Imaging Apparatus Phase Difference Auto-Focus Monotonic Control
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Solution Overview
Problem
In imaging apparatuses, the image-plane phase difference method for auto-focus faces challenges with long focal length lenses, where the small phase difference information makes it difficult to accurately calculate defocus amounts, leading to slower and lower quality focus acquisition, and frequent switching to contrast detection methods increases time and decreases quality.
Innovation Solution
An imaging apparatus with both image output and phase difference detection pixels, utilizing a control unit to generate focus state change information based on phase difference information, continuing phase difference focus control for monotonic changes and switching to alternative methods when changes are not monotonic, allowing for high-speed and high-quality auto-focus operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If image-plane phase difference focus control is used with long focal length lenses, then focus control speed is improved, but measurement precision of defocus amount deteriorates due to small phase difference information
Solution Approach 1:
The patent introduces an exit pupil region separation mechanism as an intermediary to enhance phase difference information. By separating the exit pupil region into first and second regions and directing light from each region to different pixel groups, the system amplifies the phase difference signal that would otherwise be too small to measure accurately with long focal length lenses, thus resolving the contradiction between speed and measurement precision.
Solution Approach 2:
The patent segments the exit pupil region into multiple regions (first exit pupil region and second exit pupil region) and corresponds each region to different pixel groups. This segmentation allows the system to capture and process phase difference information from spatially separated light paths, improving the measurability of defocus amounts while maintaining fast focus control speed.
2Measurement precision
If switching to contrast detection method is performed frequently, then focus accuracy is improved, but time to achieve in-focus state increases and quality decreases
Solution Approach 1:
The patent implements a feedback mechanism where the control unit continuously monitors phase difference information and determines whether to switch between image-plane phase difference focus control and contrast detection focus control based on real-time focus state assessment. This feedback-driven switching strategy optimizes the balance between speed and accuracy, avoiding unnecessary switches to contrast detection method while ensuring focus accuracy is maintained.
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 enables faster and more accurate auto-focus operations by determining monotonic focus state changes and adapting control methods, reducing the need for frequent method switching and improving overall focus quality.
Implementation Method 1
a defocus amount is calculated on the basis of a phase shift of two phase-difference images obtained by receiving, with a phase difference detection pixel provided on an imaging surface, a luminous flux that has passed through mutually different exit pupil regions
Data Source
AI summary
An imaging unit is configured with use of an imaging element including an image output pixel and a phase difference detection pixel. A control unit performs focus control based on image-plane phase difference information obtained using the phase difference detection pixel over a predetermined period, generates focus state change information indicating whether or not a change in a focus state is a monotonous change, and continues the focus control based on the image-plane phase difference information on the assumption of a large blur state in a case where the focus state change information indicates that a change in the focus state is a monotonous change. The control unit switches from the image-plane phase difference auto-focus operation to an auto-focus operation in a case where a change in the focus state is not a monotonous change. Thus, it becomes possible to perform a high-speed and high-quality auto-focus operation.