Showing papers on "High dynamic range published in 2002"

Fast bilateral filtering for the display of high-dynamic-range images

Abstract: We present a new technique for the display of high-dynamic-range images, which reduces the contrast while preserving detail. It is based on a two-scale decomposition of the image into a base layer,...

Photographic tone reproduction for digital images

Abstract: A classic photographic task is the mapping of the potentially high dynamic range of real world luminances to the low dynamic range of the photographic print. This tone reproduction problem is also faced by computer graphics practitioners who map digital images to a low dynamic range print or screen. The work presented in this paper leverages the time-tested techniques of photographic practice to develop a new tone reproduction operator. In particular, we use and extend the techniques developed by Ansel Adams to deal with digital images. The resulting algorithm is simple and produces good results for a wide variety of images.

Gradient domain high dynamic range compression

Abstract: We present a new method for rendering high dynamic range images on conventional displays. Our method is conceptually simple, computationally efficient, robust, and easy to use. We manipulate the gradient field of the luminance image by attenuating the magnitudes of large gradients. A new, low dynamic range image is then obtained by solving a Poisson equation on the modified gradient field. Our results demonstrate that the method is capable of drastic dynamic range compression, while preserving fine details and avoiding common artifacts, such as halos, gradient reversals, or loss of local contrast. The method is also able to significantly enhance ordinary images by bringing out detail in dark regions.

Photographic tone reproduction for digital images

Abstract: A classic photographic task is the mapping of the potentially high dynamic range of real world luminances to the low dynamic range of the photographic print. This tone reproduction problem is also ...

Gradient domain high dynamic range compression

Abstract: We present a new method for rendering high dynamic range images on conventional displays. Our method is conceptually simple, computationally efficient, robust, and easy to use. We manipulate the gr...

Method and system to enhance dynamic range conversion useable with CMOS three-dimensional imaging

Abstract: High dynamic range brightness information is acquired by inputting detection current to a high (adjustable) gain resettable integrator whose output V(t) is compared to a Vth threshold by a comparator whose output is counted by a reset counter as V(t)≧Vth. When a desired count is attained, data acquisition ends, the counter is read, and the entire circuit is reset. A TOF data acquisition circuit includes first and second sequences of series-coupled delay units, and a like number of latch units coupled between respective delay units. A phase discriminator compares output from each chain and feedback a signal to one of the chains and to a comparator and can equalize delay through each chain. A control voltage is coupled to the remaining chain to affect through-propagation delay time. The latch units can capture the precise time when V(t)≧Vth. Successive measurement approximation can enhance TOF resolution.

Ultrasensitive and high-dynamic-range two-photon absorption in a GaAs photomultiplier tube.

Abstract: We demonstrate improved efficiency and dynamic range for two-photon absorption at 1.5 µm in a photoelectron-counting GaAs photomultiplier tube. cw laser measurements show pure two-photon absorption occurring in the device from average powers of 1.3 µW to nearly 1 mW. We use the detector to implement an autocorrelator with peak-power × average-power sensitivity of 1.7×10-4 mW2 and discuss practical ways to reduce this figure of merit to as low as 1×10-5 mW2.

Adaptive gain control for high dynamic range image display

Abstract: Realistic display of high dynamic range images without introducing any artifact is a hard problem. In this paper we address this problem using a detail preserving local gain control approach. Unlike many other local gain control methods available in the literature, our method is simple, and does not introduce ugly "halo" artifacts around the high dynamic range edges. We demonstrate the usefulness of this method by showing several examples.

High Dynamic Range Imaging of Natural Scenes.

Abstract: The ability to capture and render high dynamic range scenes limits the quality of current consumer and professional digital cameras. The absence of a well-calibrated high dynamic range color image database of natural scenes is an impediment to developing such rendering algorithms for digital photography. This paper describes our efforts to create such a database. First, we discuss how the image dynamic range is affected by three main components in the imaging pipeline: the optics, the sensor and the color transformation. Second, we describe a calibrated, portable high dynamic range imaging system. Third, we discuss the general properties of seventy calibrated high dynamic range images of natural scenes in the database (http://pdc.stanford.edu/hdri/). We recorded the calibrated RGB values and the spectral power distribution of illumination at different locations for each scene. The scene luminance ranges span two to six orders of magnitude. Within any scene, both the absolute level and the spectral composition of the illumination vary considerably. This suggests that future high dynamic range rendering algorithms need to account jointly for local color adaptation and local illumination level.

