Compact Imaging Lens with Nested Stop for Aberration Correction
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Solution Overview
Problem
Existing imaging lenses face challenges in achieving a reduced total length while maintaining favorable optical performance.
Innovation Solution
The imaging lens is composed of a first lens group with positive refractive power, a second lens group that moves during focusing, and a third lens group, with a negative meniscus lens closest to the object side, and specific conditional expressions are satisfied to optimize lens configuration and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the total length of the lens system is reduced, then the lens becomes more compact, but optical performance deteriorates
Solution Approach 1:
The patent places the stop inside the second lens group, nesting multiple functional elements within a compact space. This allows the lens system to maintain adequate optical path length and aberration correction capability while reducing the overall total length TL, resolving the contradiction between compactness and optical performance.
Solution Approach 2:
The patent uses aspherical surfaces on specific lens surfaces (particularly in the third lens group and on the object-side surface of the first lens group) to provide localized aberration correction. This allows high optical performance to be achieved in a compact design by concentrating correction capability where most needed, rather than uniformly across all elements.
2Reliability
If the number of lenses is increased, then optical performance improves, but device complexity increases
Solution Approach 1:
The patent changes the geometric parameters of lens surfaces, specifically employing aspherical surfaces with carefully controlled curvature radii and shapes. This allows a smaller number of lens elements to achieve the same or better optical performance that would traditionally require more spherical lenses, reducing device complexity while maintaining performance.
Solution Approach 2:
The patent combines different lens materials with specific refractive indices and Abbe numbers in the lens groups. By selecting materials with complementary optical properties and combining them in specific configurations, the patent achieves superior aberration correction with fewer elements, balancing optical performance and device complexity.
3Reliability
If the stop is positioned closer to the object side, then aberration correction improves, but the lens system length increases
Solution Approach 1:
The patent nests the stop within the second lens group rather than placing it as a separate external element. This nested positioning allows the stop to be effectively closer to the object side for better aberration control while occupying space already required by the lens groups, thereby not increasing the overall lens system length.
4Speed
If the second lens group is made movable for focusing, then focusing speed improves, but device complexity increases
Solution Approach 1:
The patent divides the lens system into three distinct lens groups with different functions: the first and third groups remain fixed for stable optical performance, while only the second group moves for focusing. This segmentation allows high-speed focusing with a simple single-group movement mechanism, avoiding the complexity of moving multiple groups or the entire lens assembly.
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
This configuration results in a compact lens system with improved optical performance, enabling high-speed focusing and effective aberration correction.
Implementation Method 1
a first lens group G1 having a positive refractive power, a second lens group G2, and a third lens group G3
Data Source
AI summary
An imaging lens consists of, in order from an object side to an image side, a first lens group having a positive refractive power, a second lens group, and a third lens group. During focusing, the second lens group moves. A lens closest to the object side is a negative meniscus lens, and at least one of a second lens from the object side or a third lens from the object side is a lens other than the negative meniscus lens. A stop is disposed closer to the image side than the second lens from the object side. The imaging lens satisfies a predetermined conditional expression.