Focus Adjustment Device Using Multiple Detection Regions
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Solution Overview
Problem
Existing autofocus systems face difficulties in accurately focusing on both near and far subjects within the same AF area, leading to instability and inaccuracies in image capture, especially when a far subject and a near subject are mixed.
Innovation Solution
A focus adjustment device and method that utilize multiple focus detection regions of varying sizes within the image sensor's field of view, with a control system that determines the movement direction of the focus lens based on contrast changes and performs minute vibrations to achieve precise focus adjustments, inhibiting transitions between focus adjustment operations when consistent direction differences are detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single focus detection region is used for autofocus, then the device complexity is low, but the measurement precision of focus direction is insufficient in far-and-near mixed subjects
Solution Approach 1:
The imaging region is divided into multiple focus detection regions (first focus detection region and second focus detection region) with different sizes. Each region independently evaluates focus direction, allowing the system to detect focus directions for both far and near subjects simultaneously, thereby improving measurement precision without requiring complex additional hardware
Solution Approach 2:
Different focus detection regions are assigned different evaluation weights based on their reliability. The system determines focus direction by comparing evaluation results from multiple regions, with each region contributing according to its local characteristics. This allows accurate focus detection in far-and-near mixed subjects while maintaining a relatively simple overall device structure
2Adaptability or versatility
If focus adjustment operation switches between different operations, then the adaptability to different focus scenarios is improved, but the stability of focus adjustment is reduced due to hunting and rapid focus shifts
Solution Approach 1:
The system continuously monitors the focus detection results and switches between first and second focus adjustment operations based on real-time feedback from the focus evaluation. When the determined focus direction changes, the system switches operations; when it remains consistent, the system maintains the current operation, thereby achieving both adaptability and stability through feedback-controlled operation switching
Solution Approach 2:
The focus adjustment system dynamically switches between different adjustment operations (first and second operations) based on the determined focus direction. This dynamic switching allows the system to adapt to different focus scenarios while maintaining stability by avoiding unnecessary operation changes when the focus direction is consistent
3Speed
If the focus lens is moved continuously to achieve focus, then the focus adjustment speed is high, but the image stability deteriorates due to rapid focus shifts and hunting
Solution Approach 1:
The system performs minute vibrations of the focus lens periodically to detect focus direction accurately. This periodic vibration approach allows the system to determine the correct focus direction before executing larger focus adjustments, thereby maintaining image stability while achieving fast focus adjustment when needed
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 enhances the stability and accuracy of autofocus operations, particularly in far-and-near mixed subjects, by maintaining focus without unnecessary lens movement, ensuring clear and stable moving images with reduced hunting or rapid focus shifts.
Implementation Method 1
a direction determination section which detects, regarding each of the focus detection regions, contrast of the image signal in the focus detection region, and determines a movement direction of the focus lens to be in focus on the basis of a change of the contrast caused by the movement of the focus lens
Implementation Method 2
a first focus adjustment operation to move the focus lens while minutely vibrating the focus lens to perform the focus adjustment
Data Source
AI summary
A focus adjustment device includes a focus detection region setting section, a direction determination section and control section. The focus detection region setting section sets focus detection regions which are different in size from one another. The direction determination section determines a movement direction of a focus lens to be in focus based on a change of the contrast caused by the movement of the focus lens. The control section repetitively determines whether determination results of the movement direction obtained in the respective focus detection regions are different. The control section inhibits a switchover of a focus adjustment operation when it is consecutively determined a predetermined number of times or more that the determination results of the movement direction are different, otherwise the control section does not inhibit the switchover.