Showing papers on "High dynamic range published in 2006"

High dynamic range image rendering with a retinex-based adaptive filter

Abstract: We propose a new method to render high dynamic range images that models global and local adaptation of the human visual system. Our method is based on the center-surround Retinex model. The novelties of our method is first to use an adaptive filter, whose shape follows the image high-contrast edges, thus reducing halo artifacts common to other methods. Second, only the luminance channel is processed, which is defined by the first component of a principal component analysis. Principal component analysis provides orthogonality between channels and thus reduces the chromatic changes caused by the modification of luminance. We show that our method efficiently renders high dynamic range images and we compare our results with the current state of the art

Ghost Removal in High Dynamic Range Images

Abstract: High dynamic range images may be created by capturing multiple images of a scene with varying exposures. Images created in this manner are prone to ghosting artifacts, which appear if there is movement in the scene at the time of capture. This paper describes a novel approach to removing ghosting artifacts from high dynamic range images, without the need for explicit object detection and motion estimation. Weights are computed iteratively and then applied to pixels to determine their contribution to the final image. We use a non-parametric model for the static part of the scene, and a pixel's membership in this model determines its weight. In contrast to previous approaches, our technique does not rely on explicit object detection, tracking, or pixelwise motion estimates. Ghost-free images of different scenes demonstrate the effectiveness of our technique.

Evaluation of high dynamic range photography as a luminance data acquisition system

Abstract: In this paper, the potential, limitations and applicability of the High Dynamic Range (HDR) photography technique are evaluated as a luminance mapping tool. Multiple exposure photographs of static scenes were taken with a commercially available digital camera to capture the wide luminance variation within the scenes. The camera response function was computationally derived by using Photosphere software, and was used to fuse the multiple photographs into an HDR image. The vignetting effects and point spread function of the camera and lens system were determined. Laboratory and field studies showed that the pixel values in the HDR photographs correspond to the physical quantity of luminance with reasonable precision and repeatability.

Inverse tone mapping

Abstract: In recent years many Tone Mapping Operators (TMOs) have been presented in order to display High Dynamic Range Images (HDRI) on typical display devices. TMOs compress the luminance range while trying to maintain contrast. The dual of tone mapping, inverse tone mapping, expands a Low Dynamic Range Image (LDRI) into a HDRI. HDRIs contain a broader range of physical values that can be perceived by the human visual system. The majority of today's media is stored in low dynamic range. Inverse Tone Mapping Operators (iTMOs) could thus potentially revive all of this content for use in high dynamic range display and image-based lighting. We propose an approximate solution to this problem that uses median-cut to find the areas considered of high luminance and subsequently apply a density estimation to generate an Expand-map in order to extend the range in the high luminance areas using an inverse Photographic Tone Reproduction operator.

The Reproduction of Specular Highlights on High Dynamic Range Displays

Abstract: Recent advances in the design of high dynamic range (HDR) monitors enable the display of images having a large dynamic range, close to that encountered in the real world. As their usage will increase, we will be confronted with the problem of rerendering images that have been mapped to standard dynamic range (SDR) displays so that they look natural on HDR monitors. We address this issue for SDR images representing original HDR scenes. We propose a tone scale function that takes advantage of the increase in dynamic range of HDR monitors to recreate the brightness of specular highlights, which were clipped or compressed by the capturing and rendering process to SDR. We validate the use of such functions with a psychovisual experiment conducted on an HDR display, where the observers’ task was to judge pairs of tone-scaled images. The result of the experiment shows that using part of the extension of dynamic range provided by HDR displays to enhance the brightness of specular highlights leads to more natural looking images.

Backward Compatible High Dynamic Range MPEG Video Compression

Abstract: To embrace the imminent transition from traditional low-contrast video (LDR) content to superior high dynamic range (HDR) content, we propose a novel backward compatible HDR video compression (HDR MPEG) method. We introduce a compact reconstruction function that is used to decompose an HDR video stream into a residual stream and a standard LDR stream, which can be played on existing MPEG decoders, such as DVD players. The reconstruction function is finely tuned to the content of each HDR frame to achieve strong decorrelation between the LDR and residual streams, which minimizes the amount of redundant information. The size of the residual stream is further reduced by removing invisible details prior to compression using our HDR-enabled filter, which models luminance adaptation, contrast sensitivity, and visual masking based on the HDR content. Designed especially for DVD movie distribution, our HDR MPEG compression method features low storage requirements for HDR content resulting in a 30% size increase to an LDR video sequence. The proposed compression method does not impose restrictions or modify the appearance of the LDR or HDR video. This is important for backward compatibility of the LDR stream with current DVD appearance, and also enables independent fine tuning, tone mapping, and color grading of both streams.

