Patent ID: 8498378

Claim:
A method for controlling an emission of a beam of electrons in an X-ray imaging tube, the X-ray imaging tube comprising an anode and a cathode comprising a first emission device associated with a first assembly of polarizing plates located on either side of a first focusing cup and a second emission device associated with a second assembly of polarizing plates located on either side of a second focusing cup, wherein the method comprises: alternately emitting an accelerated incident beam of electrons from the first emission device onto a first focal point on the anode and from the second emission device onto a second focal point on the anode to generate X-rays; applying, to the first emission device, by an electric generator a first beam focusing voltage to at least one of the first assembly of polarizing plates and the first focusing cup; applying, to the second emission device, by an electric generator a second beam focusing voltage to at least one of the second assembly of polarizing plates and the second focusing cup; applying a first cut-off voltage to the first focusing cup to control the emission of the beam; and applying a second cut-off voltage to the second focusing cup to control the emission of the beam, wherein the first focal point has a first characteristic impact dimension and the second focal point has a second characteristic impact dimension, and wherein the first characteristic impact dimension and the second characteristic impact dimension are substantially equal.