X-ray body scanner using encoder for generating system controlling timing pulse train

X-ray apparatus for examining at least a portion of a body by scanning successive layers of said body with a rotating x-ray beam and detecting the x-radiation along the beam that emerges from each body layer as it is scanned, comprising:

• rotatable means that are rotatable through substantial angles about a longitudinal axis that is substantially normal to the layers of the body portion to be examined,
• x-ray source means having a fixed focal spot from which an x-ray beam originates and x-ray detector means mounted on said rotatable means and spaced angularly relative to each other about said axis and being on opposite sides of said axis for orbiting jointly about a body portion when it is disposed between said source and detector means, the relationship between said focal spot, said axis and said detector means being unaltered during said orbiting,
• means cooperating with said source means for defining the radiation emanating from said source means into a beam that is directed toward said detector means,
• motor means operatively coupled with said rotatable means for driving said rotatable means to effect scanning of a body portion solely by said joint orbiting of said focal spot and detector means, means for maintaining functions of said apparatus in predetermined relationships comprising encoder means having shaft means coupled to said rotatable means and including means responsive to rotation of said shaft means by producing a train of timing pulses in which each pulse corresponds with a fractional degree of rotation of said rotatable means, and
• means responsive to occurrence of successive predetermined numbers of said timing pulses by controlling said x-ray source means to turn on for the duration of a predetermined number of timing pulses, to thereby provide x-radiation pulses at repeatable angular increments of said rotatable means.