Five-Group Zoom Lens Compact High Magnification
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Solution Overview
Problem
Existing zoom lenses for digital cameras face challenges in achieving high magnification while maintaining a compact size and short overall length, with previous designs either having excessive length or insufficient zoom magnification.
Innovation Solution
A zoom lens configuration comprising five lens groups with specific refractive powers and movements between them, including a first lens group with a negative meniscus and positive lenses, a second lens group with negative and biconvex lenses, a third lens group that moves for focusing, and a fifth lens group with biconvex and biconcave lenses, optimized to satisfy specific focal length and Abbe number conditions for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a four-group zoom lens configuration is used to achieve high magnification, then zoom magnification is improved, but the entire length becomes excessive
Solution Approach 1:
The zoom lens is divided into five separate lens groups (G1-G5) with different refractive powers, allowing independent movement of each group during zooming. This segmentation enables compact packaging while maintaining high zoom magnification capability through coordinated movement of the five groups.
Solution Approach 2:
The lens groups are designed to move dynamically during magnification change, with specific groups moving in opposite directions. The first lens group moves toward the object side while the second lens group moves toward the image side, enabling compact telephoto configuration without increasing overall length.
2Reliability
If lens groups are moved to increase distance between second and third lens groups for better focusing performance, then focusing capability is improved, but the entire length increases
Solution Approach 1:
The third lens group is designed to move independently during focusing operations, allowing adjustment of the distance between the second and third lens groups. This dynamic movement enables close-focus capability while maintaining a compact overall lens structure through precise control of group spacing.
3Length of stationary object
If a five-group zoom lens configuration is used to reduce entire length, then compactness is improved, but zoom magnification becomes insufficient
Solution Approach 1:
The five lens groups are assigned specific refractive powers with alternating signs (+, -, -, +, +), creating a segmented optical system that achieves high zoom magnification through coordinated movement. The segmentation allows each group to contribute differently to the overall magnification while maintaining compact dimensions.
Solution Approach 2:
The lens groups are designed with specific focal length ratios satisfying f1/|f2|≥0.4 and |f3/ f5|≤4.0, and refractive index-Abbe number combinations that optimize both compactness and zoom magnification. By carefully controlling these parameters, the patent achieves high magnification in a short overall length.
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
This configuration enables a zoom lens with high magnification and a short overall length, providing compactness and high-quality images while effectively managing aberrations and image stabilization.
Implementation Method 1
a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a negative refractive power, a fourth lens group having a positive refractive power, and a fifth lens group having a positive refractive power, wherein the first lens group, the second lens group, the third lens group, the fourth lens group, and the fifth lens group are moved to change distances therebetween during magnification change
Implementation Method 2
the third lens group consists essentially of a negative lens with the object side surface having an absolute value of radius of curvature smaller than that of the image-side surface thereof, and the third lens group is moved during focusing
Data Source
AI summary
A five-group zoom lens including, in order from the object side, positive, negative, negative, positive, and positive groups. The first group includes a negative meniscus lens with the concave surface toward the image side, a positive lens and a positive lens. The second group includes a negative lens with the image-side surface having an absolute value of curvature radius smaller than that of the object side surface, a biconcave lens, and a biconvex lens. The third group includes a negative lens with the object side surface having an absolute value of curvature radius smaller than that of the image-side surface, and is moved during focusing on a closer object. The fifth group includes a positive fifth-A group including a biconvex lens, and a negative fifth-B group including a biconcave lens and a biconvex lens, wherein condition expression (1) is satisfied:0.22<fW/f1<0.27 (1).