Showing papers on "Detector published in 1987"

Integrated cargo security system

Abstract: An integrated cargo transportation security system is provided for a fleet of enclosed cargo transportation containers. Each container includes a subsystem including a door sensor for sensing access door opening and closure, a module unit including a connecting frame for a removable module and cabling leading to the door sensor. The identically appearing removable modules are configurable as active and passive. Each locks into the unit. The system includes a central data collection and processing facility for processing cargo trip data collected by at least one active module during a cargo trip of the container into a roadmap indicating travel route of the container during the trip and the time and location of significant event such as unauthorized opening of the cargo door. The module unit having an active module includes a self contained power supply, a location detector for detecting present location of said container, a clock, a central processor for generating a sequence of status numbers indicative of accumulated location, time and door status, and a memory for storing the sequence during the trip. The system further includes means for transferring the status number sequence to the central data collection and processing facility. A radio link may be provided to connect the container module to the central data facility in real time, and may be operated by authorized personnel at the container to signal predetermined conditions to the central facility.

Phase-mismatch dependence of efficiency of wave generation through four-wave mixing in a single-mode optical fiber

Abstract: The generation wave efficiency with respect to phase mismatch in the four-wave mixing process is clarified experimentally in a single-mode fiber transmission line at 825 nm wavelength. The generated power of approximately 20 pW is measured successfully for input signal powers below 1 mW by the technique utilizing a heterodyne receiver and lock-in detector. The calculated efficiency as a function of the equivalent frequency separation can well explain and reflect the results obtained experimentally. Furthermore, the efficiency at zero chromatic dispersion wavelengths of 1.3 and 1.55 μm is also discussed considering chromatic dispersion slope against wavelength.

Crystal orientation and X-ray pattern prediction routines for area-detector diffractometer systems in macromolecular crystallography

Abstract: Routines for crystal orientation and the prediction of expected reflections which are part of the data collection software package MADNES for area-detector diffractometer systems in macromolecular crystallography are described. This package is designed to be area-detector-system independent. In addition to refining crystal cell lengths and angles, crystal orientation, crystal-to-detector distance, position of the primary beam on the detector, and rotation of the detector around the primary beam, the orientation routine also refines the effective mosaic spread of the crystal, the beam inclination angle μand the detector tilt angle τ. A prealignment procedure is described for rapid rough orientation of the crystal. The routines are written in Fortran 77 in a modular way, so that they may be used independently of MADNES and each other.

Gravitational-wave bursts with memory and experimental prospects

Abstract: Experimenters usually divide the gravitational waves which they hope to detect into three classes: 'bursts' in which the wave field hTTij rises from zero, oscillates for only a few cycles and then returns to zero; 'periodic waves', and 'stochastic waves'1. There is, however, a fourth class, 'bursts with memory'2–6 (BWM), in which hTTij rises from zero, oscillates for a few cycles, and then after a burst of duration Δt settles down into a non-zero final value δhTTij. Here we show that for any kind of detector the best way to search for a BWM is to integrate up the signal for an integration time t 1/fopt, where fopt is the frequency at which the detector has optimal amplitude sensitivity to ordinary bursts (bursts without memory). In such a search the sensitivity to BWM with duration Δ <= 1/fopt is independent of the burst duration Δt and is approximately equal to the sensitivity to ordinary bursts one cycle long with frequency fopt (see Fig. 1). It is possible, though not highly probable, that BWM will be among the earliest kinds of gravitational waves detected; therefore experimenters should take them into account when planning their search strategies and data analyses.

New detector concepts

Abstract: On the basis of the semiconductor drift chamber many new detectors are proposed, which enable the determination of energy, energy loss, position and penetration depth of radiation. A novel integrated transistor-detector configuration allows nondestructive repeated readout and amplification of the signal. The concept may be used for the construction of one-or-two-dimensional pixel arrays.

Size of the detector in confocal imaging systems.

