Showing papers on "Dynamic range published in 2005"

Dynamic range in terahertz time-domain transmission and reflection spectroscopy

Abstract: We present a quantitative method for identification of the dynamic range of the detectable absorption coefficient in the analysis of transmission terahertz (THz) time-domain spectroscopy data. In transmission measurements the largest detectable absorption coefficient is determined by the dynamic range of the THz signals, whereas in reflection measurements the largest detectable absorption coefficient is determined by the scan-to-scan reproducibility of the signal.

Compressing and companding high dynamic range images with subband architectures

Abstract: High dynamic range (HDR) imaging is an area of increasing importance, but most display devices still have limited dynamic range (LDR). Various techniques have been proposed for compressing the dynamic range while retaining important visual information. Multi-scale image processing techniques, which are widely used for many image processing tasks, have a reputation of causing halo artifacts when used for range compression. However, we demonstrate that they can work when properly implemented. We use a symmetrical analysis-synthesis filter bank, and apply local gain control to the subbands. We also show that the technique can be adapted for the related problem of "companding", in which an HDR image is converted to an LDR image, and later expanded back to high dynamic range.

Dynamic range of nanotube- and nanowire-based electromechanical systems

Abstract: Nanomechanical resonators with high aspect ratio, such as nanotubes and nanowires are of interest due to their expected high sensitivity. However, a strongly nonlinear response combined with a high thermomechanical noise level limits the useful linear dynamic range of this type of device. We derive the equations governing this behavior and find a strong dependence [[proportional]dsqrt((d/L)[sup 5])] of the dynamic range on aspect ratio.

A wide dynamic range CMOS image sensor with multiple exposure-time signal outputs and 12-bit column-parallel cyclic A/D converters

Abstract: A wide dynamic range CMOS image sensor with a burst readout multiple exposure method is proposed. In this method, maximally four different exposure-time signals are read out in one frame. To achieve the high-speed readout, a compact cyclic analog-to-digital converter (ADC) with noise canceling function is proposed and arrays of the cyclic ADCs are integrated at the column. A prototype wide dynamic range CMOS image sensor has been developed with 0.25-/spl mu/m 1-poly 4-metal CMOS image sensor technology. The dynamic range is expanded maximally by a factor of 1791 compared to the case of single exposure. The dynamic range is measured to be 19.8 bit or 119 dB. The 12-bit ADC integrated at the column of the CMOS image sensor has DNL of +0.2/-0.8 LSB.

Scientific Reviews: Two-Detector System for Small-Angle Neutron Scattering Instrument

Abstract: Most of the objects of small-angle neutron scattering (SANS) experiments require the measurements of a studied sample in a wide range of momentum transfer (Q-range). Larger Q-range means more reliable determination of a model of the investigated material as well as higher accuracy of its calculated structural parameters. The dynamic range of SANS instruments is normally determined by the size of the detector, which is limited mainly by technical reasons and by the wavelength range of available thermal neutrons in the neutron beam. Even in the case of the largest detector (1 m2) at one of the best beam lines—the D22 instrument at ILL—the dynamic range is about 50. Usually the problem of the Qrange is solved by a sequence of measurements with the detector at different positions. However, it leads to considerable increase in the data acquisition time. Moreover, the problem becomes critical when it is necessary to study processes in real time, especially irreversible processes.

Methods and systems for dynamic range expansion

Abstract: Methods and systems for expanding the dynamic range of a system are provided. One method includes splitting fluorescent light emitted by a particle into multiple light paths having different intensities, detecting the fluorescent light in the multiple light paths with different channels to generate multiple signals, and determining which of the channels is operating in a linear range based on the multiple signals. The method also includes altering the signal generated by the channel operating in the linear range to compensate for the different intensities. Another method includes illuminating a particle in multiple illumination zones with light having different intensities and separately detecting fluorescent light emitted by the particle while located in the multiple illumination zones to generate multiple signals. The method also includes determining which of the signals is located in a linear range and altering the signal located in the linear range to compensate for the different intensities.

A 100 dB dynamic range CMOS image sensor using a lateral overflow integration capacitor

Abstract: The wide DR CMOS image sensor incorporates a lateral overflow capacitor in each pixel to integrate the overflow charges from the photodiode when it saturates. The 7.5/spl times/7.5 /spl mu/m/sup 2/ pixel, 1/3" VGA sensor fabricated in a 0.35 /spl mu/m 3M2P CMOS process achieves a 100 dB dynamic range with no image lag, 0.15 mV/sub rms/ random noise and 0.15 mV fixed pattern noise.

