Nippon Signal Co Ltd exhibited an SVGA (resolution: 800 x 600) compact color projector that is as small as a cigarette case at Exhibition Micromachine/MEMS.
Nippon Signal exhibited a prototype with the same resolution at the previous exhibition, but it was about the size of a lunch box (approximately 180 x 120 x 50mm). This time, the company reduced the size of the projector to about 1/8 (90 x 55 x 20mm) by reducing the size of the optical system such as lenses and the MEMS scanner that scans laser light beams in RGB colors.
In addition to the size reduction, the quality of displayed images was significantly improved. Nippon Signal's presentation signifies that MEMS scanner-based compact projectors may be commercialized soon.
With the cooperation of an optical device manufacturer, Nippon Signal designed the proprietary optical parts such as lenses. For example, the company prototyped a prism lens exclusively for projectors that was adopted to correct the distortion of light emitted from a semiconductor laser diode. As a result, the length of the optical path of the blue laser beam was reduced to approximately 1/4, compared with that of the prototype displayed at the previous exhibition.
The new projector used the semiconductor laser for the green laser light source, instead of the diode pumping solid state (DPSS) laser, which was used in the previous prototype. The adoption of semiconductor laser eliminated the need for an acoustic optical modulator (AOM), which was used along with DPSS, because the semiconductor laser light can be modulated by itself at a high speed.
The company also reduced the size of the MEMS scanner module through the size reduction of the MEMS scanner and the layout optimization of a magnet used for electromagnetic actuation.
Two MEMS scanners in the new product scan the laser light beam in the horizontal and vertical directions, both of which measure 10 x 10 x 5mm. The two MEMS scanners used in the previous prototype measured 23 x 14 x 25mm and 10 x 15 x 4.6mm.
The magnet was placed on the silicon substrate in the latest prototype, whereas it was located outside the substrate in the previous prototype.