on the printed circuit board are performed separately. Accordingly, not only is a relatively long time required to finish the task of recognition, but also a limitation is encountered in reducing the tact time incurred during the component mounting operation and also in improving the mounting accuracy. Considering the recent trend that the spacing between each neighboring lead lines extending outwardly from an electric component is reduced with an increase in number of the lead lines, demands have been made recently for achieving a highly accurate mounting of electric components and, therefore, the problems inherent in the prior art component mounting method can no longer be negligible.
Also, in order to avoid any possible spoilage of one or both of the electric component and the printed circuit board only because of a failure of the electric component to be properly mounted and/or a failure of the printed circuit board to receive the electric component, inspection is required to determine if the electric component has been properly mounted. According to the prior art component mounting method, not only is this inspection carried out separtely from the component mounting operation, but also the adjustment or repositioning of the electric component mounted incorrectly is performed manually, the productivity is relatively low.

Matsushita Electric Industrial Co., Ltd.


A cap with electromagnetic proportional valve, includes a pilot cap mounted on a valve housing and defining a pilot chamber, and an electromagnetic proportional valve mounted on the pilot cap and adapted to control a pressure of a working fluid supplied to the pilot chamber. The pilot cap includes a supply port into which a working fluid of a fluid pressure supply source is supplied, a discharge port from which the working fluid is discharged to the tank, a primary pressure passage which leads the working fluid at a primary pressure to the electromagnetic proportional valve from the supply port, a secondary pressure passage which leads the working fluid whose pressure is reduced to a secondary pressure by the electromagnetic proportional valve to the pilot chamber, and a drain passage which leads the working fluid discharged from the electromagnetic proportional valve to the discharge port.

A control valve adapted to control a flow of a working oil by controlling a pilot pressure through an electromagnetic proportional valve is known (see JP2010-127373A). In the control valve described in JP2010-127373A, an oil passage which allows a pump to communicate with an electromagnetic proportional valve, an oil passage which allows the electromagnetic proportional valve to communicate with a pilot chamber, and an oil passage which allows the electromagnetic proportional valve to communicate with a tank are provided in a body (valve housing).

Cap with electromagnetic proportional valve


In one embodiment, a computing system includes a switching voltage regulator having at least two inductors formed on a common toroidal core.

Notebook computers are portable computing devices that have become very popular in recent years. Two components that contribute to their portability are the battery and the voltage regulator.
The battery supplies electrical power to the device, typically at a voltage level of 9-13 volts. However, this voltage level is typically higher than the voltage needed by many of the components in these devices. For example, a microprocessor—the brains of the computer—typically operates on approximately one to two volts. Converting the battery voltage to the right level for any given component is the job of the voltage regulator.
In addition to converting the voltage, the voltage regulator has the job of reducing fluctuations in its output voltage as demand for power fluctuates in response to changes in component workload. For example, when a microprocessor shifts from idle to active, it pulls the regulator output voltage downward from its desired level, and conversely, when the microprocessor shifts from active to idle, it pushes the regulator output voltage upward. In either case, a properly functioning voltage regulator quickly responds to the changing load conditions by increasing or decreasing its output voltage to counteract effects of loading. A consequence of the changing load and voltage levels is that the regulator output voltage generally ripples or oscillates back and forth about its desired voltage.
To reduce the magnitude of these ripples and their undesirable effects on processor operations, many computing devices employ a multi-phase voltage regulator. These multi-phase voltage regulators often include two or more separate inductors that are connected so that ripples at the output of one phase are opposite in direction or polarity to ripples on the other phase. The outputs of the two phases are added together, with the opposing ripples partially canceling each other and reducing the magnitude of ripples that reach the microprocessor.
At least one problem recognized by the inventors is that conventional multi-phase voltage regulators often use separate inductors which not only occupy significant space on the motherboard—that is, the printed circuit board that carries many components of the computer system—but also necessitate the use of other large components, such as several 300 microfarad capacitors. Thus, the use of separate inductors ultimately limits the ability of manufacturers to further reduce the size of the motherboard or to add other components to the same size motherboard.
Accordingly, the inventors have recognized a need for alternative circuitry for voltage regulators.

Computer systems and voltage regulator circuits with toroidal inductors


The present invention relates to novel fluorescent dyes, novel fluorogenic and fluorescent reporter molecules and new enzyme assay processes that can be used to detect the activity of caspases and other enzymes involved in apoptosis in whole cells, cell lines and tissue samples derived from any living organism or organ. The reporter molecules and assay processes can be used in drug screening procedures to identify compounds which act as inhibitors or inducers of the caspase cascade in whole cells or tissues. The reagents and assays described herein are also useful for determining the chemosensitivity of human cancer cells to treatment with chemotherapeutic drugs. The present invention also relates to novel fluorogenic and fluorescent reporter molecules and new enzyme assay processes that can be used to detect the activity of type 2 methionine aminopeptidase, dipeptidyl peptidase IV, calpain, aminopeptidase, HIV protease, adenovirus protease, HSV-1 protease, HCMV protease and HCV protease.

