Showing papers on "Subpixel rendering published in 2006"

Improving accuracy by subpixel smoothing in the finite-difference time domain.

Abstract: Finite-difference time-domain (FDTD) methods suffer from reduced accuracy when modeling discontinuous dielectric materials, due to the inhererent discretization (pixelization). We show that accuracy can be significantly improved by using a subpixel smoothing of the dielectric function, but only if the smoothing scheme is properly designed. We develop such a scheme based on a simple criterion taken from perturbation theory and compare it with other published FDTD smoothing methods. In addition to consistently achieving the smallest errors, our scheme is the only one that attains quadratic convergence with resolution for arbitrarily sloped interfaces. Finally, we discuss additional difficulties that arise for sharp dielectric corners.

Geometrical SAR image registration

Abstract: Accurate subpixel registration of synthetic aperture radar (SAR) images is an issue that is again growing interest since its initial developments related to two-pass interferometry. Recent progress in coherent (multichannel) SAR processing raises the need for accurate registration of data takes acquired with large baseline spans, high temporal coverage, and with different frequency and/or operational modes. In this paper, we discuss a SAR image-registration procedure, based on the use of external measures which allows obtaining a very accurate alignment of SAR images. The presented technique makes use of a digital elevation model and of the precise information about the acquisition flight tracks, to compute the warping functions that map the position of each pixel in the different takes, thus avoiding any approximation. The resulting algorithm is simple, robust, precise, and very efficient; as a matter of fact, it may achieve high accuracy even in critical areas, such as steep topography regions. Moreover, the availability of an analytical and exact model allows performing a detailed sensitivity analysis that can be useful in evaluating the applicability of this technique even to future high-precision satellite systems. Extensive testing, carried out on several real European Remote Sensing and ENVISAT datasets, clearly shows the effectiveness of such algorithm in registering critical SAR images

Four color arrangements of emitters for subpixel rendering

Abstract: Novel three-color and four-color subpixel arrangements and architectures for display and the like are herein disclosed Novel techniques for subpixel rendering on the above subpixel arrangements are also herein disclosed

Superresolution mapping using a hopfield neural network with fused images

Abstract: Superresolution mapping is a set of techniques to increase the spatial resolution of a land cover map obtained by soft-classification methods. In addition to the information from the land cover proportion images, supplementary information at the subpixel level can be used to produce more detailed and accurate land cover maps. The proposed method in this research aims to use fused imagery as an additional source of information for superresolution mapping using the Hopfield neural network (HNN). Forward and inverse models were incorporated in the HNN to support a new reflectance constraint added to the energy function. The value of the function was calculated based on a linear mixture model. In addition, a new model was used to calculate the local endmember spectra for the reflectance constraint. A set of simulated images was used to test the new technique. The results suggest that fine spatial resolution fused imagery can be used as supplementary data for superresolution mapping from a coarser spatial resolution land cover proportion imagery.

Subpixel estimation of shifts directly in the Fourier domain

Abstract: In this paper, we establish the exact relationship between the continuous and the discrete phase difference of two shifted images, and show that their discrete phase difference is a two-dimensional sawtooth signal. Subpixel registration can, thus, be performed directly in the Fourier domain by counting the number of cycles of the phase difference matrix along each frequency axis. The subpixel portion is given by the noninteger fraction of the last cycle along each axis. The problem is formulated as an overdetermined homogeneous quadratic cost function under rank constraint for the phase difference, and the shape constraint for the filter that computes the group delay. The optimal tradeoff for imposing the constraints is determined using the method of generalized cross validation. Also, in order to robustify the solution, we assume a mixture model of inlying and outlying estimated shifts and truncate our quadratic cost function using expectation maximization.

Multiprimary color subpixel rendering with metameric filtering

Abstract: Systems and methods of rendering image data to multiprimary displays that adjust image data across metamers are herein disclosed. The metamer filtering may be based upon input image content and may optimize subpixel values to improve image rendering accuracy or perception. The optimizations may be made according to many possible desired effects. One embodiment comprises a display system comprising: a display, said display comprising at least a first set of subpixels and a second set of subpixels further comprising at least one metamer; an input image data unit; a spatial frequency detection unit, said spatial frequency detection unit extracting a spatial frequency characteristic from said input image data; and an adjustment unit, said adjustment unit adjusting image data of said first set and said second set of subpixels according to said spatial frequency characteristic.

