Time-of-Flight Camera Relative Motion Detection via Phase Correlation
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Solution Overview
Problem
Time-of-Flight (ToF) sensors are limited in range and image rate, which restricts their capability to sense motion of an object relative to the sensor effectively.
Innovation Solution
A method and apparatus where the object emits a modulated light signal, allowing the ToF camera to receive multiple sets of raw images based on correlations between the modulated reference signal and measurement signals, with phase differences determined and synchronized to calculate relative motion, compensating for synchronization errors to improve motion detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional ToF sensors are used to measure distances, then distance measurement capability is provided, but the sensing range and image rate are limited, restricting motion detection capability
Solution Approach 1:
The patent changes the operational parameters by using multiple modulation frequencies instead of a single frequency. This allows the system to achieve both high image rates for motion detection and maintain reliable distance measurement capability across different ranges, resolving the contradiction between productivity and reliability in motion sensing.
Solution Approach 2:
The patent segments the distance measurement process by dividing the scene into different depth ranges and using different modulation frequencies for different ranges. This segmentation allows simultaneous optimization for both near-field high-speed motion detection and far-field distance measurement, addressing the limitation of conventional single-frequency ToF sensors.
2Ease of operation
If the ToF camera emits light to sense objects, then active illumination enables sensing, but the system complexity and energy consumption increase
Solution Approach 1:
The patent applies self-service by having the object itself emit the modulated light signal rather than requiring the ToF camera to actively illuminate the scene. The object's emitted light is then detected and correlated by the camera, enabling passive sensing that reduces the energy burden on the camera system while maintaining sensing capability.
Solution Approach 2:
The patent inverts the conventional ToF approach by reversing the roles: instead of the camera emitting light and detecting reflections, the object emits light and the camera detects and correlates this emitted light with reference signals. This inversion reduces the camera's energy consumption while preserving distance and motion measurement capabilities.
3Device complexity
If synchronization is not performed, then system complexity is reduced, but measurement accuracy deteriorates due to synchronization errors
Solution Approach 1:
The patent implements feedback by continuously monitoring the phase differences between emitted and received light signals and using this information to adjust and maintain accurate distance measurements. The correlation process provides feedback that compensates for timing variations, achieving high measurement precision without requiring complex active synchronization mechanisms.
Solution Approach 2:
The patent applies preliminary action by pre-calculating and storing correlation data for multiple modulation frequencies and phase shifts. This pre-processing allows the system to quickly determine accurate phase differences without requiring complex real-time synchronization, reducing device complexity while maintaining measurement 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
Enables improved measurement of relative motion between the ToF camera and object with increased sample rates and wider distance ranges, enhancing the capability to detect relative distance changes and motion speed without the need for the camera to emit light, thus overcoming the limitations of conventional ToF sensing.
Implementation Method 1
Time-of-Flight (ToF) sensors measure distances to electronic devices
Implementation Method 2
determining for each set of raw images a value indicating a respective phase difference between the modulated light signal and the modulated reference signal
Data Source
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AI summary
A method for determining relative motion between a time-of-flight camera and an object in a scene sensed by the time-of-flight camera is provided. The object emits a modulated light signal. The method includes receiving at least two sets of raw images of the scene from the time-of-flight camera. The at least two sets of raw images each comprise at least one raw image. The raw images are based on correlations of a modulated reference signal and measurement signals of the time-of-flight camera. The measurement signals are based on the modulated light signal emitted by the object. Further, the method includes determining for each set of raw images a value indicating a respective phase difference between the modulated light signal and the modulated reference signal based on the respective set of raw images. The method additionally includes determining information about relative motion between the time-of-flight camera and the object based on the values indicating the phase differences. Further, the method includes outputting the information about relative motion between the time-of-flight camera and the object.