Abstract: An apparatus for producing a fringe pattern having variable parameters. The apparatus includes a light source which directs light to a first beamsplitter which transmits a first portion of the light beam along a first light path and reflects a second portion of the light beam along a second light path. The apparatus is further configured to cause the first and second light paths to converge at a second beamsplitter. A half-wave retarder is provided along the first light path in order to rotate the plane of polarization of the light traveling along the first light path by approximately 90.degree. such that the light traveling along the first and second light paths creates a fringe pattern upon convergence at the second beamsplitter. The apparatus is further configured such that one or more of the contrast, temporal frequency, spatial frequency, and orientation of the fringe pattern can be selectively varied.