Showing papers on "Dynamic range published in 1984"

Fiber-optic lattice signal processing

Abstract: We discuss the implementation of fiber-optic lattice structures incorporating single-mode fibers and directional couplers. These fiber structures can be used to perform various high-speed time-domain and frequency-domain functions such as matrix operations and frequency filtering. In this paper we mainly consider systems in which the signals (optical intensities) and coupling coefficients are nonnegative quantities; these systems fit well in the theory of positive systems. We use this theory to conclude, for example, that for such systems the pole of the system transfer function with the largest magnitude is simple and positive-valued (in the Z-plane), and that the magnitude of the frequency response can nowhere exceed its value at the origin. We also discuss the effects of various noise phenomena on the performance of fiber-optic signal processors, particularly considering the effects of laser source phase fluctuations. Experimental results are presented showing that the dynamic range of the fiber systems, discussed in this paper, is limited, not by the laser source intensity noise or shot noise, but by the laser phase-induced intensity noise. Mathematical analyses of lattice structures as well as additional applications are also presented.

Optimal design of state - space digital filters by simultaneous minimization of sensitivity and roundoff noise

Abstract: The relation between a newly defined sensitivity measure and the noise power gain for scaled filters is given. By means of this relation it is shown that the necessary and sufficient condition to minimize the noise power gain is to minimize the sensitivity measure for unsealed filters. It is shown that the minimization of this sensitivity measure can be carried out without taking into account the dynamic range constraint. A procedure for the simultaneous minimization of the sensitivity measure and the noise power gain is also given.

A novel wide dynamic range silicon photodetector and linear imaging array

Abstract: A silicon photodetector structure utilizing the MOSFET subthreshold effect is discussed. This photodetector, which can be integrated on the same chip with MOSFET circuits or CCDs, provides an analog voltage signal over a wide dynamic range. Photodetector and arrays showed, in the visible spectrum an incoming radiation-detection light-intensity dynamic range of greater than 10/SUP 7/. In addition, the photodetector device was used to realize CCD and self-scanned MOSFET linear arrays. The theory of the new photodetector device and its use in forming linear imaging arrays are discussed. Experimental results are presented.

Dynamic range and asymmetry of the auditory filter

Abstract: This experiment was designed to measure the shape and asymmetry of the auditory filter over a wider dynamic range than has been measured previously. Thresholds were measured for 2-kHz sinusoidal signals in the presence of two 800-Hz-wide noise bands, one above and one below the signal frequency. The spectrum level of the noise was 45 dB (re: 20 muPa), and the noise bands were placed both symmetrically and asymmetrically about the signal frequency. The deviation of the signal frequency from the nearer edge of each noise band varied from 0 to 0.8 times the signal frequency. Each ear of six subjects was tested, and the subjects' ages ranged from 22 to 74 years. The auditory filters derived from the data were somewhat asymmetric, with steeper slopes on the high-frequency side; the degree of asymmetry varied across subjects. The asymmetry could be characterized as a uniform stretching of the (linear) frequency scale on one side of the filter. The dynamic range of the auditory filter exceeded 60 dB in the younger listeners, but the dynamic range and sharpness of the filter tended to decrease with increasing age.

A novel wide dynamic range silicon photodetector and linear imaging array

Abstract: A novel silicon solid-state photodetector structure utilizing the MOSFET subthreshold effect was conceived, developed, fabricated, and experimental results were obtained. This photodetector device, which can be integrated on the same chip with MOSFET circuits or CCD's, provides an analog voltage signal over a wide dynamic range. Fabricated photodetector devices and arrays showed experimentally, in the visible spectrum, an incoming radiation detection light intensity dynamic range of greater than 107. In addition, the novel photodetector device was used to realize CCD and self-scanned MOSFET linear arrays. In this paper, we describe in detail the theory of the new photodetector device and its applications to form linear imaging arrays. Finally, we present experimental results obtained on developed and fabricated devices and arrays.

Interline CCD image sensor with an antiblooming structure

Abstract: A ⅔-in 384 (H) × 490 (V) element interline CCD image sensor with a new antiblooming structure was developed. Blooming was suppressed without sacrificing photosensitivity and dynamic range by means of a vertical overflow drain positioned under (rather than beside) a photodiode. For 10-percent vertical height illumination the smear signal was reduced to 0.05 percent of the illumination signal. Well-balanced performance, namely, large dynamic range (72 dB), low random noise (65 rms noise electrons per charge packet), high-contrast transfer functions for horizontal and vertical directions, and a spectral response similar to the luminous efficiency curve were obtained under moderate operating conditions.