Abstract: We consider the role of the detector size in the imaging of confocal systems. We introduce a criterion for detector size to give true confocal operation and show that the lateral resolution is considerably more sensitive to detector size than is the depth-discrimination or optical-sectioning property.

Multiple quantum well 10 μm GaAs/AlxGa1−xAs infrared detector with improved responsivity

Abstract: We have achieved a high responsivity, R=1.9 A/W, 10 μm infrared detector using intersubband absorption in GaAs/AlxGa1−xAs quantum well superlattices. The photocurrent is produced by intersubband absorption followed by efficient photoexcited tunneling. This responsivity is nearly four times higher than our previous results and has been obtained by using thicker and higher AlxGa1−xAs superlattice barriers thereby reducing the dark current and allowing the detector to be operated at higher biases.

General specifications for silicon semiconductors for use in radiation dosimetry.

Abstract: Silicon semiconductor detectors used in radiation dosimetry have different properties, just as e.g. ionisation chambers, affecting the interaction of radiation with matter in the vicinity of the sensitive volume of the detector, e.g. wall materials, and also the collection of the charges liberated in the detector by the radiation. The charge collection depends on impurities, lattice imperfections and other properties of the semiconductor crystal. In this paper the relevant parameters of a silicon semiconductor detector intended for dosimetry are reviewed. The influence of doping material, doping level, various effects of radiation damage, mechanical construction, detector size, statistical noise and connection to the electrometer is discussed.

Reticle inspection system

Abstract: An automatic inspection system including an illuminator for illuminating a reticle or photomask to be inspected, while optically projecting a magnified image of the reticle or photomask onto a plurality of detector elements. A carriage assembly moves the object at a constant velocity to allow the detector elements to sequentially view the entire surface to be inspected. The detector elements are responsive to the intensity of light incident thereupon and are periodically scanned to obtain a two-dimensional measured representation of the object. A database adaptor formulates a two-dimensional representation from the design database description corresponding to the scanned object simultaneously and in synchronism with the scanning of the photomask or reticle. The measured and database adapted representation of the scanned object are input to a signal processor for alignment and defect detection. While the representations are shifted through a memory, an alignment circuit dynamically measures and corrects for misalignment between the representations, so that a defect detector can effectively compare the representations for defects. Additional correction of misalignment between the representations is obtained by modulating the size of the measured representation as detected by the detector elements. At the operator's option, a second measured image of a multi-cell reticle or photomask may be used for comparison as a substitute for the database representation.

Automatic rearview mirror with filtered light sensors

Abstract: The specification discloses an automatic rearview mirror which more accurately responds to the glare-reduction needs of the vehicle operator. The mirror includes a reflective element, a light sensor, and a control circuit for regulating the reflective state of the mirror in response to the light sensor. The light sensor includes a detector responsive to electromagnetic wavelengths and a filter for filtering the wavelengths received by the detector so that the spectral response of the light sensor approximates the spectral response of the human eye or standard C.I.E. observer. The light sensor therefore detects the same wavelength intensities as does the vehicle operator.

High‐resolution duo‐multichannel soft x‐ray spectrometer for tokamak plasma diagnostics

Abstract: A high‐resolution, time‐resolving soft x‐ray multichannel spectrometer (SOXMOS) that permits the simultaneous measurement of emission in two different spectral ranges has been developed and tested extensively for tokamak plasma diagnostics. The basic instrument is a high‐resolution, interferometrically adjusted, extreme grazing incidence Schwob–Fraenkel duochromator. The instrument is equipped with two multichannel detectors that are adjusted interferometrically and scan along the Rowland circle. Each consists of an MgF2 coated, funneled microchannel plate, associated with a phosphor screen image intensifier that is coupled to a 1024‐element photodiode array by a flexible fiber‐optic conduit. The total wavelength coverage of the instrument is 5–340 A with a measured resolution (FWHM) of about 0.2 A when equipped with a 600‐g/mm grating, and 5–85 A with a resolution of about 0.06 A using a 2400‐g/mm grating. The simultaneous spectral coverage of each detector varies from 15 A at the short wavelength limit to 70 A at the long wavelength limit with the lower dispersion grating. The minimum readout time for a full spectral portion is 16 ms, but several individual lines can be measured with 1‐ms time resolution by selected pixel readout. Higher time resolution can be achieved by replacing one multichannel detector with a single channel electron multiplier detector. Examples of data from the PLT and TFTR tokamaks are presented to illustrate the instrument’s versatility, high spectral resolution, and high signal‐to‐noise ratio even in the 10‐A region.

