Compact Retrofocus Lens Design for Wide-Angle Imaging
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Solution Overview
Problem
Existing retrofocus imaging lenses face challenges in achieving both a reduction in size and an increase in the angle of view while maintaining effective aberration correction.
Innovation Solution
A compact retrofocus imaging lens design comprising a first group with negative refractive power, a second group with positive refractive power, a third group with three lenses forming a compound lens, and a fourth group with a positive aspherical lens, arranged in a specific order to achieve a wide angle of view of 120 degrees or more, with focal length ratios restricted by conditional expressions to balance refractive powers and correct aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a retrofocus imaging lens is designed with a larger diameter and smaller F-number to achieve higher resolution and wider angle of view, then the imaging performance is improved, but the overall size of the lens increases
Solution Approach 1:
The imaging lens is divided into four distinct groups (first group with negative power, second group with positive power, third group with positive power, and fourth group with positive power). Each group contains specific numbers of lenses (at least two negative lenses in first group, one positive lens in second group, three lenses in third group with at least two joined as compound lens, one aspherical positive lens in fourth group). This segmentation allows independent optimization of each group's function while maintaining overall compactness and achieving wide angle of view (120 degrees or more) with controlled lens size.
2Adaptability or versatility
If the angle of view is increased to 120 degrees or more to capture wider field of view, then the coverage area is improved, but the distortion and aberration correction becomes more difficult
Solution Approach 1:
The fourth group includes a positive lens with an aspherical surface, which provides localized aberration correction capability specifically tailored for wide-angle applications. The aspherical surface shape is optimized to correct distortion and other aberrations that become prominent at 120 degrees or more angle of view, while the other groups maintain spherical surfaces for basic focusing and light gathering functions.
Solution Approach 2:
The third group includes a compound lens formed by joining at least two lenses together. This composite lens structure combines different optical materials and surface curvatures to achieve aberration correction that would be difficult to obtain with a single lens, particularly important for maintaining image quality across the wide 120-degree field of view.
3Measurement precision
If multiple lens groups are added to achieve wide angle of view and correct aberrations, then the optical performance is improved, but the number of components and device complexity increases
Solution Approach 1:
The third group combines three lenses (two positive and one negative) with at least two of them joined together to form a compound lens. This merging approach integrates multiple optical functions into a single grouped structure, reducing the overall number of separate lens groups while maintaining the necessary aberration correction capabilities for wide-angle imaging.
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 achieves a compact retrofocus imaging lens with a wide angle of view of 120 degrees or more, effectively correcting spherical, astigmatism, and distortion aberrations, suitable for various camera applications while maintaining a small size and high performance.
Implementation Method 1
The fourth group includes one positive lens having an aspherical shape
Implementation Method 2
The third group includes three lenses of two positive lenses and one negative lens. At least two of the three lenses of the third group are joined together to form a compound lens
Implementation Method 3
The first group includes at least two negative lenses
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
An imaging lens (IM) includes a first group (G1), a second group (G2), an aperture stop (AS), a third group (G3), and a fourth group (G4). The first group (G1) includes at least two negative lenses. The second group (G2) includes one positive lens. The third group (G3) includes two positive lenses and one negative lens. At least two of the third group (G3) are joined together to form a compound lens. Conditional expressions (1), (2), (3), and (4) below are satisfied: (1) -2.7 ≤ f1 / f ≤ -0.7 (2) 2.2 ≤ f2 / f ≤ 6.6 (3) 3.9 ≤ f3 / f ≤ 14.3 (4) 2.8 ≤ f4 / f ≤ 11.0 where fi denotes focal length of i-th group with respect to d-line, i denotes one of 1 to 4, and f denotes focal length of an entirety of the imaging lens with respect to the d-line.