Zoom Lens Aberration Correction via Refractive Index Control
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Solution Overview
Problem
Existing zoom lenses face challenges in achieving a high zoom ratio and wide angle while maintaining optical performance and downsizing, due to increased aberrations and difficulty in correcting spherical and chromatic aberrations, especially at the telephoto end.
Innovation Solution
A zoom lens configuration with specific refractive power arrangements and movement patterns, including a first lens group with a single positive refractive power, a second lens group with negative power moving towards the image side, a third lens group with positive power moving towards the object side, and a fourth lens group with negative power moving during zooming and focusing, while optimizing the refractive indices and movement ratios to satisfy specific conditional expressions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the zoom ratio is increased and focal length at telephoto end is increased, then the zoom ratio is improved, but various aberrations such as spherical aberration, astigmatism, and chromatic aberration are increased
Solution Approach 1:
The patent applies parameter changes by precisely controlling the refractive indices of lens materials and the movement ratios of lens units during zooming. Specifically, it sets constraints on the refractive index of the positive lens (1.50 < Nd1pf ≤ 1.80) and the ratio of movement amounts (0.30 < M2/Mv < 1.50), thereby optimizing optical performance across the zoom range while achieving high zoom ratio
Solution Approach 2:
The patent segments the optical system into five distinct lens units with alternating positive and negative refractive powers. This segmentation allows independent optimization of each lens unit's movement characteristics and refractive properties, enabling correction of multiple aberrations simultaneously while maintaining high zoom ratio
2Adaptability or versatility
If the angle of view is increased, then the angle of view is improved, but the effective diameter of the first lens unit is increased
Solution Approach 1:
The patent controls the focal length ratio of the first lens unit to the entire zoom lens (4.80 ≤ f1/fw < 8.00) and sets specific refractive index ranges for lens materials. These parameter constraints enable the first lens unit to maintain a smaller effective diameter while supporting a wider angle of view through optimized optical path design
3Adaptability or versatility
If the focal length of the first lens unit is shortened, then the angle of view is improved, but spherical aberration and coma at telephoto positions deteriorate
Solution Approach 1:
The patent optimizes the focal length of the first lens unit by constraining its ratio to the total focal length (4.80 ≤ f1/fw < 8.00). This parameter optimization allows the system to achieve wide angle of view while maintaining adequate spherical aberration and coma correction at telephoto positions through the coordinated design of all five lens units
Solution Approach 2:
The patent employs composite lens designs with multiple lenses in each lens unit, using materials with different refractive indices (1.50 < Nd1pf ≤ 1.80 for positive lenses). This composite approach enables correction of spherical aberration and coma while maintaining the required angle of view and focal length relationships
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 compact zoom lens with a high zoom ratio and wide angle, maintaining high optical performance across the entire zoom range by effectively correcting aberrations and reducing the effective diameter of the first lens group.
Implementation Method 1
a first lens group, which is not moved for zooming and is composed of a single lens unit having a positive refractive power; a second lens group which has a negative refractive power and includes at least one lens unit each of which is moved toward an image side during zooming from a wide angle end to a telephoto end; a third lens group, which has a positive refractive power and includes at least one lens unit each of which is moved toward the object side during zooming from the wide angle end to the telephoto end
Data Source
AI summary
A zoom lens includes, in order from object-side, a fixed positive first group including three-or-more lenses, a negative second group including a unit moving toward image-side during zooming toward telephoto-end, a positive third group including a unit moving toward object-side during zooming from wide-end to telephoto-end, a negative fourth group moving during zooming and focusing, and a rear group. Focal lengths of the first group and the zoom lens at wide-end, a movement amount of a unit moving by largest amount during zooming toward telephoto-end in the second group, a largest value of position change between wide-end and telephoto-end of units moving toward an object side during zooming from wide-end to telephoto-end, refractive index for d-line of a positive lens closest to image-side in the first group, and average refractive index for d-line of positive lenses of the first group other than the positive lens are appropriately set.