Compact Zoom Lens Design with Aberration Control
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Solution Overview
Problem
Existing zoom lenses with high zoom ratios face challenges in maintaining optical performance due to increased surface precision requirements, leading to higher fabrication costs and difficulties in processing, especially as lens length shortens, affecting aberration properties.
Innovation Solution
A zoom lens design comprising a first lens group with a negative and positive lens, a second lens group of negative refracting power, and a third lens group of positive refracting power, where zooming is achieved by adjusting the spacing between these groups, with specific refractive index and curvature conditions to minimize aberration fluctuations and lens movement, thereby reducing the overall size and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the total lens length is shortened at increased zoom ratios, then the compactness and portability are improved, but the surface precision requirement increases leading to higher fabrication costs and difficulty
Solution Approach 1:
The patent applies parameter changes by optimizing the refractive index and curvature radius of lens surfaces to reduce the impact of surface precision errors on aberration properties. Specifically, condition (2) controls the refractive index of the positive lens in the first group, and condition (3) controls the curvature radius ratio, thereby achieving compact design with reduced sensitivity to manufacturing precision
Solution Approach 2:
The patent uses composite lens group design combining positive and negative lens groups with specific refractive index combinations. The first lens group comprises a positive lens and negative lens with carefully selected refractive indices to achieve both compactness and reduced sensitivity to surface precision errors
2Volume of moving object
If the total lens length is shortened at increased zoom ratios, then the fabrication cost increases due to higher surface precision requirements
Solution Approach 1:
The patent changes optical parameters (refractive index, curvature radius) to reduce the stringency of surface precision requirements. By satisfying condition (2) on refractive index and condition (3) on curvature radius ratio, the design achieves compact form factor while maintaining manufacturability and reducing fabrication costs
3Reliability
If the lens groups are moved less during zooming, then the aberration fluctuations are minimized, but the zooming capability is reduced
Solution Approach 1:
The patent applies local quality by assigning different functions to different lens groups: the first lens group (with specific positive and negative lenses) primarily corrects aberrations while the second and third lens groups provide the zooming function through their relative movements. This functional differentiation allows minimal movement of the first group, stabilizing aberrations while maintaining zoom capability
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 design achieves a compact, high-zoom ratio lens system with improved optical performance, reduced aberrations, and lower fabrication costs, while maintaining good aberration correction across the zoom range.
Implementation Method 1
a positive lens with a d-line refractive index Nd1p satisfying 1.40<Nd1p<1.67
Data Source
AI summary
The invention relates to a zoom lens and an imaging apparatus incorporating the same, and more particularly to a zoom lens of small format that lends itself to imaging apparatus inclusive of video cameras and digital cameras. The zoom lens comprises, in order from its object side, a first lens group G1 of positive refracting power, a second lens group G2 of negative refracting power and a third lens group G3 of positive refracting power. Zooming is implemented by changing the space between the respective lens groups. The first lens group G1 comprises one negative lens and one positive lens in order from the object side. The zoom lens satisfies conditions (1) and (2):5.0<ft/fw<50.0 (1)1.4<Nd1p<1.7 (2)where fw is the focal length of the whole zoom lens system at a wide-angle end, ft is the focal length of the whole zoom lens system at a telephoto end, and Nd1p is the d-line refractive index of the positive lens in the first lens group.