Analysis of Errors in ToF Range Imaging With Dual-Frequency Modulation

TLDR

Range imaging uses amplitude‑modulated light and a gain‑modulated sensor to capture distance and intensity for every pixel, with precision partly determined by modulation frequency and typically trading off against maximum unambiguous range. The paper proposes an efficient method that combines two distance measurements at different modulation frequencies, using signal amplitude to enhance precision. The method merges dual‑frequency distance data and incorporates signal amplitude, with its noise behavior analyzed to estimate error rates. Two‑frequency measurements extend unambiguous range without sacrificing precision, and simulated results agree with data from a PMD19k sensor.

Abstract

Range imaging is a technology that utilizes an amplitude-modulated light source and gain-modulated image sensor to simultaneously produce distance and intensity data for all pixels of the sensor. The precision of such a system is, in part, dependent on the modulation frequency. There is typically a tradeoff between precision and maximum unambiguous range. Research has shown that, by taking two measurements at different modulation frequencies, the unambiguous range can be extended without compromising distance precision. In this paper, we present an efficient method for combining two distance measurements obtained using different modulation frequencies. The behavior of the method in the presence of noise has been investigated to determine the expected error rate. In addition, we make use of the signal amplitude to improve the precision of the combined distance measurement. Simulated results compare well to actual data obtained using a system based on the PMD19k range image sensor.