An architecture for on-the-fly correction of radial distortion using FPGA

Abstract

In this paper, we introduce an FPGA implementation for correcting radial distortion which is non-linear and non-uniform, and inherently observed in images taken by wide angle lenses. In the implementation, the correction is performed in on-the-fly manner by employing a parallel architecture which focuses on efficient manipulation of look-up table (LUT) for coordinate translation: LUT decomposition and single-LUT-multiple-access method. 2D LUT is decomposed into three 1D LUTs to reduce the resource usage. The strategy of single-LUT-multipleaccess is inspired by the fact that there exists spatial and temporal proximity among the LUT accesses, even the nature of the mapping is non-linear and non-uniform. In addition, a way to eliminate redundancy, which occurs as the backward mappings and the interpolations are overlapping, is incorporated into the implementation. The series of effort aims to alleviate problems observed in conventional FPGA implementations of image handling algorithms, which are parallelization of function blocks for higher throughput and minimization of the number of access to off-chip memory. As the result, the corrected image to a distorted input frame can be stored within a vertical blank interval, with less usage of hardware resources and without unnecessary access to off-chip memory.