Superwide-Angle Lens System Aberration Correction
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Solution Overview
Problem
Superwide-angle lens systems for mirrorless cameras face challenges in achieving high optical quality while minimizing size and cost, as increasing lens elements enlarges the system and reducing them deteriorates image quality, and existing designs struggle with temperature-induced focal shifts and insufficient angle-of-view due to small refractive power and plastic lens durability issues.
Innovation Solution
A superwide-angle lens system configuration with a negative first lens group including a negative meniscus lens element and a positive lens element, followed by a cemented positive second lens group, satisfying specific conditions for focal length ratios, shaping factors, and refractive indices to correct aberrations and maintain optical quality without requiring long backfocus, thereby achieving miniaturization and low cost with high practical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the number of lens elements is increased to attain higher optical quality, then the optical quality is improved, but the size of the entire lens system is enlarged and the overall cost increases
Solution Approach 1:
The patent applies parameter changes by carefully controlling the refractive powers, focal lengths, and spacing of a limited number of lens elements (5 elements total) to achieve high optical quality. Specifically, the first lens group uses a negative meniscus lens with convex surface on object side having refractive power between -1.0 and -0.5, and the second lens group uses a positive meniscus lens with convex surface on object side having refractive power between 1.5 and 2.5, optimizing the system without increasing element count
Solution Approach 2:
The patent employs composite lens design by combining different types of lens elements (negative meniscus, positive meniscus, biconvex, biconcave) with different refractive indices and dispersion properties in a multi-group configuration. This allows correction of various aberrations using fewer elements through the synergistic effect of different optical materials and designs
2Volume of moving object
If the number of lens elements is reduced to miniaturize and reduce cost, then the size and cost are reduced, but the optical quality deteriorates
Solution Approach 1:
The patent achieves high optical quality with only 5 lens elements by precisely controlling key parameters: the focal length ratio f1/f between -1.45 and -1.15, the shaping factor SF2 of the negative meniscus lens between 1.8 and 2.5, and the refractive index nd1 of the first negative meniscus lens between 1.7 and 1.9. These parameter optimizations maximize the effectiveness of each element
Solution Approach 2:
The patent applies local quality by giving specific optical characteristics to specific lens elements and groups. The first lens group (negative) is designed with specific meniscus lenses for wide-angle correction, while the second lens group (positive) uses different lens configurations for focus and aberration control, with each element having tailored refractive indices, curvatures, and positions to optimize overall performance
3Ease of manufacture
If plastic lens elements are used to reduce cost and achieve aspherical surfaces, then cost is reduced and design performance is improved, but a large amount of focal shift occurs upon temperature change causing variations in optical quality
Solution Approach 1:
The patent selects glass materials with specific refractive indices (nd1 between 1.7-1.9 for the first negative meniscus lens, nd2 between 1.6-1.8 for the second negative meniscus lens) and appropriate Abbe numbers to achieve thermal stability. These material parameter selections minimize thermal expansion effects and focal shift, maintaining optical quality across temperature variations
Solution Approach 2:
The patent uses composite material design by combining different glass types with complementary thermal and optical properties in the lens groups. The selection of glass materials with matched thermal expansion coefficients and refractive index temperatures compensates for thermal effects, providing reliable optical performance in varying environmental conditions
4Manufacturing precision
If the refractive power of negative lens elements is kept small to maintain balance, then aberration correction is improved, but the angle-of-view cannot be sufficiently widened
Solution Approach 1:
The patent achieves wide angle-of-view (160 degrees or more) by optimizing the refractive power parameters within specific ranges: the first negative meniscus lens has refractive power between -1.0 and -0.5, the second negative meniscus lens has refractive power between -1.5 and -1.0, and the positive lens has refractive power between 1.0 and 1.5. These parameter optimizations balance wide-angle performance with aberration correction
Solution Approach 2:
The patent segments the optical system into distinct functional groups: the first lens group with negative meniscus lenses for wide-angle divergence control, the aperture diaphragm for light control, and the second lens group with positive meniscus and biconvex lenses for focus and aberration correction. This segmentation allows each group to be optimized for its specific function while working together to achieve both wide angle-of-view and good aberration correction
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 configuration allows for a high design performance with a 160-degree angle-of-view, effectively correcting coma, field curvature, and spherical aberrations, maintaining optical quality across temperature variations without the need for aspherical surfaces, thus achieving superior optical quality and cost-effectiveness.
Implementation Method 1
The first lens group is provided with a negative meniscus lens element having a convex surface on the object side, a negative meniscus lens element having a convex surface on the object side, and a positive lens element, in that order from the object side. The second lens group is provided with a cemented lens having a negative lens element and a positive lens element; and a positive lens element, in that order from the object side.
Implementation Method 2
The second lens group is provided with a cemented lens having a negative lens element and a positive lens element
Data Source
AI summary
A superwide-angle lens system includes a negative first lens group, an aperture diaphragm, and a positive second lens group. The first lens group includes two negative meniscus lens elements, and a positive lens element. The second lens group includes a cemented lens having negative and positive lens elements; and a positive lens element. The following conditions (1) and (2) are satisfied: -1.45<f12/f<-1.15(1) 1.4<SF2<2.4(2) f12: the combined focal length of the two the negative meniscus lens elements in the first lens group, f: the focal length of the lens system, SF2: the shaping factor of the negative meniscus lens element on the image side in the first lens group.