Interchangeable Lens Focus Control for Variable Image Plane Movement
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Solution Overview
Problem
Existing interchangeable lens systems lack efficient methods for accurately determining the focal state of the optical system during focus adjustment, particularly in systems that calculate contrast values while driving focus adjustment lenses at predetermined speeds.
Innovation Solution
The system employs a focus lens drive motor and encoder mechanism to detect the position of the focus lens, combined with a lens memory to store image plane movement coefficients, allowing for precise control of focus and zoom adjustments based on lens positions, and utilizes both phase difference and contrast detection systems for focus evaluation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If focus adjustment lens is driven at predetermined drive speed to calculate contrast values, then focus detection can be performed, but focus accuracy deteriorates when image plane movement coefficient varies significantly
Solution Approach 1:
The patent dynamically adjusts the drive speed of the focus adjustment lens based on the image plane movement coefficient, which varies with zoom lens position and focus lens position. Instead of using a fixed predetermined drive speed, the system adapts the drive speed to current optical conditions, ensuring reliable focus detection across all zoom and focus ranges.
Solution Approach 2:
The patent changes the drive speed parameter according to the image plane movement coefficient. When the coefficient is large (indicating significant image plane movement), the drive speed is reduced to maintain focus detection accuracy. This parameter adjustment resolves the contradiction between maintaining predetermined drive speed simplicity and achieving reliable focus detection under varying optical conditions.
2Measurement precision
If drive speed is reduced to improve focus detection accuracy when image plane movement coefficient is large, then focus accuracy improves, but adjustment time increases
Solution Approach 1:
The patent dynamically adjusts drive speed based on real-time calculation of the image plane movement coefficient. When the coefficient is small (low image plane movement), the system uses higher drive speeds to reduce adjustment time. When the coefficient is large, it reduces speed to maintain accuracy. This dynamic adaptation resolves the time-accuracy tradeoff.
Solution Approach 2:
The drive speed parameter is changed according to the image plane movement coefficient to optimize the balance between focus detection accuracy and adjustment time. This conditional parameter adjustment ensures that the system does not always use the slowest speed, thereby minimizing time loss while maintaining accuracy when needed.
3Productivity
If maximum drive speed is used for focus adjustment, then adjustment speed is maximized, but focus detection accuracy deteriorates when image plane movement exceeds pixel displacement
Solution Approach 1:
The patent implements a periodic evaluation approach where the system first calculates the image plane movement coefficient, then determines whether to use maximum drive speed or reduced drive speed based on this calculation. This periodic decision-making process ensures that high-speed operation only occurs when it will not compromise accuracy.
Solution Approach 2:
The drive speed parameter is conditionally changed based on the image plane movement coefficient. When the coefficient indicates that image plane movement will exceed acceptable pixel displacement thresholds, the system reduces the drive speed parameter to maintain detection precision. This parameter adaptation resolves the contradiction between maximum speed and accuracy.
Data Source
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AI summary
An interchangeable lens is provided which comprises: an optical system that includes a focus adjustment lens; a transceiver that performs transmission and reception of a signal between the interchangeable lens and a camera body; and a control unit configured to control the transceiver to transmit, to the camera body, a minimum value of an image plane movement coefficient that represents correspondence relationship between a movement amount of the focus adjustment lens and a movement amount of an image plane.