Stereo Camera Windshield Calibration for Wide-Angle Distortion
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Solution Overview
Problem
Conventional stereo camera calibration methods face challenges in calibrating wide-angle cameras when imaging through a windshield, as the required calibration tools become large and difficult to implement due to increased angle of view.
Innovation Solution
A camera calibration method that involves imaging a calibration object with a linear portion through the windshield, extracting a linear portion image, and correcting distortion based on a virtual image without the windshield, using a stereo camera device with components like left and right cameras, image processing units, and correction units to account for pixel shifts and lens characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the angle of view of the stereo camera is increased to capture a wider field through the windshield, then the calibration tool size must be increased to cover the expanded calibration area, but this makes the calibration process more difficult and impractical
Solution Approach 1:
The patent segments the calibration process into two distinct parts: (1) calibration without windshield interference to establish baseline parameters, and (2) calibration through the windshield to capture distortion characteristics. This segmentation allows each calibration phase to use appropriately sized tools and procedures, avoiding the need for one oversized calibration tool to handle both scenarios simultaneously.
Solution Approach 2:
The patent introduces an intermediary computational process that uses the calibration object imaged through the windshield to calculate correction parameters. This intermediary step bridges the gap between the actual distorted images captured through the windshield and the desired undistorted output, eliminating the need for physically large calibration tools that would otherwise be required to directly calibrate the entire wide-angle view.
2Measurement precision
If conventional calibration methods are used with large calibration tools for wide-angle cameras, then calibration accuracy may be maintained, but the complexity and difficulty of the calibration process increases significantly
Solution Approach 1:
The calibration object itself serves multiple functions: it provides the calibration pattern for distortion measurement, acts as a reference for calculating correction parameters, and enables self-calibration of the system. The processing unit automatically extracts calibration information from images of the calibration object and computes correction parameters without requiring complex external calibration equipment or manual intervention.
Solution Approach 2:
The patent changes the calibration approach from using physical calibration tools of various sizes to using a standardized calibration object with known geometric parameters. By imaging this calibration object through the windshield and analyzing the distortion of its known features, the system calculates correction parameters that compensate for windshield-induced distortion, maintaining accuracy while simplifying the physical calibration setup.
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 easy calibration of wide-angle cameras capturing images through windshields by correcting pixel shifts and distortions, allowing for accurate distance measurements and object detection, even with large windshield inclinations and lens pupil shifts.
Implementation Method 1
capturing an image through a windshield
Data Source
AI summary
A camera calibration method for calibrating a camera that captures an image through a windshield includes acquiring a calibration image associated with a calibration object by imaging by the camera. A calibration object has a linear portion extending in one direction intersecting an optical axis of the camera through the windshield, and the calibration object is a wire or a bar. The method further includes extracting a first linear portion image corresponding to the linear portion from the calibration image. The method further includes correcting distortion of the calibration image by comparing the first linear portion image with a second linear portion image captured when the linear portion is imaged by the camera not through the windshield.