A high background light subtraction circuit for long range time-of-flight cameras

In this paper, a background light subtraction circuit is presented for a long range time-of-flight camera in outdoor applications. A low (de)modulation frequency is used for long range estimation, which saturates the photodiode due to integration of high-intensity background light. Therefore, long range cameras are generally limited to indoor applications. In this work, a circuit is proposed to subtract up to 120 klx BGL for 1.07-9.65 m distance. A (de)modulation frequency of 2.33 MHz with 33 % duty-cycle is used. The measurement results show a range resolution of 1.49 cm and 65 cm for 1.07 m and 9.65 m distance, respectively at 120 klx background light. The circuit is fabricated and characterized in UMC 180 nm technology.