Research on the image definition criterion on the high accuracy image measurement system

In the high accuracy measurement system based on image, it is very important for the object plane to realize high accuracy complete focusing. In order to increase the focusing precision, this article proposed one kind of image definition criterion algorithm which is based on the image interpolation. Firstly, the image which carrys on interpolation processing by cubic spline functions can improve the sampling of the object plane, so the grey value change of the image edge which causes by the minimal defocusing amount can be full developed; Then, use square gradient function carries on the interpolation image for image definition criterion. The experimental result indicated that this method can enhance the focusing precision of the system object plane effectively, so the object plane adjustment precision can be promoted.