A Submillimeter Range Resolution Time-of-Flight Range Imager With Column-Wise Skew Calibration

This paper presents a time-of-flight (TOF) range imager with high-range resolution. The range imager employs a TOF measuring technique using an impulse photocurrent response and a high-speed lock-in pixel based on a drainingonly modulation. To address a skew problem in a 2-D array of the pixels, a column-wise gating-clock skew calibration was implemented. Each pixel has an in-pixel buffer and decoupling capacitor to reduce row-wise skew. A test-implemented imager has 132 × 120 effective pixels. The skew calibration circuit successfully reduce the skew from 173 to 8 psrms. The range resolution was achieved to be 0.25 mm with a 32-mm range, which corresponds to a 1.7-ps time resolution.