Ultra-compact micro-electro-mechanical laser beam scanner for augmented reality applications

Abstract

Laser beam scanners (LBS) are an emerging micro-display technology for augmented reality (AR) head-mounted displays (HMD), enabling small-form-factor and low-power display units with large field of view (FOV) and daylight-bright luminance, that are compatible with a large range of optical combiner technologies such as waveguide or holographic combiners. We have developed an ultra-compact and lightweight LBS comprising an integrated laser module, a single 2D micro-electro-mechanical systems (MEMS) mirror, and a molded interconnect device (MID). The compact integrated laser module contains red, green, and blue (RGB) semiconductor laser diodes (LDs) and a common system of microlenses for beam collimation, all enclosed in a single hermetically sealed package. The three LDs are mounted onto a single submount using a novel high-precision laser die bonding technique. This high-precision LD placement allows the use of collimation lenses that collimate all three laser beams simultaneously in contrast to separate lenses with additional active alignment steps for each color. No additional optical components such as mirrors and dichroic beam combiners are required—instead, the color channels are overlapped on a pixel-by-pixel basis by a “software beam combination” laser pulse timing algorithm. Both laser module and MEMS mirror are assembled on an MID with printed circuit board (PCB), which is connected to a driver board including video interface. We also give an outlook to future generations of fully mass manufacturable LBS systems with even smaller form factor.