Showing papers on "Dynamic range published in 1998"

A 256/spl times/256 CMOS imaging array with wide dynamic range pixels and column-parallel digital output

Abstract: A 256x256 CMOS active pixel sensor (APS) is described for an automotive stereo-vision system. Illumination may vary over several orders of magnitude, requiring a high dynamic range imager. Dynamic range is increased 20/spl times/ using a special clocking scheme for the lateral overflow gate. This dynamic range enhancement offers improvements over previously-described techniques. It simultaneously provides flexibility, user-adjustability, and digital control, with no reduction of fill factor. On-chip column-parallel cyclic analog-to-digital converters (ADCs) produce digital output at frame rates from 30 to 390 frames/s.

Dynamic spectral power equalization using micro-opto-mechanics

Abstract: We present a voltage-controlled spectral attenuator for gain shaping and power equalization in wavelength division multiplexed single-mode fiber systems. A micro-opto-mechanical modulator array, where electrostatic deflection of a silicon nitride quarter-wave dielectric layer suspended over a silicon substrate creates a column of variable reflectivity mirrors, is packaged using bulk optics and a diffraction grating to disperse the input spectrum across the device and collect the reflected light into a separate output fiber. The packaged component has 9-dB excess loss, 20-dB dynamic range and 10-/spl mu/s response. We demonstrate equalization of the amplified spontaneous emission spectrum from an erbium-doped fiber amplifier and of individual laser signals with 10-dB initial variation to less than 0.5-dB variation over a 24-nm passband-free spectrum.

Photodetector nonlinearity limitations on a high-dynamic range 3 GHz fiber optic link

Abstract: The performance of a dc to 3 GHz externally modulated link utilizing balanced high-power photodetection is presented. Nonlinearity measurements of high power photodiodes show 1 dB compression currents in excess of 55 mA and an output third-order intercept point of +32 to +34 dBm. These high current photodetectors permit the use of high power lasers as external modulator sources for low noise fiber optic links with only small degradations in the predicted link dynamic range. An externally modulated link with a 240 mW Nd:YAG laser, a dual-output 4-V V, (dc) modulator, and balanced 100 mA total photocurrent yielded a link noise figure from 15.5 to 17.5 dB, a spur-free dynamic range of 119.5 dBHz/sup 2/3/, and a 1-dB compression dynamic range of 168.4 dBHz.

Testing the limitations of 2-D companding for strain imaging using phantoms

Abstract: Companding may be used as a technique for generating low-noise strain images. It involves warping radio-frequency echo fields in two dimensions and at several spatial scales to minimize decorrelation errors in correlation-based displacement estimates. For the appropriate experimental conditions, companding increases the sensitivity and dynamic range of strain images without degrading contrast or spatial resolution significantly. In this paper, we examine the conditions that limit the effectiveness of 2-D local companding through a series of experiments using phantoms with tissue-like acoustic and elasticity properties. We found that strain noise remained relatively unchanged as the applied compression increased to 5% of the phantom height, while target contrast increased in proportion to the compression. Controlling the image noise at high compressions improves target visibility over the broad range induced in elastically heterogeneous media, such as biological tissues. Compressions greater than 5% introduce large strains and complex motions that reduce the effectiveness of companding. Control of boundary conditions and ultrasonic data sampling rates is critical for a successful implementation of our algorithms.

Converter with 77-dB Dynamic Range

Abstract: The design of a low-voltage and low-power analog-to-digital (A/D) converter is presented. A third-order single-loop modulator topology is implemented with the differential modified switched op-amp technique. The modulator topology has been transformed as to accommodate half-delay integrators. Dedicated low-voltage circuit building blocks, such as a class AB operational transconductance amplifier, a common- mode feedback amplifier, and a comparator are treated, as well as low-voltage design techniques. The influence of very low supply voltage on power consumption is discussed. Measurement results of the 900-mV A/D converter show a 77-dB dynamic range in a 16-kHz bandwidth and a 62-dB peak signal-to-noise ratio for a 40- W power consumption.

A 115-mW, 0.5-/spl mu/m CMOS GPS receiver with wide dynamic-range active filters

Abstract: This paper presents a 115-mW Global Positioning System radio receiver that is implemented in a 0.5-/spl mu/m CMOS technology. The receiver includes the complete analog signal path, comprising a low-noise amplifier, I-Q mixers, on-chip active filters, and 1-bit analog-digital converters. In addition, it includes a low-power phase-locked loop that synthesizes the first local oscillator. The receiver achieves a 2.8-dB noise figure (prelimiter), a 56-dB spurious-free dynamic range, and a 17-dB signal-to-noise ratio for a noncoherent digital back-end implementation when detecting a signal power of -130 dBm at the radio-frequency input.

