Quality control of small mechanical pieces using optical correlation techniques

A holographic matched filtering technique is used to control the contour shape of small mechanical elements. The optimization of the spatial filter leads to a well-defined response curve which is used to calibrate the output of the optical correlator in terms of shape error. It is shown that the techniques of computer holograms offer the widest possibilities to perform this optimization. The basis of the technique is presented together with a few simple examples showing the possibility of detecting shape errors of a few microns (less than 1% of the controlled dimension).