Perceptual Evaluation of Tone Mapping Operators with Regard to Similarity and Preference

Abstract: For years, 24-bit images effectively using 256 values for each color channel wereconsidered accurate enough to be used in the creation and display of photorealisticimagery. On the other end, photographers knowing the limitation of cameras andfilms would never attempt to photograph a scene including a light source placed inthe camera’s field of vision. However, as a result of global illumination renderingand high dynamic range (HDR) imaging [DM97], it is now common to generateimages spanning a huge range of luminance. Dealing with such images in elec-tronic form requires extending file formats that are restricted to too few luminancevalues and colors. An even more serious issue is effective displaying/printing ofthose images using media with limited dynamic range (both in reproducible lumi-nance values and color gamut).The first limitation was successfully addressed in different pixel encoding for-mats. A simple approach relies on using three floating point numbers for eachpixel RGB values, however, this leads to excessive file sizes. The HDR imagesize can be reduced to four bytes for each pixel using the RGBE format [War91],in which a common exponent and a mantissa are assumed for each channel thusallowing a wide dynamic range with little storage overhead. Another format, thelogLuv encoding for tiff images [Lar98] separates a logarithmic representation ofluminance and aCIE

Modeling, calibration, and correction of nonlinear illumination-dependent fixed pattern noise in logarithmic CMOS image sensors

Abstract: At present, most CMOS image sensors use an array of pixels with a linear response. However, pixels with a logarithmic response are also possible and are capable of imaging high dynamic range scenes without saturating. Unfortunately, logarithmic image sensors suffer from fixed pattern noise (FPN). Work reported in the literature generally assumes the FPN is independent of illumination. This paper develops a nonlinear model y=a+bln(c+x)+/spl epsi/ of a pixel for the digital response y to an illuminance x and shows that the FPN arises from a variation of the offset a, gain b, and bias c from pixel to pixel. Equations are derived to estimate these parameters by calibrating images of uniform stimuli, taken with varying illuminances. Experiments with a Fuga 15d image sensor, demonstrating parameter calibration and FPN correction, show that the nonlinear model outperforms previous models that assume either only offset or offset and gain variation.

A high performance digital receiver for home-built nuclear magnetic resonance spectrometers

Abstract: The design and construction of a high-performance, low-cost, and easy to assemble quadrature digital receiver for a home-built nuclear magnetic resonance (NMR) spectrometer is described. Critical synchronization and timing issues are considered and solutions are discussed. The performance of the receiver is compared to that of a modern commercial NMR spectrometer. Advantages of this system include excellent passband flatness and delay flatness, very sharp filter cutoff, high dynamic range, bandwidths up to 30 MHz, and perfect balance between the quadrature channels with no component matching or adjustment.

High dynamic range image editing

Abstract: A high dynamic range image editing system for editing an image file having pixels spanning a first range of light intensity levels in an image editing system that only displays differences in the light intensity levels of pixels within a second range of light intensity levels that is less than the first range of light intensity levels, without reducing the range of light intensity levels in the image file.

A 1 K/spl times/1 K high dynamic range CMOS image sensor with on-chip programmable region-of-interest readout

Abstract: An integrated 1024/spl times/1024 CMOS image sensor with programmable region-of-interest (ROI) readout and multiexposure technique has been developed and successfully tested. Size and position of the ROI is programmed based on multiples of a minimum readout kernel of 32/spl times/32 pixels. Since the dynamic range of the irradiance normally exceeds the electrical dynamic range of the imager that can be covered using a single integration time, a multiexposure technique has been implemented in the imager. Subsequent sensor images are acquired using different integration times and recomputed to form a single composite image. A newly developed algorithm performing the recomputation is presented. The chip has been realized in a 0.5-/spl mu/m n-well standard CMOS process. The pixel pitch is 10 /spl mu/m/sup 2/ and the total chip area is 164 mm/sup 2/.

