CoherentOptics is a freeware program for constructing optical filters and for simulating the passage of coherent light of one color and polarization at a time. This simulated propagation through an optical system, uses Fresnel optics, but no ray tracing. The magnitude and phase information of the propagating light is saved as Real and Imaginary parts of a complex number. These arrays of numbers can be saved, and manipulated in many ways. It is designed to compliment a research program involving image manipulation and holographic recognition, but seems to be useful in other ways.