Focus Control Apparatus Spatial Frequency Weighting Correction
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Solution Overview
Problem
Existing focus detection methods, such as those described in Japanese Patent No. 5087077, fail to accurately correct focus detection errors due to the lack of consideration for the focus state of the captured image, leading to insufficient correction of focus detection results.
Innovation Solution
A control apparatus and method that acquire information about the peak position of spatial frequencies transmitted by an image pickup optical system, calculate evaluation bands for image pickup and focus detection signals, and apply weighting for each spatial frequency to calculate correction information for focus detection, thereby improving the accuracy of focus control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If focus detection is performed using conventional methods (contrast detection or phase-difference detection), then focus detection can be implemented, but focus detection errors occur due to optical system aberrations and evaluation band differences
Solution Approach 1:
The patent applies parameter changes by calculating correction values based on different evaluation bands (spatial frequency characteristics) and applying appropriate correction to the focus detection result. The correction value changes parameters such as evaluation band weighting to compensate for optical system aberrations and match the perceived focus state.
2Measurement precision
If correction values are calculated based on evaluation band as in Japanese Patent No. 5087077, then some focus detection error correction is achieved, but the correction is insufficient because the focus state of the captured image is not considered
Solution Approach 1:
The patent implements feedback by using the captured image data to calculate the actual focus state and comparing it with the detected focus state. This feedback loop allows the system to adjust the correction values to better match the perceived focus state, thereby reducing focus detection errors.
Solution Approach 2:
The patent adds another dimension to the correction process by considering spatial frequency characteristics and evaluation bands. Instead of simple correction, it multi-dimensionally analyzes the focus detection signals across different spatial frequencies to calculate more accurate correction values that reflect the actual focus state.
3Ease of manufacture
If simple focus detection correction is applied, then processing is simple, but the correction accuracy is insufficient
Solution Approach 1:
The patent segments the focus detection process into multiple stages: acquiring focus detection signals, calculating evaluation bands for different spatial frequencies, determining correction values based on optical system characteristics, and applying corrections. This segmentation makes the complex correction process manageable while maintaining high accuracy.
Data Source
AI summary
A control apparatus (125) includes an acquirer (125d) configured to acquire first information relating to a peak position of a spatial frequency that an image pickup optical system transmits for each spatial frequency, and a processor (125e, 125f, 125g) configured to calculate second information relating to a first evaluation band used for processing of image pickup signals and a second evaluation band used for processing of focus detection signals, the processor is configured to calculate third information relating to a weighting for each spatial frequency, and the processor is configured to calculate correction information of focus detection based on the first, second, and third information.