Germanium Lens – The "Invisible Eye" of Infrared Systems. Crafted from high-purity single-crystal germanium with a refractive index of 4.0, it achieves over 45% transmittance in the 2–14 μm wavelength range, which can exceed 98% with anti-reflective coating. It features minimal chromatic aberration, excellent thermal stability, and can withstand extreme temperature fluctuations from -200°C to +200°C. It is an essential lens for thermal imaging, CO? lasers, automotive night vision, temperature guns, and drone payloads. The surface undergoes diamond turning and ion beam polishing, resulting in a roughness of <5 nm and surface accuracy of λ/10. It can be coated with DLC hard film for scratch resistance, salt fog resistance, and mold resistance, meeting military standard MIL-STD. Common specifications include diameters of 3–200 mm and focal lengths from 5 mm to 2 m. It can be designed in various structures such as double-convex, plano-convex, aspheric, and diffractive hybrid to achieve lightweight and athermalized designs. Future trends include ultra-thin wafer-level stacking, nano-imprinted diffractive surfaces, and wafer-level packaging, enabling infrared modules to become as miniaturized and low-cost as smartphone cameras, ushering in an era of universal night vision.