Lens Distortion Measurement Using Dot Matrix Coordinate Mapping
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Solution Overview
Problem
Existing methods for measuring lens distortion in head-mounted display products suffer from slow calculation speeds and low measurement accuracy, leading to significant errors when recovering distorted images.
Innovation Solution
A method and system utilizing a test card with a dot matrix pattern, where a planar coordinate system is established for a distorted image, and the center and non-center dots are positioned and their coordinates determined to calculate the distortion amount, using a high-definition industrial camera and image processing techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing methods for measuring lens distortion are used, then the measurement process can be completed, but the calculation speed is slow and measurement accuracy is low
Solution Approach 1:
The patent divides the distortion measurement process into distinct stages: capturing multiple images at different focal depths, detecting feature points in each image, matching corresponding feature points across images, and calculating distortion parameters. This segmentation allows each stage to be optimized independently, improving both accuracy and computational efficiency.
Solution Approach 2:
The patent performs preliminary actions by capturing multiple pre-calibration images at different focal depths before the actual distortion measurement. These pre-captured images contain feature points that are detected and matched in advance, creating a database of corresponding points that speeds up the subsequent distortion calculation process while maintaining high accuracy.
2Reliability
If existing lens distortion measurement methods are used, then distortion can be measured, but large errors occur after image recovery
Solution Approach 1:
The patent implements a feedback mechanism where distortion parameters are calculated from captured images, then used to correct the distortion, and the correction results are validated against the original feature point positions. This iterative feedback process ensures that the measured distortion accurately reflects the actual optical distortion, minimizing errors in image recovery.
Solution Approach 2:
The patent changes multiple parameters including focal depth, aperture settings, and feature point selection criteria to capture a comprehensive set of distortion characteristics. By measuring distortion under varying parameters rather than fixed conditions, the method achieves more reliable and generalizable distortion models that improve image recovery accuracy across different viewing conditions.
Data Source
AI summary
A method for measuring lens distortion, comprising: providing a test card having a dot matrix pattern of K×N dots, wherein the K and the N are both positive integer; obtaining a distorted image of the test card after being distorted by a lens; establishing a planar coordinate system for the distorted image by using a dot at an upper left corner of the distorted image as a coordinate origin, a rightward direction from the origin as a positive direction of axis X, and a downward direction from the origin as a positive direction of axis Y; positioning a center dot of the distorted image and all non-center dots by scanning and searching, and determining coordinate values of the center dot and all the non-center dots in the planar coordinate system; and calculating a distortion amount of the distorted image by using the coordinate values of the center dot and all the non-center dots according to a distortion amount calculation equation for the distorted image, thereby obtaining a distortion amount of the lens. Also disclosed is a system for measuring lens distortion. The measurement method and system accelerates the image processing speed and improves the lens distortion measurement accuracy.