Autofocus Calculation Device Dynamic Area Adjustment
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Solution Overview
Problem
Existing phase difference autofocus methods in image pickup devices face challenges in setting a sufficient focus detection area for small faces, leading to decreased accuracy and issues with near and far objects entering the focus detection area, and fail to consider the optimal ratio of enlargement for the focus detection area.
Innovation Solution
A calculation device that calculates a defocus amount using a parallax image signal, comprising a calculation unit to acquire and composite correlation signals, and a detection unit to adjust the focus detection area based on the object's size and contrast, optimizing the focus detection area by varying the luminance and correlation addition numbers based on the detected face or body size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the focus detection area is set to a small face, then the focus detection can be performed on the face, but the focus detection area becomes insufficient in size leading to decreased accuracy
Solution Approach 1:
The focus detection area is dynamically adjusted based on the detected object size. When a small face is detected, the system enlarges the focus detection area to a predetermined size to ensure sufficient signal composite amount for accurate focus detection, rather than keeping it fixed to the small face boundaries.
Solution Approach 2:
The system changes the parameter of focus detection area size based on the detected object characteristics. When the object (face) size is small, the focus detection area is enlarged to maintain an adequate number of pixels for correlation calculation, thereby preserving measurement precision.
2Measurement precision
If the focus detection area is made large to increase accuracy, then the focus detection accuracy is improved, but near and far objects enter the focus detection area causing focus detection errors
Solution Approach 1:
The system applies local quality by making the focus detection area characteristics dependent on the local object properties. When a small face is detected, the area is selectively enlarged only in that local region, allowing the area size to be adapted to the specific object rather than applying a uniform large area that would include unwanted near and far objects.
Solution Approach 2:
The focus detection area is dynamically adjusted based on the detected object size. When a small face is detected, the system enlarges the focus detection area to a predetermined size to ensure sufficient signal composite amount for accurate focus detection, rather than keeping it fixed to the small face boundaries.
3Reliability
If line addition is performed based on brightness threshold, then noise influence is decreased, but the focus detection area cannot be optimally set for small faces
Solution Approach 1:
The system changes the parameter of focus detection area size based on the detected object characteristics. When the object (face) size is small, the focus detection area is enlarged to maintain an adequate number of pixels for correlation calculation, thereby preserving measurement precision while maintaining the brightness-based line addition for noise suppression.
Data Source
AI summary
Highly accurate focus adjustment device can be provided, for example, that includes a focus detection area setting unit that sets a focus detection area to a position of a face detected in an image pickup field angle, and sets a luminance addition number and a correlation addition number in the focus detection area according to a size of the face, and performs focus detection for the face, thereby to suppress a decrease in accuracy.