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Shortpass Filters


Short pass filters are edge filters which are used to cut out wavelengths that are not required. The filter removes all wavelengths, such as NIR from visible, from the desired cut off point. For example, a short pass filter with an 650nm cut off point would transmit from the UV and visible at better than 80% up to 650nm, beyond which the transmission would fall steeply to the filter’s minimum of better than a blocking 6OD in the NIR.  Because they isolate specific wavelengths,short-pass filters are desirable in systems where they can be used to trim excess wavelengths or stray light to reduce unwanted near band emissions. Industry applications include order sorting in fluorescence and photometry .

Knight Optical supply a range of bespoke custom shortpass filters.  The range over which high quality custom shortpass filters are available is from 464nm (UV) to 1.55µm (NIR) to meet the required edge cut-off, steepness of the transition, and the amount transmitted or blocked.  For the dichroic filters the unwanted region is reflected.

Custom colour glass shortpass filters:  Solid colour glass shortpass filters are useful for selective  short-pass wavelengths and therefor achieve high out of band blocking .  Short-pass colour glass filters have uniform spectral transmission properties over their entire aperture. They achieve high out of band blocking with high transmission in short wavelengths and low transmission in the long wavelengths.  Solid colour glass shortpass filters are available in a range of custom options. Custom colour glass shortpass filters have uniform spectral transmission properties over their entire aperture.  Colour glass shortpass filters are relatively cheap and very stable. A relatively large range of shortpass filters are available for 464nm-716nm wavelength selection to produce your custom colour glass shortpass filter requirement. Custom colour glass shortpass filters are available in the schott and hoya colour filter ranges and available up to 165mm squares. These can be made into custom square and rectangular apertures or to any shape and sizes with a maximum diameter of 164mm dia.  Some russian and asian equivalent colour shortpass filters are available in larger sheets up to 300x300mm squares. Custom colour glass shortpass filters can be polished thinner achieving higher transmission.  Filters can also be drilled or CNC machined or coated with antireflective coating
to decrease reflections and increase transmission further.  Custom colour shortpass filters are used in range of spectral selection scientific scientific instrument applications
, they also have high transmissions at selected wavelengths therefore ideal where the angle of incidence of the incident light cannot be tightly controlled.

Custom dichroic shortpass filters:  Dichroic filters split the light into two or three bands and reflect one or more and transmit the others. Used at zero incidence they are generally used to select light of one of the primary colours.  Both dichroic shortpass filters and dichroic beamsplitter shortwave reflecting filters are available as custom options.  A huge range of dichroic short-pass filter colours are available not listed as standard on our website.  These can be supplied on white float glass or borosilicate substrates dependent on application.  For applications where high levels of heat are transmitted from light source borosilicate is the best option.  We hold a wide range of stock in 450mm diameter substrates so can offer custom shapes and sizes at short notice. Custom dichroic longpass filter wedges can be supplied to build custom filter wheels.

Custom dichroic beamsplitter shortwave reflecting filters:
Dichroic beamsplitters are used to separate two spectral regions which require detection at the same time. Unlike dichroic filters, the beamsplitters are designed for use at 45° and find an application within Fluorescence Microscopy . Knight Optical provide a range of custom dichroic shortwave reflecting beamsplitter filters. A huge range of dichroic beamsplitter shortwave reflecting filters are available not listed as standard on our website.  These can be supplied on white float or borosilicate substrates where high levels of heat are present.  We hold a wide range of stock in 450mm diameter substrates so can offer custom shapes and sizes at short notice. Custom dichroic beamsplitter shortwave reflecting filter wedges can be supplied to build custom filter wheels.

Custom hot mirrorsAt 0° incidence hot mirrors transmit the visible and reflect the near infra-red (heat) spectrum typically found in tungsten light sources. Hot mirrors therefore remove much of the energy that can cause heating in a lighting system. Hot mirrors can be used as an alternative to KG1 filters where the light is focussed near to the filter giving a risk of cracking. Hot mirrors reflect the heat rather than absorb the heat as in KG1 or equivalent heat filters
.  Custom hot mirrors also have a sharper cut off between IR and Visible because they have a dielectric coating that can be controlled.  Knight Optical stock large sheets of 600mm dia hot mirrors for custom hot mirror applications. Custom hot mirrors are available for visible applications in borosilicate ; we can also provide hot mirror coatings on UV grade fused silica for UV hot mirror applications working down to 175nm. We can supply custom shapes and sizes to your complete specification. A range of mounting options are available.

Custom KG1 filtersSchott KG1 or equivalent  filters are used in lighting systems to remove the near IR thermal energy from the light. As the heat is absorbed in the filter care must be taken that the filter does not overheat and crack.  In most cases it is advisable to thermally toughen KG1 or equivalent which helps to prevent thermal shock and cracking. Knight Optical have a range of custom options for schott KG1 filter glass.  Custom KG1 or equivalent heat filters can be made into custom shapes and sizes with a maximum diameter of 164mm dia. Some Russian and Asian equivalent colour bandpass filters are available in larger sheets up to 300x300mm squares. Custom KG1 or equivalent  Filters can be polished thinner achieving higher transmission. Filters can also be coated with antireflective coating to decrease reflections and increase transmission further. Other KG or equivalent glasses available in custom options are KG2 or equivalent, Schott KG3 or equivalent, Schott KG4 or equivalent and Schott KG5 or equivalent and chosen for their peak wavelength conditions.

Our custom shortpass filters can be supplied in range of mounting options.  For example custom long pass filters can be supplied to screw directly onto tamron lenses which have a 25.5 thread on the front and similar custom solutions for lenses in fujinon range where no thread is provided.

Knight Optical supply high quality custom shortpass filters made to our exact specification.  Every component is individually tested on our Agilent Cary 5000 spectrometers fitted with a UMA device for testing coatings in transmission and reflection at any given angle.  We also have a DRA device fitted for testing complex beamsplitter components.  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 shortpass filters and service can improve your instrumentation and supply chain experience.

Our 2018/2019 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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