1. Field of the Invention
This invention is in the field of intracellular detection of enzymes using fluorogenic or fluorescent probes. The invention relates to novel fluorescent dyes and application of these dyes for the preparation of novel fluorogenic or fluorescent peptide or amino acid derivatives which are substrates of proteases and peptidases. In particular, the invention relates to novel fluorogenic or fluorescent peptide derivatives which are substrates of enzymes involved in apoptosis, such as caspases and the lymphocyte-derived serine protease Granzyme B. The invention also relates to a process for measuring the activity of caspases and other enzymes involved, in apoptosis in living or dead whole cells, cell lines or tissue samples derived from any healthy, diseased, infected or cancerous organ or tissue. The invention also relates to the use of the fluorogenic or fluorescent substrates in a novel assay system for discovering or detecting inhibitors or inducers of apoptosis in compound collections or compound libraries Furthermore, the invention relates to the use of the fluorogenic or fluorescent substrates in determining the sensitivity of cancer cells to treatment with chemotherapeutic drugs. The invention also relates to novel fluorogenic or fluorescent peptide derivatives which are substrates of exopeptidases such as aminopeptidase A and N, methionine aminopeptidase and dipeptidyl-peptidase IV, endopetidases such as calpain, proteases such as HIV proteases, HCMV protease, HSV protease, HCV protease and adenovirus protease.
2. Related Art
Organisms eliminate unwanted cells by a process variously known as regulated cell death, programmed cell death or apoptosis. Such cell death occurs as a normal aspect of animal development as well as in tissue homeostasis and aging (Glucksmann, A., Biol. Rev. Cambridge Philos. Soc. 26:59-86 (1951); Glucksmann, A., Archives de Biologie 76:419437 (1965); Ellis et al., Dev. 112:591-603 (1991); Vaux et al., Cell 76:777-779 (1994)). Apoptosis regulates cell number, facilitates morphogenesis, removes harmful or otherwise abnormal cells and eliminates cells that have already performed their function. Additionally, apoptosis occurs in response to various physiological stresses, such as hypoxia or ischemia (PCT published application WO96/20721).
There are a number of morphological changes shared by cells experiencing regulated cell death, including plasma and nuclear membrane blebbing, cell shrinkage (condensation of nucleoplasm and cytoplasm), organelle relocalization and compaction, chromatin condensation and production of apoptotic bodies (membrane enclosed particles containing intracellular material) (Orrenius, S., J. Internal Medicine 237:529-536 (1995)).
Apoptosis is achieved through an endogenous mechanism of cellular suicide (Wyllie, A. H., in Cell Death in Biology and Pathology, Bowen and Lockshin, eds., Chapman and Hall (1981), pp. 9-34). A cell activates its internally encoded suicide program as a result of either internal or external signals. The suicide program is executed through the activation of a carefully regulated genetic program (Wylie et al., Int. Rev. Cyt. 68:251 (1980); Ellis et al., Ann. Rev. Cell Bio. 7:663 (1991)). Apoptotic cells and bodies are usually recognized and cleared by neighboring cells or macrophages before lysis. Because of this clearance mechanism, inflammation is not induced despite the clearance of great numbers of cells (Orrenius, S., J. Internal Medicine 237:529-536 (1995)).
Mammalian interleukin-1β (IL-1β) plays an important role in various pathologic processes, including chronic and acute inflammation and autoimmune diseases (Oppenheim, J. H. et. al. Immunology Today, 7, 45-56 (1986)). IL-1β is synthesized as a cell associated precursor polypeptide (pro-IL-1β) that is unable to bind IL-1 receptors and is biologically inactive (Mosley et al., J. Biol. Chem. 262:2941-2944 (1987)). By inhibiting conversion of precursor IL-1β to mature IL-1β, the activity of interleukin-1 can be inhibited. IL-1 is also a cytokine involved in mediating a wide range of biological responses including inflammation, septic shock, wound healing, hematopoiesis and growth of certain leukemias (Dinarello, C. A., Blood 77:1627-1652 (1991); diGiovine et al., Immunology Today 11:13 (1990)). Interleukin-1β converting enzyme (ICE) is a protease responsible for the activation of interleukin-1β (IL-1β) (Thornberry, N. A., et al., Nature 356:768 (1992); Yuan, J., et al., Cell 75:641 (1993)). ICE is a substrate-specific cysteine protease that cleaves the inactive prointerleukin-1 to produce the mature IL-1. The genes that encode for ICE and CPP32 are members of the mammalian ICE/Ced-3 family of genes which presently includes at least twelve members: ICE, CPP32Nama/Apopain, mICE2, ICE4, ICH1, TX/ICH-2, MCH2, MCH3, MCH4, FLICE/MACH/MCHS, ICE-LAP6 and ICEre1III. The proteolytic activity of this family of cysteine proteases, whose active site cysteine residue is essential for ICE-mediated apoptosis, appears critical in mediating cell death (Miura et al., Cell 75:653-660 (1993)). This gene family has recently been named caspases (Alnernri, E. S. et. al. Cell, 87:171 (1996)). A death trigger, such as Tumor Necrosis Factor, FAS-ligand, oxygen or nutrient deprivation, viruses, toxins, anti-cancer drugs etc., can activate caspases within cells in a cascade-like fashion where caspases upstream in the cascade (e.g. FLICE/MACH/MCH5) can activate capsases further downstream in the cascade (e.g. CPP-32/Yama/Apopain). Activation of the caspase cascade leads to cell death.
A wealth of scientific evidence suggests that, in many diseases, the caspase cascade is activated when it shouldn't be. This leads to excessive cellular suicide and organ failure. Diseases involving inappropriate activation of the caspase cascade and subsequent cellular suicide include myocardial infarction, congestive heart failure, autoimmune diseases, AIDS, viral infections, kidney failure, liver failure, rheumatoid arthritis, ischemic stroke, neurodegenerative diseases, atherosclerosis etc. Therefore, the discovery of novel drugs that can block or inhibit the activation of the caspase cascade would have wide-ranging impact on the treatment of degenerative diseases of most, if not all, organ systems of the human body.
Caspases are also thought to be crucial in the development and treatment of cancer. There is mounting evidence that cancer cells, while containing caspases, lack parts of the molecular machinery that activate the caspase cascade (Los et al., Blood, Vol. 90, No 8:3118-3129 (1997)). This causes the cancer cells to lose their capacity to undergo cellular suicide and the cells become immortal—they become cancerous.
It has been shown that chemotherapeutic (anti-cancer) drugs can trigger cancer cells to undergo suicide by re-activating the dormant caspase cascade. This may be a crucial aspect of the mode of action of most, if not all, known anticancer drugs (Los et al., Blood, Vol. 90, No 8:3118-3129 (1997); Friesen et al., Nat. Med. 2:574 (1996). Chemotherapeutic drugs may differ in their capacity to activate the caspase system in different classes of cancers. Moreover, it is likely that anti-cancer drugs differ in their ability to activate the caspase cascade in a given cancer (e.g. lung cancer) and in different patients. In other words, there are differences from one patient to another in the chemosensitivity of, e.g. lung cancer cells, to various anti-cancer drugs.
In summary, the excessive activation of the caspase cascade plays a crucial role in a wide variety of degenerative organ diseases, while a non-functioning caspase system is a hallmark of cancer cells. New drugs that inhibit or stimulate the caspase cascade are likely to revolutionize the treatment of numerous human diseases ranging from infectious, cardiovascular, endocrine, kidney, liver and brain diseases to diseases of the immune system and to cancer.
In order to find drugs that either inhibit or stimulate the caspase cascade, it is necessary to develop high-throughput caspase activation (HTCA) assays. These HTCA assays must be able to monitor activation or inhibition of the caspase cascade inside living or whole cells. Ideally, HTCA assays should be versatile enough to measure the caspase cascade activity inside any living or whole cell, no matter what its origin might be: Cancer cells, tumor cells, immune cells, brain cells, cells of the endocrine system, cells or cell lines from different organ systems, biopsy samples etc. Furthermore, such HTCA assays should be able to measure—within living or whole cells—the activation or inhibition of any of the caspase enzymes or any other enzymes that are involved in the caspase cascade. Developing such versatile HTCA assays represents a substantial advance in the field of drug screening.
Currently available HTCA assays do not permit inner cellular screening for compounds that can either activate or inhibit the caspase cascade. There are only cell-free, high-throughput screening assays available that can measure the activity of individually isolated caspase enzymes, or assays that can measure the activity of caspases in dead cells which have been permeabilized by osmotic shock, for example (Los et al., Blood, Vol. 90, No 8:3118-3129 (1997)). But these enzyme assays cannot predict the effect of a compound on the caspase cascade in living cells for the following reasons:    1.) Cell free assays, or assays using dead, permeabilized cells, cannot predict the ability of compounds to penetrate the cellular membrane. This is crucial because the caspase cascade resides in the interior of the cells. In order to be active, a compound must not only be able to modulate the caspase enzyme or enzymes, but it must also be able to penetrate the intact cell membrane. Cell-free assays or assays using dead cells are therefore unable to determine whether or not a compound will be potentially useful as a drug.    2.) Isolated caspases in cell-free assays are highly susceptible to oxidation and to compounds that can cause oxidation of the enzymes. This property of isolated caspases makes cell free caspase screening assays highly susceptible to artifacts and has precluded successful use of these assays for high-throughput screening of combinatorial (or other) chemical libraries. Previous mass screening efforts, using cell-free caspase enzyme assays, have led to discovery of numerous inhibitors which oxidize caspases, but no compound that would be useful as a potential drug. Similar difficulties have been reported by others.    3.) Numerous cellular receptors, proteins, cell constituents and cofactors—many of which are still unknown—can influence the caspase cascade in living cells. Cell-free caspase assays or assays using permeabilized, dead cells do not take into account these cellular receptors and cofactors. Because of this, it is possible that a compound identified in a cell-free or dead-cell caspase assay will not work in living cells. On the other hand, a compound that might inhibit or stimulate the caspase cascade indirectly through one of the cellular receptors or cofactors would be missed entirely in an cell-free or dead-cell caspase assay.    4.) It is highly likely that the caspase cascade functions differently in cells derived from different organs. There is growing evidence that the receptors and cofactors that influence the caspase cascade differ among cell types. Using cell-free or dead cell assays, it would be virtually impossible to identify cell-type or organ specific modulators of the caspase cascade.