A real-time large disparity range stereo-system using FPGAs

Abstract: In this paper, we discuss the design and implementation of a Field-Programmable Gate Array (FPGA) based stereo depth measurement system that is capable of handling a very large disparity range. The system performs rectification of the input video stream and a left-right consistency check to improve the accuracy of the results and generates subpixel disparities at 30 frames/second on 480 × 640 images. The system is based on the Local Weighted Phase-Correlation algorithm [9] which estimates disparity using a multi-scale and multi-orientation approach. Though FPGAs are ideal devices to exploit the inherent parallelism in many computer vision algorithms, they have a finite resource capacity which poses a challenge when adapting a system to deal with large image sizes or disparity ranges. In this work, we take advantage of the temporal information available in a video sequence to design a novel architecture for the correlation unit to achieve correlation over a large range while keeping the resource utilisation very low as compared to a naive approach of designing a correlation unit in hardware.

Mapping impervious surface area using high resolution imagery: a comparison of object-based and per pixel classification

Abstract: Impervious surface area is a key indicator of environmental quality. Satellite remote sensing of impervious surface has focused on subpixel analysis via various forms of statistical estimation, subpixel classification, and spectral mixture analysis, using medium resolution Landsat TM or ETM+ data. Maps of impervious surface area from these studies provide useful inputs to planning and management activities at city to regional scales. However, for local studies, large-scale, higher resolution maps are preferred. This study investigates digital classification techniques of mapping of impervious surface area using high resolution Quickbird satellite data. Two methods – object-based and per pixel classification – are explored and compared. The results provide information for accurate impervious surface mapping and estimation in high resolution imagery.

A Subpixel Image Matching Technique Using Phase-Only Correlation

Abstract: This paper presents a high-accuracy image matching technique using a Phase-Only Correlation (POC) function The POC-based image matching enables estimation of image displacements with 1/10~1/100-pixel accuracy by a function fitting technique using the closed-form representation of the POC function's peak This method requires an iterative process for the nonlinear function fitting, resulting in long computation times In this paper, we propose a Peak Evaluation Formula (PEF) that directly estimates the correlation peak location from actual 2-D data array of the POC function Experimental evaluation shows that the proposed method reduces computation time without sacrificing image matching accuracy

Pre-Subpixel Rendered Image Processing In Display Systems

Abstract: Display systems and image processing methods process pre-subpixel rendered images embedded in input color image data. The display systems include a pre-subpixel rendered (P-SPR) image detector that detects locations of a marking code that marks the portion of the input data that has been pre-subpixel rendered and which is ready for direct display. Several display system embodiments comprise first and second image data paths; the input data that requires subpixel rendering proceeds along the first path while the P-SPR image data proceeds along the second path. Another display system embodiment processes the combined input and P-SPR data along a single data path. Techniques for marking and detecting P-SPR image data using two distinct marking codes are presented in the context of the subpixel layout of the display. Techniques for using P-SPR data to display high-quality graphical symbols (e.g., font glyphs) are suitable for small, low-cost display devices.

Superresolution image reconstruction from a sequence of aliased imagery.

Abstract: We present a superresolution image reconstruction from a sequence of aliased imagery. The subpixel shifts (displacement) among the images are unknown due to the uncontrolled natural jitter of the imager. A correlation method is utilized to estimate subpixel shifts between each low-resolution aliased image with respect to a reference image. An error-energy reduction algorithm is derived to reconstruct the high-resolution alias-free output image. The main feature of this proposed error-energy reduction algorithm is that we treat the spatial samples from low-resolution images that possess unknown and irregular (uncontrolled) subpixel shifts as a set of constraints to populate an oversampled (sampled above the desired output bandwidth) processing array. The estimated subpixel locations of these samples and their values constitute a spatial domain constraint. Furthermore, the bandwidth of the alias-free image (or the sensor imposed bandwidth) is the criterion used as a spatial frequency domain constraint on the oversampled processing array. The results of testing the proposed algorithm on the simulated low- resolution forward-looking infrared (FLIR) images, real-world FLIR images, and visible images are provided. A comparison of the proposed algorithm with a standard interpolation algorithm for processing the simulated low-resolution FLIR images is also provided.

