Positive-Positive-Positive Lens System Aberration Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing medium telephoto or normal-type lenses face challenges in aberration correction due to the concentration of positive refractive power, leading to increased complexity and decreased Modulation Transfer Function (MTF) with a large number of lenses required, which are sensitive to assembly tolerances and prone to performance deterioration.
Innovation Solution
A lens system with a positive-positive-positive three-group configuration, where positive refractive power is distributed among three lens groups, using cemented lenses with specific refractive indices and curvatures to minimize aberrations, particularly chromatic aberration, and employing a symmetrical arrangement to reduce Petzval sum and improve MTF.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If negative refractive power is provided to the rear to diffuse light flux, then the light flux can reach the image plane, but the amount of refraction at each lens becomes large and aberration correction becomes difficult
Solution Approach 1:
The patent changes the refractive power distribution parameters by providing positive refractive power to the first and second lens groups and negative refractive power to the third lens group (reversed from conventional), while controlling the refractive power values within specific ranges to achieve both light flux diffusion and aberration correction
Solution Approach 2:
The patent uses cemented lenses composed of multiple lens elements with different refractive indices (including high refractive index glass with n≥1.75) to achieve both light flux diffusion and aberration correction simultaneously
2Object-generated harmful factors
If many lens surfaces are used to perform aberration correction, then aberration can be corrected, but the number of lenses increases and manufacturing complexity increases
Solution Approach 1:
The patent merges multiple lens elements into cemented lenses (first cemented lens with two positive lenses, second cemented lens with positive and negative lenses, third cemented lens with two negative lenses) to achieve aberration correction with fewer discrete lens elements, reducing assembly complexity
Solution Approach 2:
The patent optimizes the refractive power values and refractive indices of the lens elements within specific ranges to achieve effective aberration correction with a reduced number of lenses, controlling the overall complexity
3Object-generated harmful factors
If the number of lenses is increased to correct aberration, then aberration correction improves, but the MTF tends to fall and assembly tolerance sensitivity increases
Solution Approach 1:
The patent combines multiple lens elements into cemented lenses with specific configurations (first cemented lens: positive-positive, second cemented lens: positive-negative, third cemented lens: negative-negative) to achieve aberration correction while maintaining MTF and reducing assembly tolerance sensitivity
Solution Approach 2:
The patent controls the refractive power values within specific ranges (first lens group: 0.5-2.0, second lens group: 0.3-1.5, third lens group: -0.5 to -2.0) and uses high refractive index glass (n≥1.75) to optimize the balance between aberration correction and MTF performance
4Object-generated harmful factors
If high refractive index glass is used for cemented lenses, then aberration correction improves and compactness is achieved, but manufacturing cost increases
Solution Approach 1:
The patent specifies using high refractive index glass with n≥1.75 for the cemented lenses to achieve compactness and aberration correction, while controlling the overall lens structure to manage manufacturing costs
Solution Approach 2:
The patent uses composite lens structures with high refractive index glass combined with other glass types having different refractive indices to achieve both aberration correction and cost-effectiveness through optimized material selection
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 solution effectively corrects aberrations with a smaller number of lenses, maintains high MTF across the focusing range, and reduces manufacturing costs by using high refractive index glass for cemented lenses, while ensuring compactness and ease of assembly.
Implementation Method 1
a cemented lens composed, in order from the object side, of a lens with positive refractive power and a lens with negative refractive power
Implementation Method 2
by using a cemented lens where the distances (gaps) between surfaces do not need to be adjusted, various aberrations including chromatic aberration are corrected
Implementation Method 3
a first lens group with positive refractive power that moves during focusing; a second lens group with positive refractive power; and a third lens group with positive refractive power that is fixed and is disposed closest to an image plane side
Data Source
AI summary
A lens system (10) for image pickup includes, in order from an object side (11), a first lens group (G1) with positive refractive power that moves during focusing, a second lens group (G2) with positive refractive power that is disposed on an opposite side of a stop (St) to the first lens group and moves during focusing, and a third lens group (G3) with positive refractive power that is disposed closest to an image plane side (12) and is fixed. The third lens group includes, in order from the object side, a cemented lens (B31) composed of a lens with positive refractive power and a lens with negative refractive power. A combined focal length (f3) of the third lens group and a combined focal length (f12) of the first lens group and the second lens group satisfy a following condition: 2≤f3/f12≤200.