Research on the bandpass filter used for single-exposure multi-spectral ghost imaging system

Different from the traditional point-to-point imaging, multi-spectral ghost imaging retrieve the image information of the target by means of modulation and demodulation. In this paper, a single-exposure multi-spectral ghost imaging system based on a fixed phase modulator was built, and the development of thin-film devices in the system was completed. In the thin film, BK7 glass was chosen as the substrate, niobium oxide (Nb2O5) and silicon dioxide (SiO2) were used as the high and low refractive index materials, respectively. Based on the basic theory of optical thin film, the simulation analysis and the film system design were carried out by the film system design software, through setting up evaluation function for film optimization, the design of 450-700 nm band-pass film filter with an incidence angle of 0°-30° was realized and the research and development of this film was completed on OZZSQ900 box-type vacuum coating machine. Through optimizing deposition rate of SiO2 film, the surface defects and scattering loss of film were reduced. The residual evaporation deposition of film was analyzed, the fitting function between film thickness and residual evaporation deposition by least square method was established, monitoring ways was adjusted, residual evaporation deposition was reduced and the accuracy of film thickness control during preparation process was improved. From the test performed by Agilent Cary5000 spectrophotometer, the transmittance is less than 0.5% in the bands of 350-440 nm and 710-800 nm, and higher than 98% in the range of 450-700 nm at the incident angle of 0°-30°, which meets the requirements of the imaging system. The study has important practical significance and engineering value. Copyright ©2020 Infrared and Laser Engineering. All rights reserved.