Showing papers on "Detector published in 1993"

Decorrelating decision-feedback multiuser detector for synchronous code-division multiple-access channel

Abstract: A decorrelating decision-feedback detector (DF) for synchronous code-division multiple-access (CDMA) that uses decisions of the stronger users when forming decisions for the weaker ones is described. The complexity of the DF is linear in the number of users, and it requires only one decision per user. It is shown that performance gains with respect to the linear decorrelating detector are more significant for relatively weak users and that the error probability of the weakest user approaches the single-user bound as interferers grow stronger. The error rate of the DF is compared to those of the decorrelator and the two-stage detector. >

Micro pulse lidar

Abstract: An eye safe, compact, solid-state lidar for profiling atmospheric cloud and aerosol scattering is described. The transmitter of the micro pulse lidar is a diode pumped microjoule pulse energy, high-repetition-rate Nd:YLF laser. Eye safety is obtained through beam expansion. The receiver uses a photon counting solid-state Geiger mode avalanche photodiode detector. Data acquisition is by a single card multichannel scaler. Daytime background induced quantum noise is controlled by a narrow receiver field-of-view (FOV) and a narrow bandwidth temperature controlled interference filter. Dynamic range of the signal is limited by optical geometric signal compression. Signal simulations and initial atmospheric measurements indicate that systems built on the micro pulse lidar concept are capable of detecting and profiling all significant cloud and aerosol scattering through the troposphere and into the stratosphere. The intended applications are scientific studies and environmental monitoring. which require full-time unattended measurements of the cloud and aerosol height structure. >

The tomographic atom probe: A quantitative three‐dimensional nanoanalytical instrument on an atomic scale

Abstract: The physical architecture and the performance of a quantitative three‐dimensional atom probe recently constructed are described. The development of such an instrument relies on the design of a multi‐impact position sensitive detector. The multidetection system that we have developed is based on the use of a 10×10 anode array placed behind a two microchannel plate assembly in a chevron arrangement. The spread of charge between the microchannel plate and the multianode is used to derive the position of ion striking the detector. Spatial coordinates can be calculated for multiple and simultaneous time‐of‐flight events. The procedure used for the derivation of ion positions from charge measurements is given. Specific experiments were carried out in order to determine the intrinsic spatial resolution of the multidetector. Three‐dimensional reconstruction of two‐phase materials are provided and illustrate the performance of this new apparatus. The reconstructed images demonstrate that atoms are positioned with a precision of a few tenths of a nanometer. The mass resolution M/ΔM (FWHM) of the apparatus is close to 200.

Programmable portable infusion pump system.

Abstract: A portable and programmable infusion pump system is disclosed for injecting one or more medicinal substances into an individual under the control of the individual. A common controller unit and microprocessor is provided for one or more pump units. Each pump unit includes a chamber for holding a medicinal substance, an infusion tube that is connected to the chamber and is adapted to be connected to the individual, and a motor driven pump for pumping the medicinal substance through the infusion tube. The individual programs the microprocessor to perform one or more infusion processes by use of a keyboard, a card reader, a bar code reader, or a modem. Each motor and pump are controlled in accordance with its program parameters as contained in the programmed microprocessor. A pressure sensor and an air bubble detector is associated with each infusion tube, and these sensors and detectors are connected to the microprocessor.

Disposable pulse oximeter sensor

Abstract: A conformable sensor which uses a flexible substrate, preferably a polyester strip is disclosed The emitter and detector are mounted on one portion of the strip with conductive traces connecting to them The second portion of the strip is folded over to cover the emitter and detector and traces, with openings for the emitter and detector A conductive coating is applied to the strip to provide shielding from electromagnetic interference Preferably, a second portion of the strip, which folds over the first portion, also has a Faraday shield covering the opening over the detector The detector and emitter semiconductor chip die (rather than use encapsulated chips) may be mounted directly on the polyester strip so that it is in contact with one of the conductive traces

Focal plane imaging systems for millimeter wavelengths

Abstract: The authors discuss critical aspects of imaging system design and describe several different imaging systems employing focal plane array receivers operating in the 3-mm-2-mm wavelength range. Recent progress in millimeter-wavelength optics, antennas, receivers and other components permits greatly enhanced system performance in a wide range of applications. A radiometric camera for all-weather autonomous aircraft landing capability and a high sensitivity cryogenically cooled array for use in radio astronomical spectroscopy are presented. A near-focus system for identification of plastic materials concealed underneath clothing employs a two element lens, and has been demonstrated in active (transmitting) and passive (radiometric) modes. A dual-mode imaging system for plasma diagnostics utilizes both active and passive modes at its approximately=140-GHz operating frequency to study small-scale structure. The radiometric imaging systems employ between 15 and 256 Schottky barrier diode mixers, while the imaging receivers for the active systems include 64-element video detector arrays. >

Erratum: ‘‘Calibration of atomic‐force microscope tips’’ [Rev. Sci. Instrum. 64, 1868 (1993)]

Abstract: In our calibration of atomic-force microscope cantilevers, we neglected to correct for the frequency response of the optical-detection electronics. The response to cantilever vibrations will have a high-frequency cut-off, which, in our case, was higher than the resonant frequency of the cantilever. Our results were not affected, but for higher resonant frequencies, one should calibrate the detector response. We thank V. Croquette for raising this point.

