Converter Lens Segmentation for Coma Aberration Control
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Solution Overview
Problem
Converter lenses with negative refractive power face challenges in increasing focal length while minimizing aberrations such as coma aberration, especially when used with off-axis light, and lack effective aberration correction due to the absence of an aperture stop.
Innovation Solution
The converter lens design includes three or more negative lenses with a specific average refractive index (1.92 < Ndave < 2.10) and a configuration that satisfies conditional equations to control lens curvature and refractive power, allowing for effective aberration correction, particularly coma aberration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the curvature of a negative lens in a converter lens is increased in order to increase the negative refractive power, then the negative refractive power is improved, but aberrations such as coma aberration due to off-axis light occur easily
Solution Approach 1:
The converter lens is divided into multiple negative lenses (first negative lens, second negative lens, third negative lens) with different curvature characteristics. The first negative lens has a first curvature and the second negative lens has a second curvature that is smaller than the first curvature, allowing distributed refractive power while reducing aberration concentration.
Solution Approach 2:
Different regions of the converter lens are assigned different optical properties. The first negative lens has higher curvature for strong refractive power near the optical axis, while the second negative lens has lower curvature to minimize aberration for off-axis light, creating local optimization of optical quality.
2Length of stationary object
If a converter lens has negative refractive power and increases focal length of an entire system, then the focal length is improved, but aberration correction becomes difficult without an aperture stop
Solution Approach 1:
The converter lens segments the aberration correction function across multiple negative lenses with different curvature characteristics. The first negative lens addresses certain aberration components while the second negative lens addresses others, collectively achieving aberration correction without requiring an aperture stop.
Solution Approach 2:
The patent optimizes specific parameters including the curvature of each negative lens, the spacing between lenses, and the refractive indices to achieve aberration correction. By carefully controlling these parameters, the system corrects aberrations while maintaining the focal length extension function.
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 design achieves high optical performance by minimizing aberrations and enabling the use of master lenses with both low and high maximum image heights without a feeling of strangeness, even when used with imaging devices having high maximum image heights.
Implementation Method 1
a converter lens having negative refractive power and increasing a focal length of an entire system when arranged on an image side of a master lens
Implementation Method 2
a first lens unit having positive refractive power; and a second lens unit having negative refractive power
Data Source
AI summary
A converter lens includes three or more negative lenses and increases the focal length of an entire system, in which an average refractive index Ndave at the d-line (wavelength of 587.56 nm) of a material of all the negative lenses included in the converter lens is defined.