Methods and systems for high dynamic range video coding

Abstract: Embodiments of the present invention comprise methods and systems for high dynamic range (HDR) video coding and decoding that is backwards-compatible with one or more standard dynamic range (SDR) encoding and decoding techniques, through the transmission of HDR residual data used to reconstruct an encoded HDR sequence from an inverse-tone-mapped SDR sequence.

High dynamic range codecs

Abstract: A method for encoding high dynamic range (HDR) images involves providing a lower dynamic range (LDR) image, generating a prediction function for estimating the values for pixels in the HDR image based on the values of corresponding pixels in the LDR image, and obtaining a residual frame based on differences between the pixel values of the HDR image and estimated pixel values The LDR image, prediction function and residual frame can all be encoded in data from which either the LDR image of HDR image can be recreated

A High Dynamic Range CMOS Image Sensor With Inpixel Light-to-Frequency Conversion

Abstract: A high dynamic range CMOS image sensor with inpixel light-to-frequency conversion has been designed. The prototype chip was fabricated in a standard 0.18-mum single-poly six-metal CMOS technology. The experimental results show that, operating at 1.2 V, the sensor can achieve a linear dynamic range of over 115 dB and an overall dynamic range of over 130 dB

Estimation of Vehicle Speed Based on Asynchronous Data from a Silicon Retina Optical Sensor

Abstract: This work presents an embedded optical sensory system for traffic monitoring and vehicles speed estimation based on a neuromorphic "silicon-retina" image sensor, and the algorithm developed for processing the asynchronous output data delivered by this sensor. The main purpose of these efforts is to provide a flexible, compact, low-power and low-cost traffic monitoring system which is capable of determining the velocity of passing vehicles simultaneously on multiple lanes. The system and algorithm proposed exploit the unique characteristics of the image sensor with focal-plane analog preprocessing. These features include sparse asynchronous data output with high temporal resolution and low latency, high dynamic range and low power consumption. The system is able to measure velocities of vehicles in the range 20 to 300 km/h on up to four lanes simultaneously, day and night and under variable atmospheric conditions, with a resolution of 1 km/h. Results of vehicle speed measurements taken from a test installation of the system on a four-lane highway are presented and discussed. The accuracy of the speed estimate has been evaluated on the basis of calibrated light-barrier speed measurements. The speed estimation error has a standard deviation of 2.3 km/h and near zero mean

High dynamic range texture compression for graphics hardware

Abstract: In this paper, we break new ground by presenting algorithms for fixed-rate compression of high dynamic range textures at low bit rates. First, the S3TC low dynamic range texture compression scheme is extended in order to enable compression of HDR data. Second, we introduce a novel robust algorithm that offers superior image quality. Our algorithm can be efficiently implemented in hardware, and supports textures with a dynamic range of over 109:1. At a fixed rate of 8 bits per pixel, we obtain results virtually indistinguishable from uncompressed HDR textures at 48 bits per pixel. Our research can have a big impact on graphics hardware and real-time rendering, since HDR texturing suddenly becomes affordable.

Encoding of high dynamic range video with a model of human cones

Abstract: A recently developed quantitative model describing the dynamical response characteristics of primate cones is used for rendering high dynamic range (HDR) video. The model provides range compression, as well as luminance-dependent noise suppression. The steady-state (static) version of the model provides a global tone mapping algorithm for rendering HDR images. Both the static and dynamic cone models can be inverted, enabling expansion of the HDR images and video that were compressed with the cone model.

Lossy compression of high dynamic range images and video

Abstract: Most common image and video formats have been designed to work with existing output devices, like LCD or CRT monitors. As the display technology makes huge progress, these formats can no longer represent the data that the new devices can display. Therefore a shift towards higher precision image and video formats seems to be imminent. To overcome limitations of the common image and video formats, such as JPEG, PNG or MPEG, we propose a novel color space, which can accommodate an extended dynamic range and guarantees the precision that is below the visibility threshold. The proposed color space, which is derived from the contrast detection data, can represent the full range of luminance values and the complete color gamut that is visible to the human eye. We show that only minor changes are required to the existing encoding algorithms to accommodate a new color space and therefore greatly enhance information content of the visual data. We demonstrate this on two compression algorithms for High Dynamic Range (HDR) visual data: for static images and for video. We argue that the proposed HDR representation is a simple and universal way to encode visual data independently of the display or capture technology.

