Magnetic field correction method and apparatus.

摘要

Method and apparatus in an x-ray image intensifier tube 22. The invention features an intensifier tube including a photo cathode 24 for generating photo-electrons and a screen 25 for receiving those electrons after they have been accelerated through the length of the intensifier tube. A metallic shield or housing 27, 28, 29 is positioned about the space between photo cathode 24 and screen 25 and a multiturn conductive wire or coil 30 is positioned about the exterior surface of the shield and connected to a source of potential 23. The current through the wire is governed to cancel uniformly the earth's natural geomagnetic field throughout the entire interior region of the evacuated tube. This step reduces image degradation due to forces on the electron as they travel from the photocathode to the screen. Circuitry 38 is included for changing the current as the intensifier tube is re-oriented in the earth's field during x-ray diagnostic procedures.