Rear Focus Lens Stabilization via Normalized Position Data
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Solution Overview
Problem
Existing camera systems with rear focus type lenses face challenges in maintaining focus position stability during zooming, leading to shallower depth of field and increased resolution requirements, and excessive information transmission is necessary for pulse and object distance parameters.
Innovation Solution
A lens apparatus with a variable magnification lens and focus lens, equipped with a position detection unit, memory for electronic cam data, and a lens control unit that calculates normalized position information and sensitivity, allowing for focus lens driving amounts to be adjusted without changing focus position during zooming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If focus position is adjusted according to zoom position in rear focus type lens, then focus can be maintained at same object distance, but focus position shifts and requires additional correction
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the relationship between zoom position and focus position in electronic cam data before actual operation. When zooming occurs, the system simply retrieves the pre-computed focus position from memory rather than calculating it in real-time, eliminating the need for complex real-time correction mechanisms.
Solution Approach 2:
The patent replaces the traditional mechanical cam mechanism with an electronic cam system. Instead of using physical cam profiles that require precise mechanical manufacturing and adjustment, the focus position relationship is stored as digital data in memory, which can be easily updated and accessed without mechanical wear or alignment issues.
2Reliability
If focusing is controlled by object distance information, then focus position stability during zooming is improved, but depth of field becomes shallower and resolution requirements increase
Solution Approach 1:
The patent changes the control parameter from object distance information to normalized focus position information. By normalizing the focus position based on the relationship between zoom and focus positions, the system maintains focus stability without requiring high-resolution object distance measurements, thus avoiding the shallower depth of field problem.
3Ease of operation
If pulse information and object distance information are transmitted from lens to camera, then focusing control is achieved, but information transmission amount increases
Solution Approach 1:
The patent extracts only the essential information needed for focusing control - the normalized focus position information - and transmits it to the camera. By removing unnecessary parameters such as detailed pulse information and object distance information, the system achieves effective focusing control with minimal data transmission.
Data Source
AI summary
A lens apparatus detachably attachable to an image pickup apparatus, the lens apparatus includes a variable magnification lens arranged to move along an optical axis when changing magnification, a focus lens (105) arranged to move along the optical axis so as to perform focusing, position detection means for detecting a position of the focus lens, lens control means for acquiring normalized position information of the focus lens based on position information of the focus lens, and a memory arranged to store electronic cam data representing a position relation of the variable magnification lens and the focus lens corresponding to a plurality of object distances and, and a sensitivity of the focus lens calculated based on the normalized position information of the focus lens.