A color combination method with separate secondary light combination structure for coherent illumination of digital-micro-mirror devices

Abstract

The combination of three visible lasers with different wavelengths (Red/Green/Blue) illuminates a digital micro-mirror device (DMD) to generate color images, which is the core of a color imaging or display system. However, conventional optical configuration methods using a light-coupling combination produce the position mismatch of three images generated by DMDs because the diffraction angle of three wavelength beams is different. In this work, we propose a new color combination method using a separate secondary beam-combination structure (SSBCS) to achieve the complete mismatch of three images. The SSBCS can freely control the beam direction of a laser and the image shift is controllable, which can be used to compensate for the position mismatch of three images. Experiments indicate that the proposed method yields a high-quality combination of three images. The proposed methods can directly solve the color combination issue of three visible beams in an optical hardware aspect without the soft-compensation of the DMDs.