Focus Detection Unit Spatial Frequency Band Selection
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Solution Overview
Problem
Phase difference autofocus methods face challenges in correcting focus detection errors caused by aberration, especially with soft-focus lenses, which result in inaccurate focus detection and increased processing load, and existing solutions fail to effectively address these issues.
Innovation Solution
An image pickup apparatus with a pair of focus detection pixels and a processor that detects focus using signals from these pixels, capable of adjusting aberration and providing correction information to improve focus detection accuracy across various spatial frequency bands, and a detachable lens apparatus that communicates with the camera to adjust aberration based on user input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a soft-focus lens with large aberration is used, then images with soft focus effect can be obtained, but focus detection accuracy deteriorates due to large focus detection errors
Solution Approach 1:
The system changes the parameter of spatial frequency band selection based on the aberration amount. When aberration is large, it selects lower spatial frequency bands where focus detection is less affected by aberration. This dynamic parameter adjustment resolves the contradiction by adapting the detection method to the optical conditions.
Solution Approach 2:
The focus detection unit dynamically selects from multiple spatial frequency bands based on the detected aberration amount. This dynamic adaptation allows the system to maintain accurate focus detection despite varying aberration levels, particularly when using soft-focus lenses.
2Measurement precision
If focus detection is performed in high spatial frequency bands, then fine detail focus accuracy is improved, but detection becomes more sensitive to aberration errors
Solution Approach 1:
The system adjusts the spatial frequency band parameter based on aberration conditions. When aberration is detected to be large, it automatically selects lower spatial frequency bands that are more reliable under those conditions, thus maintaining detection stability.
Solution Approach 2:
The focus detection unit uses feedback from aberration amount detection to dynamically adjust which spatial frequency band is used for focus detection. This feedback mechanism ensures that the most reliable frequency band is selected based on current optical conditions.
3Adaptability or versatility
If multiple images at different in-focus degrees are captured to achieve desired soft focus, then soft focus images can be generated, but processing load increases
Solution Approach 1:
The system extracts only the necessary information (focus detection amount in appropriate spatial frequency bands) needed to determine soft focus characteristics, rather than processing multiple complete images. This reduces processing load while maintaining the ability to generate desired soft focus effects.
Solution Approach 2:
Instead of capturing multiple actual images at different focus degrees, the system uses focus detection data to create a representative measure of soft focus, effectively copying the essential information needed without the full processing burden of multiple images.
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 enables accurate focus detection even with large aberrations and allows for the generation of images with a desired degree of soft focus, reducing processing load and improving user selection options for soft focus images.
Implementation Method 1
an image sensor including a pair of focus detection pixels configured to receive light beams that have passed through different areas in an exit pupil of an imaging optical system
Data Source
AI summary
An image pickup apparatus includes an image sensor including a pair of focus detection pixels configured to receive light beams that have passed through different areas in an exit pupil of an imaging optical system, and at least one processor caused to function as a focus detection unit configured to detect focus of the imaging optical system by using a pair of focus detection signals which is generated by using output signals from the pair of focus detection pixels. The focus detection unit can detect the focus in a plurality of spatial frequency bands. The focus detection unit acquires a focus detection result to be used in a spatial frequency band corresponding to an aberration amount of the imaging optical system, the spatial frequency band being included in the plurality of spatial frequency bands.