An automatic disc eject device for a disc-loading tray of an optical disc drive comprises: a disc-loading frame, a movable disc-loading piece and a pivot. The image data of the scene is captured with a sensor, and comprises a plurality of spectra. The screws built in the screw extruders, respectively, include pressure portions with the feed rate per revolution progressively decreased toward the forward end extrusion port, and extended portions with the feed rate per revolution progressively increased toward the forward end extrusion port. The timing of occurrence of the events is detected and, on the basis of the timing detection, the direction of rotation of the tone ring is determined.