An FPGA Implementation of Hough Transform using DSP blocks and block RAMs

Xin Zhou, Yasuaki Ito, Koji Nakano


Since FPGA chips maintain relatively low price and its programmable features, it is widely used in those fields which need to update architecture or functions frequently such as communication and education areas. Especially, in mobile devices that recently require the ability to perform computation such as real-time image processing, FPGAs are promising devices. The main contribution of this paper is to present a new FPGA architecture for the Hough transform that identifies straight lines in a binary image. Recent FPGAs have hundreds of embedded DSP blocks and block RAMs. For example, Xilinx Virtex-6 Family FPGAs have a DSP48E1 block, which is a configurable logic block equipped with fast multipliers, adders, pipeline registers, and so on. They also have a dual-port memory with 18Kbits as a block RAM. One of the most important key techniques for accelerating computation using FPGAs is an efficient usage of DSP blocks and block RAMs. Our new architecture for the Hough transform uses 178 DSP48E1 blocks and 180 block RAMs with 18Kbits that work in parallel. As far as we know, there is no previously published work that fully utilizes DSP blocks and block RAMs for the Hough transform. Roughly speaking, a conventional sequential implementation performs 180m voting operations for m edge points. Our architecture performs voting operations in parallel, and outputs identified straight lines in m+97 clock cycles. Since 180m voting operations are performed using 178 DSP48E1 blocks, the lower bound of the computing time is m clock cycles. Hence our implementation is close to optimal. The implementation results show that the Hough transform for a 512×512 image with 33232 edge points can be done in only 135.75µs.


Image processing; Line detection; Hough transform; FPGA; Embedded DSP blocks; Embedded block RAMs

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