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UBC Theses and Dissertations

Single exposure high dynamic range imaging with a conventional camera using cross-screen filters Rouf, Mushfiqur

Abstract

Real world scenes often contain both bright and dark regions, resulting in a high contrast ratio, beyond the capabilities of conventional cameras. For these cases, High Dynamic Range or HDR images can be captured with expensive hardware or by taking multiple exposures of the same scene. However, these methods cost extra resources -- either spatial or temporal resolution is sacrificed, or more than one piece of hardware is needed. In this thesis, a novel technique is presented that is capable of capturing High Dynamic Range images in only one exposure of a conventional camera. We observe that most natural HDR images have only 2-5% pixels that are too bright compared to the rest of the scene to fall inside the dynamic range of a conventional camera. Our method spreads energy from these bright regions into the neighboring unsaturated pixels by defocus blurring. Bright pixels still get clipped in the captured image due to saturation of the sensor; but some information about these clipped pixels gets encoded or multiplexed in the form of superimposed glare patterns in the image. Frequency preservation and decoding of this information can be further improved by using a cross-screen filter instead of using defocus blur. Superimposed glare patterns are recovered with the help of natural image statistics. These glare patterns provide information about how much energy there is in the saturated pixels, which allows a tomography-like reconstruction of the saturated regions. Once the saturated regions are known, the rest of the image can be restored by removing the estimated glare patterns.

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Attribution-NonCommercial-NoDerivatives 4.0 International

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