Showing papers on "High dynamic range published in 1996"

Method and apparatus of high dynamic range image sensor with individual pixel reset

Abstract: A wide dynamic range image sensor provides individual pixel reset to vary the integration time of individual pixels. The integration time of each pixel is controlled by column and row reset control signals which activate a logical reset transistor only when both signals coincide for a given pixel.

Multi-mode radar system having real-time ultra high resolution synthetic aperture radar (SAR) capability

Abstract: One meter and one foot resolution is achieved in a multi-mode SAR radar system in real time by wide bandwidth RF signal generation, precision motion compensation, polar reformatting, autofocusing and high dynamic range image processing. An exciter/receiver of this system includes means for providing wideband RF waveform generation and down-conversion, while a programmable digital signal processor includes improvements in software for implementing the functions of motion compensation including the presuming of data, polar reformatting, autofocusing and image processing.

An image sensor with high dynamic range linear output

Abstract: Designs and operational methods to increase the dynamic range of image sensors (200) and APS devices (300) in particular by achieving more than one integration times for each pixel (302) thereof. An APS system (200) with more than one column-parallel signal chains (204, 206) for readout are described for maintaining a high frame rate in readout. Each active pixel (302) is sampled for multiple times during a single frame readout, thus resulting in multiple integration times. The operation methods can also be used to obtain multiple integration times for each pixel (302) with an APS design having a single column-parallel signal chain (104) for readout. Furthermore, analog-to-digital conversion of high speed and high resolution can be implemented.

Four-quadrant class AB CMOS current multiplier

Abstract: A four-quadrant class AB CMOS current-multiplier is presented. Wide input range, high dynamic range, high cutoff frequency, good linearity and low consumption are the features of the presented technique. A nonlinearity error of 1.1 % with a small-signal bandwidth of 66 MHz for a quiescent current of 25 µA and a supply voltage of 3.3 V in a 0.5 µm technology are obtained.

Multilayer anode with crossed serpentine delay lines for high spatial resolution readout of microchannel plate detectors

Abstract: We have designed, built, and tested the first successful imaging microchannel plate (MCP) detector that uses two crossed, printed circuit, serpentine delay lines, one stacked above the other in a three‐dimensional architecture. Laser ablation machining is used to cut slots that allow delay lines in two layers parallel to the MCP to sample and read out x and y image positions. Previous readouts that use delay line timing to read out both dimensions of an image employ a wire‐wound anode. The goal of this readout is to provide as many picture elements (pixels) as possible in two dimensions, with high temporal resolution, high throughput, high dynamic range, and good spatial linearity. This detector achieves this goal with off‐the‐shelf electronics and is robust for space flight. The full width half maximum (FWHM) spatial resolution is 32 μm at the center of the detector and is typically <35 μm throughout the detector. The rms linearity is 40 μm in each readout dimension, after applying only radial corrections for fringe field effects near the perimeter, and <20 μm after applying additional simple (one‐dimensional) corrections. Throughput for 10% coincidence loss is limited by the measured baseline settling time to 4×105 s−1, but the current electronics limit is 1.1×105 s−1. The walk characteristics of the detector are described. We discuss fabrication techniques, application to space‐based astronomy use, and design modifications to improve performance.

Spectroscopic optical coherence tomography

Abstract: Summary form only given. Implementations of OCT, which take advantage of the spectral bandwidth of low coherence sources for tissue spectroscopy, have not yet been reported. We describe a novel technique for depth-resolved coherent backscatter spectroscopy, which is an extension of OCT technology. Our system incorporates an OCT scanner illuminated by a superluminescent diode (SLD) at 1.3-/spl mu/m center wavelength. In the low-coherence interferometer, a scanning reference mirror generates the temporal cross-correlation function of light reflected from the reference mirror, and that backscattered from the sample arm target. A separate helium-neon interferometer is utilized for digital correction of artifacts in the low-coherence interferometer output due to nonlinearities in the reference arm retroreflector stage velocity. The low-coherence interferometric signal is digitally demodulated and filtered to obtain the complete complex envelope of the interferometric signal, which is required for the spectroscopic technique. Using this system, low-coherence interferograms with accurate sampling intervals and high dynamic range (>98 dB) are acquired.

