Method and apparatus for using spatial patterns for measuring mirror tilt angles in digital mirror devices

摘要

A method and system for indirectly measuring the tilt angle of micromirrors in a micromirror array. The method and system aims a coherent light beam through an aperture in a screen so that it reflects off of the surface of the micromirror array and creates a pattern of reflected light on the screen. The micromirror array is loaded with a pattern that has a uniform power spectral density (such as a random, aperiodic pattern or a frequency chirped sinusoidal spatial pattern) whereby certain micromirrors will be placed in the "on" position and the other micromirrors will be placed in the "off" position. By loading the micromirror array with a pattern having a uniform power spectral density distribution, the discrete nature of the resulting diffraction pattern is reduced and a pair of [sin(x)/x]<2 >patterns will be generated on the screen. These [sin(x)/x]<2 >patterns can be used to measure a variety of characteristics of the micromirrors, such as tilt angle, "roll", and deformation of the mirrors as they are tilted.