Image Capture Apparatus Phase-Difference Autofocus Computation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing image capture apparatuses using phase-difference detection methods for autofocus often require significant computation and may fail to focus on the intended subject, especially for subjects with small defocus amounts, due to incomplete correlation computation.
Innovation Solution
An image capture apparatus and method that generates pairs of image signals with different detectable defocus amount ranges and detection accuracies by compressing data volumes at varying compression rates, allowing for efficient correlation computation and accurate focus detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If correlation computation is performed for the entire shift area to ensure accurate focus detection, then measurement precision is improved, but computing time increases
Solution Approach 1:
The patent divides the correlation computation area into a first correlation computation area and a second correlation computation area. The first area is used for initial focus detection with coarser resolution, while the second area is used for refined focus detection with higher resolution. This segmentation allows the system to achieve accurate focus detection without computing across the entire shift area, thereby reducing computing time while maintaining measurement precision.
2Loss of time
If correlation computation is ended at the extremal value point to reduce computation, then computing time is reduced, but focus detection accuracy deteriorates for subjects with small defocus amounts
Solution Approach 1:
The patent employs a dynamic two-stage correlation computation approach. In the first stage, correlation computation is performed with a first correlation amount calculation range to detect the extremal value. In the second stage, if further precision is needed, computation continues with a second correlation amount calculation range that extends beyond the first range. This dynamic adjustment of computation range allows the system to reduce computing time for most cases while maintaining accuracy for subjects with small defocus amounts.
3Adaptability or versatility
If multiple pairs of image signals with different compression rates are generated, then adaptability to various defocused states is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by generating different pairs of image signals with different compression rates for different defocus scenarios. Specifically, a first pair of image signals is generated with a first compression rate for general focus detection, while a second pair of image signals is generated with a second compression rate for specific defocus ranges. This allows the system to adapt to various defocused states efficiently by selecting the appropriate signal pair, improving versatility without overwhelming complexity.
Data Source
AI summary
Regarding one or more pairs of image signals generated based on a signal obtained from an image sensor, a phase difference of the image signals is determined and a defocus amount is calculated based on the phase difference based on a correlation amount calculated while relatively shifting the positions of the one or more pairs of image signals. By using image signals whose detectable defocus amount range and defocus amount detection accuracies are different, the amount of correlation calculation for focus detection can be reduced in various defocused states of a subject for which focus detection is to be performed.