Compact Zoom Lens with Abbe Number Constraints for Chromatic Aberration
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Solution Overview
Problem
Existing zoom lenses for broadcasting and motion picture cameras face issues with large size and insufficient chromatic aberration correction, which are exacerbated by the need for compact and high-performance lenses for portable applications.
Innovation Solution
A compact zoom lens design featuring a first lens group with a positive refractive power fixed during magnification change, movable lens groups with specific refractive power configurations, and an end lens group with positive refractive power, where the first lens group includes at least two negative lenses with meniscus shapes and cemented lenses satisfying specific Abbe number and partial dispersion ratio conditions to effectively correct chromatic aberration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the first lens group is divided into first-a, first-b, and first-c lens groups with specific configurations, then chromatic aberration correction is improved, but the size of the first lens group becomes extremely large relative to the image size
Solution Approach 1:
The patent applies parameter changes by carefully selecting the refractive indices (nd), Abbe numbers (vd), and partial dispersion ratios (θgF) of the lens materials. Specifically, the first-n lens satisfies 20 < vd < 60 and -0.65 < θgF < -0.55, while the first-p lens satisfies 20 < vd < 60 and -0.60 < θgF < -0.50. These parameter constraints enable effective chromatic aberration correction while controlling the physical size of the lens group.
Solution Approach 2:
The patent uses composite material principles by combining lenses with different optical properties. The first-a lens group includes at least two negative lenses with specific material characteristics that complement each other. The cemented lens structure combining first-n and first-p lenses creates a composite optical element that corrects chromatic aberration more efficiently than single lenses, reducing the overall group size.
2Length of moving object
If the power of the first lens group is increased to reduce the entire length, then the compactness is improved, but chromatic aberration correction becomes insufficient
Solution Approach 1:
The patent resolves this contradiction through precise parameter control of lens materials. The first-n lens is constrained to 20 < vd < 60 and -0.65 < θgF < -0.55, while the first-p lens follows 20 < vd < 60 and -0.60 < θgF < -0.50. These parameter ranges are specifically selected to achieve optimal chromatic aberration correction at the required compact length.
Solution Approach 2:
The patent employs dynamic design by making the first-b lens group movable during focusing. This allows the optical system to maintain compact dimensions while adjusting the optical path to preserve chromatic aberration correction performance across different focusing states.
3Reliability
If a focusing system with multiple lens groups is used to prevent angle of view change, then imaging performance is improved, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the first lens group into three sub-groups (first-a, first-b, first-c) with distinct functions. The first-a group (negative power) corrects chromatic aberration, the first-b group (positive power) performs focusing by moving along the optical axis, and the first-c group (positive power) completes the optical power distribution. This segmentation enables independent optimization of each sub-group, achieving good imaging performance while managing complexity through functional specialization.
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-performance zoom lens with successful chromatic aberration correction, enabling size reduction and high image quality while minimizing changes in lens length during magnification, thus addressing the limitations of previous lens systems.
Implementation Method 1
a first-n lens, which is at least one negative lens of the rest of the negative lenses of the first-a lens group, satisfies the condition expressions (1), (2), and (3) below: 62gFn+0.001625×vdn0.7 (2), and 1fln/fla2 (3), where vdn is an Abbe number with respect to the d-line of the first-n lens, θgFn is a partial dispersion ratio of the first-n lens
Implementation Method 2
the first-a lens group includes at least two negative lenses, wherein the most object-side negative lens has a meniscus shape with the convex surface toward the object side, and a first-n lens, which is at least one negative lens of the rest of the negative lenses of the first-a lens group
Data Source
AI summary
A zoom lens consists of, in order from the object side, a positive first lens group that is fixed during magnification change, at least two movable lens groups that are moved during magnification change, and a positive end lens group that is disposed at the most image side and is fixed during magnification change. The first lens group consists of, in order from the object side, a negative first-a lens group that is fixed during focusing, a positive first-b lens group that is moved during focusing, and a positive first-c lens group. The first-a lens group includes at least two negative lenses, where the most object-side negative lens has a meniscus shape with the convex surface toward the object side, and a first-n lens, which is at least one negative lens of the rest of the negative lenses of the first-a lens group, satisfies given condition expressions (1) to (3).