KR20000055632A - Apparatus of Optical Pick-Up and Driving Method Thereof - Google Patents

Abstract

PURPOSE: An optical pickup device is provided to reduce manufacturing costs and to increase compatibilities, by recording information on a lower disk with an optical beam having a short wavelength after playing back the information with an optical beam having a long wavelength, and by playing back or recording information in an upper disk with the optical beam having the short wavelength. CONSTITUTION: An optical pickup device comprises a long wavelength/low output laser diode, a short wavelength/high output laser diode, a beam combiner/separator, and a numerical aperture controller(60). The long wavelength/low output laser diode plays back information recorded in a lower disk. The short wavelength/high output laser diode records information in the lower disk, and plays back or records information in an upper disk. The beam combiner/separator accords output light of the long wavelength/low output laser diode with output light of the short wavelength/high output laser diode. The numerical aperture controller controls numerical apertures of an optical beam incident to the lower/the upper disks via the beam combiner/separator.

Description

Optical pickup device and driving method thereof {Apparatus of Optical Pick-Up and Driving Method Thereof}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup apparatus for optically accessing an optical disc, and more particularly, to an optical pickup apparatus configured to be compatible with various types of discs and a driving method thereof.

Recently, optical discs have a larger capacity than conventional compact discs (hereinafter referred to as "CD") and rewritable compact discs (hereinafter referred to as "CD-R") due to continuous development efforts to increase recording capacity. Digital Versatile Disks (hereinafter referred to as "DVD") have been developed. A DVD has a higher recording density (i.e. track density) than a CD and a shorter distance from the surface of the disc to the information recording surface. In fact, DVD has a distance of 0.6 mm from the surface of the disc to the information recording surface, while CD and CD-R are 1.2 mm. Accordingly, the wavelength [lambda], the beam size BS and the numerical aperture NA of the objective lens of the optical beam used in the optical pickup device for DVD and the optical pickup device for CD and CD-R are different. In this case, the wavelength of the light beam (λ _C ) and the beam size (BS _C ) used in the CD-R and the CD optical pickup device to reproduce the DVD and CD disc using one optical pickup device It should have 780 nm and 1.4 μm, respectively, and the numerical aperture (NA _C ) of the objective lens should be maintained between 0.35 and 0.45. On the other hand, the wavelength (λ _D ) and beam size (BS _D ) of the light beam used in the optical pickup device for DVD should have 635 to 650 nm and 0.9 μm, respectively, and the numerical aperture (NA _D ) of the objective lens is 0.6. Should be maintained. With this arrangement, the DVD disc and the CD disc can be applied to play using one optical pickup device, but there are many difficulties in recording and reproducing. Accordingly, there is a demand for a new method of playing / recording various discs using one optical pickup device.

Accordingly, an object of the present invention is to provide an optical pickup apparatus and a driving method thereof configured to be compatible with various types of disks.

1 is a view showing an optical pickup device according to an embodiment of the present invention.

Figure 2 is a view showing for explaining the coating properties of the PBS of FIG.

3 is a view for explaining the coating characteristics of the DPBS of FIG.

4 is a view illustrating the coating characteristics of the BS of FIG.

5 is a view showing an optical pickup apparatus according to another embodiment of the present invention.

6 is a view for explaining the coating characteristics of the DBS of FIG.

7 is a view for explaining the coating characteristics of the DPBS of FIG.

8 is a view showing the structure of the polarization control means of FIG.

9 is a view showing the structure of the numerical aperture adjusting means of FIG.

Fig. 10 is a diagram for explaining a recording / reproducing operation of the optical pickup apparatus.

FIG. 11 is a diagram showing the shape of a beam spot focused on an optical disc. FIG.

12 is a diagram for explaining the progress of light beams of parallel beams and diverging beams.

