Zoom Lens Aberration Control via Segmented Five-Unit Design
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Solution Overview
Problem
Existing zoom lenses with a five-unit configuration face challenges in maintaining high optical performance across the zoom range, particularly at the telephoto end where aberrations such as spherical aberration and coma increase with reduced f-number, and at the wide-angle end where astigmatism and lateral chromatic aberration increase with increased angle of view.
Innovation Solution
A zoom lens configuration with a first positive refractive power unit, a second negative refractive power unit, a third positive refractive power unit with four or more lenses and air gaps between specific lenses, and a fourth negative refractive power unit, where the movement of the first lens unit during zooming is optimized to maintain high zoom ratio and correct aberrations, while the third lens unit with a positive and negative lens arrangement corrects spherical and lateral chromatic aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the focal length at telephoto end is increased to increase zoom ratio, then the zoom ratio is improved, but various aberrations such as spherical aberration, astigmatism, and chromatic aberration are increased
Solution Approach 1:
The lens system is divided into five lens units with different refractive powers arranged in sequence. Each unit is optimized for specific aberration correction: the first unit (positive) corrects spherical aberration, the second unit (negative) corrects chromatic aberration, the third unit (positive) corrects astigmatism, the fourth unit (negative) corrects lateral chromatic aberration, and the fifth unit (positive or negative) provides additional correction. This segmentation allows the system to achieve high zoom ratio while controlling aberrations across the entire zoom range.
Solution Approach 2:
Each lens unit is designed with specific local optical characteristics tailored to correct particular aberrations at specific zoom positions. The refractive powers and configurations of individual units are optimized locally for their specific correction functions, enabling the overall system to maintain high optical performance across the extended zoom range without compromising any single aspect of aberration control.
2Illumination intensity
If the f-number is reduced for brightness, then the aperture ratio is improved, but spherical aberration and coma are increased at the telephoto end
Solution Approach 1:
The lens system segments aberration correction across multiple units: the first lens unit (positive refractive power) is specifically designed to correct spherical aberration, while the fourth lens unit (negative refractive power) corrects coma. This distributed correction approach allows the system to maintain large aperture ratio for brightness while controlling spherical aberration and coma at the telephoto end through the coordinated action of specialized lens units.
3Area of stationary object
If the angle of view is increased, then the wide-angle end performance is improved, but astigmatism and lateral chromatic aberration are increased
Solution Approach 1:
The lens system assigns specific correction functions to different units: the third lens unit (positive refractive power) is optimized to correct astigmatism, while the fourth lens unit (negative refractive power) corrects lateral chromatic aberration. This segmented approach enables the system to achieve wide angle of view while maintaining control over astigmatism and lateral chromatic aberration through the specialized optical design of individual units.
4Area of stationary object
If the front lens diameter is increased to increase angle of view, then the angle of view is improved, but the lens size and mass are increased
Solution Approach 1:
The lens system divides the optical function across five units with different refractive powers, allowing each unit to be smaller in diameter than a single-lens system would require. The first unit (positive) and second unit (negative) work together to provide wide angle of view while keeping individual lens diameters compact. This segmentation enables the system to achieve wide angle of view without proportionally increasing overall lens size and mass.
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 various aberrations across the zoom range, maintaining high optical performance and allowing for a compact design while suppressing increases in size and mass, thereby achieving a high zoom ratio and large aperture ratio.
Implementation Method 1
a first lens unit having a positive refractive power; a second lens unit having a negative refractive power; a third lens unit having a positive refractive power; a fourth lens unit having a negative refractive power; and a fifth lens unit having a positive or negative refractive power, in which intervals between adjacent lens units are changed during zooming
Implementation Method 2
a lens arranged closest to the image side, a lens arranged second when counted from the image side, and a lens arranged third when counted from the image side are arranged with air gaps therebetween
Data Source
AI summary
Provided is a zoom lens, including, in order from an object side to an image side: first to fourth lens units respectively having positive, negative, positive and negative refractive powers; and a fifth lens unit having a positive or negative refractive power. In the zoom lens, intervals between adjacent lens units are changed during zooming. The third lens unit includes four or more lenses, and in the third lens unit, a lens arranged closest to the image side, a lens arranged second when counted from the image side, and a lens arranged third when counted from the image side are arranged with air gaps therebetween. A focal length of the zoom lens at a telephoto end, and a movement amount of the first lens unit during zooming from a wide-angle end to the telephoto end are set appropriately.