Showing papers on "Dynamic range published in 2008"

A 128 $\times$ 128 120 dB 15 $\mu$ s Latency Asynchronous Temporal Contrast Vision Sensor

Abstract: This paper describes a 128 times 128 pixel CMOS vision sensor. Each pixel independently and in continuous time quantizes local relative intensity changes to generate spike events. These events appear at the output of the sensor as an asynchronous stream of digital pixel addresses. These address-events signify scene reflectance change and have sub-millisecond timing precision. The output data rate depends on the dynamic content of the scene and is typically orders of magnitude lower than those of conventional frame-based imagers. By combining an active continuous-time front-end logarithmic photoreceptor with a self-timed switched-capacitor differencing circuit, the sensor achieves an array mismatch of 2.1% in relative intensity event threshold and a pixel bandwidth of 3 kHz under 1 klux scene illumination. Dynamic range is > 120 dB and chip power consumption is 23 mW. Event latency shows weak light dependency with a minimum of 15 mus at > 1 klux pixel illumination. The sensor is built in a 0.35 mum 4M2P process. It has 40times40 mum2 pixels with 9.4% fill factor. By providing high pixel bandwidth, wide dynamic range, and precisely timed sparse digital output, this silicon retina provides an attractive combination of characteristics for low-latency dynamic vision under uncontrolled illumination with low post-processing requirements.

Automatic High-Dynamic Range Image Generation for Dynamic Scenes

Abstract: Automatic high-dynamic range image generation from low- dynamic range images offers a solution to conventional methods, which require a static scene. The method consists of two modules: a camera-alignment module and a movement detector, which removes the ghosting effects in the HDRI created by moving objects.

High dynamic range image sensor with reduced line memory for color interpolation

Abstract: An image sensor has an array of pixels organized into a row and column format. Pixels are read out in a line-by-line sequence and buffered in a line image buffer. An extended dynamic range is supported by varying a column exposure time according to a periodic sequence. As a result, the pixel exposure times vary within each row. A high dynamic range is generated by combining pixel data of adjacent pixels within the same row that are of the same filter type but having different exposure times. Color interpolation is performed on the combined line data.

Single molecule electronics: increasing dynamic range and switching speed using cross-conjugated species.

Abstract: Molecular electronics is partly driven by the goal of producing active electronic elements that rival the performance of their solid-state counterparts, but on a much smaller size scale. We investigate what constitutes an ideal switch or molecular device, and how it can be designed, by analyzing transmission plots. The interference features in cross-conjugated molecules provide a large dynamic range in electron transmission probability, opening a new area for addressing electronic functionality in molecules. This large dynamic range is accessible through changes in electron density alone, enabling fast and stable switching. Using cross-conjugated molecules, we show how the width, depth, and energetic location of the interference features can be controlled. In an example of a single molecule transistor, we calculate a change in conductance of 8 orders of magnitude with an applied gate voltage. Using multiple interference features, we propose and calculate the current/voltage behavior of a molecular rectifier with a rectification ratio of >150,000. We calculate a purely electronic negative differential resistance behavior, suggesting that the large dynamic range in electron transmission probability caused by quantum interference could be exploited in future electronic devices.

An asynchronous time-based image sensor

Abstract: In this paper we propose a fully asynchronous, time- based image sensor, which is characterized by high temporal resolution, low data rate (near complete temporal redundancy suppression), high dynamic range, and low power consumption. Autonomous pixels asynchronously communicate the detection of relative changes in light intensity, and the time from change detection to the threshold crossing of a photocurrent integrator, so encoding the instantaneous pixel illumination shortly after the time of a detected change. The chip is being implemented in a standard 0.18 mum CMOS process and measures less than 10times8 mm2 at 304times240 pixel resolution.

Dynamic Backlight Gamma on High Dynamic Range LCD TVs

Abstract: A high dynamic range liquid crystal display (HDR-LCD) can enhance the contrast ratio of images by utilizing locally controlled dynamic backlight. We studied the HDR-LCD as a dual-panel display: a backlight module and a liquid crystal (LC) cell. As the gamma of the LC signal, the backlight module was also endowed with a gamma function to control the contrast ratio of HDR images. The inverse of a mapping function (IMF) method proposed as a dynamic gamma mapping curve for the backlight module, has been demonstrated to further improve in HDR image quality. By implementing the IMF method on a HDR-LCD TV with 88 backlight zones, the image contrast ratio can reach while maintaining high brightness, clear image detail, and an average power reduction of 30%.

