Image pickup tube utilizing third electrode and its operating method

A method for operating an image pickup tube, the image pickup tube comprising:

• a substrate;
• a target section including at least a photo-conductive film and a target electrode provided on said substrate;
• a mesh electrode located in opposition to said target section;
• scanning beam emitting means including a cathode electrode, opposed to the mesh electrode and located on the side opposite to the target section with respect to the mesh electrode, for emitting an electron beam and means for scanning the electron beam;
• and
• a control electrode, insulated from the target section, for controlling a surface potential of a non-scanned region of the target section while the image pickup tube operates, the control electrode having a terminal for receiving a control voltage applied thereto externally of the control electrode;
• wherein said photo-conductive film is made of an amorphous material mainly containing Se;
• the method comprising the steps of applying to said control electrode of said image pickup tube a voltage lower than that to be applied to the target electrode, and applying to said photo-conductive film an electric field of 0.8.times.10.sup.6 V/cm or more.

A method for operating an image pickup tube, the image pickup tube comprising:

• a bulb with its one end opened;
• a substrate for sealing the end of said bulb using an indium ring;
• an image pickup tube target section including a target electrode formed on the substrate within said bulb and a photo-conductive film formed on said target electrode;
• a mesh electrode located in opposition to said target section with said bulb;
• and
• scanning beam emitting means including a cathode electrode for emitting an electron beam and means for scanning the electron beam, said scanning beam emitting means being opposed to the mesh electrode and located on the side opposite to the target section with respect to the mesh electrode;
• and
• a control electrode for controlling a surface potential of a non-scanned region of the target section, said control electrode being located on the non-scanned region between said target section and said mesh electrode and electrically insulated from said target section and said mesh electrode, said control electrode having a terminal for receiving a control voltage applied thereto externally of said control electrode;
• the method comprising the step of operating said image pickup tube under the following condition:
• Vk<Vg<Vm.multidot.(Lg/Lm), and
• Vg<Vt
• where Vg represents a control electrode voltage, Vk represents a cathode electrode voltage, Vm represents a potential difference between the mesh electrode and the cathode electrode, Vt represents a potential difference between the target electrode and the cathode electrode, Lg represents the distance between the photo-conductive film and the control electrode, and Lm represents the distance between the photo-conductive film and the mesh electrode.

A method for operating the image pickup tube, the image pickup tube comprising:

• a bulb with its one end opened;
• a substrate for sealing the end of said bulb using an indium ring;
• an image pickup tube target section including a target electrode formed on the substrate within said bulb and a photo-conductive film formed on said target electrode;
• a mesh electrode located in opposition to said target section with said bulb;
• and
• scanning beam emitting means including a cathode electrode for emitting an electron beam and means for scanning the electron beam, said scanning beam emitting means being opposed to the mesh electrode and located on the side opposite to the target section with respect to the mesh electrode;
• and
• a control electrode for controlling a surface potential of a non-scanned region of the target section, said control electrode being located on the non-scanned region between said target section and said mesh electrode and electrically insulated from said target section and said mesh electrode, said control electrode having a terminal for receiving a control voltage applied thereto externally of said control electrode;
• wherein said photo-conductive film is made of an amorphous material mainly containing Se;
• the method comprising the steps of applying to said control electrode of said image pickup tube a voltage lower than that to be applied to the target electrode, and applying to said photo-conductive film an electric field of 0.8.times.10.sup.6 V/cm or more.