Our circular variable neutral density filters are designed to simplify attenuation and beamsplitting in the visible to near IR. The optical density gradient varies from 0.05–1.0 or 2.0 around a 270° circle for convenient attenuation adjustment by simply rotating the filter. Attenuation is achieved by a thin, reflective aluminum film, allowing these attenuators to withstand moderate laser energy as well as act as variable beamsplitters. A broadband, visible antireflection coating on the back side allows the optic to be left in the beam path at all times with minimal losses or ghost images.
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. Our circular variable attenuators are ideally mounted with our 941 and 946 mounts.
Specifications
| Material |
BK 7, grade A, fine annealed optical glass or equivalent; UV grade fused silica |
| Surface Flatness |
From ≤λ/2 to ≤2λ (see Ordering Information)Specification below at 632.8 nm over the clear aperture |
| Clear Aperture |
From 33 mm to 101 mm diameter |
| Outside Diameter |
127 +0/-0.25 mm |
| Inside Diameter |
25.4 +0.25/-0 mm |
| Thickness |
9.53 ±0.38 mm |
| Chamfers |
0.50–1.52 mm face width x 45° ±15° |
| Optical Densityat 632.8 nm |
AV.1: 0.05–1.0 ±0.15 over 270° at 0° AOI, density increases in a counterclockwise direction |
| AV.2: 0.05–2 ±0.20 over 270° at 0° AOI, density increases in a counterclockwise direction |
| Linearity of Density |
±5% |
| Coating, S1 |
Aluminum with an SiO overcoat |
| Coating, S2 |
Broadband antireflection coating,
Ravg <0.75% 440–700 nm at 45° AOI |
| Durability |
Metalized area MIL-M-13508C, AR coated area MIL-C-675, moderate abrasion |
| Cleaning |
Non-abrasive method, acetone or isopropyl alcohol on lens tissue recommended (see How to Clean Optics) |
| Damage Threshold |
75 W/cm2 CW, 10 mJ/cm2 with 10 nsec pulses at the specified wavelength, typical |
Circular Variable Metallic Neutral Density Filters Table
|
Model |
Material |
Diameter
[in. (mm)] |
Optical Density Range |
Surface Flatness |
Surface Quality
(scratch-dig) |
Wedge
() |
| 50G02AV.1
|
BK 7 |
127.0 |
0.05–1.0 |
≤1λ |
30-10 |
|
| 50G02AV.2
|
BK 7 |
127.0 |
0.05–2.0 |
≤1λ |
30-10 |
|
| 50Q04AV.1
|
UV grade fused silica |
127.0 |
0.05–1.0 |
≤λ/2 |
30-10 |
|
| 50Q04AV.2
|
UV grade fused silica |
127.0 |
0.05–2.0 |
≤λ/2 |
30-10 |
|
These graphs model performance of the front surface coating only.