A Broadband CMOS Amplitude Detector for On-Chip RF Measurements

Abstract: This paper presents a CMOS RF amplitude detector as a practical integrated test device and demonstrates its application for on-chip testing. The proposed circuit performs full-wave rectification and generates a dc voltage proportional to the amplitude of an RF signal over a wide frequency range. The design considerations and analysis of operation for the employed class-AB rectifier are described. Fabricated in a standard 0.35-mum CMOS process, the RF detector uses only 0.031 of area and presents an equivalent input capacitance of 13 fF. Measurements show that this RF test device has a detection dynamic range of 30 dB from 900 MHz to 2.4 GHz. Experimental results for the application of the RF amplitude detector in the built-in measurement of the gain and compression of a 1.6-GHz low-noise amplifier fabricated in the same chip are also presented.

A 15-bit Linear 20-MS/s Pipelined ADC Digitally Calibrated With Signal-Dependent Dithering

Abstract: Pseudo-random dithers have been used to measure capacitor mismatch and opamp gain errors of the pipelined analog-to-digital converter (ADC) in background and to calibrate them digitally. However, this error measurement suffers from signal range reduction and long signal decorrelation time. A signal-dependent dithering scheme allows the injection of a large dither without sacrificing the signal range and shortens the signal decorrelation time. A 1.5-bit multiplying digital-to-analog converter (MDAC) stage is modified for signal-dependent dithering with two additional comparators, and its capacitor mismatch and gain errors are measured and calibrated as one error. When sampled at 20 MS/s, a 15-bit prototype ADC achieves a spurious-free dynamic range of 98 dB with 14.5-MHz input and a peak signal-to-noise plus distortion ratio of 73 dB with 1-MHz input. Integral nonlinearity is improved from 25 to 1.3 least significant bits (LSBs) after calibrating the first six stages. The chip is fabricated in 0.18-mu CMOS process, occupies an active area of 2.3 x 1.7 mm2 , and consumes 285 mW at 1.8 V.

Magnetometry based on nonlinear magneto-optical rotation with amplitude-modulated light

Abstract: We report on an all-optical magnetometric technique based on nonlinear magneto-optical rotation with amplitude-modulated light. The method enables sensitive magnetic field measurements in a broad dynamic range. We demonstrate the sensitivity of 4.3×10−9G∕Hz at 10mG and the magnetic field tracking in a range of 40mG. The fundamental limits of the method sensitivity and factors determining current performance of the magnetometer are discussed.

Time-warp correction and calibration in photonic time-stretch analog-to-digital converter

Abstract: We show how time warps caused by nonuniform wavelength-to-time mapping in the photonic time-stretch analog-to-digital converter (ADC) can be digitally measured and removed. This is combined with digital correction of wavelength-dependent Mach-Zehnder modulator (MZM) bias offset to attain a 10 GHz bandwidth digitizer with >7 effective bits of resolution and 52 dB spur-free dynamic range. To the best of our knowledge, this is the highest resolution ADC in 10 GHz bandwidth range, with at least 1 order of magnitude higher signal-to-noise ratio than ever achieved. We also demonstrate concatenation of 30 wavelength interleaved time segments with high fidelity on the path to achieving continuous time operation.

Solid-state image pickup device and method

Abstract: A solid-state image pickup device and method are provided. The device can not only operate with a wide dynamic range but it also allows the user to switch the dynamic range corresponding to the photographic scene, and its operating method. Plural pixels, each of which has a photodiode, a transfer transistor, a floating diffusion region, an additional capacitance element, a capacitance coupling transistor, and a reset transistor, are integrated in an array on a semiconductor substrate. The capacitance of such floating diffusion region is less than that of such photodiode. A first signal S1 obtained by transferring part or all of the photoelectric charge accumulated in such photodiode PD to such floating diffusion region FD or a second signal S1+S2 obtained by transferring all of the photoelectric charge accumulated in such photodiodes to the potential obtained by coupling such floating diffusion region and such additional capacitance element CS is output to all of the pixels.

