• CaF2-PCX
  • PCX-Lenses-CaF2-1

Calcium Fluoride (CaF2)
Plano-Convex Lenses

Plano-convex (PCX) lenses are positive lenses which are thicker in the middle than at the edge, when collimated rays go through them, light converges to a physical focal point. Plano-convex lenses have one flat side and one curved side with a positive radius of curvature. Plano-Convex lenses have a positive focal length and approach best form for infinite and finite conjugate applications. These lenses focus a collimated beam to the back focus and collimate light from a point source. They are designed with minimal spherical aberration and have a focal length given by:
f= R/(n-1),
where R is the radius of curvature of the convex portion of the lens and n is the index of refraction.

Plano-convex lenses deliver less spherical distortion when focusing at infinity (when the imaged object is far away and the conjugate ratio is high). Therefore they are the go-to lens in cameras and telescopes. Maximum efficiency is achieved when the plano surface faces the desired focal plane, in other words, the curved surface faces the collimated incident beam. Plano convex lenses are a good choice for light collimation or for focusing applications utilizing monochromatic illumination, in industries such as industrial, pharmaceutical, robotics, or defense. They are an economical choice for demanding applications because they are easy to fabricate. As a rule of thumb, plano-convex lenses perform well when the object and image are at absolute conjugate ratios > 5:1 or < 1:5, so spherical aberration, coma and distortion are reduced. When the desired absolute magnification is between these two values, Bi-convex lenses are usually more suitable.

Due to its high transmission from 0.18 µm to 8.0 μm, CaF2 exhibits a low refractive index varying from 1.35 to 1.51 and is commonly used for applications requiring high transmission in the infrared and ultraviolet spectral ranges. Calcium fluoride is also fairly chemically inert and offers superior hardness compared to its barium fluoride, and magnesium fluoride cousins. Paralight Optics offers Calcium Fluoride (CaF2) plano-convex lenses with antireflection coatings for either the 1.65 µm to 3.0 µm or 2 µm to 5 µm wavelength range. This coating greatly reduces the average reflectance of the substrate less than 1.25%, yielding a high average transmission greater than 95% across the entire AR coating range. Check the following Graphs for your references.




Calcium Fluoride (CaF2)

Coating Options:

Uncoated or with Antireflection Coatings

Focal Lengths:

Available from 20 to 1000 mm


Suitable for Use in Excimer Laser Applications, in Spectroscopy and Cooled Thermal Imaging


Common Specifications:


Reference Drawing for

Plano-convex (PCX) Lens

Dia: Diameter
f: Focal Length
ff: Front Focal Length
fb: Back Focal Length
R: Radius
tc: Center Thickness
te: Edge Thickness
H”: Back Principal Plane

Note: The focal length is determined from the back principal plane, which does not necessarily line up with the edge thickness.



Ranges & Tolerances

  • Substrate Material

    Calcium Fluoride (CaF2)

  • Type

    Plano-Convex (PCV) Lens

  • Index of Refraction

    1.428 @ Nd:Yag 1.064 μm

  • Abbe Number (Vd)


  • Thermal Expansion Coefficient (CTE)

    18.85 x 10-6/K (20 - 60℃)

  • Diameter Tolerance

    Precison: +0.00/-0.10mm | High Precision: +0.00/-0.03 mm

  • Center Thickness Tolerance

    Precison: +/-0.10 mm | High Precision: +/-0.03 mm

  • Focal Length Tolerance

    +/- 2%

  • Surface Quality (Scratch-Dig)

    Precison: 80-50 | High Precision: 60-40

  • Surface Flatness (Plano Side)


  • Spherical Surface Power (Convex Side)

    3 λ/2

  • Surface Irregularity (Peak to Valley)


  • Centration

    Precison: <3 arcmin | High Precision: < 1 arcmin

  • Clear Aperture

    > 90% of Diameter

  • AR Coating Range

    1.65 µm - 3.0 μm | 2 - 5 μm

  • Transmission over Coating Range (@ 0° AOI)

    Tavg > 98% | Tavg > 95%

  • Reflectance over Coating Range (@ 0° AOI)

    Ravg < 1.25%

  • Design Wavelength

    588 nm



♦ Transmission curve of 10 mm thick uncoated CaF2 substrate: high transmission from 0.18 µm to 8.0 μm
♦ Transmission curve of 2.2 mm center thickness AR-coated CaF2 Lens: Tavg > 98% over the 1.65 µm - 3.0 μm range
♦ Transmission curve of enhanced AR-coated CaF2 Lens: Tavg > 95% over the 2 µm - 5 μm range


Transmission Curve of 2.2 mm Center Thickness AR-coated (1.65 µm - 3.0 μm) CaF2 Lens


Transmission Curve of Enhanced AR-coated (2 µm - 5 μm) CaF2 Lens