Design and fabrication of eye-safe laser ranging andinfrared imaging filter film

From the viewpoint of eye-safe, a filter film with 1 550 nm for laser ranging and 3 m～5 m spectral band for infrared imaging was designed and fabricated to inhibit 1 064 nm laser. In order to improve the mechanical strength of filter film, the thickness of every film layer was limited and the layers were reasonably arranged. ZnS and YbF3 were used as the materials and multi-spectral ZnS was used as the substrate. The filter film was fabricated by the electron beam deposition technique. Ion assisted deposition and vacuum annealing techniques were used to improve the stability of filter film. The result of spectrum measurement shows that the transmittance is only 0.5% for 1 064 nm laser and 99.3% for 1 550 nm laser, and the average transmittance is more than 99.6% for the range of 3.5 m～3.9 m. Although the refractive index of YbF3 increases in the process of deposition, the spectrum curve is not severely impacted. Environmental reliability tests were finished and results prove that the filter film is tolerant of harsh environment and can meet the requirement.