Optical vector network analyzer for single-scan measurements of loss, group delay, and polarization mode dispersion

Abstract: We present a method for measuring the complete linear response, including amplitude, phase, and polarization, of a fiber-optic component or assembly that requires only a single scan of a tunable laser source. The method employs polarization-diverse swept-wavelength interferometry to measure the matrix transfer function of a device under test. We outline the theory of operation to establish how the transfer function is obtained. We demonstrate the enhanced accuracy, precision, and dynamic range of the technique through measurements of several components.

Thermoreflectance based thermal microscope

Abstract: Thermal images of active semiconductor devices are acquired and processed in real time using visible light thermoreflectance imaging with 34mK sensitivity. By using a 16×16 alternating current coupled photodiode array with synchronous frequency domain filtering a dynamic range of 123dB is achieved for 1s averaging. Thus with a stable and higher power light source, fundamentally the camera can reach 6mK sensitivity over a submicron area. The number of pixels in the image is increased to 160×160 by multiple frame image enhancement and submicron spatial resolution is achieved. The photodiode array system has a maximum 40kHz frame rate and generates a synchronous trigger for recovery of the phase signal. Amplitude and phase images of the thermoreflectance signal for 50×50 micron square active SiGe based microcoolers are presented.

A digital pixel sensor array with programmable dynamic range

Abstract: This paper presents a digital pixel sensor (DPS) array employing a time domain analogue-to-digital conversion (ADC) technique featuring adaptive dynamic range and programmable pixel response The digital pixel comprises a photodiode, a voltage comparator, and an 8-bit static memory The conversion characteristics of the ADC are determined by an array-based digital control circuit, which linearizes the pixel response, and sets the conversion range The ADC response is adapted to different lighting conditions by setting a single clock frequency Dynamic range compression was also experimentally demonstrated This clearly shows the potential of the proposed technique in overcoming the limited dynamic range typically imposed by the number of bits in a DPS A 64 /spl times/ 64 pixel array prototype was manufactured in a 035-/spl mu/m, five-metal, single poly, CMOS process Measurement results indicate a 100 dB dynamic range, a 41-s mean dark time and an average current of 16 /spl mu/A per DPS

Continuous-wave terahertz system with a 60 dB dynamic range

Abstract: We have developed a high-performance continuous-wave terahertz imaging system based on photomixing. The emitter and detector are driven by compact, unstabilized, single-mode diode lasers. The all-optoelectronic, homodyne detection scheme yields both amplitude and phase information, and with careful optimization and matching of both emitter and receiver, a 60 dB dynamic range, at 0.53 THz, can be routinely achieved. This replicates the performance of established pulsed THz imagers at this frequency. (c) 2005 American Institute of Physics.

A 106-dB SNR hybrid oversampling analog-to-digital converter for digital audio

Abstract: An audio /spl Sigma//spl Delta/ analog-to-digital converter (ADC) with the loop filter implemented by continuous-time (CT) and discrete-time (DT) circuits is presented. A tuning circuit is used to compensate for changes in the RC product due to process skew, power supply, temperature and sampling rate variation. To eliminate errors caused by inter-symbol interference (ISI) in the CT feedback DAC, a return-to-zero (RTZ) switching scheme is applied on the error current of the CT integrator. The converter is fabricated in a 0.35-/spl mu/m CMOS process, and achieves 106-dB dynamic range, -99-dB THD+N.

High dynamic range images from low dynamic range images

Abstract: A method for displaying an image includes receiving an image having a first luminance dynamic range and modifying the image to a second luminance dynamic range free from being based upon other images, where the second dynamic range is greater than the first dynamic range. The modified image is displayed on a display.

A 0.6-V 82-dB delta-sigma audio ADC using switched-RC integrators

Abstract: A 0.6-V 2-2 cascaded audio delta-sigma ADC is described. It uses a resistor-based sampling technique which achieves high linearity and low-voltage operation without subjecting the devices to large terminal voltages. A low-distortion feed-forward topology combined with nonlinear local feedback results in enhanced linearity by reducing the sensitivity to opamp distortion, and allows increased input amplitude, resulting in higher SNDR. The modulator achieves 82-dB dynamic range and 81-dB peak SNDR in the A-weighted audio signal bandwidth with an OSR of 64. The total power consumption of the modulator is 1 mW from a 0.6-V supply. The prototype occupies 2.9 mm/sup 2/ using a 0.35-/spl mu/m CMOS technology.

