Focus Detection Pixel Defect Correction for Precision
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Solution Overview
Problem
Existing multi-point focus detection systems face challenges in maintaining precision during in-focus operations due to manufacturing defects in photoelectric conversion portions, which can lead to reduced correlation between focus detection images and errors, especially when defective pixels are positioned at critical points in object images.
Innovation Solution
A focus detection apparatus and method that utilize a combination of first and second focus detection pixels, with defect information storage and correction/elimination mechanisms to address defective pixels, allowing for accurate focusing status detection by correcting or eliminating the defective pixel values within focus detection pixel pairs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of photoelectric conversion portions is increased to achieve multi-point focus detection, then focus detection precision is improved, but manufacturing defects in photoelectric conversion portions become more likely to occur
Solution Approach 1:
The patent applies preliminary action by storing defect information in advance before focus detection operations. The system pre-identifies and records which photoelectric conversion portions are defective, then uses this stored information to selectively exclude defective pixels from correlation calculations, ensuring reliable focus detection despite the presence of defects in the increased number of photoelectric conversion portions.
Solution Approach 2:
The patent extracts and removes the influence of defective photoelectric conversion portions from the focus detection process. By identifying defective pixels and excluding them from correlation calculations, the system separates the useful signal from the harmful defective signals, maintaining measurement precision even when many photoelectric conversion portions are used.
2Reliability
If defective pixels are interpolated from nearby signals to reduce defect influence, then device reliability is improved, but correlation with the other focus detection image is lost
Solution Approach 1:
The patent converts the harmful effect of defective pixels into a beneficial selection process. Instead of interpolating defective pixel values (which would create false correlation data), the system uses defect information to identify and exclude only the necessary defective pixels from correlation calculations. This approach maintains the integrity of the correlation calculation by preserving genuine signal relationships while removing only the harmful defective signals.
3Measurement precision
If defective pixels are eliminated from focus detection calculations, then measurement precision is maintained, but the number of usable focus detection pixels decreases
Solution Approach 1:
The patent applies local quality by treating each photoelectric conversion portion individually based on its specific condition. Instead of uniformly excluding all pixels or interpolating all defective ones, the system selectively excludes only the specific defective pixels identified through stored defect information while maintaining the use of all functional pixels. This localized approach preserves the maximum number of usable pixels while maintaining measurement precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively prevents precision loss during in-focus operations by accurately detecting focusing status even with defective pixels, reducing focus detection errors and enhancing the yield and cost-effectiveness of image sensors.
Implementation Method 1
a focus detection sensor that includes a plurality of first focus detection pixels and a plurality of second focus detection pixels
Data Source
AI summary
A camera has a focus detection sensor that includes a plurality of first focus detection pixels and a plurality of second focus detection pixels, and that has a plurality of focus detection pixel pairs each including a first focus detection pixel and a second focus detection pixel, and stores defect information indicating a defective pixel. The camera corrects a value of the defective pixel and a value of one of the first focus detection pixel and the second focus detection pixel that forms the focus detection pixel pair with the defective pixel based on a value of a focus detection pixel of the same type that is not the defective pixel. The camera detects focusing status based on a phase difference between a first focus detection image obtained from the first focus detection pixels and a second focus detection image obtained from the second focus detection pixels after the correction.