Zoom Lens with Cemented Triplet for Aberration Correction
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Solution Overview
Problem
Existing zoom lenses face challenges in achieving high performance and compactness while ensuring sufficient back focus, particularly in wide-angle implementations, and often require complex configurations or insufficient angles of view.
Innovation Solution
A zoom lens configuration with a positive-negative-positive-positive group arrangement, including a cemented-triplet lens block with negative refractive power in the fourth lens group, where the distances between lens groups change during zooming to correct aberrations and maintain back focus, and incorporating aspherical surfaces for improved flexibility in aberration correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a six-group zooming configuration is used to achieve small F-numbers and wide-angle coverage, then the optical performance is improved, but the zoom barrel construction becomes complicated
Solution Approach 1:
The zoom lens is divided into four independent lens groups (Gr1, Gr2, Gr3, Gr4) with specific refractive power arrangements. Each group can move independently during zooming, allowing complex optical functions to be achieved through coordinated movement of simpler segments rather than a monolithic complex structure.
Solution Approach 2:
The patent employs conditional expressions for focal lengths and F-numbers across the zoom range (wide-angle end, intermediate focal length, telephoto end) to optimize optical parameters. By carefully controlling focal length ratios and F-number variations, the design achieves high optical performance with a simpler four-group configuration instead of six groups.
2Device complexity
If a four-group configuration is used to simplify the zoom barrel construction, then the device complexity is reduced, but the angle of view at the wide-angle end becomes insufficient
Solution Approach 1:
The patent uses an asymmetric arrangement of refractive powers in the four lens groups (positive-negative-positive-positive) rather than a symmetric configuration. This asymmetric design allows the first group to provide strong positive power for wide-angle coverage while the second group with negative power controls the zoom ratio, achieving both simplicity and wide-angle capability.
Solution Approach 2:
The lens groups are designed to move dynamically during zooming with specific distance relationships. The distance between Gr1 and Gr2 increases, while distances between other groups decrease, creating a dynamic configuration that maintains optimal optical performance across the entire zoom range from wide-angle to telephoto.
3Volume of moving object
If the distance between lens groups is reduced to achieve compactness, then the lens size is decreased, but the back focus becomes insufficient
Solution Approach 1:
The patent resolves the back focus issue by utilizing the longitudinal dimension (optical axis direction) effectively. The fourth lens group Gr4 is positioned close to the image plane with a specific distance relationship, and the cemented-triplet lens block within Gr4 is strategically arranged to provide the necessary back focus while keeping the overall lens compact in lateral dimensions.
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 achieves high performance, compactness, and sufficient back focus, effectively correcting various aberrations and ensuring proper illuminance across the zoom range, while maintaining a balanced optical system.
Implementation Method 1
at least one cemented-triplet lens block having negative refractive power, in the fourth lens group
Implementation Method 2
The zoom lens includes at least one cemented-triplet lens block having negative refractive power, in the fourth lens group
Implementation Method 3
incorporating aspherical surfaces for improved flexibility in aberration correction
Implementation Method 4
During power variation from a wide-angle end to a telephoto end, a distance between the first lens group and the second lens group increases, a distance between the second lens group and the third lens group decreases, and a distance between the third lens group and the fourth lens group decreases
Data Source
AI summary
A zoom lens includes, in an order from an object side, a first lens group having positive refractive power; a second lens group having negative refractive power; a third lens group having positive refractive power; and a fourth lens group having positive refractive power, and in which, during power variation from a wide-angle end to a telephoto end, a distance between the first lens group and the second lens group increases, a distance between the second lens group and the third lens group decreases, and a distance between the third lens group and the fourth lens group decreases, and the zoom lens includes at least one cemented-triplet lens block having negative refractive power, in the fourth lens group.