A Compact System for Real-Time Detection of Line Segments

Abstract

In this paper, we describe a compact circuit for real-time detection of line segments using the Line Hough Transform (LHT). The LHT is a technique to find out lines in an image. The LHT is robust to noises, but requires long computation time. The circuit calculates (1) r and θ of lines (r is the distance from the origin to a line and θ is the angle of the line) by the LHT units in parallel, and (2) start and end points of the lines by the other units which are completely pipelined with the LHT units. With this parallel and pipeline processing, the circuit can detects line segments by π/512 angle steps in a standard size image (640 × 480) in real-time. This circuit was implemented on an off-the-shelf PCI board with one Field Programmable Gate Array (FPGA) chip. The size of the circuit is 45% of the chip, which makes it possible to implement other circuits for higher level processing of object recognition on the same chip, or the performance can be improved twice by using the rest of hardware resources. 2 Previous Works Many approaches by software to reduce the computational complexity have been proposed, and efficient algorithms to extract line segments have also been re