MEMS digital camera

MEMS technology uses photolithography and etching of silicon wafers to enable mechanical structures with less than 1 mm tolerance, important for the miniaturization of imaging systems. In this paper, we present the first silicon MEMS digital auto-focus camera for use in cell phones with a focus range of 10 cm to infinity. At the heart of the new silicon MEMS digital camera, a simple and low-cost electromagnetic actuator impels a silicon MEMS motion control stage on which a lens is mounted. The silicon stage ensures precise alignment of the lens with respect to the imager, and enables precision motion of the lens over a range of 300 mm with < 5 mm hysteresis and < 2 mm repeatability. Settling time is < 15 ms for 200 mm step, and < 5ms for 20 mm step enabling AF within 0.36 sec at 30 fps. The precise motion allows COTS optics to maintain MTF > 0.8 at 20 cy/mm up to 80% field over the full range of motion. Accelerated lifetime testing has shown that the alignment and precision of motion is maintained after 8,000 g shocks, thermal cycling from - 40 C to 85 C, and operation over 20 million cycles.