Optical head with a tilt correction servo mechanism

Claim 2

An optical head device for recording and/or reproducing information on a recording surface of an optical disk, comprising: light source means for emitting rays of light; focussing means for converging a central portion of the rays emitted from said light source on an information track on the recording surface of the optical disk, whereby rays of light converged on the recording surface of the optical disk are reflected therefrom to form reflected rays of light; beam splitter means for separating from said rays emitted from the light source said reflected rays of light that are reflected from said recording surface of the optical disk and transmitted again through said converging lens means; first photodetector means for receiving and detecting said reflected rays of light that have passed through the converging lens means and have been separated by said beam splitter means, thereby reproducing information recorded on said track on the optical disk; characterised by deflecting means for refracting a portion of said rays of light emitted from said light source to a side spot on said recording surface of the optical disk situated to a side of the spot on the information recording track on which the central portion of the rays emitted from the light source is converged by the converging means; second photodetector means for receiving and detecting said portion of the rays of light which have been reflected at said side spot on the recording surface of the optical disk; calculation means, coupled to said second photodetector means, for calculating from an output of said second photodetector means a tilting of said recording surface of the optical disk with respect to the optical axis of the converging lens means, said calculation means outputting a signal corresponding to the calculated tilting of the recording surface of the optical disk; and actuator means, coupled to said calculation means, for adjusting, in response to said signal outputted from said calculation means, an attitude of said optical head device with respect to the recording surface of the optical disk so that the tilting of said recording surface with respect to the optical axis of the converging lens means is adjusted.

Claim 3

An optical head device for recording and reproducing information on a recording surface of an optical disk, comprising: light source means for emitting rays of light; converging lens means for converging a central portion of the rays emitted from said light source on an information track on the recording surface of the optical disk, wherein rays of light converged on the recording surface of the optical disk are reflected therefrom to form reflected rays of light; beam splitter means for separating from said rays emitted from the light source said reflected rays of light that are reflected from said recording surface of the optical disk and transmitted again through said converging lens means; first photodetector means for receiving and detecting said reflected rays of light that have passed through the converging lens means and have been separated by said beam splitter means, thereby reproducing information recorded on said track on the optical disk; refracting means, disposed at a peripheral portion of said converging lens means to form an integral piece therewith, for refracting a peripheral portion of said rays of light emitted from said light source to a side spot on said recording surface of the optical disk situated on a side of a spot on the information recording track on which the central portion of the rays emitted from the light source is converged by the converging means; second photodetector means for receiving and detecting said peripheral portion of the rays of light which have been refracted by said refracting means and thereafter been reflected at said side spot on the recording surface of the optical disk; calculation means, coupled to said second photodetector means, for calculating from an output of said second photodetector means a tilting of said recording surface of the optical disk with respect to an optical axis of the converging lens means, said calculation means outputting a signal corresponding to the calculated tilting of the recording surface of the optical disk; and actuator means, coupled to said calculation means, for adjusting, in response to said signal outputted from said calculation means, an attitude of said optical head device with respect to the recording surface of the optical disk so that the tilting of said recording surface with respect to the optical axis of the converging lens means is adjusted.

Claim 4

An optical head device for recording and reproducing information on a recording surface of an optical disk, comprising: light source means for emitting rays of light; converging lens means for converging a central portion of the rays emitted from said light source on an information track on the recording surface of the optical disk, wherein rays of light converged on the recording surface of the optical disk are reflected therefrom to form reflected rays of light; beam splitter means for separating from said rays emitted from the light source said reflected rays of light that are reflected from said recording surface of the optical disk and transmitted again through said converging lens means; first photodetector means for receiving and detecting said reflected rays of light that have passed through the converging lens means and have been separated by said beam splitter means, thereby reproducing information recorded on said track on the optical disk; refracting means, disposed at a peripheral portion of said converging lens means to form an integral piece therewith, for refracting a peripheral portion of said rays of light emitted from said light source to a side spot on said recording surface of the optical disk situated on a side of a spot on the information recording track on which the central portion of the rays emitted from the light source is converged by the converging means; second photodetector means for receiving and detecting said peripheral portion of the rays of light which have been refracted by said refracting means and thereafter been reflected at said side spot on the recording surface of the optical disk; calculation means, coupled to said second photodetector means, for calculating from an output of said second photodetector means a tilting of said recording surface of the optical disk with respect to an optical axis of the converging lens means, said calculation means outputting a signal corresponding to the calculated tilting of the recording surface of the optical disk; and actuator means, coupled to said calculation means, for adjusting, in response to said signal outputted from said calculation means, an attitude of said optical head device with respect to the recording surface of the optical disk so that the tilting of said recording surface with respect to the optical axis of the converging lens means is adjusted.

