| 摘要 |
<p>By being equipped with a computation/judgment unit (12), which computes the difference between the detection voltage from a light receiving element (32) when no light is being emitted from a light emitting element (23) and the detection voltage from the light receiving element when light is emitted from the light emitting element, and judges that there is no disk when the value of this difference is greater than a first difference threshold value, and judges that there is a disk when the difference value is less than the first threshold value and less than a second difference threshold value, disk detection can be accomplished without error, even when affected by external scattered light, increased dark current in the phototransistor, or deteriorated characteristics in the optical components (deterioration over time or environmental fluctuations).</p> |
