Auto Focusing Apparatus Stability Control
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Solution Overview
Problem
Existing autofocus systems in video cameras often fail to stabilize focus on a person, especially when the subject is moving or camera shake occurs, leading to frequent alternation between face recognition and failure, resulting in unstable focusing control.
Innovation Solution
An auto focusing apparatus and method that periodically detects a subject, sets a first frame corresponding to the detected subject and a second frame, and exercises focusing control based on the frequency of detection, using a focus signal from either frame to maintain stable focusing, even when face recognition is unreliable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If face recognition is constantly performed to focus on recognized faces, then focusing accuracy on the main subject is improved, but focusing stability deteriorates when face recognition fails frequently due to camera shake or subject movement
Solution Approach 1:
The patent dynamically switches between two focusing modes: when face recognition is successful, it uses face-based focusing control for high accuracy; when face recognition fails or alternates frequently, it transitions to fixed-position focusing control for stability. This dynamic adaptation resolves the contradiction by selecting the appropriate focusing strategy based on real-time recognition reliability.
Solution Approach 2:
The system changes the parameter of focus detection area selection based on face recognition results. It monitors the frequency of face recognition success and adjusts the focusing control parameter accordingly - using recognized face positions when recognition is stable, and falling back to fixed positions when recognition becomes unreliable, thus maintaining both accuracy and stability.
2Reliability
If focus detection area is constantly set to recognized face position, then focusing on main person is improved, but focusing reliability deteriorates when face recognition alternates frequently between success and failure
Solution Approach 1:
The patent performs preliminary evaluation of face recognition stability by monitoring the frequency of successful recognition over time. Before committing to face-based focusing control, it assesses whether the recognition is stable enough to be reliable, and only then proceeds with face-position-based focusing, preventing unreliable focusing decisions.
Solution Approach 2:
The system continuously monitors face recognition results and uses this feedback to adjust focusing control. When recognition alternates frequently, the feedback mechanism triggers a switch to fixed-position focusing, maintaining reliability by avoiding unstable face-tracking when conditions are unfavorable.
3Adaptability or versatility
If face recognition is performed periodically on moving subjects, then adaptability to subject movement is improved, but focusing stability deteriorates due to frequent recognition failures from camera shake or occlusion
Solution Approach 1:
The patent implements dynamic focusing control that adapts to subject movement by switching between face-tracking mode (when recognition is successful) and fixed-position mode (when recognition fails). This dynamic approach maintains adaptability to movement while ensuring stability during recognition failures caused by camera shake or occlusion.
Solution Approach 2:
The system prepares for potential recognition failures by having a fallback fixed-position focusing mode ready. When face recognition becomes unreliable due to movement or occlusion, the system seamlessly transitions to the pre-prepared fixed-position mode, cushioning against the instability that would otherwise occur during recognition failures.
Data Source
AI summary
When a face is detected from image signals, stability determination time is set for determining if the face is recognized in a stable manner, and a period of time for which the face is consecutively detected starts to be measured. Until the measured period of time exceeds the stability determination time, an AF evaluation value acquired from a normal frame set to include a face frame corresponding to the face is used to exercise TV-AF control. Once the measured time exceeds the stability determination time, TV-AF control is exercised based on AF evaluation values acquired from each of the face frame and the normal frame.