KR20010054942A - Optical Pickup Apparatus - Google Patents

Abstract

PURPOSE: An optical pickup device is provided to use one optical pickup for the optical pickup device of accessing different optical disks. CONSTITUTION: First and second LD chips(32a,32b) in a different wavelength light source(32) generate optical beams of wavelengths corresponding to different optical disks. An optical path identifying optical system(46) identifies optical paths of first and second optical beams(1a,1b) generated from the different wavelength light source. The optical beams in parallel state by a collimating lens(34) pass through a beam splitter for being inputted to an object lens(40). The optical beams are concentrated on recording surfaces(22a,22b) of an optical disk(22) according to wavelength and numerical aperture. Then, the optical beams on the recording surfaces are inputted to a sensor lens(42) for being concentrated on an optical detector(44). Herein, by identification of the optical paths of the optical beams, the beams are concentrated on an identified location of the optical detector.

Description

Optical Pickup Apparatus

The present invention relates to an optical pickup apparatus adapted to use one optical detector in an optical pickup apparatus for heterogeneous optical disc access.

In general, optical discs have been commercialized by commercially available compact discs (CDs) and commercially available DVDs (Digital Versatile Discs) with improved recording capacity. As such optical discs become denser, recording marks and track pitches become smaller. In addition, the denser the optical disk, the shorter the distance from the surface of the disk to the information recording surface. In practice, DVD-based optical discs have a distance of 0.6 mm from the surface of the disc to the information recording surface, while CD-based optical discs have a distance of 1.2 mm. Further, the wavelength? Of the light beam, the beam size BS, and the numerical aperture NA of the objective lens for accessing the DVD optical disc and the CD optical disc 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 accessing the CD-based optical disk should have 780 nm and 1.4 μm, respectively, and the numerical aperture of the objective lens ( NA _C ) should 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 apparatus for accessing the DVD-based optical disc should have 635 to 650 nm and 0.9 μm, respectively, and the numerical aperture of the objective lens ( NA _D ) should be maintained at 0.6.

Recently, optical pickup apparatuses capable of accessing all different types of optical discs have been developed. In addition, the optical pickup apparatus for heterogeneous optical disk access includes light sources generating light beams having different wavelengths in one package so as to simplify the configuration of the optical system and reduce the size of the entire optical pickup apparatus. There is a trend.

Referring to FIG. 1, a conventional optical pickup apparatus for accessing a heterogeneous optical disc includes a two-wavelength light source 2 having a first and a second laser diode chip (hereinafter referred to as an “LD chip”) and a two-wavelength. An objective lens 12 for condensing the first and second light beams 1a and 1b generated from the light source 2 onto each of the first recording surface 22a and the second recording surface 22b of the optical disc 22, and A first beam splitter 6, a second beam splitter 8, and a 45 ° reflector 10 are provided between the wavelength light source 2 and the objective lens 12 side by side. Each of the first and second LD chips 2a and 2b embedded in the two-wavelength light source 2 generates light beams having wavelengths corresponding to different types of optical disks. For example, the first LD chip 2a generates a first light beam 1a having a wavelength of 635 to 650 nm corresponding to the DVD-based optical disk, and the second LD chip 2b has a first wavelength of 780 nm corresponding to the CD-based optical disk. 2 light beams 1b are generated. The first and second light beams 1a and 1b in the form of diverging beams generated from the two-wavelength light source 2 are converted into parallel light beams by the collimating lens 4, and then the first and second beam splitters 6 and 8. ) Is incident on the 45 ° reflector 10. The first and second light beams 1a and 1b incident on the 45 ° reflector 10 are reflected toward the objective lens 12. The objective lens 12 condenses the first and second light beams 1a and 1b incident through the 45 ° reflector 10 on the recording surfaces 22a and 22b of the optical disc 22 in the form of spots. Here, the first light beam 1a is focused on the first recording surface 22a, and the second light beam 1b is focused on the second recording surface 22b.