Temperature-sensing system for cattle

Abstract: Disclosed is a device for detecting temperatures which differ from a variable norm of particular use in detecting elevated temperatures in cattle. The device, one being attached to each animal, includes a square wave generator, an identification number encoder for outputting the identification number of the particular animal in the herd, a fever detector with an ambient temperature compensating circuit which provides output only when internal temperature of the animal is above a preset value for a given ambient temperature, and a transmitter which sends the identification code to a receiver. In certain embodiments, no separate fever detector is provided; rather the square wave generator outputs a frequency-modulated signal related to the internal body temperature. Of particular interest is the identification number encoder which intermittently outputs a preset hardwired identification code to the transmitter at periodic intervals for transmission to a receiver either at constant intervals or when temperatures sensed by a temperature detector exceed the variable norm by a preset given amount.

Microbend fiber-optic sensor.

Abstract: Intensity modulation induced by microbending in multimode fibers is considered as a transduction mechanism for detecting environmental changes such as pressure, temperature, acceleration, and magnetic and electric fields. A generic microbend sensor has been defined and studied, and its components, such as sensing fiber, light source, optical fiber leads, and detector, have been examined and optimized. Finally, the generic microbend sensor has been tested demonstrating good performance.

Object detection method and apparatus employing electro-optics

Abstract: Apparatus for detecting the presence of an object within an area under surveillance employs an electro-optical emitter for directing light into the area and an electro-optical receiver for sensing light reflected from the object which originates from the emitter. The emitter emits light energy of a preselected wavelength and is modulated at a preselected frequency to provide the emanating light energy with a characteristic signature. Light reflected by an object within the area under surveillance is filtered and converted to an electrical signal which varies in accordance with the magnitude of the filtered light having the preselected wavelength and modulation frequency. A selected portion of the electrical signal is amplified by a band-pass amplifier and is synchronously sampled in accordance with the modulation frequency to determine the magnitude of the filtered light which originated from the emitter. The sampled signal is compared with a threshold value to determine whether an object is present within the area under surveillance. The emitter and receiver are covered by a transparent shield to protect them against foreign matter. An electro-optic detector monitors the accumulation of foreign particulates on the shield. The apparatus may be desirably used in vehicles to detect the presence of adjacent objects, particularly within the vehicle's "blind spots" and thereby avoid collisions.

Musical tone control apparatus using a detector

Abstract: A musical tone control apparatus controls a musical tone corresponding to a movement itself of an object and the like which is detected by a detector. Such detector detects also a moving speed, a moving force, a moving angle or an intensity of given impulse of the object. In the case where the detector is mounted in the vicinity of a player's joint, the detector detects a revolving or bending angle of the player's joint. Hence, the musical tone can be controlled based on such angle of the player's joint. Thus, through this musical tone control apparatus, the player can generate a musical tone having, for example, a desirable tone pitch, a desirable volume and a desirable tone color based on the movement of the object or the player's joint.

