Aspheric Microscope Objective for Wide-Field Aberration Correction
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Solution Overview
Problem
Microscope objectives with ultra-low magnification struggle to achieve uniform image quality across a wide field of view, particularly in correcting off-axis aberrations such as curvature of field.
Innovation Solution
The objective is designed with a specific configuration of lens groups, including a first lens group with positive refractive power, a second lens group with negative refractive power and one or more aspheric surfaces, a third lens group, and a fourth lens group with positive refractive power, adhering to conditional expressions to ensure a wide field of view and effective aberration correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional lens configurations are used in ultra-low magnification objectives, then the structure is simpler and cost is lower, but off-axis aberrations such as curvature of field cannot be corrected and image quality is non-uniform across the field of view
Solution Approach 1:
The objective lens is divided into four distinct lens groups (G1, G2, G3, G4) with specific functions: G1 for positive refractive power, G2 for negative refractive power with aspheric surfaces, G3 for additional correction, and G4 for final focusing. This segmentation allows each group to address specific aberrations independently, achieving uniform image quality across the wide field of view while maintaining a manageable structural complexity
Solution Approach 2:
Aspheric surfaces are strategically applied only to specific lenses within the second lens group (G2) rather than to all lens surfaces. This local application of aspheric geometry targets the correction of off-axis aberrations where they are most problematic, improving manufacturing precision in critical areas while limiting the overall device complexity and cost
2Manufacturing precision
If aspheric surfaces are added to correct aberrations, then image quality improves, but manufacturing difficulty and cost increase
Solution Approach 1:
Aspheric surfaces are applied locally only to specific lenses within the second lens group rather than to all lens elements. This selective application corrects the most critical off-axis aberrations while minimizing the number of aspheric surfaces that require complex manufacturing processes, thereby balancing image quality improvement with manufacturing feasibility
Solution Approach 2:
Instead of applying aspheric surfaces to all lens elements (excessive action), the patent applies them partially only to the second lens group where they provide the most effective correction for off-axis aberrations. This partial application achieves satisfactory aberration correction without the prohibitive cost and manufacturing difficulty of universal aspheric implementation
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 satisfactory aberration correction from the center to the periphery of the wide field of view, maintaining high image quality and cost-effectiveness by using aspheric surfaces in strategic lens groups.
Implementation Method 1
a second lens group that has one or more aspheric surface and has negative refractive power
Implementation Method 2
a surface of the second lens group that is situated closest to the object side is the surface that is situated closest to the object side among surfaces of the objective that have an effective radius of ER 1/1.5 or less
Data Source
AI summary
An objective includes a positive first lens group, a negative second lens group having one or more aspheric surface, a third lens group, and a positive fourth lens group consists of two lens components; wherein,1.6≤fL/TTL≤5 (1)1.5≤ER1/ER2 (2)D2/OTTL≤0.6 (3) are satisfied.Herein, fL is a focal length. TTL is the distance from the surface closest to the object side to the surface closest to the image side. ER1 is an effective radius of the surface closest to the object side. ER2 is an effective radius of the surface of the second lens group closest to the object side. D2 is the distance from the object plane to the surface of the second lens group closest to the image side. OTTL is the distance from the object plane to the surface closest to the image side.