Non-Single-Focal Camera Model for 3D Position Measurement
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Solution Overview
Problem
Existing three-dimensional position measuring apparatuses using single-focal camera models face accuracy issues when objects are placed between cameras and targets, such as in-vehicle setups, due to the complexity of calibrating intrinsic and extrinsic parameters, especially when cameras experience vibrations.
Innovation Solution
A position measuring apparatus that uses a non-single-focal camera model with two common planes for each camera, eliminating the need for extrinsic parameters by calculating projected points and restoring three-dimensional positions based on intrinsic camera parameters, simplifying calibration and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-focal camera model is used for three-dimensional position measurement, then the system is simple to implement, but measurement accuracy greatly decreases when objects are placed between cameras and target subjects
Solution Approach 1:
The patent changes the fundamental parameters of the camera model from a single-focal model to a non-single-focal model with multiple focal points. This involves introducing new parameters such as multiple focal lengths and corresponding focal points for each camera, allowing the system to account for refraction effects when light passes through objects like windshields. This parameter transformation resolves the contradiction by enabling accurate 3D position measurement in complex optical environments while maintaining reasonable system complexity.
2Measurement precision
If a non-single-focal camera model with intrinsic and extrinsic parameters is used, then measurement accuracy is improved, but camera calibration becomes complicated requiring adjustment of both intrinsic and extrinsic parameters
Solution Approach 1:
The patent extracts and eliminates the extrinsic parameters from the calibration process by formulating a method that only requires intrinsic parameters for calibration. The approach separates the intrinsic parameter calibration (focal lengths and focal points) from the extrinsic parameter adjustment (positional relationships between cameras), allowing calibration to be performed using only intrinsic parameters while still achieving accurate 3D position measurement. This extraction principle resolves the contradiction by simplifying calibration while maintaining measurement precision.
3Measurement precision
If extrinsic parameters are required for camera calibration, then accurate positional relationships among cameras can be established, but dynamic recalibration becomes difficult when camera positions change due to vibrations
Solution Approach 1:
The patent implements a dynamic calibration approach where intrinsic parameters (focal lengths and focal points) can be continuously or periodically recalibrated without requiring extrinsic parameter adjustment. The system allows cameras to be recalibrated in situ even when their positional relationships change due to vibrations or movement, by重新 estimating intrinsic parameters based on current image data. This dynamic capability resolves the contradiction by enabling accurate measurement even when camera positions change, without requiring complex re-calibration of extrinsic parameters.
Data Source
AI summary
A position measuring apparatus detects, from respective first and second imaging planes of first and second captured images, first and second corresponding points estimated to represent a common three-dimensional position. The apparatus calculates first to fourth projected points. Each of the first and second projected points represents a projected point of the first corresponding point on a corresponding one of the first and second common planes. Each of the third and fourth projected points represents a projected point of the second corresponding point on a corresponding one of the first and second common planes. The apparatus calculates a first beam connecting the first and second projected points, a second beam connecting the third and fourth projected points, and a point having a minimum square distance relative to each of the first and second beams as a restored point representing the three-dimensional position of the first and second corresponding points.