Patent ID: 6816573
Filing Date: 2004-11-09
Classification: G01N,H01J,H05G

Abstract:
An X-ray generating apparatus comprising:an X-ray tube for generating, within a housing sealed into vacuum, an X-ray by focusing an electron emitted from a cathode into an anode target by way of a first grid electrode, a second grid electrode, and a focusing electrode; grid voltage control means for controlling a grid voltage applied to said first grid electrode; and pulse generating means for generating a pulse which changes from an OFF state to an ON state and maintains said ON state for a predetermined period of time; wherein said first grid electrode is disposed on the focusing electrode side of said cathode, whereas said second grid electrode is disposed on the focusing electrode side of said first grid electrode; wherein said grid voltage control means has cathode current detecting means for detecting a cathode current and, in response to said pulse generated by said pulse generating means, applies a cutoff voltage to said first grid electrode when said pulse is in said OFF state so as to prevent said electron emitted from said cathode from reaching said anode target, and applies to said first grid electrode, in response to said pulse generated by said pulse generating means, a grid operating voltage adjusted such that said cathode current detected by said cathode current detecting means attains a predetermined value when said pulse is in said ON state; wherein said cathode current detecting means has a cathode current detecting resistor, connected to said cathode, for detecting said cathode current; and wherein said grid voltage control means has: an operational amplifier having one input terminal for inputting a voltage generated by said cathode current detecting resistor and the other input terminal for inputting a predetermined negative voltage or a reference voltage positive voltage; and a grid voltage control circuit for controlling, in response to an output from said operational amplifier, said grid voltage applied to said first grid electrode.