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Looking For a Custom Optical Solution? Enquire

Custom Filters

interference filters, longpass, shortpass, bandpass, neutral density, colour glass, dichroicThere are a multitude of different optical filters on the market, and Knight Optical has the capabilities to provide precision, bespoke filters to our customers. As the name implies, a filter is designed to only transmit the desired wavelengths whilst blocking the rest, either via reflection or absorption. The degree of transmission and attenuation depends on the filter type.
Knight Optical can provide the following filter types:

  • Interference bandpass
  • Dichroic
  • Colour Glass
  • Wratten 2/Polyester
  • Neutral Density
  • Heat Control
  • IR Cut

Below are our typical filter capabilities but these are always expanding, so please do not hesitate to contact our technical sales team with your enquiry:

Types Available

Interference, Dichroic, Polyester, Wratten 2, Colour glass, Neutral Density



12.5mm to 100mm diameter


3mm to 400mm diameter

Wratten 2/Polyester

100mm x 300mm

Colour glass

3mm to 100mm diameter

Neutral Density

5mm to 300mm+


175 to 3200nm+


3nm to 100nm+

Peak transmission*

> 85%


< OD4

Surface Quality*

< 60/40

Mounting Options

Mounted or unmounted available

Contact our dedicated account managers with your enquiry and we will work with you on your custom order.

Browse the categories below for further information on the different filter types available:

Additional Information

  • Filters are often categorised as bandpass, shortpass and longpass.
  • A bandpass filter will only transmit a certain waveband with blocking either side of this. Often the bandpass filter type is defined by the size of the bandwidth – narrowband, standard and broadband.
  • A shortpass filter transmits wavelengths before the cut-off wavelength. They are often used in applications to block near infrared (NIR) light from entering a system.
  • A longpass filter transmits wavelengths after the cut-on wavelength whilst blocking the shorter wavelengths before the cut-on point.
  • The cut-on and cut-off wavelengths are defined as 50% of the peak transmission.
  • Combining a shortpass and longpass filter can create bespoke bandpass filters, though with less control over parameters compared to an interference bandpass filter.

Quality Assurance

  • Transmission, absorption and reflection scans are conducted on our Agilent Cary 7000 Spectrophotomer which can perform spectral scans at multiple angles of incidence and different polarisations. Knight Optical can provide ASCII data and a graph of the spectral properties.
  • We can also test infrared filters on our Agilent Cary 660 FTIR spectrometer.
  • All optics are 100% visually inspected before packaging, our staff are trained to ISO 10110 and MIL-0-13830A, and can check down to 10/5 scratch/dig which is especially critical in laser applications.

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.
Click below to view our digital catalogue now.

view our catalogue