A 400 × 112 CMOS LiDAR Sensor with Reconfigurable-Resolution Histogramming Time-to-Digital Converters and Sub-cm Depth Refining Filter

For long-range scan light detection and ranging (LiDAR), two parameters are crucial: spatial and time resolution. Because target objects located at far distances provide only a few points on a low resolution sensor, higher spatial resolution is essential. For mechanical LiDAR, which achieves high resolution through mechanical laser scanning, increased scanning leads to lower frame rate. Moreover, a large form factor and low manufacturability can be problematic [1]. A solid-state LiDAR with row-addressable laser scanning overcame the shortcomings of mechanical LiDAR. However, achieving high resolution remains challenging due to the dense column-parallel histogramming time-to-digital converters (hTDCs) in small pitch. Even though a QVGA sensor has been reported, only the pixels, not hTDC, are reconfigured to achieve high resolution, hTDCs that can be accessed per laser emission is limited to half of the horizontal image resolution [2]. Therefore, the resolution of state-of-the-art sensors is below $200 \times 100$ [3], [4]. The time resolution is also crucial for identifying objects in a three-dimensional way. Unfortunately, owing to the limited capacity of the histogram memory, low time resolution over $1-\mathrm{ns}(15-\mathrm{cm})$ was allowed.