Instrumentation and calibration methods for the multichannel measurement of phase and amplitude in optical tomography

Abstract: In this article, we describe the multichannel implementation of an intensity modulated optical tomography system developed at Helsinki University of Technology. The system has two time-multiplexed wavelengths, 16 time-multiplexed source fibers and 16 parallel detection channels. The gain of the photomultiplier tubes (PMTs) is individually adjusted during the measurement sequence to increase the dynamic range of the system by 104. The PMT used has a high quantum efficiency in the near infrared (8% at 800nm), a fast settling time, and low hysteresis. The gain of the PMT is set so that the dc anode current is below 80nA, which allows the measurement of phase independently of the intensity. The system allows measurements of amplitude at detected intensities down to 1fW, which is sufficient for transmittance measurements of the female breast, the forearm, and the brain of early pre-term infants. The mean repeatability of phase and the logarithm of amplitude (lnA) at 100MHz were found to be 0.08° and 0.004, res...

A photon counting CdTe gamma- and X-ray camera

Abstract: A photon counting CdTe imaging camera suitable for gamma- and X-ray detection has been developed and tested. The current full active imaging area of the gamma/X-ray camera covers 44×44 mm 2 . The camera is built of eight individual detector hybrids each consisting of a pixelated CdTe detector with dimensions of 22×11 mm 2 and solder bump-bonded to a photon counting custom-designed application specific integrated circuit (ASIC). The ASICs are realized in a mixed signal, 0.35 μm 4 metal 2 poly CMOS process. The effective pixel size (image pixel pitch) is 0.5 mm. To enable higher count rate imaging and to achieve better position resolution in X-ray CT scanning each pixel is divided both on the CdTe detector and on the ASIC into two sub-pixels with dimensions 0.25×0.5 mm 2 . Every pixel circuit has two preamps each connected to one sub-pixel and feeding signal to a separate comparator. The digital pulses of the two distinct comparators are recorded by one common 8-bit counter. The amplifier offsets can be adjusted individually with 3-bit accuracy to compensate for process mismatch. A similar 3-bit gain tuning common to the two amplifiers in one pixel circuit is also implemented. A globally tuneable threshold voltage generated externally with high accuracy is used for energy discrimination. The camera can be operated both in the real time imaging mode with a maximum speed of 100 frames/s and in the accumulation mode with user adjustable counting time. Experimental data collected from a fully operational eight hybrid gamma/X-ray camera is presented and compared to simulated data. The camera exhibits excellent sensitivity and a dynamic range of 1:14,000,000. A sharp line spread function indicates the spatial resolution to be limited only by the pixel size (0.5 mm). A single pixel energy resolution of FWHM 4.7 keV at 122 keV (3.9%) was determined from measured 57 Co spectra. The peak width of the spectrum combined from all pixels was somewhat larger due to calibration inaccuracy. The photopeak efficiency was estimated from 241 Am spectra to be 60%. The developed gamma/X-ray camera is intended for back scattering imaging and as a building block in future nuclear medicine and CT scanning systems and promises highly improved performance in these applications in comparison to conventional technology.

Readout technique for increasing or maintaining dynamic range in image sensors

Abstract: The apparatus and method provide a readout technique and circuit for increasing or maintaining dynamic range of an image sensor. The readout technique and circuit process each pixel individually based on the magnitude of the readout signal. The circuit includes a gain amplifier amplifying the readout analog signal, a level detection circuit for determining the signal's magnitude, a second gain amplifier applying a gain based on the signal magnitude and an analog-to-digital converter digitizing the signal and a circuit for multiplying or dividing the signal. The method and circuit allow for a lower signal-to-noise ratio while increasing the dynamic range of the imager.

Programmable input range adc

Abstract: A programmable input voltage range analog-to-digital converter in which a split gate oxide process allows the use of high voltage (±15 volt) switches on the same silicon substrate as standard sub-micron 5 volt CMOS devices. With this process, the analog input voltage can be sampled directly onto one or more sampling capacitors without the need for prior attenuation circuits. By only sampling on a given ratio of the sampling capacitors, the analog input can be scaled or attenuated to suit the dynamic range of a subsequent ADC. In the system of the present invention, the sampling capacitor can be the actual capacitive redistribution digital-to-analog converter (CapDAC) used in a SAR ADC itself, or a separate capacitor array. By selecting which bits of the CapDAC or separate sampling array to sample on, one can program the input range. Once the analog input signal has been attenuated to match the allowed dynamic range of the SAR converter, traditional SAR techniques can be used to convert the input signal to a digital word. Other conversion technologies, such as sigma-delta and pipeline, can also be used in conjunction with the inventive system.

