Abstract: In the traditional pill defect detection method based on machine vision, the pill image is mostly shot from the right above the pill by a single camera, which is difficult to detect tablets with fracture between upper and lower surfaces and unqualified thickness effectively, the thickness of this kind of defective tablets may be different from that of standard tablets. For this kind of situation, this paper presents a method of tablet thickness detection based on binocular vision. In this method, the binocular camera is placed directly above the tablet and the image of the tablet is collected. Canny operator is used to extract the edge features of tablets for stereo matching, the parallax of tablets is calculated by using the principle of binocular vision triangulation, and the depth information of the tablet is calculated according to the parallax, the depth difference between standard tablets and tablets with transverse rupture is calculated, the tablets with thickness defects are detected. The precision of the experimental measurement results is up to 0.1 mm, which has a high detection accuracy and meets the requirements of detection accuracy, indicating that the method has good applicability and reliability.

Key words: defect detecting, Canny operator, binocular vision, stereo matching