DescriptionSpecifications
Models
Catalog PDF
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These ND filters provide linearly varying attenuation or beamsplitting in the visible and near infrared region. The optical density varies linearly across the length. Attenuation is achieved by a thin film of aluminum protected with an overcoat. Variable beamsplitting is an added benefit due to the inherent reflectivity of aluminum. The rear surface is coated with a broadband antireflection coating for the visible region. The precision polished BK 7 or UV grade fused silica substrates have a slight wedge between the faces to eliminate unwanted fringe patterns and cavity feedback.
Linear variable filters can be used individually or in matched pairs. A matched pair will eliminate the density gradient over larger apertures when moved in opposing directions. Our Model 925B compensated attenuator utilizes a matched pair of these filters and the mechanics to move them precisely (see Compensated Attenuators). |
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Specifications
| Material | BK 7, grade A, fine annealed optical glass or equivalent; UV grade fused silica |
| Surface Flatness | Specification below at 632.8 nm over the clear aperture |
| Clear Aperture | ≥central 90% of length and 80% of width |
| Dimensions | 79.4 x 25.4 mm +0/-0.25 mm |
| Thickness | 3.18 +0/-0.76 mm |
| Wedge | 15 ±5 arc min in 25.4 mm dimension |
| Matched Pairs | ≤20 arc sec wedge mismatch |
| Chamfers | 0.25–0.76 mm face width x 45° ±15° |
| Optical Density at 632.8 nm | 0.08–2.0 ±5%, transmission along 25.4 mm dimension uniform to 5% |
| Linearity of Density | ±5% |
| Coating, S1 | Aluminum with an AR.14 overcoat |
| Coating, S2 | AR.14 broadband antireflection coating,
Ravg <0.5% 430-700 nm at 0-15° 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 (Unknown type Newport.Step.Product.XRefElement) |
| Damage Threshold | 75 W/cm2 CW, 10 mJ/cm2 with 10 nsec pulses at 1064 nm, typical |
| Model | Material | Optical Density Range | Surface Flatness | Surface Quality |
| Individual Filters |
| 31W00ML.1 | BK 7 | 0.08–2.0 | ≤2λ | 40-20 |
| 31Y02ML.1 | UV Fused Silica | 0.08–2.0 | ≤1λ | 20-10 |
| Matched Filter Pairs |
| 31W00MP-ML.1 | BK 7 | 0.16–4.0 | ≤2λ | 40-20 |
| 31Y02MP-ML.1 | UV Fused Silica | 0.16–4.0 | ≤1λ | 20-10 |
| | Model | Description |
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31W00ML.1
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Linear Variable Metallic ND Filter, BK 7, 79.4x25.4mm, 0.08-2 OD, ≤2λ
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31W00MP-ML.1
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Linear Variable Metallic ND Filter Pair, BK 7, 79.4x25.4mm, 0.08-2 OD
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31Y02ML.1
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Linear Variable Metallic ND Filter, UV Fused Silica, 79.4x25.4 mm, 0.08-2 OD
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31Y02MP-ML.1
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Linear Variable Metallic ND Filter Pair, UV Fused Silica, 79.4x25.4mm, 0.08-2 OD
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