Autofocus Prediction Unit for Rapid Motion Tracking
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Solution Overview
Problem
Existing autofocus systems struggle to maintain focus on rapidly moving objects, especially when their motion characteristics change suddenly, such as during rapid movements or changes in direction, leading to difficulties in tracking subjects like figure skaters.
Innovation Solution
An image capture apparatus with a focus detection unit, prediction unit, and control unit that predicts the focus position of an object based on past outputs and adjusts focus by detecting shifts on the image sensing plane using both phase difference AF sensors and photometric data, switching prediction methods when motion exceeds a threshold to maintain accurate focus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If focus detection is performed using conventional methods on rapidly moving objects, then focus detection can be performed, but the focus detection becomes inaccurate when motion characteristics change rapidly
Solution Approach 1:
The patent applies dynamics by making the focus detection system adaptive to changing motion characteristics. The control unit dynamically adjusts the focus detection range and prediction methods based on detected motion patterns. When rapid motion or direction changes are detected, the system switches to different prediction models and adjusts the search range accordingly, allowing the system to maintain accuracy despite changing conditions.
Solution Approach 2:
The patent changes key parameters of the focus detection system based on motion characteristics. The control unit modifies the focus detection range, prediction time horizon, and selection criteria for focus detection regions according to the detected motion velocity and direction changes. This parameter adaptation enables the system to handle rapidly moving objects effectively.
2Adaptability or versatility
If the focus detection range is fixed, then the system is simple to control, but the system cannot adapt to rapid motion changes of the object
Solution Approach 1:
The focus detection range is made dynamic rather than fixed. The control unit automatically adjusts the search range based on the detected motion characteristics of the object. When rapid motion is detected, the system expands the search range or adjusts it according to the motion vector, allowing the system to track the object effectively without requiring complex manual control.
Solution Approach 2:
The system performs self-adjustment based on its own detection results. The control unit uses the motion detection output to automatically modify the focus detection parameters without external intervention. This self-service mechanism reduces the need for complex control structures while maintaining adaptability.
3Measurement precision
If prediction is based on long elapsed time, then prediction stability is improved, but prediction accuracy decreases when motion velocity changes rapidly
Solution Approach 1:
The prediction time horizon is made dynamic. The control unit adjusts the prediction elapsed time based on the detected motion velocity. When the object moves rapidly, the system uses shorter prediction intervals to respond quickly to motion changes. When motion is slow or stable, the system uses longer prediction intervals to maintain stability. This dynamic adjustment resolves the contradiction between accuracy and response time.
Solution Approach 2:
The prediction parameter (elapsed time) is changed based on motion conditions. The control unit modifies the prediction time horizon according to the detected motion characteristics, switching between different prediction strategies. This parameter change enables the system to optimize both accuracy and responsiveness under different motion conditions.
Data Source
AI summary
An image capture apparatus which captures an object image formed by an imaging lens, comprises a focus detection unit which detects a focus position of the object image at a plurality of positions on an image sensing plane, a prediction unit which stores the past output from the focus detection unit, and predicts a locus of the focus position of the object image based on the stored output, thereby predicting the focus position of the object image at a predetermined time instant, a detection unit which detects a shift of the object image on the image sensing plane, and a control unit which changes the output from the prediction unit based on the output from the detection unit.