Recorder and player apparatus stably keeping track of recording medium

Patent metadata

Field	Value
Publication number	US-9911449-B2
Application number	US-201615377044-A
Country	US
Kind code	B2
Filing date	Dec 13, 2016
Priority date	Mar 9, 2016
Publication date	Mar 6, 2018
Grant date	Mar 6, 2018

Abstract

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. The first and seventh photosensors are positioned between the third and fourth photosensors in the direction parallel to the centerline. The second and eighth photosensors are positioned between the fifth and sixth photosensors in the direction parallel to the centerline. The first photosensor receives overlapped light of the 0th-order light with the +1st-order diffracted light, the second photosensor receives overlapped light of the 0th-order light with the −1st-order diffracted light, each of the third to sixth photosensors receives the 0th-order light, and does not receive the +1st-order diffracted light and the −1st-order diffracted light, and each of the seventh and eighth photosensors receives at least the 0th-order light.

First claim

The invention claimed is:

1. 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, and
wherein the tracking servo circuit controls the tracking servo mechanism so as to reduce a tracking error signal TE:
TE= SA−SB−k 1×( SCa+SCb−SDa−SDb )− k 2×( SE−SF ),

where SA, SB, SCa, SCb, SDa, SDb, SE, and SF denote signal levels of the output signals of the first to eighth photosensors, respectively, and k1 and k2 denote constant coefficients, respectively.

2. The recording and playing apparatus as claimed in claim 1 ,
wherein the tracking servo circuit sets a value of the constant coefficient k1, such that a change in an average level of the tracking error signal TE, the change occurring when a part of the plurality of optical elements is moved in a direction of movement of the tracking servo mechanism, is smaller than a change in a case of k1=0.

3. The recording and playing apparatus as claimed in claim 1 ,
wherein the tracking servo circuit sets a value of the constant coefficient k2, such that a change in an average level of the tracking error signal TE, the change occurring when the light generated by the light source is converged on a boundary track between recorded tracks and unrecorded tracks of the recording medium, is smaller than a change in a case of k2=0.

4. The recording and playing apparatus as claimed in claim 3 ,
wherein the tracking servo circuit sets a different value of the constant coefficient k2 depending on a pitch and a depth of the track of the recording medium.

5. The recording and playing apparatus as claimed in claim 1 ,
wherein, when the center of the 0th-order light coincides with the optical axis, each of the seventh and eighth photosensors covers the 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
wherein the tracking servo circuit sets a predetermined constant coefficient k2, upon writing and reading information on and from a recording medium satisfying:
sin(λ/ P )≧1.1×NA,

where λ denotes a wavelength of the light generated by the light source, P denotes a pitch of the track, and NA denotes a numerical aperture of an object lens of the optical system.

6. The recording and playing apparatus as claimed in claim 1 ,
wherein, when the center of the 0th-order light coincides with the optical axis, each of the seventh and eighth photosensors covers the 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
wherein the tracking servo circuit sets k2≈−1, upon writing and reading information on and from a recording medium satisfying:
sin(λ/ P )<1.1×NA,

where λ denotes a wavelength of the light generated by the light source, P denotes a pitch of the track, and NA denotes a numerical aperture of an object lens of the optical system.

7. The recording and playing apparatus as claimed in claim 1 ,
wherein, when the center of the 0th-order light coincides with the optical axis, the seventh photosensor covers the region on which overlapped light of the 0th-order light with the +1st-order diffracted light is incident, and the eighth photosensor covers the region on which overlapped light of the 0th-order light with the −1st-order diffracted light is incident, and
wherein the tracking servo circuit sets a predetermined constant coefficient k2, upon writing and reading information on and from a recording medium satisfying:
sin(λ/ P )<NA,

where λ denotes a wavelength of the light generated by the light source, P denotes a pitch of the track, and NA denotes a numerical aperture of an object lens of the optical system.

8. The recording and playing apparatus as claimed in claim 1 ,
wherein, when the center of the 0th-order light coincides with the optical axis, the seventh photosensor covers the region on which overlapped light of the 0th-order light with the +1st-order diffracted light is incident, and the eighth photosensor covers the region on which overlapped light of the 0th-order light with the −1st-order diffracted light is incident, and
wherein the tracking servo circuit sets k2≈−1, upon writing and reading information on and from a recording medium satisfying:
sin(λ/ P )≧NA,

where λ denotes a wavelength of the light generated by the light source, P denotes a pitch of the track, and NA denotes a numerical aperture of an object lens of the optical system.

9. The recording and playing apparatus as claimed in claim 1 ,
wherein, when the center of the 0th-order light coincides with the optical axis, the seventh photosensor covers a subregion on which overlapped light of the 0th-order light with the +1st-order diffracted light is incident, and a subregion 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 the eighth photosensor covers a subregion on which overlapped light of the 0th-order light with the −1st-order diffracted light is incident, and a subregion 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
wherein the tracking servo circuit se

Assignees

• Panasonic Ip Man Co Ltd

Inventors

• Momoo Kazuo
• Asada Junichi
• Kobayashi Yasushi
• Sano Kousei
• Takahashi Yuichi

Classifications

• G11B7/0901 Primary

  for track following only (G11B7/0925, G11B7/094, G11B7/0941, G11B7/0943, G11B7/0945, G11B7/0946, G11B7/0948 take precedence) · CPC title

• G11B7/133

  Shape of individual detector elements · CPC title

• G11B7/0943

  Methods and circuits for performing mathematical operations on individual detector segment outputs · CPC title

• G11B7/094

  Methods and circuits for servo offset compensation · CPC title

• G11B7/131

  Arrangement of detectors in a multiple array · CPC title