Lens Position Calibration for Chromatic Aberration Autofocus
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Solution Overview
Problem
Existing image processing systems face challenges in achieving optimal focus and resolution due to chromatic aberration, which affects the focal positions of different color channels, leading to suboptimal image quality.
Innovation Solution
An image processing system that performs calibration for each color channel to determine the movement distance of the optical lens based on a modeled relationship between disparity and lens position, using disparity conversion coefficients and weights to improve focus accuracy, particularly for the green channel, which has the greatest impact on resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single focal position is used for all color channels, then the device complexity is reduced, but the image resolution and focus precision deteriorate due to chromatic aberration
Solution Approach 1:
The patent applies local quality by determining separate focal positions for different color channels (red, green, blue) instead of using a single focal position for all channels. The processor calculates channel-specific movement distances based on disparity values and calibrated relationships, allowing each color channel to be focused at its optimal position while accounting for chromatic aberration. This resolves the contradiction by improving image resolution through differentiated focus control without significantly increasing system complexity.
2Manufacturing precision
If separate focal positions are determined for each color channel, then the image resolution is improved, but the device complexity increases
Solution Approach 1:
The patent applies preliminary action by performing calibration in advance to establish the relationship between disparity values and movement distances for each color channel. The processor stores calibrated parameters (a1, b1 for red channel; a2, b2 for blue channel) that are determined beforehand through calibration processes. During actual operation, the system simply applies these pre-calculated parameters to determine focal positions, avoiding the need for complex real-time calculations and reducing operational complexity while maintaining high image resolution.
3Ease of operation
If the optical lens is moved according to average disparity across all channels, then the operation is simplified, but the green channel sharpness and overall image quality deteriorate
Solution Approach 1:
The patent applies parameter changes by introducing channel-specific calibration parameters (a1, b1 for red; a2, b2 for blue) that modify the basic disparity-to-movement-distance relationship. The processor calculates movement distances using these adjusted parameters: dr = disp_r × a1 + b1 for red channel and db = disp_b × a2 + b2 for blue channel. The green channel movement is then derived from these adjusted parameters. This allows the system to maintain simple operation while achieving precise green channel sharpness by transforming the calculation parameters rather than complicating the operational process.
Data Source
AI summary
An image processing system includes an optical lens, a lens driver, an image sensor, and a processor. The processor is configured to, based on a modeled relationship between a disparity and a position of the optical lens for each of a first to a third color channels, and further based on a position of the optical lens at which a sharpness of the third color channel is maximized, determine, for each color channel, a movement distance of the optical lens according to the disparity; determine a disparity value and a weight for each color channel from the image data; and apply the disparity value and the weight to the movement distance of the optical lens for each color channel, to determine a final movement distance of the optical lens. The lens driver is configured to move the optical lens according to the final movement distance.