Phase Difference Focus Detection in Image Pickup Apparatus
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Solution Overview
Problem
Existing focus detection methods using one-dimensional images are weak in detecting objects with repeated patterns and suffer from accuracy deterioration in the periphery due to influences from object shape and vignetting.
Innovation Solution
An image pickup apparatus that generates pairs of image signals from light beams passing through different pupil regions, detects the baseline length and pupil division direction, and calculates phase differences in the pupil division direction using these signals to perform highly accurate focus detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If one-dimensional image focus detection is used, then the focusing speed is improved, but the focus detection accuracy deteriorates in the periphery due to object shape and vignetting influences
Solution Approach 1:
The patent transitions from one-dimensional image processing to two-dimensional phase difference calculation. By calculating phase differences in both horizontal and vertical directions and synthesizing these two-dimensional measurements, the system achieves accurate focus detection across the entire image area including the periphery, while maintaining high focusing speed through efficient computational methods.
2Device complexity
If focus detection pixels are arranged in defect sections of image pickup pixels, then the device complexity is reduced, but the focus detection accuracy deteriorates due to interpolation errors
Solution Approach 1:
The patent makes all image pickup pixels serve dual functions: both image capture and focus detection. By utilizing the full pixel array for phase difference detection through two-dimensional phase difference calculation, the system eliminates the need for dedicated focus detection pixels in defect sections, thereby improving focus detection accuracy without increasing device complexity.
3Adaptability or versatility
If images are added in oblique direction to perform focus detection for periphery, then the focus detection coverage is improved, but the measurement precision deteriorates due to adding direction influences
Solution Approach 1:
The patent employs asymmetric phase difference calculation in horizontal and vertical directions, recognizing that the optimal addition direction varies by region. By calculating phase differences separately in horizontal and vertical dimensions and synthesizing results, the system adapts to local image characteristics and eliminates errors introduced by fixed oblique addition directions, achieving both comprehensive coverage and high 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
This approach enables accurate focus detection by accounting for vignetting and object shape influences, improving focus detection accuracy, especially in the periphery of the image pickup area.
Implementation Method 1
image pickup element including a plurality of focus detection pixels configured to generate a pair of image signals based on light beams passing through pupil regions different from each other
Data Source
AI summary
An image pickup apparatus includes an image pickup element including a plurality of focus detection pixels configured to generate a pair of image signals based on light beams passing through pupil regions different from each other in an image pickup optical system, a detection unit configured to detect a base line length of the plurality of focus detection pixels and a pupil division direction based on position information of a focus detection region in the image pickup element and information relating to the image pickup optical system, and a calculation unit configured to calculate a phase difference in the pupil division direction by using the pair of image signals.