Information recording and reproducing apparatus including detection of whether an information recording medium has been normally loaded into the apparatus

摘要

An information recording and reproducing apparatus includes a head unit for recording information on and reproducing information from an information recording medium having a plurality of linear tracks arranged in parallel, a device for moving the head unit relative to the recording medium, and a detector for detecting whether the record medium has been loaded into the apparatus in a normal state. The detector includes a photo-detection unit having a light projector for projecting a light beam to the recording medium and a photo-detector for detecting a light beam from the recording medium. The photo-detection unit is arranged such that when the recording medium is inserted in the normal state, the light beam from the light projector illuminates a track of the recording medium and the photo-detector detects high-order diffracted light from the illuminated track.