High dynamic range

About: High dynamic range is a research topic. Over the lifetime, 4280 publications have been published within this topic receiving 76293 citations. The topic is also known as: HDR.

Adaptive fringe projection technique for high-dynamic range three-dimensional shape measurement using binary search

Abstract: Fringe projection profilometry is a popular optical method for three-dimensional (3-D) shape measurement because of its high accuracy, fast measurement speed, and full-field inspection nature. However, due to the limited dynamic range of the digital camera, saturated pixels in the captured images will lead to serious phase errors and measurement errors when the measured object has a drastic texture variation. To deal with such a problem, an adaptive digital fringe projection technique for high dynamic 3-D shape measurement is proposed. In this method, phase-shifting fringes are adaptively generated with the aid of a coordinates mapping process and binary-search technique to eliminate saturation. Compared with previous adaptive fringe projection techniques, the camera response function and homographic mapping between the camera and projector are not needed, making the whole measurement easier to carry out and less laborious. Experiments validate the effectiveness and superiority of the proposed method for high-dynamic range 3-D shape measurement.

Enhanced energy detection for multi-band spectrum sensing under RF imperfections

Abstract: In this paper, we study simultaneous multi-channel spectrum sensing in cognitive radio context. The sensing receiver RF front-end is assumed to deploy wideband multi-channel IQ down-conversion which is well-suited for highly-integrated circuit implementations. Such RF front-end is, however, also prone to several RF impairments, such as IQ imbalance, which leads to mirror-frequency cross-talk and can thus considerably degrade the sensing performance. Assuming that the individual channel sensing is building on energy detection, we first analyze the spectrum sensing performance of the multichannel sensing receiver in terms of false alarm and detection probabilities. The analysis shows that IQ imbalance is especially harmful in terms of false alarms stemming from the mirror-channel crosstalk, and is greatly emphasized when the overall down-converted signal has high dynamic range. Motivated by this, we present an efficient digital compensation scheme, called energy correction method, where the sensing statistics of any particular channel are properly adjusted based on the corresponding mirror-channel statistics such that the effect of the crosstalk is minimized. Optimum minimum mean-squared error (MMSE) solution for the energy correction processing is first derived, complemented then with a practical low-complexity sample estimator. Extensive computer simulations demonstrate that under various parameter settings for IQ imbalance and receiver dynamic range, the proposed scheme yields sensing performance practically identical to the IQ imbalance free reference performance. Thus the proposed method offers feasible RF impairment-aware energy detection solution for practical multichannel sensing receivers.

Comprehensive Fast Tone Mapping for High Dynamic Range Image Visualization

Abstract: In this paper, we present a comprehensive tone reproduction curve based operator for the fast visualization of high dynamic range images. Image reproduction is a highly subjective process and different users will have very different preferences even for the same image. Therefore, a really useful tone-mapping tool for high dynamic range images should be fast and interactive, with which users can interactively adjust the mapping parameters and instantly visualize the results. Furthermore, there should be as few adjustable parameters as possible, and equally important, the parameters should have a clear, intuitive and straightforward relationship with the appearance of the mapped images to guide the users to adjust the parameters. Based on these requirements, we have developed a comprehensive tone reproduction curve based mapping technology. Our technique has two intuitive variables, which can be adjusted at an interactive speed even for very large images. One parameter controls the overall brightness of the reproduction and the other adjusts the detail and contrast 1 of the result. A piece of easy to use high dynamic range image visualization software that implements our operator is publicly available.

Optical receiver with high dynamic range

Abstract: An optical coupling assembly having an optical receiver that exhibits extended dynamic range, and, more particularly, an optical receiver that is integrated with a Variable Optical Attenuator (VOA) to extend the dynamic range of the receiver.

Hdr Imaging for Feature Detection on Detailed Architectural Scenes

Abstract: 3D reconstruction relies on accurate detection, extraction, description and matching of image features This is even truer for complex architectural scenes that pose needs for 3D models of high quality, without any loss of detail in geometry or color Illumination conditions influence the radiometric quality of images, as standard sensors cannot depict properly a wide range of intensities in the same scene Indeed, overexposed or underexposed pixels cause irreplaceable information loss and degrade digital representation Images taken under extreme lighting environments may be thus prohibitive for feature detection/extraction and consequently for matching and 3D reconstruction High Dynamic Range (HDR) images could be helpful for these operators because they broaden the limits of illumination range that Standard or Low Dynamic Range (SDR/LDR) images can capture and increase in this way the amount of details contained in the image Experimental results of this study prove this assumption as they examine state of the art feature detectors applied both on standard dynamic range and HDR images