Showing papers on "Dynamic range published in 2000"

High dynamic range imaging: spatially varying pixel exposures

Abstract: While real scenes produce a wide range of brightness variations, vision systems use low dynamic range image detectors that typically provide 8 bits of brightness data at each pixel. The resulting low quality images greatly limit what vision can accomplish today. This paper proposes a very simple method for significantly enhancing the dynamic range of virtually any imaging system. The basic principle is to simultaneously sample the spatial and exposure dimensions of image irradiance. One of several ways to achieve this is by placing an optical mask adjacent to a conventional image detector array. The mask has a pattern with spatially varying transmittance, thereby giving adjacent pixels on the detector different exposures to the scene. The captured image is mapped to a high dynamic range image using an efficient image reconstruction algorithm. The end result is an imaging system that can measure a very wide range of scene radiance and produce a substantially larger number of brightness levels, with a slight reduction in spatial resolution. We conclude with several examples of high dynamic range images computed using spatially varying pixel exposures.

A logarithmic response CMOS image sensor with on-chip calibration

Abstract: CMOS image sensors with logarithmic response are attractive devices for applications where a high dynamic range is required. Their strong point is the high dynamic range. Their weak point is the sensitivity to pixel parameter variations introduced during fabrication. This gives rise to a considerable fixed pattern noise (FPN) that deteriorates the image quality unless pixel calibration is used. In the present work a technique to remove the FPN by employing on-chip calibration is introduced, where the effect of threshold voltage variations in pixels is cancelled. An image sensor based on an active pixel structure with five transistors has been designed, fabricated, and tested. The sensor consists of 525/spl times/525 pixels measuring 7.5 /spl mu/m/spl times/10 /spl mu/m, and is fabricated in a 0.5-/spl mu/m CMOS process. The measured dynamic range is 120 dB while the FPN is 2.5% of the output signal range.

Apparatus and method for high dynamic range imaging using spatially varying exposures

Abstract: Apparatus and methods are provided for obtaining high dynamic range images using a low dynamic range image sensor. The scene is exposed to the image sensor in a spatially varying manner. A variable-transmittance mask, which is interposed between the scene and the image sensor, imposes a spatially varying attenuation on the scene light incident on the image sensor. The mask includes light transmitting cells whose transmittance is controlled by application of suitable control signals. The mask is configured to generate a spatially varying light attenuation pattern across the image sensor. The image frame sensed by the image sensor is normalized with respect to the spatially varying light attenuation pattern. The normalized image data can be interpolated to account for image sensor pixels that are either under or over exposed to enhance the dynamic range of the image sensor.

A high-dynamic-range CMOS image sensor for automotive applications

Abstract: In this paper, a 256/spl times/256 pixel CMOS imager is described that exhibits 120 dB dynamic range, 56 dB signal-to-noise ratio (SNR), 65% fill factor, and an effective frame rate of 50 Hz. This has been achieved using a unique combination of a multiexposure and a multigain linear readout. The imager has been integrated in 1 /spl mu/m double-metal CMOS technology. The intended application is for driver's assistant systems, but the imager can be used for a wide range of applications requiring high dynamic range.

A multibit delta-sigma audio DAC with 120-dB dynamic range

Abstract: A 24-bit 192-kHz sample-rate digital-to-analog converter (DAC) achieves 120-dB A-weighted dynamic range in the 20-kHz band, and consumes 310 mW with a 5-V power supply. A third-order five-bit /spl Delta//spl Sigma/ architecture optimized for high-end consumer audio has been developed and used. A switched-capacitor (SC) DAC combined with infinite-impulse response (IIR) and finite-impulse response (FIR) filters is employed to increase immunity to clock jitter, and reduce analog power. Partial-range dynamic element matching (DEM) enhances mismatch shaping with reduced circuit overhead. The 7.8-mm/sup 2/ chip fabricated in 0.5-/spl mu/ m CMOS integrates a stereo DAC and all functions required for DVD-audio playback.

Phase-encoded optical sampling for analog-to-digital converters

Abstract: A high-speed optical sampling system for electrical signals has been developed using a gain-switched diode laser and a dual-output Mach-Zehnder interferometer. The optical phase shift between the branches of the interferometer is highly linear in the applied electrical signal. The phase shift is encoded in the two outputs of the interferometer and is recovered through digital signal processing. Analog-to-digital (A/D) conversion with 78-dB spur-free dynamic range is demonstrated. Our phase-encoded sampling technique allows high-resolution (12-bit) conversion with high linearity at practical laser power levels.