CMOS active pixel sensor with improved dynamic range and method of operation

Abstract: A CMOS imaging array includes a plurality of individual pixels arranged in rows and columns. Each pixel is constructed the same and includes a photodetector (e.g., photodiode) receiving incident light and generating an output. A first, relatively lower gain, wide dynamic range amplifier circuit is provided responsive to the output of the photodetector. The first circuit is optimized for a linear response to high light level input signals. A second, relatively higher gain, lower dynamic range amplifier circuit is also provided which is responsive to the output of the photodetector. The second circuit is optimized to provide a high signal to noise ratio for low light level input signals. A first output select circuit is provided for directing the output of the first circuit to a first output multiplexer. A second output select circuit is provided for directing the output of the second circuit to a second output multiplexer. Thus, separate outputs of the first and second circuits are provided for each of the individual pixel sensors of the CMOS imaging array. Alternative embodiments incorporate two ore more photodetectors and two or more amplifier circuits and output select circuits. Three photodetectors and three amplifier circuits are useful for an embodiment where the sensor includes a three-color filter matrix.

On the dynamic range of optical delay lines based on coherent atomic media

Abstract: We show that the dynamic range of delay lines based on slow light propagation in atomic coherent media is restricted due to absorptive, dispersive, and nonlinear properties of the media. We compare the electro-magnetically induced transparency based delay lines with optical fiber and resonator delays.

Hysteresis controller with constant switching frequency

Abstract: Switch mode audio power amplifiers are showing up on market in still greater numbers because of advantages in form of high efficiency and low total system cost, especially for high power amplifiers. Several different modulator topologies have been made, ranging from standard PWM to various self-oscillating and digital modulators. Performance in terms of low distortion, noise and dynamic range differs significantly with the modulator topology used. Highest system performance is generally achieved with analog modulators made as a modulator loop including at least the power stage of the amplifier, because of benefits from continuous time operation and non-quantized resolution. This type of modulator uses no external carrier signal, and is called self-oscillating modulators. The work presented in this paper refers to switch mode audio power amplifier, but can be used within a wide range of DC-DC or DC-AC converters as well.

A sensitivity and linearity improvement of a 100 dB dynamic range CMOS image sensor using a lateral overflow integration capacitor

Abstract: In a CMOS image sensor featuring a lateral overflow capacitor in a pixel, which integrates the overflowed charges from a frilly depleted photodiode during the same exposure, the sensitivity in non-saturated signal and the linearity in saturated overflow signal have been improved by introducing a new pixel circuit and its operation. A 1/3" VGA color CMOS image sensor has fabricated through 0.35 /spl mu/m 2P3M CMOS process results in a 100 dB dynamic range characteristic, with improved sensitivity and linearity.

In-band OSNR and chromatic dispersion monitoring using a fibre optical parametric amplifier.

Abstract: This paper presents an all-optical, in-band optical signal-to-noise ratio (OSNR) and chromatic dispersion monitor. We demonstrate monitoring over the 1 nm bandwidth of our signal, which is a 10 GHz pulse train of 8.8 ps pulses. The monitor output power, as measured on a slow detector, has a 1.9 dB dynamic range when the signal OSNR is varied by 20 dB, and a 1.6 dB dynamic range when ±150 ps/nm of chromatic dispersion is applied. Cascaded four-wave mixing occurring in the optical parametric amplifier provides the nonlinear power transfer function responsible for the monitoring. An analysis using the signals’ probability density functions show that the nonlinear power transfer function provides preferential gain to clean undispersed pulses when compared to noisy and/or dispersed pulses. Our analysis includes a consideration of the applicability of the device to high duty cycle systems, and simulations on monitoring of a 40 Gb/s pulse train with a 50% duty cycle.