A potentially important application of a HTCA assay system for measuring intracellular caspase enzymes or any other enzymes involved in apoptosis is chemosensitivity testing of human cancers. It is known that there is a genetic difference in the susceptibility of human cancers to the currently marketed anti-cancer drugs: For example, lung cancer cells in one patient might be sensitive to Drug A, while another patient's lung cancer might be insensitive to Drug A, but sensitive to Drug B. This pharmacogenetic difference in chemosensitivity of cancer cells from different individuals is a well-known phenomenon.
In the past, attempts have been made to determine the chemosensitivity of cancer cells taken from individual patients prior to designing a treatment regimen with one or more of the marketed anticancer drugs. However, chemosensitivity testing has not found wide-spread use, because the procedures involved have some inherent technical difficulties: The testing is very time consuming (six or more days per screen) and it requires culturing of the cells prior to screening. The cell culture leads to clonal selection of cells and the cultured cells are then no longer representative of the cancer in the patient. A HTCA assay system for quickly measuring intracellular caspase activity could be used to determine very rapidly the chemosensitivity profile of freshly excised cancer cells. If the assay has a high throughput, it would be feasible to test chemosensitivity of multiple samples taken from the same patient, e.g. from different metastases. This information could then be used to design a treatment regimen using combinations of marketed anti-cancer drugs to which the cells showed greatest sensitivity.
It is clear that the need exists for HTCA assays and reagents for such assays that can be employed in drug discovery or diagnostic procedures to quickly detect and measure the activity of compounds that activate or inhibit the caspase cascade or other enzymes involved in apoptosis in the interior of living or dead whole cells. A reagent for this type of cell assay ideally should meet the following conditions: a) there should be a big difference in fluorescence signal between peptide-reporter molecule and reporter molecule after the amide bond in peptide-reporter is cleaved by the caspases or other enzymes involved in apoptosis, preferably the peptide-reporter molecule should be non-fluorescent and most preferably the peptide-reporter molecule should be non-fluorescent and colorless; b) the peptide-reporter molecule should be cell permeable, therefore there should be minimum numbers of hydrophilic groups in the molecule and the size of the molecule should preferably be small; c) the peptide-reporter molecule should preferably not diffuse out of the cell once it permeates the cell membrane; d) the reporter molecule should preferably not diffuse out of the cell once it is liberated from the peptide.
The method of screening apoptosis inhibitors or inducers in whole cells vs cell-free enzyme assay can also be used for the screening of inhibitors of enzymes other than caspases. Traditionally, enzyme inhibitors were first identified by cell-free enzyme assays. Cell cultures were then used for secondary assay to assess activity of the active compounds in intact cells. A cell permeable fluorogenic or fluorescent substrate will enable the screening of inhibitors of proteases and peptidases and other enzymes directly in living whole cells. There are several advantages in whole cell assays vs cell-free enzyme assays. One of the advantages is that in whole cell assays, the inhibitor will have to penetrate the cell to be detected. Since many proteases in living cells are regulated by other proteins, receptors or genes, screening using living cells will allow the identification of small molecule compounds which interfere with cellular proteases by binding to the active site, as well as compounds which modulate protease function by interfering with transcription, translation, biosynthesis, sub-unit assembly, cellular cofactors or signal transduction mechanisms (or viral entry into host cells, in the case of viral proteases). Furthermore, since there is an abundence of aminopeptidases in the cells, these aminopeptidases can be used in the design of fluorogenic or fluorescent substrates for whole cell assay which otherwise will not work in cell-free enzyme assays. Therefore there is a need to develop high throughput screening (HTS) assays and reagents for such assays in whole cells which can be used for drug discovery or diagnostic procedures.
AGM-1470 (also known as TNP-470) is an angiogenesis inhibitor in clinical trials for a variety of cancers. The mechanism of action of AGM-1470 was recently discovered by two independent research groups (Sin, N., et al. Proc. Natl. Acad. Sci. U.S.A. 94:6099-6103 (1997); Griffith, E. C., et al., Chem. Biol. 4:461-471 (1997)). They found that AGM-1470 and analogs are inhibitors of methionine animopeptidase type 2 (MetAP-2). The potency for inhibition of endothelial cell proliferation and inhibition of methionine aminopeptidase activity was determined for a series of AGM-1470 analogs and a significant correlation between the two activities was found.
Since angiogenesis inhibitors are known to be able to selectively kill cancer cells, a cellular screening assay for inhibitors of MetAP-2 may result in novel anti-cancer drugs. Therefore cell permeable fluorogenic or fluorescent substrates for MetAP-2 can be used for the screening of inhibitors of MetAP-2 in endothelial cells which could lead to novel anticancer agents.
Recently, HIV protease inhibitors such as ritonavir and viracept have been shown to be very effective in the treatment of patients infected with HIV. These inhibitors were designed based on the structure of the HIV protease substrate. The activities of these inhibitors were first determined against HIV protease. Active compounds were then tested for inhibition of HIV infection in cell cultures. A cell permeable fluorogenic or fluorescent substrate for HIV protease can be used for the screening of HIV protease inhibitors in HIV infected cells which could speed up the process for the discovery of novel HIV protease inhibitors and lead to new and better treatment for HIV infection. Since HIV protease processes viral precursor proteins at a late stage in viral replication, a cell permeable fluorogenic or fluorescent substrate for HIV protease also can be used to screen compounds which inhibit gene transcription or translation, viral entry, or other key proteins in the early stage of HIV infection. The fluorogenic or fluorescent substrates also could be used for diagnosis of HIV infection, which might be more sensitive than the currently available methods.
Applying the same principle, cell permeable fluorogenic or fluorescent substrates for cathepsin B can be used for the screening of cathepsin B inhibitors. Cell permeable fluorogenic or fluorescent substrates for dipeptidyl-peptidase IV can be used for the screening of dipeptidyl-peptidase IV inhibitors. Cell permeable fluorogenic or fluorescent substrates for renin can be used for the screening of renin inhibitors and cell permeable fluorogenic or fluorescent substrates for adenovirus protease or other viral proteases can be used for the screening of adenovirus protease or other viral protease inhibitors.
U.S. Pat. Nos. 4,557,862 and 4,640,893 disclose Rhodamine 110 derivatives as fluorogenic substrates for proteinases of the formula:
wherein R1 and R2, which are the same or different, are selected from the group consisting of amino acids, amino acid derivatives, blocked amino acids, blocked amino acid derivatives, and peptides. Exemplary (AA)2-Rhodamines and (peptide)2-Rhodamines are (Z-Arg)2-Rhodamine 110, (Arg)2-Rhodamine 110, (Z-Ala-Arg)2-Rhodamine 110, (Z-GlN-Arg)2-Rhodamine 110, (Z-Glu-Arg)2-Rhodamine 110, (Z-Gly-Arg)2-Rhodamine 110, (Z-Leu-Arg)2-Rhodamine 110, (Z-Met-Arg)2-Rhodamine 110, (Z-Phe-Arg)2-Rhodamine 110, (Z-Pro-Arg)2-Rhodamine 110, (Z-Trp-Arg)2-Rhodamine 110, (Z-Val-Arg)2-Rhodamine 110, and (Z-Ile-Pro-Arg)2-Rhodamine 110.
WO 96/36729 discloses compounds or their salts for assaying the activity of an enzyme inside a metabolically active whole cell. The assay compound is said to include a leaving group and an indicator group. The leaving group is selected from the group comprising amino acids, peptides, saccharides, sulfates, phosphates, esters, phosphate esters, nucleotides, polynucleotides, nucleic acids, pyrimidines, purines, nucleosides, lipids and mixtures. The indicator group is selected from compounds which have a first state when joined to the leaving group, and a second state when the leaving group is cleaved from the indicator group by the enzyme. Preferred indicator compounds are said to be Rhodamine 110, rhodol, and fluorescein and analogs of these compounds. The patent application listed many enzymes and substrates of enzymes.
U.S. Pat. No. 5,576,424 disclosed haloalkyl derivatives of reporter molecules used to analyze metabolic activity in cells of the formula:XR-SPACER-REPORTER-BLOCKWherein -BLOCK is a group selected to be removable by action of a specific analyte, to give reporter spectral properties different from those of the substrate; -REPORTER- is a molecule that, when no longer bound to BLOCK by a BLOCK-REPORTER bond, has spectral properties different from those of the substrate; -SPACER- is a covalent linkage; and XR- is a haloalkyl moiety that can covalently react with an intracellular thiol to form a thioether conjugate. Preferred reporter compounds are said to include Rhodamine-110, rhodol, fluorescein and others.

