Stereo Camera Calibration Using Trifocal Feature Tracking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional stereo camera systems for vehicles require additional hardware and software for calibration, necessitating laboratory settings and specialized targets, limiting real-time or near real-time calibration capabilities.
Innovation Solution
A method for calibrating image sensors using images captured at different time instances, tracking feature points, and applying trifocal constraints to determine calibration parameters without the need for specialized targets or time synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional systems use calibration targets and fixed brackets for stereo camera calibration, then manufacturing precision and reliability are improved, but device complexity and ease of operation deteriorate due to requiring specialized hardware and laboratory environments
Solution Approach 1:
The patent extracts and removes the calibration target from the calibration process. Instead of requiring external calibration targets (checkboards, circles, geometric patterns), the system uses naturally occurring feature points in the environment captured by the stereo camera system. This eliminates the need for specialized calibration hardware while maintaining calibration precision through feature point tracking and trifocal constraint equations.
Solution Approach 2:
The patent makes the calibration process universal by enabling it to occur in any environment without specialized equipment. The same stereo camera system used for autonomous navigation can perform self-calibration in the field using ordinary environmental features. The calibration process becomes multi-functional, serving both calibration and operational imaging purposes without requiring separate calibration hardware or laboratory settings.
2Reliability
If conventional systems use timestamps and synchronization hardware for camera synchronization, then reliability is improved, but device complexity and ease of operation worsen due to additional software and hardware requirements
Solution Approach 1:
The patent implements self-service synchronization where the stereo camera system automatically determines relative timing between cameras through the calibration process itself. Rather than relying on external timestamp synchronization hardware or complex software protocols, the system uses the geometric constraints of trifocal points and image capture timing inherently embedded in the calibration algorithm to achieve reliable synchronization without additional components.
3Measurement precision
If conventional systems require calibration targets to be available, then measurement precision is improved, but adaptability and productivity deteriorate due to inability to perform real-time calibration outside laboratory
Solution Approach 1:
The patent transforms the calibration process from a static, pre-laboratory procedure to a dynamic, real-time process. The system can continuously perform calibration in the field as the vehicle moves through the environment, adapting to changing conditions and using dynamically captured images. This enables calibration to occur whenever needed during operation rather than requiring predetermined laboratory sessions with fixed targets.
Solution Approach 2:
The patent transitions calibration from a two-dimensional planar target (checkboard on flat board) to utilizing three-dimensional environmental features and temporal dimension. By tracking feature points across multiple images captured at different times and positions, the system adds temporal and spatial dimensions to the calibration process, enabling real-time calibration without planar targets while maintaining precision through multi-view geometric constraints.
4Stability of the object's composition
If conventional systems use rigid stereo camera brackets, then stability and manufacturing precision are improved, but adaptability worsens as relative poses cannot change during vehicle movement
Solution Approach 1:
The patent performs preliminary calibration to determine the relative pose parameters between cameras, then uses these calibrated parameters throughout operation. Rather than requiring the rigid bracket to maintain perfect alignment under all conditions, the system pre-determines the transformation relationships through calibration and compensates for movements mathematically, allowing the physical mounting to be more flexible while maintaining measurement accuracy through computational correction.
Data Source
AI summary
In various examples, sensor calibration for autonomous or semi-autonomous systems and applications is described herein. Systems and methods are disclosed that calibrate image sensors, such as cameras, using images captured by the image sensors at different time instances. For instance, a first image sensor may generate first image data representing at least two images and a second image sensor may generate second image data representing at least one image. One or more feature points may then be tracked between the images represented by the first image data and the image represented by the second image data. Additionally, the feature point(s), timestamps associated with the images, poses associated with image sensors (e.g., poses of a vehicle), and/or other information may be used to determine one or more values of one or more parameters that calibrate the first image sensor with the second image sensor.