Germanium, a semi-metallic element (atomic number 32, symbol Ge) is highly suitable for midwave and longwave infrared optics even though it is obviously opaque to visible band light.

Another concern to the thermographic process is the transmittance of radiation by the lens optic elements. If an optic material is as irregular as the media the radiation summary produced by the camera, firmware, and software could be tremendously suspect. Fortunately, Germanium, a semi-metallic element (atomic number 32, symbol Ge) is highly suitable for midwave and longwave infrared optics even though it is obviously opaque to visible band light. Germanium is expensive, very refractive-that is to say, it bends light aggressively-and temperature changes can result in significant focus shifting.

FLIR T1020 Camera in HDPE Plastic Bag Graphic
Consider that longwave thermographic cameras can be contained in high density polyethylene (HDPE) bags to protect them from a hostile environment during assays as HDPE is overwhelmingly transmissive to thermographically-relevant longwave radiation.

Germanium lenses are generally coated; such coatings are not necessarily chemically inert nor tremendously durable. Germanium Dioxide-GeO2-is a coating also used to discourage the natural interactions with oxygen in the atmosphere by Germanium.

Germanium trends toward longwave infrared opacity at high temperatures (nearing 100° C); to obviate this problem, always operate your thermal cameras within the ambient specifications provided by the manufacturer.

Be perfectly complaint to manufacturer’s recommendations for chemistry when cleaning a Germanium lens, and never use materials that are physically traumatic to the lens.

This video (2:46) explores Germanium as an optic for Longwave Thermal Infrared cameras.

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Author

Expertise: Defensible extreme-specification forensic and research LiDAR (LASER Scanning) and thermographics, near-infrared & visible band imagery (photography, videography, time lapse, macro- and microphotography & video). Environmental controversies including water temperatures, geotechnics, and erosion volumetrics, architectural illumination. Construction, engineering, and craning operations and incidents. Color management, color science, and human visual acuity relevant to litigation. Certified Level II (Advanced) and Level III (Master, Managerial) Thermographer; FLIR Infrared Training Center. Certified Terrestrial LiDAR operator; theory, planning, and data interpretation; FARO Technologies, GmbH. Certified Aerial Photographer (Professional Aerial Photographers Association, International). Certified Master Aerial Photographer (Professional Aerial Photographers Association, International: one of ~50 to ever receive the award as of 7/18). OSHA 30 Certified (General Industry). Adobe Certified Expert: Photoshop (CS4, CS5, CS6, CC). Adobe Certified Expert: Premiere Pro (CS6, CC). Adobe Certified Expert: Flash Professional (CS5, CS6, CC). Adobe Certified Expert: Web Specialist (CS6). Adobe Certified Expert: Video Specialist (CS6, CC; 1 of 105 in the world as of 7/18). (Inactive) Member, Professional Advisory Board, Stevens-Henager College. (Inactive) Moderator for Adobe's online Photoshop, Premiere, & Flash forums. (Inactive) Lecturer, Law Seminars International.

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