Fluorogenic or fluorescent reporter molecules and their applications for whole-cell fluorescence screening assays for caspases and other enzymes and the use thereof


The present invention provides a method and apparatus for simulating an aerial image projected from an optical system, wherein the optical system includes a pupil and a mask. In general, the method comprises the steps of obtaining parameters for the optical system, calculating a kernel based on an orthogonal pupil projection of the parameters of the optical system onto a basis set, obtaining parameters of the mask, calculating a vector based on an orthogonal mask projection of the parameters of the mask onto a basis set, calculating a field intensity distribution using the kernel and the vector, and obtaining aerial image data from the field intensity distribution.

In lithography, an exposure energy, such as ultraviolet light that is generated in an optical system, is passed from an aperture of the system through a mask (or reticle) and onto a target such as a silicon substrate. The mask typically may contain opaque and transparent regions formed in a predetermined pattern. The exposure energy exposes the mask pattern, thereby forming an aerial image of the mask. The aerial image is then used to form an image onto a layer of resist formed on the target. The resist is then developed for removing either the exposed portions of resist for a positive resist or the unexposed portions of resist for a negative resist. This forms a patterned substrate. A mask typically may comprise a transparent plate such as fused silica having opaque (chrome) elements on the plate used to define a pattern. A radiation source illuminates the mask according to well-known methods. The radiation transmitted through the mask and exposure tool projection optics forms a diffraction-limited latent image of the mask features on the photoresist. The patterned substrate can then be used in subsequent fabrication processes. In semiconductor manufacturing, such a patterned substrate can be used in deposition, etching, or ion implantation processes, to form integrated circuits having very small features.
In a manufacturing process using a lithographic projection apparatus, a pattern in a mask is imaged onto a substrate, which is at least partially covered by a layer of radiation-sensitive material (resist). Generally, lithographic patterning processes are understood by those who practice the profession. Information regarding exemplary processes may be obtained, for example, from the book xe2x80x9cMicrochip Fabrication: A Practical Guide to Semiconductor Processingxe2x80x9d, Third Edition, by Peter van Zant, McGraw Hill Publishing Co., 1997 ISBN 0-07-067250-4.
As the size of lithographically fabricated structures decreases, and the density of the structures increases, the cost and complexity of designing masks additionally increases. One method of reducing costs of lithographic fabrication is by optimizing the lithographic design with a lithographic simulation step prior to the actual manufacturing step. One specific method of lithographic simulation is drawn to simulating the aerial image of the mask. The aerial image is defined as an intensity distribution of light just prior to reaching the resist on a surface of a substrate, when the substrate is exposed via the mask in an exposure apparatus. In order to simulate the aerial image, a layout of a mask and exposure conditions (non-limiting examples include NA: Numerical Aperture, "sgr" (sigma): Partial Coherence Factor) of the lithographic apparatus are typically required as input parameters.
Lithographic apparatus may employ various types of projection radiation, non-limiting examples of which include light, ultra-violet (xe2x80x9cUVxe2x80x9d) radiation (including extreme UV (xe2x80x9cEUVxe2x80x9d), deep UV (xe2x80x9cDUVxe2x80x9d), and vacuum UV (xe2x80x9cVUVxe2x80x9d)), X-rays, ion beams or electron beams. The following have been considered exemplary exposure sources. Light may generally refer to certain mercury emissions, i.e., wavelengths of 550 nm for the f-line, 436 nm for the g-line, and 405 mn for the h-line. Near-UV or UV generally typically refer to other mercury emissions, i.e., 365 nm for the i-line. DUV generally refers to excimer laser emissions, such as KrF (248 nm) and ArF (193 nm). VUV may refer to excimer laser F2, i.e., 157 nm, Ar2, i.e., 126 nm, etc. EUV may refer to 10-15 nm. This last portion of the electromagnetic spectrum is very close to xe2x80x9csoft X-raysxe2x80x9d but has been named as xe2x80x9cEUVxe2x80x9d, possibly to avoid the bad reputation of X-ray patterning. Soft X-rays may refer to 1-15 nm, which may typically be used in X-ray lithography.
Depending on the type of radiation used and the particular design requirements of the apparatus, the projection system may be for example, refractive, reflective or catadioptric, and may comprise vitreous components, grazing-incidence mirrors, selective multi-layer coatings, magnetic and/or electrostatic field lenses, etc; for simplicity, such components may be loosely referred to in this text, either singly or collectively, as a xe2x80x9clensxe2x80x9d.
When the resist is exposed by the aerial image, there is an additional variable in that some of the exposure light is reflected back by the surface of the substrate, and then absorbed by the resist. Accordingly, not only the resist characteristics (regarding, for example, refractive index: Dill""s A,B,C) but also parameters regarding the characteristics of the substrate (e.g., refractive index) should be included as input parameters for simulating the latent image.
The so-called Hopkins model treats the electric field forming the image typically as a scalar and assumes the object being imaged is sufficiently thin so that its effect on the incident field is represented by a multiplicative function. It is advantageous to perform the image formation analysis in the Fourier domain (frequency space) in order to deal with the pupil function of the imaging system rather than the amplitude response function, and with the angular distribution or xe2x80x9ceffective sourcexe2x80x9d rather than with the mutual intensity.
There are several computer programs commercially available that calculate aerial images based on the Hopkins model. For example, the University of California at Berkeley, Department of Electrical Engineering and Computer Science, Berkeley, Calif., 94720, offers a program called SPLAT.
The Hopkins model is used to model the imaging of drawn design features under partially coherent illumination. A major problem in modeling aerial images under partially coherent illumination is the necessity to superimpose and add the effect of each individual illumination source that makes up the partially coherent source. In the Hopkins model, a two-dimensional by two-dimensional transmission cross-coefficient function (xe2x80x9cTCCxe2x80x9d) is pre-calculated, which captures all the effects of the lithographic projection apparatus, including NA, sigma, etc. As taught, for example in Born and Wolf, p. 603, once a TCC is known, systems with partially coherent illumination can be modeled by integrating the TCC over the Fourier transform of the transmission function for the geometrical layout feature under illumination.
Fundamentally, the TCC is a two-dimensional by two-dimensional correlation function with a continuous set of arguments. In practice, an assumption can be made that the feature patterns to be imaged are periodic in space. For such periodic patterns, the TCC has a large, but discrete, set of arguments. The TCC can then be represented as a matrix, with discrete columns and rows. For typical features interesting to the lithographer the size of this matrix is tremendous and restricts the scale and size of features that can be simulated. It is a purpose of any simulation algorithm based on the Hopkins model to reduce the size of this matrix by approximation, while retaining a reasonable degree of accuracy.
An exemplary projection lithography system is illustrated in FIGS. 1A and 1B. In FIG. 1A, light from illumination source 102 is focussed by condenser 104. The condensed light passes through the mask 106, then through the pupil 108 and onto the substrate 110. As shown in FIG. 1B, substrate 110 may comprise a top anti-reflective coating 112, a resist 118, a bottom anti-reflective coating 117, a top substrate layer 114 and a plurality of other substrate layers. As indicated in FIG. 1B, the focal plane may lie within the resist 118.
In the past, several numerical techniques have been applied to reduce the size of the TCC to reasonable scales. In one instance singular value decomposition has been applied to decompose the TCC into its eigenspectrum, sort the resulting eigenvectors in decreasing magnitude of their eigenvalues, and only retain a finite number of eigenvectors in order to approximate the TCC. An exemplary method for optical simulation for the system of FIG. 1A, that uses the Hopkins model, is illustrated in FIG. 2. As illustrated in FIG. 2, at step S202, the lithographic projection apparatus and mask parameters are input in the system. At step S204, the TCC is approximated by an eigenvector diagonalization. At step S206, a two-dimensional table of convolution integrals of the eigenfunctions with a discrete set of normalized rectangles is calculated and tabulated. The article, xe2x80x9cFast, Low-Complexity Mask Designxe2x80x9d, by N. Cobb et al., SPIE Vol. 2440, pgs. 313-326, the entire disclosure of which is incorporated by reference, teaches an exemplary method for completing step S206. Since the resulting table is on a discrete grid of possible layout-features, to attain an acceptable resolution, the table must be large. At step S208, since the TCC has been approximated, the illumination system can be modeled, i.e. the aerial image can be simulated by combining each two-dimensional convolution integral corresponding to each respective rectangle in a given proximity window.
This method has two drawbacks. First, an eigenvector diagonalization is a numerically expensive operation. Thus, for a user to change lithographic projection apparatus conditions, such as NA, sigma, illumination type or lens-aberration, an expensive recalculation of the TCC approximation that limits the use of the simulation tool is required. Second, the eigenspectrum of the TCC is a two-dimensional function. Representing the associated field vectors of the geometrical pattern under illumination requires a two-dimensional lookup table that limits the speed of the field calculation in the Hopkins algorithm. Specifically, since the field vectors are a two-dimensional table, two pointers are needed to access any respective address of data, which increases access time. Further, since the field vectors are a two-dimensional table, they are stored in a portion of the cache. Using a look-up table from a DRAM in a present day CPU is more expensive than performing multiplication because the cache miss penalty is larger than the time to perform the multiplication.
