EP0354019A2 — Optical head device for reading information store…

Claim 1

Independent Claim 130 words

An optical head device for reading information stored in a recording medium wherein a light beam from a light source is converged on an optical disk and a reflected beam from the optical disk is received by a light receiving element thereby to read out information stored in the optical disk is characterized in a diffraction element comprising: first diffraction gratings for dividing a light beam from the light source into a 0th order diffracted beam utilized for reading out the information stored in the optical disk and a pair of first order diffracted beams utilized for reading tracking errors; and second diffraction gratings for guiding the reflected beam from the optical disk to the light receiving element, said first and second diffraction gratings being positioned in the same plane.

Claim 2

Dependent Claim 130 words

An optical head device for reading information stored in a recording medium wherein a light beam from a light source is converged on an optical disk and a reflected beam from the optical disk is received by a light receiving element thereby to read out information stored in the optical disk is characterized in a diffraction element comprising: first diffraction gratings for dividing a light beam from the light source into a 0th order diffracted beam utilized for reading out the information stored in the optical disk and a pair of first order diffracted beams utilized for reading tracking errors; and second diffraction gratings for guiding the reflected beam from the optical disk to the light receiving element, said first and second diffraction gratings being positioned in the same plane.

Claim 3

Dependent Claim 65 words

An optical head device for reading information stored in a recording medium according to Claim 1 wherein said diffraction element comprises a plurality of regions which are separated from each other and formed in the same plane, and a specified plurality of regions of said regions respectively have the second diffraction grating and the other regions of said regions respectively have the first diffraction grating.

Claim 4

Dependent Claim 65 words

An optical head device for reading information stored in a recording medium according to Claim 2 wherein a function for dividing a light beam into a 0th order diffracted beam and first order diffracted beams and filter function are applied to said first diffraction grating by changing the diffraction efficiency of 0th order diffracted beam and first order diffracted beam in said first diffraction grating.

Claim 5

Dependent Claim 139 words

An optical head device for reading information stored in a recoding medium according to Claim 2 wherein said diffraction element comprises six regions formed in the same plane separately from each other, and is designed such that said second diffraction grating is formed in each of two regions out of four regions located in the vicinity of both ends of said diffraction element and in each of two regions located in the vicinity of the center of said diffraction element, said ends and center being set in a corresponding direction to the radial direction of the optical disk, while said first diffraction grating is formed in each of the other two regions located in the vicinity of both ends of said diffraction element, said ends being set in a corresponding direction to the radial direction of the optical disk.

Claim 6

Dependent Claim 132 words

An optical head device for reading information stored in a recording medium according to Claim 2 wherein said diffraction element comprises five regions formed in the same plane separately from each other, and is designed such that said second diffraction grating is formed in each of two regions located in the vicinity of one end of said diffraction element and in each of two regions located in the vicinity of the center of said diffraction element, said end and center being set in a corresponding direction to the radial direction of the optical disk, while said first diffraction grating is formed in one region located in the vicinity of the other end of said diffraction element, said end being set in a corresponding direction to the radial direction of the optical disk.

Claim 7

Dependent Claim 47 words

An optical head device for reading information stored in a recording medium according to Claim 2 wherein said light receiving element comprises a photodetector having a plurality of photodetecting sections which are separated from each other corresponding to the plurality of independent regions of said diffraction element.

Claim 8

Dependent Claim 32 words

An optical head device for reading information stored in a recording medium according to Claim 6 wherein said light receiving element comprises a photodetector having five photodetecting sections separated from each other.

Claim 9

Dependent Claim 110 words

An optical head device for reading information stored in a recording medium according to Claim 2 wherein said diffraction element is designed such that the transmission factors of 0th order diffracted beam of the first and/or second diffraction gratings in the regions located in the vicinity of both ends of the diffraction element, said ends being set in a corresponding direction to the radial direction of the optical disk, are lower than those of the first and/or second diffraction gratings in the regions located in the vicinity of the center of the diffraction element, said center being set in a corresponding direction to the radial direction of the optical disk.

