Denso launches technology to reduce the cost of laser scanners

Denso has developed a technology for integrally forming an array of optical elements such as micro prisms and lenses on a silicon substrate, and published it on "MEMS2007" (published serial number: M9). This technology can use a DRIE (Deep Reactive Ion Etching) process to form an array of tiny optical elements of hundreds of μm square. Although the company did not disclose the specific use of the technology, it is estimated to be used for obstacle detection in the automotive field because of its ability to control the direction of the laser.

This technology enables the use of existing processes to oxidize silicon on the substrate to glass (silica) and glass as an optical component. Since the volume of silicon is expanded to 2.22 times after conversion into silicon dioxide, it is necessary to use a DRIE process to engrave trenches on the silicon element. In the thermal oxidation process, the entire portion is gradually oxidized into glass from the trench. At this time, the grooves are filled by the expansion, and optical elements such as prisms and lenses can be formed. The original position of the groove does not cause adverse optical effects such as light refraction. In order to reduce the roughness of the surface of the optical element, high temperature hydrogen annealing at 1150 ° C is required before the thermal oxidation process.

This technology enables the formation of an integrated prism array and lens array side by side on a silicon substrate, and the laser source array near the lens array is mounted in a later process. In order to eliminate the need to calibrate the optical axis of the laser source during installation, the positioning device required to properly mount the laser source is formed on the silicon substrate in advance. In the future, it is also possible to transplant a laser light source manufactured by another process such as a GaN substrate to a silicon substrate.

This time, by controlling the phase of the laser array, the phase of the laser can be controlled like a phased array antenna, and the illumination direction can be scanned at a certain angle range. Combined with a laser sensor, it can be applied to the detection of obstacles. At present, in the automotive field, the use of laser and millimeter wave obstacle detection sensors has reached a practical level, but most of them are large in size and expensive. If this technology reaches a practical level, laser scanning components are expected to achieve significant miniaturization and cost reduction. When equipped with a car, it can be placed in multiple parts of the body bumper.