US Patent 9350921 Structured illumination projection with enhanced exposure control

A method for controlling a structured illumination pattern generating portion is provided for illuminating a workpiece during an image acquisition by a camera in a precision machine vision inspection system. A controllable spatial light modulator (e.g., a digital light processing projector) is part of the generating portion for generating the structured illumination pattern. The pattern may comprise an array of stripes including a sinusoidal gray level intensity variation across each stripe. An overall image exposure is increased by repeating a complete structured illumination pattern generation iteration, including gray level variation, a plurality of times during an image integration period. Structured illumination microscopy techniques for determining a workpiece surface profile may benefit, wherein multiple (e.g., 3 or 4) images are acquired at respective focus positions to be analyzed, by using the method to project a different phase of a structured light pattern for each of the multiple images.