Optical scanning head with improved resolution

Abstract: The optical scanning head comprises two or more LEDs which are oriented to emit light at different angles so that a fan of light is created. A "dark room" encloses the LEDs, a lens assembly, and the spacing between the lens assembly and the detector, a linear CCD array. The portion of the dark room that extends between the lens assembly and the detector has a plurality of baffles formed therein to capture scattered light, preventing this scattered light from becoming noise at the detector. The lens assembly includes, along with a plurality of focusing lenses, a combination of a generally elliptical aperture, or "cat's eye, and a rectangular obscuration. The combination prevents the central lobe of the Airy disk generated by the incoming light from being transmitted to the detector. This results in the incoming information being carried in the outer lobes or rings, increasing the angular separation of the lines of the bar code. Waveshaping software is incorporated in the decoding processor to compensate for the limitations of the imaging system, which include convolution distortion and the resulting loss of image contrast. This software is used to determine the scan parameters including global threshold for the next scan. As an alternative to use of a global threshold, a sliding frame buffer is used to generate pseudo-pixel numbers to fill in the space between physical pixels in the detector, providing a greater number of effective pixels to obtain better resolution.

Fast imaging using subencoding data sets from multiple detectors

Abstract: A new fast imaging method using a subencoding data acquisition scheme and a multiple coil receiver system is proposed and demonstrated. In this method, a set of aliased images are produced from receiver coils by using the subencoded data without sacrificing the desired resolution, and resolved to an aliasing-free image by using the distance-dependent sensitivity information of each coil. The reduction rate of data acquisition time is proportional to the number of receiver coils. This method can be easily adapted to conventional imaging methods including fast imaging to further reduce the scan time.

OFDM/FM frame synchronization for mobile radio data communication

Abstract: A synchronization scheme enabling the use of orthogonal frequency division multiplexing (OFDM)/FM over a mobile radio channel in a pure ALOHA environment is proposed. The scheme encodes synchronization information in parallel with data in the same manner in which data is encoded in the OFDM/FM frame. The synchronization information is in the form of tones, centered in certain reserved frequency subchannels of the OFDM signal. The receiver uses a correlation detector, implemented in the frequency domain, to acquire synchronization accurately on a packet-by-packet basis. Experimental results indicate that the bit-error-rate performance achievable with the proposed scheme is within 1.5 dB of the performance obtained with ideal synchronization. >

Voice activity detector for speech signals in variable background noise

Abstract: A voice activity detector (VAD) which determines whether received voice signal samples contain speech by deriving parameters measuring short term time domain characteristics of the input signal, including the average signal level and the absolute value of any change in average signal level, and comparing the derived parameter values with corresponding thresholds, which are periodically monitored and updated to reflect changes in the level of background noise, thereby minimizing clipping and false alarms.

Disk drive using PRML class IV sampling data detection with digital adaptive equalization

Abstract: A class IV partial response, maximum likelihood data channel for a disk drive includes an encoder connected to a data sequencer for converting user data blocks into a predetermined 8/9ths code such as a (0,4,4,) code. A precoder converts the 8/9ths code into class IV code. An analog write driver supplies the class IV code to a data transducer head during data write-to-disk operations. A read channel connected to the head amplifies and conditions analog signals during data read operations. A quantizer produces samples of the analog signals in accordance with a quantization clock generated by a clock generator. An adaptive FIR filter means is conditions the data samples in accordance with selectable, adaptive filter coefficients. A Viterbi detector puts out the class IV code from the filtered and quantized samples. A postcoder converts the detected class IV code into detected 8/9ths code. A decoder converts the detected 8/9ths code into user data and supplies user data to the sequencer. The programmable FIR filter is provided with servo coefficients during reading of the servo sectors, and an asynchronous servo detector detects head position information from the quantized and filtered samples without phase locking of the quantization clock generator to the quantized servo samples. The asynchronous servo detector is also used to aid detection of sync field preamble information before the FIR filter is fully adapted. Multi-mode gain and timing loops are also a part of the present invention.