Assorted Pixels: Multi-sampled Imaging with Structural Models

Abstract: Multi-sampled imaging is a general framework for using pixels on an image detector to simultaneously sample multiple dimensions of imaging (space, time, spectrum, brightness, polarization, etc) The mosaic of red, green and blue spectral filters found in most solid-state color cameras is one example of multi-sampled imaging We briefly describe how multi-sampling can be used to explore other dimensions of imaging Once such an image is captured, smooth reconstructions along the individual dimensions can be obtained using standard interpolation algorithms Typically, this results in a substantial reduction of resolution (and hence image quality) One can extract significantly greater resolution in each dimension by noting that the light fields associated with real scenes have enormous redundancies within them, causing different dimensions to be highly correlated Hence, multi-sampled images can be better interpolated using local structural models that are learned off-line from a diverse set of training images The specific type of structural models we use are based on polynomial functions of measured image intensities They are very effective as well as computationally efficient We demonstrate the benefits of structural interpolation using three specific applications These are (a) traditional color imaging with a mosaic of color filters, (b) high dynamic range monochrome imaging using a mosaic of exposure filters, and (c) high dynamic range color imaging using a mosaic of overlapping color and exposure filters

Scannerless range imaging system having high dynamic range

Abstract: A scannerless range imaging system includes an illumination system for illuminating a scene with modulated illumination of a predetermined modulation frequency, and an image intensifier receiving reflected modulated illumination and including a modulating stage for modulating the reflected modulated illumination from the scene with the predetermined modulation frequency. An image responsive element includes an array of individual pixels for capturing images output by the image intensifier, whereby the modulation of the reflected modulated illumination incorporates a phase delay corresponding to the distance of objects in the scene from the range imaging system. A transmittance filter, including a plurality of filter elements having a spatially varying pattern of transmittance, are arranged in a one-to-one mapping with respect to the pixels forming the image responsive element. The spatially varying pattern of transmittance provides a plurality of separate exposures which are subsequently combined to form an output image with an expanded dynamic range.

Dynamic holography for high-dynamic-range two-dimensional laser wavefront control

Abstract: 'Dynamic holography is demonstrated as a technique for high- dynamic-range, multi-function laser wavefront control. In this paper, we describe three variations for hologram generation and display. These include all-optical holography for severe aberration compensation, computer-processed holography for high-optical-efficiency severe aberration compensation and computer-generated holography for multi- function laser wavefront control including dynamic tip, tilt, focus and aberration control. A prototype hologram display system operates with total optical efficiencies up to 93% and with refresh rates on the order of 10 Hz. The prototype system has resolution sufficient to introduce about 200 waves of diffractive wavefront control at 532 nm optical wavelength.'© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

High Dynamic Range Active Pixel CMOS Image Sensor and data processing system incorporating adaptive pixel reset

Abstract: A high Dynamic Range Active Pixel CMOS image sensor architecture has incorporated therein an adaptive pixel reset. The individual sensor pixels are reset only when accumulated charge, or the integration time exceeds certain predetermined limits. The reset is skipped when the integrated charge signal in a given pixel is low. The accumulated number of reset skips in a given time frame, together with the standard analog output, is used to calculate the sensor high DR output signal. A signal processing system is used to simultaneously process both sensor analog and digital outputs.

High dynamic range CMOS image sensor with conditional reset

Abstract: In this paper, we propose a new image pixel structure for high dynamic range operation, which is based on a multiple sampling scheme and conditional reset circuits. To expand the dynamic range of the sensor, the output of the pixel is sampled multiple times in an integration time. In each sampling, the output of the pixel is compared with a reference voltage, and the result of this comparison activates the conditional reset circuit. The times of conditional reset during the integration contribute to the increase of the dynamic range of the sensor. Dynamic range can be increased to N, where N is the sampling times in an integration time. The test chip was fabricated with a 0.65-/spl mu/m CMOS technology (2-P, 2-M).

