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Anti-Aliasing Snapshot HDR Imaging Using Non-Regular Sensing

Teresa Stürzenhofäcker, Moritz Klimm, Jürgen Seiler, André Kaup

Abstract

Snapshot HDR imaging is essential to capture the full dynamic range of a scene in a single exposure, making it essential for video and dynamic environments where motion prevents the use of multi-exposure techniques or complex hardware set-ups. This work presents a snapshot HDR imaging sensor that is based on spatially varying apertures, implemented by combining two differently sized prototype pixels. The different light integration areas physically extend the dynamic range towards the lower end, compared to a standard high resolution sensor. A non-regular pixel arrangement is suggested, to mitigate aliasing and overcome a loss in spatial resolution that is associated with increased light integration area of the larger prototype pixel. Subsequent reconstruction in the Fourier domain, where natural images can be sparsely represented allows to recover the image with high detail. The image acquisition approach with the proposed non-regular HDR sensor is simulated and analysed with special emphasis on the spatial resolution. The results suggest the snapshot HDR sensor layout to be an effective way to acquire images with high dynamic range and free from aliasing artefacts.

Anti-Aliasing Snapshot HDR Imaging Using Non-Regular Sensing

Abstract

Snapshot HDR imaging is essential to capture the full dynamic range of a scene in a single exposure, making it essential for video and dynamic environments where motion prevents the use of multi-exposure techniques or complex hardware set-ups. This work presents a snapshot HDR imaging sensor that is based on spatially varying apertures, implemented by combining two differently sized prototype pixels. The different light integration areas physically extend the dynamic range towards the lower end, compared to a standard high resolution sensor. A non-regular pixel arrangement is suggested, to mitigate aliasing and overcome a loss in spatial resolution that is associated with increased light integration area of the larger prototype pixel. Subsequent reconstruction in the Fourier domain, where natural images can be sparsely represented allows to recover the image with high detail. The image acquisition approach with the proposed non-regular HDR sensor is simulated and analysed with special emphasis on the spatial resolution. The results suggest the snapshot HDR sensor layout to be an effective way to acquire images with high dynamic range and free from aliasing artefacts.
Paper Structure (7 sections, 4 equations, 5 figures, 2 tables)

This paper contains 7 sections, 4 equations, 5 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Image Acquisition model
  3. Proposed High Dynamic Range Sensor Layout
  4. HDR Imaging with Spatially Varying Pixel Sizes
  5. Regular and Non-Regular Subsampling
  6. Simulation and Results
  7. Conclusion and Outlook

Figures (5)

  • Figure 1: The proposed, sensor Layout in (a) with non-regular orientation of small pixel (green) and large pixel (red). In contrast, the regular layout in (b) with constant prototype pixel orientation.
  • Figure 2: Extended dynamic range of the proposed HDR sensor.
  • Figure 3: Impact of pixel placement on the spatial resolution. The top row shows a reference HR sensor (left), the regular HDR sensor (middle), and the proposed non-regular sampling pattern (right) which are used to sample a striped reference image. The middle row depicts the corresponding sampled image. Sampling with the HR sensor yield an output equivalent to the input reference. The respective Fourier spectra are shown in the bottom row.
  • Figure 4: Impact of saturation and noise thresholds. Readings from small pixels only (left), readings from large pixels only (right), suggested HDR sensor combining both pixels (center). Blue: under-exposure; Red: over-exposure. Reinhard tone mapping is applied for visualisation reinhard.
  • Figure 5: Sampling a synthetic zoneplate with overlayed, horizontal gradient with the suggested HDR sensor in the regular and non-regular layout. (Please pay attention, additional aliasing may be caused by printing or scaling. Best to be viewed enlarged on a monitor.)