<Description of the code | symbol about the principal part of drawing>

2,42: first light source 4,44: second light source

6,12,36,46,52: collimating lens 8,48: beam orthoprism

10: beam splitter 14,54: polarizing beam splitter

16,62: lambda / 4 plate 18: dichroic polarizing beam splitter

20: Reflective mirror 22,64: Objective lens for DVD

24: CD objective lens 26,66: disc

28,32,68: sensor lens 30,34,40,70,74: photodetector

38,72 condenser lens 56 polarization control means

60: numerical aperture adjusting means 50,58: dichroic beam splitter

In order to achieve the above object, an optical pickup apparatus according to the present invention includes a long wavelength / low power laser diode for reproducing information recorded on a lower disk, and a short disk for reproducing and recording information on an upper disk, as well as recording information on a lower disk. A wavelength / high power laser diode, beam combining / separating means for matching the emission light of the long wavelength / low power laser diode and the short wavelength / high power laser diode, and a light beam incident on the disks through the beam combining / separating means And a numerical aperture adjusting means for regulating the numerical aperture.

In addition, the driving method of the optical pickup apparatus according to the present invention is a light beam having a long wavelength, and after recording the information recorded on the lower disk and the information recorded on the lower disk as a light beam having a short wavelength, a light beam having a short wavelength Information is played back / recorded on the parent disk.

Other objects and features of the present invention other than the above object will become apparent from the description of the embodiments with reference to the accompanying drawings.

A preferred embodiment of the present invention will be described with reference to FIGS. 1 to 12.

1, an optical pickup apparatus according to an embodiment of the present invention is shown. As shown in FIG. 1, the optical pickup apparatus according to the present invention records and plays back CD and DVD-based discs using high power and light having a short wavelength (e.g., 635 to 660 nm). In this case, it is possible to overcome the light absorption characteristic according to the wavelength by servoing with light having low power and long wavelength (770-830 nm). This will be described in detail. The light beam dispersed in the high power / short wavelength laser 4 is advanced in the form of a parallel beam by the first collimating lens 6. Parallel beams are shaped from elliptical to circular by beam shape prisms (8). In addition, the P wave component included in the light shaped by the polarizing beam splitter 14 (hereinafter referred to as "PBS") having the characteristics as shown in FIG. 2 is transmitted and the S wave component is reflected. The P wave transmitted through the PBS 14 is changed into circularly polarized light by the λ / 4 plate 16. In addition, a dichroic polarizing beam splitter (hereinafter referred to as "DPBS") having characteristics as shown in FIG. 3 transmits P and S waves having short wavelengths while having long wavelengths. Both P and S waves reflect. The P wave passing through the λ / 4 plate 16 passes through the DPBS 18 and proceeds to the reflection mirror 20. The reflecting mirror 20 reflects the optical path vertically and directs the light beam toward the objective lens 22 for DVD. The objective lens 22 for DVD focuses a light beam at an arbitrary point on the disk 26. In this case, the objective lens is selected according to the type of light beam. On the other hand, the light beam focused on the disk 26 is reflected. At this time, the circularly polarized light is converted into S-waves by the λ / 4 plate 16, and proceeds to the PBS 14 side. The reflected light beam is reflected by the PBS 14 to travel toward the second collimation lens 36. The reflected light beam is focused onto a first photo detector (hereinafter referred to as "PD") by a first sensor lens (hereinafter referred to as "SL"). In this case, the reflected light beam is used for signal reproduction and servo control of the optical disc. On the other hand, a circularly shaped beam in the BSP 8 is incident on the PBS 14 as a P wave, transmitted 90-85% and reflected 10-15% to the second PD 40 by the condenser lens 38. Condensed The signal from the second PD 40 is used for light output control of the LD 4 having a short wavelength.

Further, the diverging beam emitted from the long wavelength (e.g., 770-830 nm) / low power LD 2 is referred to as a beam splitter (" BS " below 10) having the characteristics as shown in FIG. ), 40-60% is transmitted and 60-40% is reflected when the P wave is incident. The light beam transmitted through the BS 10 becomes a parallel beam through the third collimation lens 12 to travel toward the DPBS 18. The light beam transmitted through the DPBS 18 is reflected in the vertical direction by the reflection mirror 20 to proceed to the objective lens 24 for the CD. By the objective lens 24 for CD, the light beam is focused on any one point on the CD. The light beam reflected from the CD exits the incident path. At this time, the reflected light beam is reflected by the BS 10 via the DPBS 18 and the third collimation lens 12 and travels toward the second sensor lens 28. The reflected light beam is focused on the third PD 30 by the sensor lens 28. Accordingly, the long wavelength / low output LD 2 and the CD objective lens 24 are used for CD-R reproduction. In addition, when recording CD-R and CD-RW, a long wavelength / low output LD 2 for servo, a short wavelength high output LD 4 for recording power, and an objective lens 24 for CD are used. On the other hand, the high output / short wavelength LD 4 and the objective lens 22 for DVD are used when recording / reproducing DVD. In this case, the position of the CD objective lens 24 and the DVD objective lens 22 is adjusted by the objective lens adjusting unit 23 so as to correspond to the long wavelength or the short wavelength.