A novel quasi-optical monopulse-tracking system for millimeter-wave application

Abstract: A novel, low-loss, polarization-independent quasi-optical monopulse comparator (QOMC) has been developed as an alternative to the commonly used waveguide comparator It has been implemented as an experimental model with an aperture of 23/spl times/23 wavelengths for a 140-GHz monopulse tracking antenna fed by a beam waveguide The QOMC consists of two cascaded identical stages (sections) to perform azimuth and elevation angle measurements Each comparator stage is composed of only two plane-parallel reflectors and a low-loss quasi-optical 3-dB beam splitter symmetrically positioned in between them Extensive model calculations of a single QOMC stage with square aperture dimensions between 10 and 25 wavelengths, and experimental investigations of the realized two-stage QOMC in a beam-waveguide field were performed Owing to its sufficient high dynamic range at bandwidths of up to about 300 MHz, and particularly, its low absorptive loss of less than 35% per stage at 140 GHz, this QOMC is suited ideally for millimeter-wave applications

A new CMOS readout circuit design for the IR FPA with adaptive gain control and current-mode background suppression

Abstract: A new CMOS current readout structure for the infrared (IR) focal-plane-array (FPA), called the buffered gate modulation input (BGMI) circuit is proposed and analyzed. The new readout circuit can achieve a high charge sensitivity with the adaptive current gain and has a good immunity from threshold-voltage variations. Moreover, the readout dynamic range is dramatically increased by using a threshold-voltage independent current-mode background suppression technique. The BGMI circuit with current-mode background suppression has been designed and simulated it has been shown that high injection efficiency, high charge sensitivity, high dynamic range, large storage capacity, and low noise performance are achieved in a 50/spl times/50 um/sup 2/ pixel size. These advantageous traits make the BGMI circuit suitable for the applications with a large background current range.

Strain sensors having ultra-high dynamic range

Abstract: A sensor configuration increases the usefulness of Fiber Optic Displacement Sensors by mounting them on an elastomer substrate. The sensor configuration can also be used for most other sensors. The elastomer substrate is used to pre-mount the sensors, making field installation easier, increasing the range of the sensors, allowing strain sensors to measure compression and elongation, and providing a mechanism whereby the sensors can be protected from failure due to excess strain. The sensing range of the sensor is increased by employing an elastomer substrate to which only a portion provides mounting for the fiber, thereby significantly enhancing the dynamic range of the sensor.

A 35-Series Superconducting Quantum Interference Device Array for High-Dynamic-Range Magnetic Measurements

Abstract: A 35-Series Superconducting Quantum Interference Device Array has been developed for a magnetometer with a high dynamic range. The coherence of each SQUID was observed in a double-shielded tube made of cryoperm and lead; a maximum voltage swing of 2 mV and flux noise of 0.6 µΦ0/√ Hz were obtained. The nonuniform inductance of the SQUIDs in the array, which causes Φ–V curve modulation, is decreased by using dummy SQUIDs at each end of the array. A gradiometer for biomagnetic measurement was constructed using a 35-SQUID array and a 10×10-mm planar pick-up coil. A magnetic-field sensitivity of 5.4 fT/√ Hz, a maximum slew rate of 1.9 mT/s, and a maximum feedback amplitude of ±2.23 µ T were achieved by using a direct-coupled flux-locked-loop circuit. The dynamic range of the magnetometer input field was ±4.13×108 √ Hz.

An ultra low-power high dynamic range direct conversion receiver

Abstract: This paper shows a direct conversion receiver intended for paging applications optimized to accomplish low power consumption and high dynamic range. The main features of the receiver are: high sensitivity, small size, very low power consumption and good dynamic range. Comparisons between this direct-conversion receiver and a equivalent superheterodyne one are reported also.

Characterization measurements of the wideband infrared scene projector resistor array

