A meniscus lens is a lens with two spherical surfaces, convex on one side and concave on the other. The lens provides a smaller beam diameter to reduce beam waste and spherical aberration. When one meniscus is combined with another lens, the focal length is shortened and the numerical aperture of the system is increased. This reduces image distortion and improves image resolution.
There are two types of meniscus lenses:
● Positive meniscus lens
The positive meniscus lens is used for applications requiring small focal numbers (less than 2.5). For focal lengths between 2.5 and 10, a meniscus lens minimizes spot size and improves image quality. The concave side curvature of a positive lens is smaller and the convex side curvature is larger.
Frequently used for beam focusing applications
Minimizes the increase in spherical aberrations for multi-element systems
● Negative meniscus lens
The negative meniscus lens is used for applications using infrared materials with a high refractive index. These lenses serve as substitutes for other negative lenses with greater curvature on the concave side and less curvature on the convex side. They are used in beam spreading applications where minimal spherical aberration is required.
Frequently used for beam expanding applications
Minimizes the increase in spherical aberrations for multi-element systems
Parameters
Material | Optical Glass |
Surface Flatness | < λ/5 @ 633nm |
Scratch/Dig | < 40/20 (both sides) |
Eccentricity | ≤ 1arcmin |
Focal Length Tolerance | < ± 1% |
Diameter Tolerance | < + 0.00/ - 0.02mm |
Thickness Tolerance | < ± 0.05 |
Clear Aperture | ≥ 95% of diameter |
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