Showing papers on "Dynamic range published in 1994"

Adaptive photoreceptor with wide dynamic range

Abstract: We describe a photoreceptor circuit that can be used in massively parallel analog VLSI silicon chips, in conjunction with other local circuits, to perform initial analog visual information processing. The receptor provides a continuous-time output that has low gain for static signals (including circuit mismatches), and high gain for transient signals that are centered around the adaptation point. The response is logarithmic, which makes the response to a fixed image contrast invariant to absolute light intensity. The 5-transistor receptor can be fabricated in an area of about 70 /spl mu/m by 70 /spl mu/m in a 2-/spl mu/m single-poly CMOS technology. It has a dynamic range of 1-2 decades at a single adaptation level, and a total dynamic range of more than 6 decades. Several technical improvements in the circuit yield an additional 1-2 decades dynamic range over previous designs without sacrificing signal quality. The lower limit of the dynamic range, defined arbitrarily as the illuminance at which the bandwidth of the receptor is 60 Hz, is at approximately 1 lux, which is the border between rod and cone vision and also the limit of current consumer video cameras. The receptor uses an adaptive element that is resistant to excess minority carrier diffusion. The continuous and logarithmic transduction process makes the bandwidth scale with intensity. As a result, the total AC RMS receptor noise is constant, independent of intensity. The spectral density of the noise is within a factor of two of pure photon shot noise and varies inversely with intensity. The connection between shot and thermal noise in a system governed by Boltzmann statistics is beautifully illustrated. >

A third-order sigma-delta modulator with extended dynamic range

Abstract: Oversampling modulators based on high-order sigma-delta modulation provide an effective means of achieving high-resolution analog-to-digital conversion in VLSI technology. Because high-order noise shaping greatly reduces the quantization noise in the signal band, the dynamic range of these modulators tends to be bounded by the thermal noise of the input stage and the maximum voltage swing in the signal path. This paper introduces a third-order cascaded sigma-delta modulator that uses a modified cascaded architecture and reduced gain in the first integrator to increase the dynamic range. An experimental modulator fabricated in a 1-/spl mu/m CMOS technology attains a resolution of 17 b for a 25-kHz signal bandwidth while operating from a single 5-V supply. With an oversampling ratio of 128 and a clock frequency of 6.4 MHz, the modulator achieves a 104-dB dynamic range and a peak signal-to-noise+distortion ratio (SNDR) of 98 dB. As indicated by both measurements and simulations, the cascaded architecture also greatly reduces the discrete noise peaks that can be present in a single-stage architecture. >

A wide-dynamic-range, low-power photosensor array

Abstract: A 32/spl times/32 array of photosensors with pulse frequency outputs uses standard 2 /spl mu/m CMOS technology. The photosensors use pulse-frequency encoding to achieve a linear dynamic range of 10/sup 6/ in optical energy. Power dissipation of the photosensor is proportional to the frequency of the pulse outputs, and under typical illumination and bias conditions, the entire 32/spl times/32 array dissipates >

Progress in CMOS active pixel image sensors

Abstract: Recent research results regarding the investigation of CMOS active pixel image sensors (APS) are reported. An investigation of various designs for the pixel, including photogate devices of various geometries and photodiode devices, has been performed. Optoelectronic performance including intrapixel photoresponse maps taken using a focused laser scanning apparatus are presented. Several imaging arrays have also been investigated. A 128 X 128 image sensor has been fabricated and characterized. Both p-well and n-well implementations have been explored. The demonstrated arrays use 2 micrometers CMOS design rules and have a 40 X 40 micrometers pixel pitch. Typical design fill-factor is 26%. Output sensitivity is 3.7 (mu) V/e- for the p-well devices and 6.5 (mu) V/e- for the n-well devices. Read noise is less than 40 e- rms for the baseline designs. Dynamic range has been measured to be over 71 dB using a 5 V supply voltage. The arrays are random access with TTL control signals. Results regarding on-chip suppression of fixed pattern noise also are presented.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Optical carrier filtering for high dynamic range fibre optic links

Abstract: Optical carrier filtering is used with an externally modulated fibre optic link to maintain high dynamic range operation with significantly reduced optical power levels. A spur-free dynamic range of 115 dBHz/sup 2/3/ is achieved for a frequency of 17 GHz with a received optical power of only 1.5 mA. An external filter is used to demonstrate a 10 dB improvement in dynamic range for a fixed optical power level.

Image data processing apparatus for processing combined image signals in order to extend dynamic range

Abstract: An image data processing apparatus includes a controller which matches a dynamic range of image data to be outputted to an output unit to a dynamic range of data and/or to an output characteristic of the output unit so that the data may be processed in the output unit.