Multispectral system for medical fluorescence imaging

Abstract: The principles of a powerful multicolor imaging system for tissue fluorescence diagnostics are discussed. Four individually spectrally filtered images are formed on a matrix detector by means of a split-mirror arrangement. The four images are processed in a computer, pixel by pixel, by means of mathematical operations, leading to an optimized contrast image, which enhances a selected feature. The system is being developed primarily for medical fluorescence imaging, but has wide applications in fluorescence, reflectance, and transmission monitoring related to a wide range of industrial and environmental problems. The system operation is described for the case of linear imaging on a diode array detector. Laser-induced fluorescence is used for cancer tumor and atherosclerotic plaque demarcation using the contrast enhancement capabilities of this imaging system. Further examples of applications include fluorescing minerals and flames.

Detectors for particle radiation

Abstract: 1. Physics foundations 2. Measurement of ionization 3. Measurement of position 4. Measurement of time 5. Particle identification 6. Measurement of energy 7. Measurement of momentum 8. Applications of detector systems Index.

A system for collection and on-line integration of X-ray diffraction data from a multiwire area detector

Abstract: A system for collecting and measuring X-ray diffraction data from protein crystals has been developed for a multiwire area detector. Computer programs run concurrently on two microcomputers, which collect and reduce detector data to integrated intensities. The self-contained system consists of an X-ray area detector, a rotation/oscillation camera, and two microcomputers connected by a high-speed Ethernet network. One microcomputer is dedicated to operation of the detector, control of the camera, and storage of the raw data. The second microcomputer automatically integrates the data as they are collected and allows the user to monitor the quality of data as they are processed. The integration programs are written in Fortran 77 and have been designed to be portable. Additional programs for crystal alignment, detector and camera control, and graphics are written in the C programming language. A description of the system, some characteristics of the detector, and the results of data collection are presented.

Dynamic response properties of movement detectors: theoretical analysis and electrophysiological investigation in the visual system of the fly

Abstract: Dynamic aspects of the computation of visual motion information are analysed both theoretically and experimentally. The theoretical analysis is based on the type of movement detector which has been proposed to be realized in the visual system of insects (e.g. Hassenstein and Reichardt 1956; Reichardt 1957, 1961; Buchner 1984), but also of man (e.g. van Doorn and Koenderink 1982a, b; van Santen and Sperling 1984; Wilson 1985). The output of both a single movement detector and a one-dimensional array of detectors is formulated mathematically as a function of time. The resulting movement detector theory can be applied to a much wider range of moving stimuli than has been possible on the basis of previous formulations of the detector output. These stimuli comprise one-dimensional “smooth” detector input functions, i.e. functions which can be expanded into a time-dependent convergent Taylor series for any value of the spatial coordinate. The movement detector response can be represented by a power series. Each term of this series consists of one exclusively time-dependent component and of another component that depends, in addition, on the properties of the pattern. Even the exclusively time-dependent components of the movement detector output are not solely determined by the stimulus velocity. They rather depend in a non-linear way on the weighted sum of the instantaneous velocity and all its higher order time derivatives. The latter point represents another reason — not discussed so far in the literature — that movement detectors of the type analysed here do not represent pure velocity sensors. The significance of this movement detector theory is established for the visual system of the fly. This is done by comparing the spatially integrated movement detector response with the functional properties of the directionally-selective motion-sensitive. Horizontal Cells of the third visual ganglion of the fly's brain. These integrate local motion information over large parts of the visual field. The time course of the spatially integrated movement detector response is about proportional to the velocity of the stimulus pattern only as long as the pattern velocity and its time derivatives are sufficiently small. For large velocities and velocity changes of the stimulus pattern characteristic deviations of the response profiles from being proportional to pattern velocity are predicted on the basis of the detector theory developed here. These deviations are clearly reflected in the response of the wide-field Horizontal Cells, thus, providing very specific evidence that the movement detector theory developed here can be applied to motion detection in the fly. The characteristic dynamic features of the theoretically predicted and the experimentally determined cellular responses are exploited to estimate the time constant of the movement detector filter.