An efficient high-resolution 11-bit noise-shaping multipath gated ring oscillator TDC

Abstract: An 11-bit, 50-Msps time-to-digital converter (TDC) using a multipath gated ring oscillator (GRO) with 6 ps of delay per stage achieves low power (2.2 to 21 mW) and small area of 160times260 mum in 0.13 mum CMOS. The structure also achieves first order noise shaping of the GRO quantization and mismatch noise; the resulting TDC error integrates to <100 fs (rms) in a 1 MHz bandwidth to achieve dynamic range of over 90 dB with no calibration required.

Imaging apparatus, imaging method, integrated circuit, and storage medium

Abstract: An imaging apparatus captures a large dynamic range image of a scene including a backlit person with a blue sky background in a manner that the person's face has an appropriate luminance level without saturating the background sky. An imaging unit obtains analogue image signals through exposure control that prevents a highlight from being saturated, an A/D converter converts the analogue image signals to digital image signals, and a signal processing unit linearly increases the dynamic range of the digital image signals. The image signals with the increased dynamic range are nonlinearly compressed to have a dynamic range of 100% or less through nonlinear dynamic range compression that intensively compresses a highlight portion. The imaging apparatus with this structure first increases the dynamic range of an image and efficiently compresses the increased large dynamic range of the image.

High-dynamic-range single-shot cross-correlator based on an optical pulse replicator.

Abstract: The operation of a single-shot cross-correlator based on a pulse replicator is described. The correlator uses a discrete sequence of sampling pulses that are nonlinearly mixed with the pulse under test. The combination of a high reflector and partial reflector replicates an optical pulse by multiple internal reflections and generates a sequence of spatially displaced and temporally delayed sampling pulses. This principle is used in a cross-correlator characterizing optical pulses at 1053 nm. A dynamic range higher than 60 dB is obtained over a temporal range larger than 200 ps.

High Dynamic Range Imaging by Fusing Multiple Raw Images and Tone Reproduction

Abstract: This paper presents an integrated color imaging system for taking images in extremely high dynamic range scenes. The system first fuses several differently exposed raw images to acquire more intensity information. The effective dynamic range of the image raw data can be extended to 256 times if five differently exposed images are fused. Then it runs edge detection iterations to extract the image details in different luminance levels. The proposed tone reproduction algorithm equalizes the histogram of the extracted fine edges which tends to assign larger dynamic range for highly populated regions. Finally, the local contrast enhancement is performed to further refine the image details. The experimental results show that the proposed high dynamic range imaging system has good performance on both tone and color reproduction.

Image sensor with high dynamic range imaging and integrated motion detection

Abstract: This disclosure describes: (1) two different schemes to enhance dynamic range, (2) a new motion detection scheme using in-pixel digital storage, and (3) the motion detection in high illumination for CMOS image sensors. The schemes may be implemented in a small pixel size and easily incorporated in simple column-level circuits for existing CMOS image sensor systems.

A 828μW 1.8V 80dB dynamic-range readout interface for a MEMS capacitive microphone

Abstract: A CMOS interface for a piston-type MEMS capacitive microphone is presented. It performs a capacitance-to-voltage conversion by bootstrapping the sensor through a voltage pre-amplifier, feeding a third-order sigma-delta modulator. The bootstrapping performs active parasitic compensation, improving the readout sensitivity by ~12 dB. The total current consumption is 460 uA at 1.8 V-supply. The digital output achieves 80 dBA-DR, with 63 dBA peak-SNR, using 0.35 um 2P/4M CMOS technology. The paper includes electrical and acoustic measurement results for the interface.

The performance of a fiber optic displacement sensor for different types of probes and targets

Abstract: A simple fiber optic displacement sensor is presented using a multimode plastic bundled fiber and the intensity modulation technique. The performance of the sensor is compared for different types of probes and targets. The probe with the largest receiving core diameter demonstrates the highest linearity range, and increasing the number of receiving cores increases the sensitivity of the sensor. With a stainless steel target and the concentric bundled fiber with 16 receiving fibers as a probe, the sensitivity of the sensor is found to be 0.0220 mV/μm over 150 to 550 μm range and – 0.0061 mV/μm over 1100 to 2000 μm range. The target with a higher reflectivity shows a higher sensitivity. The linearity range for the front slope is almost similar for all targets tested. However, for the back slope, lower reflectivity objects have a relatively higher linearity range with the highest range of 1600 μm being obtained using plastic and aluminum targets. The simplicity of the design, high degree of sensitivity, dynamic range, non-contact measurement and low cost of the fabrication make it suitable for applications in industries for position control and micro displacement measurement in the hazardous regions.

