Showing papers on "Detector published in 1992"

A CFAR adaptive matched filter detector

Abstract: An adaptive algorithm for radar target detection using an antenna array is proposed. The detector is derived in a manner similar to that of the generalized likelihood-ratio test (GLRT) but contains a simplified test statistic that is a limiting case of the GLRT detector. This simplified detector is analyzed for performance to signals on boresight, as well as when the signal direction is misaligned with the look direction. >

Optical position determination

Abstract: This invention relates to a coordinate sensor for detecting the position of a moveable detector relative to a data space coded with coordinate information by detecting and processing the coordinate information. It may be used for obtaining both two and three dimensional position related information, such as might be used for determining the position of a pen/pencil on paper for handwriting data input. It also may be used for detecting angular, rotational, and linear motion. The coordinate sensor provides an apparatus for precisely locating the position of a movable element within a space. More particularly, it provides an input/output apparatus for use with a computer that includes a movable element, whose exact position within a space can be determined without any physical connection between the movable element and the space. It comprises a data space formatted with a code for designating the coordinates of a point in the data space, a detector for detecting the code, a processor for processing data from the detector to determine the position of the point in the data space, and a data output method for human interface to the coordinate sensor.

Optical scanning head

Abstract: The optical scanning head includes at least one trio of light emitting diodes arranged so the LEDs emit light at different angles to create a fan of light. An optical module includes a light shield or "dark room" and a lens/filter assembly which provides control of the depth of focus of the scanner. The optical module is located behind the light source, and the detector, made up of a CCD array is mounted behind the optic module for detecting the light intensity in the reflected beam over a field of view across a bar code symbol. The CCD array generates an electrical signal indicative of the detected light intensity. A DC source or battery provides DC voltage to the LEDs and CCDs in response to a clocked signal which provides a gradual or sequential illumination of the LEDs and coordinates the activation of the CCDs in order to minimize power consumption during scans.

Water-equivalent plastic scintillation detectors for high-energy beam dosimetry: I. Physical characteristics and theoretical considerations

Abstract: A minimally perturbing plastic scintillation detector has been developed for the dosimetry of high-energy beams in radiotherapy. The detector system consists of two identical parallel sets of radiation-resistant optical fibre bundles, each connected to independent photomultiplier tubes (PMTs). One fibre bundle is connected to a miniature water equivalent plastic scintillator and so scintillation as well as Cerenkov light generated in the fibres is detected at its PMT. The other 'background' bundle is not connected to the scintillator and so only Cerenkov light is detected by its PMT. The background signal is subtracted to yield only the signal from the scintillator. The water-equivalence of plastic scintillation detectors is studied for photon and electron beams in the radiotherapy range. Application of Burlin cavity theory shows that the energy dependence of such detectors is expected to be better than the commonly used systems (ionization chambers, LiF thermoluminescent dosimeters, film and Si diodes). It is also shown that they are not affected by temperature variations and exhibit much less radiation damage than either photon or electron diode detectors.

Detection, measurement, and gravitational radiation

Abstract: The optimum design, construction, and use of the Laser Interferometer Gravitational Wave Observatory (LIGO), the French-Italian Gravitational Wave Observatory (VIRGO), or the Laser Gravitational Wave Observatory (LAGOS) gravitational radiation detectors depends upon accurate calculations of their sensitivity to different sources of radiation. Here I examine how to determine the sensitivity of these instruments to sources of gravitational radiation by considering the process by which data are analyzed in a noisy detector. The problem of detection (is a signal present in the output of the detector?) is separated from that of measurement (what are the parameters that characterize the signal in the detector output?). By constructing the probability that the detector output is consistent with the presence of a signal, I show how to quantify the uncertainty that the output contains a signal and is not simply noise. Proceeding further, I construct the probability distribution that the parametrization $\ensuremath{\mu}$ that characterizes the signal has a certain value. From the distribution and its mode I determine volumes $V(P)$ in parameter space such that $\ensuremath{\mu}\ensuremath{\in}V(P)$ with probability $P$ [owing to the random nature of the detector noise, the volumes $V(P)$ are always different, even for identical signals in the detector output], thus quantifying the uncertainty in the estimation of the signal parametrization. These techniques are suitable for analyzing the output of a noisy detector. If we are designing a detector, or determining the suitability of an existing detector for observing a new source, then we do not have detector output to analyze but are interested in the "most likely" response of the detector to a signal. I exploit the techniques just described to determine the "most likely" volumes $V(P)$ for detector output that would result in a parameter probability distribution with given mode. Finally, as an example, I apply these techniques to determine the anticipated sensitivity of the LIGO and LAGOS detectors to the gravitational radiation from a perturbed Kerr black hole.

