After exposure the stored image is read-out using red He-Ne laser light. The laser light induces PSL in the phosphor which in turn emits characteristic blue light, the intensity of which is proportional to the number of absorbed incident X-ray photons. The luminescence is detected by a photomultiplier tube and then converted to a digital signal.
The raw spiral image is then corrected against a calibration image and converted to a Cartesian coordinate system. A separate calibration image is set up for each plate using a flood field from an radioactive source and is used to correct all images recorded by the plates. After read out the plate is erased more thoroughly by Tungsten lamps.