The neutral density filter is an optical component used to uniformly attenuate light intensity without altering the spectral composition of the source. Based on the working principle, ND filters can be classified into absorptive ND filters and reflective ND filters. According to the optical density profile, they fall into fixed OD filters, graduated ND filters, and variable ND filters. By spatial distribution, they are categorized as uniform ND filters and patterned ND filters.
Maintains spectral neutrality.
Precise control of light intensity.
May introduce aberrations or non-uniformity.
| Material | Optical glass, Fused Silica |
| Diameter Tolerance | +0.0,-0.2 mm |
| Thickness Tolerance | +0.0,-0.1 mm |
| Parallelism | ＜30" |
| Transmitted Wavefront Error | λ/4@633nm |
| Blocking | OD≥2 |
| Clear Aperture | >90% CA |
| Surface Quality | 40/20-60/40 S/D |
