Measurement of the effective focal length by the centerline detection of light stripes

A composite method for detecting the centerline of straight light stripe is presented in this paper. In order to locate the image of stripe, a conditional dilation algorithm based on mathematical morphology is proposed to extract the regions of interest (ROI), and a shape factor is applied to eliminate the disturbance regions, so the straight light stripes are determined finally. Barycenter method is used to detect the centerline of stripe, and the outliers on the detected centerline are removed by a method based on probabilistic theory. The novel method has been used in the effective focal length measurement and the accuracy of measurement is better than 0.2 percent.