# A Six-Tap 720 × 488-Pixel Short-Pulse Indirect Time-of-Flight Image Sensor for 100 m Outdoor Measurements

## TL;DR

A new image sensor enables long-range distance measurements up to 100 meters with high accuracy and resistance to ambient light.

## Contribution

A six-tap, high-resolution SP-iToF image sensor is introduced for long-range, high-accuracy depth measurements under bright conditions.

## Key findings

- The sensor achieves 100 m outdoor measurements with depth noise below 1%.
- It uses a six-tap pixel design with 90% demodulation contrast for 20 ns light pulses.
- High-speed ADCs and efficient exposure allocation enable a 10 fps depth-image frame rate.

## Abstract

Long-range, high-resolution distance measurement with high ambient-light tolerance has been achieved using a 720 × 488-resolution short-pulse indirect time-of-flight (SP-iToF) image sensor featuring six-tap, one-drain pixels fabricated by a front-side illumination (FSI) process. The sensor performs 30-phase demodulation through six-tap pixels in each subframe, combined with five range-shifted subframe (SF) readouts. The six-tap demodulation pixel, designed with a lateral drift-field pinned photodiode, demonstrates over 90% demodulation contrast for a 20 ns light-pulse width. High-speed column-parallel 12-bit cyclic ADCs enable all six-tap subframe signals to be read within 4.38 ms. This high-speed subframe readout, together with efficient exposure-time allocation across the five subframes, enables a depth-image frame rate of 10 fps. The multi-phase demodulation in SP-iToF measurements, operating with an extremely small duty ratio of 0.2%, effectively suppresses ambient-light charge accumulation and the associated shot noise in the pixel. As a result, distance measurements up to 100 m under 100 klux illumination are achieved, with depth noise maintained below 1%.