TOF Sensor Mode Switching for Low-Power 3D Hand Tracking
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Solution Overview
Problem
Wearable systems using time-of-flight (TOF) sensors for hand tracking in augmented reality (AR), virtual reality (VR), or mixed reality (MR) environments face significant power consumption issues, making them prohibitive for efficient operation.
Innovation Solution
A power-efficient method for TOF sensors involving a low power mode that computes depth frames and amplitude frames, switching to a high accuracy mode when activation conditions are met, such as user interaction, to conserve power while maintaining accurate hand tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If TOF sensor operates in high accuracy mode continuously, then hand tracking precision is improved, but power consumption increases significantly
Solution Approach 1:
The system dynamically switches between low power mode and high accuracy mode based on detected hand presence and interaction conditions. The TOF sensor operates in low power mode during normal operation and transitions to high accuracy mode only when hand interaction is detected, making the system adaptable to real-time requirements while optimizing power consumption.
Solution Approach 2:
The system performs periodic hand presence detection using low power mode sequences, which include depth frames and amplitude frames. This periodic checking allows the system to maintain awareness of hand presence with minimal power consumption while enabling timely transitions to high accuracy mode when needed.
2Use of energy by moving object
If TOF sensor operates in low power mode, then power consumption is reduced, but hand tracking accuracy decreases
Solution Approach 1:
The system performs preliminary detection using low power mode sequences that include both depth frames and amplitude frames. These preliminary actions detect hand presence and prepare the system for potential high accuracy mode activation, ensuring that full accuracy is available when hand interaction is anticipated.
Solution Approach 2:
The system uses feedback from depth frame and amplitude frame analysis to determine whether hand presence conditions are met. This feedback mechanism guides the decision to switch between operating modes, ensuring that hand tracking accuracy is maintained when hands are present while conserving power when they are not.
3Measurement precision
If TOF sensor performs frequent depth frames, then hand tracking accuracy is improved, but power consumption increases
Solution Approach 1:
The system segments the frame acquisition process into two distinct types: depth frames for accurate 3D hand tracking and amplitude frames for hand presence detection. By segmenting these functions and performing them in different modes, the system reduces overall power consumption while maintaining hand tracking accuracy when needed.
Solution Approach 2:
The system changes operational parameters by switching between low power mode and high accuracy mode based on hand presence detection. This parameter change allows the system to adjust the frequency and type of frames acquired, optimizing the balance between hand tracking accuracy and power consumption dynamically.
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 by alternating between low power and high accuracy modes, ensuring efficient hand tracking with reduced energy usage without compromising accuracy.
Implementation Method 1
A time-of-flight (TOF) camera (or sensor) is a range imaging camera system that resolves distance based on the speed of light, measuring the time-of-flight of a light signal between the camera and the subject for each point of the image
Implementation Method 2
The illumination is switched on for a short time, the resulting light pulse illuminates the scene and is reflected by the objects in the field of view. The camera lens gathers the reflected light and images it onto the sensor or focal plane array
Data Source
AI summary
Techniques are disclosed for operating a time-of-flight (TOF) sensor. The TOF may be operated in a low power mode by repeatedly performing a low power mode sequence, which may include performing a depth frame by emitting light pulses, detecting reflected light pulses, and computing a depth map based on the detected reflected light pulses. Performing the low power mode sequence may also include performing an amplitude frame at least one time by emitting a light pulse, detecting a reflected light pulse, and computing an amplitude map based on the detected reflected light pulse. In response to determining that an activation condition is satisfied, the TOF may be switched to operate in a high accuracy mode by repeatedly performing a high accuracy mode sequence, which may include performing the depth frame multiple times.