A 200 mW 3.3 V CMOS color camera IC producing 352/spl times/288 24 b video at 30 frames/s

Abstract: A digital color camera has been monolithically realized in a standard 0.8-/spl mu/m CMOS technology. The chip integrates a 353/spl times/292 photogate sensor array with a unity-gain column circuit, a hierarchical column multiplexer, a switched-capacitor programmable-gain amplifier, and an 8-b flash analog/digital converter together with digital circuits performing color interpolation, color correction, computation of image statistics, and control functions. The 105-mm/sup 2/ chip produces 24-b RGB video at 30 frames/s. The sensor array achieves a conversion gain of 40 /spl mu/V/electron and a monochrome sensitivity of 7 V/lux/spl middot/s. For a 33-ms exposure time, the camera chip achieves a dynamic range of 65 dB and peak-to-peak fixed pattern noise that is 0.3% of saturation. Digital switching noise coupling into the analog circuits is shown to be data independent and therefore has no effect on image quality. Total power dissipation is less than 200 mW from a 3.3 V supply.

A 1.5 V, 4.1 mW dual channel audio delta-sigma D/A converter

Abstract: The paper describes a stereo digital-to-analog converter intended for portable digital-audio which operates at 1.5 V and consumes only 4.1 mW. A 15-level quantization, third-order delta-sigma was employed to reduce digital operation speed, relax out-of-band filtering requirements, and enhance immunity to clock jitter. The use of direct charge transfer switched-capacitor technique in the multibit reconstruction DAC reduces kT/C noise and element mismatch without increase of power dissipation. The data weighted averaging algorithm suppresses nonlinearity caused by capacitor mismatch by first-order noise-shaping, thereby making mismatch-induced noise negligible. The stereo audio DAC achieves 90 dB dynamic range and 81 dB peak signal-to-noise-plus-distortion ratio over a 20 kHz passband. The 5.3 mm/sup 2/ chip is fabricated in a 0.6 /spl mu/m CMOS technology which includes low-threshold devices.

Detailed theoretical investigation of the input power dynamic range for gain-clamped semiconductor optical amplifier gates at 10 Gb/s

Abstract: A detailed theoretical investigation of the input power dynamic range for gain-clamped semiconductor optical amplifier (GC-SOA) gates at 10 Gb/s is presented. We show that although the gain is clamped, the dynamic changes of the carrier distribution in the GC-SOA causes pattern effects on a time scale given by the relaxation frequency of the GC-SOA. Combined with a higher noise figure compared to a conventional SOA, this results in a dynamic range only /spl sim/0.5 dB better than for an optimized SOA gate.

CMOS active pixel image sensor with CCD performance

Abstract: A color CMOS image sensor has been developed which meets the performance of mainstream CCDs. The pixel combines a high fill factor with a low diode capacitance. This yields a high light sensitivity, expressed by the conversion gain of 9 (mu) V/electron and the quantum efficiency fill factor product of 28 percent. The temporal noise is 63 electrons, and the dynamic range is 67 dB. An offset compensation circuit in the column amplifiers limits the peak-to-peak fixed pattern noise to 0.15 percent of the saturation voltage.

Photodetector designs for low-noise, broadband, and high-power applications

Abstract: We present design and performance details of three photodetector circuits that have been developed in the authors laboratory over the past eight years. These detectors have been optimized to meet the unique demands of experiments such as high power, high sensitivity interferometry, nonlinear optics, and laser noise measurements. The circuits are: a low-noise dc coupled (dc 20 MHz) general purpose detector, a low-noise broadband (15–1100 MHz) detector capable of detecting 10 mW of light, and a high-power large dynamic range detector (30 kHz–60 MHz) capable of detecting up to 100 mW of light. We present bandwidth dynamic range and noise performance details for all three designs. In addition, we present detailed circuit schematics along with design and construction guidelines to enable assembly and use of these designs.

Closed Loop Silicon Accelerometers

Abstract: The control-system structure and behaviour are considered for an analogue and a digital servo-accelerometer having a dynamic range from mg to several g (1g=9.81 ms/sup -2/), for use in low-frequency applications. The paper emphasises the derivation of mathematical models, which are presented together with simulated and test results obtained from the implementation of these strategies on a bulk-micromachined silicon sensing element employing capacitive signal pick-off. The digital device, which is based upon oversampling conversion, proved to have superior stability compared to the analogue accelerometer. Furthermore, it has the advantages of producing a direct digital output signal and an inherent self-test feature.