Image pickup means

Abstract: Image pickup means which incorporate means for logarithmically converting the incident light intensity, for controlling the light intensity issued with a plurality of varied intensities, and performing electrically the controlling of throttling of light intensity and dynamic range by receiving the light from the controlling means on pickup elements, adding the converted electrical signals, corresponding to the light intensity received on the pickup elements, through adder means to provide electrical signals having a magnified dynamic range and processing these electrical signals through subsequent circuits.

Parallel‐recording systems for electron energy loss spectroscopy (EELS)

Abstract: The present report paper deals with the use of a photodiode array for recording electron energy loss spectra in a transmission electron microscope. Important properties of the array are outlined, together with a description of the circuitry needed for interfacing the output to a multichannel analyser. In the direct-exposure mode, the device can easily detect a single (80 or 100 keV) electron, allowing inner-shell energy losses between 200 eV and 2000 eV to be recorded in about 10 seconds. By signal averaging a large number of readouts, a dynamic range of at least 105 is possible. Irradiation damage to the array can be controlled by cooling the array and by various anealing procedures. Sensitivity and DQE are lower, but the dynamic range is higher in the indirect mode, where a fluorescent screen is used to convert the electrons into visible photons, which are then imaged onto the diodes. The choice of screen material and of optical coupling to the array are discussed. Several spectral artifacts are described, together with spectrum-processing techniques designed to remove them.

Digital Single Sideband Detection For Interferometric Sensors

Abstract: Digital single sideband detection with time discrete phase modulation for interferometric sensors utilizes integrated-optic components, and a direct digital processing. A dynamic range of 57 dB, and a maximum phase error of 0.07° are achieved with 10 bit converters.

Apparatus and method to increase dynamic range of digital measurements

Abstract: Disclosed is a method for overcoming one of the limiting factors in applying digital techniques to measuring analog signals over a wide dynamic range, namely, the uncertainty introduced into the measurement by noise and A/D conversion, particularly at low signal levels. A central feature of the technique is the filtering of the signal with a variable time constant digital filter, the time constant being a function of the measured signal in such way as to increase the effective resolution of small signals at the expense of an increased transient delay. For large signals, the time constant is reduced so that adequate transient response is provided when it is most needed and when there is already adequate resolution.

Large dynamic range multiplier for a maximal-ratio diversity combiner

Abstract: An improved large dynamic range multiplier is disclosed that provides substantially ideal multiplication for signals within a maximal-ratio predetection diversity combiner. Linear product multiplication is necessary in the second mixing stage of the maximal-ratio predetection diverstiy combiner, where it is essential that the mixer product signal be proportional to the product of its input signals, which each have a dynamic range in excess of 40 db. The multiplier, which in the preferred embodiment of the present invention is a field-effect-transistor device, provides a product signal that has a linear dynamic range approaching 130 db, far in excess of the 80 db necessary to accommodate typical input signals having a 40 db dynamic range.

Wide dynamic range video camera

Abstract: Atetevision camera apparatus(10) wherein bright objects are attenuated to fit within the dynamic range of the system while dim objects are not receives linearly polarized lightfrom an object scene (12), the light being passed by a beamsplitter (20) and focused on the output plane of a liquid crystal light valve (16) oriented such that, with no excitation from a cathode ray tube (22), all light is rotates 90° and focused on the input plane of a video sensor (28). The light is then converted to an electrical signal, which is amplified and used to excite the CRT. The resulting image is collected and focused onto the light valve, which rotates the polarization vector of each light increment to an extent proportional to the light intensity from the CRT. The overall effect is to selectively attenuate the image pattern focused on the sensor.

Method and apparatus for transmitting digital signal

Abstract: It has been observed that the S/N ratio of differential-mode PCM and summation-mode PCM with respect to quantization noise is improved at low frequencies and high frequencies, respectively, and consequently the dynamic range thereof is increased. An input signal is divided into blocks of a predetermined number of bits, and, for each block, the one of the general-mode PCM, differential-mode PCM, and summation-mode PCM mode is selected in which adaptive encoding is most efficient, and consequently the quantization noise is smallest, and the input signal data in the mode selected for each block is transmitted together with a mode signal and an adaptive data signal, etc. It has also been observed that the closer to the main signal, the larger the masking effect on the sense of hearing, so that the S/N ratio in terms of the sense of hearing is improved by changing the noise spectrum during digitization to correspond to the spectrum of the input signal.

