Rotary recording medium having a guide track and recording and reproducing apparatus therefor

A recording and reproducing apparatus for recording and reproducing information on and from a rotary recording medium, said rotary recording medium comprising a recording surface upon which information is recorded, and a guide track which is a groove formed on said recording surface and having one of a spiral and a concentric shape, both edge lines of said groove having a wave shape that changes cyclically in a direction of a radius, said recording and reproducing apparatus comprising:

• a first light source irradiating a light beam to said recording surface so that the center of a spot is positioned to one side of said groove in said guide track,
• a second light source irradiating a light beam to said recording surface so that the center of a spot is positioned to another side of said groove in said guide track,
• first photoelectric conversion means for receiving a first reflected beam obtained by reflecting said light beam from said first light source on said recording surface and outputting a first signal corresponding to said first reflected beam,
• second photoelectric conversion means for receiving a second reflected beam obtained by reflecting said light beam from said second light source on said recording surface and outputting a second signal corresponding to said second reflected beam,
• first signal extraction means for extracting, from said first signal, a signal having a frequency component corresponding to said wave shape of one of the edge lines of said groove,
• second signal extraction means for extracting, from said second signal, a signal having a frequency component corresponding to said wave shape of the other edge line of said groove,
• tracking control means for controlling a position, in a direction of said radius, of said first and second light sources so that a central portion of spots of light beams from said first and second light sources is positioned on recording tracks formed on both sides of said guide track, on the basis of each of the signals extracted by said first and second signal extraction means, and
• means for simultaneously forming said recording tracks for the information on both sides of said guide track at a time of a recording and for simultaneously reproducing the recorded information from said recording tracks at a time of a reproduction.