Zoom Lens Fourth Group Segmentation for Compact Autofocus
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Solution Overview
Problem
Existing zoom lenses face challenges in reducing size while maintaining long focal lengths and achieving favorable optical performance, particularly in correcting image blurring caused by vibration and camera shake, and they often have configurations that hinder autofocus speed and durability in surveillance applications.
Innovation Solution
A zoom lens configuration comprising a first lens group with positive refractive power, a second and third lens group with negative refractive power that move during zooming, and a fourth lens group with a specific arrangement of sub-groups that include a vibration reduction and focusing lens group, optimized to satisfy certain conditional expressions for refractive powers and movements, which reduces the overall size and improves optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fourth lens group is designed with sufficient diameter to accommodate the divergence effect of the second and third lens groups, then the optical performance is improved, but the overall size of the lens system increases
Solution Approach 1:
The fourth lens group is divided into five sub-groups (fourth A through fourth E lens groups) with different functions. The fourth B lens group is specifically designated for vibration reduction and the fourth D lens group for focusing, allowing each segment to be optimized for its specific purpose while contributing to the overall compact design.
Solution Approach 2:
The fourth B lens group is designed to move in a direction intersecting with the optical axis during image blur correction, and the fourth D lens group moves along the optical axis during focusing. This dynamic capability allows the lens system to correct vibrations and perform autofocus without requiring a larger stationary lens diameter.
2Ease of operation
If the focusing lens group is provided in the first group having large aperture and mass, then the focusing function is achieved, but the autofocus speed decreases and the durability of focusing mechanism is reduced
Solution Approach 1:
The focusing function is extracted from the first lens group and relocated to the fourth D lens group, which has a smaller diameter and mass. This extraction allows the focusing mechanism to operate more quickly and with greater durability, as the smaller lens group requires less force and distance to move for focusing.
3Adaptability or versatility
If the second and third lens groups are designed with negative refractive power to achieve zooming, then the zooming function is improved, but the divergence effect increases causing the fourth lens group to increase in diameter
Solution Approach 1:
The fourth lens group is segmented into five sub-groups that can be optimized for different functions. This segmentation allows the design to accommodate the divergence effect from the negative refractive power lens groups while maintaining a compact overall structure through specialized sub-groups for vibration reduction and focusing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed configuration allows for a compact zoom lens with enhanced optical performance, effective vibration reduction, and improved autofocus speed, suitable for surveillance applications, while maintaining long focal lengths and reducing the diameter of lens groups for better durability and performance.
Implementation Method 1
a fourth B lens group which has a negative refractive power and moves in a direction intersecting with an optical axis during image blur correction
Implementation Method 2
a fourth D lens group which moves along the optical axis during focusing
Implementation Method 3
a first lens group that has a positive refractive power; a second lens group that has a negative refractive power; a third lens group that has a negative refractive power; and a fourth lens group that has a positive refractive power
Data Source
AI summary
The zoom lens consists of, in order from an object side, a positive first lens group, a negative second lens group, a negative third lens group, and a positive fourth lens group. During zooming from a wide-angle end to a telephoto end, the second lens group moves to an image side, and the third lens group moves to the image side after moving to the object side. The fourth lens group consists of, in order from the object side, a positive fourth A lens group, a negative fourth B lens group moving during image blur correction, a positive fourth C lens group, a fourth D lens group moving during focusing, and a fourth E lens group having a refractive power with a sign different from that of a refractive power of the fourth D lens group.