Ultrasensitive‐hot‐electron microbolometer

Abstract: We present measurements on a novel power detector which can be used as an ultrasensitive detector of millimeter and submillimeter radiation. The absorbing element consists of a thin film resistor strip which is connected to superconducting electrodes. This device exploits the Andreev reflection of electrons and the weak electron‐phonon coupling at low temperatures to produce a large temperature rise for a small input power (≊10 mK/fW). The temperature rise of the electrons is detected by a tunnel junction where part of the metal strip forms the normal electrode. We have measured a voltage responsivity of approximately 109 V/W and an amplifier‐limited electrical noise equivalent power ≊3×10−18 W Hz−1/2 at an operating temperature of 100 mK. If infrared radiation were efficiently coupled to the absorbing element with an antenna or a waveguide, then the sensitivity of this detector would be at least a factor of 10 better than the best available direct detector operating at the same temperature.

Active hand controller feedback loop

Abstract: An active hand controller system is provided wherein a feedback loop detects the position of a control stick to control a motor driving the control stick to thereby provide certain force feel characteristics to the control stick. The feedback loop includes a detector for detecting force exerted for the control stick to generate a signal indicative of the force or torque being applied to the control stick. In a more specific aspect, the invention includes the use of variable reluctance transformers, preferably in a push/pull configuration to detect the forces being exerted on the control stick.

Interferometric quantum cryptographic key distribution system

Abstract: An apparatus and method for distributing cryptographic key information is described incorporating a quantum channel for conveying dim and reference light pulses, a timing channel, a source of coherent light pulses, beamsplitters, a random number generator, a phase modulator and a memory for recording the phase of transmitted dim light pulses. A cryptographic key receiver is described incorporating beam splitters, a random number generator, a phase modulator, a detector and a memory for recording the phase of received dim light pulses. The invention overcomes the problem of distributing fresh cryptographic key information between two users who share no secret information initially.

A flexible printed circuit sensor assembly for detecting optical pulses

Abstract: A flexible sensor assembly for detecting optical pulses in which said sensor assembly comprises a flexible printed circuit having mounted thereon at least one light emitting diode and at least one photoelectric detector connected to different circuit patterns with an insulative tape secured over the circuit and components and wherein the flexible sensor is adapted to be folded so that the photoelectric detector can be spaced from and disposed over the light emitting diode.

The performance of the ZEUS central tracking detector z-by-timing electronics in a transputer based data acquisition system

Abstract: The Central Tracking Detector of the ZEUS experiment employs a time difference technique to measure the z coordinate of each hit. The method provides fast, three-dimensional space point measurements which are used as input to all levels of the ZEUS trigger. Such a tracking trigger is essential in order to discriminate against events with vertices lying outside the nominal electron-proton interaction region. Since the beam crossing interval of the HERA collider is 96 ns, all data must be pipelined through the front-end readout electronics. Subsequent data aquisition employs a novel technique which utilizes a network of approximately 120 INMOS transputers to process the data in parallel. The z-by-timing method and its data aquisition have been employed successfully in recording and reconstructing tracks from electron-proton interactions in ZEUS.

Spatial resolution of silicon microstrip detectors

Abstract: The spatial resolution of silicon microstrip detectors is studied as a function of the main detector parameters and of the track angle. Several algorithms for finding the position of particle hits are presented and analysed. Analytic expressions of the spatial resolution are derived for the main algorithms. Using a Monte Carlo simulation, the spatial resolution is calculated for each algorithm and, for each detector design and track geometry, the algorithm that gives the best resolution is determined.

Personal identification system

Abstract: A personal identification system includes a number of antenna preamplifier nodes coupled to collection nodes which are in turn coupled to a central computer. A personal detector unit attached to a user is inserted into an enclosure of the antenna preamplifier node. The antenna preamplifier node is electrically isolated by RF attenuation material. An antenna of the antenna preamplifier node is a low gain antenna. The antenna preamplifier node reads a coded radio frequency signal of a personal detector unit inserted into an enclosure and rejects signals of other various personal detector units in the vicinity.

Transition radiation detectors

Abstract: The use of transition radiation (TR) as a means of identifying high energy particles has now become a subject of intensive experimental investigations and applications. Our intention is first to study the physics of these phenomena and to describe ways of building detectors which can efficiently identify particles.

Realistic optical homodyne measurements and quasiprobability distributions.

Abstract: The deteriorating effect of low-efficiency detectors in different schemes suitable for a direct measurement of the Q function and in optical homodyne tomography is studied in some detail. It turns out that this effect amounts to smoothing the respective quasiprobability distribution that would be measured with unit-efficiency detectors. Our main result is that those smoothed distributions can be identified with certain s-parametrized quasiprobability distributions. Thus the latter gain direct experimental significance as distributions measurable under realistic experimental conditions.

