Zoom Lens with Fixed Positive Units for Compact High-Magnification Design
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Solution Overview
Problem
Existing zoom lenses face challenges in achieving a high magnification variation ratio while maintaining small size and correcting aberrations, particularly in achieving both wide-angle and telephoto configurations with reduced size and chromatic aberration.
Innovation Solution
A zoom lens configuration with four or more lens units, including a first positive, second negative, and third positive refractive power units, where the third lens unit has three positive lens elements, and specific inequalities are satisfied to control focal lengths, refractive indices, and lateral magnifications, allowing for fixed positions of certain lens units during zooming to maintain optical performance and reduce size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the refractive powers of the first and second lens units are enhanced to reduce size and suppress aberrations in telephoto range, then the size is reduced and chromatic aberration is corrected, but the lens cannot achieve a wide-angle configuration
Solution Approach 1:
The zoom lens is divided into multiple lens units (first through fourth lens units) with different refractive powers and movement characteristics. The first lens unit has positive refractive power, the second has negative refractive power, the third has positive refractive power, and the fourth has negative refractive power. This segmentation allows each unit to be optimized for specific functions while working together to achieve both wide-angle and telephoto configurations.
Solution Approach 2:
Different lens units have different movement characteristics during zooming. The first and third lens units move toward the image side, while the second and fourth lens units move toward the object side. This dynamic arrangement allows the lens to achieve a high magnification variation ratio (wide-angle to telephoto range) while maintaining compact size and correcting aberrations across the entire zoom range.
2Adaptability or versatility
If a high magnification variation ratio is achieved, then the zoom range is expanded, but the lens size and complexity increase
Solution Approach 1:
The lens employs a dynamic zoom mechanism where four lens units move in opposite directions during zooming. The first and third lens units (with positive refractive power) move toward the image side, while the second and fourth lens units (with negative refractive power) move toward the object side. This coordinated movement allows achievement of a high magnification variation ratio of 14.6x while maintaining a compact overall lens size.
Solution Approach 2:
The lens satisfies specific parameter relationships: 0.005 < f3/ft < 0.150, 1.90 < nd3u < 2.30, and -0.50 < β2w < 0.01, where f3 is the focal length of the third lens unit, ft is the focal length at telephoto end, nd3u is the maximum refractive index of lenses in the third unit, and β2w is the lateral magnification of the second lens unit at wide-angle end. These parameter constraints optimize the balance between zoom ratio and lens size.
3Reliability
If the number of lens units is increased to correct aberrations, then optical performance is improved, but the lens becomes more complex and larger
Solution Approach 1:
The zoom lens is segmented into four lens units with alternating refractive powers (positive, negative, positive, negative). This segmentation allows effective correction of various aberrations including spherical aberration, coma, and chromatic aberration, while maintaining a relatively compact and manageable structure.
Solution Approach 2:
The lens optimizes specific parameters to balance aberration correction with structural simplicity. The third lens unit has a focal length ratio f3/ft between 0.005 and 0.150, and the maximum refractive index nd3u is constrained between 1.90 and 2.30. These parameter constraints enable effective aberration correction without excessive complexity.
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 configuration achieves a high magnification variation ratio while effectively correcting spherical and chromatic aberrations over the entire zoom range, ensuring a compact size and high optical performance across both wide-angle and telephoto ranges.
Implementation Method 1
The third lens unit includes three lens elements each having positive refractive power
Implementation Method 2
nd3u is a maximum value among refractive indices for d-line of lenses included in the third lens unit
Data Source
AI summary
A zoom lens includes four or more lenses that include, in order from an object side to an image side, a first lens unit having positive refractive power, a second lens unit having negative refractive power, and a third lens unit having positive refractive power. A distance between adjacent lens units changes during zooming from a wide-angle end to a telephoto end. For zooming from the wide-angle end to the telephoto end, the first lens unit and the third lens unit are fixed relative to an image plane, and the second lens unit moves toward the image side. The third lens unit includes three lens elements each having positive refractive power. Predetermined inequalities are satisfied.