Imaging Lens Material Pairing for Small F-Number Aberration Correction
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Solution Overview
Problem
Existing imaging lenses struggle to achieve a small F number while satisfactorily correcting various aberrations.
Innovation Solution
The imaging lens design includes a first lens group with positive refractive power and a second lens group where the distance between them changes during focusing, with a stop positioned closer to the image side than the second lens from the object side, and specific refractive index and Abbe number conditions are met for LA and LB positive lenses to balance aberration correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the F number is reduced to increase light intake, then illumination intensity improves, but aberration correction becomes difficult
Solution Approach 1:
The patent applies local quality by using different glass materials with specific refractive indices and Abbe numbers for different lens elements. The LA positive lens uses material with 1.86≤NdA<2.2 and 10≤vdA<35, while the LB positive lens uses material with 1.45≤NdB<1.70 and 57≤vdB<105. This localized material differentiation enables effective aberration correction across the lens system while maintaining a small F number for sufficient light intake.
Solution Approach 2:
The patent employs composite materials by combining multiple lens elements made from different glass materials with complementary optical properties. The combination of LA positive lenses (high refractive index, moderate Abbe number) and LB positive lenses (lower refractive index, high Abbe number) creates a composite optical system that corrects both spherical and chromatic aberrations simultaneously, enabling small F number design with satisfactory aberration correction.
2Object-affected harmful factors
If more lens elements are added to correct aberrations, then aberration correction improves, but device complexity increases
Solution Approach 1:
The patent achieves effective aberration correction with relatively few lens elements by carefully controlling material parameters. The conditional expressions for refractive index (NdA, NdB) and Abbe number (vdA, vdB) define optimal material ranges that maximize aberration correction efficiency. By changing and optimizing these material parameters within specific ranges, the patent corrects aberrations with a compact lens configuration rather than adding numerous elements.
Solution Approach 2:
The LA and LB positive lenses serve multiple functions simultaneously: they provide positive refractive power for focusing, correct spherical aberration through their specific refractive indices, and correct chromatic aberration through their complementary Abbe numbers. This multi-functionality allows the patent to achieve comprehensive aberration correction with a compact lens structure, reducing overall device complexity.
3Manufacturing precision
If high refractive index materials are used to reduce lens curvature, then manufacturing precision improves, but chromatic aberration increases
Solution Approach 1:
The patent introduces LB positive lenses with high Abbe number materials (57≤vdB<105) as intermediary elements to counteract the chromatic aberration introduced by LA positive lenses with high refractive index materials (1.86≤NdA<2.2). The LB lenses act as mediators that compensate for the dispersion effects, enabling the use of high refractive index materials for better manufacturing precision without suffering from increased chromatic aberration.
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
This design achieves a small F number with effective correction of aberrations, particularly chromatic aberrations, while maintaining a compact lens configuration and reducing weight.
Implementation Method 1
a first lens group G1 having a positive refractive power; and a second lens group G2 having a refractive power
Implementation Method 2
a stop St is disposed closer to the image side than a lens which is second from the object side
Data Source
AI summary
An imaging lens includes a positive first lens group and a second lens group, which are continuous in order from the position closest to the object side, as lens groups. During focusing, the distance between the first lens group and the second lens group changes. A stop is disposed closer to the image side than a lens which is second from the object side. A combined refractive power of all lenses closer to the object side than the stop is positive. The imaging lens includes an LA positive lens and an LB positive lens that satisfy a predetermined conditional expression at a position closer to the object side than the stop. An Abbe number of the LB positive lens is the maximum among Abbe numbers of all positive lenses closer to the object side than the stop.