Light is a kind of electromagnetic wave, with the visible spectral of 0.38-0.76um, and the infrared spectral region of 0.76-1000um.The part of 0.76-3.0um is called reflected infrared light, and the part of 3.0-18um is called emitted infrared light. Short-wave infrared light SWIR is located in the non-visible light spectrum between near infrared (NIR) and long-wave infrared (IR). Its wavelength is between 0.9-1.7um, and its action is similar to photons in the visible light range; it behaves more like visible light rather than thermal energy in the infrared spectrum. Although the SWIR wavelength is relatively short, photons in this range are less susceptible to Rayleigh scattering caused by particles with smaller diameters, because their wavelengths are relatively long, which means that SWIR light can pass through smoke, fog or haze.
The SWIR lens is also an optical lens. The short-wave infrared light emitted by the lens group converges onto the image sensor, and the chip converts the photoelectric signal, and finally forms the gray image of the object. The SWIR lenses are similar to the visible light lenses and are mainly composed of an optical glass lens. However, the SWIR imaging lens group must be specially designed, optimized and prepared according to the SWIR wavelength. The anti-reflection coating is usually required to be greater than 75% in the 700-1900nm band, and in the 900-1700 nm band, The transmittance is greater than 80%. If we use a lens group designed for visible light to perform SWIR imaging, it will result in low image resolution (a significant decrease in resolution) and high optical aberration (and increase in optical aberration). The lens group and other optical elements (filters, windows, etc.) of the SWIR lens can use the same manufacturing process as the optical element of the visible light lens, so the manufacturing cost can be reduced.
SWIR lenses can be applied to semiconductor wafers, electronic boards or solar cell inspections, night or day safety monitoring, laser light energy analysis, non-destructive inspections of artworks, medical imaging, biometrics, aerial photography, food sorting, etc.