Compare Model Drawings, CAD & Specs Optical Density Material Availability Price
In Stock
0.05 - 1 N-BK7
In Stock
1 Week
0.05 - 2 UV grade fused silica
1 Week


  • Size
    Ø127.0 mm
  • Optical Density Tolerance
    ±0.15 over 270° at 0° AOI
  • Damage Threshold
    75 W/cm2 CW, 10 mJ/cm2 with 10 nsec pulses at the specified wavelength, typical
  • Size Tolerance
    +0/-0.25 mm
  • Thickness
    9.53 mm
  • Thickness Tolerance
    ±0.38 mm
  • Surface Quality
    30-10 scratch-dig
  • Clear Aperture
    From 33 mm to 101 mm diameter
  • Chamfers
    0.50–1.52 mm face width
  • Chamfers Angle Tolerance
    45° ±15°
  • Durability
    Metalized area MIL-M-13508C, AR coated area MIL-C-675, moderate abrasion
  • Inside Diameter
    25.4 mm


Finely Control Beam Attenuation

These filters allow convenient adjustment of beam attenuation by simply rotating the filter. Optical density varies continuously from 0.05–1.0 (or 0.05-2.0) across a 270° angular range. The thin reflective aluminum film is able to withstand moderate power laser beams. BK7 substrates are a good general laboratory use option, while Fused Silica substrates offer maximum thermal stability.

Optimized for 450-700 nm Wavelength Range

Circular variable ND filters are available with BK 7 substrates for general laboratory use, or UV fused silica substrates for maximum thermal stability. Although the coatings are optimized for 450–700 nm, they will operate from 400–1100 nm with only minor losses.

Proper Orientation

To prevent unwanted interference from etalon effects, filters should be angled slightly with respect to the incident beam. To minimize back reflections, the filter should be oriented with the coated metallic surface facing the incident beam. Any light reflected from the uncoated second surface will pass through the metallic coating first, which will greatly attenuate unwanted back reflections.

AR Coated Second Surface

The second surface of this circular linear variable filter is AR coated to prevent undesired transmission loss, and to reduce stray light due to back reflections. The AR coating is optimized for 440 to 700 nm.

Variable Beamsplitter Applications

These filters consist of a thin metallic coating of variable thickness. Because attenuation is primarily caused by reflection with only a small amount of absorption, these filters may optionally be used as variable beamsplitters.

Circular ND Filter Mounting

Our circular variable attenuators are ideally mounted with our 941 Compact Filter Rotators or 946 (946-M)Tip & Tilt Filter Rotation Mounts.