The single crystal of germanium used in semiconductor is less absorption in the infrared wavelength of 2 - 20μm and it can be used as an optical element of the infrared light. It is a single lens which was made with the germanium crystal. It is used as a lens of a camera to observe the infrared, such as thermography.
◦Even though it looks like the light does not transmit because of its metallic luster, it is transmitting through a wide infrared range of 2 - 20μm.
◦The wavelength of 1.5μm or less does not transmit, so it also provides the effect of an infrared transmission filter.
◦Since the silicon lens has a refractive index of 4 or more, the lens curvature is slower then when made from standard glass.
It is available with an AR coating to reduce the transmission loss by reflection at the requested wavelength.
Remark
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Attention
Germanium lens can have metallic luster, so that visible light is reflected and absorbed. Because of this, no transmittance occurs.
Germanium lens without an anti-reflection coating has a loss due to surface reflection and results in transmittance of about 40%.
For the observation of infrared wavelengths, it is necessary to consider the effect of the radiation spectrum by temperature. In case of using in an environment of 30℃ or more, radiant light of infrared (near 9.6μm) is emitted from all substances, and it will not be able to properly observe this infrared spectrum.
Image Label
Germanium Plano Convex Lens 50mm Focal Length
Focal length
50mm
Material
Germanium (Ge)
Design Wavelength
10.6μm
Coating
Uncoated
Surface reflectance
36% at 5μm
Shape Type
Plano Convex spheric (Polished surface on both sides)
The single crystal of germanium used in semiconductor is less absorption in the infrared wavelength of 2 - 20μm and it can be used as an optical element of the infrared light. It is a single lens which was made with the germanium crystal. It is used as a lens of a camera to observe the infrared, such as thermography.