Adaptive Autofocus Range Control for Moving Face Tracking
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Solution Overview
Problem
Existing imaging apparatuses face challenges in stabilizing focus control when a face target is moving, leading to significant changes in estimated subject distance and excessive movement of the focus lens, resulting in unstable focus control and potential false detection.
Innovation Solution
An imaging apparatus with object information holding, imaging, object detecting, object-autofocus-range calculating, and autofocus control means to determine and adjust the focus lens movement range based on the detected object size and position, using a detection frame and cancel conditions to ensure stable focus control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the focus lens movement range is adjusted based on detected face position and size, then focus control speed is improved, but focus stability deteriorates when the subject is moving
Solution Approach 1:
The patent applies dynamics by making the focus lens movement range adaptive rather than fixed. The range is dynamically adjusted based on the detected face position and size, allowing the system to optimize between speed and stability depending on the subject's state. When the face is stationary, a narrower range provides stable focus, while the system can expand the range when needed for tracking moving subjects.
Solution Approach 2:
The patent changes the parameter of focus lens movement range based on detected face characteristics. By calculating the face position and size from the captured image, the system adjusts the movement range parameters to match the subject's scale and position, enabling faster focus acquisition while maintaining stability through context-aware parameter selection.
2Adaptability or versatility
If the focus lens moves significantly to track a moving face, then focus tracking capability is improved, but lens shaking increases causing unstable focus detection
Solution Approach 1:
The system dynamically adjusts the focus lens movement range based on the detected face position and size. This dynamic adaptation allows the lens to track moving faces effectively while preventing excessive movement that would cause shaking. The movement range is calculated to be sufficient for tracking but constrained enough to maintain stability.
Solution Approach 2:
The patent performs preliminary detection of face position and size before executing focus lens movement. By calculating the appropriate movement range in advance based on the detected face characteristics, the system prepares the optimal tracking parameters before the actual focus adjustment, enabling smooth and stable tracking without sudden large movements.
3Measurement precision
If the subject distance estimation changes significantly due to false face detection, then object detection sensitivity is improved, but false detection occurrence increases
Solution Approach 1:
The system uses feedback by continuously monitoring the detected face position and size to adjust the focus lens movement range. This feedback mechanism allows the system to verify detections and adjust parameters accordingly, reducing the impact of false detections. When a false detection occurs, the feedback loop can detect inconsistencies and prevent significant distance estimation changes.
Solution Approach 2:
The patent performs preliminary verification of face detection by calculating the face position and size before using these values for subject distance estimation. This preliminary action allows the system to filter out obvious false detections and ensure that only valid face detections are used for focus control, improving detection reliability.
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
Enables stable focus control on a predetermined object by calculating and adjusting the focus lens movement range, reducing false detection and lens shaking, and maintaining accurate focus tracking even with moving subjects.
Implementation Method 1
imaging means for converting incident light from the subject to a captured image
Data Source
AI summary
An imaging apparatus includes an object information holding unit to hold a size of a predetermined object included in a subject; an imaging unit to convert incident light from the subject to a captured image; an object detecting unit to detect the object included in the captured image and a size of an object image; an object-autofocus-range calculating unit to calculate an object-autofocus-range that is a limited movement range of a focus lens; a use determination range calculating unit to calculate a use determination range that is a range to determine whether detection of an in-focus position of the detected object is to be performed in the object-autofocus-range and that includes the object-autofocus-range; and an autofocus control unit to detect the in-focus position by setting the object-autofocus-range and moving the focus lens in the object-autofocus-range if a current position of the focus lens is within the use determination range.