Interpolation Free Subpixel Accuracy Motion Estimation

Abstract: Subpixel motion estimation plays an important role in compression efficiency within modern video codecs such as MPEG2, MPEG4, and H.264. Subpixel motion estimation is implemented within these standards using interpolated values at 1/2 or 1/4 pixel accuracy. Such interpolation gives a good reduction in residual energy for each predicted macroblock and, therefore, improves compression. However, this leads to a significant increase in computational complexity at the encoder. This is especially true for H.264 where the cost of an exhaustive set of macroblock segmentations need to be estimated in order to obtain an optimal mode for prediction. This paper presents a novel interpolation-free scheme for subpixel motion estimation using the result of the full pixel sum of absolute difference distribution of each motion compensated block applied to an H.264 encoder. This system produces reduced complexity motion estimation with a controllable tradeoff between compression performance and encoder speed. These methods facilitate the generation of a real time software H.264 encoder

OLED device with improved power consumption

Abstract: A method for making an OLED device, comprising: providing a plurality of subpixels of different colors, including at least three gamut-defining subpixels, each subpixel requiring an operating voltage which is based on the maximum current density required by that subpixel; selecting the display operating voltage to be equal to or greater than the maximum required subpixel operating voltage; and selecting the area of the subpixels to reduce the maximum required subpixel operating voltage, thereby reducing the display operating voltage so as to reduce power consumption in the device.

Color flat panel display sub-pixel rendering and driver configuration for sub-pixel arrangements with split sub-pixels

Abstract: Various embodiments of a sub-pixel repeating group are disclosed. In one embodiment, an octal subpixel repeating group may comprise three-color (red, green and blue) sub-pixels with blue colored subpixel comprising twice the number of positions within the octal sub-pixel grouping as the red and green colored sub-pixels. In another embodiment, a subpixel repeating group comprises two rows of eight “split” subpixels comprising three primary colors and a non-saturated neutral, or white, subpixel functioning as a primary color.

A Real-Time Large Disparity Range Stereo-System using FPGAs

Abstract: In this paper, we discuss the design and implementation of a Field-Programmable Gate Array (FPGA) based stereo depth measurement system that is capable of handling a very large disparity range. The system performs rectification of the input video stream and a left-right consistency check to improve the accuracy of the results and generates subpixel disparities at 30 frames/second on 480 × 640 images. The system is based on the Local Weighted Phase- Correlation algorithm [9] which estimates disparity using a multi-scale and multi-orientation approach. Though FPGAs are ideal devices to exploit the inherent parallelism in many computer vision algorithms, they have a finite resource capacity which poses a challenge when adapting a system to deal with large image sizes or disparity ranges. In this work, we take advantage of the temporal information available in a video sequence to design a novel architecture for the correlation unit to achieve correlation over a large range while keeping the resource utilisation very low as compared to a naive approach of designing a correlation unit in hardware.

Temporal target tracking in hyperspectral images

Abstract: This research addresses the problem of tracking a moving point target in a time sequence of hyperspectral images; we focus on the detection of moving targets with staring technologies In these applications, the images consist of targets moving at subpixel velocity in backgrounds that are influenced by both evolving clutter and noise The demand for a low false-alarm rate on one hand and a high probability of detection on the other makes the tracking a challenging task The use of hyperspectral images should be superior to current technologies, due to the benefit of simultaneously exploiting two target-specific properties: the spectral target characteristics and the time-dependent target behavior We propose an algorithm that is in two steps The first step is the transformation of each of the hyperspectral images forming the sequence into a two-dimensional image using a known point-target detection-acquisition algorithm In the second step, target detection and tracking are performed by the means of time-domain processing A match-filter technique is used for the hyperspectral image transformation; a variance-filter algorithm is developed to detect the presence of targets from the temporal profile of each pixel while suppressing clutter-specific influences

Organic light-emitting display and fabricating method thereof

Abstract: An organic light-emitting display (OLED) is provided. The OLED comprises a plurality of pixels on a substrate. Each pixel on the substrate comprises a first electrode, an organic luminescent layer and a second electrode in sequence. The first electrode comprises a first subpixel region, a second subpixel region and a third subpixel region. The organic luminescent layer comprises a first organic luminescent layer and a second organic luminescent layer. The first organic luminescent layer is above the first subpixel region and the second subpixel region. The second organic luminescent layer is above the second subpixel region and the third subpixel region. The fabricating method of the OLED is disclosed in the specification too.

