KR19980036478A - Optical pickup device for multitrack scanning - Google Patents

Abstract

Disclosed is an optical pickup apparatus for scanning multi-tracks, which employs grating so that information can be simultaneously recorded and reproduced for a plurality of tracks on a disc.

The optical pickup apparatus for multi-track scanning includes a light source for generating and outputting light, diffraction optical means for diffracting the light emitted from the light source, and an optical path between the diffraction optical means and the disk to convert the traveling path of the incident light. Optical path changing means, an objective lens disposed on the optical path between the optical path converting means and the disk to focus light incident from the light source side and converging on the recording surface of the disk, and reflected from the disk to the objective lens and optical path And a photodetector for detecting light incident through the converting means, wherein the diffraction optical means diffracts each of the first grating configured to diffract the incident light and the light diffracted in one direction by the first grating in a different direction. Light spots are formed on at least two tracks, including the second grating, and the photodetectors are capable of receiving light reflected from the tracks of the disc, respectively. It is characterized in that a plurality is provided so as to correspond to the number of tracks to be multi-scan.

Description

Optical pickup for multitrack scanning

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup apparatus, and more particularly, to an optical pickup apparatus for scanning multiple tracks, which is capable of simultaneously recording and reproducing information on a plurality of tracks of a disc by employing grating.

In general, the optical pickup device is employed in a compact disc player (CDP), digital video disc player (DVDP), CD-ROM drive, DVD-ROM drive, etc., and the contactless information on the recording surface of the disc that is mounted on the spindle motor and rotates at high speed. Record or play back recorded information.

1 is a view showing an optical arrangement of a conventional optical pickup device. As shown, the optical pickup device includes a light source 10, an objective lens 30, a beam splitter 25, and a photodetector 40.

The objective lens 30 focuses the light incident from the light source 10 to be formed on the recording surface of the disc 1. The beam splitter 25 is positioned on an optical path between the light source 10 and the objective lens 30, and the light incident from the light source 10 is reflected toward the objective lens 30, and the objective lens ( Light incident from the side 30 passes straight through to the photodetector 40. The photodetector 40 receives the light reflected from the recording surface of the disk 1 to detect the RF information signal and the error signal. The photodetector 40 is composed of a plurality of dividers to independently receive and detect light.

In addition, the optical pickup device includes a grating 21 and a collimating lens (not shown) between the light source 10 and the disk 1. The grating 21 is a zero-order diffraction light incident light so that the photodetector 40 can detect a track error signal by a three-beam method, Diffraction with primary diffraction light, ... The collimating lens is a lens that converts incident divergent light into parallel light. Further, an astigmatism lens 35 is further provided on the optical path between the beam splitter 25 and the photodetector 40. The astigmatism lens 35 is a semi-cylindrical lens, and when the distance between the objective lens 30 and the disk 1 is in focus, a circular beam is formed on the photodetector 40. If not, the elliptical beam is made to enter the photodetector 40.

Such a conventional optical pickup apparatus performs recording and / or reproduction of information while scanning only one track of tracks in which light emitted from the light source 10 is formed concentrically on the recording surface of the disk 1. Therefore, the performance of the disc player employing the optical pickup device, that is, the information processing speed, is largely dependent on the rotational speed of the spindle motor 5 which rotates the disc 1, thereby limiting the information processing speed.

SUMMARY OF THE INVENTION The present invention has been made to overcome the above-mentioned disadvantages, and provides an optical pickup apparatus for multi-track scanning that can scan at least two tracks simultaneously so as to greatly increase the information processing speed of a disc player. There is a purpose.

1 is a view showing an optical arrangement of a conventional optical pickup device.

2 is a view showing an optical arrangement of an optical pickup apparatus for multi-track scan according to the present invention.

FIG. 3 shows the arrangement of diffractive optical means in FIG. 2 in accordance with an embodiment of the present invention. FIG.

FIG. 4 is a schematic view of the radially diffracted shape of light by the first grating; FIG.

FIG. 5 is a schematic view showing the diffracted light of the first grating diffracted by the second grating; FIG.

