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KMID : 1159320130150030217
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Korean Journal of Vision Science
2013 Volume.15 No. 3 p.217 ~ p.226
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The fabrication and characteristic for H-α imaging narrow bandpass optical filter by e-beam deposition
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Park Moon-Chan
Ko Kyun-Chae
Lee Wha-Ja
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Abstract
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Purpose: The H-α imaging narrow bandpass optical filter with a 656.3nm central wavelength and 8nm FWHM was designed and fabricated, and its characteristics and structure were studied.
Method: The bandpass filter with 656.3nm central wavelength and IR cut?off filter using Ti3O5/SiO2 multilayer were made by electron beam evaporation apparatus and the transmittaces of the filters were measured by spectrophotometer. The number of layers and the thicknesses of filters were measured from the cross section of IR cut-off filter by SEM image and the structures of the bandpass filter and IR cut-off filter and AR coating layer of IR cut-off filter were known by XRD and the composition of bandpass filter was analysed by XPS analysis.
Results: The optimization of the narrow bandpass layer for H-α filter was composed of 30 layers and that of AR coating layer was composed of 6 layers and that of IR cut-off layer was composed of 32 layers. The maximun central wavelength of fabricated H-imaging filter have a little tolerance of 0.7nm when compared to the designed peak wavelength. XRD patterns from the bandpass filter and anti-reflective coating layer were found to be amorphous, the infrared cut-off filter was coated as a crystal growth. It was known that the IR cut-off filter was composed of 32 layers by SEM image and the top layer of bandpass filter was SiO2 layer by XPS analysis.
Conclusions: The H-α filter combing 30 layers bandpass filter and 32 layers IR cut-off filter with a 657nm central wavelength and 8nm FWHM using Ti3O5/SiO2 mutilayer was designed and fabricated, and it was known that the transmittance and FWHM of fabricated H-α filter were similar to that of designed H-α filter.
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KEYWORD
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H-α imaging filter, IR cut-off filter, narrow bandpass filter, Ti3O5/SiO2 multilayer
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