KR19980050656A - 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 for generating a second light beam of a second wavelength arranged in parallel with the first light source; An objective lens for focusing the light beam from the light source onto the information recording surface of the optical disc, a heterogeneous reflection mirror that integrates the traveling path of the light beams generated by the first and second light sources into the objective lens, and enters the optical disc from the heterogeneous reflection mirror toward 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.

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 is a diagram schematically showing 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 sources 18 double reflecting mirror

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 digital recorder having a larger recording capacity than conventional compact discs (hereinafter referred to as CDs) and rewritable compact discs (hereinafter referred to as CD-Rs) due to continuous development efforts to increase recording capacity. Tiled discs (hereinafter referred to as DVDs) 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.

As a result, the wavelength?, 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 λ _c and the beam size BS _c of the light beam used in the optical pickup apparatus for CD-R and CD should have 780 nm and 1.4 μm, respectively, and the numerical aperture (NA) of the objective lens. _c ) shall be maintained between 0.35 and 0.45. On the other hand, the wavelength (λ _D ) and the 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 (NAD) of the objective lens is 0.6. Must be maintained.

In order to suppress both CD-R / CD and DVD, the optical pickup device has two light sources for generating light beams of different wavelengths, as well as a propagation path of the light beams generated by the two light sources and incident on the objective lens. It must be located within range. However, this allowable beam is very small, such as 100 μm, and it is very difficult to keep the merit between the propagation paths of the light beams generated by 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 in parallel with the first light source and the first light source for generating the first light beam of the first wavelength, to generate a second light beam of the second wavelength A second 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 disc, and a traveling path of the light beams generated at the first and second light sources, and guiding 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.

In addition to the above objects, the objects and advantages of the present invention 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 on a support plate 12 and first and second light sources 14 and 16 to generate light beams to be irradiated to the optical disc 10. An optical pickup window for a heterogeneous optical disc according to an embodiment of the present invention having a heterogeneous reflection mirror 18 disposed obliquely on an upper portion thereof). The first light source 14 generates a first light beam (ie, 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 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 dual reflecting mirror 18 reflects the first light beam from the first light source 14 and the second light beam from the second light source 16 at right angles to propagate the first and second light beams toward the optical disk 10. Match the furnace. To this end, the dual reflection mirror 18 has a total reflection surface 18A formed on the upper surface and a selective reflection surface 18B formed on the bottom surface. The total reflection surface 18A reflects all the light beams regardless of the polarization characteristics of the light beams. On the other hand, the selective reflection surface 18B selectively reflects the light beam according to the polarization characteristic of the light beam. In detail, the selective reflection surface 18B transmits the first light beam of vertical linearly polarized light and reflects the second light beam of horizontal linearly polarized light. Alternatively, selective reflective surface 18B may be formed to transmit a second light beam of horizontal linearly polarized light and reflect a second light beam of vertical linearly polarized light. In addition, the selective reflection surface 18B is formed by alternately applying magnesium fluorite (MgF ₂ ) and zinc sulfide (ZnS) with a dichroic coating film. The first light beam reflected by the total reflection surface 18A of the dual reflection mirror 18 follows the same traveling path as the second light beam reflected by the selective reflection surface 18B of the double reflection mirror 18. Is investigated. In addition, the first and second light sources 14 and 16 installed side by side on the support plate 12 are packaged together as a single module together with the double reflecting mirror 18. This module maintains the interior in a 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 photodetector 22 for converting the light beam reflected by the optical disc 10 into an electrical signal, and a double reflection mirror 18. And a beam splitter 24, a λ / 4 plate 26, and a polarizing plate 28 arranged side by side between the lens and the objective lens 20. The beam splitter 24 is intact so as to travel the light beam from the double reflecting mirror 18 (ie, FIG. 1 or the second light beam) 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 plate 26 is a horizontal linearly polarized light beam (i.e., TE wave) when the light beam from the beam splitter 24 is a first light beam that is a vertical linearly polarized light beam (i.e., TM wave). Is converted into a second light beam. In addition, the λ / 4 plate 26 is a circularly polarized light characteristic (i.e., S-wave) when the light beam from the beam splitter 24 is a second light beam having a horizontal new polarization characteristic (i.e., TE wave). Is converted into 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 plate 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 in the form of a dot on the first information recording surface 10A of the optical disc 10 by the objective lens 20. To ensure that the DVD is accessed correctly. When the second light beam is generated from 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, which decreases as the objective lens 20 moves in the horizontal and vertical directions.

As described above, the optical pickup device for heterogeneous optical disks according to the present invention can match the path of travel of the optical beams having different wavelengths generated by the two light sources by the dual reflection mirror 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 on the beam without departing from the spirit 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 beam of the claims.

Claims (7)

A first light source generating a first light beam of a first wavelength, a second light source arranged side by side with the first light source to generate a second light beam of a second wavelength, and light beams from the first and second light sources An objective lens focused on the information recording surface of the optical disc, beam integration means for integrating and guiding the traveling paths of the light beams generated by the first and second light sources toward the objective lens, and an optical beam to be incident from the beam integration means toward the optical disc. And a beam size adjusting means for adjusting the size of the light beam according to the wavelength. The method of claim 1, wherein the first and second light beams have different polarization characteristics, and the beam integration means selectively reflects the light beams according to the total reflection surface and the polarization characteristics of the light beams irrespective of the polarization characteristics of the light beams. An optical pickup apparatus for heterogeneous optical discs, characterized by comprising a double reflecting mirror having a selective reflecting surface. 3. 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 selective reflecting surface reflects a second light beam of horizontal linearly polarized light. Device. 4. The apparatus of claim 3, wherein the beam size adjusting means comprises: a polarization converter positioned between the dual reflection mirror 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 polarization converter toward the objective lens according to the polarization characteristic of the light beam. The optical beam according to claim 4, further comprising: light detecting means for converting the light beam reflected by the optical disk into an electrical signal, and a light beam from the double reflecting mirror positioned between the double reflecting mirror, the polarization converter and the light detecting 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 lens 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 causing the light beam from the beam splitter to travel in parallel to said polarization transducer. 5. The optical pickup apparatus for heterogeneous optical discs according to claim 4, wherein the credible reflective surface is formed by alternately applying magnesium fluorite (MgF ₂ ) and zinc sulfide (ZnS).