Intensified silicon photodiode array detector linearity: application to coherent anti-Stokes Raman spectroscopy

Abstract: The linearity of an intensified silicon photodiode array multichannel detector is studied with coherent anti-Stokes Raman and other similar signals. Studies with diffuse and focused (spherically and cylindrically) signals resolved apparent saturation problems which limit the dynamic range of the detector. In addition, it has been shown that there is no short-range wavelength (473-532-nm) dependence on this saturation. Theoretical explanations for these phenomena are also included.

EXCLUSIVE OR processing (binary image subtraction) using thick Fourier holograms.

Abstract: Theoretical and experimental results are presented for parallel EXCLUSIVE OR processing using thick Fourier holograms. The data pages used contained 1024 bits in a 32 × 32 format. A holographically stored data page is reconstructed together with an input data page that is imaged through the system. The amplitudes of the two wave fronts are adjusted to be equal, and their relative phase is adjusted to be 180°, thus producing the bit-by-bit EXCLUSIVE OR operation between the pages. Using an expanded reference beam for the geometrical configuration treated, it is calculated that the average dynamic range between a 0 and a 1 in the output power would be 17.4 dB. Experimentally, it is shown that excellent EXCLUSIVE OR results are obtainable. Photographs of these results are presented. An average dynamic range of 7.7 dB was measured, the decrease from the calculated value being primarily due to noise in the video method of detection used in the measurements. The probabilities of miss and false alarm and the total probability of error were also measured. The use of a small diameter reference beam, necessary in some applications, causes a large mismatch in the shapes of the two wave fronts, thus degrading the EXCLUSIVE OR results. It is shown theoretically and experimentally that using an aperture at the recording material produces partial compensation of the wave fronts, thus improving the EXCLUSIVE OR results.

Improved-dynamic-range single-mode OTDR at 1.3 μm

Abstract: A high-performance single-mode optical time-domain reflector (OTDR) incorporating a new low-noise receiver design utilising a PIN diode detector and a transimpedance amplifier is described. With a 1.3 μm laser diode source a dynamic range of 30 dB one way is achieved, and using an Nd: YAG laser source the dynamic range is 41 dB one way.

The Liquid Crystal-Based Visible To IR Dynamic Image Converter (VIDIC)

Abstract: The Liquid Crystal -Based Visible to IR Dynamic Image Converter (VIDIC)U. Efron, S.T. Wu, P.O. Braatz, J. Grinberg, L.D. HessA.M. Lackner, J.D. Margerum and F.G. YamagishiHughes Research Laboratories3011 Malibu Canyon RoadMalibu, California 90265AbstractThe development of a liquid crystal -based visible -to -IR dynamic image converter isdescribed. Liquid crystal studies in the IR, as well as the structure, operation andpreliminary performance results of a 10.6 um VIDIC are reported.IntroductionExisting infrared simulation systems suffer from low resolution (caused by thermalspread in the image plane), slow response (caused by a large thermal time constant), andlimited dynamic range capabilities (limited by the conflicts between high resolution anddynamic range of a thermal -based target simulation system.) Because of these limitations anew simulation system is needed which can provide a complex, fast changing IR scene with ahigh degree of dynamic range and resolution, and is capable of real -time interaction with acomputer image generation (CIG) system.We believe that one such solution is offered by the liquid crystal light valve (LCLV) -based VIDIC. This device is based on the liquid crystal and semiconductor technologieswhich were developed at Hughes Research Laboratories during the past decade.1,2 The twomain advantages of the LCLV -based VIDIC over existing systems such as the Bly cell are:(1) the generation of a non -thermal image at the focal (target) plane, and (2) theseparation of the output source from the input image. Optical modulation of the IR beamcaused by polarization- rotation effects frees the LCLV -VIDIC system from the severe trade-offs associated with a thermal target projection system. Separation of the output imagefrom the input source allows a compact, low power input image source (e.g., a CRT) to beused without sacrificing the high IR power required at the output. Thus, much higherperformance in resolution, dynamic range and speed is expected from a LCLV -VIDIC system,with the additional advantages of high temperature simulation and compatibility with a CIG

Monolithic Wideband Parallel Channel Detector Array

Abstract: A parallel channel detector array was developed to function in an acousto-optical signal processor. Each channel is independent of all the other channels with a photodetector pitch of 254 micrometers. The design provided for a 50 db dynamic range for a -54 dbm to -4 dbm 0.85 micrometer optical power input with a logarithmic output transfer characteristic. A monolithic N-MOS process with 3 micrometer design rules was utilized to fabricate the detector array.

