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In the Spotlight: Infrared (IR) Windows

22nd Sep 2021

In this blog, Knight Optical – the leading supplier of stock and custom-made premium-quality optical components – investigates some popular uses for its Infrared (IR) Windows and talks through these highly-specified optics’ key features.

Exploited across a wide variety of industries, Infrared (IR) Windows are engineered explicitly to pass infrared (IR) wavelengths. Whether it’s the near-infrared (NIR), short-wave infrared (SWIR), mid-wave infrared (MWIR) or long-wave infrared (LWIR) sub-band, our IR Windows are employed for a wide range of uses – and each specified batch of Windows, of course, have their own set of precise specifications. In fact, when it comes to Knight Optical’s IR Windows, it is a rarity to find a pair of matching specifications, which stems from their long list of utilisations.

With so many functions and industries – all with their own set of stringent regulations to abide by – it’s no wonder that our custom-made IR Windows are so prevalent. As well as bespoke dimensions, augmenting optical coatings and modified thicknesses, our customised IR Windows are also available in specific substrates, tailored to your end application’s demands to ensure optimum operability.

What Substrates are Available at Knight Optical?

Here at Knight Optical, we boast an extensive portfolio of substrates for all categories of optical components.

Specifically for IR Windows, our options include:


With transmission wavebands ranging from 0.12 to 12µm, our Fluoride substrates not only excel in IR applications but also perform exceptionally well in the ultraviolet (UV) and visible (VIS) spectrums too.

Our Fluoride portfolio consists of:

Calcium Fluoride (CaF2)
With transmission bands spanning 0.13 to 10µm, Calcium Fluoride’s (CaF2) features comprise low absorption and a high transmission band that ranges from UV to MWIR.
   Barium Fluoride (BaF2)
Transmitting from 0.12 to 12µm, Barium Fluoride (BaF2) has a somewhat extended frequency band in contrast with CaF2. With transmission above 90%, it’s easy to see  why    BaF2 is such a sought-after substrate in multiple sectors.
Magnesium Fluoride (MgF2)
The toughest of our popular Fluoride trio and transmitting from 0.1 to 7µm, Magnesium Fluoride (MgF2) is ideal for both IR and UV applications and, unlike CaF2 and BaF2, is also water stable.

Potassium Bromide (KBr)
With an average transmission of 90% between 0.3 and 20µm, these crystalline IR windows have an impressive range that spans the UV, VIS, MWIR and LWIR spectrums. Click here to view our Potassium Bromide (KBr) options.

Sodium Chloride (NaCl)
Again, ideal for IR and UV applications, Sodium Chloride (NaCl) has a high transmission of 0.2 to 15µm. The substrate itself is soft, highly soluble and hygroscopic and, therefore, requires protection from atmospheric conditions.

Zinc Selenide (ZnSe)
Our Zinc Selenide (ZnSe) Windows transmit from 0.5 to 15µm – before dropping to zero. With a low absorbance in the IR range, ZnSe is regularly used for CO2 laser applications.

Germanium (Ge)
With transmission between 1.8 and 23µm, Germanium (Ge) is an ideal substrate for applications where the UV and VIS regions are blocked, solely receiving transmission into the LWIR region.

What are IR Windows Typically Used For?
At Knight Optical, our IR Windows are specified for an array of applications throughout the world and are abundant in a vast assortment of sectors.

Just a few of the industries and utilisations that our IR Windows are employed for include:
Military & Defence
As a long-standing partner with military and defence organisations across the globe, Knight Optical is accustomed to the stringent demands that are sought by this high-specification field.

Our IR Windows are amongst some of the most popular optics that we supply to this sector.
Specific applications include:

  • Navigation
  • Night vision goggles
  • Guidance heads for missiles
  • Forward-looking infrared (FLIR) scanners – and much more.

Oil & Gas
In the Oil & Gas sector, IR Windows make up a part of potentially life-saving equipment for personnel working on site and the surrounding areas of facilities. These essential systems allow oil and gas producers to monitor locations and ensure they’re free from gas leaks and confirm that system integrity is uncompromised.

Standard devices used within this industry – which make use of IR optics – include:
Optical Gas Imaging (OGI)

  • Thermal cameras
  • Thermal imaging cameras with a cooled detector
  • Gas Cloud Imaging (GCI) – and much more.

Much like the above-mentioned Oil & Gas industry, IR Windows are hugely beneficial within the electricals arena. Thermography – and, of course, the IR Windows that frequently accompany thermographic devices – are instrumental for those working with possibly hazardous electricals. This equipment is regularly used to inspect live electrical equipment without the need for engineers to remove protective covering.

With such an emphasis on energy efficiency, it’s no wonder that the construction industry is putting IR Windows to good use. Here, these optics play an integral role in the building sector’s aim to build more efficiently – again, in the form of thermography.

IR thermal imaging conducts the following duties:

  • Analyses how a building absorbs, retains, and radiates heat
  • Like the electricals sector – enables safe maintenance of electrical systems
  • Plays a part in the manufacturing QA process – and much more.

IR cameras are used within the metals sector and are imperative to recognising the dangerous substances that are commonly found within metallurgy – such as molten metal. However, IR isn’t solely used to analyse risk; cameras equipped with IR optics are also employed to reduce energy and detect insulation-related issues.

In the automobile sector, IR cameras are commonly used as a non-invasive method of investigation for a wide range of tasks.
These include:

  • Checking a vehicle’s engine for irregularities
  • Examining a vehicle’s brakes and tyres
  • Monitoring heated seats and rear windows for heat-related concerns – and much more.

That said, it’s not just a vehicle’s health that IR devices are employed for. LiDAR (light detection and ranging) also uses various IR optics and is a popular system that Knight Optical deals with regularly. LiDAR is increasingly being incorporated into today’s vehicles to improve safety on the road by helping drivers with sensor-based technology in hard-to-navigate environments.

As well as the automotive sector, there is a wide range of other industries that are switching on to the benefits of LiDAR.
These include the following areas:

  • Industrial
  • Robotics
  • Security
  • Logistics and many more.

Why Choose Knight Optical for your Application? 
Discerning customers rely on Knight Optical not only for the premium quality of our output and in-house state-of-the-art Metrology Laboratory and QA Department‘s capabilities but because – as well as a range of Stock Optics (available for next-day dispatch) – we also offer our optics as Custom-Made Components.

This year, we’re celebrating 30 years in business. With three decades’ experience under our belt and a whole host of long-standing world-renowned customers on our books, we are proud to have worked on some of the most ground-breaking innovations.

If you are looking for premium-quality, bespoke optical components, please do not hesitate to get in touch with a member of the Technical Sales Team today.