Apparatus for optically reproducing signals recorded on a rotating recording medium

Claim 1

An apparatus for optically reproducing signals recorded on a rotating recording medium, said signals comprising an information signal recorded along track turns disposed in a mutually side-by-side arrangement on the recording medium and at least one kind of reference signal recorded along the track turns and in the central part between the centerlines of mutually adjacent track turns, said reference signals overlapping the lateral edges of said adjacent track turns of the information signal, said information signal being recorded in a form of a succession of pits formed on a substantially flat surface of the recording medium, the depth of said pits being substantially uniform, said apparatus comprising: means for producing a first light beam; means for producing a second light beam; optical system means for projecting said first and second light beams to form spots on the surface of said recording medium so that the light beams are reflected from said surface of said recording medium, said optical system means receiving said first and second light beams as they are reflected from said surface of said recording medium, the width in the track transverse direction of the first light beam spot on the recording medium being substantially the same as the transverse width of each of said track turns, said optical system means including an objective lens having a depth of focus which is substantially equal to or less than two times said uniform pit depth; first detecting means for detecting said reflected first light beam to produce a reproduced signal which comprises a reproduced information signal and at least one reproduced reference signal; means for separating the reproduced reference signal from the reproduced signal and for producing a tracking control signal in response to the reproduced reference signal; tracking control means responsive to said tracking control signal for controlling the optical system means so that the center of the first light beam spot follows along the centerline of each of said track turns; second detecting means for detecting said reflected second light beam to produce a focus control signal; and focus control means responsive to said focus control signal for controlling the distance of said objective lens with respect to the recording medium so that said first light beam is focused on approximately said substantially flat surface of the recording medium or on bottoms of the information signal pits.

Claim 2

An apparatus for optically reproducing signals recorded on a rotating recording medium, said signals comprising an information signal recorded along track turns disposed in a mutually side-by-side arrangement on the recording medium and at least one kind of reference signal recorded along the track turns and in the central part between the centerlines of mutually adjacent track turns, said reference signals overlapping the lateral edges of said adjacent track turns of the information signal, said information signal being recorded in a form of a succession of pits formed on a substantially flat surface of the recording medium, the depth of said pits being substantially uniform, said apparatus comprising: means for producing a first light beam; means for producing a second light beam; optical system means for projecting said first and second light beams to form spots on the surface of said recording medium so that the light beams are reflected from said surface of said recording medium, said optical system means receiving said first and second light beams as they are reflected from said surface of said recording medium, the width in the track transverse direction of the first light beam spot on the recording medium being substantially the same as the transverse width of each of said track turns, said optical system means including an objective lens having a depth of focus which is substantially equal to or less than two times said uniform pit depth; first detecting means for detecting said reflected first light beam to produce a reproduced signal which comprises a reproduced information signal and at least one reproduced reference signal; means for separating the reproduced reference signal from the reproduced signal and for producing a tracking control signal in response to the reproduced reference signal; tracking control means responsive to said tracking control signal for controlling the optical system means so that the center of the first light beam spot follows along the centerline of each of said track turns; second detecting means for detecting said reflected second light beam to produce a focus control signal; and focus control means responsive to said focus control signal for controlling the distance of said objective lens with respect to the recording medium so that said first light beam is focused on approximately said substantially flat surface of the recording medium or on bottoms of the information signal pits.