Germanium Lens from Shanghai Optics

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Our germanium lenses have a high refractive index—the highest refractive index among readily available IR transmitters. It also exhibits minimal chromatic aberration due to low dispersion. Because of these properties, Ge lenses are ideal for use in infrared (FLIR and FTIR) field applications. Other applications include thermal imaging systems and precision analytic instruments which may be used in harsh environments.

It is the special hardness of germanium that gives it its unique ruggedness; Ge has a Knoop hardness of 780. It is a high density material, at 5.33 g/cm3, and allowances must be made for this weight if you are designing a weight sensitive system.

Germanium is also subject to thermal runaway. What this means is that the transmission will decrease as temperature increases, and the lens becomes opaque. Because of this thermal runaway effect, germanium lenses should only be used at temperatures below 100°C.

Germanium has optimal transmission (over 45%) in the 2-12 μm band, which makes it most useful for mid-infrared light. With anti-reflective coatings, transmission can be brought up to about 95%.

Germanium Lens Factory Specifications

Shanghai Optics manufactures quality germanium lenses in a range of popular sizes, from 5m m to 350 mm in diameter. Our standard anti reflective coating is best suited for light transmissions between 3 and 12 μm. The focal length of our lenses is determined up to a +/-1% tolerance, and the surface flatness is l/4 @ 633nm.

The surface quality of our factory standard germanium lenses is 20-10 scratch dig, after coating. This is considered precision quality and is suitable for most laser applications.

Germanium Optics Factory Standards