Stereo Microscope Variable Power Optical System Design
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Solution Overview
Problem
Conventional variable power optical systems for stereomicroscopes face challenges in achieving a wide variable power range while maintaining a large numerical aperture, leading to insufficient performance in both aspects.
Innovation Solution
A variable power optical system with a configuration of a first lens group having positive refractive power, a second lens group with negative refractive power and an achromatic cemented lens, an aperture stop, and a fourth lens group with negative refractive power, where the second and third lens groups move in opposite directions along the optical axis, optimizing the position of the entrance pupil closer to the object to enhance the variable power range and aberration correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the variable power range is made wide, then the magnification flexibility is improved, but the numerical aperture becomes small
Solution Approach 1:
The optical system is divided into multiple lens groups (first through fourth lens groups) with different refractive powers. Each group can move independently along the optical axis, allowing separate control of magnification and numerical aperture. This segmentation enables the system to achieve wide variable power range while maintaining large numerical aperture by coordinating the movement of different lens groups.
Solution Approach 2:
The patent employs dynamic movement of lens groups during zooming operations. Specifically, the second and third lens groups move in opposite directions along the optical axis, which dynamically adjusts the effective focal length while preserving the entrance pupil position and numerical aperture. This dynamic coordination resolves the contradiction between variable power range and numerical aperture.
2Measurement precision
If the numerical aperture is made large, then the resolution is improved, but the variable power range becomes narrow
Solution Approach 1:
By segmenting the optical system into multiple independently controllable lens groups, the patent enables simultaneous optimization of numerical aperture and variable power range. The first and fourth lens groups maintain the large numerical aperture, while the second and third lens groups provide the variable power functionality through their coordinated movement.
Solution Approach 2:
The optical system achieves multi-functionality by enabling both high numerical aperture (for resolution) and wide variable power range (for magnification flexibility) within a single system. The coordinated movement mechanism allows the system to perform both functions simultaneously across the entire zoom range, making it universally applicable to various observation requirements.
3Adaptability or versatility
If the entrance pupil position is moved closer to the object, then the variable power range is enhanced, but the aberration correction becomes more difficult
Solution Approach 1:
The patent divides the optical system into multiple lens groups that can move independently. This segmentation allows the entrance pupil to be positioned closer to the object for enhanced variable power range, while separate lens groups (particularly the second and third groups moving in opposite directions) are used to correct aberrations that arise from this configuration.
Solution Approach 2:
The patent employs parameter changes in the form of coordinated movement of lens groups along the optical axis. By changing the positions of the second and third lens groups in opposite directions, the system maintains proper aberration correction despite the entrance pupil being positioned closer to the object, thus resolving the contradiction between variable power range and aberration correction.
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 wide variable power range and effective aberration correction, improving the numerical aperture and resolution of the objective optical system, making it suitable for high-magnification applications like fluorescent illumination.
Implementation Method 1
a second lens group with negative refractive power and an achromatic cemented lens
Data Source
Figure 1A~1C
Figure 2A
Figure 2B
AI summary
The present invention includes, in order from an object: a first lens group G1 having positive refractive power; a second lens group G2 having negative refractive power; an aperture stop S; a third lens group G3 having positive refractive power; and a fourth lens group G4 having negative refractive power. The second lens group G2 has, in order from an object, a front group G2F having negative refractive power and a rear group G2R having an achromatic cemented lens including a positive lens and a negative lens. The second lens group G2 and the third lens group G3 move in opposite directions along an optical axis at least in a part of a variable power block. In this configuration, the following conditional expressions are satisfied, 0.4 < f2F / f2 < 1.6 and -3.0 < q2 < -0.3 where f2 denotes a focal length of the second lens group G2, f2F denotes a focal length of the front group G2F of the second lens group, and q2 denotes a form factor of a negative lens disposed closest to the object of the front group G2F constituting the second lens group.