Research On Large-diameter Infrared Tunable F-P Filter

As it developed quickly,laser weapon is very likely to be widely used in future wars as a powerful strategic weapon.In response to the threat of laser weapons for imaging system,filter-based laser protection solutions have been researched and applied,but they cannot effectively protect lasers with unknown wavelengths.The tunable Fabry-Perot(F-P)filter has the advantages of tunability,wide free spectral range,high control accuracy,stable structure,easy processing,etc.,which may effectively cover the shortage of optical filter with fixed length.It is expected that the protection scheme based on tunable F-P filters has application prospects in the field of laser protection.Aiming at the application requirements of medium-wave infrared laser protection,this thesis proposed and developed a tunable FP filter with large diameter that is driven by piezoelectric ceramic stack.The test results show that it can choose specific wavelength infrared light whose wavelength ranges from3 ?m to 5 ?m selectively through scanning cavity's length,and has good filtering performance.The main research contents of this thesis are as follows:(1)On the basic principle of tunable F-P filter,TFCalc software is used to design the optical film including high reflection film and antireflection film of F-P cavity.Then capacitive displacement sensor's probes were made on the surface of mirror,and piezoelectric ceramic stack was used as the driver to fabricate the infrared tunable F-P filter.(2)The infrared tunable F-P filter's control circuit based on the SMT32F407 ZGT single-chip microcomputer is designed and made,which has the function of cavity length control.At the same time,QT upper computer and STM32 computer control software supporting the circuit have been developed.(3)In order to improve the accuracy of F-P cavity's length control,a closed-loop control algorithm based on capacitive displacement sensor and an open-loop control algorithm based on Back Propagation(BP)neural network were designed and implemented respectively.(4)A test system for the tunable F-P filter was built.The driving voltage module of the circuit was tested,and the calibration of the capacitance displacement sensor was completed by using a color laser displacement meter,and the closed-loop control algorithm and the open-loop control algorithm were verified and evaluated,then they were compared on performance.The tunable F-P filter's infrared spectrum was tested by a fourier infrared spectrometer.Finally,the test of the cavity length scanning to capture the high transmittance peak of the F-P cavity was done.