Detection of individual 0.4–28 μm wavelength photons via impurity‐impact ionization in a solid‐state photomultiplier

Abstract: A solid‐state device capable of continuous detection of individual photons in the wavelength range from 0.4 to 28 μm is described. Operated with a dc applied bias, its response to the absorption of incident photons consists of submicrosecond rise time pulses with amplitudes well above the electronic readout noise level. A counting quantum efficiency of over 30% has been demonstrated at a wavelength of 20 μm, and over 50% was observed in the visible‐light region. Optimum photon‐counting performance occurs for temperatures between 6 and 10 K and for count rates less than 1010 counts/s per cm2 of detector area. The operating principle of the device is outlined and its performance characteristics as a photon detector are presented.

X-ray scanner for detecting plastic articles

Abstract: An x-ray scanner for detecting plastic articles has an x-ray source which generates a fan-shaped x-ray beam through which an article to be examined is moved. A primary radiation detector array is disposed at a side of the article opposite to the x-ray source and functions to provide a normal x-ray image identifying metal articles. Additional detectors, which detect scatter radiation are disposed around the examination space at a distance from the primary radiation detector. The scatter radiation detectors detect scattered radiation characteristic of that produced by plastic articles. Signals from the scatter radiation detectors are processed, by which the presence of a plastic article can be identified.

Transdermal detection system

Abstract: A transdermal detection system for the detection of a target substance which migrates to the surface of the skin of a subject by diffusion comprises detector means and attachment means. The detector means includes at least one detector chemical contained in solution and capable of chemically reacting with the target substance as the target substance migrates to the skin surface of the subject to produce a detectable signal, and a barrier means for substantially preventing migration of the detector chemical into the skin surface of the subject. The attachment means maintains the detector means adjacent the surface of the skin of the subject.

Method and apparatus for utilizing an electro-optic detector in a microtomography system

Abstract: The present invention is an apparatus and a method for producing tomographic images of an object irradiated by a beam of collimated radiation transmitted in a plurality of rays through a set of coplanar sections of an object as viewed from a plurality of angles about a rotation axis. The apparatus includes an imaging electro-optic detector to record the transmitted radiation, wherein the electro-optic detector alters the image format, the format alteration being focused; means to determine and align the projected position of the rotation axis on the electro-optic detector: means to align the object with respect to the rotation axis; means to determine and assure spatial uniformity detector response; means to reduce signal dependent backgrounds; means to determine the projection coefficients from the transmitted radition with respect to one or more reference calibration exposures; and means to compute a reconstructed image of the object's attenuation coefficients.

Charge transfer device detectors for analytical optical spectroscopy--Operation and characteristics

Abstract: This article is the first in a two-part series describing the operation, characteristics, and application of a new class of solid-state multichannel UV-visible detectors. In this paper, charge transfer devices (CTDs) are described. Detector characteristics pertinent to spectroscopic application—including quantum efficiency, read noise, dark count rate, and available formats—are emphasized. Unique capabilities, such as the ability to nondestructively read out the detector array and the ability to alter the effective detector element size by a process called binning, are described. CTDs with peak quantum efficiencies over 80% and significant responsivity over the wavelength range of 0.1 nm to 1100 nm are discussed. Exceptionally low dark count rates, which allow integration times of up to many hours and read noises more than two orders of magnitude lower than those read by commercially available PDA detectors, contribute to the outstanding performance offered by these detectors.

Tomographic imaging with concentric conical collimator

Abstract: An X-ray imaging apparatus comprising an X-ray source, a collimator, and an X-ray scatter detector. The X-rays are directed toward an object to be imaged where the collimator and detector are located between the source and object. The X-rays striking the object produce back scattered X-rays which are directed back through the collimator to the detector and an image is produced.

