Dynamic Focus Detection Area Division for Phase Difference Autofocus
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Solution Overview
Problem
Existing autofocus systems using on-imaging plane phase difference detection methods face challenges in reducing calculation periods, especially during subject tracking or prediction, leading to inefficiencies in high-accuracy focus detection.
Innovation Solution
A focus detection apparatus that divides focus detection areas into smaller divisions based on subject movement or size changes, adjusting the number of focus detection areas and correlation calculation ranges to enhance sampling frequency and reduce calculation time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If focus detection signals are added in time and space directions to suppress noise, then measurement precision is improved, but calculation period increases
Solution Approach 1:
The image sensor is divided into multiple focus detection pixel regions, each with independent photoelectric conversion units. This segmentation allows parallel processing of focus detection signals from different regions, reducing the total calculation period while maintaining measurement precision through spatial diversity.
Solution Approach 2:
The patent dynamically adjusts the number of frames of focus detection signals to be added based on subject movement detection. When subject movement is detected, the system reduces the number of addition operations to shorten calculation period; when no movement is detected, it increases addition operations to improve measurement precision.
2Reliability
If subject tracking or prediction is performed with high sampling frequency, then reliability of tracking is improved, but calculation period increases
Solution Approach 1:
The system dynamically adjusts sampling frequency based on subject movement state. When movement is detected, sampling frequency is increased to improve tracking reliability; when stationary, frequency is reduced to minimize calculation period. This dynamic adaptation resolves the contradiction between tracking reliability and calculation efficiency.
Solution Approach 2:
The patent changes the parameter of frame addition count based on detection results. By adjusting this parameter dynamically, the system optimizes the balance between tracking reliability (requiring more samples) and calculation period (requiring fewer samples), achieving both goals under different operating conditions.
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
This approach improves subject tracking performance by accelerating focus detection calculations, allowing for more accurate and timely autofocus adjustments, especially when dealing with moving subjects.
Implementation Method 1
each focus detection pixel having a first photoelectric portion and a second photoelectric portion that share one microlens and receive light beams passing through different pupil regions
Data Source
AI summary
A focus detection apparatus that performs phase difference focus detection using signals output from focus detection pixels each having first and second photoelectric portions that share one microlens, comprises: a setting unit that sets a focus detection area; a detection unit that detects whether a position and/or a size of a subject in an image has changed; a division unit that divides the focus detection area into a plurality of divisional areas by a divisor that is smaller when the detection result yields true than when it yields false; and a focus detection unit that adds signals respectively for the first and second photoelectric portions included in each divisional area in the divisional direction and obtains correlation amounts between the added signals, and adds the obtained correlation amounts for each focus detection area, then performs the focus detection.