Immersion Objective Lens Group Design for Working Distance
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Solution Overview
Problem
Conventional immersion objectives for microscopy have difficulty achieving a long working distance while maintaining a compact size and sufficient aberration correction, especially for observing larger samples with a wide field of view.
Innovation Solution
The design incorporates a first lens group with positive refractive power and a second lens group with negative refractive power, arranged closer to the image, to extend the working distance while minimizing the overall length of the objective, and includes specific lens configurations such as plano-convex and meniscus lenses to effectively correct aberrations like field curvature and comatic aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional immersion objectives are designed with longer working distance, then the ability to observe deeper portions of samples is improved, but the overall length of the objective becomes excessively large
Solution Approach 1:
The objective is divided into multiple lens groups (first lens group with positive refractive power, second lens group with negative refractive power, and third lens group) that can be independently optimized. This segmentation allows each group to contribute differently to the overall optical performance, enabling long working distance while controlling the total length of the objective.
Solution Approach 2:
The patent employs specific refractive index parameters and focal length ratios for different lens groups to optimize the optical path. By carefully selecting and adjusting these parameters (refractive indices, focal lengths, spacing between groups), the design achieves extended working distance without proportionally increasing the overall objective length.
2Area of stationary object
If immersion objectives are designed for wide field of view observation, then the ability to observe larger samples is improved, but aberration correction performance deteriorates
Solution Approach 1:
Different lens groups are assigned specific functions: the first lens group primarily corrects spherical aberration, the second lens group (with negative refractive power) corrects comatic aberration and field curvature, and the third lens group fine-tunes the optical performance. This functional segmentation enables effective aberration correction across the entire wide field of view.
Solution Approach 2:
Each lens group is designed with specific refractive power characteristics tailored to correct particular types of aberrations in specific regions of the field. The negative refractive power of the second lens group is specifically optimized for correcting off-axis aberrations, while the positive refractive power groups handle on-axis and general field correction.
3Length of moving object
If conventional objectives are designed with long working distance, then deeper sample observation is enabled, but comatic aberration and field curvature worsen
Solution Approach 1:
The patent specifies precise parameter ranges for the lens groups, including the ratio of focal lengths and refractive indices. By optimizing these parameters within defined ranges, the design achieves the conditional expression for working distance while simultaneously correcting comatic aberration and field curvature through the coordinated action of the positive and negative refractive power groups.
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 a longer working distance with reduced overall length, enabling high-performance aberration correction over a wide field of view, particularly improving comatic aberrations and field curvature, while maintaining a compact microscope system.
Implementation Method 1
a first lens group, with a positive refractive power, that converts divergent light from an object point into convergent light
Implementation Method 2
a second lens group, with a negative refractive power, that is arranged closer to an image than is the first lens group
Data Source
AI summary
An immersion objective includes a first lens group, with a positive refractive power, that converts divergent light from an object point into convergent light and a second lens group, with a negative refractive power, that is arranged closer to the image than is the first lens group. The immersion objective satisfies the conditional expression below where WD is a working distance of the immersion objective and D is a distance on an optical axis of the immersion objective from the observation target plane to the lens surface closest to the image in the immersion objective.0.11≤WD/D≤0.7