LiDAR sensors in applications like autonomous driving, human-robot-collaboration, or logistics have to be robust, lowcost, and reliable. While several LiDAR architectures and methods are currently tested in the field, the improvement of individual system components, including photon detectors and laser sources, are part of ongoing scientific work.
The detector presented here is a CMOS integrated SPAD (single photon avalanche diodes) array device employing a new groundbreaking technology. Backside illuminated SPADs are fabricated and bonded wafer-to-wafer onto a smart ROIC (read-out IC), combining state-of-the-art circuitry and algorithms in a single device.
With 64x48 pixels the novel detector test vehicle paves the way for near-future LiDAR devices. The detector comprises a state-of-the-art time-to-digital converter (TDC) architecture for accurate time-of-flight (ToF) measurements with one TDC shared among 4 pixels. The TDC provides a time resolution of 312.5 ps and has a measurement range up to 192 m. Furthermore, the sensor supports switching of the acquisition modes between timing, counting, and time gating modes. The integrated background-light rejection algorithm, presented earlier in a previous device, allows about 66% higher maximum measurement ranges in environments with a high level of ambient light.
The large pixel pitch of 125 μm is actually limited by the ROIC manufactured in a 350 nm CMOS process. Thus, with smaller CMOS feature sizes for the ROIC, the pixel count can be scaled up drastically in future devices without changing the detection principle or the architecture of the SPAD detector array.