Size and efficacy are two of the main challenges of an AR display. A compact form factor and low power consumption are highly desirable in AR glasses. Self-emitting display technologies such as OLED and MicroLED do not need illumination thus enabling simpler and smaller optics, but their efficacy is quite low, especially for pixel sizes of 5um or below. Spatial Light Modulator (SLM) based technologies, such as DMD, LCoS (Liquid Crystal on Silicon), and LBS (Laser Beam Scanning), take advantage of high efficacy light sources and can achieve a high brightness AR display combining low power consumption and high pixel density, which is highly preferable in many applications. The DMD, together with the efficient and ever-improving LED light source, has been highly favored in the battery-powered portable projection display market, due to its high efficacy in a compact form factor as well as its insensitivity to polarization. Here we present a compact optical engine architecture for AR glasses, taking into consideration both size and efficacy. The design simplifies the traditional DMD illumination to a compact size targeting a thin profile similar to a backlit LCD. This compact size is achieved with a small compromise to engine efficacy. Multiplying the pixel density with a glass plate actuator offers a performance improvement that easily justifies the slight increase in size. This architecture offers an excellent optical engine option for AR glasses which is both compact and high performance.
|