Focus Detection Correction Using Pupil Region Signal Correlation
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Solution Overview
Problem
Existing image capturing apparatuses face challenges in performing high-speed and high-accuracy focus detection due to fixed pattern noise, which affects the correlation calculation results and requires significant memory capacity and processing time for correction across the entire image sensor surface.
Innovation Solution
The apparatus acquires signals from first and second photoelectric converters receiving light through different pupil regions of the image capturing optical system, calculates a correlation value, and corrects it based on the light receiving amount of at least one of the converters to determine the defocus amount, thereby improving focus detection accuracy and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If correction is performed on the entire surface of the image sensor to remove fixed pattern noise, then the focus detection accuracy is improved, but the memory capacity required and processing time increase significantly
Solution Approach 1:
The patent divides the image sensor surface into multiple regions and performs correction only on the specific region where focus detection is performed, rather than processing the entire sensor surface. This segmentation approach reduces the data volume requiring correction, thereby decreasing processing time and memory requirements while maintaining focus detection accuracy.
Solution Approach 2:
The patent applies correction selectively to the local region of interest for focus detection rather than uniformly across the entire image sensor. By concentrating computational resources on the relevant local area, the system achieves accurate focus detection with reduced processing overhead and lower memory demands.
2Measurement precision
If correction is performed on the entire surface of the image sensor to remove fixed pattern noise, then the focus detection accuracy is improved, but the memory capacity required increases
Solution Approach 1:
The patent segments the image sensor data into multiple regions and stores correction information only for the region where focus detection is performed. This reduces the quantity of data that must be stored in memory, thereby decreasing the required memory capacity while still achieving accurate focus detection through selective correction.
Solution Approach 2:
The patent implements local correction by storing and applying correction values only for the specific region of interest rather than for the entire image sensor surface. This localized approach minimizes memory usage while maintaining the accuracy needed for focus detection in the target region.
3Measurement precision
If phase difference detection is performed using divided photodiodes receiving light through different pupils, then focus detection capability is enabled, but the correlation calculation results are affected by fixed pattern noise
Solution Approach 1:
The patent extracts and removes the fixed pattern noise component from the correlation calculation results obtained through phase difference detection. By separating and eliminating the noise element, the system preserves the focus detection capability while improving the reliability of the correlation calculations.
Solution Approach 2:
The patent converts the harmful effect of fixed pattern noise into a beneficial correction process. By characterizing the noise pattern and applying appropriate correction to the correlation results, the system transforms the previously detrimental noise influence into an opportunity to enhance measurement reliability.
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
This approach enables high-speed and high-accuracy focus detection by reducing the influence of fixed pattern noise and optimizing memory usage, allowing for precise focus positioning without the need for extensive memory capacity or prolonged processing times.
Implementation Method 1
a first photoelectric converter and a second photoelectric converter that receive light beams passing through different pupil regions of an image capturing optical system from each other
Data Source
AI summary
A control apparatus includes an acquirer (129a) that acquires a first signal and a second signal that correspond to output signals of a first photoelectric converter and a second photoelectric converter, respectively, the first and second photoelectric converters receiving light beams passing through different pupil regions of an image capturing optical system from each other, and a calculator (129b) that calculates a correlation value of the first signal and the second signal to calculate a defocus amount based on the correlation value, and the calculator corrects the correlation value based on a light receiving amount of at least one of the first photoelectric converter and the second photoelectric converter.