A light-pen single-camera 3D coordinate vision measurement system is introduced in this paper. By analysising characteristics of the system image

a digital method for recognizing the elliptical light spot images of the measured control points is proposed. On the basis of the pixel number of a measured control point' elliptical light spot image contour

too large and too small light spot images can be eliminated. Then

using the method based on the evaluation for elliptical profile error

the measured control points' elliptical light spot image can be recognized. The algorithm for this method is given

and the experimental results show that this algorithm is simple

fast

easy to realize and practical to the vision inspection system with circular measured control points. Compared with the common method

which applies the filter mounted on the CCD camera lens to segregate the noise bright spot image in the image background

it has certain theoretical significance and practical project value.