Claim 5

An optical head device as claimed in claim 2, wherein said refracting means comprises a prism formed at a flange portion of said converging lens means.

Claim 6

An optical head device as claimed in claim 2, wherein said refracting means comprises means for converging said peripheral portion of the rays refracted by said refracting means.

Claim 7

An optical head device for recording and reproducing information on a recording surface of an optical disk, comprising: light source means for emitting rays of light; first diffraction grating means for diffracting a central portion of the rays emitted from said light source, so as to resolve it into a plurality of pencils of rays; converging lens means for converging along an information track on the recording surface of the optical disk said plurality of pencils of rays into which a central portion of the rays emitted from said light source is resolved by said first diffraction grating means, wherein the pencils of rays converged on the recording surface of the optical disk are reflected therefrom to form reflected pencils of rays; beam splitter means for separating said reflected pencils of rays reflected from said recording surface of the optical disk from said pencils of rays into which the central portion of the rays emitted from the light source is resolved; first photodetector means for receiving and detecting said reflected pencils of rays that have been converged by the converging lens means and thereafter have been separated by said beam splitter means from the emitted rays, thereby reproducing information recorded on the information track on the optical disk and detecting a tracking error; second diffraction grating means, formed integrally with said first diffraction grating means at a side thereof, for diffracting a peripheral portion of said rays emitted from said light source means so as to deflect it and direct it via the converging lens means on a side spot on said recording surface of the optical disk that is situated to a side of the spots along the information track on which said pencils of rays are converged by said converging lens means; second photodetector means for receiving and detecting said peripheral portion of the rays of light which has been diffracted by said second diffraction grating means and thereafter has been reflected at said recording surface of the optical disk; calculation means, coupled to said second photodetector means, for calculating from an output of said second photodetector means a tilting of said recording surface of the optical disk with respect to an optical axis of the converging lens means, said calculation means outputting a signal corresponding to the calculated tilting of the recording surface of the optical disk; and actuator means, coupled to said calculation means, for adjusting, in response to said signal outputted from said calculation means, an attitude of said optical head device with respect to the recording surface of the optical disk so that the tilting of said recording surface with respect to the optical axis of the converging lens means is adjusted.

Claim 8

An optical head device for recording and reproducing information on a recording surface of an optical disk, comprising: light source means for emitting rays of light; first diffraction grating means for diffracting a central portion of the rays emitted from said light source, so as to resolve it into a plurality of pencils of rays; converging lens means for converging along an information track on the recording surface of the optical disk said plurality of pencils of rays into which a central portion of the rays emitted from said light source is resolved by said first diffraction grating means, wherein the pencils of rays converged on the recording surface of the optical disk are reflected therefrom to form reflected pencils of rays; beam splitter means for separating said reflected pencils of rays reflected from said recording surface of the optical disk from said pencils of rays into which the central portion of the rays emitted from the light source is resolved; first photodetector means for receiving and detecting said reflected pencils of rays that have been converged by the converging lens means and thereafter have been separated by said beam splitter means from the emitted rays, thereby reproducing information recorded on the information track on the optical disk and detecting a tracking error; second diffraction grating means, formed integrally with said first diffraction grating means at a side thereof, for diffracting a peripheral portion of said rays emitted from said light source means so as to deflect it and direct it via the converging lens means on a side spot on said recording surface of the optical disk that is situated to a side of the spots along the information track on which said pencils of rays are converged by said converging lens means; second photodetector means for receiving and detecting said peripheral portion of the rays of light which has been diffracted by said second diffraction grating means and thereafter has been reflected at said recording surface of the optical disk; calculation means, coupled to said second photodetector means, for calculating from an output of said second photodetector means a tilting of said recording surface of the optical disk with respect to an optical axis of the converging lens means, said calculation means outputting a signal corresponding to the calculated tilting of the recording surface of the optical disk; and actuator means, coupled to said calculation means, for adjusting, in response to said signal outputted from said calculation means, an attitude of said optical head device with respect to the recording surface of the optical disk so that the tilting of said recording surface with respect to the optical axis of the converging lens means is adjusted.