Abstract: Kinetic energy weapon (KEW) programs under the Ballistic Missile Defense Office (BMDO) need high fidelity, fast framing infrared (IR) imaging seekers. As imaging sensors have matured to support BMDO, the complexity of functions assigned to the KEW weapon systems has amplified the necessity for robust hardware-in-the-loop (HWIL) simulation facilities to reduce program risk. Tactical weapon systems are also turning to imaging focal plane array (FPA) seekers. They too require more sophisticated HWIL testing. The IR projector, an integral component of a HWIL simulation, must reproduce the real world with enough fidelity that the unit-under-tests's (UUT) software will respond to the projected scenario of images as though it were viewing the real world. The MOSFET resistor array IR scene projector shows great promise in cryogenic vacuum chamber as well as room temperature testing. Under the wideband infrared scene projector (WISP) program, an enhanced version of the resistor array is currently under development. When the WISP system is delivered, the projector will consist of a 512 by 512 baseline array with the center 128 by 128 resistors having a higher output capability. For the development stage of the program, 512 by 512 prototype baseline and 128 by 128 prototype high dynamic range (HDR) arrays have been fabricated separately. Characterization measurements to include: spectral output, dynamic range capability, apparent temperature, rise time, fall time, cross talk, and current consumption have been accomplished on the prototype baseline and HDR arrays at the Kinetic Kill Vehicle Hardware-in-the-Loop Simulator (KHILS) Facility and the Guided Weapons Evaluation Facility (GWEF). Results from the measurements show the HDR array dynamic range is an order of magnitude greater than its predecessor. Other parameters such as droop, rise time, etc., either meet or are close to meeting system specifications. The final design of the arrays is currently in progress based on these results.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Optical trans-impedance amplifier of high dynamic range

Abstract: PROBLEM TO BE SOLVED: To provide a preamplifier that can extend a dynamic range without sacrificing sensitivity SOLUTION: In a preamplifier for current generated by a light detection diode 100, a current is combined with a base of an NPN transistor 102 connected as the common emitter part and at the same time a feedback resistance 120 is connected to the base as a buffer amplifier for constructing a standard transimpedance constitution By integrating an output from this buffer amplifier, a control loop detects a signal level Since, under a condition of strong signal detection, an MOSFET 119 parallel to the feedback resistance 120 reduces the transimpedance by means of the control loop, it can increase signal processing ability of the preamplifier This control loop is also connected to the second MOSFET 105 parallel to a corrector load resister 103 of the NPN transistor and reduces a valid corrector load impedance at the strong signal level Moreover, in order to increase an emitter circuit resistance part of the common amplifier part directed toward the strong signal level, the third MOSFET 106 provided in parallel with an emitter resistance 104 of the NPN responds to a signal level

Fabry-Perot laser high linearity analog optical links

Abstract: High dynamic range analog optical links are demonstrated using a variety of Fabry-Perot lasers, including commercial and custom devices All of the devices demonstrate a dynamic range and noise figure close to that of an analog DFB laser for short (<2 km) links The best devices have performance which rivals that of a typical DFB laser

Linearized modulators for analog photonic links

Abstract: The potential applications of high dynamic range analog RF photonic links include antenna remoting, photonic-coupled phased-array antennas, and cable-television transmission This paper compares the results obtained with a number of different electro-optic modulator types and link configurations assuming an ideal velocity-matched modulator The degrading effects of velocity mismatching are also presented for some of the modulators studied

Current scaling technique for high dynamic range switched-current delta-sigma modulators

Abstract: Thermal noise at the input usually imposes a fundamental limitation on the dynamic range of switched-current (SI) delta-sigma modulators. The authors present a technique for increasing the dynamic range of SI modulators without a drastic increase in power dissipation and chip area.

Encoder and decoder

Abstract: PURPOSE: To give a wide-band and high dynamic range by providing an encoder with an encoding means which transmits an input acoustic signal after encoding it by a sampling frequency which is a specific number or more times as high as the audible band and providing a decoder with a decoding means which takes out and reproduces a signal of a prescribed band. CONSTITUTION: The input acoustic signal is encoded by >=4-fold sampling frequency of the audible band, and the dynamic range of the audible band is extended by ΔΣ modulation if necessary. That is, a ΔΣ modulator 2 is provided which is operated by >=4-fold sampling frequency of the audible band and has >=8-bit output and has the shaping characteristic varied by mode control and consists of an adder 4, a local quantizer 5, etc., and an inputted digital signal is encoded by the ΔΣ modulator 2 and is transmitted together with the mode control ID. At the time of decoding, the cut-off frequency of a low pass filter is controlled in accordance with the characteristic of the ΔΣ modulator 2 based on the mode control ID by a digital filter.

