Imaging Apparatus Aperture Control for Focus Stability
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Solution Overview
Problem
Existing imaging apparatuses face issues where changing the aperture value from the focus detection value to the imaging aperture value can cause movement of the image plane, leading to an unfocused image capture, especially as the aperture value approaches the opening side.
Innovation Solution
An imaging apparatus that calculates and sets a closing side limit value for the aperture based on focus detection positions and exit pupil positions to prevent image plane movement, ensuring focus detection accuracy and maintaining image focus during aperture changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the aperture value is set to a smaller value (more opening side) than the predetermined aperture value during focus detection, then vignetting is prevented and focus detection accuracy is improved, but image plane movement occurs when changing to imaging aperture value, causing focus loss
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the aperture value during focus detection based on the detected focus position. The calculation unit determines an appropriate aperture value that balances vignetting prevention and image plane stability, and the control unit adjusts the aperture accordingly. This resolves the contradiction by making the aperture value a variable parameter rather than a fixed value, allowing optimization for each focus detection scenario.
Solution Approach 2:
The patent implements feedback by using the focus detection result to determine the appropriate aperture value for subsequent imaging. The system detects the focal state, calculates the suitable aperture value based on this detection, and adjusts the aperture before actual image capture. This feedback loop ensures that the aperture setting accounts for both vignetting prevention and image plane stability requirements.
2Adaptability or versatility
If the aperture value is changed from focus detection value to imaging aperture value, then imaging requirements are met, but image plane movement occurs leading to unfocused image capture
Solution Approach 1:
The patent applies preliminary action by performing focus detection at multiple focus detection positions before actual image capture. The system calculates the appropriate aperture value based on these preliminary detections and sets the aperture accordingly before the final imaging operation. This preliminary adjustment prevents image plane movement during the actual capture, resolving the contradiction between aperture adaptability and position stability.
Solution Approach 2:
The system dynamically changes the aperture parameter based on focus detection results. By calculating an optimized aperture value that considers both the imaging requirements and image plane stability, the system adjusts the aperture setting to prevent excessive image plane movement while maintaining the necessary adaptability for different imaging scenarios.
Data Source
AI summary
An imaging apparatus is provided which comprises: an imaging unit 22 that captures an image through an optical system and outputs an image signal corresponding to the captured image; a focus detection unit 21 that uses the image signal as the basis to detect a focal state of the optical system at a plurality of focus detection positions set in an image plane of the optical system; a calculation unit 21 that calculates a limit value at a closing side of an aperture value of the optical system as a closing side limit value, the limit value corresponding to a focus detection position when the focus detection unit 21 performs focus detection; and a control unit 21 that, when the focus detection unit 21 performs focus detection, sets the aperture value of the optical system on the basis of the closing side limit value corresponding to the focus detection position for performing focus detection.