SPUMIC: Simultaneous phase unwrapping and multipath interference cancellation in time-of-flight cameras using spectral methods

Abstract

We propose a framework for simultaneous phase unwrapping and multipath interference cancellation (SPUMIC) in homodyne time-of-flight (ToF) cameras. Our multi-frequency acquisition framework is based on parametric modeling of the multipath interference phenomena. We use robust spectral estimation methods with low computational complexity to detect and estimate multipath parameters. Using simulations and analysis we demonstrate that our proposed solution is implementable in real-time on existing ToF cameras without requiring any hardware modifications.Index Terms-Time-of-flight range imaging, depth sensing, 3D camera, phase unwrapping, multipath cancellation, mixed, flying pixel, spectral estimation.

Defocus deblurring and superresolution for time-of-flight depth cameras

“…In contrast to these methods which aim to deblur the complex measurements, our approach directly estimates the latent amplitude and depth from the degraded measurements. This allows us to apply separate regularizations on the amplitude and depth, and also supports for the next generation ToF cameras with multiple modulation frequencies, phases and exposures [10,16].…”

“…Objects separated by the integer multiples of the full range are indistinguishable. The next generation of ToF cameras use multiple modulation frequencies and phases to reduce the ambiguity [10,16]. The multifrequency/phase data can also help resolve "flying pixels" (mixtures of foreground and background depth) at the object boundaries, and suppress artifacts due to global illumination [7].…”

Application of lidar techniques to time-of-flight range imaging

“…The application of lidar techniques to AMCW ToF cameras is possible because of the advances of the ToF imaging arrays, the maximum modulation frequency has increased significantly over the last ten years [4]. The closest previous work using ToF range cameras with multiple modulation frequencies is Kirmani [15], who take complex measurements at five frequencies and resolving multi-path interference with spectrum estimation and phase unwrapping the data. Sampling over five frequencies requires a minimum of 15 raw frames, and this is difficult to achieve when 30 fps of depth information is required.…”

“…The ideas in [18], while powerful and practical for analysis of light transport, are not suitable for real-time imaging. In contrast to both [15] and [18], the work herein does not use phase stepping, but instead relies only on multi-frequency data acquisition. In this paper we show that multi-frequency techniques are the equivalent of SFCW.…”

“…Freedman et al [14] expanded Godbaz's work to three modulation frequencies and used a compressed lookup table. Kirmani et al [15] measured five modulation frequencies and used spectrum estimation techniques to resolve the multi-path interference and perform phase unwrapping. Droeschel et al [16] also employed multi-frequency operation of AMCW to perform phase unwrapping.…”