KR19980050654A - Optical pickup device for different optical discs - Google Patents

Abstract

The present invention relates to an optical pickup apparatus for heterogeneous optical discs, which accesses optical discs having different distances from the surface and the information recording surface.

An optical pickup apparatus for heterogeneous optical discs includes a first light source for generating a first light beam of a first wavelength, a second light source arranged to form a constant angle with the first light source, and generating a second light beam of a second wavelength; An objective lens for focusing the light beam from the second light source onto the information recording surface of the optical disc, a polarization diffraction grating for guiding the light beams generated by the first and second light sources toward the objective lens, and a polarization diffraction deflector from the polarization diffraction deflector to the optical disc Beam size adjusting means for adjusting the size of the light beam according to the wavelength of the light beam to be incident.

As a result, the optical pickup device for heterogeneous optical discs accurately accesses optical discs of different types by adjusting the wavelength and size of the light beam according to the type of disc.

Description

Optical pickup device for different optical discs

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 schematically shows the structure of an optical pickup apparatus for heterogeneous optical disks according to an embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

10 optical disc 12 support plate

14,16 first and second light source 18 polarized diffraction grating

20: objective lens 22: photodetector

24: beam splitter 26: λ / 4 plate

28: polarizing plate 30: collimating lens

32: sensor lens

The present invention relates to an optical pickup apparatus for optically accessing an optical disc, and more particularly, to an optical pickup apparatus for heterogeneous optical discs having two light sources for generating optical beams having different wavelengths.

In recent years, optical discs have a higher recording capacity than conventional compact discs (hereinafter referred to as CD's) and rewritable compact discs (hereinafter referred to as CD-Rs) due to continuous development efforts to increase recording capacity. 갗 Digital Versatile Disk (hereinafter referred to as `` DVD '') was 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.

As a result, the wavelength [lambda], the beam size BS and the numerical aperture NA of the objective lens of the optical beam used in the DVD optical pickup device and the CD and CD-R optical pickup device are different. For example, the wavelength λc and the beam size BSc of the light beam used in the CD-R and the optical pickup device for the CD should have 780 nm and 1.4 μm, respectively, and the numerical aperture NAc of the objective lens is 0.35 to 0.45 should be maintained. 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.

In order to access both CD-R / CD and DVD, the optical pickup device has two light sources for generating light beams of different wavelengths, as well as the propagation path of the light beams generated by the two light sources and incident on the objective lens. You must be in my position. However, this tolerance is very small, such as 100 μm, and it is very difficult to keep the distance between the propagation paths of the light beams generated from the two light sources due to the structural problem of the light source. For this reason, the optical pickup apparatus could not access all optical disks having different distances from the surface and the information recording surface by using two light sources.

Accordingly, it is an object of the present invention to provide an optical pickup apparatus for heterogeneous optical discs that can access all optical discs of different types by matching paths of light beams generated by two light sources.

In order to achieve the above object, the optical pickup device for a heterogeneous optical disk according to the present invention is arranged so that the first light source for generating the first light beam of the first wavelength and the second light beam of the second wavelength are arranged at an angle with the first light source. Integrates a second light source for generating a light source, an objective lens for focusing the light beams from the first and second light sources on the information recording surface of the optical disk, and a path of the light beams generated at the first and second light sources, and guides them toward the objective lens. And a beam size adjusting means for adjusting the size of the light beam in accordance with the wavelength of the light beam to be incident from the beam integration means toward the optical disk.

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

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

Referring to FIG. 1, first and second light sources 14 and 16 installed side by side and up and down on a support tube 12 to generate a light beam to be irradiated to the optical disc 10, and first and second light sources ( An optical pick-up apparatus for a heterogeneous optical disc according to an embodiment of the present invention is shown having a polarization diffraction grating 18 arranged on the traveling direction of the light beam from 14 and 16. The first light source 14 generates a first home light beam (that is, TM wave) having a wavelength of 635 to 650 nm and a vertical linear polarization characteristic. The second light source 16 generates a second light beam (ie TE wave) having a wavelength of 780 nm and a horizontal linear polarization characteristic. The second light source 16 is supported by the support plate 12 such that the second light beam crosses the first light beam generated by the first light source 14 at a predetermined angle. In addition, the first and second light sources 14 and 16 are selectively driven according to the type of the optical disc 10. In detail, the first light source 14 is driven when the optical disk 10 is a DVD having a relatively short distance between the surface and the information recording surface of 0.6 mm, while the second light source 16 has a surface where the optical disk 10 is surfaced. It is driven in the case of a relatively long CD or CD-R with a distance of 1.2 mm from the information recording surface. The polarization diffraction grating 18 selectively diffracts the light beams from the first and second light sources 14 and 16 according to the polarization characteristic to thereby advance the path of the second light beam from the second light source 16 to the first light source 14. Coincides with the traveling path of the first light beam. For example, the polarization diffraction grating 18 passes the first linear light beam as it is and the second optical beam having horizontal linear polarization characteristics is diffracted at a constant angle. Conversely, the polarization diffraction grating 18 may rotate the first light beam at a constant angle to match the traveling path of the first light beam with the traveling path of the second light beam. By this polarization diffraction grating 18, the first light beam generated by the first light source 14 and the second light beam generated by the second light source 16 are irradiated to the optical disk 10 along the same traveling path. The first and second light sources 14 and 16 installed side by side on the support plate 12 are packaged together with the polarization diffraction grating 18 in one module. This module keeps the interior vacuum to extend the life of the first and second light sources 14, 16.

