Extender Lens Aberration Control via Cemented Groups
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Solution Overview
Problem
Existing extender lenses for imaging systems suffer from significant spherical aberration and on-axis chromatic aberration, leading to performance degradation when inserted into master lenses, failing to meet current high image quality demands.
Innovation Solution
An extender lens configuration comprising a first lens group with positive refractive power and a second lens group with negative refractive power, specifically designed to increase the focal length of the whole lens system without changing the imaging position, by satisfying certain conditional expressions for Abbe numbers, refractive indices, and partial dispersion ratios, thereby minimizing aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional extender lens configurations are used, then the focal length is extended, but spherical aberration and on-axis chromatic aberration increase significantly
Solution Approach 1:
The patent applies parameter changes by carefully selecting and controlling the Abbe numbers (ν1p, ν1n) of the positive and negative lenses in the three-lens cemented lens, along with their refractive indices and partial dispersion ratios. By satisfying specific conditional expressions for these optical parameters, the invention achieves effective correction of on-axis chromatic aberration while maintaining the focal length extension function. The precise control of material parameters enables simultaneous reduction of both spherical and chromatic aberrations.
Solution Approach 2:
The patent employs composite materials through the three-lens cemented lens structure, which combines positive and negative lenses with different Abbe numbers and refractive indices. This composite lens design allows for chromatic aberration correction by using materials with complementary optical properties. The cemented construction of multiple lens elements with different dispersive characteristics creates a composite optical system that reduces both spherical and chromatic aberrations while extending the focal length.
2Length of moving object
If existing extender lens designs are inserted into master lens, then focal length is changed, but performance of whole lens system degrades
Solution Approach 1:
The patent uses parameter changes by establishing specific conditional expressions that govern the optical parameters of the extender lens components. By controlling the Abbe numbers, refractive indices, and focal length ratios within defined ranges, the invention ensures that the extender lens maintains high image quality when inserted into the master lens. This parameter optimization prevents performance degradation while achieving the desired focal length extension.
Solution Approach 2:
The patent converts the potential harm of aberration introduction into a benefit by deliberately designing the three-lens cemented lens with specific material properties. The combination of positive and negative lenses with different Abbe numbers, while potentially introducing complexity, actually serves to correct chromatic aberrations that would otherwise degrade performance. The design transforms what could be a source of performance degradation into a mechanism for aberration correction and image quality enhancement.
3Measurement precision
If focal length is extended without changing imaging position, then imaging position is maintained constant, but aberration control becomes more difficult
Solution Approach 1:
The patent applies parameter changes by satisfying the conditional expression -5 < f1/f1n < -0.5, which controls the ratio between the focal length of the first lens group and the focal length of the negative lens in the three-lens cemented lens. This parameter control enables the system to extend focal length while maintaining stable imaging position. Additionally, by controlling the Abbe numbers and partial dispersion ratios of the lens materials, the invention simultaneously manages aberration levels despite the constrained design requirements.
Solution Approach 2:
The patent applies local quality by creating a specialized three-lens cemented lens structure with specific local optical properties. The positive and negative lenses within the cemented assembly have locally optimized characteristics (different Abbe numbers, refractive indices) that are tailored to correct aberrations at specific positions in the optical path. This local optimization within the cemented lens structure enables aberration control while maintaining overall imaging position stability during focal length extension.
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 extends the focal length of the lens system while maintaining image quality and reducing spherical and chromatic aberrations, ensuring high performance without degrading the imaging position, thus addressing the limitations of previous extender lenses.
Implementation Method 1
a three-lens cemented lens having three lenses of a positive lens, a negative lens, and a positive lens cemented together in order from the object side
Implementation Method 2
where ν1n is an Abbe number of the negative lens constituting the three-lens cemented lens on the basis of a d line
Data Source
AI summary
An extender lens is removably inserted into a master lens, performs an increase in a focal length without changing an imaging position due to insertion, and consists of a positive first lens group and a negative second lens group in order from the object side. The first lens group consists of one or more positive lenses in order from the object side, and a three-lens cemented lens having three lenses of a positive lens, a negative lens, and a positive lens having cemented together in order from the object side. The following Conditional Expression (1) relating to an Abbe number ν1n of the negative lens of the three-lens cemented lens is satisfied:26<ν1n<40. (1):