The Alabama A & M University Department of Physics Optics and Information Processing

Binary Phase Only Filter

Binary phase only spatial filters simulate correlation against a spatial light modulator (SLM). This filter includes only phase information, since we can choose to output either phase or amplitude. If we choose amplitude (binarize to 0 and 1) we will produce a large DC (0 frequency spike in the correlation plane). This is to be avoided, and we therefore choose a phase only configuration.

Such a system would look something like:

For example take the Alabama A & M University Logo:

We want to find the large letter "A":

We make a filter of "A" (using msf.m) and we then binarize it to -1 and 1 (using binarize.m) :

We then simulate the optical correlator (using optcorr.m), and finally obtain the magnitude squared (we normally use square law detectors, using magsqu.m):

Notice that the correlation peak is much more narrow that that of the matched spatial filter.