What Do You Know about Optical Windows?

Mar. 06, 2021

Optical windows are flat, optically transparent panels, typically designed to maximise transmittance over a specified wavelength range while minimising reflection and absorption. They are typically used to protect optical systems and electronic sensors from the external environment. As windows do not introduce optical power into the system, they should be selected based on the transmission characteristics of the material, the optical surface specification and the mechanical characteristics to match your application.

Material properties

Material properties including light transmission, refractive index and window substrate hardness are critical in determining which window is the best choice for your application.


The density of the glass is important as it helps determine the weight of the optical components, which is critical for weight-sensitive applications. Typically, the refractive index of glass increases as density increases. However, the relationship between refractive index and density is not linear.

Coefficient of thermal expansion

The coefficient of thermal expansion describes how the size of a glass will vary with temperature. This property is a key factor in applications involving extreme temperatures and rapid temperature differences.

Rectangular Window

Kupfer Hardness

The Knoop hardness of a glass is a measure of its resistance to indentation. It is determined by applying a fixed force to a given indenter and measuring the depth of the final indentation. The smaller the indentation, the higher the Knoop hardness. As a rule, materials with a high Noah's hardness are less brittle and can withstand greater indentation differences than materials with a low Noah's hardness.

Optical surface specifications

The surface specification of an fiber optic window affects optical performance and must be taken into account when selecting or specifying a window. It is important to ensure that your optical window has the right specification in terms of sealing to meet the requirements of your application, but over-toleranced windows can unnecessarily increase costs.

Surface quality

The surface quality of an optical window is an assessment of the surface defects that may be caused during manufacture or handling. These defects typically result in a small reduction in throughput and a small increase in scattered light, which in most imaging or spotting applications has little or no adverse effect on overall system performance. However, certain surfaces are more sensitive to these defects, such as surfaces in the image plane, where surface defects have come into focus. Windows with high power levels are also sensitive to surface defects as they can lead to increased energy absorption and damage to the window.

Surface quality is usually described by the scratch specification in the American Standard MIL-PRF-13830B. Scratch names can be determined by comparing scratches on a surface to a set of standard scratches under controlled lighting conditions. This is not a direct measure of the size of the scratch itself. On the other hand, the name of the excavation is directly related to the size of the excavation. The excavation name is calculated by multiplying the diameter in microns by 10.

As a optical lenses manufacturer,Tian Cheng Optics Co., Ltd. mainly manufacture high precision optical components such as spherical lens, cylindrical lens, prism, filter, window, mirror, beamsplitter, waveplate, polarizer, rod Lens and micro optics. Our products were approved by many special companies from United Kingdom, Germany, Austria, Switzerland, Italy, Ireland, Sweden, Australia, Israel, U.S.A. etc.

If you want to get more information about high quality optical window price,please contact us.


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