A High Resolution Multibit Sigma-delta Modulator With Individual Level Averaging

Abstract: A second-order sigma-delta modulator with a 3-b internal quantizer employing the individual level averaging technique has been designed and implemented in a 1.2 μm CMOS technology. Testing results show no observable harmonic distortion components above the noise floor. Peak S/(N + D) ratio of 91 dB and dynamic range of 96 dB have been achieved at a clock rate of 2.56 MHz for a 20 KHz baseband. No tone is observed in the baseband as the amplitude of a 10 KHz input sine wave is reduced from −0.5 dB to −107 dB below the voltage reference. The active area of the prototype chip is 3.1 mm 2 and it dissipates 67.5 mW of power from a 5 V supply

A 16-b D/A converter with increased spurious free dynamic range

Abstract: A novel approach to D/A switch design has resulted in improved frequency domain performance for direct digital synthesis for clock rates up to 40 MSPS. Use of the new switch in a BiCMOS 16-b DAC has achieved a spurious free dynamic range of greater than 80 dB. >

Switched-current memory circuits for high-precision applications

Abstract: We discuss circuit parameters that limit the precision of basic dynamic current-memory cells. In addition to analyzing current-copying errors caused by the finite output conductances of the current sources and by the clock-feedthrough (CFT) of the feedback switches, we analyze the noise performance of the basic memory cell. To reduce CFT and noise, we propose a novel circuit based on Miller capacitance-enhancement. Measurement results of memory cells integrated in a 1-/spl mu/m CMOS process confirm the theoretical findings; with our CFT and noise reduction technique based on Miller enhanced capacitance and dummy switches, we achieve a dynamic range of 11 b at clock frequencies greater than 100 kHz. >

A digitally-corrected 20b delta-sigma modulator

Abstract: Transducers such as photodiodes produce signal currents in the 1 pA to 1 /spl mu/A range. To achieve a six-decade dynamic range, thermal noise currents at the system input must be minimized. The authors show that including the transimpedance photodiode amplifier in a delta-sigma modulated loop with digitally-corrected trilevel quantizers/DACs leads to lower thermal noise. The characteristics of the modulator are summarized. >

High-frequency photodiode characterization using a filtered intensity noise technique

Abstract: Optical filtering of amplified spontaneous emission improves measurement dynamic range for frequency response measurements of optoelectronic receivers. For high bandwidth receivers, a novel periodically filtered intensity noise technique is proposed. Response measurements using these techniques on a 1 GHz and 30 GHz receiver are demonstrated. >

Effect of compression ratio in a slow-acting compression hearing aid: paired-comparison judgments of quality

Abstract: Paired-comparison judgments of quality were obtained from 20 hearing-impaired listeners (half with a small dynamic range and half with a large dynamic range) for speech-in-noise (vent, apartment, and cafeteria) processed through a slow-acting compression hearing aid. Compression ratio was varied (1, 1.5, 2, 3, 5, and 10:1). Compression threshold, attack time, and release time were fixed. Sound quality judgments were significantly affected by compression ratio, noise, and dynamic range. Preference decreased with increasing compression ratio. The selection of compression ratio. The selection of compression ratios 3:1. Less compression (no compression or 1.5:1) was preferred with the highest level noise (cafeteria noise) than with the lower level noises (vent or apartment). In particular, the small dynamic range group preferred compression with the vent and apartment noises (noise below the compression threshold), but preferred a linear hearing aid with the cafeteria noise (above the compression threshold). The large dynamic range group showed a slightly greater preference for the linear hearing aid for all three noises.

Image signal processing apparatus having function for compressing dynamic range and correcting color saturation

Abstract: An input section receives an image signal including signals related to colors to output at least a luminance signal component of the image signal. A compressing section compresses the dynamic range of the luminance signal component from the input section. A setting section obtains a compression coefficient from a relationship between the luminance signal component whose dynamic range is compressed by the compressing section and the luminance signal component from the input section. An operating section executes an operation for compressing dynamic ranges of the signals related to colors included in the image signal in accordance with the compression coefficient obtained by the setting section. A correcting section substantially corrects the color saturation of the signals related to a color included in the image signal while preserving the luminance of the image signal such that the color saturation is more intensively suppressed as the luminance becomes lower.

