Phase disambiguation using spatio-temporally modulated illumination in depth sensing

Takahiro Kushida,Kenichiro Tanaka,Takahito Aoto,Yasuhiro Mukaigawa,Takuya Funatomi

doi:10.1186/s41074-020-00063-x

Abstract

Phase ambiguity is a major problem in the depth measurement in either time-of-flight or phase shifting. Resolving the ambiguity using a low frequency pattern sacrifices the depth resolution, and using multiple frequencies requires a number of observations. In this paper, we propose a phase disambiguation method that combines temporal and spatial modulation so that the high depth resolution is preserved while the number of observation is kept. A key observation is that the phase ambiguities of temporal and spatial domains appear differently with respect to the depth. Using this difference, the phase can disambiguate for a wider range of interest. We develop a prototype to show the effectiveness of our method through real-world experiments.

Highlights

Depth measurement is widely used in applications such as augmented reality, factory automation, robotics, and autonomous driving
The phase ambiguity still exists in the frequency of the greatest common divisor, which requires several measurements to obtain a wider range of interest
The depths were obtained by an ordinary ToF with a single low frequency, phase shifting with single high frequency, and our method for the comparison

Summary

Introduction

Depth measurement is widely used in applications such as augmented reality, factory automation, robotics, and autonomous driving. A key observation of this paper is that the phase ambiguities of the time-of-flight (ToF) and the phase shifting appear differently on the depth domain. The spatial phase is defined as the disparity domain; the depth candidates appear at gradually increasing intervals Based on this difference, the phase ambiguity can be resolved by combining temporal and spatial modulation. We combine these techniques to realize both better resolution and wider range of interest Another problem regarding the ToF is multi-path interference due to indirect light transport. Our method leverages the asymmetric relations of spatial and temporal wrapping to solve the ambiguity of the phase

Depth measurement techniques using modulated illumination

Phase recovery and depth estimation

Result

Findings

Conclusion