Long Range Pupil Location Algorithm Based on the Improved Circle Fitting Method

Since the pupil will show abnormal contraction or expansion after taking drugs, the technology of long range pupil diameter detection can be used for rapid screening of drug users. In this paper, a long range pupil location algorithm is proposed based on the improved circle fitting method. Firstly, the improved histogram-based binarization method is used to obtain candidate pupil contours, and non-pupil contours are filtered according to the shape or size. Then, the ROI is extracted from the original image according to the pupil contours, and the facula contours are extracted and filled by the features, such as gray value, size and position. Finally, an improved circle fitting method is used to obtain an accurate pupil position. The experimental results on CASIA-IrisV4-Distance database show that the proposed algorithm can locate the pupil more accurately and the average deviation of center and radius is smaller compared with the existing pupil detection algorithms.