BRD Optical makes fixed OD value neutral density filter by depositing Inconel film on a clear cubstrate. The advantage of the coated density filter is in the broader band and lower ripple than that of absorptive density filter. The coated wavelengthcan be extended to 200nm to 1100nm or more. 
The disadvantage is that there is some reflective light on the filter. The OD value can vary from 0.1 to 0.5. The OD value is controlled by coating inconel thin film 
thickness. Regular thickness of the NDF is 1.1mm or 0.55mm.
| Material | BK7 |
| Diameter tolerance | +0.0/-0.1mm |
| Thickness tolerance | ±0.1mm |
| Parallelism | <3 arc min |
| Flatness | λ~λ/10 |
| Clear aperture | >90% |
| Density tolerance | ±2% |
| Part No. | Wanvelength Range (nm) | Optical Density (OD) @550nm |
| ND01 | 400-1100 | 0.1 |
| ND02 | 400-1100 | 0.2 |
| ND03 | 400-1100 | 0.3 |
| ND04 | 400-1100 | 0.4 |
| ND05 | 400-1100 | 0.5 |
| ND06 | 400-1100 | 0.6 |
| ND07 | 400-1100 | 0.7 |
| ND08 | 400-1100 | 0.8 |
| ND09 | 400-1100 | 0.9 |
| ND10 | 400-1100 | 1 |
| ND20 | 400-1100 | 2 |
| ND30 | 400-1100 | 3 |
| ND40 | 400-1100 | 4 |
| ND50 | 400-1100 | 5 |