Signal interception: performance advantages of cyclic-feature detectors

Abstract: The problem of detecting the presence of spread-spectrum phase-shift-keyed signals in variable noise and interference backgrounds is considered, and the performances of four detectors are evaluated and compared. The detectors include the optimum radiometer, the optimum modified radiometer that jointly estimates the noise level and detects the signal, and the maximum-SNR spectral-line regenerator for spectral-line frequencies equal to the chip rate and the doubled carrier frequency. It is concluded that the spectral-line regenerators can outperform both types of radiometers by a wide margin. The performance advantages are quantified in terms of receiver operating characteristics for several noise and interference environments and receiver collection times. >

Application of the wavelet transform for pitch detection of speech signals

Abstract: An event-detection pitch detector based on the dyadic wavelet transform is described. The proposed pitch detector is suitable for both low-pitched and high-pitched speakers and is robust to noise. Examples are provided that demonstrate the superior performance of the pitch detector in comparison with classical pitch detectors that use the autocorrelation and the cepstrum methods to estimate the pitch period. >

Image control apparatus

Abstract: An image control apparatus which is essentially composed of a movement detector, a judging device, and a controller wherein the movement detector detects the movement of the operator and generates a movement signal corresponding to the detected movement of the operator. The judgement device determines the state of the operator on the basis of the movement signal provided by the movement detector. The controller controls the image in accordance with the movement signal and the judgement of the judgement device. The movement detector, judging device and the controller cooperate so as to control the image in accordance with the movement of the operator.

The CLEO-II detector

Abstract: The new detector for data recording by the CLEO collaboration at the Cornell Electron Storage Ring is described. This detector has been designed to optimize studying e+ e− annihilation into hadronic matter at a total energy of 10 GeV. It consists of high precesion charged particle tracking chambers and an electromagnetic calorimeter together with systems for particle identification. The design of the detector and its performance over the first year and a half of operation are presented.

Obstacle-detecting apparatus

Abstract: This device can detect an obstacle in a railroad crossing or similar setting by way of image processing independently of a height and a width of an obstacle. The image data read from a video, camera 11 into a multi-valued image memory 13 is compared with background data stored in a background-data creating unit 15 in a data comparator 16. Based on the compared result, a still-object detector 17 detects if an obstacle exists. If it is detected that an obstacle exists and a rod of a crossing gate is down in a gate state detector 18, an alarm output unit 19 serves to output an alarm signal.

Optical signal free-space conversion board

Abstract: This is a board to transport and convert optical outgoing free-space signals from a spatial light modulator which comprises: at least one detector to process the outgoing free-space signal; at least one signal transmitter to process the outgoing free-space signal; and at least one outgoing optical signal carrier to carry a converted outgoing signal. Other methods and devices are disclosed.

Voice activity detection using a periodicity measure

Abstract: The paper describes a voice activity detector (VAD) that can operate reliably in SNRs down to 0 dB and detect most speech at −5 dB. The detector applies a least-squares periodicity estimator to the input signal, and triggers when a significant amount of periodicity is found. It does not aim to find the exact talkspurt boundaries and, consequently, is most suited to speech-logging applications where it is easy to include a small margin to allow for any missed speech. The paper discusses the problem of false triggering on nonspeech periodic signals and shows how robustness to these signals can be achieved with suitable preprocessing and postprocessing.

Automated photomask inspection apparatus

Abstract: An automated photomask inspection apparatus including an XY state (12) for transporting a substrate (14) under test in a serpentine path in an XY plane, an optical system (16) comprising a laser (30), a transmission light detector (34), a reflected light detector (36), optical elements defining reference beam paths and illuminating beam paths between the laser, the substrate and the detectors and an acousto-optical beam scanner (40, 42) for reciprocatingly scanning the illuminating and reference beams relative to the substrate surface, and an electronic control, analysis and display system for controlling the operation of the stage and optical system and for interpreting and storing the signals output by the detectors. The apparatus can operate in a die-to-die comparison mode or a die-to-database mode.

