Focus Lens Position Correction for Thermal and Mechanical Drift
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Solution Overview
Problem
Existing lens control systems face issues with mechanical deformation, temperature changes, and individual differences leading to inaccuracies in lens positioning, resulting in focus shifts and inability to move lenses to intended positions.
Innovation Solution
A lens control apparatus that corrects the difference between specified and actual driving amounts using temperature data, pulse count values, and focus evaluation values to ensure accurate lens positioning, incorporating mechanisms for resetting these values when deviations occur.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If lens driving is performed based on predetermined driving amount, then lens positioning speed is improved, but positioning precision deteriorates due to mechanical deformation and orientation differences
Solution Approach 1:
The system uses autofocus evaluation values as feedback to detect actual lens positioning accuracy. By comparing the expected position with the actual focus evaluation, the system calculates correction amounts to compensate for mechanical deformations and orientation differences, thereby maintaining positioning precision while using predetermined driving amounts for speed.
Solution Approach 2:
The system dynamically adjusts driving parameters by calculating correction amounts based on temperature, orientation, and focus evaluation data. This allows the lens driving unit to modify its operation in real-time, compensating for mechanical variations while maintaining efficient predetermined driving amounts.
2Manufacturing precision
If correction information is stored for each lens to compensate for individual differences, then positioning precision is improved, but device complexity and data transfer time increase
Solution Approach 1:
Instead of storing comprehensive correction data for every possible condition, the system acquires and stores only the necessary correction information specific to each lens's actual performance characteristics. This selective approach reduces data complexity while maintaining precision for the specific lens installed.
Solution Approach 2:
The system performs self-calibration by using the autofocus evaluation function to automatically determine correction amounts for each lens. This eliminates the need for complex external calibration procedures and reduces the burden of data management, as the system generates its own correction information through normal operation.
3Ease of operation
If focus is fixed after initial adjustment, then operational simplicity is improved, but focus accuracy deteriorates due to temperature-induced expansion and contraction
Solution Approach 1:
The system transitions from a static fixed focus approach to a dynamic correction approach. By continuously monitoring temperature changes and applying real-time correction amounts to the lens position, the system maintains focus accuracy despite thermal expansion and contraction, while requiring minimal user intervention.
Solution Approach 2:
The system performs preliminary correction by calculating and applying temperature compensation amounts in advance based on detected temperature changes. This proactive adjustment prevents focus drift before it occurs, maintaining accuracy without requiring continuous manual intervention.
Data Source
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AI summary
A lens control apparatus having an imaging optical system including a focus lens includes a lens control unit configured to control a position of a lens of the imaging optical system based on a control driving amount of the lens, an acquisition unit configured to acquire driving information including an actual driving amount of the lens controlled by the lens control unit, and a first correction unit configured to correct the position of the lens based on a difference between the control driving amount and the actual driving amount. The first correction unit corrects the position of the lens by adding or subtracting an amount of correction to or from the control driving amount when the lens control unit next performs the control of the position of the lens, such that the difference decreases.