Image pickup apparatus and method for broadening apparent dynamic range of video signal

Abstract: An image pickup method and an image pickup apparatus are provided which can pick up an image with a broad substantial dynamic range even with a video camera or the like which is likely to be subject to image shifts. In increasing an apparent dynamic range of a video signal by synthesizing a single image from a plurality of images sequentially picked up at different exposure amounts, if a difference between a motion vector between pixels in a plurality of images and a motion vector between images is larger than a predetermined threshold value, the pixel is not used for synthesization. Even a video signal having an image shift caused by a motion of an object itself or hand vibration can be subjected to a practically usable dynamic range increasing process.

Stochastic-flash analog-to-digital conversion

Abstract: Flash-type analog-to-digital converters (ADC's) presenting a nonlinear behavior, i.e., having nonequally spaced threshold levels, may introduce harmonic distortion that can be reduced by employing large-amplitude dither-based conversion techniques. However, large-scale dithering is difficult to implement and, in addition, severely reduces the ADC input dynamic range. In this paper, a new ADC architecture is presented based on ordinary flash conversion and dynamic element matching, that strongly reduces nonlinear distortion. It eliminates the need for large-scale dither signals by randomizing the resistor positions in the resistor string used to generate the voltage references. Some properties of this architecture are analyzed and simulation results that validate the theoretical assumptions are presented.

Imaging apparatus with dynamic range expanded, a video camera including the same, and a method of generating a dynamic range expanded video signal

Abstract: An imaging circuit generates a first video signal with a first exposure interval and a second video signal with a second exposure interval substantially at the same time, the second exposure interval being shorter than the first exposure interval, the first and second video signals respectively having first and second dynamic ranges which are different but continues. The first video signal is synchronized with the second video signal. An exposure ratio between the first and second exposure intervals is detected. A gain of the second video signal is adjusted according to the exposure ratio. A combined video signal is generated from the first and second video signals according to a mixing control signal indicative of a mixing ratio between first and second video signals and levels of the first and second video signals to have an expanded dynamic range such that the first dynamic range is connected to the second dynamic range with difference in gains of the first and second video signals adjusted for linearity. An edge enhancement signal may be gain-controlled or coring-controlled according to the mixing control signal or the exposure ratio. The similar apparatus and method for color signals are also disclosed. The output dynamic range for a display is limited by a non-linear process.

Photon statistics of amplified spontaneous emission noise in a 10-Gbit/s optically preamplified direct-detection receiver

Abstract: We verify experimentally, over a dynamic range of 55 dB in the probability distribution, that the amplified spontaneous emission noise of the 0’s from an optically preamplified receiver is degenerate Bose–Einstein distributed. Using the noise parameters extracted from the experiment, we are able to predict the sensitivity of a 10-Gbit/s direct-detection receiver.

Wideband phase-noise measurement of mode-locked laser pulses by a demodulation technique.

Abstract: A new method is proposed and demonstrated for measuring the phase noise (pulse timing fluctuations) of mode-locked lasers. The instantaneous phases of the pulse intensity are extracted in a time domain, and the phase-noise power spectral density is calculated from the demodulated signals. Compared with the conventional method based on the single-sideband phase-noise measurement, the proposed method has a larger dynamic range and a wider frequency span. The phase noise of a mode-locked Cr:LiSAF laser is measured for 50-mHz-1-MHz Fourier frequencies.

All optical wavelength conversion schemes for increased input power dynamic range

Abstract: Schemes for increasing the input power dynamic range of interferometric wavelength converters are presented with experiments at 10 Gb/s showing large improvements. A simple conversion scheme that uses current control of the interferometer improves the dynamic range from /spl sim/3-/spl sim/8 dB. A simpler method of inserting an Er-doped fiber amplifier (EDFA) before the converter results in more than 40 dB of dynamic range while a method of using a semiconductor optical amplifier (SOA) for power control gives /spl sim/28-dB dynamic range.

