Showing papers on "Detector published in 1996"

Two-dimensional detector software: From real detector to idealised image or two-theta scan

Abstract: Detector systems introduce distortions into acquired data. To obtain accurate angle and intensity information, it is necessary to calibrate, and apply corrections. Intensity non-linearity, spatial distortion, and non-uniformity of intensity response, are the primary considerations. It is better to account for the distortions within scientific analysis software, but often it is more practical to correct the distortions to produce ‘idealised’ data. Calibration methods and software have been developed for single crystal diffraction experiments, using both approaches. For powder diffraction experiments the additional task of converting a two-dimensional image to a one-dimensional spectrum is used to allow Rietveld analysis. This task may be combined with distortion correction to produce intensity information and error estimates. High-pressure experiments can introduce additional complications and place new demands on software. Flexibility is needed to be able to integrate different angular regions se...

Semiconductor ultraviolet detectors

Abstract: In this review article a comprehensive analysis of the developments in ultraviolet (UV) detector technology is described. At the beginning, the classification of UV detectors and general requirements imposed on these detectors are presented. Further considerations are restricted to modern semiconductor UV detectors, so the basic theory of photoconductive and photovoltaic detectors is presented in a uniform way convenient for various detector materials. Next, the current state of the art of different types of semiconductor UV detectors is presented. Hitherto, the semiconductor UV detectors have been mainly fabricated using Si. Industries such as the aerospace, automotive, petroleum, and others have continuously provided the impetus pushing the development of fringe technologies which are tolerant of increasingly high temperatures and hostile environments. As a result, the main efforts are currently directed to a new generation of UV detectors fabricated from wide band‐gap semiconductors the most promising ...

MICROMEGAS: a high-granularity position-sensitive gaseous detector for high particle-flux environments

Abstract: We describe a novel structure for a gaseous detector that is under development at Saclay. It consists of a two-stage parallet-plate avalanche chamber of small amplification gap (100 μm) combined with a conversion-drift space. It follows a fast removal of positive ions produced during the avalanche development. Fast signals (≤1 ns) are obtained during the collection of the electron avalanche on the anode microstrip plane. The positive ion signal has a duration of 100 ns. The fast evacuation of positive ions combined with the high granularity of the detector provide a high rate capability. Gas gains of up to 10 5 have been achieved.

Detection, mixing, and frequency multiplication of terahertz radiation by two-dimensional electronic fluid

Abstract: We show that a short channel High Electron Mobility Transistor (HEMT) has a resonance response to electromagnetic radiation at the plasma oscillation frequencies of the two dimensional electrons in the device. This response can be used for new types of detectors, mixers, and multipliers. These devices should operate at much higher frequencies than conventional, transit-time limited devices, since the plasma waves propagate much faster than electrons. The responsivities of such devices may greatly exceed the responsivities of Schottky diodes currently used as detectors and mixers in the terahertz range. A long channel HEMT has a nonresonant response to electromagnetic radiation and can be used as a broadband detector for frequencies up to several tens of terahertz.

Generation and detection of terahertz pulses from biased semiconductor antennas

Abstract: We propose a simple model based on the Drude–Lorentz theory of carrier transport to account for the details of the ultrashort terahertz pulses radiated from small photoconductive semiconductor antennas. The dynamics of the bias field under the influence of the space-charge field from the accelerated carriers is included in the model. We consider in detail the optical system used to image the terahertz radiation onto the terahertz detector, and we calculate the frequency-dependent response of the detector. The proposed model is compared with several different experiments, each focusing on different parameters of the model. Agreement between experiment and model is found in all cases, supporting the validity of this simple and appropriate model.

A quantitative model of the "effective" signal processing in the auditory system. I. Model structure.

Abstract: This paper describes a quantitative model for signal processing in the auditory system. The model combines a series of preprocessing stages with an optimal detector as the decision device. The present paper gives a description of the various preprocessing stages and of the implementation of the optimal detector. The output of the preprocessing stages is a time‐varying activity pattern to which ‘‘internal noise’’ is added. In the decision process, a stored temporal representation of the signal to be detected (template) is compared with the actual activity pattern. The comparison amounts to calculating the correlation between the two temporal patterns and is comparable to a ‘‘matched filtering’’ process. The detector itself derives the template at the beginning of each simulated threshold measurement from a suprathreshold value of the stimulus. The model allows one to estimate thresholds with the same signals and psychophysical procedures as those used in actual experiments. In the accompanying paper [Dau et al., J. Acoust. Soc. Am. 99, •••–••• (1996)] data obtained for human observers are compared with the optimal‐detector model for various masking conditions.

