Time-of-flight camera power reduction via selective modulation frequency
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Solution Overview
Problem
Time-of-flight (ToF) cameras face high power consumption due to the need for multiple IR image captures at various modulation frequencies to disambiguate phase differences greater than 2π, leading to phase wrapping issues and increased energy usage.
Innovation Solution
Implementing a method where key-frame depth images are generated using multiple modulation frequencies, and P-frame depth images are generated using a single modulation frequency, reducing the number of IR images captured and thus lowering power consumption by activating electronic components only when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple modulation frequencies are used to disambiguate phase differences, then depth measurement accuracy is improved, but power consumption increases
Solution Approach 1:
The patent segments the frame buffer into multiple planes (first plane for first modulation frequency, second plane for second modulation frequency). This allows selective processing and rendering from different frequency data, enabling the system to use multi-frequency depth information only when needed for disambiguation, rather than continuously capturing at all frequencies, thus reducing overall power consumption while maintaining measurement accuracy when required
Solution Approach 2:
The system implements periodic capture at multiple modulation frequencies rather than continuous multi-frequency capture. By alternating between single-frequency and multi-frequency capture modes based on rendering needs, the patent reduces the total number of high-power multi-frequency capture operations while still achieving accurate depth measurement when phase disambiguation is necessary
2Reliability
If multiple IR images are captured at various modulation frequencies, then phase wrapping issues are resolved, but the number of image captures increases
Solution Approach 1:
The patent performs preliminary rendering using depth information from a single modulation frequency to determine whether phase disambiguation is actually needed. Only when the preliminary render indicates potential phase wrapping issues does the system proceed to capture and process additional images at multiple frequencies. This preliminary assessment action reduces the total number of image captures by avoiding unnecessary multi-frequency acquisitions in scenes without phase wrapping problems
Solution Approach 2:
The frame buffer with its multiple planes acts as an intermediary structure that stores depth information from different modulation frequencies. This intermediary allows the system to capture images at multiple frequencies, store them efficiently in separate planes, and then selectively combine or use only the necessary frequency data for phase disambiguation, reducing the operational overhead compared to processing all captured images at all frequencies
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 reduces power consumption in ToF cameras by generating P-frame depth images with less electrical power compared to traditional multi-frequency methods, while maintaining accurate depth measurements, particularly beneficial for battery-powered devices.
Implementation Method 1
a ToF illuminator configured to emit active IR light
Implementation Method 2
the ToF illuminator is repeatedly activated to illuminate a scene with active IR light, wherein the ToF illuminator modulates the active IR light in a plurality of different modulation frequencies
Implementation Method 3
A time-of-flight (ToF) camera may determine a depth of a subject relative to the ToF camera based on the known speed of light and a measured time of flight of light between the ToF camera and the subject
Data Source
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AI summary
A time-of-flight (ToF) camera is configured to operate in a manner that reduces power consumption of the ToF camera. For a key frame, a key-frame depth image is generated based on a plurality of sets of key-frame IR images. Each set of key-frame IR images is acquired using a different modulation frequency of active IR light. For a P-frame after the key frame, a P-frame depth image is generated based on a set of P-frame IR images acquired using a single modulation frequency of active IR light.