Autofocus Control Unit for Stable Phase Difference Detection
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Solution Overview
Problem
Existing image capturing apparatuses face challenges in maintaining stable focus adjustment when the phase difference detection direction is switched, leading to potential sudden loss of focus, especially when dealing with subjects that have edges only in specific directions.
Innovation Solution
The image capturing apparatus includes a phase difference detection unit, a focus detection unit, an adjustment unit, and a control unit. The control unit ensures that focus adjustment based on the phase difference in the second direction is not performed until the reliability of the focusing state detected in the second direction exceeds a predetermined value, when transitioning from focus adjustment in the first direction to the second direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pupil division is performed in both horizontal and vertical directions to achieve highly accurate autofocus, then focus detection accuracy is improved, but processing time and power consumption increase due to reading all pixels without thinning
Solution Approach 1:
The patent segments the pixel array into first pixel regions with horizontal photoelectric conversion sections and second pixel regions with vertical photoelectric conversion sections. This allows independent processing of focus detection in different directions, enabling the system to read out only necessary pixels for each direction rather than all pixels, thus reducing processing time while maintaining accurate focus detection in both horizontal and vertical directions.
2Productivity
If thinning reading mode is used during standby state to suppress processing time and power consumption, then processing efficiency is improved, but focus detection reliability deteriorates when switching from AF control before photographing still image
Solution Approach 1:
The patent dynamically switches between different reading modes based on the operational state. During standby state, thinning reading mode is used to improve processing efficiency. When transitioning to AF control before photographing still image, the system switches to non-thinning reading mode to ensure reliable focus detection. This dynamic adaptation allows the system to optimize between processing efficiency and detection reliability based on contextual requirements.
Solution Approach 2:
The patent performs preliminary focus detection during standby state using the available photoelectric conversion sections before the actual photographing operation. By conducting AF control in advance and maintaining focus information, the system prepares for the upcoming still image photographing, ensuring that when the transition occurs, the focus state is already established and reliable focus detection can continue without interruption or loss of reliability.
3Adaptability or versatility
If phase difference detection direction is switched from horizontal to vertical during standby AF control, then adaptability to different subjects is improved, but focus stability deteriorates due to sudden loss of focus
Solution Approach 1:
The patent implements feedback mechanisms that monitor the reliability of focus detection results when switching between different photoelectric conversion sections. When transitioning from horizontal to vertical phase difference detection, the system evaluates the reliability of the detected focus state. If the reliability falls below a predetermined threshold, the system maintains the previous focus state or adjusts the transition timing, thereby preventing sudden loss of focus while still enabling adaptability to different subject orientations.
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 solution enables stable focus adjustment operations even when the phase difference detection direction is switched, preventing sudden loss of focus and maintaining accurate autofocus.
Implementation Method 1
pupil division is performed by one microlens and a pair of photoelectric conversion sections that are provided for each pixel of an image capturing element
Implementation Method 2
a pair of photoelectric conversion sections that are provided for each pixel of an image capturing element
Data Source
AI summary
An image capturing apparatus includes a phase difference detection unit configured to detect a phase differences in a first direction and in a second direction, a focus detection unit configured to detect a focusing state based on the phase differences in the first direction and in the second direction and acquire reliability of the focusing state, an adjustment unit configured to perform focus adjustment based on the focusing state, and a control unit configured to control not to perform the focus adjustment based on the second direction until the reliability of the focusing state in the second direction becomes higher than a predetermined value in a case of transitioning from a first state using the phase difference in the first direction to a second state using the phase difference in the second direction.