Blocked impurity band detectors—an analytical model: Figures of merit

Abstract: We are presenting an analytic model for the figures of merit of a novel extrinsic infrared quantum detector—the blocked impurity band (BIB) detector. The detector consists of top and bottom contacts, a heavily doped active layer, and a nearly intrinsic layer, called the blocking layer, to stop the motion of hopping carriers in the impurity band. The responsivity, gain, excess noise factor, and detectivity of the BIB detector are calculated as functions of the device dimensions, doping concentrations, and the applied reverse bias, which controls the electric field in the depletion region, devoid of hopping carriers, of the device underneath the blocking layer. Central to our model is the inclusion of impact ionization of carriers in the calculation of the detector response and of the associated noise. For practical detector dimensions and doping concentrations, and at 2‐V reverse bias, we calculate the responsivity to be on the order of 2 A/W, and detectivities, with 1012 photons/cm2 s background photon fl...

Channel Modeling and Threshold Signal Processing in Underwater Acoustics: An Analytical Overview

Abstract: An overview of underwater acoustic channel modeling and threshold signal processing is presented, which emphasizes the inhomogeneous, random, and non-Ganssian nature of the generalized channel, combined with appropriate weak-signal detection and estimation. Principal attention is given to the formal structuring of the scattered and ambient acoustic noise fields, as well as that of the desired signal, including both fading and Doppler "smear" phenomena. The role of general receiving arrays is noted, as well as their impact on spatial and temporal signal processing and beam forming, as indicated by various performance measures in detection and estimation. The emphasis here is on limiting optimum threshold systems, with some attention to suboptimum cases. Specific first-order probability density functions (pdf's) for the non-Ganssian components of typical underwater acoustic noise environments are included along with their field covariances. Several examples incorporating these pdf's are given, to illustrate the applications and general methods involved. The fundamental role of the detector structure in determining the associated optimum estimators is noted: the estimators arc specific linear or nonlinear functionals of the original optimum detector algorithm, depending on the criterion (i.e., minimization of the chosen error or cost function) selected. Results for both coherent and incoherent modes of reception are presented, reflecting the fact that frequently signal epoch is not known initially at the receiver. To supplement the general discussion, a selected list of references is included, to provide direct access to specific detailed problems, techniques, and results, for which the present paper is only a guide.

Comparison Of Phase-Measurement Algorithms

Abstract: Phase-measurement algorithms for calculating the phase of a wavefront from interference fringe data are compared. Experimental data show that different algorithms yield different phase values when using the same intensity data. A computer simulation of errors due to phase-shifter miscalibration and nonlinearity, as well as detector nonlinearity is performed to show that certain algorithms are more sensitive to some errors than others. Dependences of each of these errors is found versus percent of error over a 2ic range of phase values. These results enable the determination of what system errors are present in a phase-measurement interferometer.

Spectrochemical Measurements with Multichannel Integrating Detectors

Abstract: This is the second article in a two-part series describing the operation, performance characteristics, and spectroscopic application of charge transfer devices (CTDs) in analytical chemistry. The first article in the series describes the new generation of integrating multichannel detectors, the charge injection device (CID), and the charge-coupled device (CCD). The first article also discusses the spectroscopically pertinent characteristics of these detectors and presents performance data for representative devices. This article covers three major topics related to the optimum use of integrating detectors in analytical spectroscopy. The advantages of employing integrating multichannel detectors in analytical spectroscopy, rather than a single detector in a wavelength scanning system or an interferometer, are discussed. Included are detector read noise considerations which have not been considered in previous performance comparisons. When one is employing an integrating detector in luminescence, absorption, and emission applications, achievable sensitivity is dependent on differing detector parameters. In the first case, quantum efficiency and read noise are of the greatest importance, whereas in the later two cases, dynamic range is most significant. The calculation of minimum detectable analyte signal for these three techniques illustrates the differences between integrating detectors and detectors which produce a photocurrent. This discussion also illustrates the great sensitivity that can be achieved with a modern CTD detector. Factors pertaining to the optical design of spectrometers which efficiently use CTDs are presented, along with examples of linear and two-dimensional dispersive polychromators employing CTDs. Low-light-level imaging and a nonconventional method of using a CCD for rapid scanning spectro-photometry are also discussed.