A CMM-based automatic measurement method for surface area

A method combining coordinates measuring method with digital image technique was introduced to measure area of irregular particular regions. The coordinate measuring machine (CMM) was used to control coordinate positions of charge-coupled device (CCD) camera for recording image of measured region. Image processing technique with image segmentation and mosaic was used to calculate area. Firstly transform coefficient between a pixel in an image and real area in square meter was calibrated by a plane templet. Secondly image distortion due to distance from CCD camera to different locations of curved surface was corrected using the concept of perspective projection in computer graphics. And then curved-surface spread was given as a modification of curved surface effect to promote measurement accuracy. Both the relative error and the repeatability error are less than 0.5% in this method.