FIG. 6 is a view schematically showing the shape in which light is diffracted in the track direction of the disc by the first grating; FIG.

7 is a schematic illustration of the formation of a light spot on a track of a disc.

8 is a view schematically showing an example of a photodetector according to the present invention.

9 schematically illustrates another example of a photodetector in accordance with the present invention.

* Description of the symbols for the main parts of the drawings *

50 ... disk 60 ... light source

70 Diffractive Optics 71 First Grating

72 Second grading 75 Optical path changing means

80 objective lens 90 photodetector

In order to achieve the above object, the multi-track scan optical pickup device of the present invention comprises a light source for generating and emitting light; Diffraction optical means for diffracting the light emitted from the light source; Optical path converting means disposed on an optical path between the diffraction optical means and the disk to convert a traveling path of incident light; An objective lens disposed on an optical path between the optical path converting means and the disk to focus light incident from the light source toward the recording surface of the disk; An optical detector for detecting light reflected from the disk and incident through the objective lens and the optical path converting means, wherein the optical pickup device for diffraction optical means diffracts the incident light. First grating; And second grating for diffracting each of the light diffracted in one direction by the first grating in a different direction, wherein the light spot is formed on at least two tracks, and the photodetector is reflected from the track of the disc. A plurality of tracks may be provided to correspond to the number of tracks to be multi-scanned to receive light.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a diagram illustrating an optical arrangement of an optical pickup apparatus for multi-track scanning according to an exemplary embodiment of the present invention.

As shown, the optical pickup device converts the light source 60 for generating and outputting light, the diffraction optical means 70 for diffracting the light emitted from the light source 60 and dividing the light into several branches, and the traveling path of the incident light. The optical path changing means 75, the objective lens 80 for focusing the incident light to be formed on the recording surface of the disk 50, and reflected from the disk 50, and the objective lens 80 and the optical path conversion. A photodetector 90 for receiving light via the means 75.

As is widely known, the light path converting means 75 may include a beam splitter for transmitting and reflecting incident light at a predetermined light quantity ratio, and a polarizing beam splitter for transmitting or reflecting incident light according to a polarization direction thereof. In addition, a hologram element may be provided to transmit light incident in one direction in a straight line while diffracting and transmit light incident in another direction. The optical path converting means 75 is located on the optical path between the diffraction optical means 70 and the objective lens 80, and reflects the light incident from the light source 60 toward the disk 50. The incident light converts the traveling path of the light toward the photodetector 90.

The objective lens 80 is disposed between the optical path converting means 75 and the disk 50 so as to focus incident light so that an optical spot is formed on the recording surface of the disk 50.

The diffraction optical means 70 includes a first grating for diffracting incident light and a second grating for diffracting each of the light diffracted in one direction by the first grating in a different direction. As shown in FIG. 3, the first and second gratings 71 and 72 preferably have a lattice direction perpendicular to each other.

Diffraction of incident light along the arrangement direction of the first and second grading 71 and 72 will be described with reference to FIGS. 4 to 6.

As shown in FIG. 4, the first grating 71 has the zeroth order and By diffraction in the primary diffraction light 100a, 100b, 100c or the like, the light source is arranged to form at least one light spot in the radial direction of the disk 50. In this case, as shown in FIG. 5, the second grating 72 again shifts the diffracted light 100a, 100b, 100c by the first grating 71 to the 0th order. By diffraction with a primary diffractive light, the respective tracks are arranged to form at least one light spot in the track direction.

In addition, as shown in FIG. 6, the first grating 71 stores the incident light with zero order and By diffraction in the primary diffraction light (100, 110, 120) or the like, at least one light spot can be arranged in the track direction of the disk (50). In this case, the second grading 72 may return the 0th order and the diffracted light 100, 110, 120 by the first grading 71 again. By diffraction with a primary diffractive light, at least one light spot is arranged in each track in the radial direction of the disc 50, and the result is the same as described with reference to FIG.

