No abstract

The combination of laser light sources and MEMS technology enables a range of display systems such as ultra small projectors for mobile devices, head-up displays for vehicles, wearable near-eye displays and projection systems for 3D imaging. Images are created by scanning red, green and blue lasers horizontally and vertically with a single two-dimensional MEMS. Due to the excellent beam quality of laser beams, the optical designs are efficient and compact. In addition, the laser illumination enables saturated display colors that are desirable for augmented reality applications where a virtual image is used. With this technology, the smallest projector engine for high volume manufacturing to date has been developed. This projector module has a height of 7 mm and a volume of 5 cc. The resolution of this projector is WVGA. No additional projection optics is required, resulting in an infinite focus depth. Unlike with micro-display projection displays, an increase in resolution will not lead to an increase in size or a decrease in efficiency. Therefore future projectors can be developed that combine a higher resolution in an even smaller and thinner form factor with increased efficiencies that will lead to lower power consumption.

A high-frequency resonant horizontal scanner and a linearly driven vertical scanner at display frame rates can create a 2-D raster for video display. The combined motion of the two scanners forms a sinusoidal raster in the vertical direction where the raster line spacing is uniform only at the center and becomes progressively nonuniform towards the left and right edges of the display screen. Nonuniformities degrade the image quality and can be corrected by the addition of a third scanner to the system. Last year we reported the requirements and some of the early results in our MEMS-based raster correction scanner development effort. Since then, a lot of progress was made and the scanner was successfully incorporated into an SXGA resolution helmet-mounted display system. In this paper we report the results of thick copper coil development, new coil and magnet design for electromagnetic actuator, thermal flatness testing, new mounting design, and finally the performance measurements for the HMD system with a raster correction scanner.