Optical disc reproducing apparatus with mechanical shock detection

An optical disc reproducing apparatus comprising:

• an objective lens for focusing a light beam from a light source on a disc surface as a light spot;
• a focus actuator for driving the objective lens in the vertical direction to the disc surface;
• a light detector for converting the reflected light from the disc surface into an electric signal;
• a focus error signal generator for generating a focus error signal having a magnitude which represents a vertical deviation of the focal point from the disc surface;
• a first comparator for comparing the magnitude of the focus error signal with a predetermined first reference level and outputting a defocus representing signal when the magnitude of the focus error signal exceeds the first reference level;
• a reflected light intensity detector for detecting a reflected light intensity from the disc surface based on the output from the light detector;
• a second comparator for comparing the reflected light intensity with a predetermined second reference level;
• a signal monitor coupled to the first and second comparators for monitoring the time at which the reflected light intensity decreases below the second reference level and the time at which the defocus representing signal is outputted by the first comparator;
• and
• a lens evacuator for driving a focus actuator to evacuate the objective lens from the disc surface when the signal monitor detects that the reflected light intensity decreases below the second reference level in the second comparator within a prescribed period of time after the first comparator outputs the defocus representing signal.