High dynamic range imaging by pupil single‐mode filtering and remapping

Abstract: Because of atmospheric turbulence, obtaining high angular resolution images with a high dynamic range is difficult even in the near-infrared domain of wavelengths. We propose a novel technique to overcome this issue. The fundamental idea is to apply techniques developed for long baseline interferometry to the case of a single-aperture telescope. The pupil of the telescope is broken down into coherent subapertures each feeding a single-mode fibre. A remapping of the exit pupil allows interfering all subapertures non-redundantly. A diffraction-limited image with very high dynamic range is reconstructed from the fringe pattern analysis with aperture synthesis techniques, free of speckle noise. The performances of the technique are demonstrated with simulations in the visible range with an 8-m telescope. Raw dynamic ranges of 1:10 6 can be obtained in only a few tens of seconds of integration time for bright objects.

High dynamic range data format conversions for digital media

Abstract: One or more continuous mappings are defined at a digital media encoder to convert input digital media data in a first high dynamic range format to a second format with a smaller dynamic range than the first format. The encoder converts the input digital media data to the second format with the smaller dynamic range using the continuous mapping and one or more conversion parameters relating to the continuous mapping. The encoder encodes the converted digital media data in a bitstream along with the conversion parameter(s). The conversion parameter(s) enable a digital media decoder to convert the converted digital media data back to the first high dynamic range format from the second format with the smaller dynamic range. Techniques for converting different input formats with different dynamic ranges are described.

Method, apparatus and system providing a storage gate pixel with high dynamic range

Abstract: A method, apparatus and system are described providing a high dynamic range pixel. An integration period has multiple sub-integration periods during which charges are accumulated in a photosensor and repeatedly transferred to a storage node, where the charges are accumulated for later transfer to another storage node for output.

CMOS image sensors for sensor networks

Abstract: We report on two generations of CMOS image sensors with digital output fabricated in a 0.6 ?m CMOS process. The imagers embed an ALOHA MAC interface for unfettered self-timed pixel read-out targeted to energy-aware sensor network applications. Collision on the output is monitored using contention detector circuits. The image sensors present very high dynamic range and ultra-low power operation. This characteristics allow the sensor to operate in different lighting conditions and for years on the sensor network node power budget.

Representing and reconstructing high dynamic range images

Abstract: A high dynamic range image can be recovered from a full-resolution lower-dynamic-range image and a reduced-resolution higher-dynamic-range image. Information regarding higher spatial frequencies may be obtained by extracting high spatial frequencies from the lower-dynamic-range image. In some embodiments an approximate impulse-response function is determined by comparing the higher- and lower-dynamic range images. A scaling image obtained by applying the impulse-response function to a high-frequency band of the lower-dynamic range image is combined with an upsampled higher-dynamic range image to yield a reconstructed image.

Multi-View Multi-Exposure Stereo

Abstract: Multi-view stereo algorithms typically rely on same-exposure images as inputs due to the brightness constancy assumption. While state-of-the-art depth results are excellent, they do not produce high-dynamic range textures required for high-quality view reconstruction. In this paper, we propose a technique that adapts multi-view stereo for different exposure inputs to simultaneously recover reliable dense depth and high dynamic range textures. In our technique, we use an exposure-invariant similarity statistic to establish correspondences, through which we robustly extract the camera radiometric response function and the image exposures. This enables us to then convert all images to radiance space and selectively use the radiance data for dense depth and high dynamic range texture recovery. We show results for synthetic and real scenes.

Efficient wavelet rotation for environment map rendering

Abstract: Real-time shading with environment maps requires the ability to rotate the global lighting to each surface point's local coordinate frame. Although extensive previous work has studied rotation of functions represented by spherical harmonics, little work has investigated efficient rotation of wavelets. Wavelets are superior at approximating high frequency signals such as detailed high dynamic range lighting and very shiny BRDFs, but present difficulties for interactive rendering due to the lack of an analytic solution for rotation. In this paper we present an efficient computational solution for wavelet rotation using precomputed matrices. Each matrix represents the linear transformation of source wavelet bases defined in the global coordinate frame to target wavelet bases defined in sampled local frames. Since wavelets have compact support, these matrices are very sparse, enabling efficient storage and fast computation at run-time. In this paper, we focus on the application of our technique to interactive environment map rendering. We show that using these matrices allows us to evaluate the integral of dynamic lighting with dynamic BRDFs at interactive rates, incorporating efficient non-linear approximation of both illumination and reflection. Our technique improves on previous work by eliminating the need for prefiltering environment maps, and is thus significantly faster for accurate rendering of dynamic environment lighting with high frequency reflection effects.

