Telecom Optics

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Drum lenses

Product Description

Hobbite® Telecom Optics (Drum lenses)

Drum lenses and half drum lenses are adapted ball lenses. Drum lenses are manufactured by axial grinding and hence removing the outside proportion of the sphere. The resulting drum lens is then easier to handle. As a drum lens has a ground outside diameter it’s therefore easier to mount and align into optical systems as the outside diameter is cylinder in shape. The two spherical lens shapes either ends of the drum lens are still perfect for fibre-coupling and endoscopy applications.

Half drum lenses are what the name suggests a drum lens that is cut in half. A half drum lens is manufactured by taking a full drum lens that has two spherical faces and then polishing one of its spherical faces to a plano flat face resulting in an elongated planoconvex lens.

Our range of drum and half drum lenses can be manufactured from a range of materials;N-BK7 or equivalent is typically used in visible applications. Quartz and UV grade fused silica is used for applications working in deep UV wavelengths down to185nm; these materials are also useful in the NIR wavelengths up to 2000nm. A range of high index materials in Schott and Ohara grades such as Lasfn9, Lasf35, S-Lah65 and Lah78 are available for very short focal lengths with minimal spherical aberrations.


Type Drum Lens
Diameter (mm) 2.0
Diameter Tolerance (μm) +0/-50
Radius R (mm) 1.25
Radius Tolerance (μm) +0/-1.5
Length (mm) 2.50
Length Tolerance (μm) ±3
Surface Quality 40-20
Index of Refraction nd 1.517
Substrate N-BK7
Coating Uncoated
Wavelength Range (nm) 350 – 2200
RoHS Compliant


You can customise this product to your needs. If you do not find suitable specifications for your application please contact us for custom solution.

To order or request information please drum-lenses-typeafill in the form (
3.Focal length
6.Center Thickness


  • Cylindrical Sides with Convex curvatures
  • Typical Ball lens Performance
  • High Transmittance
  • Low Reflectance
  • Accurate Wavelength manipulation


  • Compact Fiberoptical Components
  • Laser Systems
  • Micro Optical Devices
  • Optical Assemblies


Hobbite metrology lab applies following product inspection:
Visual inspection – surface quality evaluation according to MIL 13830 and ISO 10110 standards
Dimensions – measurement of geometrical dimensions, as diameter, thickness, etc.
Radius of Curvature (Spherometer)*
Effective Focal Length (Spherometer)
Centering (Centration unit)
Irregularity (Interferometer)
Wavefront distortion (Interferometer)