“Soul germanium glass” of infrared thermal imager lens
The infrared thermal imager receives the infrared radiation emitted by the object through the lens and reflects it to the detector to form an infrared image with temperature. Different colors represent different temperatures. The lens of an infrared thermal imager can transmit infrared rays, but ordinary cameras cannot. Why?
1. Ordinary camera lens material
The lens of ordinary camera is usually made of optical glass, which can refract light to amplify objects. Optical glass is generally synthetic. The exposure of ordinary cameras to infrared rays is insufficient. The main reason may be the photosensitive element, followed by the lens. The attenuation degree of the lens of the ordinary camera to the infrared ray mainly depends on the material of the lens, the coating and the wavelength of the infrared ray. The infrared ray transmission near the visible light is relatively high.
2、 Infrared thermal imager lens material
The lens of the infrared thermal imager is made of germanium glass, which is in the range of 2-16 μ M-band has good light transmission performance and stable chemical properties, and is not easy to react with metal oxides, acidic substances, air and water. The general working band of infrared thermal imager is 2-13 μ m. Germanium glass has good transmittance to mid far infrared, and ordinary optical glass has very low transmittance in these bands. Coating the optical film on the germanium glass can greatly increase the infrared transmittance and reduce the reflectivity of the germanium glass surface, but the germanium glass is not transparent in the visible light band.
Germanium is a rare metal element, and it is very difficult to extract high concentration germanium. The first ore containing germanium is very small, but germanium is very dispersed, and there is almost no concentrated germanium ore. Therefore, the production cost of germanium glass is relatively high, and the selling price in the market is higher than that of ordinary optical glass. Therefore, the price of infrared thermal camera lens is higher than that of ordinary camera.