Focus Detection Device Signal Division for Mixed Subject Distances
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Solution Overview
Problem
Focus detection errors occur in cameras using phase detection methods when boundaries between focus detection blocks do not align with boundaries between distant and near subjects in the same photographic screen.
Innovation Solution
A focus detection device that divides focus detection signal sequences into multiple partial sequences based on calculated differences, using a difference calculation unit and a division unit to determine focus detection parameters, and adjusts focus accordingly using a focus adjustment parameter determination unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the focus detection pixel row is divided into a plurality of blocks, then the focus detection can be performed for different distance ranges, but focus detection errors occur because boundaries between the blocks do not align with boundaries between distant subjects and near subjects
Solution Approach 1:
The patent divides the focus detection pixel row into multiple blocks, where each block can independently calculate focus detection values. This segmentation allows the system to handle different distance ranges (distant subjects and near subjects) simultaneously by processing each block's data separately, thus resolving the contradiction between adaptability and measurement precision.
Solution Approach 2:
The patent dynamically selects which block's focus detection value to use based on the actual subject distance. The system determines whether the subject is distant or near and selectively outputs the focus detection value from the corresponding block, making the system adaptable to different scenarios while maintaining accurate focus detection for the specific subject type.
2Device complexity
If fixed block boundaries are used for focus detection, then the device complexity is reduced, but focus detection accuracy deteriorates when subject boundaries do not match block boundaries
Solution Approach 1:
The patent segments the focus detection pixel row into multiple blocks with fixed boundaries, simplifying the device structure. Each block independently calculates focus detection values, maintaining low device complexity while enabling accurate focus detection through selective use of block results based on subject type.
Solution Approach 2:
The system dynamically selects the appropriate focus detection value from different blocks based on subject distance determination. This dynamic selection mechanism maintains simple fixed block structures while achieving accurate focus detection by choosing the result from the block corresponding to the actual subject range.
3Device complexity
If the same focus detection parameter is used for all subjects, then the calculation process is simplified, but focus adjustment accuracy deteriorates when both distant and near subjects are present
Solution Approach 1:
The patent calculates focus detection values separately for each block (distant subject block and near subject block) rather than using a single unified calculation. This segmented calculation approach maintains relatively simple processing within each block while improving overall focus adjustment accuracy by selecting the appropriate calculation result based on subject type.
Solution Approach 2:
The system dynamically determines which focus detection parameter to use based on subject distance. When a distant subject is detected, the system uses the focus detection value from the distant subject block; when a near subject is detected, it uses the value from the near subject block. This dynamic parameter selection simplifies the calculation process for each case while achieving accurate focus adjustment.
Data Source
AI summary
A focus detection device includes: a sensor outputting a pair of focus detection signal sequences, each of which being made of a plurality of focus detection signals; a difference calculation unit obtaining a plurality of differences by sequentially calculating differences between focus detection signals corresponding to each other in the pair of focus detection signal sequences; a division unit dividing the pair of focus detection signal sequences into at least two pairs of partial signal sequences based on the plurality of differences; a focus detection parameter calculation unit calculating a first focus detection parameter according to a phase difference amount of a first pair of partial signal sequences and a second focus detection parameter in accordance with a phase difference amount of a second pair of partial signal sequences; and a focus adjustment parameter determination unit determining either the first or second focus detection parameters, as a focus adjustment parameter.