| 摘要 |
PURPOSE:To regulate the light transmittance of a viewing window in accordance with the intensity of light emitted in a vacuum treating apparatus by fitting two polarizing plates to the window and turning one of the plates so as to cause relative displacement. CONSTITUTION:A frame 2 is tightly fixed on the end of the viewing window fitting part 1 of the body of a vacuum treating apparatus. A glass plate 4, a gasket 5, a fixed polarizing plate 6, a gasket 7 and a movable polarizing plate 8 are tightly fixed on the frame 2 in succession with an O-ring 3 in-between by means of a cap 9. The movable polarizing plate 8 is turned at about 90 deg. angle. The inner polarizing plate 6 may be made movable. The quantity of light transmitted is set at a value optimum for observation by changing the relative angle between the two polarizing plates 6, 8. |