Accordingly, there is needed a method and apparatus for simulating a projection lithography system using the Hopkins model, that does not use a numerically expensive eigenvector diagonalization operation. What is further needed is a method and apparatus for simulating a projection lithography system using the Hopkins model that permits a user to change lithographic projection apparatus conditions, such as NA, sigma, illumination type or lens-aberration without requiring an expensive recalculation of the TCC approximation.
It is an object of the present invention to provide a method and apparatus for simulating a projection lithography system using the Hopkins model that does not use a numerically expensive eigenvector diagonalization operation.
It is another object of the present invention to provide a method and apparatus for simulating a projection lithography system using the Hopkins model that permits a user to change lithographic projection apparatus conditions without requiring an expensive recalculation of the TCC approximation.
It is still another object of the present invention to provide a method and apparatus for predicting the intensity field distribution (xe2x80x9caerial imagexe2x80x9d) at the surface and throughout the resist film of a substrate being irradiated in a lithographic imaging process.
In accordance with the foregoing objectives, the present invention writes the TCC as T(qxe2x80x2q), where q and qxe2x80x2 each are continuous frequencies in two-dimensional Fourier space, q=(qx, qy), qxe2x80x2=(qxe2x80x2x, qxe2x80x2y). The present invention approximates the TCC extremely well as a bilinear form of a basis function with kernel A[ij]. Furthermore, the present invention utilizes a set of orthogonal polynomials. The kernel A[ij] represents a small matrix that efficiently approximates the TCC for a broad range of illumination conditions used in modern lithographic processing. The present invention uses a lower number of arithmetic operations as a result of the use of a one-dimensional look-up table as opposed to the two-dimensional look-up table in the prior art. Furthermore, the one-dimensional look-up table achieves a higher cache hit ratio than a two-dimensional look-up table of the same resolution, thereby providing a more efficient system.
In general, in one embodiment, the invention features a method of simulating an aerial image projected from an optical system, the optical system including a pupil and a mask plane, the method comprising the steps of providing a mask to the mask plane, obtaining parameters for the optical system, calculating a kernel based on an orthogonal pupil projection of the parameters of the optical system onto a basis set, obtaining parameters of the mask, calculating a vector based on an orthogonal mask projection of the parameters of the mask onto a basis set, calculating a field intensity distribution using the kernel and the vector, and obtaining an aerial image from the field intensity distribution.
In one embodiment of the invention, the parameters for the optical system include aberrations.
In another embodiment of the invention, the step of calculating a kernel corresponding to the parameters of the optical system includes the step of generating a table of indefinite integrals based on a recurrence over a seed array of incomplete gamma functions.
In yet another embodiment of the invention, the step of calculating a kernel corresponding to the parameters of the optical system further includes the step of tabulating an array of orthogonal pupil projection coefficients corresponding to respective points in the pupil of the optical system, wherein the optical system is in-focus. More particularly, it further comprises the step of combining sample weights of an illuminator profile of the optical system with the array of orthogonal pupil projection coefficients.
In still another embodiment of the invention, the step of calculating a kernel corresponding to the parameters of the optical system further includes the step of tabulating an array of orthogonal pupil projection coefficients corresponding to respective points in the pupil of the optical system, wherein the optical system is either not in-focus or has aberrations. More particularly, it further comprises the step of combining sample weights of an illuminator profile of the optical system with the array of orthogonal pupil projection coefficients.
In still yet another embodiment of the invention, the step of calculating a kernel corresponding to the parameters of the optical system further includes the step of: tabulating an array of orthogonal pupil projection coefficients corresponding to respective points in the pupil of the optical system, wherein the optical system accounts for effects of diffusion of photoactive compounds in the resist. More particularly, it further comprises the step of combining sample weights of an illuminator profile of the optical system with the array of orthogonal pupil projection coefficients.
In a further embodiment of the invention, the step of calculating a vector corresponding to the parameters of the mask further includes the step of specifying a proximity window within the mask for geometric sampling.
In still a further embodiment of the invention, the step of calculating a vector corresponding to the parameters of the mask further includes the step of decomposing a geometric pattern of the mask into a disjoint set of rectangles and tabulating an array of projections of the rectangles within a proximity window. More particularly, the step of calculating a vector corresponding to the parameters of the mask further includes the step of correcting the array of projections of the rectangles based on the type of mask.
In general, in another aspect, the invention features a method for simulating an aerial image projected from an optical system, the optical system including a pupil and a mask plane, the method comprising the steps of: providing a mask to the mask plane, obtaining parameters for the optical system, obtaining parameters of the mask, projecting the components of electric field vectors to an orthogonal polynomial basis as described in further detail below, the polynomials including polynomials associated with the parameters of the optical system, and approximating the transmission cross-correlation function associated with the optical system based on the orthogonal projection of polynomials.
In general, in still another aspect, the invention features a simulation device operable to simulate an aerial image projected from an optical system, the optical system including a pupil and a mask plane, the simulation device comprising a first parameter obtainer for obtaining parameters of the optical system, a first calculator for calculating a kernel based on an orthogonal pupil projection of the parameters of the optical system onto a basis set, a second parameter obtainer for obtaining parameters of a mask provided to the mask plane, a second calculator for calculating a vector based on an orthogonal mask projection of the parameters of the mask onto a basis set, a third calculator for calculating a field intensity distribution using the kernel and the vector, and an aerial image obtainer for obtaining aerial image data from the field intensity distribution.
In one embodiment of the invention, the first, second, and third calculators are the same calculator.
In another embodiment of the invention, the parameters for the optical system include aberrations.
In yet another embodiment of the invention, the first calculator is operable to generate a table of indefinite integrals based on a fast recurrence over a seed array of incomplete gamma functions.
In still another embodiment of the invention, the first calculator is operable to tabulate an array of orthogonal pupil projection coefficients corresponding to respective points in the pupil of the optical system, wherein the optical system is in-focus.
In still yet another embodiment of the invention, the first calculator is operable to tabulate an array of orthogonal pupil projection coefficients corresponding to respective points in the pupil of the optical system, wherein the optical system is either not in-focus or has aberrations.
In a further embodiment of the invention, the first calculator is operable to tabulate an array of orthogonal pupil projection coefficients corresponding to respective points in the pupil of the optical system, wherein the optical system accounts for effects of photoactive compound diffusion in the resist.
In still a further embodiment of the invention, the second calculator is operable to specify a proximity window within the mask for geometric sampling.
In yet a further embodiment of the invention, the second calculator is operable to decompose a geometric pattern of the mask into a disjoint set of rectangles and tabulate an array of projections of the rectangles within a proximity window. More particularly the second calculator is operable to correct the array of projections of the rectangles based on the type of mask.
In general, in yet another aspect, the invention features a simulation device operable to simulate all aerial image projected from an optical system, the optical system including a pupil and a mask plane, the simulation device comprising a first parameter obtainer for obtaining parameters of the optical system, a second parameter obtainer for obtaining parameters of a mask provided to the mask plane, a first calculator for orthogonally projecting polynomials, the polynomials including polynomials associated with the parameters of the optical system, and a second calculator for approximating the transmission cross-coefficient associated with the optical system based on the orthogonal projection of polynomials.
Additional advantages of the present invention will become apparent to those skilled in the art from the following detailed description of exemplary embodiments of the present invention. The invention itself, together with further objects and advantages, can be better understood by reference to the following detailed description and the accompanying drawings.