A Low-Voltage and Low-Power Adaptive Switched-Current Sigma–Delta ADC for Bio-Acquisition Microsystems

Abstract: An ultralow-voltage and low-power adaptive sigma-delta analog-to-digital converter (SDADC) with a 10-bit dynamic range for bio-microsystem applications is presented. The proposed SDADC includes a switched-current sigma-delta modulator (SISDM) and a digital decimator. In order to achieve the low-voltage requirement, a novel class-AB switched-current memory cell is adopted to implement the SISDM with the oversampling ratio (OSR) of 64. In addition, a proposed differential current comparator and a low-voltage 1-bit switched-current digit-to-analog converter (SIDAC) are used for the design of the SDM. Benefits from the SISDM using the class-AB memory cell are low power consumption and high dynamic range. Moreover, a new single-multiplier structure is presented to implement the finite-impulse-response (FIR) digital filters which are the major hardware elements in the decimator. For the various applications with different biosignal frequencies, the SDADC could be manipulated in different operating modes. The overall ADC has been implemented in a TSMC 0.18-mum 1P6M standard CMOS process technology. Without a voltage booster to raise the gate voltage of switches, measurement results show that the SISDM has a dynamic range over 60 dB and a power consumption of 180 muW with an input signal of 1.25-kHz sinusoid wave and 5-kHz bandwidth under a single 0.8-V power supply for electroneurography signals. In addition, the postlayout simulations of SDADC including SISDM and decimator reveal that the dynamic range is still over 60 dB without degrading by digital circuits

High dynamic range texture compression

Abstract: We present a novel compression scheme for high dynamic range textures, targeted for hardware implementation. Our method encodes images at a constant 8 bits per pixel, for a compression ratio of 6:1. We demonstrate that our method achieves good visual fidelity, surpassing DXTC texture compression of RGBE data which is the most practical method on existing graphics hardware. The decoding logic for our method is simple enough to be implemented as part of the texture fetch unit in graphics hardware.

High-dynamic-range laser range finders based on a novel multimodulated frequency method

Abstract: A continuous-wave phase-shift laser range finder employs a novel multimodulation frequency method associating an undersampling analog-digital converter (ADC) with digital synchronous detection. This presentation greatly improves measured phase accuracy and reduces prior art scheme complexities. The novel patented design includes one phase-lock-loop (PLL) chip to produce a multimodulation frequency, one analog-to-digital converter operating at a low sampling rate, and an effective algorithm to calculate the final distance, which has encoded computing codes, and is implemented into compact computing circuits but without mixers and redundant components. The experimental results prove that a nonambiguity range is easily achieved to 1.5 Km when the modulation frequency is operated at 0.1 MHz. The measured accuracy approaches 2.9 mm using the same apparatus when the modulation frequency is tuned to 14.5 MHz. Dynamic range can reach 5.2×105 without a very high modulation frequency below 15 MHz, as revealed by a detailed analysis.

Class-AB techniques for high-dynamic-range microwave-photonic links

Abstract: Class-AB techniques are analyzed as a means to minimize the noise associated with the residual carrier in analog optical links. A bound for shot and intensity noise is derived and compared to previously reported measurements. It is found that for an ideal modulator transfer function (Class B), a substantial improvement in shot-noise limited spur-free dynamic range (e.g., 11.7 dB at 10% modulation) can be realized.

