- Provides Continuously Variable Attenuation
- OD Ranges from 0.04 - 2.0 or 0.04 - 4.0
- Two Size Options
Thorlabs' Rectangular Continuously Variable Metallic (i.e., reflective) Neutral Density Filters provide a continuous range of optical densities (OD) in a single optic. They are composed of a UV fused silica glass substrate and a metallic Inconel coating, ensuring a flat spectral response from the ultraviolet into the mid-infrared. These filters are commonly used as variable attenuators. Offered in 10 mm x 50 mm and 25 mm x 100 mm sizes (H x W), these rectangular neutral density filters are available with OD ranges of either 0.04 - 2.0 or 0.04 - 4.0. Please refer to the Specs tab for more information.
The optical density, OD, is defined by the equation:
Hence, a higher OD corresponds to lower transmission and greater reflection of the incident light, while a lower OD corresponds to higher transmission and less reflection. For example, an OD = 2 filter will attenuate the transmitted beam to 1% of the incident intensity. See the Graph tab for a plot of transmission as a function of distance when using one of our continously variable filters.
The Inconel coating on these filters is a very hard metallic alloy that is resistant to aging under normal conditions but will oxidize at elevated temperatures. It is therefore recommended that the neutral density filters be used at temperatures below 100° C.
These filters are not intended to serve as laser safety equipment. For lab safety, Thorlabs offers an extensive line of safety and blackout products that significantly reduces exposure to stray or reflected light.