Abstract:

A non contact, high precision shaft diameter measuring technique was proposed combining the CCD camera calibration and subpixel edge detection. Based on the improved distortion model of ZHANG Zhengyou, the parameters of the CCD camera were calibrated fixing the calibration board by a specially designed fixture to ensure the agreement between the clamped state of the measure shaft and the calibrated external parameters. A fitting form of subpixel edge detection algorithm was used to localize the two edges in the shaft image. An expression to determine the real shaft diameter from the pseudodiameter was derived. The comparison of the measuring results with those obtained by the traditional precision measuring tool showed that for the basic dimension of measured shaft diameter 35~75 mm the average error of the proposed technique is about 0.02 mm.

Key words: technology of instrument and meter, shaft diameter measurement, CCD camera, non contact measurement