High-resolution laser rangefinder based on a phase-shift measurement method

Abstract: The laser range-finder presented here has been designed as a part of a non-destructive testing system. The whole conception of the system is detailed. The method is based on phase-shift measurement, but using electronic heterodynage to provide a good resolution. An RF card is the heart of the system, including two VCO and two active mixers, providing the modulation signal and both reference and phase shifted signal at intermediate frequency of 125 kHz. The emitter is a laser diode at 12 mW average output power, the receiver uses an avalanche photodiode. We also find an amplification board with an 80 dB dynamic range AGC, and the frequencies control board. The phase shift is estimated by direct counting with more than 10 bits resolution, that means about 0.4 mm for a 60 cm range without phase ambiguity. The amplification level, obtained from the AGC loop, gives an estimation on the measurement quality and on the target surface. A PC computer controls the range-finder through an interface specially developed. It is based on two PLD, one for the general sequencement and one for the averaging of the data. The obtained data are stored in a 2Kb FIFO memory waiting a data request for the PC or generating an interrupt if it is full. The interface is easy to drive from the PC with the choice for averaging value, and amplification criterion. The imaging should be provided by scanning mirrors. Measurement of the target distance and estimation of the target surface conducts to laser imaging. Altogether the system is rather compact due to the disposition of the cards and also rather low-cost.

High dynamic range apparatus for separation and detection of polynucleotide fragments

Abstract: A high dynamic range apparatus for separation and detection of polynucleotide fragments has a housing adapted to receive an electrophoresis gel holder containing an electrophoresis gel loaded with fluorophore-labeled samples; one or more laser diodes for providing radiation of a frequency suitable for excitation of the fluorophore which irradiates an array of excitation/detection sites on the electrophoresis gel; an array of detectors aligned with the excitation/detection sites for collecting fluorescent emissions; and one or more components for increasing the dynamic range of the instrument by at least an order of magnitude. These components, which can be used individually or in combination include detectors that are connected to a signal processing system that modulates the period of signal integration employed so that large signals are totaled at short time intervals and smaller signals are totaled at longer time intervals; the use of a beam splitter to produce a high intensity beam of emitted light and a low intensity beam of emitted light from each excitation/detection site; and a device for modulating the intensity of the excitation beam can be used to improve the dynamic range of the instrument.

Reduction of nonlinear distortion in MQW semiconductor optical amplifier using light injection and its application in multichannel M-QAM signal transmission systems

Abstract: By using an external light-injected multiple-quantum-well (MQW) semiconductor optical amplifier (SOA), we have demonstrated a 100-km optical fiber link that transports 77 channels of 64-QAM signals. This is equivalent to a system capacity of 2.3 Gb/s, while using a laser bandwidth of only 550 MHz. Under a requirement of carrier to noise and nonlinear distortion ratio of 30 dB per channel, the 1310-nm gain-peaked SOA input dynamic range was increased from 0 to 9 dB due to an injected light with 8.8 dBm and a wavelength of 1284 nm.

Practical spread spectrum pulse compression for ultrasonic tissue imaging

Abstract: Spread spectrum pulse compression is a signal processing algorithm that enhances critical system performance parameters such as signal-to-noise ratio, peak power requirements, minimum detectable signal, and total dynamic range. For this research, a digital, real-time, Barker coded, bi-phase modulator was designed and constructed, as well as a simple ultrasonic test tank containing both synthetic targets and excised goat's liver. Upon reception and demodulation of the spread spectrum ultrasonic echo, cross-correlation with a sidelobe suppression filter was performed. Due to limitations such as narrow bandwidth, and very short minimum ranges, a practical ultrasonic pulse compression system must be restricted to short code lengths. For 13 bit Barker code compression, the expected increase in signal-to-noise ratio of 11 dB was realized; at the same time greater than 30 dB of instantaneous dynamic range was maintained.

Novel large-area MIS-type x-ray image sensor for digital radiography

Abstract: We have developed a brand new, large-area X-ray image sensor for Digital Radiography System (DRS). The sensor utilizes a thin film transistor (TFT)/metal insulator semiconductor (MIS)-type photoelectric converter array made from hydrogenated amorphous silicon (a-Si:H). The sensor has 2688 X 2688 pixels at a pitch of 160 micrometer. The active area is 17 inch X 17 inch. The sensor utilizes scintillator coupled to the array. The light generated by X-rays is detected by the MIS-type photoelectric converters, and the resultant signals are scanned out by switching the TFTs. The a-Si TFT/MIS-type photoelectric converter array is characterized by high signal to noise ratio (SNR) and simple fabrication process. We will describe the principle and the performance of the sensor. In addition, we will present some X-ray images of a human subject obtained with this sensor. Dynamic range of the sensor covers most of the exposure range for radiography. SNR is limited almost only by the X-ray photon noise. MTF is sufficient for digital chest radiography. X-ray images have good contrast. The experimental results and obtained images show that the brand new sensor has great advantages for replacing X-ray film. The simple fabrication process of the sensor promises high productivity and low cost of DRS.

