Miniaturization of a wide-angle 3D FMCW flash LIDAR

In the field of three-dimensional (3D) sensing, the Frequency Modulated Continuous Wave (FMCW) Light detection and ranging (LIDAR) has natural capabilities such as immunity to ambient light and the measurement of axial speed in addition to depth. Today, most implementations rely on scanning solutions. These later systems are either mechanically built, or based on optical phased arrays (OPAs). The scene is illuminated point by point, and the interference with the reference beam is then detected by a single photo-detector. However, the development of a beam-steering component able to scan the scene in two dimensions at fast rates with low power consumption remains a challenge. An alternative solution without any OPA is the flash FMCW LIDAR where a diverging beam illuminates the whole scene and the detection is carried out in parallel in every pixel of an image sensor. Despite common belief, both solutions have the same depth range in principle, given the same resolution and frame rate of the depth image. In this work, we present our development of a flash FMCW LIDAR system operational in the near-infrared domain. We have designed our system for the detection of a wide field of view (FOV = 52°), and assembled it with micro-optical millimeter-sized optical components in an attempt for miniaturization. We show depth images obtained with our setup. We also measure the depth resolution of the system and its angular performance by determining the heterodyne efficiency as a function of the angle in the field of view. It turns out that the present performances of our LIDAR are limited by the camera frame rate, and the misalignment of reference and scene beams incident on the sensor. We finally put forward some ideas to overcome these limitations in the near future.