Keishi Hanahara

A real-time processor for the Hough transform

The Hough transform method for recognition can cope effectively with noisy backgrounds and gaps in boundaries. However, long computation time and large memory requirements have prevented it from being used in real-time applications. An architecture devised to solve those problems, with a focus on detecting straight lines, is presented. Examples are given of the use of an experimental hardware model for automatic inspection and measurement of objects in factories and laboratories. It took less than one second from picture input to straight line parameter reproduction for these examples. >

A circle-detection algorithm simulating wave propagation

Based on the analogy of the Hough transform and Huygenss principle, we present a circle-detection algorithm that numerically solves a two-dimensional wave equation using neighbor-based operations only, that is, Laplacian, frame addition, and multiplication of constants with frame contents, all basic functions of standard image processors. Because it does not use edge extraction, the algorithm detects circles even from low-contrast and blurred images. A comparison of point spread functions shows the algorithm to be equivalent to the weighted Hough transform but requiring much less computation. We applied the algorithm to disk-surface inspection of low-contrast and blurred microscopic images.

High-speed hough transform processor and its applications to automatic inspection and measurement

We have developed a processor with dedicated hardware for performing high-speed Hough transforms, to enable real time inspection and measurement of linear boundaries in gray scale images. The Hough transform method for recognition can cope effectively with noisy backgrounds and gaps in boundaries. However, long computation time and large memory requirements have been preventing it from being used in real time applications. This paper presents an architecture devised to solve those problems. It also provides examples of application to automatic inspection and measurement of objects in factories and laboratories. It took less than one second from picture input to straight line parameter reproduction for these examples.