| Adding diffractive optical elements in the infrared imaging system, not only can reduce the size and weight of the system, but also makes the system unique function of de-dispersion and athermalization. Currently, the single point diamond turning technology is the main manufacture processing for infrared diffractive optical element. Those elements haven’t yet to realize mass production and large-scale applications. Therefore, it is necessary to study a new process technology for the mass production of infrared diffractive optical element. Therefore, this thesis presents the molding manufacture technology of infrared diffractive optical element.The main process of molding manufacture infrared diffractive optical elements that is studied in this thesis is as follows:Firstly, use a hard anti-stick mold molded the heat-softened infrared glass in the uniform heating vacuum environment and maintained a suitable time, and then removed the pressure. Finally, we got the infrared diffraction optical elements after a presetting annealing cooling program.The hard mold that is used for molding infrared glass is Si mold, which is made by single point diamond turning. In addition, the Si mold was used as master mask, we firstly transfered the diffraction microstructure to the epoxy resin resist etching layer on SiC base by the micro molding technology, and then transfered the diffraction microstructure to the base through the ICP etching to produce the SiC mold with higher hardness and longer service life.In SiC mold manufacturing, the paper studies process parameters of the polymer corrosion resistant layer microstructure molding and the ICP etching transfer microstructure. In polymer corrosion layer microstructure molding part, the thesis studies the influence on the results under the hot-pressing method, soft molding method and with different polymer materials. Use the PDMS soft mold to soft-mold epoxy resist layer at room temperature. After 24 hours curing, the microstructure is integral. Profile dimensions meet the requirements and error keeps under 0.03%. The surface roughness is 6-8nm. In ICP etching transfer microstructure part, the thesis studied different process parameters on etching rate and the effects of etching rate. Experiments show that under the parameters that SF6 flow is 60sccm, O2 flow is 2sccm, ICP power is 1000w, bias power is 40w, temperature is 30℃, and pressure is 30mTorr, the SiC etching rate is 118.67nm/min, and the epoxy etching rate is 329.90nm/min. The SiC/epoxy resin etching ratio is stable at 1:2.78. The etching rate is suitable for the transfer of microstructures.In infrared glasses molded part, the paper have studied the influence of results under the different mold temperature and heating methods. Eventually the molding parameters determined as follows:for the heating process, raised the room temperature to 200℃ in 40 min and kept 20 min; and then raised it to 350℃ in 40 min and kept 20 min; at last raised it to 430 ℃ in 40 min and kept 30 min with 9.6kg pressure. The cooling process is as follows. First, cooled down the furnace temperature from 430℃ to 350℃ and kept 2 h for stress relieving. And then let the sample cooling with the furnace. Remove the sample after the cooling process finished. The result shows that:infrared glasses fully fill the mold profile, microstructure have no deformation or dislocation, and the diffraction microstructures size, which measured by the contact measuring instrument, meet the requirements well. Profile dimensions error keep under 0.03%. The surface roughness is 6-8nm. |
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