Time-of-Flight Depth Imaging With Temperature-Based Phasor Correction
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Solution Overview
Problem
Time-of-flight depth sensing systems experience errors in depth measurements due to temperature sensitivity of light sources and image sensors, leading to inaccuracies in phase and amplitude measurements, particularly at high-powered laser operations.
Innovation Solution
Implement a linear inverse approach to determine complex phasors for each sample acquired at each light source modulation frequency, using temperature calibration models to correct for temperature dependencies of both the light source and image sensor, applying spatial corrections to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high-powered laser operations are used to improve illumination intensity, then lighting performance is improved, but temperature increases causing measurement precision to deteriorate
Solution Approach 1:
The system continuously monitors temperature through temperature sensors and feeds this information back to the processor, which then adjusts calibration parameters and phase offset values to compensate for temperature-induced measurement drift, maintaining measurement precision despite high-powered laser operation
Solution Approach 2:
The system dynamically changes calibration parameters and phase offset values based on temperature measurements. By adjusting these parameters as temperature varies during high-powered laser operation, the system maintains accurate depth measurements while using high illumination power
2Measurement precision
If temperature compensation is implemented to maintain measurement precision, then depth measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The system performs preliminary calibration at multiple temperature points during manufacturing, storing calibration data in lookup tables. During operation, the system simply retrieves pre-computed calibration values based on current temperature, avoiding the need for complex real-time compensation calculations
Solution Approach 2:
The patent replaces complex analog temperature compensation mechanisms with digital signal processing techniques. By using digital lookup tables and processor-based calibration adjustments, the system achieves precise temperature compensation with minimal additional hardware complexity
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
Achieves millimeter-level accuracy across a wide temperature range by mitigating temperature-induced errors, ensuring precise depth sensing despite variations in electro-optical properties.
Implementation Method 1
a periodically modulated laser beam is emitted toward a target object, reflected light is received at an image sensor, and, for each pixel of the image sensor, the phase of the received light is compared with that of the emitted light
Implementation Method 2
one or more temperature sensors configured to sense a temperature of the light source and/or image sensor
Data Source
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AI summary
One example provides a time-of-flight depth imaging system configured to modulate light emitted from a light source to illuminate an environment with modulated light, and for each of one or more modulation frequencies, integrate an image at each phase step of a plurality of phase steps, and sense a temperature of the light source and/or image sensor via one or more temperature sensors to acquire a measured temperature. The instructions are further executable to,, and for each pixel of one or more pixels of the image sensor, determine a complex phasor based upon the measured temperature using a linear inverse function for each modulation frequency, determine a phase shift between the light emitted from the light source and light from the light source reflected back by the environment based on the complex phasor, and output a depth value for the pixel based upon the phase shift.