Claim 10

Dependent Claim 118 words

An optical head device for reading information stored in a recording medium according to Claim 8 wherein the depths of the second diffraction gratings in the regions located in the vicinify of at least one end of the diffraction element, said end being set in a corresponding direction to the radial direction of the optical disk, is differentiated from the depths of the second diffraction gratings in the regions located in the vicinity of the center of the diffraction element, said center being set in a corresponding direction to the radial direction of the optical disk, so that the diffraction element has a different transmission factors of 0th order diffracted beam at least one end and the center.

Claim 11

Dependent Claim 137 words

An optical head device for reading information stored in a recording medium according to Claim 8 wherein said diffraction element is designed such that a light beam emitted from the light source passes through the second diffraction grating in the diffraction element to produce a 0th order light which is irradiated and reflected at the optical disk, and then further divided into a 0th order diffracted beam and first order diffracted beams at a different second diffraction grating in the diffraction element and thereafter one of said first diffracted beams reaches on a parting line between the adjacent photodetecting sections in the photodetector, thereby causing a focus servo-mechanism to move a beam spot on the optical disk according to the surface vibration of the optical disk in order to detect the information stored in the optical disk.

Claim 12

Dependent Claim 110 words

An optical head device for reading information stored in a recording medium according to Claim 8 wherein said diffraction element is designed such that a light beam emitted from the light source passes through a second diffraction grating in the diffraction element to produce a 0th order light which is irradiated and reflected at the optical disk, and then further divided into a 0th order diffracted beam and first order diffracted beams at a different second diffraction grating in the diffraction element and thereafter one of said first diffracted beams reaches the photodetecting section in the photodetector, thereby detecting the information stored in the optical disk at the photodetecting section.

Claim 13

Dependent Claim 143 words

An optical head device for reading information stored in a recording medium according to Claim 8 wherein said diffraction element is designed such that a light beam emitted from the light source reaching the first diffraction grating of the diffraction element is divided into a 0th order diffracted beam and ± first order diffracted beams utilized for detecting tracking errors and irradiated on the optical disk, and the reflected beam from the optical disk reaches the second diffraction grating of the diffraction element and is divided into a 0th order diffracted beam and first order diffracted beams thereat, and then one of said first order diffracted beams reaches the photodetecting section in the photodetector, thereby causing a tracking servo-mechanism to move a beam spot on a recording track on the optical disk in accordance with the diffracted beam received by said photodetecting section.

Claim 14

Dependent Claim 117 words

An optical head device for reading information stored in a recording medium according to Claim 8 wherein said diffraction element is designed such that a light beam emitted from the light source reaching at the second diffraction grating located at least in the vicinity of one end of the diffraction element, said end being set in a corresponding direction to the radial direction of the optical disk, is divided so as to produce a 0th order diffracted beam whose luminous intensity is decreased thereat, and said 0th order diffracted beam is guided into the optical disk to produce reflected beams most of which reach the first diffraction grating of the diffraction element without diverging to the photodetector.

Claim 15

Dependent Claim 143 words

An optical head device for reading information stored in a recording medium wherein a light beam from a light source is converged on an optical disk and a reflected beam from the optical disk is received by a light receiving element thereby to read out information stored in the optical disk is characterized in a diffraction element for guiding the reflected beam from the optical disk to the light receiving element, positioned between the optical disk and a first diffraction grating disposed at the light source side on the optical path, said diffraction element including a second diffraction grating divided into a plurality of regions by parting lines which extend in a corresponding direction to the radial direction of the optical disk and parting lines which extend in a corresponding direction to the direction of the alignment of pits in the optical disk.

Claim 16

Dependent Claim 143 words

An optical head device for reading information stored in a recording medium wherein a light beam from a light source is converged on an optical disk and a reflected beam from the optical disk is received by a light receiving element thereby to read out information stored in the optical disk is characterized in a diffraction element for guiding the reflected beam from the optical disk to the light receiving element, positioned between the optical disk and a first diffraction grating disposed at the light source side on the optical path, said diffraction element including a second diffraction grating divided into a plurality of regions by parting lines which extend in a corresponding direction to the radial direction of the optical disk and parting lines which extend in a corresponding direction to the direction of the alignment of pits in the optical disk.

Claim 17

Dependent Claim 75 words

An optical head device for reading information stored in a recording medium according to Claim 14 wherein said second diffraction grating formed in the diffraction element is divided into six second diffraction grating regions by a parting line which extends in a corresponding direction to the radial direction of the optical disk and two parting lines which extend in a corresponding direction to the direction of the alignment of the pits in the optical disk.