Method and apparatus for fast aerial image simulation


An optical filter includes a substrate, and a periodic structure in which a plurality of members formed of silicon are periodically arranged on a surface of the substrate. The filter selectively transmits light of a first wavelength included in light incident on the periodic structure in the direction of the substrate. The members are two-dimensionally arranged with a period of 400 nm to 500 nm. The dimension of the members in the direction parallel to the surface is of 120 nm to 160 nm. A local maximum value of the transmission spectrum of the first wavelength is within the range of 400 nm to 500 nm.

1. Field of the Invention
The present invention relates to an optical filter using guided mode resonance.
2. Description of the Related Art
In recent years, separately from the conventional color filter using pigment, a color filter using guided mode resonance (GMR) or Guided Resonance (GR) Mode has been proposed. The color filter using guided mode resonance takes advantage of a resonance condition between diffracted light and a waveguide mode occurring in a waveguide. Optical filters based on GMR are considered to provide high light use efficiency and a sharp resonance spectrum.
Kanamori et al., in "Fabrication of Transmission Color Filters Using Silicon Subwavelength Gratings on Quartz Substrates", IEEE Photonics Technology Letters, Vol. 18, No. 20, Oct. 15, 2006 (hereinafter referred to as Literature 1) discloses a color filter that includes a one-dimensional diffraction grating formed of silicon and uses the guided mode resonance occurring in the silicon periodic structure.
The filter disclosed in Literature 1 transmits RGB (Red, Green, and Blue) portions of the incident light having a particular polarization component. TE polarized light is made to be incident on a filter for red and a filter for green, and TM polarized light is made to be incident on a filter for blue.
Japanese Patent Laid-Open No. 2007-41555 (hereinafter referred to as Literature 2) discloses a filter that includes a two-dimensional diffraction grating formed of silicon and transmits R and G light. Literature 2 states that making the diffraction grating perfectly two-dimensional can reduce polarization dependency.
The color filter disclosed in Literature 1 uses a one-dimensional diffraction grating, therefore the angle between the grating structure of the diffraction grating and polarized light incident thereon may have various values depending on the angle of incident polarized light, and therefore the transmission property thereof has strong polarization dependency. Such strong polarization dependency causes inconvenience, for example, when the filter is used in an image sensor of a digital camera or the like.
Although Literature 2 discloses that use of a two-dimensional diffraction grating reduces the polarization dependency of color filters for red and green, a color filter for blue, which constitutes the three primary colors, is not achieved.
In view of the use in an image sensor for picking up a color image, it is desirable to achieve a color filter that transmits the three primary colors including blue with a high transmittance.

Optical filter, solid-state imaging element having the filter, and imaging apparatus


An implant for releasing an active substance into a vessel through which a body medium flows. The implant release an active substance into a vessel through which a body medium flows downstream from the location of the implant. A base of a biodegradable material is a carrier of the active substance to be released. The body medium flows past the implant and the active substance is release. The implant is configured so that the active substance does not contact a vessel wall at the location of implant.

For centuries man has attempted to accelerate the healing process of pathological processes and conditions and reduce the symptoms associated with disease by the targeted administration of pharmaceutically active substances. Besides the selection of and search for suitable active substances, one problem resides in making the active substance available at the desired site of treatment. In order to minimise the side effects associated with administration, the release of the active substance should, if possible, be limited exclusively to the site of treatment. Furthermore, it is necessary in most cases, in order to optimise the effect, to maintain a posology as accurately as possible, i.e., to keep the concentration of active substance within specific range limits at the site of treatment over a predeterminable period. Conventionally active substances are applied orally, subcutaneously, intravenously or rectally. The conventional systemic administration of medicines results in considerable complications, particularly in the case of local diseases, e.g., tumours.
For many years there have therefore been increasing efforts to introduce the active substance more specifically into the body of the patient to be treated. The term 'Local Drug Delivery' (LDD) has been established to describe an exclusively local treatment from an implant, i.e., elution of an active substance essentially only into the tissue immediately surrounding the implant. The site of treatment at which the active substance is to exert its pharmacological action therefore lies immediately adjacent to the site of implantation.
An important area of application for LDD systems therefore lies in the improvement in biocompatibility of permanent implants such as stents, cardiac pacemakers or orthopaedic prostheses. In particular, complications caused by the presence of the implant or by the implantation should be reduced or avoided here.
The basic concept behind an administration of active substances that deviates from the LDD systems descried above, which is also applied in this invention, is that of providing a more distinct spatial separation between the site of implantation and the site of treatment. In other words, the active substance released on the implant should not act directly (locally) but should only exert its action in a region of tissue spatially separate from the implant after introduction into the body. The term 'Regional Drug Delivery'—or briefly RDD—will be used in the following to describe this type of regional active substance administration.
In some symptoms, e.g., locally limited tumours, active substances can be administered via the vascular system of the tissue to be treated. For this purpose it is necessary to introduce the implant into a vessel that lies downstream from the treatment site. A state of the art approach consists, for example, in injecting into the vessel a polymeric matrix containing the active substance. The matrix is designed so that it is converted immediately after injection to a tough film which adheres to the vascular walls. This film containing the active substance gradually decomposes, releasing the active substance. However, it is very difficult in practice to achieve such a pinpoint injection into the vessel concerned, which may lead to further complications, due to formation of thrombi for example. Finally, a posology also depends on the thickness of the film, i.e., it is difficult to predict the release characteristic that actually exists.

Implant for releasing an active substance into a vessel through which a body medium flows


In a method of controlling a picture signal processing mode, first and second motion vectors are determined (ME, D.sub.T) for first and second fields, and a picture signal processing mode control signal is obtained by comparing (D.sub.T, -, COMP-R) the first and second motion vectors. The control signal may be transmitted along with, for example, a HDTV signal to give an indication to a TV receiver whether the signal originated from movie-film or from non-movie-film or be generated within the receiver.

The invention relates to a method of and apparatus for controlling a picture signal processing mode. The picture signal processing mode may indicate whether the picture signal originates from movie-film and, more specifically, how the fields of the picture signal relate to the pictures of the movie-film, or whether motion vectors are reliable enough to allow for a motion-compensated picture signal processing mode. The invention further relates to a television signal receiver including such a picture signal processing mode controlling apparatus.
Many recent proposals for novel High-Definition TeleVision (HDTV) systems include the requirement that a control signal is to be transmitted along with the HDTV signal which gives an indication about the origin of the picture signal, because in some respects, picture signals originating from movie-film require a different treatment, i.e. picture signal processing mode, than picture signals which are picked up by a video camera from a live scene and transmitted directly or recorded on tape or disc and subsequently transmitted as the picture signal, herein termed "non-movie-film picture signals". For similar reasons, up-conversion algorithms to be used in Improved Definition TeleVision (IDTV) receivers require a picture signal processing mode control signal which provides information about the origin of the picture signal. Up till now, no reliable and yet simple method of automatically detecting whether the picture signal originates from movie-film has been reported. Another problem met in IDTV receivers is that motion-compensated picture signal processing methods are potentially very suitable to provide an improved display quality of the picture signal, but that artifacts caused by motion vector estimation errors are very disturbing. Consequently, there is a need to determine when motion vectors are reliable enough to allow for a motion-compensated picture signal processing mode, and when the motion-compensated picture signal processing mode should be switched off in view of the unreliability of the motion vectors.

