Three-Group Optical System with Moving Focus Group for Aberration Correction
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Solution Overview
Problem
Existing fixed focal point optical systems of the inner focus type face challenges in correcting various aberrations, particularly when increased in diameter.
Innovation Solution
An optical system comprising a first lens group with positive refractive power, a second lens group with positive refractive power, and a third lens group with negative refractive power, where the second lens group moves along the optical axis, satisfying specific conditional expressions to correct aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the optical system is increased in diameter, then the collecting area is improved, but the aberration correction becomes difficult
Solution Approach 1:
The optical system is divided into three lens groups with different refractive powers arranged in sequence. The first lens group has positive refractive power, the second lens group has positive refractive power, and the third lens group has negative refractive power. This segmentation allows each group to contribute differently to aberration correction while maintaining a large collecting area.
Solution Approach 2:
The patent applies specific conditional expressions to control the optical parameters: 0.100 < BFa/f < 0.500 and -5.000 < (G1R1)/f < 500.000. By carefully adjusting these parameters, the system achieves favorable aberration correction across the entire focusing range while maintaining large aperture.
2Device complexity
If the optical system is designed for inner focus type, then the focusing mechanism is simplified, but the aberration correction deteriorates
Solution Approach 1:
The second lens group is designed to move along the optical axis during focusing, transforming the static lens arrangement into a dynamic one. This movement enables the system to maintain focus across different object distances while the three-group structure continues to provide aberration correction.
Solution Approach 2:
Each lens group is assigned specific optical characteristics: the first group provides positive refractive power, the second group (which moves) provides positive refractive power, and the third group provides negative refractive power. This local differentiation of optical properties enables simultaneous achievement of simple focusing mechanism and excellent 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
The system achieves favorable optical performance throughout the focusing range from infinity to short distances, effectively correcting astigmatism and coma aberrations.
Implementation Method 1
a first lens group having positive refractive power, a second lens group having positive refractive power, and a third lens group having negative refractive power
Data Source
AI summary
An optical system comprises a first lens group having positive refractive power, a second lens group having positive refractive power, and a third lens group having negative refractive power, arranged in order from an object side, wherein, when focusing, the second lens group moves along an optical axis, and the optical system satisfies the conditional expressions 0.100<BFa/f<0.500 and −5.000<(−G1R1)/f<500.000, where BFa is an air equivalent distance on the optical axis between a lens surface on an image side of a lens disposed closest to an image and the image, f is a focal length of the optical system, and G1R1 is a radius of curvature of a lens surface on the object side for a lens component disposed farthest on the object side in the first lens group.