Focus Lens Blur Detection for Stable Tracking
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Solution Overview
Problem
Existing image capture apparatuses face challenges in maintaining stable focus tracking due to image blur, which affects autofocus evaluation values, leading to unstable focus position identification and tracking, especially during camera shake or panning.
Innovation Solution
An image capture apparatus and method that includes a blur detection unit to determine if the blur amount is above a threshold, triggering the use of a first focus detection method involving reciprocating motion of the focus lens, while avoiding the second method that relies on changes in autofocus evaluation values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the second focus detection method (hill-climbing operation) is used to identify focus position based on AF evaluation value changes, then focus tracking speed is improved, but measurement precision deteriorates due to image blur affecting AF evaluation values
Solution Approach 1:
The patent dynamically switches between the first focus detection method (minute-driving operation) and the second focus detection method (hill-climbing operation) based on the detected image blur amount. When image blur exceeds a threshold, the system selects the first method which is less sensitive to blur; when blur is within tolerance, it selects the second method for faster tracking. This dynamic selection resolves the contradiction by adapting the focus detection approach to current imaging conditions.
2Measurement precision
If the minute-driving operation is used to identify focus position, then measurement precision is improved, but productivity deteriorates due to increased operation time
Solution Approach 1:
The system dynamically adjusts the focus detection method based on image blur conditions. When image blur is detected beyond a threshold, the patent selects the minute-driving operation (first method) which provides more precise focus identification despite taking longer. When blur is minimal, it switches to the hill-climbing operation (second method) for faster tracking. This dynamic adaptation resolves the contradiction between precision and efficiency.
3Adaptability or versatility
If AF control is performed during image blur, then adaptability is improved, but reliability deteriorates due to unstable focus position identification
Solution Approach 1:
The patent implements a dynamic selection mechanism that monitors image blur amount and switches between focus detection methods accordingly. When blur exceeds a threshold, the system selects the first focus detection method (minute-driving operation) which is less sensitive to blur-induced AF evaluation value changes, thereby maintaining reliable focus tracking during blur conditions while preserving AF operation continuity.
Solution Approach 2:
The system continuously monitors image blur amount and uses this feedback to dynamically adjust the focus detection method. The blur detection unit provides real-time feedback about imaging conditions, enabling the control unit to select the appropriate focus detection method (first or second) to maintain reliable and stable focus position identification under varying blur conditions.
Data Source
AI summary
Provided is an image capture apparatus that can perform focus detection based on a focus evaluation value indicating contrast of a subject image included in a focus detection area using an image signal output from an image sensor. In accordance with the extent of a blur amount of the subject image, the image capture apparatus determines how to use a method for performing focus detection through a reciprocating motion of a focus lens and a method for performing focus detection by moving the focus lens in a direction toward which the focus evaluation value increases. Focus detection is performed based on the determination.