Method and apparatus for discriminating between movie film and non-movie film and generating a picture signal processing mode control signal


The present invention relates to an energy allocation system for operating at least an energy storage device to substantially balance the energy consumed by the energy storage device with the energy supplied thereto, comprising the steps of: determining a power flexibility of the energy storage device by generating an upper time-varying power function; predicting energy consumption data per discrete time-slots over a given time-window for the device; predicting a demand for energy by the device in a given planning time-period; generating a time-varying upper energy function for the demand prediction that defines an uppermost limit for the supply of energy to the device; generating a time-varying lower energy function for the demand prediction that defines a lowermost limit for the supply of energy to the device, and supplying energy to the device in a range defined by the limits specified by the upper energy function and the lower energy function.

It is globally acknowledged that the depletion of natural energy resources, environmental issues arising from the use thereof and the lack of alternative energy resources are but some of the issues that impact the profile of the energy landscape of the future. To date, natural energy resources continue to be used for the generation of different energy forms. For example, the thermal energy generated from fossil fuels such as oil, gas and coal is converted to other energy forms such as electrical, motion and so on. However, such natural energy resources, and fossil fuels in particular, are becoming scarce, cannot be replaced and/or detrimentally impact the environment. Nuclear energy has been used as an alternative energy form to the aforementioned energy resources. In particular, nuclear fission has been used for the generation of heat and electricity. However, there are short-term risks such as incidences associated with nuclear fission as well as long term issues such as storage and/or disposal of radioactive waste resulting from nuclear fission.
In order to address the above-described issues and/or to provide alternative energy resources, investment, development and research into renewable energy resources such as, for example, solar and wind power, is being done. An advantage associated with renewable energy resources, and from the viewpoint of sustainability, is that they may be considered to be abundant given that, thus far, there is no known limit on the life expectancy of the sun. However, there are some issues associated with renewable energy resources, which restrict them from providing a suitable alternative to and/or completely replacing fossil fuels for the generation of energy. One such issue is that renewable energy resources are time-variant in their occurrence—the wind does not always blow and the solar irradiance depends on the time of the day and on cloud movement. A further issue is that renewable energy resources may be area-specific in that they may occur more abundantly in some areas compared to others, such as, for example, coastal regions and deserts, which may be far away from the demand of such resources, thereby necessitating the consideration of transport issues to the location(s) of the demand.
With respect to the consumption aspect of the energy chain, demand for energy may also be variable and random, albeit with differences from the variability and randomness with which energy is generated using renewable energy resources. To facilitate the alignment of energy demand/consumption with energy supply/generation, particularly where renewable energy resources are used for the energy supply/generation, energy storage devices may be used and/or considered. However, for certain energy forms, such as, for example, electrical energy, it may be a challenge to provide energy storage devices with sufficient capacity, if at all. In this regard, although pump storage plants may provide a solution, they are usually implemented in certain terrains such as mountainous regions and require access to water. Other methods such as, for example, hydrogene extraction and compressed air have associated technical limitations and so are not widely used. As for electrical accumulator technology, it is costly and may be considered to have inadequate storage density, thus space and other resources may have to be facilitated for its implementation in a realistic energy chain scenario.
Some proposals have been made to facilitate alignment between power generation and power consumption/demand. Reference is made to the document titled, "Pacific Northwest Gridwise testbed demonstration projects: Part i. Olympic peninsula project", published in the Technical Report PNNL-17167, Pacific Northwest National Laboratory, October 2007 by D. J. Hammerstrom et. al and also to the document titled, "Pacific Northwest Gridwise testbed demonstration projects: Part ii. Grid-friendly appliance project", published in the Technical Report PNNL-17079, Pacific Northwest National Laboratory, October 2007 by D. J. Hammerstrom et. al. These documents publish the investigation conducted in the Pacific Northwest Gridwise project where price incentives were coupled to the generated power and individual electrical appliances could react—momentarily—to power shortages, where a power shortage was observed by a reduced grid frequency, this scenario highlighting how the grid frequency may serve as a universal indicator of the power present in a power grid. The Pacific Northwest Gridwise project is concerned with the alignment of power consumption with power generation rather than aligning energy consumption with energy generation, that is, only current/power decisions are addressed rather than the attainment of energy goals by the provision of power over a given time-period.
Reference is now made to the Danish EDISON project as documented in, "Electrical Vehicle Fleet Integration in the Danish EDISON project—A virtual power plant on the island of Bornholm", published in Proc. IEEE Power & Energy Society General Meeting 2010, Minneapolis, Minn., USA, Jul. 25-29, 2010, also available at: URL:domino.research.ibm.com/library/cyberdig.nsf/papers/9C976F3545EA6E EE852576AF003208EE/$File/rz3761.pdf, by C. Binding et. al, and "Introducing Electrical Vehicles into the current electricity markets", EDISON Deliverable D2.3, Version 3, C. Hay, M. Togeby, N.C. Bang (Ea Energy Analyses), C. Sondergren (Danish Energy Association), L. H. Hansen (Dong Energy), May 25, 2010, URL:www.edison-net.dk/{tilde over ( )}/media/EDISON/Reports/Edison Deliverable2.3Version3.0.ashx. Like the Pacific Northwest Gridwise project, the Danish EDISON project, is also based on price signals that are coupled to power generation and works only in the power dimension rather than in the energy dimension.
Another proposal to facilitate addressing the misbalance between power generation and power consumption can be found in the document titled, "Powermatcher: multiagent control in the electricity infrastructure", published in the Proceedings of the fourth international joint conference on Autonomous agents and multiagent systems, pages 75-82, ACM 2005 by J. K. Kok, C. J. Warmer and I. G. Kamphuis. In the PowerMatcher system, the demand aspects in the power chain hierarchically express their power demand and pass their bids to the generation entities, that is, power generation sources. If mismatching between bids and offers are detected, an auctioning approach to find a feasible bid/offer relation is taken. The PowerMatcher system is organised hierarchically and so it may be scaled, but it has increased real-time communication requirements in order to support an auction-style balancing between power supply/generation and power demand/consumption. Like the Pacific Northwest Gridwise project and the EDISON project, the Powermatcher system operates in the power dimension rather than the energy dimension, i.e. there is no guarantee that sufficient amounts of power are delivered to a demand unit over a given time-period and, thus, in the event that a price quoted in a bid/offer in respect of a given demand unit is considered to be relatively high, no power will be fed into that demand unit and so it will not accumulate energy. In this case, and for example, where the demand unit is embodied by an electrical appliance such as the battery of an electrical vehicle, it will remain uncharged and, if it is a hot-water boiler, then it will not be heated.
Reference is now made to the document titled, "Hierarchical model predictive control for resource distribution", published in Proceedings of the 49th IEEE conference on decision and control, Atlanta Ga., USA, December 2010, IEEE, by Bendtsen et. al wherein a hierarchical concept using aggregation towards a high-level controller is proposed. Like the above-described documents, this disclosure is concerned with the alignment of power generation with power consumption rather than working in the energy dimension to fulfil an energy goal. Whilst energy constraints have been expressed in terms of the maximum and minimum total energy that can be stored in a device, these terms are static and do not reflect the time-varying need of stored energy as related to energy consumption and inflowing power/energy.

Energy allocation system for balancing energy consumption

International Business Machines Corporation


A triple latch flip flop system and method are disclosed. In one embodiment, triple latch flip-flop system includes a pull up latch, a pull down latch, a primary latch and an output. The pull up latch drives a pull up node. The pull down latch driving a pull down node. The primary latch records state of the triple latch flip-flop system. The output for outputting a logic value based upon outputs of the pull up latch, pull down latch and the primary latch.

