|Lens Form||Positive/Negative meniscus Lens||Material||BK7, Fused Silica, CaF2, BaF2, MgF2, ZnSe, GaAs, Ge, Sapphire, Etc.|
|Diameter Range||1mm -300mm||Diameter Tolerance||+0.0/-0.1mm|
|Clear Aperture||>90%||Thickness Tolerance||±0.1mm|
|Focal Length Tolerance||±2%||Surface Quality||40/20 S/D|
|Irregularity||λ/4 @ 633 nm (λ/8 optional)||Centering||2 arc min|
A Meniscus Lens, or a Convex-concave Lens is an optical lens consisting of one concave and one convex side, and the two sides have different radii of curvature according which the meniscus lenses could be categorized into two kinds: positive meniscus lenses and negative meniscus lenses.
A Positive Meniscus Lens is more curved on the convex side than on the concave side, and its edge thickness is greater than its central thickness, contributing to a positive focal length. In contrast, a Negative Meniscus Lens is more curved on the concave side than on the convex side, and its central thickness is greater than its edge thickness, contributing to a negative focal length. Positive Meniscus Lenses converge light is utilized to reduce the focal length when used in conjunction with other lenses and increase the numerical aperture (NA) of existing optical modules without introducing significant spherical aberration. These functions are quite useful for image instruments to increase the resolution, and for focusing lasers to shrink the spot diameter when the incident beam width is rather large, providing diffraction-limited performance and better precision for laser processing. A negative meniscus lens diverges light and functions in just the opposite manner as a positive meniscus lens, to increase the focal length, reduce the NA of the optical assemblies, and expand beams.
Hangzhou Shalom EO offers Custom Positive and Negative Meniscus Lenses made from a wide assortment of materials, including Fused Silica, N-BK7, Chalcogenide Glass, Germanium, GaAs, ZnSe, Baf2/CaF2/MgF2, Sapphire, etc. Diameters from 1.0mm to 300mm are available. Custom coating options include uncoated substrates, Broadband Anti-reflection (BBAR) coatings that cut to a significant extent the reflection (average reflection below 0.5%) over a certain wavelength range, and V-coating which provides higher transmission (average reflection below 0.25%) at a narrower range, and low-cost MgF2 AR coatings (average reflection below 1.5%). The different transmission wavelength ranges of the coatings could be selected according to your requirements. While other specifications could all be tailored for you.
Note that when using a positive meniscus lens to converge light, the convex side should point to the incident light source. While for negative meniscus lenses to the concave side should point to the incoming light.
Common Applications of Meniscus Lenses:
1. Integration into Infrared Lens Assemblies
In particular, for infrared lens modules, meniscus lenses are an attractive candidate because infrared optical materials tend to have larger refractive indexes (e.g. the refractive index of germanium is 4), denoting that spherical aberration would be more severe, and in this sense, a meniscus germanium lens is more advantageous than a plano-convex or plano-concave one, as it induces low levels of spherical aberration, and the entire design could be simplified with the exemption of additional lenses for correction of aberrations.
2. Focusing lenses for CO2 Laser
The CO2 laser is often utilized for laser processing (cutting, engraving, etc.), and a more intensified and contracted focus spot helps to increase the beam qualities and processing precision. ZnSe and GaAs meniscus lenses for CO2 laser focusing are available in Shalom EO.
Positive Meniscus Lenses:
Negative Meniscus Lenses: