Part 2: Optical Windows

Posted by  | 16th March 2021  | Optical Products

BK7 Windows Custom

In Part 1, we introduced you to Optical Windows – flat, plane-parallel, transparent optical surfaces designed to protect sensors and other electronic instruments from environment conditions.

They are used across medical, defence, instrumentation, laser, research and imaging sectors in a wide range of applications.

Here we look at substrate options for Optical Windows and review a range of specific options starting with Borosilicate Windows and Plates through to UV and IR Crystal Windows and Plates.

Optical Windows Substrate Options

As a recap on Part 1, we listed the range of substrates which can be used in Optical Windows:

Optical Windows from UQG Optics

All our Optical Windows are available from a standard range stock, while custom sizes and specifications can be custom-made to your specific design.

We stock a wide range of optical windows including:

Borosilicate Windows and Plates

Where optical windows and plates of high visual and optical clarity are needed, borosilicate glass sheets are optically polished before being cut to size. Optical polishing results in a high-quality precision surface finish and flatness. Borosilicate’s very low CTE (Coefficient of Thermal Expansion) gives it high strength integrity, ideal for optical flats, laser windows, mirrors and special camera windows with high transparency in visible and near IR & UV range of wavelengths used in optics, photonics and opto-electronics.

Coating Witness Pieces

Coating witness pieces are available for testing the application of optical coatings to test pieces of substrate. Coating witness pieces allow thin film coatings to be applied to test samples without using the finished part, for example to measure transmission, reflectivity, temperature, durability, polarization and salt fog tests across a wide range of materials for the UV to IR range. A wide range of thicknesses and diameters are available from stock and as custom options.

Flow Plates

Laser glass flow plates are used in laser systems as a protection plate to other components, often to reduce harmful radiation. Stock flow plates are made of doped Cerium glass but are non-browning so can withstand long periods of radiation without any colour change to the glass. Further radiation resistant glasses include borosilicate, quartz and UV fused silica. They are also used in camera protection windows and view windows in sensitive, high radiation environments.

IPL Glass Block Crystals

IPL (Intense Pulsed Light) Glass Blocks are made in Schott N-BK7. The IPL Glass block crystals have polished optical faces to ensure light is transmitted at a certain wavelength. They are used in laser equipment for beauty treatments such as hair removal, vascular therapy and skin rejuvenation, where protecting the skin is of critical importance. 

Lead Glass Windows and Plates

Lead glass windows offer excellent shielding protection against gamma radiation and x-rays. Schott RD50 has a high density, meaning high x-ray absorption relative to glass thickness. These optical windows and plates are widely used in vacuum systems for viewports and protection windows for instruments across science and industry. Circular lead glass windows or plates can be custom made in two surface finish grades, either optically polished for increased flatness or thickness tolerance and from standard polished sheet materials.

Optical Domes

Optical Domes are ideal for use in protective windows for visible and infrared applications for extreme environments. They have robust protective properties, making them ideal for use in underwater cameras and imaging applications for subsea high-pressure environments. At UQG Optics, optical domes are available in BK7, fused quartz, sapphire and UV fused silica.

Step Windows

Step Windows have a step ground into the edge or length of the glass to accommodate rings or sealant for seating into housing or mechanical assembly. Step Window materials include BK7, fused quartz, borosilicate and sapphire as well as a range of others, subject to thickness, which can be custom coated if required. Additional bevels and angles can be ground to the step for assembly and handling.

UV and IR Crystal Windows and Plates

UV and IR windows are used in a huge range of optical instruments, equipment and applications including thermography, laser spectroscopy and medical thermology equipment to FTIR analysis, excimer laser systems and in thermal imaging systems in defence and aerospace industries, life and medical sciences and many other wide and varied industrial optics for OEM applications. Substrates include barium fluoride, calcium fluoride, germanium, IR fused quartz, magnesium fluoride, silicon, zinc selenide and zinc sulphide.

Ask UQG Optics for advice on substrate properties and their suitability for specific applications.

Next Steps

If you would like to find out more about optical windows from UQG Optics, please contact us on 01223 420329 or email our sales team at