A large-scale coherent 4D imaging sensor.

Abstract

Detailed and accurate 3D mapping of dynamic environments is essential for machines to interface with their surroundings^1-3 and for human-machine interaction^4,5. Although considerable effort has been made to create the equivalent of the complementary metal-oxide-semiconductor (CMOS) image sensor for the 3D world, scalable, high-performance, reliable solutions have proven elusive^6-11. Focal plane array (FPA) sensors using frequency-modulated continuous-wave (FMCW) light detection and ranging (LiDAR) have shown potential to meet all of these requirements and also provide direct measurement of radial velocity as a fourth dimension. Previous demonstrations^12,13, although promising, have not achieved the simultaneous scale and performance required by commercial applications. Here we present a large-scale, coherent LiDAR FPA enabled by comprehensive chip-scale optoelectronic integration. A 4D imaging camera is built around the FPA and used to acquire point clouds. At the core is a 352 × 176-pixel 2D FMCW LiDAR FPA comprising more than 0.6 million photonic components, all integrated on-chip together with their associated electronics. This represents a five times increase in pixel count with respect to previous demonstrations¹². The pixel architecture combines the outbound and inbound optical paths within the pixel in a monostatic configuration, together with coherent detectors and electronics. Frequency-modulated light is directed sequentially to groups of pixels by in-plane thermo-optic switches with integrated electronics for driving and calibration. An integrated serial digital interface controls both optical switching and readout synchronously. Point clouds of objects ranging from 4 to 65 m with per-pixel integration time compatible with frame rates from 3 to 15 frames per second (fps) are shown. This result demonstrates the capabilities of FMCW LiDAR FPA sensors as enablers of ubiquitous, low-cost, compact coherent 4D imaging cameras.