Compact Zoom Lens Unit with Aberration Control
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Solution Overview
Problem
Existing zoom lens units fail to achieve a balance between compactness, wide angle, high magnification ratio, and effective aberration correction, particularly with magnification ratios below 10 times and half-field angles less than 38 degrees, leading to insufficient performance for modern imaging demands.
Innovation Solution
A zoom lens unit design comprising a first positive refracting lens group, a second negative refracting lens group, a third lens group with specific positive lenses satisfying a partial dispersion ratio formula, and a fourth positive refracting lens group, where all lens groups move during magnification changes, optimizing the Abbe number and partial dispersion ratio of the third lens group's positive lenses to reduce chromatic aberration and improve image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the magnification ratio is increased to meet user demand for high magnification, then the magnification ratio improves, but the total length of the zoom lens unit at telephoto end increases, reducing compactness
Solution Approach 1:
The zoom lens unit is divided into four distinct lens groups (first positive, second negative, third positive, fourth positive) that can move independently relative to each other. This segmentation allows each group to contribute differently to magnification changes, enabling high magnification ratio (9.5 times) while maintaining compact total length through coordinated movement of segmented groups rather than uniform extension.
Solution Approach 2:
The patent employs a complex multi-dimensional movement scheme where lens groups move not only along the optical axis but also with varying intervals between them. The interval between first and second lens groups increases, while interval between second and third decreases, creating a non-linear spatial arrangement that achieves high magnification without proportional increase in overall length.
2Adaptability or versatility
If the half-field angle is increased to achieve wide angle performance, then the half-field angle improves, but the telephoto ratio increases, reducing compactness
Solution Approach 1:
The third lens group is specifically designed with at least two positive lenses and one negative lens, creating local optical quality variations within that group. This localized configuration optimizes wide-angle performance (half-field angle 40 degrees) by concentrating corrective elements in the third group, allowing wide angle achievement without requiring proportional increase in telephoto ratio.
Solution Approach 2:
The patent optimizes specific optical parameters including the Abbe number and partial dispersion ratio of positive lenses in the third lens group. By controlling these parameters and satisfying specific conditional expressions, the system achieves wide-angle performance while maintaining compact telephoto ratio, resolving the contradiction between field angle and compactness.
3Adaptability or versatility
If the zoom lens unit is designed for high magnification ratio, then the magnification ratio improves, but the aberration correction becomes more difficult
Solution Approach 1:
The second lens group with negative refracting power acts as an intermediary element between the positive first and third lens groups. This negative group mediates the optical paths, helping to correct aberrations introduced by the high-magnification positive groups. The coordinated movement of this intermediary group during zooming maintains aberration correction across the full magnification range.
Solution Approach 2:
The patent uses composite lens structures within lens groups, combining multiple lens elements with different optical properties (positive and negative lenses in third group, various glass materials with different Abbe numbers). This composite approach allows sophisticated aberration correction while maintaining high magnification ratio, as each material contributes different corrective capabilities.
4Adaptability or versatility
If the zoom lens unit is designed for wide angle performance, then the half-field angle improves, but the aberration correction particularly for chromatic aberration becomes more difficult
Solution Approach 1:
The patent explicitly controls the Abbe number and partial dispersion ratio parameters of positive lenses in the third lens group by satisfying specific conditional expressions. This parameter optimization directly addresses chromatic aberration correction, allowing wide-angle performance (40-degree half-field angle) to be achieved while maintaining effective chromatic aberration control through carefully selected glass materials.
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 provides a compact zoom lens unit with a half-field angle of 38 degrees or more and a magnification ratio of 9 times or more, achieving complete aberration correction and high resolution suitable for high-resolution imaging elements, while reducing material costs and enhancing glass material selection flexibility.
Implementation Method 1
a third lens group having a positive refracting power... all the positive lenses of the third lens group satisfy the following formula: −0.005865νd3p+0.93226gF3pd3p+0.95226 where, νd3p represents an Abbe number of each of the positive lenses of the third lens group, and θgF3p represents a partial dispersion ratio
Data Source
AI summary
A zoom lens unit, including in order from an object side to an image side: a first lens group having a positive refracting power; a second lens group having a negative refracting power; a third lens group having a positive refracting power; and a fourth lens group having a positive refracting power, an aperture stop being disposed on an object side of the third lens group, wherein the third lens group has at least two positive lenses and one negative lens, wherein all the positive lenses of the third lens group satisfy the following formula: (1) −0.005865&ngr;d3p+0.93226<&thetas;gF3p<−0.005865&ngr;d3p+0.95226, where, &ngr;d3p represents an Abbe number of each of the positive lenses of the third lens group, and &thetas;gF3p represents a partial dispersion ratio of each of the positive lenses of the third lens group, defined by the formula: &thetas;gF3p=(ng−nF)/(nF−nC).