Camera Resolution Measurement Using Distorted Test Charts
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Solution Overview
Problem
Existing contrast methods for measuring camera resolution fail when distortion is present, as they generate harmonics components and change frequency intervals, making accurate MTF measurement impossible for cameras with distortion in the photography field of view, such as fish-eye cameras.
Innovation Solution
A resolution measurement method using a computer device that generates a distortion map and a distorted test chart through back projection, allowing accurate resolution measurement by the contrast method even in cameras with distortion, by correcting for geometric distortions using a computer device, display, and camera system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the contrast method is used for resolution measurement, then measurement precision is improved, but it cannot be applied to cameras with distortion
Solution Approach 1:
The patent applies preliminary action by pre-distorting the test chart image according to the camera's distortion characteristics before display. This allows the contrast method to be applied to distorted cameras by anticipating and compensating for distortion effects in advance, enabling accurate resolution measurement that would otherwise be impossible with conventional undistorted test patterns.
Solution Approach 2:
The patent changes the parameters of the test chart by applying distortion transformation to create a distorted test chart image with specific distortion characteristics matching the camera's optical distortion. This parameter modification enables the test pattern to accommodate distorted camera optics while maintaining measurement accuracy through subsequent compensation algorithms.
2Adaptability or versatility
If the slanted-edge method is used, then applicability to distorted cameras is improved, but measurement precision deteriorates due to image processing effects
Solution Approach 1:
The patent extracts and removes the distortion effect from the measurement process by using a distorted test chart that accounts for camera distortion. This allows the measurement to be performed on the distorted image directly without requiring additional image processing or distortion correction steps that would compromise measurement precision.
3Adaptability or versatility
If a distorted test pattern is used in the contrast method, then harmonics components are generated, but measurement precision is maintained through distortion correction
Solution Approach 1:
The patent applies feedback by using the known distortion characteristics of the camera to pre-distort the test chart, then using algorithms to compensate for the introduced distortion in the measurement process. This feedback loop ensures that harmonics components generated by distortion are properly accounted for, maintaining MTF measurement accuracy even with distorted test patterns.
Data Source
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AI summary
Provided is a method for measuring the resolution of a camera having distortion in the photography field of view thereof. A resolution measurement method, that is performed by a computer device, for a camera comprising: generating a distortion map which represents correspondence relation between coordinates of all pixels of a first test chart and coordinates of all pixels of the first test chart in an image captured by a camera which causes distortion in a photography field of view; generating, according to the correspondence relation represented by the distortion map, a distorted test chart which is a distorted image of a second test chart that is used for measuring resolution at a specific area in the first test chart in the captured image; and performing, by using the distorted test chart, measurement of resolution according to a contrast method at a part, that corresponds to the specific area, in the photography field of view of the camera.