Method and apparatus for determining an objects position, topography and for imaging

Abstract: Light is supplied via a optical fiber to a probe head. The light exiting the optical fiber is focused to a point by a lens. Reflected light from an object at or near the focal point is reflected back through the lens and then focused to the source optical fiber or a second optical fiber located next the source optical fiber. The return signal is then detected in a detector module. By noting the characteristics of the response curve as the object is moved back and forth relative to the probe head, the position of the object can be determined. By performing this procedure over several points, a detailed topography map can be created. Additionally, the probe head can be scanned at a constant distance from the surface to produce an image of the surface as the response signal varies according to the surface's reflectivity. The microprobe can be used, for example, to find the position of probe tips on a wafer prober, to determine the topography of the surface of the wafer, and to find the position of the wafer edge.

Maximum likelihood frequency detectors for orthogonal multicarrier systems

Abstract: A frequency estimation algorithm for a multicarrier system based on the maximum likelihood principle is derived. A frequency detector structure directly based on this algorithm is proposed, together with a reduced complexity structure having the same performance. Such a detector shows a very small acquisition range due to the particular form of the likelihood functions for a multicarrier sytem. To overcome this limitation, a modified version of the frequency detector is proposed. It has a considerably increased acquisition range together with low augmentation in complexity. >

Radiation responsive surgical instrument

Abstract: A crystal containing detector particularly suited for use in immunoguided surgery capable of detecting gamma emissions present at tumor sites. The instrument utilizes a cadmium-zinc-telluride detector crystal which may be retained within a finger mount positioned over the surgeon's finger. Within this mount there also is incorporated a first preamplification stage designed to accumulate charge signals from the detector as well as to drive a relatively short length of cable to a second preamplification stage located, for example, within a housing at the surgeon's upper arm. The small finger mounted probe may be moved between operative orientations at the underside of the tip of the finger to stand-by orientations at the top of the finger adjacent the knuckles In an additional embodiment, the finger probe incorporates a sodium iodide crystal, the scintillations from which are transmitted via a short length of fiber optic cable to an upper arm mounted housing which contains a photomultiplier tube. Signals from the remote, arm-mounted housing then are transmitted via longer cabling or the like to a control console.

Application of a natural diamond detector for the measurement of relative dose distributions in radiotherapy.

Abstract: The suitability of a natural diamond detector with a special contact system for the measurement of relative dose distributions in selected radiotherapy applications was studied. The performance of the diamond detector was analysed by comparison with measurements using an ionization chamber and a silicon diode detector. The good stability, high response and good spatial resolution of the diamond detector were demonstrated by relative measurements in high-energy photon and electron beams and around the 137Cs source of an afterloading device. The application of the diamond detectors for relative as well as absolute dose measurements of beta ray ophthalmic applicators was also highlighted. It is concluded that the diamond with the special contact system is a suitable detector for relative dose measurements in a wide variety of applications, especially when high response and high spatial resolution are required.

Moveable desktop light controller

Abstract: A device for controlling power to an electrical load. The device has two components: a portable desktop detector unit and a wall-mounted receiver unit. The desktop detector detects the presence of a human in a room and the ambient light level and sends signals to the receiver unit to supply power to or withhold power from an electrical load such as a fluorescent light and to adjust the brightness of the light. Since the detector is portable, it can be positioned and repositioned at different locations in a room to maximize its ability to detect the presence of a human and to sense the level of ambient light in various room locations. Each detector and receiver pair have matching addresses so that a receiver will operate an electrical load only in response to its mated detector, thus allowing multiple devices to be used to control multiple lights without interfering with each other. The device can also operate with a third component that acts as a master key and controls the maximum brightness, at which lights may be operated.

Optical fiber interconnection apparatus and methods

Abstract: A substantially parallel array of printed wiring boards (11A-E) each support a light source element (13A-E) and a light detector element (14A-E). Each light source element is connected to all of the light detector elements of the other printed wiring boards by optical fibers (18) supported in arcuate grooves (16) of an optical backplane member (12). Each source element is also connected to a source terminal (26) and each detector element is connected to a detector terminal (27), which permit bypass interconnections between selective source elements and detector elements. In another embodiment (FIGS. 10 and 11) a broad surface (33) of the optical backplane member (32) contacts edges of the printed wiring boards (31A-C).

Method and apparatus for non-invasive measurement of blood sugar level

Abstract: To intensity-modulate laser light periodically wavelength-modulated by and emitted from a wavelength-variable semiconductor laser 11. To separate the laser light into optical paths 13a, 13b with a beam splitter 14 to irradiate an examined location 17 for assessing blood sugar through path 13a. To detect the intensity of transmitted or reflected light from examined location 17 with a first detector 21 and the intensity of laser light passing through path 13b with a second detector 22 to detect the ratio of the former intensity to the latter intensity with a logarithmic ratio amplifier 25. To detect the rate of change in the ratio with respect to the change in wavelength of the wavelength modulation with a lock-in amplifier 26 to obtain a derivative spectral signal of the absorption spectrum of glucose. An arithmetic processor 27 detects blood sugar in the examined location from the derivative spectrum.