Recent developments in X-ray imaging detectors

Abstract: The replacement of the radiographic film in medical imaging has been the driving force in X-ray imaging developments. It requires a ∼40 cm wide detector to cover all examinations, an equivalent noise level of 1–5 X-ray quanta per pixel, and spatial resolution in the range 100–150 μm. The need for entirely electronic imaging equipments has fostered the development of many X-ray detectors, most of them based on an array of amorphous silicon pixels, which is the only technology capable to achieve such large areas. Essentially, two concepts have been implemented: • intermediate conversion of X-rays to light by a scintillator, detected by an array of light sensitive pixels, comprising a photodiode and a switching device, either a TFT or a diode. • conversion into electron–hole pairs in a photoconductor, collected by an array of electrodes and switches. In both cases, charge amplifiers read the generated charges line by line. Scintillator and photoconductor-based systems are now close to production. They achieve better image quality than the classic film-screen combination, at lower X-ray dose and with a much broader dynamic range. Dynamic imaging up to 30 frames/s has been demonstrated. The technical challenges at the level of the a-Si array are the number of acceptable defects, the on/off ratio of the switches, the quantum efficiency of the photodiodes, the memory effects associated with traps in a-Si. Of course, long-term reliability is a major concern for medical components.

A 3.3-V single-poly CMOS audio ADC delta-sigma modulator with 98-dB peak SINAD and 105-dB peak SFDR

Abstract: This paper presents a second-order /spl Delta//spl Sigma/ modulator for audio-band analog-to-digital conversion implemented in a 3.3-V, 0.5-/spl mu/m, single-poly CMOS process using metal-metal capacitors that achieves 98-dB peak signal-to-noise-and-distortion ratio and 105-dB peak spurious-free dynamic range. The design uses a low-complexity, first-order mismatch shaping 33-level digital-to-analog converter and a 33-level flash analog-to-digital converter with digital common-mode rejection and dynamic element matching of comparator offsets. These signal-processing innovations, combined with established circuit techniques, enable state-of-the art performance in CMOS technology optimized for digital circuits.

Applications of active arrayed-waveguide gratings in dynamic WDM networking and routing

Abstract: We describe how active arrayed-waveguide gratings (AWGs) may find a diverse range of applications in future dynamic wavelength division multiplexed (WDM) networking and routing. Our initial simulations indicate that these applications include dynamic signal power and erbium-doped fiber amplifier (EDFA) gain equalization with a dynamic range of 12 dB, and interchannel amplified spontaneous emission (ASE) suppression by more than 20 dB; optical add/drop multiplexing with passband-flattened channels and suppressions of 15 dB; and dynamic dispersion compensation of up to /spl plusmn/300 ps/nm.

Dynamic range compressor-limiter and low-level expander with look-ahead for maximizing and stabilizing voice level in telecommunication applications

Abstract: A voice signal processing system with multiple parallel control paths, each of which address different problems, such as the high peak-to-RMS signal ratios characteristic of speech, wide variations in RMS speech levels, and high background noise levels. Different families of input-output control curves are used simultaneously to achieve efficient peak limiting and dynamic range compression as well as low-level dynamic expansion to prevent excessive amplification of background noise. In addition, a delay in the audio path relative to the control path makes it possible to employ an effective look-ahead in the control path, with FIR filtering smoothing-matched to the look-ahead. Digital domain peak interpolators are used for estimating the peaks of the input signal in the continuous time domain.

Comparison of linear gain and wide dynamic range compression hearing aid circuits II: aided loudness measures.

