Recorder and player apparatus stably keeping track of recording medium

A recording and playing apparatus for writing and reading information on and from a recording medium having a plurality of tracks disposed at a predetermined pitch, the recording and playing apparatus comprising:

• a light source;
• a photo detector;
• an optical system including a plurality of optical elements, the optical system converging light generated by the light source onto a track of the recording medium, and transmitting 0th-order light, +1st-order diffracted light, and −1st-order diffracted light, which are reflected by the recording medium and then incident to an incident surface of the photo detector;
• a tracking servo mechanism that keeps track of the recording medium;
• and
• a tracking servo circuit that controls the tracking servo mechanism based on output signals of the photo detector,
• wherein the photo detector includes first to eighth photosensors, each of the first to eighth photosensors generating an output signal depending on incident light,
• wherein the photo detector has a centerline on the incident surface, the centerline passing through an intersection of an optical axis of the optical system and the incident surface, and the centerline extending in a direction corresponding to a tangential direction of the track,
• wherein the first, third, fourth, and seventh photosensors are disposed on one side with respect to the centerline, and the second, fifth, sixth, and eighth photosensors are disposed on another side with respect to the centerline,
• wherein the third and fourth photosensors are disposed such that the first and seventh photosensors are positioned between the third and fourth photosensors in the direction parallel to the centerline,
• wherein the fifth and sixth photosensors are disposed such that the second and eighth photosensors are positioned between the fifth and sixth photosensors in the direction parallel to the centerline,
• wherein, when a center of the 0th-order light coincides with the optical axis, the first photosensor covers a region on which overlapped light of the 0th-order light with the +1st-order diffracted light is incident, the second photosensor covers a region on which overlapped light of the 0th-order light with the −1st-order diffracted light is incident, each of the third to sixth photosensors covers a region on which the 0th-order light is incident, and on which the +1st-order diffracted light and the −1st-order diffracted light are not incident, and each of the seventh and eighth photosensors covers a region on which at least the 0th-order light is incident,
• wherein the seventh photosensor covers a plurality of subregions, each of the subregions generates an output signal depending on incident light,
• wherein the eighth photosensor covers a plurality of subregions, each of the subregions generates an output signal depending on incident light, and
• wherein the tracking servo circuit selects at least one of a plurality of output signals corresponding to the plurality of subregions of the seventh photosensor, and selects at least one of a plurality of output signals corresponding to the plurality of subregions of the eighth photosensor, depending on at least one of a pitch of the track, a depth of the track, and recording film characteristics of the recording medium.

A recording and playing apparatus for writing and reading information on and from a recording medium having a plurality of tracks disposed at a predetermined pitch, the recording and playing apparatus comprising:

• a light source;
• a photo detector;
• an optical system including a plurality of optical elements, the optical system converging light generated by the light source onto a track of the recording medium, and transmitting 0th-order light, +1st-order diffracted light, and −1st-order diffracted light, which are reflected by the recording medium and then incident to an incident surface of the photo detector;
• a tracking servo mechanism that keeps track of the recording medium;
• and
• a tracking servo circuit that controls the tracking servo mechanism based on output signals of the photo detector,
• wherein the photo detector includes first to eighth photosensors, each of the first to eighth photosensors generating an output signal depending on incident light,
• wherein the photo detector has a centerline on the incident surface, the centerline passing through an intersection of an optical axis of the optical system and the incident surface, and the centerline extending in a direction corresponding to a tangential direction of the track,
• wherein the first, third, fourth, and seventh photosensors are disposed on one side with respect to the centerline, and the second, fifth, sixth, and eighth photosensors are disposed on another side with respect to the centerline,
• wherein the third and fourth photosensors are disposed such that the first and seventh photosensors are positioned between the third and fourth photosensors in the direction parallel to the centerline,
• wherein the fifth and sixth photosensors are disposed such that the second and eighth photosensors are positioned between the fifth and sixth photosensors in the direction parallel to the centerline,
• wherein, when a center of the 0th-order light coincides with the optical axis, the first photosensor covers a region on which overlapped light of the 0th-order light with the +1st-order diffracted light is incident, the second photosensor covers a region on which overlapped light of the 0th-order light with the −1st-order diffracted light is incident, each of the third to sixth photosensors covers a region on which the 0th-order light is incident, and on which the +1st-order diffracted light and the −1st-order diffracted light are not incident, and each of the seventh and eighth photosensors covers a region on which at least the 0th-order light is incident,
• wherein the first photosensor covers a plurality of subregions, each of the subregions generates an output signal depending on incident light,
• wherein the second photosensor covers a plurality of subregions, each of the subregions generates an output signal depending on incident light, and
• wherein the tracking servo circuit selects at least one of a plurality of output signals corresponding to the plurality of subregions of the first photosensor, and selects at least one of a plurality of output signals corresponding to the plurality of subregions of the second photosensor, depending on at least one of a pitch of the track, a depth of the track, and recording film characteristics of the recording medium.