Effect of errors in optical correlators

Abstract

Given the interest in optical binary phase-only correlation implemented with magnetooptic spatial light modulators, an understanding of the effect of errors in system alignment and optical components is critical in obtaining optimum system performance. We present simulations of performance degradation in the presence of six errors divided into three groups. Under the first group, system errors, we simulate both translational and rotational misalignment of the input mask with the filter mask. Because system errors are mainly alignment errors, they are largely controllable by the designer. Next, we have errors that are partially controllable by the designer, which result from a combination of system and component nonidealities. These include a scale error caused by an incorrect focal length of the first set of transform lenses and an error in phase compensation owing to inexact component placement and lens focal length. Last, we have component errors that are not controllable by the designer, which result from the choice of spatial light modulator. These include imperfect contrast in both the input and filter masks and phase errors caused by the nonuniform flatness of the masks. The effects of each individual error are discussed, and the result of combining all six errors, under assumptions of reasonable tolerances and system parameters, are also presented. Conclusions are drawn as to which tolerances are most critical for optimum system performance.