X-ray tube with capacitively coupled filament drive

DETAILED DESCRIPTION In accordance with the present invention, an x-ray tube is provided in which an evacuated envelope and a filament contained therein undergo relative rotational movement.
A capacitive coupling conveys electrical power from an AC source across the envelope to the filament disposed in the interior of the envelope.
In accordance with a more limited aspect of the present invention, the capacitive coupling includes annular rings disposed interior and exterior to the evacuated envelope in a capacitively coupled relationship.
In accordance with a more limited aspect of the present invention, the envelope includes a cylindrical side wall extending generally perpendicular to an anode affixed thereto for rotation therewith.
The annular side wall passes between the interior and exterior capacitive coupling rings.
In accordance with another more limited aspect of the present invention, a plurality of cathode filaments are provided.
A means is provided for applying current primarily to a selected one of the filaments.
In accordance with a more limited aspect of the present invention, the means for providing current to a selected one of the filaments includes an adjustable resonance circuit for establishing a resonance condition with only a selected one of the filaments.
In this manner, electrical power is supplied primarily to the filament in resonance and substantially no electrical power is supplied to the filament(s) which is out of resonance.
One advantage of the present invention is that it allows direct power connections with the filament The filament current is directly measurable.
Another advantage of the present invention is that it reduces parasitic losses.
Another advantage of the present invention is that it is more compact than air core transformers, permitting a reduction in the size of the x-ray tube.
Still further advantages of the present invention will be come apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments