Patent Number: 
Section: claims

1. An X-ray tube comprising:an electron emission unit comprising a cold cathode,wherein the electron emission unit is divided into a first region A and a second region B, andwherein the electron emission unit is formed in a square shape, and the first region A comprises a square in a center of the electron emission unit that it inclined at 45 degrees to edges of the emission unit, and the second region B comprises four corners of the electron emission unit surrounding the first region A;an anode unit comprising a target unit disposed opposite to the electron emission unit, with which electrons emitted from the electron emission unit collide;a focus structure disposed between the electron emission unit and the target unit disposed on a surface of the anode unit that is opposed to the electron emission unit;a first transistor TA connected to the first region A;a second transistor TB connected to the second region B; anda controller configured to turn ON/OFF the first region A and the second region B independently by selectively maintaining ON and OFF gate-cathode potentials in the first transistor TA and the second transistor TB respectively, andwherein collision regions at the anode unit of electron beams emitted from the first region A and the second region B substantially coincide with each other. 2. The X-ray tube according to claim 1, whereinthe first region A comprises a center region, andthe second region B comprises one or more peripheral regions surrounding the center region. 3. The X-ray tube according to claim 2, wherein an area of the center region and a total area of the one or more peripheral regions are substantially equal to each other.