Wide-Angle Zoom Lens Aberration Correction
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Solution Overview
Problem
Wide-angle zoom lens systems with angles exceeding 80° at the short focal length extremity face challenges in correcting aberrations like distortion and astigmatism, and achieving high-speed focusing due to strong refractive power requirements, which complicates the design and increases lens diameter, making it difficult to maintain a compact form and efficient focusing.
Innovation Solution
A wide-angle zoom lens system is designed with a specific arrangement of lens groups, including a negative first lens group, a positive second lens group, and a positive third lens group, where each group moves along the optical axis during zooming, and the positive second lens group is used for focusing, employing aspherical surfaces and cemented lenses to correct aberrations and reduce lens diameter, while maintaining a compact form.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a retrofocus lens arrangement with strong refractive power is used to achieve wide-angle view and compact size, then the back focal distance is extended and overall length is reduced, but distortion, field curvature, and astigmatism cannot be sufficiently corrected
Solution Approach 1:
The lens system is divided into multiple lens groups (first lens group with negative refractive power, second lens group with positive refractive power, and additional lens elements) that work together to correct aberrations. Each lens group has specific functions: the first lens group provides the necessary negative power for wide-angle view, while the second lens group and other elements correct distortion, field curvature, and astigmatism, allowing compact size without sacrificing optical quality
Solution Approach 2:
Different regions of the lens system have different optical properties tailored to specific functions. The first lens group has strong negative refractive power for wide-angle coverage, while the second lens group has positive refractive power optimized for aberration correction. Aspherical surfaces are applied to specific lens elements where they are most effective for correcting distortion and other aberrations, rather than uniformly across all elements
2Device complexity
If the first lens group is used for focusing, then the lens structure is simple, but the focusing speed is slow and lens diameters are larger
Solution Approach 1:
The focusing function is extracted from the first lens group and assigned to the second lens group instead. This allows the first lens group to be optimized solely for providing the necessary negative refractive power for wide-angle view, while the second lens group handles focusing operations. This separation enables faster focusing speed and reduced lens diameters without compromising the overall lens structure
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 system effectively corrects aberrations over the entire zooming range, reduces aberration fluctuations during focusing, and achieves a shorter minimum photographing distance, enabling high-speed focusing with a compact and efficient lens design.
Implementation Method 1
a negative first lens group, a positive second lens group, and a positive third lens group, in this order from the object
Data Source
AI summary
A wide-angle zoom lens system includes a negative fist lens group, a positive second lens group, and a positive third lens group, in this order from the object.Upon zooming from the short focal length extremity to the long focal length extremity, each of the negative fist lens group, the positive second lens group and the positive third lens group move along the optical axis thereof while a distance between the negative fist lens group and the positive second lens group decreases, and a distance between the positive second lens group and the positive third lens group also decreases.The wide-angle zoom lens system satisfies the following condition:2.45<f3/fw<3.5 (1)whereinf3 designates the focal length of the positive third lens group; andfw designates the focal length of the entire wide-angle zoom lens system at the short focal length extremity.