Optical storage device made thinner by substituting electrical means for capabilities of sensors

An optical storage device for reproducing information from and/or recording information on an optical storage medium by irradiating a light beam generated by a stationary optical unit incorporated in a main body onto said optical storage medium via a carriage, which moves in a radial direction of said optical storage medium within said main body, in a state in which said optical storage medium loaded in said main body is rotated, comprising:

• a cutoff frequency change means for temporarily setting the cutoff frequency of a filter means located on a path of a signal reproduced by way of said carriage to a normally-unused lower frequency immediately after said optical storage medium is loaded in said main body;
• a sector spacing detection means for detecting a spacing of sectors of said optical storage medium using a signal sent from said filter means;
• a position information memory means for storing positions in the radial direction of said optical storage medium, and frequencies and sector spacings associated with the positions;
• and
• a detection means for detecting the type of said optical storage medium and a position of a current reproduction track on the basis of a detected sector spacing and data stored in said position information memory means.