Electronic systems and circuits have made a significant contribution towards the advancement of modern society and are utilized in a number of applications to achieve advantageous results. Numerous electronic technologies such as digital computers, calculators, audio devices, video equipment, and telephone systems facilitate increased productivity and cost reductions in analyzing and communicating data, ideas and trends in most areas of business, science, education and entertainment. A number of components such as latches often utilized to facilitate realization of many of these advantageous results. Latches are typically used to facilitate orderly data flow in electronic circuits. However, using traditional flip flop latches often involve tradeoffs that can amount to significant impacts given the prolific use of numerous latches in many applications.
While traditional flip flop latches may provide flow coordination, there are a number of issues that often arise in conventional flip flop latch systems. For example, traditional flip flop latches often involve timing penalties that tend to become even more burdensome as the operating frequencies of various systems increase. Traditional flip flop latches also often involve racing issues, Vmin limitations issues, and power consumption issues. For example, glitching input data can result in unnecessary active power consumption during clock "low" transitions.

Triple latch flip flop system and method


This invention relates to a method for drying the charge of a unit that treats petroleum cuts with a low water charge that consists in injecting a hydrolysable chemical compound into said charge.

This invention relates to the drying of petroleum cuts with a low water charge that are to be treated in units whose operation is sensitive to the presence of water in their charges.
A method for reducing the quantity of water in the charge of an isomerisation unit for paraffin base hydrocarbons with a water content that ranges between 0.5 and 5 ppm, is described in the British document GB 1 426 401 A dated Feb. 25, 1976.
According to this method, to reduce the water content to below 0.5 ppm, the paraffin base hydrocarbon charge is put in contact with a solid drying chemical agent whose active surface ranges between 1 and 500 m2/g.
The dried charge is then isomerized at a temperature ranging between 50 and 350xc2x0 C., in the presence of hydrogen, by passing over a catalyst.
According to one of the methods of execution of this method, the drying chemical agent is a support that is chemically inert to water, on the surface of which are deposited chemical compounds that easily combine with water. The chemical compounds can he either alkaline metals, such as potassium or sodium, or easily hydrolysable metallic chlorides, such as aluminum chloride.
This method has the disadvantage of needing costly and voluminous equipment that is hard to install on existing units in order to be implemented.
Furthermore, when the solid chemical agent has reacted with the water from the hydrocarbon charge, it cannot be regenerated and must be replaced.
Another method for drying a hydrocarbonic charge consists in passing said charge in dryers through a bed of adsorbent product that holds the water back through molecular interaction.
The adsorbent product is usually alumina or a molecular sieve. It progressively saturates with water and must be periodically regenerated.
Generally, two dryers are arranged parallel to each other where one is in regeneration mode while the other is carrying out the drying.
When the hydrocarbonic charge is passing through the dryer, the water is contains is adsorbed over a transfer area, that moves from the entry point to the exit point of the dryer as the adsorbent becomes saturated.
The width of this transfer area depends on the operating conditions, the periodicity of the regeneration of the adsorbent and of its aging.
At the beginning of the adsorption cycle, the transfer area is close to the entry point of the dryer and the water content of the charge when it exits is very low. At the end of the adsorption phase, the transfer area is close the to the exit point of the dryer and it could happen that the charge then only encounters adsorbent saturated with water.
This phenomenon results in a very rapid increase of the charge""s water content at the dryer""s exit point.
As the detection limit of the devices that measure the charge""s water content is in the 0.1 ppm by weight range, when such a content is detected, the operation of the hydrocarbonic charge treatment unit has already experienced harmful effects, such as a significant deactivation of the catalyst in the case of an isomerisation unit.
The object of this invention is precisely to correct said disadvantages and provide an economic, efficient and safe method for drying a hydrocarbonic charge.
With this end in view, it proposes a method for drying a charge from a unit that treats petroleum cuts with a low water charge, characterized in that this charge is injected with a quantity of a chemical compound chosen from the group consisting of:
a metal halide replaced by hydrocarbonic radicals with a formula of M1XyR1nR2m where M1 is a metal chosen from the group consisting of aluminum, gallium and indium, X is a halogen, R1 and R2 are hydrocarbonic radicals, the value or y is 1, 2 or 3, and the values of m and n are either 0 or 1, the sum of n and m is not equal to zero and the sum of y, n and m is equal to 3,
a metal halide replaced by hydrocarbonic radicals with a formula of M2XzR1jR2kR3l where M2 is a metal chosen from the group consisting of titanium, tin, germanium and zirconium, X is a halogen, R1, R2 and R3 are hydrocarbonic radicals, the value of z is 1 or 2 and the values of j, k and l are either 0 or 1, the sum of j, k and l is not equal to zero, and the sum of z, j, k and 1 is equal to 4,
a metal compound replaced by hydrocarbonic radicals with a formula of M3R1R2R3R4 where M3 is a metal chosen from the group consisting of titanium, tin, germanium and zirconium, and R1, R2 and R3 are hydrocarbonic radicals,
a metal compound replaced by hydrocarbanic radicals with a formula of M4R1R2R3 where M4 is a metal chosen from the group consisting of aluminum, gallium and indium, R1, R2 and R3 arc hydrocarbonic radicals
where the quantity of the chemical compound injected is at least equal to the quantity necessary for all the water contained in said charge to react by hydrolysis with said chemical compound.
The hydrocarbonic radicals R1, R2, R3 and R4 are preferably chosen from the alkyl or aryl groups.
When the water content of the charge, expressed by weight, is less that 1 ppm, the quantity of chemical compound injected is advantageously less than 1% by weight of said charge.
Preferably, the quantity of chemical compound injected is less than 100 ppm by weight and, even more preferably, less than 1 ppm by weight of said charge.
In a preferred mode of execution, the method of the invention is implemented by previously diluting the quantity of chemical compound injected in at least a hydrocarbon.
The hydrocarbon for the dilution can namely be chosen from the paraffin base hydrocarbons that contain 5 or 6 carbon atoms.
Alternatively, the hydrocarbon for the dilution can be chosen from the naphthenic hydrocarbons that contain 5 or 6 carbon atoms.
When the unit that treats the petroleum cut is an isomerisation unit that consists of a section that dries the charge and a reaction section, linked by a connecting pipe, the chemical compound can be injected into said connection.
Lastly, in this form of implementation, the connecting pipe can advantageously be provided with a mixing device arranged downstream from the point of injection of the chemical compound.
Therefore, the device in the invention provides an economical and efficient means for drying hydrocarbon charges at the entry point of treatment units that are sensitive to the presence of water.
On the one hand, it does not require that the refineries make any significant additional investments. On the other hand, the chemical compounds injected into the hydrocarbon charge according to the method as set forth in the invention hold hydrocarbon radicals that allow them to better solubilize in the charge and therefore make it easier to improve the sought dehydration.

Method for drying the charge from a unit that treats petroleum cuts with a low water charge

Abstract: The quantity of the chemical compound injected is at least equal to the quantity necessary for all the water contained in the charge to react by hydrolysis with said chemical compound.

Abstract: The invention finds its application in units that treat petroleum cuts and whose operation is sensitive to the presence of water in their charges, in particular the paraffin base hydrocarbon isomerisation units. One drawing.


A receiver that receives radio signals, and a method for the same. The radio signals may be received by a plurality of antennas and then demodulated by respective converter devices, an estimated channel device estimates a channel for at least one antenna and at least one beam-forming device performs beam-forming on a selected main path signal from among the demodulated incident data signals. The output signals from the at least one beam-forming device are combined. The method of receiving the incident data signals may be accomplished by using space diversity.

1. Field of the Invention
The present invention relates to a radio receiver and more particularly, to a method and an apparatus for receiving digital TV signals using space diversity and at least one beam-former device.
2. Description of the Related Art
Conventional digital TV signals are subject to multi-path signaling occurring, often due to buildings, walls, and clouds. When receiving digital TV signals, the multi-path effect may result in echoes of the same received digital TV signals. In a digital TV receiver, such echoes are manifested as signal noise. These echoes resulting from the multi-path effect, have a strong influence on the quality of the received digital TV signals. The Advanced Television System Committee (ATSC) standard A53 is a standard for conventional digital TV receivers.

Method and apparatus for receiving digital television signals using space diversity and beam-forming