Five-Group Zoom Lens with Fixed End Groups for High Magnification
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Solution Overview
Problem
Conventional zoom lenses for cameras, such as motion-picture and broadcasting cameras, face challenges in achieving a compact and high-performance design with high magnification while maintaining optical quality across the zoom range, often resulting in large diameter and length, and limited zoom ratios.
Innovation Solution
A five-group zoom lens configuration with specific refractive power arrangements, where the first and fifth lens groups are fixed relative to the image plane, and the second, third, and fourth lens groups are moved along the optical axis, satisfying certain condition expressions to optimize focal lengths, refractive indices, and image heights, thereby reducing aberrations and achieving high magnification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional four-group or fewer zoom lens configurations are used, then the lens structure is simpler, but the zoom ratio is limited and cannot achieve high magnification
Solution Approach 1:
The zoom lens is divided into five distinct lens groups (G1-G5) with specific refractive power arrangements. This segmentation allows independent movement of the second, third, and fourth lens groups during zooming while keeping the first and fifth groups fixed, enabling a high zoom ratio of 10× or more without excessive complexity in any single group.
2Adaptability or versatility
If the number of lens groups is increased to achieve high zoom ratio, then the zoom ratio increases, but the diameter and length of the lens system become large
Solution Approach 1:
The second, third, and fourth lens groups are designed to move dynamically along the optical axis during zooming operations. This dynamic configuration allows the lens to achieve high magnification ratios by changing the relative positions of lens groups rather than increasing the overall lens length, maintaining a compact form factor.
Solution Approach 2:
The moving lens groups (G2-G4) are arranged to nest within the optical path defined by the fixed first and fifth lens groups. This nesting arrangement allows multiple lens groups to occupy overlapping spatial regions during zooming, reducing the overall length of the lens system while maintaining high zoom capability.
3Adaptability or versatility
If the number of lens groups is increased to achieve high zoom ratio, then the zoom ratio increases, but the diameter of the lens system increases
Solution Approach 1:
Each lens group is assigned a specific refractive power (positive or negative) and positioned to perform a localized function in the optical path. The second lens group has positive refractive power, the third has negative refractive power, and the fourth has positive refractive power. This localized optimization allows high zoom ratio without requiring all lens groups to have large diameters.
4Ease of manufacture
If conventional zoom lens configurations are used, then manufacturing is simpler, but aberration control during magnification change is insufficient
Solution Approach 1:
The patent specifies precise parameter ranges for refractive powers, focal lengths, and movement distances of lens groups. By controlling these parameters within defined ranges, the lens system maintains good aberration correction across the entire zoom range from wide-angle to telephoto ends, achieving high optical performance without overly complex manufacturing requirements.
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 solution results in a compact, lightweight zoom lens with suppressed aberration changes during magnification, maintaining high optical performance and achieving a high zoom ratio of around 10×, ensuring good performance across the entire zoom range.
Implementation Method 1
a first lens group having a positive refractive power; a second lens group having a positive refractive power; a third lens group having a negative refractive power; a fourth lens group having a negative refractive power; and a fifth lens group having a positive refractive power
Data Source
AI summary
A zoom lens consists essentially of, in order from the object side, a positive first lens group, a positive second lens group, a negative third lens group, a negative fourth lens group, and a positive fifth lens group. During magnification change from the wide-angle end to the telephoto end, the first lens group and the fifth lens group are fixed relative to the image plane, and the second lens group, the third lens group, and the fourth lens group are moved along the optical axis direction to change distances between the lens groups.