Although the optical pickup apparatus according to an embodiment of the present invention has been described with respect to the optical pickup apparatus for recording / reproducing CD and DVD discs, this relationship may be applied to DVD and HD-DVD. For example, in the case of DVD-R playback, long wavelength / low output LD and an objective for DVD are used. In addition, when recording DVD-R and DVD-RW, long wavelength / low output LD for servo, short wavelength high output LD for recording power, and objective lens for HD-DVD are used. On the other hand, high-power / short wavelength LD and objective lens for HD-DVD are used for recording / playback of HD-DVD. In this case, the LD for DVD generates light beams having a wavelength of 650 nm at low output, and the LD for HD-DVD generates light beams having a wavelength of 410 nm at high output. This relationship could also be applied to CDs and HD-DVDs. For example, in the case of CD-R reproduction, long wavelength / low output LD and objective lens for CD are used. In addition, CD-R and CD-RW recording use long wavelength / low output LD for servo, short wavelength high output LD for recording power, and objective lens for HD-DVD. On the other hand, high-power / short wavelength LD and objective lens for HD-DVD are used for recording / playback of HD-DVD. In this case, the LD for CD generates a light beam having a wavelength of 780 nm at low output, and the LD for HD-DVD generates a light beam having a wavelength of 410 nm at high output. As described above, the optical pickup apparatus according to the present invention can perform recording / reproducing of various discs using one optical pickup.

5, there is shown an optical pickup apparatus according to another embodiment of the present invention.

An optical pickup apparatus according to another embodiment of the present invention records / reproduces a CD and a DVD disc by using one objective lens for a DVD and light sources generating light beams having different wavelengths. This will be described in detail. The light beam emitted from the long wavelength / low output LD 2 travels to the first collimating lens 52 via the first dichroic beam splitter 32 (hereinafter referred to as “DBS”). At this time, the coating characteristics of the first DBS 32 is to transmit the P wave of the long wavelength / short wavelength and reflect the S wave as shown in (a) of FIG. The long wavelength P wave becomes a parallel beam (or divergent beam / converging beam) by the first collimating lens 52, passes through the DPBS 54, and then proceeds toward the polarization control means 56. At this time, the incident light beam passes through without being polarized in the state where the driving voltage is applied. The light beam passing through the polarization control means 56 is reflected in the vertical direction by the second DBS 58 and proceeds to the opening adjustment means 60. The polarization control means 56 and the aperture control means 60 will be described in detail. As shown in FIG. 8, the polarization control means 56 is coated with the electrodes 55 and 55 ′ on the glass substrates 51 and 51 ′, and the liquid crystal layer 53 is disposed between the electrodes 55 and 55 ′. ) Will have a structure arranged. In this case, since the polarization state of the incident beam is not changed when the power is applied (i.e., turned on), the polarization state of the incident beam is changed by 180 ° when the power is turned off (i.e., turned off). As wave, S wave is converted into P wave. That is, the polarization control means 56 adjusts the polarization state of the incident beam depending on whether the power is applied.

In addition, the opening adjustment means 60 is composed of a polarizer 63 and a Color Separated Filter (hereinafter referred to as " CSF ") as shown in FIG. The non-polarization area | region which has a non-polarization characteristic is provided in the center circular part of the polarizing part 63, and the polarization area | region which has a polarization characteristic is provided in the edge. As a result, the specific polarized beam is absorbed in the polarization region provided at the edge of the polarizer 63 so that the beam passing through the polarizer 63 disappears. In addition, the central circular portion of the CSF 61 is provided with a phase correction region for passing both short and long wavelength light beams and minimizing a phase difference with the peripheral portion. The light beam with the long wavelength passing through it is reflected. At this time, the long wavelength / low output light beam passes through the central portion of the aperture adjusting means 60 to the λ / 4 plate 62. The light beam converted into circularly polarized light by the λ / 4 plate 62 is focused at an arbitrary point on the disk 66 via the objective lens 64 for DVD. In addition, the light beam reflected from the optical disk is focused on the first PD 70 via the reverse incident path.