Spur-free dynamic range measurements of a fiber optic link with traveling wave linearized directional coupler modulators

Abstract: Two-tone testing was performed on a laboratory fiber optic link with LiNbO/sub 3/ traveling wave linearized directional coupler modulators. The third-order distortion was measured at 500 MHz and 1000 MHz, and the spur-free dynamic range was determined. Two modulator configurations, with either one or two passive bias sections, were tested and the results were compared with measurements of simple directional coupler modulators. A 9.5-11 dB improvement in the dynamic range was found in the links employing the linearized modulators. >

Silicon range finder-a realtime range finding VLSI sensor

Abstract: In this paper, we present a range-imaging VLSI vision sensor which is able to measure the 3D position in realtime. Photodiodes and an operational circuit are integrated into each pixel to function as a micro-rangefinder in mixed analog-digital technology. A 2D array chip of this micro-rangefinders is able to capture fully parallel a dynamic range image. A complementary pair of photodiodes has the advantage of capturing reliable 3D data without disturbance due to the temperature drift, the ambient light, the manufacturing dispersion and other noises. The prototype system gives us a 24/spl times/24 range image with high accuracy at video frame-rate. >

Technology and Performance of TFA (Thin Film on ASIC-Sensors

Abstract: A TFA image sensor consists of an amorphous silicon based multilayer structure on top of a crystalline ASIC. The Multilayer acts as the optical detector, whereas the ASIC performs analog or digital signal processing for each individual pixel. Depending on the operation Mode, the dynamic range of the detector exceeds the performance of conventional CCDs by far. Pixel electronics which is adapted to the requirements of the detector can thereby maximize the dynamic range of the complete sensor array. Crosstalk among adjacent pixels can be eliminated by technological or electronic Means.

Ultra-linear chirp generation via VCO tuning predistortion

Abstract: The multiple signal dynamic range and frequency resolution of wide bandwidth compressive receivers (CR), two key parameters of surveillance systems, have historically been limited by swept local oscillator (SLO) performance. Noise, spurious signals, and nonlinear frequency-time slopes in the SLO have been the cause of these limitations. This paper describes a technique to generate an SLO for a CR application which improves the multiple signal dynamic range by 15 dB over previous techniques at a much lower cost, and with less complexity. This technique for high speed linear chirp generation also has applications in FMCW or pulse compression radar systems. >

Method for electronic image dynamic range and contrast modification

Abstract: A dynamic range and contrast modification method for electronic images, and digital and analogue implementations are disclosed. Dynamic range changes are accomplished by making linear and nonlinear modifications to the low frequency component. Contrast changes are accomplished by making cross dependent, linear, and nonlinear modifications to the high frequency component. Cross dependent modifications are modifications that depend upon the changes to the low frequency component. Modifications are achieved using processor elements that implement mathematical operations. An automatic gain control, AGC, is used to control the low frequency component modification for some embodiments.

Wide dynamic range vision sensor for vehicles

Abstract: The dynamic range of brightness on road scenes is very wide, because the lighting condition dynamically varies with various weather and road conditions. Therefore, the dynamic range of conventional TV cameras is insufficient to input the images of road scenes. The authors have developed a method for expanding the dynamic range of TV cameras. Also, they have developed an experimental vision sensor system with a wide dynamic range based on the method applicable to the vision systems for vehicles. The effectiveness of the sensor in comparison with conventional TV cameras was confirmed from the experiments on highways under various lighting conditions. >

A low noise integrated AMPS IF filter

Abstract: A 455 KHz IF filter suitable for AMPS cellular telephone applications has been developed in a 1.2 /spl mu/m CMOS technology. The design is based on interspersion of repeated AGC and leapfrog g/sub m/-C stages. Including RSSI circuitry, the active area is 17 mm/sup 2/. It draws 6.5 mA from a single ended 5 V supply. Measured results confirm a dynamic range of 64 dB and an S/(N+D) of 40 dB, sufficient for AMPS cellular applications. >

A cellular analog front end with a 98 dB IF receiver

Abstract: To date, mixed-signal CMOS devices designed for cellular telephony have adopted conventional receiver architectures. They consist of dual baseband A/D converters with performance limited to approximately 60 to 75 dB dynamic range. Thus, these architectures require the following components in the preceding IF strip. Since the overall system dynamic range is on the order of 140 dB, a large amount of programmable gain (80-100 dB) is required in the preceding RF/IF strip to preserve the system noise. External filters at both the first and second IF frequencies are required to provide full channel selectivity before the A/D conversion is performed. Also, dual analog quadrature mixers are required to convert the receive signal from the second IF to baseband. The mixed-signal CMOS device presented in this paper substantially reduces the programmable gain, filtering, and external components required in the IF strip. This is accomplished by performing an IF A/D conversion and providing 98 dB dynamic range. >

A Novel α-Si(C):H Color Sensor Array

Abstract: A novel α-Si(C):H color sensor array has been developed. In this device a single pixel consists of a combination of an amorphous silicon nipin detector and a crystalline operational amplifier. Steady state and transient opto electronic behavior of the nipin structure have been studied in order to optimize the design of the image sensor. Nipin structures are found to exhibit excellent dynamic range (125 dB) and linearity. The crystalline electronics causes only very little signal distortion which makes this sensor device a potential candidate for color image capture and processing for a wide range of illumination levels.

