Zoom Lens Aberration Correction via Dispersion Control
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Solution Overview
Problem
Conventional zoom lenses with high zoom ratios face challenges in achieving both high optical performance and effective aberration correction, particularly at the telephoto end, due to significant chromatic aberration and other optical errors.
Innovation Solution
A four-unit zoom lens configuration with specific settings for the second lens unit, including a combination of positive and negative lenses with optimized Abbe numbers and relative partial dispersion, to correct chromatic aberration and maintain high optical performance across the zoom range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the zoom ratio is increased to achieve high zoom ratio of 100 or more, then the versatility and functionality of the zoom lens is improved, but chromatic aberration and other optical errors increase significantly
Solution Approach 1:
The zoom lens is divided into four distinct lens units (first through fourth lens units) with different refractive powers and dispersion characteristics. Each lens unit is independently configured to address specific aberration types, allowing the system to achieve high zoom ratio while correcting chromatic aberration through coordinated movement and design of individual segments.
Solution Approach 2:
The patent employs lens elements with different dispersion characteristics (positive and negative lenses with specific Abbe numbers) within the second lens unit. This composite approach combines materials with anomalous dispersion properties to correct chromatic aberration while maintaining the high zoom ratio functionality, effectively resolving the contradiction between versatility and optical quality.
2Device complexity
If conventional lens configurations are used to achieve high zoom ratio, then the structural complexity is reduced, but optical performance deteriorates due to large variation of aberrations
Solution Approach 1:
The second lens unit is specifically configured with a particular arrangement of positive and negative lenses having optimized Abbe numbers and relative partial dispersion values. This localized optimization of lens properties in the critical second unit allows effective aberration correction during zooming while maintaining overall structural feasibility.
Solution Approach 2:
The patent specifies precise parameter ranges for the second lens unit, including the Abbe number (ν) and relative partial dispersion (θ) of lens materials, as well as focal length ratios and spacing relationships. By controlling these parameters within defined ranges, the system achieves stable optical performance across the zoom range without excessive structural complexity.
3Ease of manufacture
If the second lens unit configuration is not optimized, then the ease of manufacture is improved, but manufacturing precision of optical performance is compromised due to large aberration variation
Solution Approach 1:
The second lens unit is designed to move along the optical axis during zooming operations, with its position dynamically adjusted to maintain optimal aberration correction across different focal lengths. This dynamic configuration allows the lens to achieve high optical performance throughout the zoom range while using a manageable number of moving components.
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 reduces and corrects chromatic aberration, achieving high optical performance and a high zoom ratio of 100 or more, while minimizing residual secondary spectrum and axial chromatic aberration at the telephoto end.
Implementation Method 1
a large amount of chromatic aberration of magnification (lateral chromatic aberration) and axial chromatic aberration (longitudinal chromatic aberration) may occur at the zoom position close to the telephoto end
Implementation Method 2
a second lens unit having a negative refractive power, in which at least one positive lens and at least one negative lens are arranged
Data Source
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AI summary
A zoom lens includes, in order from an object side to an image side, a first lens unit (U1) having a positive refractive power, a second lens unit (U2) having a negative refractive power and configured to move during zooming, a third lens unit (U3) having a positive refractive power and configured to move during zooming, and a fourth lens unit (U4) having a positive refractive power and configured not to move for zooming. In the zoom lens, the second lens unit includes at least one positive lens and at least one negative lens. Furthermore, in the zoom lens, average values of Abbe number (v) and relative partial dispersion (θ) of materials of the at least one negative lens (νma, θna) and average values of Abbe number (v) and relative partial dispersion (θ) of materials of the at least one positive lens (νpa, θpa) satisfy an appropriate condition.