A CMOS image sensor with programmable pixel-level analog processing

Abstract: A prototype of a 34 /spl times/ 34 pixel image sensor, implementing real-time analog image processing, is presented. Edge detection, motion detection, image amplification, and dynamic-range boosting are executed at pixel level by means of a highly interconnected pixel architecture based on the absolute value of the difference among neighbor pixels. The analog operations are performed over a kernel of 3 /spl times/ 3 pixels. The square pixel, consisting of 30 transistors, has a pitch of 35 /spl mu/m with a fill-factor of 20%. The chip was fabricated in a 0.35 /spl mu/m CMOS technology, and its power consumption is 6 mW with 3.3 V power supply. The device was fully characterized and achieves a dynamic range of 50 dB with a light power density of 150 nW/mm/sup 2/ and a frame rate of 30 frame/s. The measured fixed pattern noise corresponds to 1.1% of the saturation level. The sensor's dynamic range can be extended up to 96 dB using the double-sampling technique.

10-GHz bandwidth RF spectral analyzer with MHz resolution based on spectral hole burning in Tm/sup 3+/:YAG

Abstract: We demonstrate the first 10-GHz instantaneous bandwidth radio-frequency spectrum analyzer based on spectral hole burning in Tm/sup 3+/:YAG. It exhibits 10 000 frequency channels and a resolution better than 1 MHz. Thanks to the fast and linear chirping capabilities of the laser used, it has a potential 100% probability of interception and a response time in the millisecond range. Its linear dynamic range of 16 dB is presently essentially limited by the modest amount of optical power available and can be further improved.

Signal conditioning algorithms for enhanced tactical sensor imagery

Abstract: In tactical sensor imagery there always is a need for less noise, higher dynamic range and more resolution. Although recent developments lead to better and better Focal Plane Array (FPA) camera systems, modern infrared FPA camera system are still hindered by non-uniformities, a limited signal-to-noise ratio and a limited spatial resolution. The current availability of fast and inexpensive digital electronics allows the use of advanced reeal-time signal processing to address the need for better image quality. We will present results of signal-conditioning algorithms, which achieve significant better performance with regard to the FPA problems given above. Scene-Based Non-Uniformity Correction (SBNUC) can provide an online correction of existing and evolving fixed-pattern noise. Dynamic Super Resolution (DSR) improves the signal-to-noise ratio, while simultaneously improving spatial resolution. The signal-conditioning algorithms can handle camera movements, high temporal noise levels, high fixed-pattern noise levels and large moving objects. The Local Adaptive Contrast Enhancement (LACE) algorithm does effectively compress the 10, 12 or 14 bits dynamic range of the corrected imagery towards a 6 to 8 bits dynamic range for the display system, without the loss of image details. In this process, it aims at keeping all information in the original image visible. We will show that the SBNUC, DSR, mosaic generation, and LACE can be integrated in a very natural way resulting in excellent all-round performance of the signal-conditioning suite. We will demonstrate the application of SBNUC, DSR, Mosaicking and LACE for various imaging systems, showing significant improvement of the image quality for several imaging conditions.

A 19.5b dynamic range CMOS image sensor with 12b column-parallel cyclic A/D converters

Abstract: A CMOS image sensor with 117 dB DR is demonstrated in a 025 /spl mu/m CMOS technology through merging of multiple exposures A 12b cyclic ADC with integrated noise canceling is implemented in the column of the image sensor and achieves a DNL of +04/-08 LSB

Micro-optical sensor system for pressure, acceleration, and pressure gradient measurements

Abstract: A micro-optical fiber tip based sensor system for pressure, acceleration, and pressure gradient measurements in a wide bandwidth, the design of which allows for multiplexity of the input side of the system is based on micro-electromechanical fabrication techniques. The optical portion of the system is based on low coherence fiber-optic interferometry techniques which has a sensor Fabry-Perot interferometer and a read-out interferometer combination that allows a high dynamic range and low sensitivity to the wavelength fluctuation of the light source. A phase modulation and demodulation scheme takes advantage of the Integrated Optical Circuit phase modulator and multi-step phase-stepping algorithm for providing high frequency and real time phase signal demodulation. The system includes fiber tip based Fabry-Perot sensors each of which has a diaphragm that is used as a transducer.

An optimal tone reproduction curve operator for the display of high dynamic range images

Abstract: We present a new tone mapping method for the display of high dynamic range images in low dynamic range devices. We formulate high dynamic range image tone mapping as an optimisation problem. We introduce a two-term cost function, the first term favours linear scaling mapping, the second term favours histogram equalisation mapping, and jointly optimising the two terms optimally maps a high dynamic range image to a low dynamic range image. We control the mapping results by adjusting the relative weightings of the two terms in the objective function. We also present a fast and simple implementation for solving the optimisation problem. We present results to demonstrate that our method works very effectively.