Plasma wave electronics: novel terahertz devices using two dimensional electron fluid

Abstract: We discuss how the propagation of plasma waves in a High Electron Mobility Transistor (HEMT) can be used to implement a new generation of terahertz devices, including sources, resonant detectors, broad band detectors, and frequency multipliers. Our estimates show that these devices should outperform conventional terahertz devices, which use deep submicron Schottky diodes.

Exciter-detector unit for measuring physiological parameters

Abstract: An exciter-detector unit is disclosed which includes an exciter (104) and a detector (105) mounted on a common support (101) for inducing perturbations into the body and detecting the perturbations after they travel a distance through the body.

Free-hand aiming of a needle guide

Abstract: This invention is a method for free-hand directing of a needle (12) towards a target (16) located in a body volume, the method including the steps of producing an image of the target and the body volume (18), transmitting the image by means of an imaging detector (28) to a display screen (22) which communicates with a position sensing controller (20), sensing spatial orientation data of the imaging detector with respect to a reference, transmitting the spatial orientation data of the imaging detector to the position sensing controller, displaying the spatial orientation data onto the display screen, placing the needle with a point thereof substantially pointing at the target sensing spatial orientation data of the needle with respect to the reference, transmitting the spatial orientation data of the needle to the position sensing controller, causing the position sensing controller, based on the spatial orientation data of the imaging detector and of the needle, to indicate on the display screen a trajectory of the needle point, and inserting the needle into the body volume towards the target in accordance with the trajectory indicated on the display screen.

Remote control system

Abstract: A remote control system includes a remote control unit and a controlled unit. The remote control unit is moved in space, and includes a movement detector, selection switch and transmitter. The movement detector detects movement of the remote control unit. The transmitter transmits output of the movement detector and the selection switch. The controlled unit includes a display device, receiver, and controller. The display device includes a display screen, and displays a cursor and icons on the display screen. The receiver receives the output of the movement detector and the selection switch transmitted by the transmitter. The controller moves the cursor across the display screen in accordance with the output of the movement detector and the selection switch.

Performance of the DELPHI detector

Abstract: DELPHI (DEtector with Lepton, Photon and Hadron Identification) is a detector for e^+e^- physics, designed to provide high granularity over a 4\pi solid angle, allowing an effective particle identification. It has been operating at the LEP (Large Electron-Positron) collider at CERN since 1989. This article reviews its performance.

Electromagnetic noise detector for implantable medical devices

Abstract: Disclosed are apparatus and method for detecting electromagnetic interference (EMI), or noise, that may disrupt the proper operation of medical devices (10) implantable in patients, such as cardiac stimulators. Circuitry of the detector of the invention is independent of other circuitry of the medical device. EMI is magnetically induced on an antenna (40) that may be within the metal housing (252) of the device (10) in a receiver circuit (40), and the EMI signals are output to the noise detector (66, 68). A variety of alert signals may be provided to the medical device circuitry to warn of the presence of EMI so that appropriate responses may be taken to insure the safety of the patient dependent on the device. The detector may share the telemetry antenna of the medical device, or utilize a separate, dedicated antenna to receive EMI. Alternative antennas external to the metal housing of the medical device include leads from the device to the heart of the patient, and a dedicated antenna (260) in the nonmetal header (254) of the device.

Sleep detection and driver alert apparatus

Abstract: A sleep detection and driver alert apparatus has a compact housing that can be placed around the rearview mirror or on the dashboard. It contains all lenses and electronic detection mechanisms for monitoring the effects of early impending sleep by means of an infrared auto-focusing, digital, image stabilizing lens with zoom capability. Additionally, the unit contains an added infrared thermal sensor for the monitoring and evaluation of different ambient temperatures around the facial areas of the nose and mouth. These temperature changes will be that of the exhaled gas plume of normal breathing patterns, which will lower in volume as the driver begins to hypoventilate, thus increasing their blood level of carbon dioxide which is in most part the reason for early drowsiness associated with sleep. The device will monitor via the infrared camera the thermal image changes in pixel color of open versus closed eyes of the driver via the temperature sensitive infrared portion of the digitized photographic image passed through a video charge coupling device. The combination of non movement and a decrease in breath temperature, which is a physiological response to hypoventilation thus initiating drowsiness, will trigger the infrared camera to zoom onto the eye region of the driver. This combined data is routed to the sleep status microprocessor memory via the optical image detector and thermal sensor for data changes above or below baseline data measurements.

