Europe, UK, Asia & RoW: [email protected] +44 (0)1622 859444 | USA & Canada: [email protected] +1 401-583-7846

BREXIT UPDATE: Knight Optical will continue to provide quality assured service for all your optical requirements both custom & stock. We will handle all requirements caused by the new regulations.


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Neutral Density Filters

neutral density filter from Knight OpticalNeutral density filters are designed to equally reduce the transmission over a specified spectrum, either by absorption or reflection. The optical density (OD) of the filter is controlled by the material and its thickness. Knight Optical can supply custom neutral density filters in gelatine, Absorption
schott glass range and metallic type options.

Custom glass neutral density filters attenuate light by absorption just like the custom gelatine neutral density filters so care must be taken to avoid overheating.  Custom glass ND filters are more robust and tend to have more uniform absorption characteristics. Custom absorption type neutral density filters are available as 165x165mm squares of which any shape or size can be custom machined to meet your specific requirement. Larger sizes using alternative material supply equivalent to schott glass
are available up to 300mm sq, please speak to our technical team.  Custom gelatine ND filters are available up to 300x100mm sheets and can easilily be cut with a razor for special custom sizes and shapes. Custom metallic neutral density filters comprise a thin metallic layer on a LEGB borosilicate or equivalent  or fused silica polished window. Metallic filters attenuate the light by reflection and thus avoid the possible heating issues with glass and gelatine filter types. However care must be taken to ensure the reflected light does not cause problems elsewhere in the optical system.  Custom metallic ND filters can be made to any shape or size as UV fused silica and borosilicate are available in large sheets.  We can also vacuum coat large sheets and dice to very small squares after coating ensuring cost effective production.

Our custom range of high quality neutral density filters are available from 175-2500nm to meet most requirements. A range of mounting options are available for seamless integration of custom ND filters into your instrument application

Knight Optical supply high quality custom neutral density filters made to your exact specification. Every component is individually tested on our Agilent Cary 5000 spectrometers fitted with a UMA device for testing transmission and reflection at any given angle. Our Agilent 660 FTIR spectrometer is used for coatings between 3.5µm and 45µm. All tested by our highly skilled technicians in our state of art metrology lab to ensure all components meet our high quality standards. We can provide transmission and reflection curves at given wavelengths from 175nm up to 3200nm in TXT or CSV format, or other formatted options.

Contact our multilingual technical sales team and discover how Knight Optical’s high quality custom neutral density filters and service can improve your instrumentation and supply chain experience.

Our 2022/2023 Catalogue

Inside Knight Optical’s catalogue you’ll find details of the industries we serve as well as the many other services we can offer. It also showcases hundreds of our most popular products, supported by useful technical information, to help you choose the right part for your application.
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