Retrofocus Wide-Angle Lens System Miniaturization
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Solution Overview
Problem
Retrofocus wide-angle lens systems face challenges in miniaturization while maintaining a long back focal distance, and effectively correcting aberrations such as distortion, chromatic aberration, and spherical aberration, especially when trying to shorten the lens system while preserving optical performance.
Innovation Solution
A wide-angle lens system design featuring a negative front lens group and a positive rear lens group, with specific focal length ratios and arrangements of cemented lens elements, including aspherical surfaces, to achieve a compact form while correcting aberrations and maintaining a 70° angle-of-view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a retrofocus lens system is designed with a negative front lens group and positive rear lens group to achieve a long back focal distance, then the back focal distance is increased, but the overall lens length increases and miniaturization becomes difficult
Solution Approach 1:
The lens system is divided into distinct functional groups: a negative front lens group (with sub-groups having different refractive powers) and a positive rear lens group (with cemented elements). This segmentation allows each group to be optimized independently for its specific function while contributing to the overall compact design.
Solution Approach 2:
The patent employs a nested arrangement where the diaphragm is positioned within the lens system structure, and cemented lens elements are integrated closely together. The negative front lens group and positive rear lens group are arranged in a compact nested configuration that minimizes overall length while maintaining the required back focal distance.
2Length of moving object
If the lens system is miniaturized by reducing the number of elements and distances, then the lens length is shortened, but aberration correction (especially distortion and chromatic aberration) deteriorates
Solution Approach 1:
Different regions of the lens system are assigned specific optical properties: the negative front lens group (with specific sub-groups) addresses distortion and chromatic aberration, while the positive rear lens group (with cemented elements of specific refractive indices and Abbe numbers) corrects spherical aberration and other off-axis aberrations. This local optimization ensures comprehensive aberration correction in a compact design.
Solution Approach 2:
The patent uses cemented lens elements with specifically selected glass materials having different refractive indices and Abbe numbers. This composite approach combines materials with complementary optical properties to achieve superior aberration correction, particularly chromatic and spherical aberrations, within the constrained compact structure.
3Reliability
If cemented lens elements are used in the positive rear lens group to correct spherical aberration and chromatic aberration, then aberration correction is improved, but manufacturing complexity increases
Solution Approach 1:
Multiple lens elements are cemented together to form integrated units in the positive rear lens group. This merging of elements reduces the number of separate air-glass interfaces, simplifies alignment requirements, and decreases the overall number of components that need to be handled during assembly, thereby reducing manufacturing complexity while maintaining aberration correction performance.
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 design results in a high-quality, miniaturized retrofocus wide-angle lens system with improved correction of aberrations and a 70° angle-of-view, effectively addressing the challenges of miniaturization and optical performance.
Implementation Method 1
The positive rear lens group includes cemented lens elements having a positive lens element, a negative lens element and a positive lens element
Implementation Method 2
an aspherical surface is formed in the final lens element of the positive rear lens group
Data Source
AI summary
A wide-angle lens system includes a negative front lens group and a positive rear lens group, in this order from the object.The negative front lens group includes a negative first sub-lens group and a positive second sub-lens group, in this order from the object.The positive rear lens group includes cemented lens elements having a positive lens element, a negative lens element and a positive lens element.The wide-angle lens system satisfies the following conditions:−0.8<fla/flb<−0.2 (1)0.7<f/fR<1.1 (2)whereinfla designates the focal length of the negative first sub-lens group;flb designates the focal length of the positive second sub-lens group;f designates the focal length of the entire wide-angle lens system; andfR designates the focal length of the positive rear lens group.