The optical pickup apparatus for accessing a heterogeneous optical disc also includes first and second photodetectors 16 and 20 for converting the light beam reflected from the optical disc 22 into an electrical signal. The first and second light beams 1a, 1b, which are focused on the recording surfaces 22a, 22b of the optical disc 22, are reflected to back the optical path. After the first light beam 1a is reflected by the 45 ° reflector 10, the first light beam 1a is incident toward the first sensor lens 14 by the reflecting surface of the second beam splitter 8. The reflected light beam is focused on the first photodetector 16 by the first sensor lens 14 and converted into an electrical signal. After the second light beam 1b is reflected by the 45 ° reflector 10, the second light beam 1b is incident on the first beam splitter 6 via the second beam splitter 8 and is reflected on the reflective surface of the first beam splitter 6. Incident to the second sensor lens 18. The reflected light beam is focused on the first photodetector 20 by the second sensor lens 18 and converted into an electrical signal.

However, the optical pickup apparatus for accessing the heterogeneous optical disk shown in FIG. 1 requires photodetectors 16 and 20 for converting each of the reflected light beams having different wavelengths into electrical signals and reflecting paths of the light beams according to the wavelengths of the reflected light beams. Since the beam splitters 6 and 8 are required to separate the optical components, the number of optical components increases and the structure thereof is complicated. To this end, by using the photodetector module 24 composed of a single package as shown in FIG. In this case, the photodetector module 24 is formed on the substrate so that the photodiode chips (hereinafter referred to as "PD chips") 24a and 24b divided into four or two parts as shown in FIG. As described above, in the photodetector module 24 configured as one package, reflected light beams having different wavelengths must be focused on the respective PD chips 24a and 24b. Accordingly, when the PD chip 24a or 24b is aligned with respect to any one of the reflected light beams, the PD chip alignment with respect to the other reflected light beams is very difficult. Furthermore, even after the alignment, the optical components constituting the optical system, particularly the PD chips 24a and 24b, are changed in position due to an external environment (temperature, vibration, etc.), thereby reducing optical reliability.

Accordingly, it is an object of the present invention to provide an optical pickup apparatus which is adapted to use one optical detector in an optical pickup apparatus for heterogeneous optical disc access.

1 is a view showing a conventional optical pickup apparatus for accessing a heterogeneous optical disk.

2 is a view showing another conventional optical pickup apparatus for heterogeneous optical disk access.

3 is a plan view illustrating the photodetector module illustrated in FIG. 2.

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

FIG. 5 is a plan view showing the photodetector shown in FIG. 4; FIG.

FIG. 6 is a diagram showing a first embodiment of the optical path matching optical system shown in FIG. 4; FIG.

FIG. 7 shows a second embodiment of the optical path matching optical system shown in FIG. 4; FIG.

FIG. 8 shows a third embodiment of the optical path matching optical system shown in FIG. 4; FIG.

FIG. 9 shows a fourth embodiment of the optical path matching optical system shown in FIG. 4; FIG.

FIG. 10 is a diagram showing a fifth embodiment of the optical path matching optical system shown in FIG. 4; FIG.

FIG. 11 shows a sixth embodiment of the optical path matching optical system shown in FIG. 4; FIG.

FIG. 12 shows a seventh embodiment of the optical path matching optical system shown in FIG. 4; FIG.

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

<Brief description of symbols for the main parts of the drawings>

1a, 1b: light beam 2,32: two-wavelength light source

2a, 2b, 32a, 32b: LD chip 4, 34: collimation lens

6,8,36: Beam splitter 10,38: 45 ° reflector

12,40: objective lens 14,18,42: sensor lens

16,20,44: photodetector 22: optical disk

22a, 22b: recording surface of optical disk 24: optical detection module

48: flat plate or wedge plate 50: triangular prism

52: bi-dispersion lens 54: grating plate

58, 60, 62: convex lens 64: concave lens

66: birefringence plate 70: oblate plate

In order to achieve the above object, the optical pickup according to the present invention includes a light source generator for generating light beams having different wavelengths, and light path adjusting means for matching the light paths of the light beams.

Other objects and advantages of the present invention in addition to the above object will become apparent from the description of the preferred embodiment of the present invention with reference to the accompanying drawings.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to FIGS. 4 to 13.

