Product Types
We supply a wide range of optical filters for the infrared region of the spectrum
We supply a wide range of optical filters for the infrared region of the spectrum. These filters are normally combinations of thin film interference filters which can be tailor made to any wavelength, and absorption filters, which depend on the fundamental optical properties of materials.
The thin film filters comprise of stacks of thin layers (of different optical materials) in controlled thicknesses. Light is reflected at each film interface and by correct choice of parameters can be made to interfere with that from other interfaces, constructively, for certain wavelengths giving high reflectance and destructively for others, giving high transmittance. Longwave pass, shortwave pass and bandpass filters can be designed and manufactured in this way. Normally, because of the finer number of layers involved, ideal performance is obtained only over a limited range of wavelengths.
Outside this range, spurious transmission occurs and usually auxiliary filters are used to suppress the unwanted sidebands. The auxiliary filters are in most cases absorption filters, which have extensive rejection bands but which lack the flexibility of thin film filters, although sometimes additional inference filters may be used, particularly when no suitable absorption filters exist.
Filter Types
Narrow Bandpass
Narrow bandpass filters are designed to isolate a narrow region of the infra-red spectrum.
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Wide Bandpass
Wide bandpass filters are designed to isolate a very wide spectral band.
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Long Wave Pass
Long Wave Pass filters (also referred to as edge filters) are constructed from stacks of thin layers.
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Short Wave Pass
Short wave pass filters are distinguished by a sharp transition from a zone of transmission to a zone of rejection.
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Neutral Density
The majority of neutral density filters offered are manufactured with a metallic coating which attenuates incident light by both reflection and absorption
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Gas Bands
A range of special purpose narrow band filters for gas and vapour analysis are generally available ex-stock at very competitive prices.
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Order Sorting
Blocking and order sorting filters are frequently used in measuring equipment to suppress unwanted wavelengths.
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Semiconductor Filters
Semiconductor filters are, strictly, not thin film filters, but absorption filters, relying on the electronic band of their structure.
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Anti-Reflection
Capabilities in anti-reflection coatings range from single layers to advanced high efficiency multi-layer coatings.
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Optical Windows
Blocking and order sorting filters are frequently used in measuring equipment to suppress unwanted wavelengths.
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Mirrors
Blocking and order sorting filters are frequently used in measuring equipment to suppress unwanted wavelengths.
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