Zoom Lens with Five Moving Groups for Compact High-Ratio Design
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Solution Overview
Problem
Conventional zoom lenses face challenges in achieving a large zoom ratio while minimizing the overall optical system size while maintaining excellent optical performance.
Innovation Solution
A zoom lens configuration comprising multiple lens groups with specific refractive powers and arrangements, including a first lens group with positive refractive power, a second lens group with negative refractive power, and a third lens group with positive refractive power, where these groups move along the optical axis to adjust focal lengths, ensuring conditional expressions are met to optimize focal lengths and refractive indices for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the zoom ratio is increased in conventional zoom lenses, then the focal length range is improved, but the overall optical system size increases
Solution Approach 1:
The zoom lens is divided into five distinct lens groups (G1-G5) with alternating positive and negative refractive powers. Each group can move independently along the optical axis, allowing complex zoom functionality to be achieved through coordinated movement of segmented components rather than a single large optical system.
Solution Approach 2:
The lens groups are arranged in a nested configuration where smaller lens groups are positioned within the overall optical path defined by larger groups. The negative lens groups (G2, G4) are strategically placed to compact the optical path, enabling a high zoom ratio (56.9x) while keeping the total optical system length compact at 144.97mm in telephoto state.
2Volume of moving object
If the optical system is downsized in conventional zoom lenses, then the portability is improved, but the zoom ratio decreases
Solution Approach 1:
The zoom lens employs dynamic movement of all five lens groups along the optical axis during zooming operations. The first lens group (G1) moves to adjust object-side focal length, while subsequent groups (G2-G5) move to maintain image quality and achieve the extended focal length range. This dynamic coordination enables a compact 106.54mm length in wide-angle state while achieving 56.9x zoom capability.
3Reliability
If the focal lengths and refractive indices are optimized in the first lens group, then the optical performance is improved, but the manufacturing complexity increases
Solution Approach 1:
The first lens group (G1) is designed with specific local optical properties, including a positive meniscus lens with asymmetric surfaces and specific refractive index (nd=1.8830) and Abbe number (vd=40.66). The conditional expression 0.25 < f1/ft < 0.38 optimizes the focal length ratio to control spherical aberration and field curvature, achieving excellent optical performance while maintaining manufacturability through standardized glass materials.
Solution Approach 2:
The patent establishes specific parameter ranges for the lens groups to optimize performance. The conditional expression −0.18 < (f1×fw)/(f2×ft) < 0 optimizes the relationship between first and second lens group focal lengths across the zoom range, while 0.367 < nN1−nP1 ensures appropriate refractive index difference in cemented lenses. These parameter constraints guide manufacturing without requiring exotic materials or complex geometries.
4Reliability
If the cemented lens structure is used in the first lens group, then the aberration correction is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The first lens group incorporates a cemented lens structure combining a negative lens (nd=1.4978, vd=82.57) and a positive lens (nd=1.8830, vd=40.66). This composite structure effectively corrects chromatic aberration by using materials with different dispersion properties. The conditional expression 0.367 < nN1−nP1 ensures sufficient refractive index difference for effective achromatization, while the cemented design eliminates air-glass interfaces that would cause reflections and additional aberrations.
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 enables a zoom lens with a large zoom ratio in a compact form while maintaining excellent optical performance by adjusting focal lengths and refractive indices, thereby correcting aberrations and ensuring high image-forming capabilities across various focal lengths.
Implementation Method 1
a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, and a fifth lens group having positive refractive power
Data Source
AI summary
In a zoom lens comprising a first lens group (G1) having positive refractive power, a second lens group (G2) having negative refractive power, a third lens group (G3) having positive refractive power, a fourth lens group (G4) having negative refractive power, and a fifth lens group (G5) having positive refractive power, the first to fifth lens groups (G1 to G5) are respectively moved along the optical axis so that a distance between the first lens group (G1) and the second lens group (G2), a distance between a distance between the second lens group (G2) and the third lens group (G3), a distance between the third lens group (G3) and the fourth lens group (G4), a distance between the fourth lens group (G4) and the fifth lens group (G5) respectively changes upon zooming from a wide-angle end state to a telephoto end state, so that a conditional expression “0.25<f1−/ft<0.38” is satisfied.