MEMS-based laser projection system enables high resolution 3D scanning
This new driving scheme allows switching of the target positions of the laser beam quickly, and a dynamic adjustment of the scanning speed is also possible. 3D cameras or miniaturized laser projectors equipped with this technology offer higher resolution and make innovative solutions possible, such as robot eyes with sharp vision or compact cell phone projectors with high image quality.
A camera with LinScan technology potentially imitates the human visualization system by first scanning the surroundings and then resolving interesting objects with greater precision, explains Thilo Sandner, Project Manager at Fraunhofer IPMS
The LinScan technology poses a tremendous developmental leap for application in compact laser projectors as well. Unlike the double-resonant scanning principle used so far for pico-projectors, where the mirror oscillates in a sinusoidal manner with a frequency predefined by the geometry of the component, LinScan makes it possible for the laser beam to jump from line to line with a flexible scanning speed. Image resolutions of SVGA (800 x 600) and more become possible with miniaturized architectures.
LinScan is based on the manufacturing technology developed by Fraunhofer IPMS for resonant microscanners. The idea is to tilt the drive combs of the hitherto existing resonant scanner toward each other. This makes the linear drive of the mirror plate on one axis possible. Furthermore, a resonant drive with a defined frequency on the fast horizontal axis can be combined with a variable quasi-static oscillation on the vertical axis. The components are manufactured in the Fraunhofer IPMS cleanroom in a bulk micromachining manufacturing process. All of the micro-mechanical components are manufactured as two-dimensional structures in a layer of monocrystalline silicon. The vertical comb electrodes are realized in an adhesive wafer bonding process with a second planar-structured silicon wafer. Mechanical solid state structures on the second wafer tilt or stagger the in-plane comb drive, the whole device is fixed by and subsequent wafer-bonding fusing. Given the small tolerances of micromachining processes, the structures on the two wafers are optimal aligned to each other. This component concept is extremely flexible and makes it possible to realize a broad spectrum of component characteristics.
The scanning head is the intermediate result of the European joint research project "TACO", carried out by Fraunhofer IPMS in cooperation with four other research facilities and two enterprises. Together, the partners are working on implementing the foveal principle – i.e. the rough scanning of objects appearing within the range of sight – in a 3D camera system to detect the objects looked for, and record said objects with a markedly higher resolution. The researchers plan to combine the LinScan scanning technology with a three-dimensional object survey based upon time of flight (TOF) as well as with software for ultra-fast object capture and to increase comprehension of the surroundings.
Visit the Fraunhofer Institute for Photonic Microsystems IPMS at www.ipms.fraunhofer.de
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