Focus Control Apparatus Backlash and Thermal Defocus Correction
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Solution Overview
Problem
Existing image capturing apparatuses face challenges in correcting defocus caused by orientation changes, movement, and thermal changes without uniform correction methods, leading to potential object replacement and suboptimal focus adjustments.
Innovation Solution
A focus control apparatus that calculates and adjusts the focus lens position using backlash data, lens sensitivity, and thermal focus correction methods, allowing for precise defocus correction without the need for orientation detectors, and optimizing thermal focus correction based on temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If uniform correction amount is used to correct focus lens position, then correction process is simple, but blur correction is inaccurate due to individual differences in mechanical backlash and thermal expansion
Solution Approach 1:
The patent applies local quality by storing individual blur amount data for each image capturing apparatus in a storage unit. Instead of using a uniform correction amount for all devices, the system retrieves and applies device-specific blur amounts that account for individual mechanical backlash and thermal expansion characteristics, thereby achieving accurate blur correction while maintaining a relatively simple correction process.
2Reliability
If thermal focus correction is applied, then defocus caused by thermal change is corrected, but object replacement occurs when the focus position shifts to focus on a different object
Solution Approach 1:
The patent implements dynamics by making the focus correction amount variable based on zoom position. The correction amount is calculated as a product of a base blur amount and a zoom position-dependent factor. This dynamic adjustment allows the system to adapt the correction strength according to the current zoom state, preventing excessive correction that would cause object replacement while still effectively correcting thermal defocus across different zoom positions.
Solution Approach 2:
The system uses feedback by continuously monitoring the zoom position and adjusting the thermal focus correction amount accordingly. The correction amount is dynamically recalculated based on the current zoom state, ensuring that the focus adjustment remains appropriate for the current optical configuration and prevents overshooting that would result in object replacement.
3Measurement precision
If orientation detector is added to correct defocus caused by orientation change, then blur correction accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies copying by using data from existing sensors (accelerometer, gyroscope, temperature sensor) to represent orientation and thermal states, rather than adding dedicated orientation detectors. The system copies and processes information from these existing components to calculate blur amounts and apply corrections, achieving accurate orientation-based focus adjustment without increasing device complexity or adding expensive specialized detectors.
Data Source
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AI summary
A focus control apparatus includes a controller configured to provide a focus control that holds an object distance on which an image capturing optical system is focused that includes a magnification varying lens and a focus lens, and a calculator configured to calculate a defocus amount by using information on lens sensitivity that represents a relationship between a unit moving amount of the magnification varying lens and a moving amount of an image plane in the image capturing optical system, and information on error amounts of stop positions of the magnification varying lens and that of the focus lens. The controller moves the focus lens in a moving range limited based on the defocus amount.