An X-ray tube of an embodiment includes an anode; and an electron emission device. In an embodiment, the electron emission device includes at least one electron emitter including at least one emission surface and at least one barrier grid, the at least one barrier grid being spaced apart from the at least one emission surface of the electron emitter and includes a definable number of individually controllable grid segments. According to an embodiment, at least one individually definable grid voltage is applicable to each of the grid segments. In a simple manner, an electron-emission device of an embodiment permits the image quality to be adjusted with minimal anode loading.