Autofocus Defocus Normalization by Image Height
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Solution Overview
Problem
Existing image pickup apparatuses struggle to accurately determine a single defocus amount for autofocus (AF) when there are differences in defocus amounts corresponding to the image height, leading to inaccurate AF performance.
Innovation Solution
An image pickup apparatus equipped with a focus detector and a processor that performs focus control. The processor acquires first information on the relation between defocus amounts at specific positions and other positions, uses this information to calculate second defocus amounts, and then determines a third defocus amount for focus control from these second defocus amounts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If one defocus amount is determined by comparing defocus amounts in multiple focus detection directions, then focus detection can be performed, but accurate comparison cannot be performed when there is defocus amount difference corresponding to image height
Solution Approach 1:
The patent applies parameter changes by introducing a defocus amount ratio that varies according to image height. This ratio is used to normalize defocus amounts from different image heights before comparison, transforming the parameter space to enable accurate comparison across different detection directions while accounting for image height variations
2Loss of information
If defocus amounts are obtained in multiple focus detection directions, then more focus information is available, but one accurate defocus amount cannot be obtained when defocus amount difference exists due to image height
Solution Approach 1:
The patent transforms multiple defocus amount measurements into a comparable format by applying image height-based ratios, enabling the system to utilize information from multiple detection directions while deriving a single accurate defocus amount through normalized comparison
Solution Approach 2:
The system uses feedback from multiple focus detection directions, comparing defocus amounts after normalization to determine the accurate focus state, leveraging redundant information to improve overall measurement reliability
Data Source
AI summary
An image pickup apparatus includes a focus detector configured to perform focus detection in an imaging area to acquire a plurality of first defocus amounts different from one another in at least one of an image height, a focus detection direction, and an angle of an object; and a processor configured to perform focus control. The processor is configured to acquire first information indicating a relation between a defocus amount at a specific position in the imaging area and a defocus amount corresponding to the at least one in an area other than the specific position, acquire a plurality of second defocus amounts by using the plurality of first defocus amounts and the first information, and acquires a third defocus amount to be used for the focus control from among the plurality of second defocus amounts.