Abstract: Objectives:The goal of this study was to test the theoretical advantages of a single-channel wide dynamic range compression (WDRC) circuit fitted using the DSL method for increased dynamic range and normalized loudness growthDesign:Ten adolescents and young adults with moderate to severe sensorineu

100000-pixel, 120-dB imager in TFA technology

Abstract: A locally autoadaptive image sensor LARS II (Lokal-AutoadaptiveR Sensor) with 368/spl times/256 pixels was designed and fabricated in thin film on ASIC (TFA) technology. Every pixel contains an automatic shutter, made of 17 transistors and two capacitors on an area of 40/spl times/38.3 /spl mu/m/sup 2/, that adapts the integration time to the local intensity. This allows the capture and processing of scenes with extremely high dynamic range. For the amorphous detector system, local contrast and temperature stability are demonstrated to be excellent while the transient response is sufficient for imaging applications. Sample images shown in this paper verify the total dynamic range of 120 dB.

High frequency/high dynamic range CMOS VGA

Abstract: A novel CMOS variable gain amplifier (VGA) with high frequency and high dynamic range is proposed. The VGA has a controllable gain range of -50 dB-+50 dB which can be controlled by adjusting the external voltage as well as an enhanced operating frequency range up to 200 MHz. It is fabricated using 0.35 /spl mu/m CMOS technology and has a core area of 580/spl times/660 /spl mu/m.

The performance of a CCD digital autoradiography imaging system.

Abstract: Autoradiography is a widely used technique for imaging trace quantities of radioactivity within biological samples, conventionally using photographic film. This method produces images with high spatial resolution, but it suffers from very low sensitivity and poor dynamic range. Digital autoradiography systems with greatly improved sensitivity and linearity are commercially available, but the spatial resolution is usually much less than that achieved using film. We report here the design, construction and characterization of a novel digital autoradiography system based on scientific-grade charged coupled devices (CCDs). Images of x-ray and β emissions from radionuclides commonly used in autoradiography show that the system can perform high-speed quantitative imaging with a spatial resolution of ~30 µm. Using a frame by frame acquisition method the dynamic range is shown to be at least three orders of magnitude. The absolute detection efficiency is comparable to the best of the currently available digital systems. CCD images of 125I and 14C radioisotope distributions in tissue samples are superior to the equivalent film images and have been acquired in 1-10% of the time.

Demonstration of an all-digital 7-bit 33-channel photonic delay line for phased-array radars.

Abstract: A 7-bit multichannel photonic delay line for phased-array antenna control is demonstrated Multichannel (33-pixel) ferroelectric liquid-crystal (FLC) devices are used as polarization rotation elements, and polarization beam-splitter cubes are used as polarization elements that route the optical signals to different paths The controller is remotely fed by a unique fiber-optic-array design that uses gradient-index lens collimators for the input single-mode polarization-maintaining fibers The optical signal is collected by a similar fiber array that uses multimode fibers for improved coupling efficiency Photonic delay-line (PDL) design issues such as multiport assemblies, multipixel FLC designs, and delay-line architectures are discussed Furthermore, various PDL parameters are examined High electrical isolation numbers are obtained for both the within-channel leakage noise (eg, less than -70 dB) and the interchannel cross talk (eg, less than -90 dB) Optical and electrical insertion loss is examined for the PDL as well as for the overall system A high-compression dynamic range of 149 dB · Hz and a spurious free dynamic range of 105 dB · Hz2/3 are presented

Method and system of noise removal for a sparsely sampled extended dynamic range image sensing device

Abstract: A method of removing noise from a sparsely sampled extended dynamic range image produced by a sparsely sampled extended dynamic range image sensing device having fast photosites with a predetermined response to a light exposure for producing fast pixel values and slow photosites with a slower response to the same light exposure for producing slow pixel values, includes the steps of: providing a sparsely sampled extended dynamic range digital image having fast and slow pixel values; using a noise filter method to remove noise from the sparsely sampled extended dynamic range digital image by using only slow pixel values to generate slow noise reduced pixel values and using only fast pixel values to generate fast noise reduced pixel values; and combining the slow noise reduced pixel values and the fast noise reduced pixel values to generate a noise reduced sparsely sampled digital image.

3D Imaging: Wave Front Sensing Utilizing a Birefringent Crystal

Abstract: Utilizing a rotatable thin birefringent crystal and two polarizers, the three-dimensional (3D) wave front of any light wave can be measured conveniently. In first experiments phase-front distortions as small as 15 mm are detected with a dynamic range of 3 mm and a spatial resolution of 50 mm. Such a dynamic range and spatial resolution exceed the performance of conventional wave front sensors of, e.g., the Shack-Hartmann type, significantly. Furthermore, the new system is rather insensitive against mechanical instabilities in opposition to interferometric and holographic techniques.

