STRAIN CORRECTING DEVICE FOR X-RAY IMAGE TUBES

摘要

An external magnetic field (m) intruding into an electron lens area (23) from outside an X-ray image tube (11) is detected by a magnetic field sensor (32). A magnetic field for offsetting the external magnetic field (m) is generated by a coil (33) arranged in an input surface area (21) of the X-ray image tube (11), so that the distortion is corrected by removing the effects of the external magnetic field (m). The magnetic field sensor (32) is arranged in an area surrounded by a magnetic shield (20) of the X-ray image tube (11) and constituting an outer peripheral area on the electron lens area (23) side distant from the input surface area (21) of the X-ray image tube (11). The magnetic field sensor (32) is such that the effects of the magnetic field generated by the coil (33) arranged on the input surface area (21) side of the X-ray image tube (11) are reduced and the external magnetic field (m) intruding into the electron lens area (23) is accurately detected. A distortion correcting apparatus (31) of the X-ray image tube (11) can thus automatically correct the distortion.