Signal correlation using a one-dimensional electroabsorptive CCD spatial light modulator

Abstract: Electrically addressed spatial light modulation (SLM) may be carried out in a GaAs charge-coupled device (CCD) by charge-transfer control of the electroabsorption in the individual storage wells. One-dimensional modulator arrays may be utilized in both space-integrating and time-integrating correlators operated as incoherent optical processors. In the space-integrating case, one SLM controlled by the input signal is operated in cascade with a second SLM controlled by a reference waveform. This arrangement yields a single-detector output which is the correlation as a function of time. In the time-integrating correlator, the input signal is carried by the light source while a single SLM with a traveling reference wave controls the output intensity to a detector array. The modulator arrays may be operated with the light at normal incidence to a CCD with transparent gates or in a guided-wave mode, where the light propagates beneath the gate electrodes and parallel to the surface. The calculated dynamic range is greater for the guided-wave case because of the greater depth of modulation, although the fabrication and optical coupling are more critical. Space-integrating correlator performance is limited by "bleaching" or well-filling by the modulated light and predicted dynamic ranges are 20 dB for normal-incidence operation and 40 dB for the guided-wave mode. In the time-integrating correlator, saturation of the detector array is limiting, but the 100-percent modulation available in the input optical source yields 35-dB dynamic range for normal-incidence and 55 dB for guided-wave operation.

Image reader for X-ray film or the like having a detection system with an expanded dynamic range

Abstract: An image reader having a high sensitive detection system for detecting a variation in a first light quantity to generate a first output, a low sensitive detection system for detecting a variation in a second light quantity to generate a second output where the second light quantity is greater than the said first light quantity, and a signal composing circuit for receiving the outputs of the high and low sensitive detection systems, each of the detection systems being so disposed as to detect simultaneously or substantially simultaneously a ray bundle from a picture element of a picture, and the output of the signal composing circuit being (a) the output of the high sensitive detection system when the received light quantity is smaller than a threshold light quantity which can be detected with substantially the same degree of accuracy by both the detection systems or (b) the sum of (i) the output of the low sensitive detection system and (ii) the difference between the outputs of the detection systems at the threshold light quantity whereby a time-serial output of wide dynamic range is obtained.

Expanding the dynamic range of x-ray videodensitometry using ordinary image digitizing devices.

Abstract: While x-ray images on film have a wide dynamic range of up to three optical density units (o.d.) or 1:1000 variation in transparency, many ordinary digitizing video systems have a limited dynamic range of ~1.4 o.d. in actual practice. The digital images thus either lack details in the dark areas or are saturated and bloom in the bright areas and have a poor contrast ratio. We present here an object-dependent digital image processing method to overcome this drawback by appropriately selecting and correcting pixels drawn from two images acquired from the same radiograph at different light levels. A calibrated gray scale is used to compensate for the nonlinearity of the video system and derive the true optical density for each pixel. The method should find applications in digital mammography, teleradiology, archiving of radiographs, and videodensitometry in general.

Fast light interconnected processor

Abstract: A fast light interconnected processor device for image processing includes an image sensor for producing a line scan signal, a one-dimensional line display for producing a light having an intensity representative of the scan signal and an array of light detectors for producing a two-dimensional convolution of the image with a blurring function performed simultaneously with the scanning of the image scene The image sensor is, for example, a thermal imager (forward looking infrared system) which outputs electrical signals representative of thermal energy emanating from a scene The one-dimensional line display is, for example, a one-dimensional array of light emitting diodes which converts the electrical signals of the thermal image to a light image And the array of light detectors is, for example, an array of charge transfer devices positioned to receive the light image and produce the two-dimensional convolution of the image with a blurring function performed simultaneously with the scanning of the image scene for a contrast map A zero crossing detector may be connected to the light detector array for producing an outline of the image Also, the one-dimensional line display may be positioned as to the detector array to provide an in-focus image for an automatic low frequency gain leveling device for controlling the incoming signal dynamic range to match the display dynamic range

