Autofocus Control Switching Phase Contrast Detection for Tracking Accuracy
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Solution Overview
Problem
During moving image capture or continuous shooting, the phase detection AF method is often used to improve trackability of the focus position, but this can result in reduced focusing accuracy compared to contrast detection AF or hybrid AF methods.
Innovation Solution
An image capturing device and method that combines phase detection AF and contrast detection AF, using detection pixels to receive light through different regions of the imaging optical system, with a focusing control unit to drive optical members to a detected focusing position, and a second detection unit to monitor subject image changes, switching between methods based on stability of the scene to maintain trackability and improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If phase detection AF method is used to improve trackability of focus position, then focusing speed is improved, but focusing accuracy deteriorates
Solution Approach 1:
The patent dynamically switches between phase detection AF and contrast detection AF methods based on scene stability. When the scene is stable (low movement), contrast detection AF is used for high accuracy. When the scene is unstable (high movement), phase detection AF is used for fast tracking. This dynamic adaptation resolves the contradiction by selecting the appropriate method based on real-time conditions.
Solution Approach 2:
The patent changes the parameter of focus detection method based on scene stability evaluation. By monitoring scene stability and switching between two different AF methods, the system optimizes both speed and accuracy according to the current shooting conditions, resolving the inherent trade-off between the two methods.
2Measurement precision
If contrast detection AF method is used to improve focusing accuracy, then measurement precision is improved, but focusing time increases
Solution Approach 1:
The system dynamically selects the focus detection method based on scene stability. Contrast detection AF is applied only when the scene is stable, minimizing time loss while maximizing accuracy when conditions permit. This resolves the contradiction by avoiding unnecessary time expenditure on contrast detection when the scene is moving.
Solution Approach 2:
The patent changes the detection method parameter based on scene stability evaluation. By switching between phase detection and contrast detection methods, the system achieves high accuracy when needed (stable scenes) while maintaining speed when necessary (unstable scenes), resolving the time-accuracy trade-off.
3Adaptability or versatility
If phase detection AF method is used for moving image capture, then trackability is improved, but focusing accuracy deteriorates
Solution Approach 1:
The patent implements dynamic method selection based on scene stability detection. When shooting moving images with unstable scenes, phase detection AF provides good trackability. When the scene stabilizes, contrast detection AF is activated to improve focusing accuracy. This dynamic switching resolves the contradiction between trackability and accuracy.
Solution Approach 2:
The system changes the focus detection parameter (method selection) based on scene stability. By evaluating scene stability and switching between phase detection and contrast detection methods, the system achieves both good trackability during movement and high accuracy during stable periods, resolving the contradiction.
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
The solution enhances both the trackability and focusing accuracy of the image capturing device by dynamically switching between phase detection AF and contrast detection AF based on scene stability, optimizing focus positioning during moving image capture.
Implementation Method 1
an imaging element having a light receiving surface including detection pixels that receive light passed through different regions of an exit pupil of an imaging optical system, and detect a phase difference between two images obtained by splitting the exit pupil
Implementation Method 2
a contrast evaluation value for evaluating a contrast of an image taken by an image sensor is obtained while AF scanning operation is being performed. Then, a lens position of an imaging optical system at which the contrast evaluation value is the largest is detected as a focusing position
Data Source
AI summary
[Object] To improve both trackability of a focus position and focusing accuracy with respect to a subject. [Solution] An image capturing device includes: an imaging element having a light receiving surface including detection pixels that receive light passed through different regions of an exit pupil of an imaging optical system, and detect a phase difference between two images obtained by splitting the exit pupil; a first detection unit configured to execute at least any of first focus detection based on a phase detection autofocus (AF) method and second focus detection based on a contrast detection AF method; a focusing control unit configured to drive at least one optical member included in the imaging optical system toward a focusing position detected by the focus detection; and a second detection unit configured to detect a change in a subject image. In a case where a state in which a change amount of the subject image is less than a threshold continues for a predetermined period of time or more after the first focus detection, the first detection unit executes the first focus detection or the second focus detection.