These infrared filters are made of multiple layers of film stacked on top of each other, each with a different refractive index and thickness. When incident light strikes this filter, it is reflected and refracted at the interface of each film layer, resulting in an interference phenomenon. Only light of wavelengths that meet specific conditions can pass through the interferometric filters, while other wavelengths are reflected or absorbed. Interferometric infrared filters have the advantages of high transmittance, high selectivity, narrow bandwidth, and good temperature stability, but they also have the disadvantages of complex production process, high cost, and angle sensitivity.

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