Imaging Apparatus Dynamic Weighting for Exposure Control
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Solution Overview
Problem
Conventional imaging apparatuses face challenges in exposure control when the depth of field is deep, causing background areas to be overly weighted, which disrupts appropriate exposure for the main object due to the assignment of weighted values based on defocus amounts in focus detection areas.
Innovation Solution
An imaging apparatus with a defocus amount acquisition unit, light metering unit, and determination unit that adjusts weighting coefficients for light metering areas based on defocus amounts, allowing for dynamic weighting to prioritize exposure control for the main object by differentiating between focus detection areas with varying defocus values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a larger weighted value is assigned to light metering areas with smaller defocus amounts (in focus areas), then the main object exposure is improved, but background areas with large defocus amounts still exert excessive influence when depth of field is deep, disturbing appropriate exposure control
Solution Approach 1:
The patent applies dynamics by making the weighting coefficient adjustment dynamic rather than static. The determination unit dynamically adjusts weighting coefficients based on the distribution of defocus amounts across all focus detection areas. When the depth of field is deep and many background areas are in focus, the system dynamically reduces their weighting influence, whereas when the background is naturally out of focus, it allows greater weighting. This dynamic adaptation resolves the contradiction between maintaining accurate main object exposure and adapting to varying depth of field conditions.
Solution Approach 2:
The patent employs parameter changes by modifying the weighting coefficients based on the statistical distribution of defocus amounts. Instead of using fixed weighting based solely on individual defocus amounts, the system changes the weighting parameters by comparing each area's defocus amount against the overall distribution pattern. This parameter adjustment allows the system to differentiate between main objects and background areas even when both are in focus, thereby resolving the exposure control disturbance caused by deep depth of field conditions.
2Device complexity
If weighting is based solely on absolute defocus amount, then simple exposure control is achieved, but background brightness excessively influences exposure when many areas are in focus
Solution Approach 1:
The patent introduces an intermediary mechanism - the determination unit that analyzes the distribution pattern of defocus amounts across all focus detection areas. This intermediary layer processes the raw defocus amount data and generates adjusted weighting coefficients that account for the overall scene context. Rather than directly using absolute defocus amounts as weights, the system uses this intermediary analysis to mediate the weighting process, thereby preventing background brightness from excessively influencing exposure while maintaining a relatively simple overall structure.
Data Source
AI summary
A determination unit determines a weighting coefficient for a second light metering area corresponding to a focus detection area at which a second defocus amount having an absolute value larger than an absolute value of a first defocus amount is acquired relatively smaller than a weighting coefficient for a first light metering area corresponding to a focus detection area at which a first defocus amount is acquired, and changes a difference between the weighting coefficient for the first light metering area and the weighting coefficient for the second light metering area based on a plurality of defocus amounts including the defocus amount of the focus detection area not corresponding to the first light metering area and the second light metering area.