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Low-latency histogram equalization for infrared image sequences - a hardware implementation

This work describes a hardware implementation of the contrast-limited adaptive histogram equalization algorithm (CLAHE). The intended application is the processing of image sequences from high-dynamic-range infrared cameras. The variant of histogram equalization implemented is the one most commonly used today. It involves dividing the image into tiles, computing a transformation function on each of them, and interpolating between them. The contrast-limiting is modified to facilitate the hardware implementation, and it is shown that the error introduced by this modification is negligible. The latency of the design is minimized by performing its successive steps simultaneously on the same frame and by exploiting the vertical blank pause between frames. The resource usage of the histogram equalization module and how it depends on its parameters has been determined by synthesis. The design has been synthesized and tested on a Xilinx FPGA. The implementation supports substituting other dynamic range reduction modules for the histogram equalization component by partial dynamic reconfiguration.

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This is the author-generated version of a paper I produced during the course of my work and which was published in the Journal of Real-Time Image Processing on 15 June 2011 (received 22 November 2010, accepted 13 May 2011), and is also known as DOI 10.1007/s11554-011-0204-y.

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