UV Fused Silica Positive Meniscus Lenses, Uncoated

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Features

• Choose from Ø1" or Ø2" Versions
• Wavelength Range: 185 nm - 2.1 μm (uncoated)
• Focal Lengths Available from 100.0 - 1000.0 mm
• Fabricated from UV-Grade Fused Silica
• Spherical Surface Power: 3 Fringes
• Spherical Surface Irregularity: λ/4

Thorlabs' UV-Grade Fused Silica Positive Meniscus Lenses are available either uncoated or with a UV antireflection coating for the 245 - 400 nm range deposited on both surfaces. Compared to N-BK7, UV-Grade Fused Silica offers high transmission deeper into the UV (down to 185 nm), better homogeneity, and a lower coefficient of thermal expansion. In addition, UV fused silica exhibits virtually no laser-induced fluorescence (as measured at 193 nm), making it an ideal choice for applications from the UV to the near IR.

Positive meniscus (convex-concave) lenses, which are thicker in the middle than at the edges and cause light rays to converge, are designed to minimize third-order spherical aberration. They are often used in conjunction with other lenses to decrease the focal length, and therefore increase the numerical aperture (NA), of an optical assembly. When used to focus a collimated beam, as shown in the diagram above, the convex side of the lens should face the source to minimze spherical aberration. Since a positive meniscus lens has a greater radius of curvature on the concave side of the lens than on the convex side, real images can be formed.

Thorlabs offers their negative meniscus lenses in Ø1 and Ø2" versions. Each size is compatible with a multitude of Thorlabs lens mounts. Please see the Mounting Options tab for details.

Using Positive Meniscus Lenses

• Achieve Tighter Focusing by Combining a Meniscus Lens with Plano-Convex Lenses
• Build Multi-Element Lens Systems to Achieve Higher NA without Significant Increases in Aberrations

Positive meniscus lenses are designed to minimize spherical aberration. They have one convex and one concave surface. When used in combination with another lens, a positive meniscus lens will shorten the focal length and increase the NA of the system. Figures 3.1 through 3.3 illustrate the performance gains that can be achieved by using multi-element imaging systems. The combination of a meniscus lens and a plano-convex lens yields a 21 µm focused spot versus a 240 µm spot from the single plano-convex lens. Figure 3.3 shows a meniscus lens being used to shorten the focal length of a 100 mm focal length plano-convex lens. In addition, the transverse and lateral aberrations are greatly reduced. The convex surface of both lenses should be facing away from the image.

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Figure 3.1  A single plano-convex lens focuses the beam to a Ø240 µm spot.

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Figure 3.2  Two plano-convex lenses focus the beam to a Ø81 µm spot.

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Figure 3.3  A plano-convex lens used with a positive meniscus lens focuses the beam to a Ø21 µm spot.