High dynamic range pixel with gain and true shutter capability

Abstract: A pixel architecture and associated three phase operating method for a CMOS active pixel sensor system is disclosed. The first phase is an accumulation phase, charges from the incident light as well as charges accumulated since after the prior cycle's accumulation phase are used to charge a node to control a source follower transistor. The second phase is a read-out phase, which shuts off the transfer transistor to isolate the photodiode from the source follower transistor while an the source follower transistor causes an electrical signal to be output from the pixel. The third phase is a reset phase which couples the node used to control the source follower transistor to a reset potential source. The architecture of the pixel of the present invention is capable of responding across a wide dynamic range of incident light while exhibiting minimal fixed pattern noise.

High-dynamic range SAXS data acquisition with an X-ray image intensifier

Abstract: Data with a wide dynamic range of intensity can be collected with a pinhole high-brilliance small-angle X-ray scattering (SAXS) camera using an image-intensified charge-coupled device (CCD) detector. The point spread function (PSF) of this detector has a narrow peak with a broad low tail such that a high level of scattered intensity at small angles can cause a significant background in the detector elements at higher angles. A correction scheme for the long tail of the PSF of the detector is needed when this integrating area detector is used for measuring intensity that spans a dynamic range of four to five orders of magnitude. A procedure is described for measuring the PSF contribution by masking a small part of the detector from the scattered radiation with an absorbing material. In order to measure the PSF, it is necessary to use a high-intensity spot, which is readily achieved by using a sample that scatters strongly at small angles. Although this intensity is spread over many pixels, the sharp features in the scattering from the silica sample chosen for this study permit one to obtain simultaneously both the narrow and the broad parts of the PSF. The data are compared with the actual scattering function, which has been measured exactly with a point-geometry Bonse–Hart camera. The advantages of this procedure are discussed.

Photodetector with high dynamic range and increased operating temperature

Abstract: A photodiode ( 1 ) in a conventional photodetector-pixel architecture is supplied with a shunt diode ( 2 ) connected to a control voltage (V 0 ). Suitable selection of the constant or time-varying control voltage (V c ) allows a combination of linear and non-linear, preferably logarithmic illumination response of the photodiode ( 1 ), resulting in a high dynamic photodetecting range of more than five orders of magnitude. The properties of the shunt diode ( 2 ) and the control voltage (V c ) can be chosen such that the resulting dark current matches the dark current of the photodiode ( 1 ), which becomes independent of voltage for high temperatures. This enables photodetecting with a sufficient dynamic range at higher temperatures than possible with conventional photodetectors.

ACTIVE-EYES: an adaptive pixel-by-pixel image-segmentation sensor architecture for high-dynamic-range hyperspectral imaging

Abstract: The ACTIVE-EYES (adaptive control for thermal imagers via electro-optic elements to yield an enhanced sensor) architecture, an adaptive image-segmentation and processing architecture, based on digital micromirror (DMD) array technology, is described. The concept provides efficient front-end processing of multispectral image data by adaptively segmenting and routing portions of the scene data concurrently to an imager and a spectrometer. The goal is to provide a large reduction in the amount of data required to be sensed in a multispectral imager by means of preprocessing the data to extract the most useful spatial and spectral information during detection. The DMD array provides the flexibility to perform a wide range of spatial and spectral analyses on the scene data. The spatial and spectral processing for different portions of the input scene can be tailored in real time to achieve a variety of preprocessing functions. Since the detected intensity of individual pixels may be controlled, the spatial image can be analyzed with gain varied on a pixel-by-pixel basis to enhance dynamic range. Coarse or fine spectral resolution can be achieved in the spectrometer by use of dynamically controllable or addressable dispersion elements. An experimental prototype, which demonstrated the segmentation between an imager and a grating spectrometer, was demonstrated and shown to achieve programmable pixelated intensity control. An information theoretic analysis of the dynamic-range control aspect was conducted to predict the performance enhancements that might be achieved with this architecture. The results indicate that, with a properly configured algorithm, the concept achieves the greatest relative information recovery from a detected image when the scene is made up of a relatively large area of moderate-dynamic-range pixels and a relatively smaller area of strong pixels that would tend to saturate a conventional sensor.

