Interchangeable Lens Autofocus Correction via Reference Data
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Solution Overview
Problem
The contrast-based autofocus function in interchangeable lens camera systems is affected by spherical aberrations and varying evaluated AF frequencies, leading to inconsistent focus positions when different lenses and camera bodies are combined, which compromises the best AF performance.
Innovation Solution
A camera system with a lens unit and camera body that includes a focusing mechanism, a computing section for acquiring shooting parameters, and storage for reference data to correct focus positions based on contrast measurements, allowing for interpolation or closest frequency matching to ensure accurate focus regardless of lens and camera combinations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the contrast-based AF function is used with different evaluated AF frequencies for different camera bodies, then the AF operation can be performed adaptively to each camera's specifications, but the focus position shifts due to spherical aberration variations, leading to inconsistent AF performance
Solution Approach 1:
The patent applies preliminary action by pre-measuring and storing the relationship between contrast peak positions and actual best in-focus positions for multiple assumed AF frequencies in reference data before actual shooting. During AF operation, the system calculates correction values based on the evaluated AF frequency and retrieves corresponding correction data from the pre-prepared reference data, eliminating the need for real-time complex calculations and ensuring accurate focus positioning despite frequency variations across different camera bodies
Solution Approach 2:
The patent employs parameter changes by introducing correction values that adjust the contrast peak position based on the evaluated AF frequency. The system changes the focus position parameter from the raw contrast peak position to a corrected position using frequency-specific correction data, thereby compensating for spherical aberration effects and maintaining consistent AF performance across different camera bodies with different evaluated AF frequencies
2Productivity
If the contrast peak position is used directly as the AF position, then the AF operation is simple and fast, but the AF position deviates from the best in-focus position when spherical aberration is present
Solution Approach 1:
The patent implements feedback by calculating correction values based on the evaluated AF frequency and using these correction values to adjust the contrast peak position. The system continuously refines the focus position by applying frequency-specific corrections derived from reference data, ensuring that the final AF position accurately reflects the best in-focus position while maintaining the speed of contrast-based AF operation
Solution Approach 2:
The patent introduces correction values as an intermediary between the contrast peak position and the final AF position. These correction values act as a mediator that compensates for spherical aberration effects without requiring complex real-time calculations, thus maintaining operational speed while improving focus accuracy. The correction values are retrieved from pre-computed reference data based on the evaluated AF frequency
Data Source
AI summary
To provide an interchangeable lens camera system for shooting with the best in-focus position, no matter how a group of two or more interchangeable lenses to produce different degrees of spherical aberrations and a group of cameras of different types with different evaluated autofocus frequencies are combined. The camera system of this invention includes a lens unit and a camera body to be removable and attachable from/to each other. The lens unit includes a first computing section for acquiring shooting parameters during a focusing operation and a storage section that stores reference data for changing focus positions according to the contrast of image. The camera body includes an imaging device to output a video signal representing subject's image and a second computing section for measuring the contrast of the image based on its own predetermined evaluated AF frequency during the focusing operation and calculating a correction value based on the shooting parameter and the reference data associated with the highest contrast, thereby changing the focus positions according to the correction value calculated.