Fast locking mechanism for channelized ultrawide-band communications

Abstract: A receiver for acquisition and lock of an impulse radio signal comprising an adjustable time base to output a sliding periodic timing signal having an adjustable repetition rate, and a decode timing modulator to output a decode signal in response to the periodic timing signal. The impulse radio signal is cross correlated with the decode signal to output a baseband signal. The receiver integrates T samples of the baseband signal and a threshold detector uses the integration results to detect channel coincidence. A receiver controller stops sliding the time base when channel coincidence is detected. A counter and extra count logic, coupled to the controller, are configured to increment or decrement the address counter by a one or more extra counts after each T pulses is reached in order to shift the PN code modulo for proper phase alignment of the periodic timing signal and the received impulse radio signal.

Optical ranging camera

Abstract: Apparatus for creating an image indicating distances to objects in a scene, comprising: a modulated source of radiation, having a first modulation function, which directs radiation toward a scene; a detector, which detects radiation reflected from the scene, modulated by a second modulation function, and generates, responsive to said detected modulated radiation, signals responsive to the distance to regions of the scene; a processor, which receives signals from the detector and forms an image, based on the signals, having an intensity value distribution indicative of the distance of objects from the apparatus; and a controller, which varies at least one of the first and second modulation functions, responsive to the intensity value distribution of the image formed by the processor.

X‐ray detection using a superconducting transition‐edge sensor microcalorimeter with electrothermal feedback

Abstract: We have developed a new type of x‐ray detector based on a superconducting transition‐edge thermometer operated near 100 mK. A superconducting quantum interference device is used to measure the current through the thermometer, and negative electrothermal feedback is used to improve the energy resolution and shorten the thermal time constant. We have used a detector mounted on a scanning electron microscope to measure the energy of titanium Kα (4.5 keV) fluorescence x rays with a resolution better than 14 eV full width at half‐maximum. Using two other devices, we have measured an energy resolution for Joule heat pulses of 2.6 eV at 1 keV and 0.2 eV at 4 eV, the best reported for any calorimeter. An electrical noise equivalent power of 3×10−18 W/√Hz was also measured, suggesting the use of these detectors as infrared bolometers.

System and method for performing real time data acquisition, process modeling and fault detection of wafer fabrication processes

Abstract: A system and method for detecting faults in wafer fabrication process tools by acquiring real-time process parameter signal data samples used to model the process performed by the process tool. The system includes a computer system including a DAQ device, which acquires the data samples, and a fault detector program which employs a process model program to analyze the data samples for the purpose of detecting faults. The model uses data samples in a reference database acquired from previous known good runs of the process tool. The fault detector notifies a process tool operator of any faults which occur thus potentially avoiding wafer scrap and potentially improving mean time between failures. The fault detector also receives notification of the occurrence of process events from the process tool, such as the start or end of processing a wafer, which the fault detector uses to start and stop the data acquisition, respectively. The fault detector also receives notification of the occurrence of a new process recipe and uses the recipe information to select the appropriate model for modeling the data samples. The fault detector employs a standard data exchange interface, such as DDE, between the fault detector and the model, thus facilitating modular selection of models best suited to the particular fabrication process being modeled. Embodiments are contemplated which use a UPM model, a PCA model, or a neural network model.

Single optical photon detection with a superconducting tunnel junction

Abstract: THE charge-coupled device (CCD) has become the detector of choice in optical astronomy. CCDs provide a very linear response to detected photons, are very efficient at some wavelengths, and can now provide coverage of a relatively wide field of view1–3. But they become quite inefficient with decreasing wavelength, and they lack intrinsic wavelength and time resolution. The only way to select specific wavelengths is to place filters in front of the detector, which makes the total system less efficient. Time resolution can be achieved only with short exposures, which are possible only with very bright sources. Here we report a superconducting device that can overcome these limitations, and which has performance characteristics far superior to existing photon counting systems4–7. Our superconducting tunnel junction can detect individual photons at rates up to 2.5 kHz in the wavelength range 200–500 nm, with an intrinsic spectral resolution of 45 nm and a quantum efficiency estimated to be about 50 per cent. The theoretical resolution of the present device is ∼ 20 nm, but use of superconductors with lower transition temperature could improve that to 8 nm.

