X-ray CT apparatus

An X-ray CT apparatus, comprising:

• a gantry including a substantially cylindrical rotary section and a stationary section rotatably holding the rotary section;
• rotation detecting means for detecting the rotation of the rotary section to generate a rotation detecting signal, said rotation detecting means including a target section to be detected, which is mounted to one of said rotary section and said stationary section to impart a periodic change in the magnetic flux in the rotating direction of the rotary section, and a rotation detecting sensor mounted to the other of the rotary section and the stationary section with a gap provided between said target section to detect the change in the magnetic flux generated in the target section in accordance with rotation of the rotary section and to generate a rotation detecting signal in accordance with detection of the change in the magnetic flux;
• a sensor for detecting a reference position of the rotary section to generate a reference position detecting signal;
• calculating means for calculating at least one of the rotating position and the rotating speed of the rotary section on the basis of said detection signal, said calculating means calculating the rotating position of the rotary section on the basis of the reference position signal generated from a position sensor and the rotating speed of the rotary section and also calculating a correction amount conforming with the position from said rotation detecting signal;
• and
• moving means for slightly moving said rotation detecting sensor relative to said target section in accordance with said correcting amount to maintain constant the gap between the target section and the rotation detecting sensor.

An X-ray CT apparatus, comprising:

• a gantry including a substantially cylindrical rotary section and a stationary section rotatably holding the rotary section;
• rotation detecting means for detecting the rotation of the rotary section to generate a rotation detecting signal, said rotation detecting means including a ring-like target section to be detected, which is mounted to any one of said rotary section and said stationary section and having a periodic slit pattern formed therein, and an optical sensor mounted to the other of said rotary section and said stationary section in a manner to face said target section to detect the light ray passing through the slit pattern of the target section in accordance with rotation of the rotary section and, thus, to generate a detection signal;
• correcting means for correcting the rotation detecting signal;
• and
• calculating means for calculating at least one of the rotating position and the rotating speed of the rotary section on the basis of a corrected detecting signal from said correcting means.

An X-ray CT apparatus comprising:

• a gantry including a substantially cylindrical rotary section and a stationary section rotatably holding the rotary section;
• detectable means, mounted on one of the rotary section and the stationary section, for applying a periodical change on a magnetic flux generated in a circumferential space which is coaxially defined around said rotary section;
• detecting means, mounted on the another of the rotary section and the stationary section, for detecting the change of the magnetic flux which is produced due to the rotation of the rotary section, to generate a rotation detecting signal;
• and
• calculating means for calculating at least one of the rotating position and the rotating speed of the rotary section on the basis of the detecting signal from said detecting means,
• wherein said detectable means includes a gear having tooth tips, and
• wherein said detecting means includes means for applying the magnetic flux in the circumferential space, and a magneto-resistance element for producing a change in the resistance corresponding to the change in said magnetic flux to generate an electric signal.

An X-ray CT apparatus comprising:

• a gantry including a substantially cylindrical rotary section and a stationary section rotatably holding the rotary section;
• motor for directly driving the rotary section to rotate the rotary section;
• ring-shaped detectable section mounted on one of the rotary section and the stationary section and having a plurality of slits periodically arranged on said section;
• detecting means, mounted on the another of the rotary section and the stationary section, for detecting light rays passing through the slit to generate a rotation detecting signal;
• and
• means for generating an encoded signal based on the rotation detecting signal from said detecting means.