Research on the Adjustable Magnification of Vision Measurement Module Integrated in Precision Assembly System

摘要

To satisfy the demand of multi-scale measurement of miniature parts, a vision measurement module with zoom lenses was set up for evaluation and final integration in precision assembly system. A new template with circular patterns of different diameters was designed for calibration of zoom-lens camera. The principal point was determined based on the focus-of-expansion method, and the orientational deviation of image was experimentally studied in the zoom process. Pixel equivalent was calculated by circular patterns of different diameters and its repeatability was tested during the zoom process. Experimental results indicated that the principal point offset is less than 0.6pixel, and the measurement error caused by orientational deviation of image is negligible for most of the assembly tasks. Due to the good repeatability of pixel equivalent, off-line calibration data can be used in the actual measurement process. When the much higher accuracy was required during assembly, the online calibration could be employed.