Super-resolution from unregistered aliased images

Abstract: Aliasing in images is often considered as a nuisance. Artificial low frequency patterns and jagged edges appear when an image is sampled at a too low frequency. However, aliasing also conveys useful information about the high frequency content of the image, which is exploited in super-resolution applications. We use a set of input images of the same scene to extract such high frequency information and create a higher resolution aliasing-free image. Typically, there is a small shift or more complex motion between the different images, such that they contain slightly different information about the scene. Super-resolution image reconstruction can be formulated as a multichannel sampling problem with unknown offsets. This results in a set of equations that are linear in the unknown signal coefficients but nonlinear in the offsets. This thesis concentrates on the computation of these offsets, as they are an essential prerequisite for an accurate high resolution reconstruction. If a part of the image spectra is free of aliasing, the planar shift and rotation parameters can be computed using only this low frequency information. In such a case, the images can be registered pairwise to a reference image. Such a method is not applicable if the images are undersampled by a factor of two or larger. A higher number of images needs to be registered jointly. Two subspace methods are discussed for such highly aliased images. The first approach is based on a Fourier description of the aliased signals as a sum of overlapping parts of the spectrum. It uses a rank condition to find the correct offsets. The second one uses a more general expansion in an arbitrary Hilbert space to compute the signal offsets. The sampled signal is represented as a linear combination of sampled basis functions. The offsets are computed by projecting the signal onto varying subspaces. Under certain conditions, in particular for bandlimited signals, the nonlinear super-resolution equations can be written as a set of polynomial equations. Using Buchberger's algorithm, the solution can then be computed as a Grobner basis for the corresponding polynomial ideal. After a description of a standard algorithm, adaptations are made for the use with noisy measurements. The techniques presented in this thesis are tested in simulations and practical experiments. The experiments are performed on sets of real images taken with a digital camera. The results show the validity of the algorithms: registration parameters are computed with subpixel precision, and aliasing is accurately removed from the resulting high resolution image. This thesis is produced according to the concepts of reproducible research. All the results and examples used in this thesis are reproducible using the code and data available online.

A Real-Time Large Disparity Range Stereo-System Using FPGAs

Abstract: In this paper, we discuss the design and implementation of a Field-Programmable Gate Array (FPGA) based stereo depth measurement system that is capable of handling a very large disparity range. The system performs rectification of the input video stream and a left-right consistency check to improve the accuracy of the results and generates subpixel disparities at 30 frames/second on 480 x 640 images. The system is based on the Local Weighted Phase-Correlation algorithm [9] which estimates disparity using a multi-scale and multi-orientation approach. Though FPGAs are ideal devices to exploit the inherent parallelism in many computer vision algorithms, they have a finite resource capacity which poses a challenge when adapting a system to deal with large image sizes or disparity ranges. In this work, we take advantage of the temporal information available in a video sequence to design a novel architecture for the correlation unit to achieve correlation over a large range while keeping the resource utilisation very low as compared to a naive approach of designing a correlation unit in hardware.

Subpixel registration directly from the phase difference

Abstract: This paper proposes a new approach to subpixel registration, under local/global shifts or rotation, using the phase-difference matrix. We establish the exact relationship between the continuous and the discrete phase difference of two shifted images and show that their discrete phase difference is a 2-dimensional sawtooth signal. As a result, the exact shifts or rotations can be determined to subpixel or subangle accuracy by counting the number of cycles of the phase-difference matrix along the frequency axes. The subpixel portion is represented by a fraction of a cycle corresponding to the noninteger part of the shift or rotation. The rotation angle is estimated by applying our method using a polar coordinate system. The problem is formulated as an overdetermined system of equations and is solved by imposing a regularity constraint. The tradeoff for imposing the constraint is determined by exploiting the rank constraint leading to a closed-form expression for the optimal regularization parameter.

Image distortion correction for lenticula misalignment in three-dimensional lenticular displays

Abstract: In manufacturing a lenticular display system, precise alignment of the lenticular sheet on the LCD panel may not be practically achievable. Hence, observed view images inevitably produce unwanted distortion. We propose a novel method to alleviate the display distortion of each observed view image in a lenticular 3-D display. We first derive the relationship between subpixel values on the LCD pixel array and the image to be observed at each viewing zone in terms of system design parameters and the viewer's eye position. Based on this relationship, we analyze the distortion between the observed and original view images. We then derive a compensation algorithm to minimize the distortion and generate high-quality 3-D images. To verify the proposed scheme, we examine displayed results from several 3-D images of synthetic and real scenes. The results demonstrate that the proposed scheme significantly reduces distortions and improves the image quality in the lenticular display system.

System for reducing crosstalk

Abstract: PROBLEM TO BE SOLVED: To reduce the crosstalk for display. SOLUTION: As to the crosstalk correction relating to a green subpixel G 1 , the crosstalk (from red to green) from the left subpixel is calculated on the basis of the pixel value of red and green and the crosstalk (from blue to green) from a right subpixel is calculated on the basis of a pixel value of blue and green. These two amounts of crosstalk are subtracted from the green value. The red pixel is adjacent to the blue subpixel of the left pixel (B 1-1 ) and therefore the correction is derived from B 1-1 and G 1 . The crosstalk relating to the blue pixel is derived from G 1 and R 1+1 by the same reason. The crosstalk correction value is obtained by mathematically processing these. COPYRIGHT: (C)2006,JPO&NCIPI