Three dimensional camera

Abstract: Apparatus for creating an image indicating distances to points in objects in a scene, comprising: a modulated source of radiation, having a first modulation function, which directs radiation toward a scene such that a portion of the modulated radiation is reflected from the points and reaches the apparatus; an array detector which detects radiation from the scene, modulated by a second modulation function, each element of the array detector being associated with a point in the scene, each element of the array detector generating a signal, responsive to a part of the reflected radiation reaching the apparatus, the magnitude of particular element's signal being dependent on the distance of a point in the scene, associated with that element's signal; and a processor which forms an image, having an intensity value distribution indicative of the distance of each of the points in the scene from the apparatus, based on the magnitude of the signal associated with the point; wherein the first and second modulation functions comprise repetitive pulsed modulation functions which are different from each other.

Hybrid motion tracker

Abstract: A hybrid motion tracker captures the motion of a person. Magnetic field sensors and optical sources are placed on a person, each located on different limbs. A fixed transmitter emits electromagnetic energy and infrared light is transmitted from the optical light sources to the fixed optical sensors. The magnetic field sensors sense the magnetic field and a computer calculates each sensor's position and orientation relative to the fixed transmitter. The optical system's Position Sensing Detectors measure the transmitted infrared light and the computer calculates the position and orientation of each optical light source. The position and orientation of each sensor is used to reconstruct the person's motion in real time, which is sent to a host computer. The computer utilizes the optical system which is more precise than the magnetic field system to compensate for the magnetic field system and thereby achieve higher accuracies. The system is a hybrid system using both magnetic fields and infrared light. By combining the two different technologies into one system, all of the advantages of the two systems by themselves are employed and none of their disadvantages become detrimental, in particular, accuracy and dynamic performance are enhanced over results obtained through sole use of a magnetically based system.

Influence of the scattering phase function on light transport measurements in turbid media performed with small source-detector separations.

Abstract: Many methods of optical tissue diagnosis require that measurements be performed with small source-detector separations in a backscatter geometry. Monte Carlo simulations are used to demonstrate that for these situations light transport depends on the exact form of the angular scattering probability distribution, P(theta). Simulations performed with different forms of P(theta) with the same value of ?cos theta? result in the collection of significantly different fractions of the incident photons, particularly when small-numerical-aperture delivery and collection fibers are employed. More photons are collected for the distribution that has a higher probability of scattering events with theta > 125 degrees . For the clinically relevant optical parameters employed here, the differences in light collection are >60%.

Hopfield neural network implementation of the optimal CDMA multiuser detector

Abstract: We investigate the application of Hopfield neural networks (HNN's) to the problem of multiuser detection in spread spectrum/CDMA (code division multiple access) communication systems. It is shown that the NP-complete problem of minimizing the objective function of the optimal multiuser detector (OMD) can be translated into minimizing an HNN "energy" function, thus allowing to take advantage of the ability of HNN's to perform very fast gradient descent algorithms in analog hardware and produce in real-time suboptimal solutions to hard combinatorial optimization problems. The performance of the proposed HNN receiver is evaluated via computer simulations and compared to that of other suboptimal schemes as well as to that of the OMD for both the synchronous and the asynchronous CDMA transmission cases. It is shown that the HNN detector exhibits a number of attractive properties and that it provides a powerful generalization of a well-known and extensively studied suboptimal scheme, namely the multistage detector.

Low cost apparatus for detecting arcing faults and circuit breaker incorporating same

Abstract: A low cost analog arcing detector and a circuit breaker incorporating such a detector provide a variable response time to arcing faults based upon the amplitude of the arcing current. A filter generates pulses having an amplitude proportional to the amplitude of the step increase in current generated by the striking of the arc. The pulses are rectified and the amount by which the single polarity pulses exceed a threshold value, selected to eliminate nuisance trips on current step increases characteristic of some common loads, is integrated by a capacitor connected to a resistor which continually adjusts the capacitor voltage in a sense opposite to that of the pulses. The capacitor and resistor are selected to generate a trip signal as a function of the accumulated, time attenuated magnitude of the step increases in current associated with each striking of the arc current. Preferably, the pulses are squared before the reference current is subtracted to provide faster response for large amplitude arc currents, while avoiding false trips caused by known loads. Preferably, the arcing detector is used with a ground current detector which provides further protection by tripping on ground currents flowing through carbon tracks deposited by arcing currents below the threshold of the arcing fault detector.