Claim 9

An optical head device as claimed in claim 5 wherein said second diffraction grating means comprises: a diffraction grating whose grating interval is varied gradually, and adjustment means for adjusting a position of the diffraction grating in a direction of grating interval variation.

Claim 10

An optical head device as claimed in claim 5 or 6, wherein said first and second diffraction grating means comprises diffraction gratings having a saw-tooth formed cross section.

Claim 11

An optical head device as claimed in claim 5, 6 or 7, further comprising an aperture limiter means for limiting an aperture of said converging lens means for the pencils of rays into which said central portion of the rays emitted from the light source means is resolved by said first diffraction grating means.

Claim 12

An optical head device as claimed in any of claims 1 to 8, wherein said second photodetector means comprises a pair of photodetector cells, and said signal outputted from said calculation means corresponds to a difference between two outputs of said pair of photodetector cells.

Claim 13

An optical head device for recording and reproducing information on a recording surface of an optical disk, comprising: light source means for emitting rays of light; converging lens means for converging a central portion of the rays emitted from said light source on an information recording track on the recording surface of the optical disk, wherein rays of light converged on the recording surface of the optical disk are reflected therefrom to form reflected rays of light; beam splitter means for separating said reflected rays of light reflected from said recording surface of the optical disk from said rays emitted from the light source; first photodetector means for receiving and detecting said reflected rays of light that are separated by said beam splitter means, thereby reproducing information recorded on the information track on the optical disk; reflection means for reflecting a peripheral portion of said rays of light emitted from said light source, thereby deflecting and directing it via said converging lens means, to a side spot on said recording surface of the optical disk situated to a side of a spot on the information track on which the central portion of the rays emitted from the light source is converged by the converging means; second photodetector means for receiving and detecting said peripheral portion of the rays of light which have been reflected by said reflection means and thereafter at said side spot on the recording surface of the optical disk; calculation means, coupled to said second photodetector means, for calculating from an output of said second photodetector means a tilting of said recording surface of the optical disk with respect to an optical axis of the converging lens means, said calculation means outputting a signal corresponding to the calculated tilting of the recording surface of the optical disk; and actuator means, coupled to said calculation means, for adjusting, in response to said signal outputted from said calculation means, an attitude of said optical head device with respect to the recording surface of the optical disk so that the tilting of said recording surface with respect to the optical axis of the converging lens means is adjusted.

Claim 14

An optical head device for recording and reproducing information on a recording surface of an optical disk, comprising: light source means for emitting rays of light; converging lens means for converging a central portion of the rays emitted from said light source on an information recording track on the recording surface of the optical disk, wherein rays of light converged on the recording surface of the optical disk are reflected therefrom to form reflected rays of light; beam splitter means for separating said reflected rays of light reflected from said recording surface of the optical disk from said rays emitted from the light source; first photodetector means for receiving and detecting said reflected rays of light that are separated by said beam splitter means, thereby reproducing information recorded on the information track on the optical disk; reflection means for reflecting a peripheral portion of said rays of light emitted from said light source, thereby deflecting and directing it via said converging lens means, to a side spot on said recording surface of the optical disk situated to a side of a spot on the information track on which the central portion of the rays emitted from the light source is converged by the converging means; second photodetector means for receiving and detecting said peripheral portion of the rays of light which have been reflected by said reflection means and thereafter at said side spot on the recording surface of the optical disk; calculation means, coupled to said second photodetector means, for calculating from an output of said second photodetector means a tilting of said recording surface of the optical disk with respect to an optical axis of the converging lens means, said calculation means outputting a signal corresponding to the calculated tilting of the recording surface of the optical disk; and actuator means, coupled to said calculation means, for adjusting, in response to said signal outputted from said calculation means, an attitude of said optical head device with respect to the recording surface of the optical disk so that the tilting of said recording surface with respect to the optical axis of the converging lens means is adjusted.

Claim 15

An optical head device as claimed in claim 10, wherein said second photodetector means comprises a pair of photodetector cells, and said signal outputted from said calculation means corresponds to a difference between two outputs of said pair of photodetector cells.

Claim 16

An optical head device as claimed in claim 10 or 11, wherein said second photodetector means is disposed next to said first photodetector means to receive the peripheral rays of light reflected from the recording surface of the optical disk via the converging lens means and the beam splitter means.

Claim 17

An optical head device as claimed in claim 10 or 11, wherein said second photodetector means is disposed on a flange portion of said converging lens means to receive the peripheral rays of light reflected at the recording surface of the optical disk directly therefrom.

