Commonly Used Optical Components of Infrared Thermal Imagers—Germanium Lenses

The germanium crystal has a high refractive index and is only transparent to infrared light, but opaque to visible light and ultraviolet light. As an optical material, it has unique and excellent properties and can be used to make special infrared light-transmitting germanium windows, prisms, and lenses. The following is an introduction to the excellent applications of germanium glass in infrared optical systems.

Germanium glass has good light transmission performance in the 2-16μm waveband, and its chemical properties are relatively stable. It is not easy to react with metal oxides, acidic substances, air, and water. Infrared thermal imaging cameras generally work in a wavelength range of 2-13μm, while germanium glass has a very good light transmittance to the mid-and far-infrared wavebands, while ordinary optical glass has extremely low transmittance in these wavebands.

Plating an optical film on germanium glass can greatly increase the transmittance of infrared rays and reduce the reflectivity of the germanium glass surface. Generally, if germanium glass is used on the windows of infrared thermal imaging cameras and infrared thermometers, the transmittance of germanium glass is only 40-50% without coating, and the transmittance after antireflection coating can reach 90%.

Moreover, most customers also require DLC to be coated with diamond-like carbon film on germanium glass to strengthen the hardness of germanium glass and achieve a certain explosion-proof effect.

Germanium glass has a small change in refractive index and color heat bokeh. In the range of 1-14um, the germanium glass has no thermal defocusing, making it easier to design colors to correct the infrared optical system. It is also an ideal choice for applications combined with other infrared optical materials.

The content of germanium in the earth's crust is 2 parts per million, which is the 52nd most abundant element in the earth's crust. Germanium is one of the most dispersed elements in the earth's crust, and there are few ores containing germanium, so it has not been mined on an industrial scale for a long time. 

Germanium is called scattering element or scattering metal together with 7 elements of cadmium, gallium, indium, thallium, selenium, tellurium, and rhenium. The scattered metals play an important role in the development of high-tech and future energy. Therefore, infrared optical lenses that usually use germanium crystals are also more expensive.

In some infrared thermal imaging cameras, we can also use silicon crystals instead of germanium glass. Silicon (Si) single crystal is a chemically inert material with high hardness and is insoluble in water. It has good light transmission performance in the 1-7μm band, and it also has good light transmission performance in the far-infrared band, which is a feature that other infrared materials do not have.

Silicon (Si) single crystal is usually used for the substrate of 3-5μm mid-wave infrared optical windows and optical filters. Because of its good thermal conductivity and low density, it is also used to make laser mirrors or infrared temperature measurements and infrared optical lenses. Commonly used materials. But the operating band of silicon crystal is not as far as germanium glass.

The infrared optical lens designed and produced by QUANHOM is made of high-quality germanium crystal, which has good light transmittance in the mid-to-far infrared band, and we also have infrared optical elements made of silicon crystal and other infrared optical materials for you to choose from. If you want to know more about infrared optical lenses after reading the above, you can get professional solutions by contacting us.

With excellent R&D technology and high-quality product services, we have quickly become one of the leading manufacturers of Opto-electromechanical components. We are committed to the production of various thermal infrared lenses (including LWIR, MWIR, and SWIR). We have a professional production team and a strict quality inspection system, which can carry out a full range of quality control on the details of the product. At the same time, our thoughtful one-stop service and effective solution technology have won unanimous praise and trust from customers. If you are interested in our infrared optical lens, please contact us immediately!