Fabrication of Thin Film Band-Pass Filter for Automotive Active Infrared Night Vision System

We reported the fabrication of thin film band-pass filter (800~1000 nm) for automotive active infrared night vision system.First, the thin films, comprising the low/high index SiO₂/Ta₂O₅ multi-layers and designed with software Macleod, were deposited on quartz substrate in OTFC-1300 reactor under the optimized deposition conditions.Next, the influence of the precision of films' thickness on the filter's transmittance was investigated in Newton iteration algorithm with MATLAB software and by experimentally evaluation.Two major problems, including low transmittance at band-pass center and large concussion on both spectral edges, were solved by optimizing the thickness of sensitive layers.Finally, the prototyped filter, fabricated with the optimized layer thickness, was experimentally tested.The results show that the band-pass filter meets the environmental requirements.For instance, its properties included:a transmittance over 99% in 800~1000 nm range, an average reflectance below 3% (2%) in 380~780 nm (1064~1270 nm) range.