| 摘要 |
PURPOSE:To prevent the dew condensation of the equipment by sealing dry air for maintaining a dry state, and providing a gas sealed part which supplement gas when the gas leaks, a heat conduction type sensor which detected the degree of leak of the gas, and an alarm circuit. CONSTITUTION:When humidity sensors 4 and 4' are provided in a photographic lens for a TV camera, the humidity sensor 4 is arranged in the space formed of lenses which constitute a focusing group 10, the other humidity sensor 4' is arranged in the space between a compensator group 12 and an image-forming lens group 13, and the dry air is sealed in those spaces. Pipes 15 and 15' are communicated from outside a lens barrel 14 and pipes 17 and 17' which are linked to a dry gas cylinder (not shown in figure) through valves 16 and 16' opened and closed freely are linked to the pipes 15 and 15'; and the valves 16 and 16' are opened in response to the sound of the alarm circuit 7, e.g. buzzer to seal the dry air in the lens barrel 14 again.
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