Dynamic‐range limitations of intensified CCD photon‐counting detectors

Abstract: The bright limit to the dynamic range of intensified CCD photon-counting detectors is governed by coincidence losses. In this paper a theoretical analysis of the loss mechanisms is carried out and verified using laboratory data. For applications where the input source is stable, such as star field imaging from space, the theoretical dynamic-range curve can then be used for accurate quantification.

Wide dynamic range silicon diaphragm vacuum sensor by electrostatic servo system

Abstract: A wide dynamic range silicon diaphragm vacuum sensor by an electrostatic servo system and an electrical circuit for servo control have been made. In nonservo mode, i.e., when the sensor was used as a capacitive vacuum sensor, a linear characteristic between pressure and output voltage was obtained in the pressure range from 0.1 to 100 Pa. On the other hand, the square root of the servo voltage was proportional to the pressure in a wide pressure range from 0.1 to 530 Pa in servo mode. The servo mechanism is effective for widening the dynamic range of vacuum sensors.

XPAD, a new read-out pixel chip for X-ray counting

Abstract: Hybrid pixel detectors featuring a high signal to noise ratio, real 2 dimensional reconstruction and local intelligence, have now been demonstrated to be one of the most powerful trackers for high energy physics experiments. They have, therefore, gained interest in other physics fields and for medical applications. However, the conversion of pixel detectors from high energy physics to X-ray detection is not completely straightforward and new challenges appear. For example, high counting rates, wide dynamic ranges and low detection levels are required. "XPAD" (X-ray Pixel Chip with Adaptable Dynamics) is a novel concept of a pixel detector read-out chip especially developed for X-ray diffraction. This circuit, submitted in a 0.8 /spl mu/m CMOS technology, contains 600 square pixels distributed into 24 columns of 25 elements each. The analogue part, gathering 2 cascaded amplifiers, uses the automatic pole-zero cancellation technique in order to keep the baseline stable even at counting rate as high as 10/sup 7/ photons per second. A fast discriminator allows a detection level from 5 keV (1200 electrons) to 50 keV. A new read-out concept based on a special overflow mechanism has been implemented for infinite dynamic range purposes. This technique permits also data transport during acquisition and motion reconstruction provided by some level of time tagging.

Performance analysis of phoswich/APD detectors and low-noise CMOS preamplifiers for high-resolution PET systems

Abstract: An integrated 0.8-/spl mu/ CMOS charge-sensitive preamplifier previously designed for LSO/APD-based positron emission tomography (PET) systems has been further investigated for use with multicrystal/avalanche photodiode (APD) PET detectors. In addition to low-noise wide-band performance and power efficiency, high dynamic range and good signal-to-noise ratio over a broad range of shaping times are required to process the signals from crystals being used in phoswich detectors, which have a wide range of scintillation decay time and light output characteristics. The preamplifier equivalent noise charge (N/sub eq/) was measured as a function of input capacitance and amplifier-shaping time constant. The performance of the preamplifier was also assessed using APDs coupled to a variety of scintillators. Measurements were obtained at a preamplifier input-device current of 2 and 4 mA. The higher bias led to marginal improvements of the timing performance but had no effect on energy resolution. The very low noise of the preamplifier allows optimum timing performance to be obtained at lower APD gain and improves crystal identification by pulse shape discrimination with phoswich detectors.

Method for independent dynamic range control

Abstract: Different dynamic range control values are applied to the 2-channel and m-channel outputs without repeating the inverse transform of the audio samples. First, m-channel dynamic range control values are applied to audio samples in the frequency domain (“frequency samples” or “frequency coefficients”). The frequency samples are then inverse transformed to generate audio samples in the time domain (“time samples”). The time samples are duplicated to two sets where the 2-channel dynamic range control values are applied to one set of time samples. 2-channel dynamic range control values include 2-channel final scales that, when multiplied with the first set of time samples, at least partially remove the effects of the m-channel dynamic range control and readjust the dynamic range for 2-channel output. The first set and the second set are then windowed. Thus, independent dynamic range control for the m-channel output and the 2-channel output are achieved without repeating the inverse transform, which is computational and/or memory intensive.

