Imaging Lens with Moving Cemented Groups for Aberration Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional single focus imaging lenses lack a wide focusing range and insufficient suppression of aberrations during focusing, particularly in applications like machine vision and factory automation where precise detection and measurement are required, and the lens system often cannot maintain a constant length during focusing.
Innovation Solution
The design incorporates a first lens group fixed relative to the image plane and a second lens group that moves towards the object side during focusing, comprising specific cemented lenses with controlled refractive indices and Abbe numbers, with a stop positioned between the lens groups to maintain lens length and reduce aberrations, satisfying specific condition expressions for optimal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional retrofocus lens system is used with a negative lens group on the object side and a positive lens group on the image side, then the lens can achieve basic focusing function, but the focusing range is insufficient and aberrations (spherical aberration and astigmatism) are not sufficiently suppressed
Solution Approach 1:
The lens system is divided into multiple lens groups with specific configurations. The second lens group is further segmented into a first cemented lens (biconvex lens + negative lens) and a second cemented lens (negative lens + positive lens), allowing independent optimization of each segment's contribution to focusing range and aberration control
Solution Approach 2:
Different regions of the lens system are assigned different optical properties. The biconvex lens in the first cemented lens provides strong positive power for extending focusing range, while the negative lenses with specific radius of curvature ratios correct spherical aberration. The stop position is optimized to control astigmatism, creating local quality variations that collectively resolve the contradiction
2Ease of operation
If the lens system is designed to maintain constant entire length during focusing, then installation constraints for FA and machine vision are satisfied, but the focusing range and aberration suppression are compromised
Solution Approach 1:
Instead of moving the entire lens system or the first lens group to achieve focusing (which would change the entire length), the invention moves only the second lens group while keeping the first lens group and stop fixed. This inverted approach to focusing mechanism maintains constant entire length while achieving the required focusing range through optimized movement of the second lens group
3Adaptability or versatility
If the second lens group is moved during focusing, then focusing function is achieved, but the entire lens length changes which conflicts with installation constraints
Solution Approach 1:
The stop acts as an intermediary reference point that remains fixed during focusing. By positioning the stop between the first and second lens groups and keeping it fixed while moving only the second lens group, the system achieves focusing function while maintaining constant entire length. The stop mediates between the moving second lens group and the fixed first lens group
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 allows for focusing without changing the entire lens length, achieves a wide focusing range, and effectively suppresses aberrations, ensuring good optical performance across the focusing range.
Implementation Method 1
a first cemented lens consisting of, in order from the object side, a biconvex lens and a negative lens having a smaller absolute value of radius of curvature of the object-side surface than that of the image-side surface
Implementation Method 2
a second cemented lens as a whole having a positive refractive power and consisting of, in order from the object side, a negative lens having a smaller absolute value of radius of curvature of the image-side surface than that of the object-side surface and a positive lens having a smaller absolute value of radius of curvature of the object-side surface than that of the image-side surface
Data Source
AI summary
An imaging lens consists of, in order from the object side, a first lens group fixed during focusing, and a positive second lens group moved toward the object side during focusing from a distant object to a close object. The second lens group consists of, in order from the object side, a first cemented lens consisting of a biconvex lens and a negative lens having a smaller absolute value of curvature radius of the object-side surface than that of the image-side surface, and a second cemented lens as a whole having a positive refractive power and consisting of a negative lens having a smaller absolute value of curvature radius of the image-side surface than that of the object-side surface and a positive lens having a smaller absolute value of curvature radius of the object-side surface than that of the image-side surface. The imaging lens satisfies specific condition expressions.