An indirect time-of-flight measurement technique with impulse photocurrent response for sub-millimeter range resolved imaging.

This paper presents an indirect time-of-flight (TOF) measurement technique with an impulse photocurrent response of a lock-in pixel. By using a short-pulse laser, the generated photocurrent can be presumed to be an impulse response. This facilitates the utilization of the full high-speed performance of the photodetector and gives high range resolution. As a proof-of-concept, a test chip with a lock-in pixel based on draining-only modulation was implemented using 0.11 μm CMOS image-sensor technology. The test chip achieved a range resolution of 0.29 mm in a 50-mm measurable range, which corresponds to a time resolution of 1.9 ps and the successful acquisition of a 3-mm example step.