| The use of a flexible,ordered fiber bundle(FB)for collection and delivery of infrared images is desirable in the extreme(e.g.under nuclear irradiation)or unfavorable environments(e.g.stray electromagnetic fields,in restricted spaces,etc.).It could be beneficial to optimize the structure and improve efficiency,as well as reduce the weight and volume of the system.Moreover,it has a great potential application in homeland security and defense,medical diagnostics and manufacturing industries.Therefore,there is tremendous value in studying the fabrication and properties of the flexible high-resolution infrared FBs.Up to date,the chalcogenide FBs were fabricated through the conventional ‘layer winding method' and‘acid-leaching method'.Due to their poor mechanical properties and low glass transition temperature resulting of the weak chemical bonds of the chalcogenides,the diameter of the chalcogenide fibers is hardly decreased less than 50?m,and their physical parameters,such as the thermal expansion coefficient,are not match those of the oxide soft glasses.Therefore,many technical problems should certainly be solved for the fabrication of the flexible,high-resolution chalcogenide FBs.In this paper,aiming to the fabrication method for the flexible chalcogenide FBs and achieving high-resolution infrared image transmission,the effects of different fabrication approaches on the resolution,filling rate,cross talk and the coupling effect of the FBs were investigated.The major works and obtained results are described as follows:(1)The mechanical strength of single fiber was improved by introducing high-performance thermoplastic polymer polyimide(PEI),whose characteristic temperature matches well with the chalcogenide glass,as the fiber cladding.The As2S3/PEI fiber bundle with 900 pixels was prepared via the multiple filament process,and the diameter of the single fiber is 80?m.It was calculated that the broken rate was1%,the resolution was 7 lp/mm and the cross talk rate was 1%.A clear image of an electric iron was obtained by using the fiber bundle as a transmission media.However,the large single fiber diameter and high cross talk rate limit the resolution of the fiber(2)bundle,which leads to fuzziness in the details of the obtained thermal image.(2)In order to further improve the resolution of the fiber bundle,a As2S3/PEI fiber bundle including 81000 single fibers was prepared via the multiple filament process.The diameters of the single fiber and As2S3 core were 10?m and 9?m,respectively.The cross section of the fiber bundle was found to be 110 mm2.It was calculated that the resolution was 45 lp/mm and the cross talk rate was ~2.5%.An image of an electric iron with clear details and consistent profile was obtained using this fiber bundle.After removing the PEI cladding,the fiber bundle became flexible,but the cross talk rate increased a lot resulting in image blurring.(3)To reduce the cross talk rate of the flexible fiber bundle,a monofilament perform with large core package radio was prepared by introducing a glass extrusion technique,which contains ~195 thousands As40S60/As38S62/PEI(core/inner cladding/outer cladding)single fibers.The cross section of the as-prepared fiber bundle was larger than 30mm2 and its cross talk rate was effectively reduced to 1.5%.In addition,the filling rate was increased by reducing the thickness of protective PEI cladding,which effectively improves the infrared imaging resolution of the fiber bundle..After dissolving the PEI with DMAC solvent,we finally obtained a flexible fiber bundle.(4)In order improve the coupling efficiency between the output surface of fiber bundle and the CCD detector,here we fabricated As2S3 fiber perform with square structure via a kind of glass extrusion process.By combining multiple filaments method,a As2S3/PEI fiber bundle with square arrangement were obtained.The filling rate was increased to 85%.Using this fiber bundle with square profile,the coupling problem between the output surface and the CCD detector was solved. |
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