Time Frequency Duality of Time-of-Flight Range Cameras for Resolving Multi-path Interference

Abstract

Time-of-Flight (ToF) range cameras measure the depth from the camera to the objects in the field of view. This is achieved by illuminating the scene with amplitude modulated light and measuring the phase shift in the modulation envelope between the out going and reflected light. ToF cameras suffer from measurement errors when multiple propagation paths exist from the light source to the pixel. Previous work has resolved this error by taking measurements at different modulation frequencies. Other previous work has used the properties of a binary sequence as the modulation waveform to resolve the multiple propagation paths. In this work the advantages of taking measurements with each method are investigated. There is an improved jitter performance and measurement linearity with using binary sequences, while decreased variance in the phase with a frequency sweep. We present a transform between sampling with a binary sequence and sampling with multiple frequencies and show that they are equivalent and a transform exists between them. The results of resolving multi-path interference are compared between each method and its transform.