High dynamic range analog-to-digital converter having parallel equalizers

Abstract: An analog-to-digital converting includes a fanned out module for receiving an input signal and producing a plurality of new signals. A plurality of analog to digital converter modules receive the new signals from the fanned out module. Each of the new signals is assigned at least one of the analog to digital converters, such that the digital converter modules produce a plurality of digitized signals from each of their associated new signals. A combiner module receives the plurality of digitized signals, and combines the plurality of digitized signals to form a single digitized signal.

Charge multiplier with logarithmic dynamic range compression implemented in charge domain

Abstract: A CCD device incorporates Charge Multiplication in its CCD registers together with charge domain Dynamic Range compression. This structure preserves the high dynamic range available in the charge domain of these devices, and avoids limiting it by an inadequate voltage swing of the charge detection nodes and amplifiers. The Dynamic Range compression is logarithmic from a predetermined built in threshold and noiseless. The technique has an additional advantage of maintaining the compact size of the registers, and the registers may also include antiblooming devices to prevent blooming.

High dynamic range InP HBT delta-sigma analog-to-digital converters

Abstract: To date, the development of multifunction multicarrier digital receivers for cellular base station and military communications applications has been limited by the demanding dynamic range requirements for the analog-to-digital converter (ADC). The use of oversampling delta-sigma modulators provides a promising approach to overcoming the dynamic range barriers Nyquist-rate converters face in the same applications. This paper discusses issues involved in the design of high-speed high dynamic range wide-band delta-sigma ADCs for such communications applications. Test results of prototype designs are also presented. The delta-sigma modulators described in this paper operate at sampling frequencies ranging from 1 to 2.5 GHz with center frequencies ranging from dc to 100 MHz, providing between 74 and 84.2 dB signal-to-noise ratio (12 and 13.7 bits) for bandwidths of 25 and 12.5 MHz, respectively. The loop filters are continuous-time low-pass and bandpass implementations of order 6 and 10, and were fabricated in an InP heterojunction bipolar (HBT) technology. A typical tenth-order design consumes 6 W of power and occupies a die area of 23.5 mm/sup 2/.

Low-threshold high-dynamic-range optical limiter for ultra-short laser pulses

Abstract: We demonstrate an optical limiter for ultra-short (∼100-fs) laser pulses. The device has a dynamic range (= damage energy/onset-of-limiting energy) of more than 10000 and an onset-of-limiting energy of only ∼10 nJ. The output-pulse energy is kept below 1.3 μJ. The limiting mechanism is based on two-photon absorption and refractive nonlinearities in a 20-mm piece of ZnSe. We discuss the importance of the different nonlinearities, damage issues, and guidelines for the construction of the device.

Perceptual tone mapping operators for high dynamic range scenes

Abstract: A major goal of realistic image synthesis is to generate images that are both physically and perceptually indistinguishable from reality. One of the practical obstacles in reaching this goal is that the natural world exhibits a wide range of colors and intensities. The range of the luminances in the real world can vary from 10-4cd/m2 (for starlight) to 105cd/m2 (for a daylight scene). Reproducing these luminances on a cathode-ray tube (CRT) display is currently not possible as the achievable intensities are about 100 cd/m2 and the practical ratio between maximum and minimum pixel intensity is approximately 100:1. At the University of Bristol, we have constructed a High Dynamic Range (HDR) viewer that is capable of achieving a 10,000:1 contrast ratio. This sketch investigates, by means of psychophysical experiments, the benefits such a HDR device has to offer realistic computer graphics.

W-CDMA SiGe TX-IC with high dynamic range and high power control accuracy

Abstract: This paper demonstrates the SiGe TX-IC for W-CDMA mobile terminals. For the TX-IC, a novel architecture of a variable gain amplifier is proposed to improve dynamic range and power control accuracy. With the 0.5 /spl mu/m SiGe BiCMOS technology, this TX-IC achieved over 100 dB dynamic ranges within /spl plusmn/1.5dB accuracy over all temperatures. Output power of 7 dBm can be achieved by employment of P-MOSFET current mirror type self bias control circuit for the driver amplifier. Measurement results also satisfy the specification defined by 3GPP.