HDR VolVis: high dynamic range volume visualization

Abstract: In this paper, we present an interactive high dynamic range volume visualization framework (HDR VolVis) for visualizing volumetric data with both high spatial and intensity resolutions. Volumes with high dynamic range values require high precision computing during the rendering process to preserve data precision. Furthermore, it is desirable to render high resolution volumes with low opacity values to reveal detailed internal structures, which also requires high precision compositing. High precision rendering will result in a high precision intermediate image (also known as high dynamic range image). Simply rounding up pixel values to regular display scales will result in loss of computed details. Our method performs high precision compositing followed by dynamic tone mapping to preserve details on regular display devices. Rendering high precision volume data requires corresponding resolution in the transfer function. To assist the users in designing a high resolution transfer function on a limited resolution display device, we propose a novel transfer function specification interface with nonlinear magnification of the density range and logarithmic scaling of the color/opacity range. By leveraging modern commodity graphics hardware, multiresolution rendering techniques and out-of-core acceleration, our system can effectively produce an interactive visualization of large volume data, such as 2.048/sup 3/.

The analog challenge of nanometer CMOS

Abstract: Nanometer CMOS technology offers the required integration density for advanced products such as home theatre equipment and personal communication devices. The system solutions inside these products demand highly integrated systems-on-silicon, blending high-density digital functions with analog interface circuits. These integrated solutions have to cope with high data-rates, and thus require high speed and high dynamic range circuits, without compromising power consumption. Novel choices on circuit and system level are required to handle the increased number of devices subject to high variability, running at higher intrinsic speeds with a constraint power supply.

Architectures for High Dynamic Range, High Speed Image Sensor Readout Circuits

Abstract: The stringent performance requirements of many infrared imaging applications warrant the development of precision high dynamic range, high speed focal plane arrays. In addition to achieving high dynamic range, the readout circuits for these image sensors must achieve high linearity and SNR at low power consumption. Two high dynamic range image sensor schemes that have been developed for visible range imaging were reviewed first and discuss why they cannot meet the stringent performance demands of infrared imaging. A new dynamic range extension scheme, folded multiple capture, was then described that can meet these performance requirements. Dynamic range is extended using synchronous self-reset while high SNR is maintained using few non-uniformly spaced captures and least-squares fit to estimate pixel photocurrent. The paper concludes with a description of a prototype of this architecture targeted for 3D-IC IR focal plane arrays

Mixed analog and digital pixel for high dynamic range readout

Abstract: An improved CMOS pixel with a combination of analog and digital readouts to provide a large pixel dynamic range without compromising low-light performance using a comparator to test the value of an accumulated charge at a series of exponentially increasing exposure times. The test is used to stop the integration of photocurrent once the accumulated analog voltage has reached a predetermined threshold. A one-bit output value of the test is read out of the pixel (digitally) at each of the exponentially increasing exposure periods. At the end of the integration period, the analog value stored on the integration capacitor is read out using conventional CMOS active pixel readout circuits.

Tone mapping for high dynamic range images

Abstract: Tone mapping is an essential step for the reproduction of "nice looking" images. It provides the mapping between the luminances of the original scene to the output device's display values. When the dynamic range of the captured scene is smaller or larger than that of the display device, tone mapping expands or compresses the luminance ratios. We address the problem of tone mapping high dynamic range (HDR) images to standard displays (CRT, LCD) and to HDR displays. With standard displays, the dynamic range of the captured HDR scene must be compressed significantly, which can induce a loss of contrast resulting in a loss of detail visibility. Local tone mapping operators can be used in addition to the global compression to increase the local contrast and thus improve detail visibility, but this tends to create artifacts. We developed a local tone mapping method that solves the problems generally encountered by local tone mapping algorithms. Namely, it does not create halo artifacts, nor graying-out of low contrast areas, and provides good color rendition. We then investigated specifically the rendition of color and confirmed that local tone mapping algorithms must be applied to the luminance channel only. We showed that the correlation between luminance and chrominance plays a role in the appearance of the final image but a perfect decorrelation is not necessary. Recently developed HDR monitors enable the display of HDR images with hardly any compression of their dynamic range. The arrival of these displays on the market create the need for new tone mapping algorithms. In particular, legacy images that were mapped to SDR displays must be re-rendered to HDR displays, taking best advantage of the increase in dynamic range. This operation can be seen as the reverse of the tone mapping to SDR. We propose a piecewise linear tone scale function that enhances the brightness of specular highlights so that the sensation of naturalness is improved. Our tone scale algorithm is based on the segmentation of the image into its diffuse and specular components as well as on the range of display luminance that is allocated to the specular component and the diffuse component, respectively. We performed a psychovisual experiment to validate the benefit of our tone scale. The results showed that, with HDR displays, allocating more luminance range to the specular component than what was allocated in the image rendered to SDR displays provides more natural looking images.