TOF De-aliasing via Periodic Frequency Cycling
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Solution Overview
Problem
Conventional time-of-flight (TOF) systems face challenges in disambiguating phase shift data due to inherent ambiguity between detected phase shift and distance measurements, leading to high power consumption and computational complexity, especially in portable depth imaging systems.
Innovation Solution
The system emits different frequencies of light over successive image frames, measuring phase shifts and computing distances for each frequency, then correlates the data across frames to determine a single distance, reducing power consumption and computational complexity while maintaining de-aliasing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple frequencies are emitted simultaneously for each frame to de-alias phase shift data, then de-aliasing accuracy is improved, but power consumption and computational complexity increase significantly
Solution Approach 1:
The patent applies periodic action by emitting different frequencies at different time intervals (frames) rather than simultaneously. The system cycles through multiple frequencies across successive frames, allowing de-aliasing to be achieved over time rather than requiring all frequencies to be active at once, thereby reducing instantaneous power consumption while maintaining measurement accuracy.
2Measurement precision
If multiple frequencies are emitted simultaneously for each frame to de-alias phase shift data, then de-aliasing accuracy is improved, but computational complexity increases significantly
Solution Approach 1:
The patent reduces computational complexity by processing frequencies periodically across frames rather than simultaneously. By correlating phase shift measurements taken at different frequencies across multiple frames, the system achieves de-aliasing with less computational burden compared to simultaneous multi-frequency processing, as each frame processes only one frequency.
Solution Approach 2:
The patent applies preliminary action by collecting phase shift data at different frequencies across multiple frames before performing the final correlation and de-aliasing computation. This staged approach allows the system to prepare measurement data in advance, reducing the complexity of the final computational step.
3Use of energy by moving object
If conventional TOF systems use single frequency emission, then power consumption is reduced, but phase shift ambiguity remains unresolved
Solution Approach 1:
The patent applies parameter changes by varying the frequency parameter across successive frames. By changing the emission frequency over time and correlating the phase shift measurements at different frequencies, the system resolves phase shift ambiguity while maintaining lower power consumption compared to simultaneous multi-frequency emission.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for the generation of depth maps with significantly reduced power consumption and computational resources compared to conventional methods, achieving accurate de-aliasing of phase shift data while maintaining the same level of accuracy as traditional systems.
Implementation Method 1
Gated three-dimensional (3-D) cameras, for example time-of-flight (TOF) cameras, provide distance measurements to objects in a scene by illuminating a scene and capturing reflected light from the illumination
Implementation Method 2
Conventional TOF systems ascertain depth distances (Z) to a target object by emitting modulated optical energy of a known frequency, f, and examining phase-shift in the optical signal reflected from the target object back to the TOF system
Data Source
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AI summary
A system and method are disclosed for determining a depth map using TOF with low power consumption. In order to disambiguate, or de-alias, the returned distance(s) for a given phase shift, the system may emit n different frequencies of light over n successive image frames. After n frames of data are collected, the distances may be correlated by a variety of methodologies to determine a single distance to the object as measured over n image frames. As one frequency may be emitted per image frame, the depth map may be developed while consuming low power.