Compton scattering tomography

Abstract: Apparatus and methods for Compton scattering tomography employ a source of monoenergetic gamma rays and a detector capable of detecting the energy of scattered photons and determining the detector location both disposed on one side of an object to be imaged. Based on analysis of the measurement of the energy of the detected photons and the detector locations, a circle of possible scattering locations is determined as to each scattering event. By performance of a number of experiments as a function of detector location and energy, the density of the object can be reconstructed by filtering and back-projecting the data to yield an image responsive to variation in the density of the material of the object to be imaged.

A Si bipolar phase and frequency detector IC for clock extraction up to 8 Gb/s

Abstract: A phase and frequency detector IC is presented that operates up to an NRZ bit rate of 8 Gb/s. The IC comprises a phase detector (PD), a quadrature phase detector (QPD), and frequency detector (FD). In the PD and QPD the VCO signal and the quadrature VCO signal are sampled by the NRZ input signal. The two beat notes provided by this operation are subsequently processed in the FD. The superposition of the FD output and the PD output signals are then fed into a passive loop filter (lag/lead filter). The loop filter and the VCO are external components. The measured pull-in range is >+or-100 MHz at 8 Gb/s. The measured r.m.s. time jitter of the extracted clock is less than 1.9 ps for a pseudorandom bit sequence (PRBS) length of 2/sup 23/-1. A 0.9- mu m 12-GHz f/sub T/ silicon bipolar process was used to fabricate the chip with a total power consumption of 1.4 W. >

R.F. transparent RF/UV-IR detector apparatus

Abstract: A dual-mode, radio frequency, optical-wavelength detector apparatus includes RF-transparent optical elements adapted to focusing optical energy in a wavelength range including ultraviolet through infrared wavelengths, on an optical detector, and an RF antenna located behind the optical elements. One embodiment of the apparatus employs a Cassegrain infrared optical telescope system having a concave primary mirror, the front surface of which has applied thereto multiple layers of dielectric material comprising an interference filter reflective in a band of infrared wavelengths, and transmissive to radio frequency energy. A convex secondary mirror having a similar reflective coating is so located as to reflect infrared energy backwards through a central coaxial perforation through the primary mirror onto an infrared detector. The apparatus includes a planar RF antenna rearward of the primary mirror, which antenna utilizes the full aperture of the infrared optical system for the reception and transmission of RF energy.

Model for the computation of self-motion in biological systems.

Abstract: I present a method by which direction- and speed-tuned cells, such as those commonly found in the middle temporal area of the primate brain, can be used to analyze the patterns of retinal image motion that are generated during observer movement through the environment. For pure translation, the retinal image motion is radial in nature and expands out from a point that corresponds to the direction of heading. This heading direction can be found by the use of translation detectors that act as templates for the radial image motion. Each translation detector sums the outputs of direction- and speed-tuned motion sensors arranged such that their preferred direction of motion lies along the radial direction out from the detector center. The most active detector signifies the heading direction. Rotation detectors can be constructed in a similar fashion to detect areas of uniform image speed and direction in the motion field produced by observer rotation. A model consisting of both detector types can determine the heading direction independently of any rotational motion of the observer. The model can achieve this from the outputs of the two-dimensional motion sensors directly and does not assume the existence of accurate estimates of image speed and direction. It is robust to the aperture problem and is biologically realistic. The basic elements of the model have been shown to exist in the primate visual cortex.

A computational model of the analysis of some first-order and second-order motion patterns by simple and complex cells

Abstract: Although spatio-temporal gradient schemes are widely used in the computation of image motion, algorithms are ill conditioned for particular classes of input. This paper addresses this problem. Motion is computed as the space-time direction in which the difference in image illuminance from the local mean is conserved. This method can reliably detect motion in first-order and some second-order motion stimuli. Components of the model can be identified with directionally asymmetric and directionally selective simple cells. A stage in which we compute spatial and temporal derivatives of the difference between image illuminance and the local mean illuminance using a truncated Taylor series gives rise to a phase-invariant output reminiscent of the response of complex cells.

High resolution gamma ray spectroscopy with CdTe detector systems

Abstract: Energy resolution and photopeak efficiency of the nowadays CdTe detector material can be improved using several detector shapes or electronic signal processing. Current results obtained in our laboratory with different detector geometries and pulse discrimination methods are presented and compared. Finally, we report on a new charge loss compensation method which improves both energy resolution and photopeak efficiency.