Claim 18

Dependent Claim 75 words

An optical head device for reading information stored in a recording medium according to Claim 14 wherein said second diffraction grating formed in the diffraction element is divided into nine second diffraction grating regions by two parting lines which extend in a corresponding direction to the radial direction of the optical disk and two parting lines which extend in a corresponding direction to the direction of the alignement of the pits in the optical disk.

Claim 19

Dependent Claim 45 words

An optical head device for reading information stored in a recording medium according to Claim 14 wherein said light receiving element comprises a photodetector including a plurality of photodetecting sections separated from each other corresponding to the plurality of independent regions in the diffraction element.

Claim 20

Dependent Claim 29 words

An optical head device for reading information stored in a recording medium according to Claim 17 wherein said light receiving element comprises a photodetector including five independent photodetecting sections.

Claim 21

Dependent Claim 102 words

An optical head device for reading information stored in a recording medium according to Claim 14 wherein said diffraction element is designed such that the transmission factors of 0th order diffracted beam at the second diffraction grating regions located in the vicinity of both ends of the diffraction element, said ends being set in a corresponding direction to the radial direction of the optical disk, are lower than those at the second diffraction grating regions located in the vicinity of the center of the diffraction element, said center being set in a corresponding direction to the radial direction of the optical disk.

Claim 22

Dependent Claim 125 words

An optical head device for reading information stored in a recording medium according to Claim 19 wherein the depth of the second diffraction grating at the regions located in the vicinity of both ends of the diffraction element, said ends being set in a corresponding direction to the radial direction of the optical disk in order to detect the information stored in the optical disk, is differentiated from the depth of the second diffraction grating at the regions located in the vicinity of the center of the diffraction element, said center being set in a corresponding direction to the radial direction of the optical disk, so that the diffraction element has different transmission factors of 0th order diffracted beam at both ends and the center.

Claim 23

Dependent Claim 242 words

An optical head device for reading information stored in a recording medium according to Claim 19 wherein said diffraction element is designed such that a light beam emitted from the light source is divided into a 0th order diffracted beam and a pair of first order diffracted beams by the first diffraction grating, and some diffracted beams among them pass through the second diffraction grating regions in one part of the diffraction element divided into two parts with a parting line which extends in a corresponding direction to the radial direction of the optical disk, and are irradiated onto the optical disk to produce reflected beams which reach the second diffraction grating regions in the other part of the diffraction element divided with said parting line, and then the 0th order beam among said diffracted beams which have reached at said second diffraction grating regions in the other part of the diffraction element is diffracted thereat to produce a first order diffracted beam to be guided onto a parting line between adjacent photodetecting sections of the photodetector, thereby causing a focus servo-mechanism to move a beam spot on the optical disk in accordance with the surface vibration of the optical disk, while the pair of first diffracted beams which have reached at said second diffraction grating regions in the other side of the diffraction element are diffracted thereat to be guided into two photodetecting sections of the photodetector, thereby detecting tracking errors.

Claim 24

Dependent Claim 188 words

An optical head device for reading information stored in a recording medium according to Claim 19 wherein said diffraction element is designed such that a light beam emitted from the light source passes through second diffraction grating regions in the diffraction element after being divided into a 0th order diffracted beam and a pair of first order diffracted beams by the first diffraction grating, so as to be irradiated and reflected at the optical disk, and said 0th order diffracted beam which has been reflected at the optical disk, returns to different second diffraction grating regions and is further divided thereat into a 0th oder diffracted beam and first order diffracted beams one of which reaches the photodetecting section in the photodetector whereby the detection of information stored in the optical disk is performed, while said pair of first order diffracted beams which have been reflected at the optical disk, return said different second diffraction grating regions and are diffracted thereat so as to be guided into two photodetecting sections, thereby causing a tracking servo-mechanism to move a beam spot on a recording track on the optical disk.

Claim 25

Dependent Claim 149 words

An optical head device for reading information stored in a recording medium wherein a light beam from a light source is converged on the optical disk and a reflected beam from the optical disk is received by a light receiving element thereby to read out information stored in the optical disk is characterized in comprising a diffraction element positioned between the light source and the optical disk on the optical path, said diffraction element including: a first diffraction grating for dividing the light beam from the light source into a 0th order diffracted beam utilized for reading out the information stored in the optical disk and a pair of first order diffracted beams utilized for reading tracking errors, at the light source side thereof; and a second diffraction grating for guiding the reflected beam from the optical disk to the light receiving element, at the optical disk side thereof.

