Grayscale laser image formation using a programmable binary mask

Abstract

We present grayscale laser image formation from a programmable binary mask using a digital micromirror device (DMD) followed by a telescope with an adjustable pinhole low-pass filter. System performance was measured by comparing the intensity conformity with respect to the target image and by the energy conversion efficiency. A theoretical analysis of image precision proved high-precision image formation and inspired the iterative pattern refinement process based on the point spread function of a single DMD pixel to seek optimized image quality. We derived the diffraction efficiency formula of the DMD and discussed the overall system energy efficiency with operation wavelengths. Actual image precision performance was evaluated by measuring the root-mean-square (RMS) error of a series of sinusoidal-flattop profiles with different system bandwidths. We produced grayscale laser images with different spatial spectral content using intensity profiles of Laguerre-Gaussian, Hermite-Gaussian, and Lena-flattop beams. Measured RMS errors of all examples of various bandwidths were consistent with the image precision of the sinusoidal reference patterns. The ripple effect caused by the sharp-edged pinhole was the major contributor to the residual error in the output images. Error histograms had a zero-mean Gaussian distribution with standard deviation equal to the value of the RMS error.