Error performance of multiple-symbol differential detection of PSK signals transmitted over correlated Rayleigh fading channels

Abstract: The error performance of multiple-symbol differential detection of uncoded QPSK signals transmitted over correlated Rayleigh fading channels is studied. The optimal detector is presented, along with an exact expression for the corresponding pairwise error event probability. It is shown that multiple-symbol differential detection is a very effective strategy for eliminating the irreducible error floor associated with a conventional differential detector. In all of the cases investigated, a detector with an observation interval as small as two symbols is sufficient for this purpose. It is also found that the error performance of a multiple-symbol differential detector is not sensitive to the mismatch between the decoding metric and the channel fading statistics. >

A large area detector for high-energy neutrons

Abstract: We present design studies, results of test measurements, and Monte Carlo simulations which served as a basis for the realization of a large area neutron detector (LAND). It has a front area of 2m×2m and a depth of 1 m, and features a multilayer structure of passive converter and active scintillator material. The detector is subdivided in independently operating paddles which allow time-of-flight and position measurement. An energy resolution of ΔT n / T n =5.3% for a flight path of 15 m and an overall detection efficiency of ϵ ≈ 1 is anticipated for neutrons with T n ≈ 1 GeV. The operation of LAND at the SIS facility of GSI is described.

Grating‐coupled quantum‐well infrared detectors: Theory and performance

Abstract: A theory of the grating‐coupled quantum‐well infrared detector, based on the modal expansion method (MEM) is presented together with numerical simulation results. MEM is a near‐exact way of determining the electromagnetic‐field pattern in a reflection grating‐coupled quantum‐well infrared detector, and is suitable for the calculation of absorption quantum efficiencies. Both lamellar gratings and crossed (doubly periodic) gratings are dealt with. Numerical simulations show that quantum efficiencies integrated with respect to wavelength ηint equal to 1 μm may be obtained in a detector equipped with a crossed grating of square symmetry, and a waveguide. The waveguide is defined by the metal grating on one side of the infrared absorbing quantum wells, and a thick aluminum arsenide layer on the other. This implies a factor of 4 higher ηint than in a 45° polished edge detector with the corresponding quantum‐well characteristics. Finally, a sensitivity analysis shows that a change in grating dimensions of the order of 0.1 μm results in relative changes of ηint of about 1%.

A bat-like sonar system for obstacle localization

Abstract: An active wide-beam sonar system that mimics the sensor configuration of echolocating bats is described for applications in sensor-based robotics. Obstacles in a two-dimensional (2-D) environment are detected and localized using time-of-flight (TOF) measurements of their echoes. The standard threshold detector produces a biased TOF estimate. An unbiased TOF estimate is derived by a parametric fit to the echo waveform, motivated by experimental observations of actual sonar signals. This novel method forms a tradeoff between the complexity of the optimum estimator and the biased threshold detector. Using the TOF information from both methods, the range and azimuth of an obstacle are estimated. Localization is most accurate if the obstacle is located along the system line-of-sight and improves with decreasing range. Standard deviations of the range and azimuth estimators are compared to the Cramer-Rao lower bounds. The parabolic fit method has large variance but zero bias at large deviations from the line-of-sight. The system operation is generalized from isolated obstacles to extended obstacles. >

A High-Speed Data-Collection System for Large-Unit-Cell Crystals using an Imaging Plate as a Detector

Abstract: A high-speed data-collection system for large-unit-cell crystals is presented, using the Fuji Imaging Plate as an X-ray detector and a rotating-anode generator as the X-ray source. It is an automatic data-acquisition system that requires almost no manual intervention. The quality of data collected on the system is discussed. Merging R values ranged from 0.04 to 0.05. Compared with a four-circle diffractometer, data reproducibility was better, isomorphous/anomalous Patterson maps were almost identical in quality and data from a small-molecule crystal, cytidine, were of almost the same quality. Protein structures were refinable using the data measured on the system, the final crystallographic R value of the 2.2 A 3-isopropylmalatedehydrogenase structure being 0.185 and that of the 1.88 A Flammulina veltipes agglutinin structure being 0.199.

Jammed shuffle detector

Abstract: The present invention provides a floating jammed shuffle detector for use in a card shuffling machine. The detector has a body with a card contacting portion and a sensor interactive portion. A detector housing and a photosensor are provided. The sensor interactive portion has an aperture of a predetermined size. The detector, particularly the body, is reciprocally mounted in the housing, whereby the card contacting portion of the detector contacts the uppermost card of a deck of cards and the sensor interactive portion is received in the photosensor. Depending on the sensed position of the card contacting portion of the detector, the machine receives a reshuffle or proceed command.