On the other hand, the beam radiated from the short wavelength / high output LD 4 becomes a parallel beam by the second collimating lens 46 and is then shaped into an elliptical shape to a circular shape by the BSP 48. The circularly shaped light beam passes through the DPBS 54 and has the same optical path as the long wavelength beam. In addition, the light beam having a short wavelength is reflected in the vertical direction by the second DBS 58 after passing through the polarization adjusting means 56. Since the light beam passing through the second DBS 58 passes through the polarization portion 63 and the edge region of the CSF 61 of the aperture adjustment means 60, the light beam has a large numerical aperture. The light beam having a large numerical aperture is focused on the disc by the objective lens 64 after passing through the λ / 4 plate 62 to enable recording / reproducing. In addition, the light beam reflected by the disk 66 is reflected by the second DBS 58 via the reverse incidence path. The light beam reflected by the second DBS 58 is focused on the second PD 74 via the condenser lens 72. In this case, the light output of the short wavelength / high output LD 44 is controlled in response to the amount of reflected light focused on the second PD 74.

On the other hand, with reference to Figure 10 will be described the operation principle according to the playback / recording of each disc. As shown in (a) of FIG. 10, the operation during DVD recording / reproducing is performed by the short wavelength beam transmitted through the S-wave from the DPBS 54 entering the polarization control means 56 in which the driving voltage is applied and not polarized. Will pass. The non-polarized light beam is converted into a circularly polarized beam by the λ / 4 plate 62 via the aperture adjusting means 60 and then focused at a point on the disc 66 by the objective lens 64. The beam reflected by the DVD disk 66a is converted into S-waves by the λ / 4 plate 62 again, and then proceeds to the reverse incident path. The light is reflected by the DBS 58 and travels toward the condenser lens 72. The reflected light beam is focused on the second PD 74 by the condenser lens 72 to control the amount of light of the short wavelength / high output LD 44. At this time, since all openings are not affected, the beam spot size required by the DVD disc 66a can be obtained.

On the other hand, the CD-R / RW proxy operation is operated as shown in FIG. This will be described in detail. In the light beam reflected by the DPBS 54, the P wave is changed to the S wave by the polarization control means 56 in which the driving voltage is cut off. In addition, the polarized light beam is passed through the opening is limited by the polarizing plate 63 of the opening adjusting means (60). The light beam of which the numerical aperture is limited is converted into circularly polarized light by the λ / 4 plate 62 and then focused at one point on the CD disc 66b by the objective lens 64. At this time, the beam spot size preferably has a size and light output suitable for recording. The beam reflected by the CD disk 66b is converted into P wave by the λ / 4 plate 62. The reflected light beam passes through the second DBS 58 and the DPBS 54 and is reflected by the first DBS 32 to travel toward the sensor lens 68. The light beam via the sensor lens 68 is incident toward the first PD 70. In this case, a long wavelength / low output beam is used as the servo beam, and its operation principle is as described below. The long wavelength beam is incident on the polarization control means 56 in the voltage-off state with the P wave, and is converted into the S wave. Subsequently, the light beam converted into S-waves is converted into circularly polarized light by the λ / 4 plate 62 after the numerical aperture is limited by the color separation filter 61 of the aperture adjusting means 60. The light beam converted into circularly polarized light is focused on the CD disk 66b by the objective lens 64. At this time, it is preferable that the size of the beam spot is adjusted to have an appropriate size to servo. In addition, the light beam reflected by the CD disk 66b is converted into P waves by the λ / 4 plate 62. The P wave is converted back into the S wave by the polarization control means 56. The light beam converted into the S wave is reflected toward the sensor lens 68 by the DBS 32 via the DPBS 54. The light beam via the sensor lens 68 is focused on the PD 70. At this time, two beams of short wavelength and long wavelength should be adjusted to coincide on the optical disk as shown in FIG. Referring to FIG. 11 in detail, the light spot of the light beam having a short wavelength is shown as 1 'and the light spot of the light beam having the long wavelength is shown as 3'. In this case, it is desirable to align the centers of the 1 'and 3' light spots so that they can be accurately recorded after playing the information on the disc. It is also desirable to align the light spots to move along the center of the track.

