Zoom Lens Final Group Segmentation for Aberration Control
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Solution Overview
Problem
There is a demand for a zoom lens that is compact and lightweight for imaging applications like movie and broadcast cameras, but achieving both size reduction and weight reduction while maintaining high optical performance is challenging, as it often results in increased spherical aberration and field curvature.
Innovation Solution
A zoom lens design comprising a stationary first lens group with positive refractive power, movable lens groups, and a stationary final lens group with positive refractive power, where the final lens group is separated into a front and rear group by an air distance, with specific configurations of lenses and Conditional Expressions to optimize optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If reduction in size and weight is achieved, then compactness and maneuverability are improved, but spherical aberration and field curvature increase
Solution Approach 1:
The final lens group is divided into a front group and a rear group separated by an air distance, allowing independent optimization of each subgroup to correct spherical aberration and field curvature while maintaining compact overall size
Solution Approach 2:
The second front group negative lens is designed with a specific concave shape toward the image side, and the rear group negative meniscus lens is configured with specific curvature ratios, creating localized optical corrections in critical regions of the lens system
2Length of moving object
If reduction in size and weight is achieved, then compactness and operability are improved, but field curvature becomes large
Solution Approach 1:
Dividing the final lens group into front and rear subgroups with an air gap between them enables distributed correction of field curvature across different zones of the optical path, achieving flat field performance in a compact form
Solution Approach 2:
The asymmetric configuration of negative lenses with specific concave/convex orientations and curvature ratios creates balanced optical correction that compensates for field curvature while maintaining compact lens 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
The design achieves a balance between size and weight reduction while maintaining high optical performance by minimizing spherical aberration and field curvature, as demonstrated by satisfying Conditional Expressions (1) to (4), which allow for effective correction of chromatic and spherical aberrations.
Implementation Method 1
a first lens group that remains stationary with respect to an image plane during zooming and has a positive refractive power; at least two movable lens groups that are moved by changing distances between the movable lens groups and adjacent groups in a direction of an optical axis during zooming
Data Source
AI summary
The zoom lens consists of, in order from an object side: a first lens group that remains stationary during zooming and has a positive refractive power; at least two movable lens groups that are moved during zooming; and a final lens group that remains stationary during zooming and has a positive refractive power. The final lens group consists of, in order from the object side, a front group and a rear group. The front group has, successively in order from a position closest to the object side, two or less positive lenses and one first front group negative lens, and a second front group negative lens that is different from the first front group negative lens at a position closest to an image side and is concave toward the image side. An aperture stop is provided between the movable lens group and the first front group negative lens. The rear group consists of a positive lens and a rear group negative meniscus lens that is convex toward the image side. In addition, the zoom lens satisfies predetermined conditional expressions.