Digital pulse processing in high resolution, high throughput, gamma-ray spectroscopy

Abstract: A new method for processing signals produced by high resolution, large volume semiconductor detectors is described. These detectors, to be used in the next generation of spectrometer arrays for nuclear research (i.e., EUROBALL, etc.), present a set of problems, such as resolution degradation due to charge trapping and ballistic deficit effects, poor resolution at a high count rate, long term and temperature instability, etc. To solve these problems, a new approach based on digital moving window deconvolution (MWD) is developed. >

The use of the wavelet transform in the detection of an unknown transient signal

Abstract: For the detection of a not-perfectly-known signal in noise, usually no uniformly most powerful test exists, and thus a detector performance depends on the signal representation. The use of the wavelet representation of signals to perform a new detection scheme is discussed. The advantage of using this particular representation is shown. It is shown that prior information regarding the relative bandwidth and the time-bandwidth-product of the signal to be detected is efficiently incorporated into the detection problem formulation. Thus, the proposed detection scheme is most suitable for detection of unknown transient signals when prior information about the signal time-bandwidth product and relative bandwidth exists. In these cases, the wavelet-representation-based detector performs better than any other. The structure of the proposed detectors is discussed and its performance is evaluated using Monte Carlo simulations. >

A novel charge sensitive preamplifier without the feedback resistor

Abstract: A novel charge sensitive preamplifier which has no resistor in parallel with the feedback capacitor is presented. No external device or circuit is required to discharge the feedback capacitor. The detector leakage and signal current flows away through the gate of the first JFET which works with its gate to source junction slightly forward biased. The DC stabilization of the preamplifier is accomplished by an additional feedback loop, which permits to equalize the current flowing through the forward baised gate to source junction and the current coming from the detector. An equivalent noise charge of less than 20 electrons r.m.s. has been measured at room temperature by using an input JFET with a transconductance to gate capacitance ratio of 4 mS/5.4 pF.

The Galileo Solid-State Imaging Experiment

Abstract: The Solid State Imaging (SSI) experiment on the Galileo Orbiter spacecraft utilizes a high-resolution (1500 mm focal length) television camera with an 800 × 800 pixel virtual-phase, charge-coupled detector It is designed to return images of Jupiter and its satellites that are characterized by a combination of sensitivity levels, spatial resolution, geometric fiedelity, and spectral range unmatched by imaging data obtained previously The spectral range extends from approximately 375 to 1100 nm and only in the near ultra-violet region (~350nm) is the spectral coverage reduced from previous missions The camera is approximately 100 times more sensitive than those used in the Voyager mission, and, because of the nature of the satellite encounters, will produce images with approximately 100 times the ground resolution (ie, ~50mlp−1) on the Galilean satellites We describe aspects of the detector including its sensitivity to energetic particle radiation and how the requirements for a large full-well capacity and long-term stability in operating voltages led to the choice of the virtual phase chip The F/85 camera system can reach point sources of F(mag) ~ 11 with S/N ~ 10 and extended sources with surface brightness as low as 20 kR in its highest gain state and longest exposure mode We describe the performance of the system as determined by ground calibration and the improvements that have been made to the telescope (same basic catadioptric design that was used in Mariner 10 and the Voyager high-resolution cameras) to reduce the scattered light reaching the detector The images are linearly digitized 8-bits deep and, after flat-fielding, are cosmetically clean Information ‘preserving’ and ‘non-preserving’ on-board data compression capabilities are outlined A special “summation” mode, designed for use deep in the Jovian radiation belts, near Io, is also described The detector is ‘preflashed’ before each exposure to ensure the photometric linearity The dynamic range is spread over 3 gain states and an exposure range from 417 ms to 512 s A low-level of radial, third-order, geometric distortion has been measured in the raw images that is entirely due to the optical design The distortion is of the pincushion type and amounts to about 12 pixels in the corners of the images It is expected to be very stable

Processes for lift-off of thin film materials and for the fabrication of three dimensional integrated circuits

Abstract: Various novel processes permit integrating thin film semiconductor materials and devices using lift off, alignment, and deposition onto a host substrate. As a result, three dimensional integrated circuits can be constructed. Three dimensional communication in an integrated circuit can be implemented via electromagnetic communication between emitters and detectors fabricated via the novel processes. Integrated circuit layers are transparent to the electromagnetic signals propagated from the emitter and received by the detector. Furthermore, arrays of optical detectors can be implemented to perform image processing with tremendous speed. Processing circuitry can be situated directly below the optical detectors to process in massive parallel signals from individual optical detectors.