• PCX-Lenses-NBK7-(K9)-1

Plano-Convex Lenses

Plano-convex (PCX) lenses have a positive focal length and can be used to focus collimated light, to collimate a point source, or to reduce the divergence angle of a diverging source. When image quality is not critical, plano-convex lenses can also be used as a substitute for achromatic doublets. To minimize the introduction of spherical aberration, a collimated light source should be incident on the curved surface of the lens when being focused and a point light source should be incident on the planar surface when being collimated.

Each N-BK7 lens can be offered with a 532/1064 nm, 633 nm, or 780 nm laser line V-coating. The V-coating is a multilayer, anti-reflective, dielectric thin-film coating designed to achieve minimal reflectance over a narrow band of wavelengths. Reflectance rises rapidly on either side of this minimum, giving the reflectance curve a “V” shape, as shown in the following performance plots. For more information on other AR coatings such as wavelength ranges of 350 – 700 nm, 400 – 1100 nm, 650 – 1050 nm, or 1050 – 1700nm, please contact us for details.

Paralight Optics offers N-BK7 (CDGM H-K9L) Plano-Convex lenses with options of either uncoated or our antireflection (AR) coatings, which reduces the amount of light reflected from each surface of the lens. Since approximately 4% of the incident light is reflected at each surface of an uncoated substrate, the application of our multi-layer AR coatings improves transmission, which is important in low-light applications, and prevents the undesirable effects (e.g., ghost images) associated with multiple reflections. Having optics with AR coatings optimized for the spectral range of 350 – 700 nm, 400 – 1100 nm, 650 – 1050 nm, 1050 – 1700 nm, 1650 – 2100 nm deposited on both surfaces. This coating greatly reduces the average reflectance of the substrate less than 0.5% (Ravg < 1.0% for the ranges of 0.4 – 1.1 μm and 1.65 – 2.1 μm) per surface, yielding a high average transmission across the entire AR coating range for angles of incidence (AOI) between 0° and 30° (0.5 NA). For optics intended to be used at large incident angles, consider using a custom coating optimized at a 45° angle of incidence; this custom coating is effective from 25° to 52°. Broadband coatings have a typical absorption of 0.25%. Check the following Graphs for your references.





Wavelength Range:

330 nm - 2.1 μm (Uncoated)

Coating Options:

Uncoated or with AR Coatings or laser line V-Coating of 633nm, 780nm or 532/1064nm

Focal Lengths:

Available from 4 to 2500 mm


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

    N-BK7 (CDGM H-K9L)

  • Type

    Plano-Convex (PCV) Lens

  • Index of Refraction (nd)


  • Abbe Number (Vd)


  • Thermal Expansion Coefficient (CTE)

    7.1 x 10-6/℃

  • Diameter Tolerance

    Precison: +0.00/-0.10mm | High Precision: +0.00/-0.02mm

  • Thickness Tolerance

    Precison: +/-0.10 mm | High Precision: +/-0.02 mm

  • Focal Length Tolerance

    +/- 1%

  • Surface Quality (Scratch-Dig)

    Precison: 60-40 | High Precision: 40-20

  • Surface Flatness (Plano Side)


  • Spherical Surface Power (Convex Side)

    3 λ/4

  • Surface Irregularity (Peak to Valley)


  • Centration

    Precison: <3 arcmin | High Precision: <30 arcsec

  • Clear Aperture

    90% of Diameter

  • AR Coating Range

    See the above description

  • Transmission over Coating Range (@ 0° AOI)

    Tavg > 92% / 97% / 97%

  • Reflectance over Coating Range (@ 0° AOI)

    Ravg < 0.25%

  • Design Wavelength

    587.6 nm

  • Laser Damage Threshold

    7.5 J/cm2 (10ns,10Hz,@532nm)



♦ Transmission curve of uncoated NBK-7 substrate: high transmission from 0.33 µm to 2.1 μm
♦ The following plots of V-coats have a minimum reflectance of less than 0.25% per surface at the coating wavelength of 633nm, 780nm, 532/1064nm (YAG V-coating) and are designed for angles of incidence (AOI) between 0° and 20°. Compared to our broadband AR coatings, V-coatings achieve lower reflectance over a narrower bandwidth when used at the specified AOI. For more information or get a quote, feel free to contact us.


633 nm V-Coat Reflectance (AOI: 0 - 20°)


780 nm V-Coat Reflectance (AOI: 0 - 20°)


532/1064 nm V-Coat Reflectance (AOI: 0 - 20°)