Focus Detection Device Using Exit Pupil Segmentation
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Solution Overview
Problem
Conventional focus-detection devices using phase-difference detection type focus detection based on image sensor outputs face challenges in accuracy due to low similarity between A and B images, leading to deteriorated focus detection accuracy and potential aliasing issues, especially when focus detection pixels are spaced far apart, resulting in incomplete high-frequency band acquisition.
Innovation Solution
A focus-detection device comprising first and second detecting units that compute phase differences between image signals from different partial and entire regions of the exit pupil, with shifting mechanisms to enhance accuracy, and a computing unit that evaluates defocus amounts using these phase differences, while also assessing reliability based on image signal characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If focus detection pixels are disposed at a large distance, then the device complexity is reduced, but the measurement precision deteriorates due to aliasing errors and inability to acquire high-frequency band components
Solution Approach 1:
The exit pupil is divided into multiple partial regions, and separate photoelectric conversion portions are provided for each partial region within the same pixel. This segmentation allows the pixel to capture light from different pupil regions simultaneously, enabling phase difference detection without requiring spatially separated pixels, thus maintaining measurement precision while reducing device complexity.
Solution Approach 2:
Instead of separating focus detection functions across different spatial positions (one-dimensional arrangement), the invention utilizes the exit pupil plane as an additional dimension. By providing multiple photoelectric conversion portions within the same pixel that correspond to different partial regions of the exit pupil, the system transforms the spatial separation problem into a pupil-region separation problem, resolving the contradiction between pixel distance and detection accuracy.
2Ease of manufacture
If focus detection pixels are used, then the manufacturing cost is reduced compared to dividing each pixel's photoelectric conversion portion, but the measurement precision deteriorates due to low similarity between A and B images
Solution Approach 1:
Each focus detection pixel is segmented into multiple photoelectric conversion portions, each receiving light from a different partial region of the exit pupil. This segmentation within pixels allows generation of multiple image signals (A image, B image, etc.) from the same pixel location, ensuring high similarity between comparison images while maintaining manufacturing simplicity of using dedicated focus detection pixels.
Solution Approach 2:
The focus detection pixels serve multiple functions: they generate both A images and B images (or more) by utilizing different photoelectric conversion portions within the same pixel. This multi-functionality allows the system to perform phase difference detection with high accuracy without requiring separate pixel groups for A and B images, thereby maintaining manufacturing ease while improving measurement precision.
3Device complexity
If focus detection pixels are disposed at a large distance, then the device structure is simplified, but the measurement precision deteriorates due to aliasing occurring differently between A and B images
Solution Approach 1:
The invention segments the photoelectric conversion function within each pixel into multiple portions, each associated with a different partial region of the exit pupil. This segmentation ensures that A images and B images are generated from the same pixel location but different pupil regions, eliminating differential aliasing errors while simplifying the overall pixel arrangement structure.
Solution Approach 2:
Multiple photoelectric conversion portions within the same pixel create copies of the imaging function for different pupil regions. These copies (A image, B image) are generated from identical pixel positions, ensuring consistent sampling characteristics and preventing differential aliasing, while the overall device structure remains simplified.
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
Improves the accuracy of phase-difference detection type focus detection by effectively computing defocus amounts and reducing noise influence, allowing for more precise focus adjustment and higher image quality even with low similarity between A and B images.
Implementation Method 1
a photoelectric conversion portion of each pixel has two divided areas that receive, via the microlens, light beams having passed through different regions of an exit pupil of a photographic lens
Data Source
AI summary
Disclosed is a focus-detection device capable of performing phase-difference detection type focus detection using outputs of an image sensor, and a method for controlling the same. Phase differences between image signals each of which based on a light beam that has passed through different partial regions of an exit pupil of an imaging optical system, and an image signal based on a light beam that has passed through the entire region of the exit pupil is detected. Then, a defocus amount of the imaging optical system is computed using the sum of the phase differences.