Realization of augmented reality (AR) solutions is key towards the much-needed integration of digital content into the real world. This seamless integration of digital content with the real world in AR devices is achieved by displaying the information using a suitable projector in the field-of-view (FOV) of the user. One of the most practical solutions to realize this is a laser beam scanner (LBS) projector combined with a diffractive optical waveguide. Features such as a small form factor, high brightness, large color gamut, and low power-consumption make LBS a popular choice as the light engine for the emerging consumer market for AR displays where the primary focus is on obtaining a stylish wearable rather than an unwieldly head mounted device. As should be the case for any AR/VR/MR display, LBS plus waveguide solution must be evaluated against the IEC 60825- 1:2014 standard for a typical use case. In this manuscript, we will first describe a typical AR solution, a TriLite Trixel® 3 LBS plus a waveguide combiner. We will discuss the operating principle of such a device. Based on that we shall highlight stepwise the key considerations in such a system for ensuring a Class 1 operation in a typical AR use case as per the IEC 60825-1:2014 requirements.
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.
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