Constrained matched filtering for extended dynamic range and improved noise rejection for Shack-Hartmann wavefront sensing.

Abstract: We recently introduced matched filtering in the context of astronomical Shack-Hartmann wavefront sensing with elongated sodium laser beacons [Appl. Opt. 45, 6568 (2006)]. Detailed wave optics Monte Carlo simulations implementing this technique for the Thirty Meter Telescope dual conjugate adaptive optics system have, however, revealed frequent bursts of degraded closed loop residual wavefront error [Proc. SPIE 6272, 627236 (2006)]. The origin of this problem is shown to be related to laser guide star jitter on the sky that kicks the filter out of its linear dynamic range, which leads to bursts of nonlinearities that are reconstructed into higher-order wavefront aberrations, particularly coma and trifoil for radially elongated subaperture spots. An elegant reformulation of the algorithm is proposed to extend its dynamic range using a set of linear constraints while preserving its improved noise rejection and Monte Carlo performance results are reported that confirm the benefits of the method.

A 108 dB SNR, 1.1 mW Oversampling Audio DAC With A Three-level DEM Technique

Abstract: A low power audio oversampling SigmaDelta digital-to-analog converter (DAC) with a three-level (+1, 0,-1) dynamic-element-matching (DEM) technique and an inter-symbol interference-free (ISI) output stage is presented. Solutions for design challenges such as ISI, clock jitter sensitivity, and out-of-band noise are presented. The converter is fabricated in a 0.18 mum CMOS process, occupies 0.55 mm2, achieves 108 dB dynamic range, -98 dB THD + N while consumes a total of 1.1 mW per channel at 1.8 V supply.

A New Auto Exposure System to Detect High Dynamic Range Conditions Using CMOS Technology

Abstract: This paper proposes a new auto-exposure algorithm that can accurately detect high-contrast lighting conditions and improve the dynamic range of output images for a camera system. The proposed method calculates the difference between the mean value and the median value of the brightness level of captured images to estimate lighting conditions. After that, a multiple exposure mechanism is carried out to improve the details of output pictures. Simulation results show that the system works well with CMOS sensors used in mobile phones and surveillance cameras. Besides, the proposed algorithm is fast and simple and therefore can be fitted in most CMOS platforms that have limited capabilities.

Improved Digital-to-Analog Conversion Using Multi-Electrode Mach–Zehnder Interferometer

Abstract: An improved version of a digital-to-analog converter (DAC) based on a multi-electrode Mach-Zehnder interferometer (MZI) is presented and analyzed. The device described has superior performance regarding both linearity and dynamic range. The improvements are achieved by utilizing a special mapping method between the analog input and the digital sequence applied to the device, and by an optimized sectioning method for the electrodes. Further improvement in linearity is attained by allowing the number of electrodes M to be larger than the number of digitization bits N (M > N). An analytical and systematic method for performing the mapping and selecting the electrodes' sizes is explicitly described and shown to be optimal. A comparison of the proposed approach to previously reported biased MZI reveals that dynamic range and linearity are significantly improved which is translated to increased resolution and reduced quantization errors. It follows from the optimization process that quantization and nonlinearity errors can be reduced to any extent by appropriately increasing the number of electrodes.

A highly linear bulk-driven CMOS OTA for continuous-time filters

Abstract: In this paper we present a bulk-driven CMOS triode-based fully balanced operational transconductance amplifier (OTA) and its application to continuous-time filters. The proposed OTA is linearly tunable with the feature of low distortion and high output impedance. It can achieve wide input range without compromising large transconductance tuning interval. Using a 0.18 ¼m n-well CMOS process, we have implemented a third-order elliptic low-pass filter based on the proposed OTA. Both the simulation and measurement results are reported. The total harmonic distortion is more than -45 dB for fully differential input signals of up to 0.8 V peak---peak voltage. A dynamic range of 45 dB is obtained under the OTA noise integrated over 1 MHz.

