An apparatus and method of detecting a missing nozzle in an ink jet print head can detect a missing nozzle with a simple process when the missing nozzle is generated. The method provides for grouping and chronological ordering of a plurality of exams for a patient according to attributes and allows the plurality of exams to be forwarded to a scheduling system for simultaneously scheduling all exams such that restrictions imposed during the grouping process are met. An electrically-conductive component extends from one electrode to the other in contact with the phase-change material. Preferably, the intensity of the light emitted by the LEDs varies with the light level of the image to be displayed by the display device. Rotation of a capstan motor is controlled in accordance with sync signal time difference information output from the sync signal time difference detection circuit, thereby performing a highly accurate tracking control not affected by jitter or eccentricity.