Claim 18

An optical head device as claimed in claim 10 or 11, wherein said second photodetector means is disposed on a side of said converging lens means to receive the peripheral rays of light undergoing a reflective diffraction of first order at the recording surface of the optical disk.

Claim 19

An optical head device as claimed in any of claims 10 to 14, further comprising an aperture limiter means for limiting an aperture of said converging lens means for the central portion of the rays emitted from the light source means.

Claim 20

An optical head device as claimed in claim 10, wherein said second photodetector means comprises a linear position detector means, disposed on a substrate on which said first photodetector means is disposed, for detecting a linear position of the peripheral rays of light incident thereon after being reflected at the recording surface of the optical disk, the linear position detector outputting a signal corresponding to the detected linear position of the incident rays.

Claim 21

An optical head device for recording and reproducing information on a recording surface of an optical disk, comprising: light source means for emitting rays of light; converging lens means for converging the rays emitted from said light source on an information recording track on the recording surface of the optical disk, wherein rays of light converged on the recording surface of the optical disk are reflected therefrom to form reflected rays of light; beam splitter means for separating from said rays emitted from the light source said reflected rays of light that are reflected at said recording surface of the optical disk and transmitted again through said converging lens means; first photodetector means for receiving and detecting said reflected rays of light that have been separated by said beam splitter means, thereby reproducing information recorded on the track on the optical disk; reflection means for reflecting a portion of said rays of light emitted from said light source which is split via said beam splitter means from the portion directed to said converging lens means via said beam splitter means, to a side spot on said recording surface of the optical disk situated to a side of a spot on the information recording track on which the central portion of the rays emitted from the light source is converged by the converging means; second photodetector means for receiving and detecting said peripheral portion of the rays of light which have been reflected from said recording surface of the optical disk; calculation means, coupled to said second photodetector means, for calculating from an output of said second photodetector means a tilting of said recording surface of the optical disk with respect to an optical axis of the converging lens means, said calculation means outputting a signal corresponding to the calculated tilting of the recording surface of the optical disk; and actuator means, coupled to said calculation means, for adjusting, in response to said signal outputted from said calculation means, an attitude of said optical head device with respect to the recording surface of the optical disk so that the tilting of said recording surface with respect to the optical axis of the converging lens means is adjusted.

Claim 22

An optical head device for recording and reproducing information on a recording surface of an optical disk, comprising: light source means for emitting rays of light; converging lens means for converging the rays emitted from said light source on an information recording track on the recording surface of the optical disk, wherein rays of light converged on the recording surface of the optical disk are reflected therefrom to form reflected rays of light; beam splitter means for separating from said rays emitted from the light source said reflected rays of light that are reflected at said recording surface of the optical disk and transmitted again through said converging lens means; first photodetector means for receiving and detecting said reflected rays of light that have been separated by said beam splitter means, thereby reproducing information recorded on the track on the optical disk; reflection means for reflecting a portion of said rays of light emitted from said light source which is split via said beam splitter means from the portion directed to said converging lens means via said beam splitter means, to a side spot on said recording surface of the optical disk situated to a side of a spot on the information recording track on which the central portion of the rays emitted from the light source is converged by the converging means; second photodetector means for receiving and detecting said peripheral portion of the rays of light which have been reflected from said recording surface of the optical disk; calculation means, coupled to said second photodetector means, for calculating from an output of said second photodetector means a tilting of said recording surface of the optical disk with respect to an optical axis of the converging lens means, said calculation means outputting a signal corresponding to the calculated tilting of the recording surface of the optical disk; and actuator means, coupled to said calculation means, for adjusting, in response to said signal outputted from said calculation means, an attitude of said optical head device with respect to the recording surface of the optical disk so that the tilting of said recording surface with respect to the optical axis of the converging lens means is adjusted.

Claim 23

An optical head device as claimed in claim 17, wherein said second photodetector means comprises a pair of photodetector cells, and said signal outputted from said calculation means corresponds to a difference between two outputs of said pair of photodetector cells.

Claim 24

An optical head device as claimed in claim 17 or 18, wherein said reflecting means comprises a plane mirror and said optical head device further comprises a convex lens means for collimating said portion of the rays reflected by said reflection means.

Claim 25

An optical head device as claimed in claim 17 or 18, wherein said reflection means comprises a concave mirror.

Claim 26

An optical head device substantially as described with reference to any of Figures 8 to 35 of the drawings.

Claim 27

An optical head device substantially as described with reference to any of Figures 8 to 35 of the drawings.