Image Pickup Apparatus Defocus Calculation Visual Field Center Stability
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Solution Overview
Problem
Existing image pickup apparatuses using phase difference detection methods struggle to accurately calculate defocus amounts, particularly for three-dimensional object images, due to limitations in three-point interpolation methods.
Innovation Solution
The apparatus includes an image pickup unit receiving light from different pupil regions and a calculation unit that adjusts the size of the image signal shift range to maintain the visual field center's position relative to the target pixel, ensuring accurate defocus calculation through correlation function analysis using methods like SAD or NCC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If three-point interpolation method is used to calculate defocus amount, then calculation speed is improved, but measurement precision deteriorates for three-dimensional object images
Solution Approach 1:
The patent changes the parameter of the predetermined range size in the correlation function calculation. By adjusting the range size based on shift amount, the calculation maintains accuracy for three-dimensional objects while preserving computational efficiency. This parameter adaptation resolves the contradiction between fast calculation and precise measurement.
2Device complexity
If fixed predetermined range is used in correlation function calculation, then device complexity is reduced, but measurement precision deteriorates due to visual field center variation
Solution Approach 1:
The patent introduces dynamic adjustment of the predetermined range size based on the shift amount between image signals. This dynamic parameter changes with operating conditions to maintain the visual field center position, achieving high measurement precision without excessive device complexity through adaptive rather than fixed parameters.
3Measurement precision
If predetermined range size is increased to maintain visual field center stability, then measurement precision is improved, but calculation time increases
Solution Approach 1:
The predetermined range size is dynamically adjusted based on shift amount rather than being uniformly large. This allows the calculation to use only the necessary number of pixels required to maintain visual field center stability, avoiding unnecessary computational overhead and reducing calculation time while preserving measurement precision.
Data Source
AI summary
An image pickup apparatus includes an image pickup unit configured to receive an incident light beam from regions of a pupil of an optical system different from each other to output a first image signal and a second image signal, and a calculation unit configured to calculate an evaluation value while relatively shifting the first and second image signals from pixels included in a predetermined range to calculate a defocus amount, and the calculation unit is configured to change a size of the predetermined range so that a center of a visual field range relative to a position of a target pixel does not vary depending on a shift amount between the first and second image signals.