Meniscus lenses are optical lenses that produce a smaller focal point and fewer aberrations than a standard plano-convex lens. Meniscus lenses have one convex and one concave surface with each surface having its own radius or curvature. Applications include lasers and cameras.

Types of Meniscus Lenses

There are two types of meniscus lenses.

Positive Meniscus: Positive meniscus lenses have a shorter radius of curvature on the convex side and a longer radius of curvature on the concave side; the edges of these lenses are thicker than the center. A positive meniscus lens can decrease the focal length of another lens while retaining the angular resolution. Meniscus lenses are used to create a tighter beam focus.

Negative Meniscus: Negative meniscus lenses have a shorter radius of curvature on the concave side and a longer radius of curvature on the convex side; the center of the lens is thicker than its edges. This type of lens is frequently used in place of other negative lenses for high-index infrared materials. They are useful for beam-expanding application, which require minimal spherical aberration.

Configurations

Meniscus lenses are commonly made of optical glass such as BK-7 (Borosilicate Glass), crown glass, flint glass, LaSFN9, and UV grade fused silica along with non-glass materials such as sapphire, polycarbonate, and zinc selenide. Meniscus lenses are generally between 9 and 38mm in diameter and are mounted using optical mounts such as lens holders.

Specifications and Features

The following specifications determine the functionality of a meniscus lens.

• Focal Length: The Effective Focal Length is the distance from the lens that light converges. Focal lengths are positive for a converging system and negative for a diverging system.
• Center/Edge Thickness: The thickness of the lens at its outer edges and its center axis.
• Surface Quality: The lens surface quality describes the appearance of the lens surface. The most common way surface quality is represented is the scratch-dig specification described by the MIL-PRF-13830B standard.

These features provide additional utility or ease-of-use.

• Antireflective Coating: An antireflective coating has been applied to the lens.
• Laser Rated: Lens is rated to be used with lasers. Laser rated lenses are designed to work with laser's high power output without excessive degradation.
• Mounted: The lens comes already mounted.

Images credits:

Thorlabs Inc | Nightlase Technologies