Fiber Optic Gyro With Digital Data Processing

Abstract: Fiber optic gyros make use of the Sagnac-effect for rotation rate measurement. Two counterpropagating light beams travelling through a coil with length L and diameter D experience a phase shift 2ΔΦ which is given by (1) 2ΔΦ 2LD Ω λ= wavelength c = velocity of light Ω = angular velocity This phase shift can be detected with a 'phase-nulling scheme' or by direct detection /1/. The direct detection has the advantage of an uncomplicated optical set-up (Fig. 1, /2/), but the signal detection raises some problems. By using an analogue system the linearity and the dynamic range are subject to severe limitations. To overcome these problems we use a digital signal detection scheme.© (1984) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A Spectral Analysis Technique in Ultrasound Transducer Characterization

Abstract: This paper briefly outlines a spectral analysis procedure for qualitative characterization of ultrasound transducers and presents applications of the procedure for the assessment of acoustic parameters. The parameters include the transmitting and receiving frequency response, directivity pattern and effective aperture of different shape piezoelectric tranceivers. The advantages and fundamental limitations of the spectral analysis technique are discussed in terms of frequency range, signal to noise ratio and dynamic range. Experimental data are presented which show that the technique is extremely useful in transducer performance evaluation as a continuous function of frequency. Future applications of the technique, including complex, i.e. both amplitude and phase, characterization of ultrasound piezoelectric transducers, are also pointed out.

Photoelectric switch with limit setting means to prevent disablement when the amplifier is saturated

Abstract: There is provided a photoelectric switch in which a beam reflected by an object to be detected is received in a trigonometric manner so that any failure in the distance measurement of the object can be prevented with employment of ordinary amplification circuit for received-light signals without enlarging the figure of the dynamic range of the circuit. In the switch, a circuit for comparing the ratio of the received-light signals to a predetermined operational level includes means for setting the nearest limit point for a set range of a detecting area to be farther than an intersection of the projected light beam with a line connecting centers of light-receiving lens and received-light detecting element so that the detection of the object can be made even when the dynamic range of the amplification circuit is saturated, whereby the presence of the object in the detecting area can be always discriminated even upon the dynamic range saturation of the amplification circuit.

Radar sensitivity and resolution in presence of range sidelobe reducing networks designed using linear programming

Abstract: Binary phase-coded waveforms are widely used in modern radar systems. In linear receivers the sidelobes present at the output of the compression filter cause a reduction of the useful dynamic range. Many procedures have been developed to reduce the sidelobes based on a compensation of their Fourier spectra or on a design of an optimum single mismatched filter. The present paper uses linear programming technique to define an optimum sidelobe reducing network which introduces small mismatching losses when cascaded to a matched filter. The influence of quantization in a digital implementation is evaluated.

Analog fiber gyro with extended linear range

Abstract: A gyroscope system for obtaining an extended linear dynamic range for platform rotation rate measurements comprising a first fiber optic gyroscope with a first optical fiber coil described by a first quantity L 1 R 1 /λ 1 where L 1 is the length of the first optical fiber coil, R 1 is the radius of the first fiber coil, and λ 1 is the light source wavelength, this first quantity being chosen to provide a linear output for a first range of small rotation rates of the platform; a second fiber optic gyroscope with a second optical fiber coil described by a second quantity L 2 R 2 /λ 2 with this second quantity being chosen to provide a linear output for a second range of large rotation rates of the platform, with this second range partially overlapping the first range; voltage controlled oscillators for converting the gyroscope signals to pulse frequency signals; a circuit for determining whether a reference rotation rate within the overlap between the first and second ranges has been reached and generating a control signal in accordance therewith; a pulse counter; and a switch for switching one or the other of the pulse frequency signals to the pulse counter in accordance with the control signal so that a gyroscope which is operating within its linear range is utilized.

Photo diode-array dynamic range for optical signal systems

Abstract: A signal handling system of improved dynamic range wherein a logarithmic circuit is interposed between a photo-diode array and other output circuitry.

Dual-beam interferometer for optical difference measurements

Abstract: A dual-beam interferometer system is presented for performing reflectivity and absorption measurements in the 10–400-cm−1 far-infrared region. This system is designed for cryogenic applications intended for solid state spectroscopy. It consists of two coupled interferometers for optical difference measurements. Dual-beam interferometry is useful when conventional interferograms are digitization noise limited. The method of optical subtraction is presented and compared with methods based on electronic subtraction. The enhancement of dynamic range by this method increases the photometric accuracy (≥0.1%). Possible sources of errors such as offset of simultaneously recorded interferograms are discussed and analytical methods for their correction are presented.