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

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.

[1]  Ramesh Raskar,et al.  Coded time of flight cameras , 2013, ACM Trans. Graph..

[2]  H. Aanaes,et al.  Environmental Effects on Measurement Uncertainties of Time-of-Flight Cameras , 2007, 2007 International Symposium on Signals, Circuits and Systems.

[3]  Guang Gong,et al.  Signal Design for Good Correlation: For Wireless Communication, Cryptography, and Radar , 2005 .

[4]  Michael J. Cree,et al.  A strategy for the correction of effects of jitter in AMCW lidar images , 2013, 2013 28th International Conference on Image and Vision Computing New Zealand (IVCNZ 2013).

[5]  Adrian Peter Paul Jongenelen,et al.  Development of a Compact,  Configurable, Real-Time Range  Imaging System , 2011 .

[6]  Michael J. Cree,et al.  Closed-form inverses for the mixed pixel/multipath interference problem in AMCW lidar , 2012, Electronic Imaging.

[7]  Ayush Bhandari,et al.  Sampling and Reconstruction of Sparse Signals in Fractional Fourier Domain , 2010, IEEE Signal Processing Letters.

[8]  Robert Lange,et al.  3D time-of-flight distance measurement with custom solid-state image sensors in CMOS/CCD-technology , 2006 .

[9]  M. Cree,et al.  Mixed pixel return separation for a full-field ranger , 2008, 2008 23rd International Conference Image and Vision Computing New Zealand.

[10]  Philip A. Chou,et al.  SPUMIC: Simultaneous phase unwrapping and multipath interference cancellation in time-of-flight cameras using spectral methods , 2013, 2013 IEEE International Conference on Multimedia and Expo (ICME).

[11]  Mirko Schmidt,et al.  SRA: Fast Removal of General Multipath for ToF Sensors , 2014, ECCV.

[12]  Timo Kahlmann,et al.  Range imaging metrology: Investigation, calibration and development , 2008 .

[13]  Ramesh Raskar,et al.  Resolving Multi-path Interference in Time-of-Flight Imaging via Modulation Frequency Diversity and Sparse Regularization , 2014, Optics letters.