Conversion Lens Positive Element Abbe Number Control
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Solution Overview
Problem
Existing conversion lenses for optical apparatuses face challenges in correcting chromatic aberration of magnification and field curvature, particularly when inserted between a master lens and the main unit of an imaging device, due to limitations in refractive power and material properties.
Innovation Solution
A conversion lens with a negative refractive power is designed, incorporating a positive lens with specific refractive index and Abbe number ranges to correct chromatic aberration and field curvature, using highly-dispersive optical materials with low partial dispersion ratios and small refractive indices to achieve achromatization and minimize secondary spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a conversion lens with negative refractive power is inserted to increase focal length, then the focal length of the entire lens system is increased, but chromatic aberration of magnification and field curvature deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the Abbe number (30≤νd≤40), refractive index (1.225≤[nd−(14.387/νd)]≤1.276), and partial dispersion ratio (0.4300≤[θgF−(2.9795/νd)]≤0.5010) of the positive lens material to achieve optimal correction of chromatic aberration and field curvature while maintaining negative refractive power for focal length extension
Solution Approach 2:
The patent uses composite optical materials by combining specific glass types (e.g., LaK15, LaK16, LaK17 from Ohara Inc.) that exhibit negative anomalous partial dispersibility, creating a positive lens with unique dispersion properties that simultaneously correct multiple types of aberrations
2Manufacturing precision
If conventional optical materials are used in the positive lens, then material availability is good, but chromatic aberration of magnification cannot be effectively corrected
Solution Approach 1:
The patent specifies precise parameter ranges for Abbe number (30≤νd≤40), refractive index combinations (1.225≤[nd−(14.387/νd)]≤1.276), and partial dispersion ratios (0.4300≤[θgF−(2.9795/νd)]≤0.5010) to identify suitable conventional glass materials that can achieve superior chromatic aberration correction
Solution Approach 2:
The patent applies local quality by selecting optical materials with specific local dispersion characteristics (negative anomalous partial dispersibility) for the positive lens, where the material's partial dispersion ratio θgF is specifically optimized to correct chromatic aberration of magnification in the blue-green wavelength region
3Manufacturing precision
If the positive lens parameters are optimized for chromatic aberration correction, then image quality improves, but the lens system becomes more complex
Solution Approach 1:
The patent optimizes image quality by precisely controlling material parameters (Abbe number, refractive index, partial dispersion ratio) of the positive lens rather than increasing the number of lens elements, thereby correcting chromatic aberration and field curvature without significantly increasing structural complexity
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 chromatic aberration of magnification and field curvature, allowing for improved image quality and miniaturization of the conversion lens, while maintaining environmental resistance and hardness.
Implementation Method 1
a positive lens, wherein the following conditional expressions are satisfied, 30≤νd≤40, 1.225≤[nd−(14.387/νd)]≤1.276, and 0.4300≤[θgF−(2.9795/νd)]≤0.5010, where νd is an Abbe number of the positive lens, θgF is a partial dispersion ratio of the positive lens for g-line and F-line, and nd is a refractive index of the positive lens for d-line
Implementation Method 2
The solution effectively corrects chromatic aberration of magnification and field curvature, allowing for improved image quality and miniaturization of the conversion lens
Data Source
AI summary
A conversion lens having a negative refractive power includes a positive lens GP. The positive lens GP satisfies all the following conditional expressions:30≤νd≤40,1.225≤[nd−(14.387/νd)]≤1.276, and0.4300≤[θgF−(2.9795/νd)]≤0.5010,where νd is an Abbe number of the positive lens GP, θgF is a partial dispersion ratio of the positive lens GP for g-line and F-line, and nd is a refractive index of the positive lens GP for d-line.