Focusing Control Device Selective Phase Difference Measurement
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Solution Overview
Problem
The phase difference AF method faces challenges in maintaining focusing accuracy, especially when the focus detection area is small, as it is influenced by noise and periodic patterns, making it difficult to accurately determine the phase difference amount, particularly when the subject moves.
Innovation Solution
A focusing control device and method that utilize a sensor with divided focus detection areas, where first and second signal detection sections acquire correlation values and measure phase difference amounts, allowing for selective determination of the focus lens position based on these values to improve focusing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the focus detection area is made small to accurately focus on the main subject, then the focusing precision on the main subject is improved, but the measurement precision of the phase difference amount deteriorates due to noise influence and periodic patterns
Solution Approach 1:
The focus detection area is divided into multiple regions (first focus detection area and second focus detection area) to enable selective measurement. By segmenting the detection area, the system can choose regions with sufficient signal strength while maintaining small effective detection areas for accurate main subject focusing, thus resolving the contradiction between small area requirement and noise resistance.
Solution Approach 2:
The system dynamically selects which focus detection area to use based on real-time correlation value measurements. When the first focus detection area shows strong correlation (indicating sufficient signal), it is used for measurement; otherwise, the second area is selected. This dynamic adaptation allows the system to maintain reliable focusing accuracy under varying conditions while preserving the benefits of small detection areas.
2Reliability
If the focus detection area is made large to include sufficient feature points, then the measurement precision of the phase difference amount is improved, but the focusing precision on the main subject deteriorates due to background inclusion
Solution Approach 1:
The detection system is segmented into multiple focus detection areas with different characteristics. The first area is optimized for main subject focusing with smaller size, while the second area serves as a backup with potentially different characteristics. This segmentation allows the system to achieve reliable measurements by selecting the appropriate segment for the given conditions without requiring a single large area that would always include background.
Solution Approach 2:
The correlation value calculation acts as an intermediary mechanism that bridges the trade-off between area size and measurement quality. By evaluating correlation values from the first focus detection area and using them as a decision criterion, the system indirectly selects the optimal detection area configuration, thus resolving the contradiction between large area reliability and small area focusing precision.
3Measurement precision
If the focus detection area is made small to exclude background, then the main subject focusing precision is improved, but the device complexity increases due to the need for multiple detection areas and selective determination logic
Solution Approach 1:
Instead of using a single complex detection system, the patent segments the detection function into multiple simpler focus detection areas. Each area can be independently configured and evaluated, reducing the complexity of any single detection region while achieving the desired precision through selective use of multiple segments.
Solution Approach 2:
The system implements a multi-area detection approach where having more detection areas than strictly necessary provides redundancy and simplifies the selection logic. By preparing multiple potential detection areas in advance with clear selection criteria based on correlation values, the system avoids the need for complex real-time optimization algorithms, thus reducing overall device complexity while maintaining high focusing precision.
Data Source
AI summary
A focusing control device includes: a sensor as defined herein; a first correlation value generation unit as defined herein; a second correlation value generation unit as defined herein; a first phase difference amount measurement unit as defined herein; a second phase difference amount measurement unit as defined herein; a target position determination unit that selectively performs a first process of determining a target position of the focus lens based on the first phase difference amount and a second process of determining the target position of the focus lens based on the second phase difference amount, based on the correlation values acquired by the first correlation value generation unit and the correlation values acquired by the second correlation value generation unit; and a lens driving control unit that drives the focus lens to the target position determined through the first process or the second process.