Efficient ASIC and FPGA implementations of IIR filters for real time edge detection

To reduce the computation cost, Deriche (1987, 1990) extended the work from Canny (1986) on optimal edge detectors to the use of recursive filters. Nevertheless, this cost is still too high for real time implementation on FGGA circuits. Here, we optimized both the algorithmic and architectural aspects of the original Deriche filter. A new organization of the filter is proposed at the 2D and 1D levels which reduces the memory size and the computation cost by a factor of two for both software and hardware implementations. We prove that the use of only 3 bits to code the scale parameter does not reduce the quality. The result from this choice is that the first order recursive filter which is the basic block of the entire architecture can be built with only 4 adders. The architecture of a 10 Mpixels/second filter on an unique FPGA is described.