| 摘要 |
PURPOSE:To prevent contamination due to photo-electric material by forming at least one of plural electrodes arranged between the input and output faces with a fixed and a movable electrodes then covering the necessary electrode with the movable electrode when forming a photoelectric face. CONSTITUTION:Grid electrodes 17-19 and an anode electrode 20 are arranged between the input and the output faces 13 16. The input face 13 is held between a cathode ring 14 and a support ring 15 where the cathode ring 14 is formed with a fixed electrode 24 to be supported on an enclosure 12 and a non- reversible movable electrode 25 comprising three telescopable coaxial tubular members 26-28 arranged at the inside. When forming a photoelectric face where photoelectric material is dispersed from a generator 33, necessary electrode is covered with the movable electrode 25 and displaced by applying vibration upon formation. Consequently, contamination due to photoelectric material is prevented resulting in improvement of contrast.
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