An X ray imaging apparatus is provided. The X ray imaging apparatus (100) comprising: an X ray source unit (101) including an X ray source for emitting an X ray beam the X ray source unit being movable such that the X ray beam to be emitted is movable along an axis (X) an X ray detecting unit (102) comprising an X ray detector (12) for detecting the X ray beam the X ray detecting unit (102) being movable along the axis (X) and a control unit (105) adapted to control the movement of the X ray detecting unit (102) in response to a movement of the X ray source unit (101) wherein the X ray source unit (101) further includes a laser for emitting a laser beam (La) for indicating a center of the X ray beam along the axis (X) the X ray detecting unit (102) further comprises a plurality of sensors (104) arranged along the X axis (X) each of the plurality of sensors (104) being configured to sense the laser beam (La) and to generate a sensor signal (S S2 S3 S4 S) indicative of its sensing of the laser beam (La) and the control unit (105) is adapted to control the movement of the X ray detecting unit (102) based on the sensor signals (S S2 S3 S4 S) generated by the plurality of sensors.