Micromachined thermocouple microwave detector by commercial CMOS fabrication

Abstract: This paper reports on the design and testing of a thermocouple microwave detector fabricated through a commercial CMOS foundry with an additional maskless etching procedure. The detector measures true r.m.s. power of signals in the frequency range from 50 MHz to 20 GHz, and input power range from -30 to +10 dBm, the device has linearity better than /spl plusmn/0.4% for input power versus output voltage over the 40 dB dynamic range. Measurements of the return loss, obtained using an automatic network analyzer, show acceptable input return loss of less than -20 dB over the entire frequency range. The sensitivity of the detector was measured to be (1.007/spl plusmn/0.004) mV/mW.

Method and apparatus for producing high-fidelity images by synchronous phase coherent digital image acquisition

Abstract: An apparatus and method for synchronizing sampling of a video signal to a video synchronization signal of the video signal are provided. The frequency-divided output of an oscillator (or other controllable frequency source) is applied as one input to a phase detector, while the other input to the phase detector is supplied by the video synchronizing signals. The error signal voltage output of the phase detector is applied to correct the frequency, and thereby the phase, of the oscillator output through a dynamically-tuned phase-locked loop filter until the phases of the two input signals are in perfect agreement and no error voltage is produced. After a delay for this phase correction, during which time all video amplification is suspended, an output of the oscillator is then applied to sample the image without the presence of phase disparities while video amplification is restored. Full dynamic range digital acquisition then proceeds with extremely high accuracy at any desired resolution. An apparatus and method are provided for achieving such operation.

Low distortion analogue signal transmission using vertical cavity lasers

Abstract: Signal distortion in a short wavelength vertical cavity surface-emitting laser (VCSEL) is studied. The spurious free dynamic range is found to be 104.3 dB Hz2/3 at 102 MHz and 98 dB Hz2/3 at 1 GHz, which approaches the dynamic range of Fabry-Perot and DFB lasers, and is 20 dB higher than previously reported for VCSELs.

A multimode digital detector readout for solid-state medical imaging detectors

Abstract: A multipurpose digital detector readout for medical imaging applications is presented. The readout is capable of measuring both current and charge, allowing a single detector array to perform imaging functions previously accomplished with two separate machines. The circuit employs a variable rate /spl Sigma//spl Delta/ analog-to-digital converter (ADC) to measure current over a 130-dB dynamic range in a 1 kHz band and resolve charge pulses down to 360 e/sup -/ at 100 000 events/s. Detector currents of up to 7 /spl mu/A and charge pulses as large as 25 fC can be measured. A low-noise charge sensing amplifier (CSA) is combined with digital pulse shaping to optimize the noise performance and flexibility of the charge measurements. Fabricated in an 1.2 /spl mu/m complimentary metal-oxide-semiconductor (CMOS), the circuit occupies 1.5 mm/sup 2/ and dissipates 11 mW/channel from a 5 V supply.

A flow cytometer designed for fluorescence calibration.

Abstract: In the development of suitable standards and calibration materials for fluorescence measurement, it becomes necessary to make accurate fluorescence measurements of these materials on flow cytometers. The results of such measurements may be affected by numerous sources of error, prominent among which are deviations of logarithmic amplifiers (log amps) from ideal response. To minimize the deleterious effects of log amps and multicolor fluorescence compensation circuitry on measurements, we built a flow cytometer with electronics incorporating high-precision peak detectors usable over a range from below 2 mV to 10 V, and we developed data acquisition software that transfers held peak values to a commercial 16-bit data acquisition system mounted in a personal computer running Windows 95. Fluorescence compensation is done in software, and transformation of the compensated data from a 16-bit linear to an 8-bit, 4-decade logarithmic scale is accomplished using a look-up table. Although dynamic range may be restricted by noise in the data acquisition system, high sensitivity can be achieved by photomultiplier tube gain adjustment, and it is likely that the use of a lower noise data acquisition system and/or digital processing of pulse information will enable operation over the full 4-decade dynamic range. Even at its current performance level, our instrument provides substantially better linearity over most of the scale than can be obtained using conventional electronics incorporating log amps; we believe this characteristic is critical for use in standards development.