| 摘要 |
PROBLEM TO BE SOLVED: To reduce radiation of hot rays to a monitor camera by arranging a transparent plate member exhibiting high light transmittance in a visible ray zone and low light transmittance in a hot ray radiation zone in an inspection hole made through a heat insulating wall and disposing the monitor camera on the outside of the transparent plate oppositely thereto. SOLUTION: A transparent plate member 3 coated with a tin oxide based film to exhibit high light transmittance in a visible ray zone and low light transmittance in a hot ray radiation zone is disposed on the outside of an inspection hole made through a heat insulating wall 1. A tubular body 5 is provided on the outside of the transparent plate member 3 while penetrating the furnace shell 7 and a monitor camera 13 such as a CCD video camera is disposed at the outer end part of the tubular body 5 through a heat shielding plate 12. A rodlike optical fiber 14 is laid in the tubular body 5 from the front face of the monitor camera 13 to a position proximate to the transparent plate member 3. According to the arrangement, radiation of hot rays to the monitor camera 13 can be reduced significantly.
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