Description
Germanium is widely used because of its high refractive index, large transmission distance range and robust mechanical properties. Optical grade germanium crystal has a wide infrared transmission band (available in both 3~5μm and 8~12μm bands) and is a good material for making infrared optical lenses, mostly used in thermal imaging cameras and infrared lasers. However, germanium is subject to thermal fugacity, i.e., the transmittance decreases as the temperature increases.
Custom Germanium (Ge) Convex Lens with AR coating for Thermal Camera Sensor
Specifications
Material: | Ge |
---|---|
Diameter: | 2 mm |
Focal Length: | 15 mm |
Edge Thickness, Te: | 0.12 mm |
Lens Type: | Plano-Convex |
Surface Quality: | 60-40, 40-20, or better |
Surface Accuracy: | λ/2, λ/4 or better |
Coating: | AR+DLC or Customer Request |
Features
- High Refractive Index – Germanium has a high refractive index (~4.0 at 10.6 µm), making it suitable for infrared applications.
- Infrared Transparency – It is highly transparent in the 2–14 µm wavelength range, ideal for thermal imaging and IR optics.
- Low Dispersion – Germanium exhibits minimal chromatic aberration in the infrared spectrum due to its low dispersion.
- High Density – With a density of ~5.33 g/cm³, it is relatively heavy compared to other optical materials.
- Temperature Sensitivity – Its refractive index changes significantly with temperature, affecting optical performance in varying environments.
- Durability and Hardness – Germanium is mechanically strong and resistant to scratches, making it suitable for rugged applications.
- Absorption in Visible Spectrum – It is opaque to visible light, limiting its use to infrared applications.
- AR Coating Compatibility – To reduce surface reflections, anti-reflective coatings like DLC or BBAR are commonly applied.
Applications
- Thermal Imaging Systems – Used in infrared cameras and thermal imaging devices for defense, surveillance, and industrial applications.
- Infrared Spectroscopy – Employed in IR spectrometers for chemical analysis and material identification.
- CO2 Laser Optics – Used in 10.6 µm CO₂ laser systems for cutting, welding, and engraving applications.
- Night Vision Devices – Integrated into night vision and IR detection systems for military and security purposes.
- Medical Imaging – Applied in thermal diagnostic tools for detecting temperature variations in medical examinations.
- Environmental Monitoring – Utilized in gas detection and remote sensing systems to analyze atmospheric conditions.
- Aerospace and Defense – Incorporated into targeting, guidance, and surveillance systems in military and aerospace applications.
- Hyperspectral Imaging – Used in IR hyperspectral cameras for geological mapping, agriculture, and food safety analysis.
Frequently Asked Questions
What are the advantages of using germanium plano-convex lenses in infrared applications?
Germanium plano-convex lens have high infrared transparency (2–14 µm), a high refractive index (~4.0), and excellent durability, making them ideal for thermal imaging, spectroscopy, and CO2 laser systems.
Why is germanium not used for visible light applications?
Germanium is opaque to visible light, as it strongly absorbs wavelengths below approximately 2 µm, limiting its applications to the infrared spectrum.
What anti-reflective coatings are commonly applied to germanium lens?
Common AR coatings for germanium lenses include broadband anti-reflective (BBAR) coatings and diamond-like carbon (DLC) coatings, which help reduce surface reflections and enhance transmission.
What are the mechanical properties of germanium that make it suitable for rugged environments?
Germanium is a hard and dense material (density ~5.33 g/cm³), offering high resistance to scratches and mechanical stress, making it suitable for harsh environments such as aerospace and military applications.
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