Patent Number: 051174472
Section: abstract

An image input apparatus including a camera tube having a photoconductive layer onto which an optical image is to be projected, a cathode for emitting an electron beam for scanning the photoconductive layer, a control electrode for controlling a beam current of the electron beam emitted from the cathode in accordance with a control voltage, and a mesh electrode having a frame, the apparatus further including a deflecting circuit for periodically deflecting the electron beam to scan the photoconductive layer. The deflecting circuit periodically deflects the electron beam to scan an area outside a restricted scanning area determined by the frame of the mesh electrode. A beam current control circuit is further added, if necessary, for generating a control voltage and applying the control voltage to the control electrode to control the beam current of the electron beam such that the electron beam does not collide with the frame of the mesh electrode during a period in which the electron beam scans the area outside the restricted scanning area.