Accuracy of determination of three-dimensional coordinates and strain of press forming products by image sensing camera

摘要

A method for calculating the three-dimensional coordinates and strain of press forming products using an image sensing camera is shown, and the measurement error is determined. First, a method for determining two kinds of parameters is presented; one kind of parameter represents the positions and angles of the camera (extrinsic parameters), and the other kind represents the focal length and the shift of principal point of the lens (intrinsic parameters). Second, the measurement error, that is, the difference between the true value and the measured one, is determined using a numerical model which gives the coordinates of the object point and the imaged one on the image sensing camera calculated in advance by geometric optics. The error can be decreased when the intrinsic parameters are introduced and the technique for determining the boundary of a black and white target on the sensor surface is improved. In a press forming experiment, the maximum error of measurement is 0.143mm, and the average error is 0.0992mm at a distance L = 2680mm of camera to the product.