Multi-Camera Intrinsic Calibration Under Thermal Distortion
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Solution Overview
Problem
Existing visual tracking systems in AR and VR devices face challenges in accurately calibrating camera intrinsic parameters due to thermal distortions caused by heat generated by the cameras and other components, which are not addressed by factory calibration methods.
Innovation Solution
A method for identifying and adjusting camera intrinsic parameters based on real-time temperature conditions by disabling one camera to reduce its temperature to factory calibration levels, using it for 6DOF tracking, and projecting features onto another camera to form a temperature-based distortion model for accurate calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If factory calibration is used to set camera intrinsic parameters, then the system is simple to manufacture and operate, but the calibration accuracy deteriorates under varying thermal conditions
Solution Approach 1:
The patent implements dynamic calibration by continuously monitoring camera temperature and adjusting intrinsic parameters in real-time based on thermal conditions. The system transitions from static factory calibration to dynamic adaptive calibration, where parameters are updated during operation to maintain accuracy across varying thermal environments.
Solution Approach 2:
The patent changes the operational parameters of the camera system by introducing temperature-dependent intrinsic parameters. Instead of using fixed calibration values, the system adjusts focal length, principal point, and distortion coefficients based on measured temperature, creating a mapping between thermal state and calibration parameters.
2Reliability
If real-time temperature-based calibration is implemented, then calibration accuracy under varying conditions is improved, but computing resources and system complexity increase
Solution Approach 1:
The patent performs preliminary calibration across a range of temperatures during manufacturing or initial setup, creating a pre-computed lookup table or calibration model. This allows the runtime system to simply query pre-calculated parameters based on current temperature, avoiding expensive real-time optimization computations while maintaining accuracy.
Solution Approach 2:
The patent replaces complex real-time computational calibration with a simplified query-based system that uses pre-computed temperature-parameter mappings. This substitution reduces the computational burden from solving optimization problems in real-time to simple table lookups or polynomial evaluations based on measured temperature.
3Measurement precision
If one camera is disabled for cooling to achieve factory calibration temperature, then calibration accuracy is improved, but productivity and data collection efficiency decrease
Solution Approach 1:
The patent implements periodic calibration cycles where cameras are temporarily disabled to cool down and achieve factory calibration temperature, then quickly re-enabled for normal operation. This periodic cooling-calibration-operation cycle allows the system to maintain accurate parameters without permanently reducing productivity, as calibration occurs in brief intervals rather than continuously.
Solution Approach 2:
The patent makes the camera system multi-functional by enabling it to operate in both calibration mode (with reduced cooling requirements) and normal tracking mode. The same hardware infrastructure serves dual purposes: capturing images for calibration during cooling periods and performing 6DOF tracking during operation, maximizing resource utilization.
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
Enhances the accuracy of visual-inertial tracking systems by providing real-time calibration, reducing the need for computing resources and improving pose estimation in varying user environments.
Implementation Method 1
disabling a first camera of the multi-camera visual tracking system while a second camera of the multi-camera visual tracking system is enabled... after detecting that the temperature of the first camera is within the threshold of the factory calibration temperature
Data Source
AI summary
A method for adjusting camera intrinsic parameters of a multi-camera visual tracking device is described. In one aspect, a method for calibrating the multi-camera visual tracking system includes disabling a first camera of the multi-camera visual tracking system while a second camera of the multi-camera visual tracking system is enabled, detecting a first set of features in a first image generated by the first camera after detecting that the temperature of the first camera is within the threshold of the factory calibration temperature of the first camera, and accessing and correcting intrinsic parameters of the second camera based on the projection of the first set of features in the second image and a second set of features in the second image.