An analog memory integrated circuit for waveform sampling up to 900 MHz

Abstract: The design and implementation of a switched-capacitor memory suitable for capturing high-speed analog waveforms is described. Highlights of the presented circuit are a 900 MHz sampling frequency (generated on chip), input signal independent cell pedestals and sampling instances, and cell gains that are insensitive to component sizes. A two-channel version of the memory with 32 cells for each channel has been integrated in a 2-/spl mu/m complementary metal oxide semiconductor (CMOS) process with polysilicon-to-polysilicon capacitors. The measured rms cell response variation in a channel after cell pedestal subtraction is less than 0.3 mV across the full input signal range. The cell-to-cell gain matching is better than 0.01% rms, and the nonlinearity is less than 0.03% for a 2.5-V input range. The dynamic range of the memory exceeds 13 bits, and the peak signal-to-(noise+distortion) ratio for a 21.4 MHz sine wave sampled at 900 MHz is 59 dB. >

A fuzzy filter for dynamic range reduction and contrast enhancement

Abstract: When an image with a large dynamic range is recorded on media with a smaller dynamic range, details that represents in very high and/or very low luminance regions become invisible. In this paper a fuzzy logic based solution to this problem is proposed. The algorithm estimates the image brightness and hence common sense rules determine the amount of dynamic range reduction. These rules are based on global (i.e. image level) and local (i.e. pixel level) brightness characteristics. To extract visual details, a fuzzy process calculates the contrast amplification factor according to the luminance reduction performed. >

Camera with large dynamic range

Abstract: In accordance with the present invention, an apparatus and method are described which in general provide for an extended dynamic range in light sensitivity for an imaging device. This extended dynamic range is achieved primarily through control of the light intensity level in a image on a pixel by pixel basis. In one aspect, a multi-faceted light controller is used like a variable iris camera, but on a pixel by pixel basis; thereby achieving a wider range of intensity control. In another aspect, this system is enhanced by adding another controller outside the feedback loop, before an added output image detector. In yet another aspect, some or most of the elements of the controlling and detecting system may be integrated into a composite monolithic structure.

Avalanche photodiodes as large dynamic range detectors for synchrotron radiation

Abstract: We investigated silicon-based avalanche photodiodes (APDs) as X-ray detectors in terms of their linearity, maximum counting rates, and dynamic range with 8.4 keV synchrotron radiation. Measurements resulted in counting rates that extend from the APD's noise level of 10−2 Hz to saturation counting rates in excess of 108 Hz. In addition, by monitoring the APD's noise level and photon counting efficiency between synchrotron bursts, we demonstrate nine orders of magnitude dynamic range.

Field cross correlator for analysis of ultrafast signals

Abstract: The cross-correlation function between two light fields is recorded with the help of a new device. The proposed correlator exhibits ultrashort time resolution. The optical path difference between the two interfering beams does not have to be known with interferometric precision. The experimental dynamic range proved to be as large as 105. The device features imaging capabilities that could be applied to the analysis of two-dimensional images with ultrashort time resolution.

Enhanced means of processing signals used to interpret the condition of machinery

Abstract: A method of processing electrical signals which span a large dynamic range in order to enable the signal to be processed in its entirety without the need for any alteration to the signal gain or signal attenuation, comprises splitting of the signal along two or more paths each having a different amount of amplification or attenuation, the passing of each of these two or more different signals into one of two or more smaller dynamic range circuits which produce a logarithmically scaled representation of the average magnitude of the signal level at its input and the summation of the logarithmic outputs of the two or more smaller dynamic range circuits to produce a resultant logarithmically scaled signal representative of the average magnitude of the input signal over a very large dynamic range. The invention also includes apparatus for carrying out the above defined method.

1.9 picosecond high-sensitivity sampling optical temporal analyzer

Abstract: An all solid‐state, high‐sensitivity sampling optical temporal analyzer has been demonstrated by integrating two interdigitated picosecond metal‐semiconductor‐metal photodetectors into a coplanar transmission line structure. The full width at half‐maximum of the response time is 1.9 ps. The noise equivalent optical power is 500 pW, and the dynamic range is more than 60 dB.

Real-time wave-amplitude spectrum analyzer for air-liquid interfaces

Abstract: We describe a method for the direct, absolute and noninvasive measurement of surface height profiles on air‐liquid interfaces. Wave amplitude spectra are directly obtained from electronically imaged surface height profiles without resorting to problematic reconstructions from wave slope measurements. This measurement principle relies on the volume attenuation of light in the liquid rather than the refraction of light at the wave‐supporting interface. Surface height resolution of tens of micrometers has been demonstrated. A suitable photodiode detector and an appropriate laser provide the two parameters which are sufficient to optimize system spatial and temporal resolution and spatial dynamic range.