Scan-less 3D optical sensing/Lidar scheme enabled by wavelength division demultiplexing and position-to-angle conversion of a lens.

Abstract

We propose a novel scheme for 3D sensing or Lidar without the need for beam scan or 2D photo-imaging. The scheme is enabled by the combination of a lens' position-to-angle conversion and the wavelength division multiplexing/demultiplexing (WDM) commonly used in optical fiber communication systems. However, unlike in a WDM system where different wavelengths carry different data channels, here lights of different wavelengths are demultiplexed into different waveguides or fibers with their exiting ends placed in the focal plane of the lens, which converts the exiting lights into beams of different angles to form a 1D or 2D beam array according to the relative position of the fiber ends with respect to the optical axis of the lens for illuminating the targets and finally sensing the light reflected from different directions. The returned signals are then demultiplexed into different photodetectors to determine the distances of the reflections in different directions. We show that the scheme has the potential to be implemented in photonics integrated circuit (PIC) for low cost production. We successfully demonstrate the scheme with the off-the-shelf discrete fiber optic components using 4 WDM channels and time-of-flight (ToF) technique for distance measurement, although hundreds wavelength channels from a photonic integrated microcomb may be used in practice. Finally, we demonstrate that the angular resolution of the beam array of different wavelengths can be improved by dithering the fiber array or the lens. We believe this new scheme provides an attractive alternative to the MEMS and optical phased array based beam scanning and can be explored further to enable low cost and high speed 3D sensing, particularly Lidar systems.