The influence of additional filters upon the output of an optical correlator is studied for the case of a spatial filter measuring the size of rectangles. Addtional filters leading to increased sensitivity are derived by means of a series expansion. One type of additional filter, consisting of several transparent slits, yields a linear relation between output signal and the deviation from the desired size. The other additional filter, effecting a quadratic output characteristic, is a properly dimensioned bandpass. Experimental results demonstrate the enhancement of sensitivity achieved with additional filters. As this method can easily be extended to a correlator measuring the diameter of circular apertures, additional filters may be of interest in the field of automatic production control.
© 1973 Optical Society of America
Equations on this page are rendered with MathJax. Learn more.