Microvision Inc. has shown a prototype of its pico-projector, which uses micro electro-mechanical systems (MEMS) to produce a digital projector in a palm-sized battery-powered unit. Unlike TI’s DLP technology with millions of tiny mirrors, Microvision uses a specially developed single-mirror MEMS chip.
Almost a decade in development, Microvision's pico-projector is based on a unique MEMS technology platform that uses laser scanning technologies borrowed from Microvision's successful bar-code reader product. Solid-state lasers combined in the same tiny module with a single digital micro-mirror simplify the projection system by not requiring any lenses. Control circuitry aims the lasers in a raster-scanning pattern, modulating the coherent beam onto each pixel of the display by moving the single mirror to keep the image in focus regardless of distance.
The mirror is round, about one millimetre in diameter, and deflected in both the X and Y planes simultaneously. As the mirror scans left-to-right and top-to-bottom, the three lasers are modulated so each pixel in the display receives the appropriate mixture of red, green and blue light to render the image accurately.
The mirror scans each pixel position using red, green and blue lasers. No focusing lens is required because the lasers produce razor-sharp points without external optics. This lets the full spectrum of colours and shades of grey be produced in a million-pixel display by a projector that's seven millimetres thick and has a total volume of only five cubic centimetres.
The main drawback of the pico-projector is that the display brightness is only 10 lumens, compared with 100 lumens or more for current digital projectors.
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