44 scanning technology taken from laser printers. This can detect a 30 cm falling object at a distance of 100 m. In Lidar, a MEMS mirror or motor is required to irradiate laser light over a wide, high-density area. However, MEMS mirrors typically have lower resolution and motors tend to wear out quickly. One company’s new integrated sensor provides higher resolution than motorbased systems and greater durability than conventional MEMS mirrors. A proprietary MEMS mirror, developed with that supplier’s advanced manufacturing and ceramic package technologies, and high-resolution laserscanning technology, supports highprecision sensing for various industries, including autonomous vehicles, ships, heavy machinery, and more. Solid state Lidar An all-solid-state Lidar eliminates moving parts and replaces mechanical scanning with electrical scanning. Among the commercially viable system designs are a VCSEL source with defocus lenses for flash illumination and 1D/2D addressable VCSEL with defocus lenses. Additional options include VCSEL/EEL with a metasurface and a FMCW EEL with optical array. Medium- to long-distance Lidars use an array of addressable VCSEL lasers, which can be scanned to illuminate the area in front of a vehicle. A 2D VCSEL array matrix allows individual control of both anodes and cathodes of the VCSEL laser diodes, providing more flexibility in the illumination strategies. The metal electrodes add complexity to the fabrication, however, and it faces slightly more challenges compared with the 1D approach. Higher peak power enables greater signal-to-noise ratios and longer detection ranges for Lidar. Having more junctions ensures a higher external quantum efficiency, directly proportional to the junction count. This results in a higher power density, while driving current, and a greater power conversion efficiency for the same optical power. Existing VCSEL-based Lidars typically have five to six junctions, doubling every 18 months. Researchers have experimentally demonstrated small-divergence AR-VCSELs up to 14 junctions and, theoretically, there is no upper limit for the number of junctions. However, in practical terms, incorporating more junctions may present challenges in terms of thick epitaxial growth, high aspect ratio trench/mesa etching and coating in fabrication, and reliability concerns at higher power density and material stress. Reliability To ensure the reliable operation of Lidar throughout a vehicle’s lifetime, the lasers must pass the automobile standard reliability test, AEC-Q102. This testing includes a high-temperature operating lifetime (HTOL) of 1000h, HTOL under 85C and an 85% humidity environment of 1000h, a lowtemperature operating lifetime of 500h, powered/unpowered temperature cycling, a harmful gas test, dew test and an electrostatic discharge (ESD) test. While AEC-Q102 is the basic reliability standard for VCSELs used in automotive Lidar, every manufacturer sets its own standard, which is normally higher and includes rigorous requirements for the failure in time (FIT) rate – the number of failures expected in one billion device hours of operation. AR-VCSEL array chips can survive the 6000h HTOL test, well above the AEC-Q102 requirement and represent over 300 years of use in the field. In addition to the long-term ageing study, tens of thousands of AR-VCSEL array chips have been subjected to the FIT study. Although the higher power-density requirement in future Lidar systems to provide higher range sensing may add stress to the lifetime of AR-VCSEL, the tests show sufficient endurability. April/May 2025 | Uncrewed Systems Technology Focus | Lidar Images detected by a camera-Lidar fusion sensor (Image courtesy of Kyocera) Fusion of the camera and Lidar sensor provides parallax-free, real-time data integration, ensuring efficient and accurate results
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