Focus Detection Device Using Pupil Eccentricity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The accuracy of image plane-based phase-detection AF in image sensors is affected by manufacturing errors, leading to suboptimal focus detection signals.
Innovation Solution
A focus detection device and method that generate first and second focus detection signals from an image sensor, calculate a shift amount between these signals, and convert it into a defocus amount using a conversion coefficient based on pupil eccentricity and incident pupil distance, which are dependent on the image height at the focus detection position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If image plane-based phase-detection AF is used for focus detection, then focus detection capability is enabled, but manufacturing errors in the image sensor reduce the accuracy of focus detection signals
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the conversion coefficient based on image height. The conversion coefficient, which converts shift amount to defocus amount, is modified according to the specific image height position, thereby compensating for manufacturing variations in the image sensor and improving focus detection accuracy across different field positions.
Solution Approach 2:
The patent implements local quality by applying different conversion coefficients to different image height positions. Instead of using a uniform conversion coefficient for the entire image sensor, the system tailors the conversion parameter to each local region (image height), accounting for local manufacturing variations and optical path differences.
2Measurement precision
If a uniform conversion coefficient is used for focus detection across the entire image sensor, then the device complexity is reduced, but the accuracy of focus detection varies with image height due to manufacturing errors
Solution Approach 1:
The patent changes the conversion coefficient parameter based on image height position. By making the conversion coefficient a variable parameter rather than a fixed value, the system achieves accurate focus detection across different image positions while maintaining a relatively simple calculation framework that only requires selecting or computing the appropriate coefficient for the given image height.
3Measurement precision
If focus detection is performed without considering pupil eccentricity and incident pupil distance variations, then the calculation process is simplified, but the defocus amount calculation becomes inaccurate
Solution Approach 1:
The patent incorporates pupil eccentricity and incident pupil distance as variable parameters in the conversion coefficient calculation. These parameters change with image height, and by including them in the conversion coefficient determination, the system achieves accurate defocus amount calculation while keeping the overall process computationally efficient through pre-established relationships or lookup tables.
Data Source
AI summary
A focus detection device calculates a shift amount between a first focus detection signal and a second focus detection signal both generated based on a signal obtained from an image sensor. The device also calculates a conversion coefficient and applies the conversion coefficient to the shift amount to convert the shift amount into a defocus amount of an imaging optical system. The device calculates the conversion coefficient based on at least one of a pupil eccentricity amount and an incident pupil distance, both are dependent on an image height at a focus detection position.