Software-Defined Six-Port Radar Technique for Precision Range Measurements

Abstract: A software-defined radar measurement system on the basis of a six-port receiver technique is proposed and described in this paper. The system makes use of a hybrid scheme of two performance-complementary operating modes, namely, frequency-modulated continuous-wave (FMCW) and two-tone continuous-wave signals. Generally, the FMCW-based measurement technique is deployed to give an approximate range value of target while the two-tone continuous-wave (CW)-based measurement technique can accurately determine the range that may, however, be ambiguous. The six-port circuit is used for the receiver as a precision phase detector in two-tone CW function and at the same time as a mixer in FMCW function. Various waveforms are generated in direct digital synthesizers and processed by different algorithms in a digital signal processor. The switching between the frequency-modulated CW and two-tone CW functions is controlled by software to improve the resolution and ensure a reliable operation. A system prototype is designed and made for a C-band demonstration. The Schottky diodes used as power detectors in the six-port are calibrated so that they can be used beyond the square-law region, thus allowing a higher power level and a better dynamic range. Measured results validate the proposed software-defined platform and accurate range results are confirmed.

Pulse width modulation: A novel readout scheme for high energy photon detection

Abstract: In standard PET scintillation detection, the energy, timing, and location of the incoming photon are recovered using analog signal processing techniques The energy and location information are processed using an analog-to-digital (ADC) converter that samples an analog value that is proportional to the integral of the charge created by the scintillation event We propose to change the paradigm and modulate the width (rather than amplitude) of a digital pulse to be proportional to the integral of the charge created The analog value of the outgoing digital pulses is recovered by using a time-to-digital converter (TDC) in the back-end electronics, without the need for an ADC Note that in this new scenario the same TDC used to record the time of the event is used to recover the amplitude The main performance parameter that must be optimized is the dynamic range versus the dead-time of the front-end detector The goal is an 8-bit dynamic range for this pulse-width modulation (PWM) scheme, which is adequate for high resolution PET systems based on semiconductor detectors such as avalanche photodiodes (APD) or cadmium zinc telluride (CZT) A novel circuit has been designed, fabricated, and tested for the proposed PWM readout scheme This circuit is different than previously developed time over threshold pulse width modulation circuits used in high energy physics PWM techniques simplify the routing to the back end electronics without degrading the performance of the system A readout architecture based on PWM processes digital rather than analog pulses, which can be easily multiplexed, enabling one to achieve very high channel density required for ultra-high resolution, 3-D positioning PET detector systems

Sensitive silicon microphone with wide dynamic range

Abstract: A silicon microphone on which four acoustic transducers are integrated, having different values of sensitivity and, accordingly, different values of dynamic range; the analog acoustic signals are supplied from the four acoustic transducers to the integrated circuit device, and are converted to digital acoustic signals; the digital acoustic signal output from the acoustic transducers with relatively high sensitivity acoustic transducers are normalized with respect to the digital acoustic signal output from the acoustic transducer with lowest sensitivity, and the normalized digital acoustic signals are selectively formed into a composite acoustic signal depending upon the sound pressure of sound waves so that the dynamic range is expanded without sacrifice of high sensitivity in the low sound pressure range.

High dynamic range imager with a rolling shutter

Abstract: A high dynamic range imager operates pixels utilizing at least a short integration period and a long integration period. The pixel reading circuits of the imager are adapted to process pixel signals corresponding to the integration periods in parallel. The pixel signals are converted into digital values in parallel. The digital values are each linear functions of the incident light and therefore suitable for use with conventional color processing algorithms. A pipelined rolling shutter operation may be employed where the short integration period of one row of pixels is performed simultaneously with the long integration period of another row of pixels.

Multispectral high dynamic range imaging

Abstract: Capturing natural scenes with high dynamic range content using conventional RGB cameras generally results in saturated and underexposed and therefore compromising image areas. Furthermore the image lacks color accuracy due to a systematic color error of the RGB color filters. The problem of the limited dynamic range of the camera has been addressed by high dynamic range imaging1, 2 (HDRI): Several RGB images of different exposures are combined into one image with greater dynamic range. Color accuracy on the other hand can be greatly improved using multispectral cameras,3 which more accurately sample the electromagnetic spectrum. We present a promising combination of both technologies, a high dynamic range multispectral camera featuring a higher color accuracy, an improved signal to noise ratio and greater dynamic range compared to a similar low dynamic range camera.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.