Solid-state image sensor with focal-plane digital photon-counting pixel array

Abstract: A solid-state focal-plane imaging system comprises an N×N array of high gain, low-noise unit cells, each unit cell being connected to a different one of photovoltaic detector diodes, one for each unit cell, interspersed in the array for ultralow level image detection and a plurality of digital counters coupled to the outputs of the unit cell by a multiplexer (either a separate counter for each unit cell or a row of N of counters time shared with N rows of digital counters). Each unit cell includes two self-biasing cascode amplifiers in cascade for a high charge-to-voltage conversion gain (>1 mV/e - ) and an electronic switch to reset input capacitance to a reference potential in order to be able to discriminate detection of an incident photon by the photoelectron (e - ) generated in the detector diode at the input of the first cascode amplifier in order to count incident photons individually in a digital counter connected to the output of the second cascode amplifier. Reseting the input capacitance and initiating self-biasing of the amplifiers occurs every clock cycle of an integratng period to enable ultralow light level image detection by the array of photovoltaic detector diodes under such ultralow light level conditions that the photon flux will statistically provide only a single photon at a time incident on any one detector diode during any clock cycle.

Sleep apnea detector system

Abstract: An apnea monitor and system for treatment includes a detector in a fixed console that projects a detection beam at a sleep surface. The detection beam is reflected off a patient on the surface and return light is analyzed to develop a signal which varies with external motion of the patient's upper body. The motion signals are then fed to a pattern recognizer which identifies breath signals and analyzes them to detect cessation or excessive pauses in breathing, and trigger an alarm or intervention to restore breathing regularity. The monitor includes a laser for generating radiation. The radiation is reflected from the patient and is directed onto a detector. The detector produces output signals corresponding to the impinging reflected light, which are processed by a control element to determine the change of movement, e.g., the breathing rate, of the patient.

Radio transmitter and method of controlling transmission by radio transmitter

Abstract: APC circuitry used for a radio transmitter comprises a detector (7) which detects a radio frequency (RF) output signal (5) to output a detection signal (8), an integrator (15) which integrates the detection signal (8) to output a power signal (16) representing the average power level of the RF output signal (5), a control unit (18) for calculating an error level from the difference between the average power level and a reference power level which corresponds to a predetermined power of the RF output signal (5), and for multiplying the error level by a correction coefficient so as to calculate a control signal correction value for correcting the value of a control signal (14) and then generate control data the digital value of which is corrected according to the control signal correction value and a reference control value that is predetermined so as to generate the RF output signal (5) having the predetermined power.

Device for diagnosing physiological state and device for controlling the same

Abstract: The present invention relates to a device for diagnosing physiological state based on blood pulse waves detected in the body. It is the objective of the present invention to provide a device which correctly diagnoses the current physiological state based on changes in physiological state measured over a specified period of time in the past while taking into consideration the cyclical variation exhibited in physiological state. In order to realize this objective, the device according to the present invention has as its main components: blood pulse wave detector 381 and stroke-volume-per-beat measurer 382 which respectively detect blood pulse wave and stroke volume in the body; blood pulse wave extraction memory 386 which extracts characteristic information from the detected blood pulse wave; memory 383 in which the physiological state calculated from the stroke volume and this characteristic information is stored; output portion 385 which outputs an alarm; and microcomputer 387 which controls each part inside the device. The microcomputer calculates the circulatory parameters based on characteristic information obtained from the waveform extraction memory, and stores the parameters in memory at specified time intervals. At these times, microcomputer 387 calculates the circulatory parameters from the stroke volume per beat and the characteristic information of the blood pulse wave at specified time intervals, and stores the parameters in memory 383. Further, microcomputer 387 reads out from memory 383 the circulatory parameters from a specified time interval in the past, and calculates the average value and standard deviation. Microcomputer 387 then determines whether or not the current circulatory parameters are within a specified range determined by their average value and standard deviation. When the circulatory parameters are determined to be outside this range, microcomputer 387 controls output portion 385 to sound an alarm.

Sub-sampled discrete time read channel for computer storage systems

Abstract: A sampled amplitude read channel is disclosed for reading binary data from a computer disk storage system, wherein the read channel sub-samples an analog read signal at a rate lower than the baud rate and detects the binary data from the sub-sampled values using a sequence detector. In one embodiment, the sub-sampled values are interpolated to generate synchronous sample values which are processed by a conventional sequence detector. In another embodiment, the sequence detector is modified to detect the binary data directly from the sub-sampled values. In yet another embodiment, the sequence detector comprises a remodulator and an error pattern detector for detecting and correcting bit errors in the detected binary data. In addition, for the various embodiments a channel code increases the distance property of the sequence detector in order to compensate for the degradation in performance caused by sub-sampling.