A Parallel-Phase Demodulation-Based Distance-Measurement Method Using Dual-Frequency Modulation

In-Gyu Jang,Sung-Hyun Lee,Yong-Hwa Park

doi:10.3390/app10010293

In-Gyu Jang, Sung-Hyun Lee + Show 1 more

Open Access

https://doi.org/10.3390/app10010293

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Abstract

Time-of-flight (ToF) measurement technology based on the amplitude-modulated continuous-wave (AMCW) model has emerged as a state-of-the-art distance-measurement method for various engineering applications. However, many of the ToF cameras employing the AMCW process phase demodulation sequentially, which requires time latency for a single distance measurement. This can result in significant distance errors, especially in non-static environments (e.g., robots and vehicles) such as those containing objects moving relatively to the sensors. To reduce the measurement time required for a distance measurement, this paper proposes a novel, parallel-phase demodulation method. The proposed method processes phase demodulation of signal in parallel rather than sequentially. Based on the parallel phase demodulation, 2π ambiguity problem is also solved in this work by adopting dual frequency modulation to increase the maximum range while maintaining the accuracy. The performance of proposed method was verified through distance measurements under various conditions. The improved distance measurement accuracy was demonstrated throughout an extended measurement range (1–10 m).

Highlights

Such 3D spatial information can be utilized in various types of engineering applications, such as unmanned vehicles, robots, human-recognition systems, medical applications, and even personal IT devices [1,2,3,4,5,6,7]
In the field of machine vision, 3D depth maps are widely used for many purposes, including human motion capturing [5,6] and object recognition [7]
The ToF measurement method has been widely adopted as an alternative for 3D depth sensing due to its compactness and low calculation loads [12,13,14,15,16]

Summary

Introduction

Such 3D spatial information can be utilized in various types of engineering applications, such as unmanned vehicles, robots, human-recognition systems, medical applications, and even personal IT devices [1,2,3,4,5,6,7]. There are several ways to obtain a 3D depth map, such as stereoscopy [8,9], the structured light method [10,11], and the Time-of-flight (ToF) measurement method [12,13,14,15,16]. The stereoscopy and structured light methods require many cameras and incur excessive computational loads [13]. These methods can achieve high depth resolutions only when a relatively large triangulation base is obtained, meaning that the systems are often bulky [13]. The traveling time, i.e., the ToF, is converted into the distance

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Results

Conclusion