On the other hand, the CD sequence playback operation is performed as shown in Fig. 10C. This will be described in detail. The short wavelength beam transmitted from the DPBS 54 through the S wave is incident on the polarization control means 56 in which the driving voltage is applied and passes without polarization. The non-polarized light beam is converted into a circularly polarized beam by the λ / 4 plate 62 via the aperture adjusting means 60, and then focused at a point on the CD disc 66b by the objective lens 64. In this regard, the short wavelength beam is incident on the polarization control means 56 in the voltage-off state with the P wave, and is converted into the S wave. Subsequently, the light beam converted into S-waves is converted into circularly polarized light by the λ / 4 plate 62 after the numerical aperture is limited by the color separation filter 61 of the aperture adjusting means 60. The light beam converted into circularly polarized light is focused at one point on the CD disk 66b by the objective lens 64. The beam reflected from the CD disk 66b is converted into S-waves by the λ / 4 plate 62 again, and then proceeds to the reverse incident path. The light is reflected from the first DBS 50 via the second DBS 58 and the DPBS 54 and travels toward the sensor lens 68. The light beam via the sensor lens 68 is focused on the first PD 70. Accordingly, by applying the principle of Fig. 10 to reduce the spherical aberration by adjusting the opening incident on the objective lens and at the same time to obtain the desired beam size of the optical pickup device that can be operated by using a finite optical system for both CD and DVD discs Implementation is possible. In addition, the DVD system of the infinite optical system as shown in Fig. 12A can be realized by using the same objective lens as the CD system of the finite optical system as shown in (b). Although the optical pickup apparatus according to another embodiment of the present invention has been described with respect to the optical pickup apparatus for recording / reproducing CD and DVD discs, this relationship can be applied to DVD and HD-DVD or CD and HD-DVD.

As described above, the optical pickup apparatus according to the present invention reduces manufacturing costs by recording / reproducing CD-R / RW discs by using a light source having a long wavelength of low power and a light source having a short wavelength of high power. Also, it can be applied to high-density optical pickup compatible with blue laser to improve compatibility.

As described above, the optical pickup apparatus according to the present invention has an advantage of reducing manufacturing costs and increasing compatibility.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. For example, in the detailed description of the present invention, an optical pickup apparatus for recording / reproducing CDs and DVD discs has been described. However, it will be understood by those skilled in the art that this relationship can be applied to DVD and HD-DVD or CD and HD-DVD. . Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (8)

A long wavelength / low power laser diode which reproduces the information recorded on the lower disk, A short wavelength / high power laser diode for recording information on the lower disk and reproducing and recording the information on the upper disk; Beam combining / separating means for matching the emitted light of the long wavelength / low power laser diode and the short wavelength / high power laser diode; And numerical aperture adjusting means for adjusting the numerical aperture of the light beams incident on the disks via the beam combining / separating means. The method of claim 1, The numerical aperture adjusting means, A first objective lens configured to correspond to the numerical aperture of the light beam having the long wavelength; A second objective lens configured to correspond to the numerical aperture of the light beam having the short wavelength; And an objective lens adjusting unit for adjusting positions of the first and second objective lenses so as to correspond to the long wavelength and the short wavelength. The method of claim 1, The numerical aperture adjusting means, A polarizing plate for absorbing a light beam having a specific polarization characteristic, An optical pickup apparatus, comprising a color separation filter for transmitting a light beam having a specific wavelength. The method of claim 1, And the beam combining / separating means comprises polarization converting means for adjusting the polarization state of the incident beam. After the information recorded on the lower disk is reproduced by the light beam having a long wavelength, the information is recorded on the lower disk by the light beam having a short wavelength, and the information is reproduced / recorded on the upper disk by the light beam having a short wavelength. A method of driving an optical pickup device. The method of claim 5, And when the wavelength of the light beam having the long wavelength is 770 to 830 nm, the wavelength of the light beam having the short wavelength is 635 to 660 nm. The method of claim 5, And when the wavelength of the light beam having the long wavelength is 635 to 660 nm, the wavelength of the light beam having the short wavelength is 390 to 430 nm. The method of claim 5, And when the wavelength of the light beam having the long wavelength is 770 to 830 nm, the wavelength of the light beam having the short wavelength is 390 to 430 nm.