Interchangeable Lens Focus Sensitivity by Image Height
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Solution Overview
Problem
In interchangeable lens image capturing systems, achieving a good in-focus state at varying image heights is challenging due to differences in defocus amounts, leading to decreased accuracy and longer focusing times, especially with wide-angle lenses where focus sensitivity varies significantly across the image frame.
Innovation Solution
The system calculates the drive amount of the focus lens using focus sensitivity specific to the image height where the defocus amount is detected, storing focus sensitivity information in the interchangeable lens and using it to adjust focus drive commands, allowing for accurate autofocus at any image height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If focus sensitivity corresponding to the center of the image surface (image height of zero) is used for focus detection at positions where image height is not zero, then the focusing system can operate with a single focus sensitivity value, but the in-focus accuracy decreases due to the significant difference in defocus amounts at different image heights
Solution Approach 1:
The patent applies local quality by storing multiple focus sensitivity values in the lens apparatus, each corresponding to different image height positions. The camera body selects and uses the appropriate focus sensitivity value based on the actual focus detection position's image height, ensuring that each local region uses its optimal sensitivity parameter for accurate focus calculation.
Solution Approach 2:
The system dynamically adapts the focus sensitivity value based on the focus detection position. Instead of using a fixed center-based sensitivity value, the system selects from multiple stored sensitivity values according to the actual image height where focus detection is performed, making the focus control adaptive to different positions across the image surface.
2Measurement precision
If focus sensitivity values for different image heights are stored in the lens apparatus, then in-focus accuracy is improved at any image height, but the device complexity increases due to additional memory storage requirements
Solution Approach 1:
The patent implements local quality by storing multiple focus sensitivity values in the lens apparatus, each corresponding to different image height positions. The camera body selects and uses the appropriate focus sensitivity value based on the actual focus detection position's image height, ensuring that each local region uses its optimal sensitivity parameter for accurate focus calculation.
3Ease of operation
If a single focus sensitivity value is used for the entire image frame, then the system operation is simplified, but the focusing time increases due to the need for repetitive focusing attempts at marginal image heights where defocus amounts differ significantly
Solution Approach 1:
The patent applies preliminary action by pre-storing multiple focus sensitivity values corresponding to different image height positions in the lens apparatus before actual focus detection. When focus detection is performed, the system can immediately select the appropriate sensitivity value based on the detection position, avoiding the need for repetitive focusing attempts and reducing overall focusing time.
Data Source
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AI summary
The interchangeable lens apparatus (100) provided with an image capturing optical system and being detachably attachable to an image capturing apparatus (200), the image capturing apparatus being configured to detect a defocus amount of the image capturing optical system by using a signal acquired by photoelectric conversion of an optical image formed by the image capturing optical system. The interchangeable lens apparatus includes a focus lens (105) included in the image capturing optical system, and a memory (220) to store information on a focus sensitivity indicating a relation between a unit movement amount of the focus lens and a displacement amount of the optical image. The information on the focus sensitivity is information for enabling acquiring the focus sensitivity different depending on an image height.