Focus Adjusting Apparatus Using Rate of Change and Image Size
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Solution Overview
Problem
Conventional focus adjustment methods in cameras often result in unnecessary AF restarts during moving-image shooting or continuous AF operations, leading to blurred images and excessive power consumption due to incorrect determination of subject distance changes.
Innovation Solution
A focus adjusting apparatus and method that control focus adjustment based on the rate of change in focus evaluation value and the state of the image size, using a calculation unit to determine a restart determination value and adjust the focus accordingly, reducing unnecessary AF operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If focus adjustment is performed continuously during moving-image shooting or continuous AF operation, then focus tracking capability is improved, but power consumption increases and unnecessary AF restarts occur
Solution Approach 1:
The patent applies dynamics by making the AF operation mode adjustable and adaptive. The system can switch between continuous AF operation and single-shot AF based on shooting conditions and user preferences. The focus adjustment is performed dynamically only when necessary (when subject distance actually changes), rather than continuously, thereby reducing power consumption while maintaining reliable focus tracking when needed.
Solution Approach 2:
The patent changes the parameter of AF operation frequency and timing based on detected subject distance changes. By monitoring whether the subject has moved beyond a predetermined distance threshold, the system adjusts the AF operation parameters to perform focus adjustment only when necessary, rather than continuously. This parameter adaptation reduces unnecessary AF operations and power consumption while maintaining focus reliability.
2Speed
If AF restart is triggered by focus evaluation value change, then focus adjustment responsiveness is improved, but false AF restarts occur when subject distance has not changed
Solution Approach 1:
The patent introduces an intermediary verification mechanism (subject distance detection) between the focus evaluation value change and the AF restart decision. Instead of directly triggering AF restart based solely on focus evaluation value changes, the system first verifies whether the subject distance has actually changed beyond a predetermined threshold. This intermediary check prevents false AF restarts caused by focus evaluation fluctuations when the subject distance remains constant.
Solution Approach 2:
The patent implements feedback by continuously monitoring subject distance and using this information to validate whether AF restart should be triggered. The system feeds back the subject distance detection result to the AF control logic, which then decides whether to initiate AF restart. This feedback mechanism ensures that AF restart occurs only when there is a genuine subject distance change, improving measurement precision while maintaining responsiveness.
3Measurement precision
If multiple AF operations are performed frequently, then focus accuracy is improved, but image quality deteriorates due to blurred images during adjustment
Solution Approach 1:
The patent applies preliminary action by performing subject distance detection and verification before initiating AF operations. The system checks whether the subject distance has changed beyond a predetermined threshold before starting focus adjustment. This preliminary verification ensures that AF operations are only performed when necessary, preventing unnecessary focus adjustments that would cause blurred images during the adjustment process, thereby maintaining image quality while achieving focus accuracy when needed.
Data Source
AI summary
A focus adjusting apparatus includes an imaging unit, a calculation unit, a detection unit, and a control unit. The imaging unit is configured to generate an imaging signal of an image formed by an optical system. The calculation unit is configured to calculate based on the imaging signal a focus evaluation value in accordance with a focus adjustment position of the optical system. The detection unit is configured to detect a state with respect to a size of the image. The control unit is configured to control focus adjustment of the optical system based on a rate of change in the focus evaluation value and the state with respect to the size of the image.