Claim 26

Dependent Claim 149 words

An optical head device for reading information stored in a recording medium wherein a light beam from a light source is converged on the optical disk and a reflected beam from the optical disk is received by a light receiving element thereby to read out information stored in the optical disk is characterized in comprising a diffraction element positioned between the light source and the optical disk on the optical path, said diffraction element including: a first diffraction grating for dividing the light beam from the light source into a 0th order diffracted beam utilized for reading out the information stored in the optical disk and a pair of first order diffracted beams utilized for reading tracking errors, at the light source side thereof; and a second diffraction grating for guiding the reflected beam from the optical disk to the light receiving element, at the optical disk side thereof.

Claim 27

Dependent Claim 30 words

An optical head device for reading information stored in a recording medium according to Claim 23 wherein said second diffraction grating includes a plurality of regions separated from each other.

Claim 28

Dependent Claim 83 words

An optical head device for reading information stored in a recording medium according to Claim 23 wherein the transmission factors of 0th order diffracted beam in the vicinity of both ends of said second diffraction grating, said ends being set in a corresponding direction to the radial direction of the optical disk, are lower than that in the vicinity of the center of the second diffraction grating, said center being set in a corresponding direction to the radial direction of the optical disk.

Claim 29

Dependent Claim 183 words

An optical head device for reading information stored in a track or tracks on a recording medium wherein a light beam from a light source is converged onto the medium and a reflected beam from the medium is received by a light receiving element thereby to read out information stored in the track or tracks, wherein there is provided diffraction means including first diffraction grating portions for dividing the light beam from the light source into a 0th order diffracted beam utilized for reading out the information stored in the track or tracks and a pair of first order diffracted beams utilized for reading tracking errors; and second diffraction grating portions for guiding the reflected beam from the optical disk to the light receiving element, the transmission factors for the 0th order diffracted beam of the first and/or second diffraction grating portions in regions located outermost in the diffraction means in a direction transverse the track or tracks are lower than those of the first and/or second diffraction grating portions in regions located generally centrally of the diffraction means element in said direction.

Claim 30

Dependent Claim 183 words

An optical head device for reading information stored in a track or tracks on a recording medium wherein a light beam from a light source is converged onto the medium and a reflected beam from the medium is received by a light receiving element thereby to read out information stored in the track or tracks, wherein there is provided diffraction means including first diffraction grating portions for dividing the light beam from the light source into a 0th order diffracted beam utilized for reading out the information stored in the track or tracks and a pair of first order diffracted beams utilized for reading tracking errors; and second diffraction grating portions for guiding the reflected beam from the optical disk to the light receiving element, the transmission factors for the 0th order diffracted beam of the first and/or second diffraction grating portions in regions located outermost in the diffraction means in a direction transverse the track or tracks are lower than those of the first and/or second diffraction grating portions in regions located generally centrally of the diffraction means element in said direction.

Claim 31

Dependent Claim 121 words

An optical head for reading information stored in a track or tracks on an optical medium, the head comprising optical means to project light from a light source onto the medium and to direct light from the medium onto a light sensor having an array of sensor regions for the generation of signals from which information, focusing and tracking signals can be derived, wherein the optical means includes diffraction means having an array of diffraction portions and wherein to avoid crosstalk between adjacent track portions the diffraction portions at the periphery of the array in a direction transverse the track or tracks have relatively low transmissivity for 0th order diffracted beam compared to diffraction portions within the array in said direction.

Claim 32

Dependent Claim 121 words

An optical head for reading information stored in a track or tracks on an optical medium, the head comprising optical means to project light from a light source onto the medium and to direct light from the medium onto a light sensor having an array of sensor regions for the generation of signals from which information, focusing and tracking signals can be derived, wherein the optical means includes diffraction means having an array of diffraction portions and wherein to avoid crosstalk between adjacent track portions the diffraction portions at the periphery of the array in a direction transverse the track or tracks have relatively low transmissivity for 0th order diffracted beam compared to diffraction portions within the array in said direction.

Optical head device for reading information stored in a recording medium

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