Variable Magnification Optics With Fixed Aberration Correction
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Solution Overview
Problem
Existing variable magnification optical systems face challenges in maintaining consistent optical performance across different magnification settings, particularly in reducing variations in aberrations such as spherical and coma aberrations.
Innovation Solution
A variable magnification optical system is configured with a specific arrangement of lens groups, including a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, and a subsequent lens group, where the first and third lens groups are fixed relative to the image plane, and the spacings between adjacent lens groups are varied, adhering to certain conditional expressions to minimize aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the spacings between all lens groups are varied to achieve magnification change, then the magnification range is improved, but the variations in spherical and coma aberrations increase
Solution Approach 1:
The lens system is divided into functionally distinct groups: the first lens group (positive power) and third lens group (positive power) are fixed relative to the image plane to maintain consistent aberration correction, while the second lens group (negative power) moves to provide magnification change. This segmentation allows the system to achieve variable magnification while maintaining stable optical performance by isolating the magnification function from the aberration correction function.
2Reliability
If more lens groups are added to correct aberrations, then the optical performance is improved, but the device complexity and weight increase
Solution Approach 1:
The first and third lens groups with positive refractive power serve multiple functions: they provide the necessary positive optical power for the overall system and simultaneously act as fixed reference elements for aberration correction. By making these groups fixed relative to the image plane, they universally handle both magnification stability and aberration control, reducing the need for additional dedicated correction groups.
3Reliability
If the first and third lens groups are fixed relative to the image plane, then the variations in spherical and coma aberrations are reduced, but the mechanism complexity for varying spacings increases
Solution Approach 1:
The magnification control function is extracted and isolated to the second lens group with negative refractive power. By dedicating this single group to handle all magnification changes through its movement, the system simplifies the overall mechanism compared to coordinating movements of multiple groups. The fixed first and third groups provide stable aberration correction while the second group independently handles magnification variation.
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 effectively reduces variations in aberrations, including spherical and coma aberrations, across varying magnification settings, resulting in improved optical performance and a smaller, lighter system.
Implementation Method 1
a first lens group (G1) having positive refractive power
Implementation Method 2
a second lens group (G2) having negative refractive power
Implementation Method 3
a third lens group (G3) having positive refractive power
Data Source
AI summary
A variable magnification optical system including, in order from an object side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a subsequent lens group including a plurality of lens groups is configured so that at varying magnification, the first and third lens groups are fixed with respect to an image plane, and the spacings between adjacent lens groups are varied, and that the following conditional expression is satisfied:0.24<(TL/f1)/(ft/fw)<0.55where TL is the distance from a lens surface closest to the object side to the image plane, f1 is the focal length of the first lens group, ft is the focal length of the variable magnification optical system in a telephoto end state, and fw is the focal length of the variable magnification optical system in a wide-angle end state.