Subframe Video Synchronization via 3D Phase Correlation

Abstract: This paper introduces an accurate approach for synchronization (temporal alignment) between two video sequences of the same dynamic scene captured by uncalibrated cameras. With the homography assumption in spatial domain, an iterative procedure that successively achieves the alignment in space and time is proposed and its convergence is experimentally verified. Subframe accuracy is achieved by extending the existing image subpixel registration scheme to subframe video synchronization. In order to demonstrate the accuracy of the proposed method, we adopt a novel use of audio signals for their high sampling rate to obtain the synchronization ground-truth. The proposed video synchronization technique has potential use in temporal super-resolution, image-based rendering and tele-immersion.

Coupled Bayesian Framework for Dual Energy Image Registration

Abstract: Image registration for X-ray dual energy imaging is challenging due to the overlaid transparent layers (i.e., the bone and soft tissue) and the different appearances between the dual images acquired with X-rays at different energy spectra. Moreover, subpixel accuracy is necessary for good reconstruction of the bone and soft-tissue layers. This paper addresses these problems with a novel coupled Bayesian framework, in which the registration and reconstruction can effectively reinforce each other. With the reconstruction results, we can design accurate matching criteria for aligning the dual images, instead of treating them as multi-modality registration. Furthermore, prior knowledge of the bone and soft tissue can be exploited to detect poor reconstruction due to inaccurate registration; and hence correct registration errors in the coupled framework. A multiscale freeform registration algorithm is implemented to achieve subpixel registration accuracy. Promising results are obtained in the experiments.

Display device and color filter substrate

Abstract: A display device includes a pixel defined by a plurality of subpixels. The plurality of subpixels include: first and second red subpixels for displaying red; a green subpixel for displaying green; a blue subpixel for displaying blue; and a yellow subpixel for displaying yellow.

New method for subpixel image matching with rotation invariance by combining the parametric template method and the ring projection transform process

Abstract: The need for accurate and efficient computation of template matching prevails in many applications. However, a challenge in tem- plate matching is to obtain high accuracy that involves acceptable com- putation complexity and is robust to rotation. A new subpixel template matching approach that combines the parametric template method and the ring projection transform process is proposed. It not only achieves subpixel accuracy in location, but also offers rotation invariance in the subpixel template matching. Furthermore, our approach is conceptually simple, easy to implement, and very efficient because no iterative steps are involved. The simulated results show that our approach enjoys very high precision in the presence of image rotations. Experiments with real- world scenes demonstrate that the proposed method can reach subpixel accuracy for finding the distance between two target objects in the pres- ence of rotations and translations. This indicates that our approach is suitable for accurate on-line template matching with scene rotations and translations. © 2006 Society of Photo-Optical Instrumentation Engineers.

Displaying method and image display device

Abstract: In a displaying method for use in an image display, an original gray scale is divided into a higher gray scale and a lower gray scale. Further, the color subpixels are divided into two groups corresponding to the higher and lower gray scales, respectively. The gray scale to be expressed by each subpixel is calibrated by weighing the original higher or lower gray scale for the pixel and the adjacent pixels and summing up the results. The color shift problem due to different visual angles can therefore be solved.

BP Neural Network Based SubPixel Mapping Method

Abstract: A new subpixel mapping method based on BP neural network is proposed to improve spatial resolution of both raw hyperspectral imagery (HSI) and its fractional image. The network is used to train a model that describes the relationship between mixed pixel accompanied by its neighbors and the spatial distribution within the pixel. Then mixed pixel can be super-resolved by the trained model in subpixel scale. To improve the mapping performance, momentum is employed in BP learning algorithm and local analysis is adopted in processing of raw HSI. The comparison experiments are conducted both on synthetic images and on truth HSI. The results prove that the method has fairly good mapping effect and very low computational complexity for processing both of raw HSI and of fractional image.

Improved Bichromatic Display

Abstract: A display system includes a subpixelated display panel having subpixels in two saturated primary colors. In one embodiment, the primary colors are selected so as to be a substantially metameric pair for an achromatic color such as white. Information display efficiencies arise from utilizing a checkerboard arrangement for the two primary colored subpixels and from using subpixel rendering algorithms to render an image on the display. The bichromatic display may display a black and white image combined with a monochromatic image, or may provide the capability to overlay a first image from a first image source carried on a chromatic channel onto a second image from a second image source carried on a luminance channel, where the first image source detects light wavelengths that the Human Vision System is not sensitive to, such as infrared light. This latter embodiment of the bichromatic display system is suitable for night vision devices.