Subpixel Edge Detection And Estimation With A Line Scan Camera

A microprocessor-controlled line scan camera system for measuring edges and lengths of steel strips is described, and the problem of subpixel edge detection and estimation is considered based on measurements of gray values of the line images at a limited number of pixels. The true edge locations may be between pixels. A two-stage approach is presented. At the first stage, a simple template matching method is used to place the estimated edge point to the nearest pixel value. Three second-stage methods are examined, which are designed for subpixel estimation. In the case of nonstationary Poisson noise, a recursive maximum likelihood method is proposed. Monte Carlo simulations for Gaussian and Poisson noise indicate that subpixel estimation accuracy can be obtained if the noise level is not very high.