Thin-form-factor red-green-blue laser scanning system for full-color laser image projection

Abstract

A thin-form-factor laser scanning system composed of a planar-type laser source with a waveguide-type combiner and a micro-electromechanical systems (MEMS) scanning mirror was developed. The laser source and MEMS mirror were mounted on a common substrate, resulting in a thin and small form factor. The scanning laser beam comprised coaxially combined red, green, and blue beams, capable of projecting a full-color laser scanning image. The system design incorporated a projection image distortion analysis, which assumed a raster scan scheme, whereby the horizontal fast-scan direction lay in the plane defined by the incident beam direction and the direction normal to the common substrate, and the vertical slow-scan direction lay in a plane perpendicular to the horizontal scan plane. The incident angle of the laser beam on the MEMS mirror was kept small (less than 45°). Three types of laser scanning systems were constructed to provide scanning laser beams with different beam directions by replacing the detachable beam-deflection modules as follows: (1) Simple mirror type directing the beam opposite to the incident beam, with a system height of 4 mm; (2) Beam splitter type directing the beam perpendicular to the incident beam, with a system height of 6 mm; and (3) Prism mirror type directing the beam forward relative to the incident beam, with a system height of 8 mm. The systems had distinctive features rendering each suitable for different applications. Thus, these laser scanning systems offer compact solutions for laser scanning image projection.