Experimental investigation at 10 Gb/s of the noise suppression capabilities in a pass-through configuration in SOA-based interferometric structures

Abstract: We experimentally investigate a pass-through scheme for all-optical noise suppression in a SOA-based interferometric structure at 10 Gb/s. An input power dynamic range of /spl sim/8 dB as well as a noise suppression capability of /spl sim/4.5 dB has been demonstrated. Furthermore, the transmission properties have been investigated showing a small pre-amplified penalty of /spl sim/0.3 dB after transmission over 31 km of standard single mode fiber.

Wideband channel sounding dynamic range using a sliding correlator

Abstract: The sliding correlator is widely used in channel sounders employed to measure the impulse response of the radio channel. Cross-correlation of two pseudonoise (PN) sequences with slightly different chip rates gives the channel impulse response. However, the slight difference in chip rates creates various distortions in the cross-correlation response, compared with the autocorrelation function of the same PN sequence. The most significant of these is a reduction in dynamic range. Using a novel algorithm, this paper quantifies the dynamic range as a function of N (the PN sequence length) and k (the time scaling factor, or the inverse of the fractional difference in chip rates), allowing a sliding correlator with up to N=2047, and k=100000 to be fully simulated. A design method based on the results presented in the paper is described.

A 1 V 1 mW digital-audio /spl Delta//spl Sigma/ modulator with 88 dB dynamic range using local switch bootstrapping

Abstract: A 1 V, 1 mW, 14 bit delta-sigma modulator in a standard CMOS 0.35-/spl mu/m technology is presented. A modified symmetrical bootstrapped switch is used in order to allow rail-to-rail signal switching. A single-loop third-order topology with an oversampling ratio of 100 achieves a dynamic range of 88 dB, a peak SNR of 87 dB and a peak SNDR of 85 dB in a signal bandwidth of 25 kHz.

Apparatus and method for expanding dynamic range in image processing system

Abstract: A dynamic range expanding apparatus in an image processing system, capable of more stably expanding dynamic visual range by removing motion blurring caused when images each having different exposure levels are combined, and a dynamic range expanding method, are provided. In this apparatus, a video multiplexing unit divides a digital video signal, which is converted from an analog video signal output by a charged coupled device, into an over-exposed video signal and an under-exposed video signal having different exposure levels. A motion correction unit corrects the moving part of an excessively-exposed video according to the amount of movement of an image acquired by the charged coupled device, using the output of the video multiplexing unit. A video output unit interpolates a dark part of a resultant signal corrected by the motion correction unit and a bright part of the under-exposed video signal using a luminance weight produced from the under-exposed video signal, and outputs the interpolated result as an expanded video signal having an expanded dynamic range.

Segmented mapping converter system and method

Abstract: Partitioned signal processing systems and methods featuring substantial flexibility and cost effective implementations is presented. The architecture of the systems and methods of the present invention can be divided into a plurality of modules having manual and automatic methods. The modules can be implemented by both analog and digital designs, can be designed together or dispersed across a network, and can be dynamically reconfigured via software. These modules include a user interface, an input signal processor, an adaptive compander, a volume control and pre-mixer, an output signal processor, a noise extractor, a transform engine, a statistical analysis engine, and a calibrator/annunciator. The manual methods include methods to establish dynamic range mapping. The automatic methods include methods to establish dynamic range mapping, a method to maintain dynamic range mapping, a method to adjust dynamic range mapping in the presence of noise, and a method for intelligent volume control.

Vertically integrated sensors for advanced imaging applications

Abstract: A thin film on ASIC (TFA) image sensor is fabricated depositing an amorphous silicon thin-film detector onto a CMOS ASIC. With regards to advanced imaging systems, TFA provides enhanced performance and more flexibility than conventional technologies. Extensive on-chip signal processing is feasible, as well as small pixels for high resolution imagers. Two new TFA imager prototypes have recently been fabricated. High-resolution image sensor (HIRISE II) with 1024/spl times/128 pixels is an active pixel sensor suited for digital photography. Local autoadaptiver sensor (LARS II) with 368/spl times/256 pixels splits the illumination information into two signals, thereby providing a dynamic range of more than 120 dB, as required by automotive applications. Both prototypes include correlated double sampling and double delta sampling for efficient suppression of fixed pattern noise.