CW Time-of-Flight Camera Multi-Frequency Phase Sensing
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Solution Overview
Problem
Continuous wave (CW) ToF camera systems face challenges with high power consumption and potential inaccuracies due to object movement during light emission and readout, leading to blurred images and inefficient energy use.
Innovation Solution
A CW-ToF camera system operates in a low energy mode by modulating laser light with different frequencies for phase difference determination, reducing energy consumption and processing time while maintaining accuracy through techniques like lower optical power, shorter accumulation periods, fewer charge samples, and sub-sampling imaging pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laser light is emitted and image sensor readout is performed multiple times to obtain phase differences, then imaging accuracy is improved, but energy consumption increases
Solution Approach 1:
The patent applies partial action by performing multiple measurements only when necessary (e.g., when depth information is required or when objects are stationary), and using single measurements for other cases. This selective approach maintains imaging accuracy when needed while reducing energy consumption during normal operation.
Solution Approach 2:
The system dynamically adjusts its measurement strategy based on scene characteristics, object motion detection, and depth map quality requirements. When objects are detected to be moving or when depth accuracy is critical, the system performs multiple measurements; otherwise, it uses single measurements to conserve energy.
2Measurement precision
If multiple readout operations are performed on image sensor pixels, then phase difference measurement accuracy is improved, but operating time increases
Solution Approach 1:
The patent performs multiple readout operations selectively based on whether depth information is required and whether objects in the scene are stationary. When depth mapping is not needed or objects are moving, single readout operations are used, reducing operating time while maintaining sufficient accuracy for the application.
Solution Approach 2:
The system performs preliminary detection to determine if multiple measurements are necessary before executing the full measurement sequence. This preliminary assessment allows the system to avoid unnecessary multiple readout operations, thereby reducing operating time while maintaining accuracy when truly needed.
3Measurement precision
If laser emission and sensor readout time is extended to improve measurement accuracy, then phase difference precision is improved, but object movement during measurement causes blurring
Solution Approach 1:
The patent performs multiple measurements only when objects are detected to be stationary or when depth information is critically required. When objects are moving, the system uses single measurements to capture the scene before motion causes blurring, accepting reduced precision in exchange for maintaining image quality.
Solution Approach 2:
The system uses feedback from motion detection and depth map quality assessment to dynamically adjust the measurement strategy. When motion is detected or when single measurements provide sufficient quality, the system reduces to single measurements, preventing motion blur while maintaining adequate precision.
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
The system achieves lower energy consumption and faster operation without significant reduction in imaging accuracy, reducing motion blur and increasing frame rate by optimizing energy use and processing speed.
Implementation Method 1
an imaging sensor comprising a plurality of imaging pixels for accumulating charge based on incident light comprising reflected laser light
Data Source
AI summary
The present disclosure relates to a lower energy/faster time of flight camera system configured to measure distance to an object. The system is configured to emit laser light modulated with a first frequency and image light reflected by an object in order to determine a first phase difference between the emitted and reflected light. It then emits laser light modulated with a second frequency and images light reflected by the object to determine a second phase difference between the emitted and reflected light. The distance to the object is determined using the first and second phase differences. The system operates at lower energy for obtaining the first phase difference compared with the operation to obtain the second phase difference. This results in lower overall energy consumption, and potentially also faster overall operation, compared with previous continuous wave time of flight systems, without any significant reduction in accuracy of imaging.