Sunday, December 9, 2018

Germanium Lens


Germanium lens are made using germanium material which is a relatively hard, of high density, IR transmitting material. This material can block UV and VIS wavelengths. On the side it can allow IR from 2 µm.

Germanium material is very suitable for designing lens since its refractive index with the ability to support impossible specifications to be created. Common applications of germanium lens include thermal imaging where the Germanium material can be used as a front optic while its index of refraction helps the lens to support wide-angle lenses.

Germanium lens are best in mid-infrared applications. They work very well in harsh environments . Shanghai optics offers the most known sizes having Anti-Reflection Coatings. The lens is likely to be affected by thermal runaway in that, when the temperature goes high the transmission goes down.


The Germanium lens are specified to be used at temperatures not exceeding 100 degrees Celsius. 5.33 g/Cm3, which is the Germanium’s highest density is put into consideration when making designs for weight-sensitive systems. Germanium lens are very good in IR applications requiring rugged optics.

This is attributed by the Knoop Hardness which is 780. In summary, Germanium lens have high Index of Refraction, minimal Chromatic Aberration due to low dispersion, ideal for Rugged IR applications as well as having popular sizes containing AR coating from 3-12 µm.


Germanium lens can have various manufacturing limits which include; Anti-reflection coating of 3-12 µm, clear aperture having more than 85% of central dimension, surface figure of a quarter length each 633 nm, surface quality after coating of 20-10, Focal length of positive or negative one percent and lens of diameter 5 mm-350 mm. Additionally, Germanium lens can be manufactured containing different shapes like spherical plano-concave, P-Convex, Concave-Convex and Aspheric.


Germanium lens are tested with Zygo interferometer and spectrophotometer. This is the standard testing items which ensures the lens is of high quality.

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