7 is a schematic view showing a disk 50 in which light spots are formed. The disc 50 comprises a track formed spirally or concentrically from its central root. Each track includes a land 52 in which information is recorded, and a groove 53 formed between each land 52 and the land 52. The light diffracted by the diffraction optical means 70 condenses at different track positions, as shown. The zeroth order diffraction light of the diffraction optical means 70 is formed at the first track position 200a, and the + 1st order diffraction light is formed at the second track position 200b adjacent to one side of the first track position, and -1 order. The diffracted light enters the third track position 200c adjacent to the other side of the first track position.

8 is a schematic view showing an example of the photodetector 90 according to the present invention. As shown, the photodetector 90 includes first, second, and third photodetectors 190a, 190b, 190c, and these photodetectors 90 comprise the first, second, and first The light reflected at the three track positions 200a, 200b and 200c is received. The first photodetector 190a receives the light reflected from the first track position 200a, and a track error signal for correcting the information signal of the first track position 200a and the position of the optical pickup device. The focus error signal is detected. To this end, the first photodetector 190a is formed of four split plates A, B, C, and D that independently photoelectrically convert. As described above, since the detection of the information signal, the focus error signal, and the track error signal from the first photodetector 190a including four partition plates is well known, the detailed description thereof will be omitted. The second and third photodetectors 190b and 190c are each formed as a single divider, and receive the light reflected from the second and third track positions 100b and 100c to receive the second track position. And information signals of the third track positions 100b and 100c. Here, the photodetector 90 is provided in plural numbers corresponding to the number of tracks recorded and reproduced at the same time.

9 is a schematic view showing another example of the photodetector 90 according to the present invention.

As shown, the first photodetector 190a is further provided with two split plates 195a and 195b to detect the track error signal using the three-beam method, the rest of which is the same as described with reference to FIG. 8. Do.

In addition, the optical pickup apparatus for multi-track scanning preferably includes a collimating lens (not shown) for converting the divergent light incident between the light source 60 and the disk 50 into parallel light. In addition, it is preferable to further include an astigmatism lens 85 on the optical path between the optical path converting means 75 and the photodetector 90. This astigmatism lens 85 is a semi-cylindrical lens, and when the distance between the objective lens 80 and the disk 50 is in focus, a circular beam is formed on the photodetector 90. If not, make an elliptical beam.

The optical pickup device provided as described above scans a plurality of tracks which are recorded and reproduced simultaneously in one rotation of the disk 50, for example, by scanning the first, second and third track positions 200a, 200b and 200c. Record and / or reproduce information. Therefore, the information processing speed can be improved without greatly depending on the rotational speed of the spindle motor 55. In this case, the recording and / or reproducing of information may be performed in units of the number of tracks simultaneously scanned so that the light emitted from the light source 60 does not scan the same track in duplicate as the disk 50 rotates.

Therefore, the optical pickup apparatus according to the present invention provided as described above is provided with at least one grating so as to diffract light in the radial direction of the disk, so that light spots are formed on several tracks of the disk at the same time. Since multiple tracks can be scanned simultaneously during rotation, the information processing speed can be significantly increased without increasing the rotation speed of the disc.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the claims.

Claims (3)

A light source for generating and emitting light; Diffraction optical means for diffracting the light emitted from the light source; Optical path converting means disposed on an optical path between the diffraction optical means and the disk to convert a traveling path of incident light; An objective lens disposed on an optical path between the optical path converting means and the disk to focus light incident from the light source toward the recording surface of the disk; In the optical pickup apparatus for multi-track scan comprising a; optical detector for detecting the light reflected from the disk and incident through the objective lens and the optical path conversion means; The diffraction optical means includes: first grating adapted to diffract incident light; A second grating configured to diffract each of the light diffracted in one direction by the first grating in a different direction, such that light spots are formed on at least two tracks, And a plurality of photodetectors corresponding to the number of tracks that are multi-scanned so as to receive the light reflected from the tracks of the disk. 2. The optical pickup apparatus of claim 1, wherein the first and second gratings are arranged so that their lattice directions are perpendicular to each other. The method of claim 1, wherein at least one of the plurality of photodetectors includes at least two partition plates each independently photoelectrically converted to detect a track error signal and a focus error signal of the disk. Optical pickup for track scanning.