Measurement of acoustic parameters by means of pseudorandom signals

Abstract: In this paper, a portable acoustic parameter analyser is presented. Based on pseudorandom sequences, the analyser obtains the impulse response of a linear system using the cross-correlation between the pseudorandom input sequence and the output signal of the system to be measured. The deterministic nature of the pseudorandom sequence allows one to achieve high dynamic range measurements with very low amplitude signals. Once the impulse response signal, h(t), is obtained, the acoustic parameters are calculated. The main advantage of the analyser relies on its ability to work under noisy situations, something vital in acoustics because the acoustic properties of a room constantly alters. Measurements can be made without interfering room activities such as plays or music concerts.

Intermodulation in channelized digital ESM receivers

Abstract: : This thesis investigates intermodulation distortion generated by analog-to-digital converters (ADCs) in a channelized digital ESM receiver when processing multiple signals simultaneously. The spurious free dynamic range (SFDR) associated with this distortion is discussed. Two methods for increasing the spurious free dynamic range are evaluated. First, by adding a small amount of Gaussian noise to the input of the receiver, the intermodulation distortion is found to be reduced significantly. Second, by using a narrow bandwidth sub-Nyquist sampling rate with high dynamic range ADCs it is possible to increase the spurious free dynamic range of the digital receiver. The first method is a simple approach but the ability to increase the SFDR is limited. The second method is more effective but requires greater computation and complex receiver design.

Enhancement and quality control of GOES images

Abstract: The new generation of Geostationary Operational Environmental Satellites (GOES) have an imager instrument with five multispectral bands of high spatial resolution,and very high dynamic range radiance measurements with 10-bit precision. A wide variety of environmental processes can be observed at unprecedented time scales using the new imager instrument. Quality assurance and feedback to the GOES project office is performed using rapid animation at high magnification, examining differences between successive frames, and applying radiometric and geometric correction algorithms. Missing or corrupted scanline data occur unpredictably due to noise in the ground based receiving system. Smooth high resolution noise-free animations can be recovered using automatic techniques even from scanline scratches affecting more than 25 percent of the dataset. Radiometric correction using the local solar zenith angle was applied to the visible channel to compensate for time- of-day illumination variations to produce gain-compensated movies that appear well-lit from dawn to dusk and extend the interval of useful image observations by more than two hours. A time series of brightness histograms displays some subtle quality control problems in the GOES channels related to rebinning of the radiance measurements. The human visual system is sensitive to only about half of the measured 10- bit dynamic range in intensity variations, at a given point in a monochrome image. In order to effectively use the additional bits of precision and handle the high data rate, new enhancement techniques and visualization tools were developed. We have implemented interactive image enhancement techniques to selectively emphasize different subranges of the 10-bits of intensity levels. Improving navigational accuracy using registration techniques and geometric correction of scanline interleaving errors is a more difficult problem that is currently being investigated.

High dynamic range, low-noise floating-gate photosensor

Abstract: The floating-gate photosensor is a new method for detecting wideband photosignals that has high dynamic range and low noise. Low noise is achieved because the transduction from a photocurrent to a voltage uses capacitive coupling rather than the use of a load resistor. The floating-gate photosensor has demonstrated a noise equivalent power of 10 nW, a rise time of 50 nS, and a dynamic range of 10/sup 5/:1. The detector is AC coupled and has a square-root compressing transfer function for large photosignals.

A chirp-OTDR using an AWG compressor

Abstract: We describe a chirp optical time-domain reflectometer (chirp-OTDR) that is used to enlarge dynamic range Use of an arrayed-waveguide grating (AWG) compressor confirms its advantages in the field of high dynamic range measurements

A single Chip Implementation for Fast Convolution of Long Sequences

Abstract: Usually, long convolutions are computed by programmable DSP boards using long FFTs. Typical operational requirements such as minimum power dissipation, minimum volume and high dynamic range/accuracy, make this solution often inefficient and even unacceptable. In this paper we present a single chip floating point solution for large convolution problems. It is based on an algorithm that maps long convolutions on short FFTs without affecting the optimum complexity O(N log N). The chip contains a highly parallelized short length FFT core enabling us to compute an FFT completely, without external FFT working memory intervention. The FFT core contains a set of fully parallelized radix 2 processing cores based on a hybrid floating point data format. The proposed implementation of the arithmetic blocks is the result of a trade off between maximum accuracy, maximum dynamic range and minimum chip area. The convolution chip will be used in a realtime Synthetic Aperture Radar (SAR) imaging processor developed for on-board aircraft or satellite processing.