The optical pickup device for heterogeneous optical discs includes an objective lens 20 for focusing a light beam to be irradiated on the optical disc, a photo detector 22 for converting the light beam reflected by the optical disc 10 into an electrical signal, and a polarization diffraction grating 18. ) And a beam splitter 24, a λ / 4 tube 26, and a polarizing plate 28 arranged side by side between the objective lens 20 and the objective lens 20. The beam splitter 24 is intact so that the light beam (ie, the first or second light beam) from the polarization diffraction grating 18 travels toward the objective lens 20 via the λ / 4 plate 26 and the polarizing plate 28. Pass it through.

In addition, the beam splitter 24 is reflected by the optical disk 10 to reflect the reflected light beam through the objective lens 20, the polarizing plate 28 and the λ / 4 plate 26 toward the photodetector 22. And the λ / 4 plate 26 changes the polarization characteristics of the light beam traveling from the beam splitter 24 toward the polarizer 28. In detail, the λ / 4 tube 26 is a horizontal linearly polarized light beam (ie, TE wave) when the light beam from the beam splitter 24 is a first light beam that is a vertical linearly polarized light beam (ie, TM wave). Is converted into a second light beam. In addition, the lambda / 4 plate 26 is used when the light beam from the beam splitter 24 is a second light beam having a horizontal linear polarization characteristic (i.e., TE wave). Convert to a third light beam. Then, the polarizing plate 28 selectively blocks a part of the light beam in accordance with the polarization characteristic of the light beam from the λ / 4 plate 26. In other words, when the light beam from the λ / 4 plate 26 is the second light beam having the horizontal linear polarization characteristic, the polarizing plate 28 passes the light beam directly toward the objective lens 20. In contrast, when the light beam from the λ / 4 tube 26 is a third light beam having circular polarization characteristics, the polarizing plate 28 blocks the outer portion of the light beam and travels toward the objective lens 20. (Ie, beam size) is made small. As a result, when the first light beam is generated from the first light source 14, the polarizing plate 28 focuses the light beam on the first information recording surface 10A of the optical disc 10 in a positive shape by the objective lens 20. This allows the DVD to be suppressed accurately. When the second light beam is generated in the second light source 16, the polarizing plate 28 focuses the light beam on the second information recording surface 10B of the optical disc 20 in the form of dots by the objective lens 20. Ensure that CDs and CD-Rs are accessed correctly.

In addition, the optical pickup device for the heterogeneous optical disk includes a collimating lens 30 positioned between the beam splitter 24 and the λ / 4 plate 26, and a sensor lens 32 positioned between the beam splitter 24 and the photodetector 22. ). The collimating lens 30 advances the first or second light beam from the beam splitter 24 toward the objective lens 20 in parallel. The sensor lens 32 condenses the light beam from the beam splitter 24 on the surface of the photodetector 22. As a result, the collimation lens 30 and the sensor lens 32 have a function of improving the sensitivity of the reflected light beam that is degraded as the objective lens 20 moves in the horizontal and vertical directions.

As described above, the optical pickup apparatus for heterogeneous optical disks according to the present invention can match the paths of the light beams generated by the two light sources by the polarization diffraction grating to the objective lens. The optical pickup apparatus for heterogeneous optical disks according to the present invention uses a polarizing plate and a λ / 4 plate to selectively adjust the beam diameters (ie, beam sizes) of light beams having different wavelengths to adjust the numerical aperture of the objective lens. Accordingly, the optical pickup apparatus for heterogeneous optical discs according to the present invention can accurately access both DVD, CD, and CD-R having different distances from the surface and the information recording surface.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit and scope of the present invention. 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 (6)

A first light source for generating a first light beam of a first wavelength, a second light source arranged at an angle with the first light source to generate a second light beam of a second wavelength, and from the first and second light sources An objective lens for focusing the light beam on the information recording surface of the optical disc, beam integration means for integrating the traveling paths of the light beams generated by the first and second light sources and guiding it toward the objective lens, and an optical beam incident from the beam integration means toward the optical disc. And a beam size adjusting means for adjusting the size of the light beam in accordance with the wavelength of the optical disk. The method of claim 1, wherein the first and second light beams have different polarization characteristics, and the beam integrating means diffracts any one of the first and second light beams at a predetermined angle according to the polarization characteristics to advance the light beams. And a polarization diffraction grating for matching a path with a traveling path of another light beam. The optical pickup of claim 2, wherein the first light beam is a vertical linearly polarized light beam, the second light beam is a horizontal linearly polarized light beam, and the polarization diffraction grating diffracts the second light beam at a constant angle. Device. 4. The apparatus of claim 3, wherein the beam size adjusting means comprises: a polarization converter positioned between the polarization diffraction grating and the objective lens to convert a vertical linearly polarized light beam into a horizontal linearly polarized light beam and a horizontal linearly polarized light beam into a circularly polarized light beam; And a polarizing plate for selectively blocking a part of the light beam traveling from the transducer toward the objective lens according to the polarization characteristic of the light beam. The optical beam according to claim 4, wherein the light detection means for converting the light beam reflected by the optical disk into an electrical signal is located between the polarization diffraction grating, the polarization transducer and the light detection means, A beam splitter configured to irradiate the optical disk via the polarizing transducer, the polarizing plate, and the objective lens, and to reflect the reflected light beam from the optical disk via the objective lens, the polarizing plate, and the polarizing transducer toward the light detecting means. Optical pickup device for heterogeneous optical disk, characterized in that it further comprises. 6. The sensor of claim 5, further comprising: a sensor lens positioned between the beam splitter and the light detecting means for condensing a light beam to be incident from the beam splitter toward the light detecting means, and positioned between the beam splitter and the polarization converter. And a collimating lens for allowing the light beam from the splitter to travel in parallel to the polarization transducer.