Referring to FIG. 4, the two-wavelength light source 32 in which the first and second LD chips 32a and 32b are embedded and the first and second light beams 1a and 1b generated from the two-wavelength light source 32 are An optical path matching optical system disposed side by side between an objective lens 40 for condensing on each of the first recording surface 32a and the second recording surface 32b of the optical disk 32 and the two-wavelength light source 32 and the objective lens 40 (46), collimating lens (34), beam splitter (36) and 45 [deg.] Reflector (10), and a photodetector (44) for converting the light beam reflected from the optical disc (32) into an electrical signal. The optical pickup apparatus for accessing heterogeneous optical disks is shown. Each of the first and second LD chips 32a and 32b embedded in the two-wavelength light source 32 generates light beams having wavelengths corresponding to different types of optical disks. For example, the first LD chip 32a generates the first light beam 1a having a wavelength of 635 to 650 nm corresponding to the DVD-based optical disk, and the second LD chip 32b has a first wavelength of 780 nm corresponding to the CD-based optical disk. 2 light beams 1b are generated. The optical path matching optical system 46 coincides the optical paths of the first and second light beams 1a and 1b generated from the two wavelength light source 32. The detailed configuration of the optical path matching optical system 46 will be described later. The collimating lens 34 converts a light beam in the form of a diverging beam incident from the optical path matching optical system 46 into a parallel light beam. The light beam converted by the collimation lens 34 into the parallel light beam passes through the beam splitter 36 and is reflected by the 45 ° reflector 38 to be incident on the objective lens 40. The light beam incident on the objective lens 40 is condensed in the form of spots on different recording surfaces 22a and 22b of the optical disc 22 according to the wavelength and the numerical aperture. The light beams focused on the recording surfaces 22a and 22b of the optical disk 22 enter the sensor lens 42 via the 45 ° reflector 40 and the reflecting surface of the beam splitter 36 in the direction of the optical path. The reflected light beam incident on the sensor lens 42 is focused on the photodetector 44. The photodetector 44 is composed of a single PD chip 44a divided into four as shown in FIG. 5 to convert the reflected light beam into an electrical signal.

As such, when the optical paths of the first and second light beams 1a and 1b coincide with each other by the optical path coincidence optical system 46, the reflected light beam may be focused at the same point on the photodetector 44.

The optical path matching optical system 46 includes a flat plate or wedge plate 48 as shown in FIG. 6, a triangular prism 50 as shown in FIG. 7, a bi-dispersion lens 52 as shown in FIG. 8, and a grating plate 54 as shown in FIG. 9. A combination of the convex lenses 58 and 60 as shown in FIG. 10, a combination of the convex lens 62 and the concave lens 64 as shown in FIG. 11, and a birefringent plate 66 as shown in FIG. 12. The optical paths of the fields 1a and 1b are matched.

When the first and second light beams 1a and 1b are incident on the flat plate or wedge plate 48 as shown in FIG. 6, the first light beam 1a is reflected on the first surface 48a of the flat plate or wedge plate 46. The second light beam 1b is refracted from the first surface 48a toward the second surface 48b and then reflected and incident on the collimating lens 34 with the same optical path as the first light beam 1a. Accordingly, the light beams 1a and 1b incident on the flat plate or wedge plate 46 at different light paths travel toward the objective lens 40 at the same light path, and are then reflected by the PD chip of the photodetector 44. 44a) is converted into an electrical signal. When the distance between the light beams 1a and 1b is changed, the light paths of the light beams 1a and 1b may be equally matched by adjusting the angle between the first surface 48a and the second surface 48b. .

When the first and second light beams 1a and 1b having different wavelengths are incident on the first surface 50a of the triangular prism 50, the one point on the second surface 50b as shown in FIG. 7. Coincides with and proceeds toward the collimating lens 34. When the distance between the first and second light beams 1a and 1b is changed, the optical paths of the light beams 1a and 1b are adjusted by adjusting the angle θ formed between the first and second surfaces 50a and 50b. The same can be matched.

8, triangular prisms 52a and 52b having different vertex angles? 1 and? 2 and dispersion coefficients? 1 and? 2 are bonded to each other. The vertex angle θ1 of the first triangular prism 52a is set to be smaller than the vertex angle θ2 of the second triangular prism 52a, and the dispersion coefficient υ1 is smaller than the dispersion angle υ2 of the second triangular prism 52b. It is set large. When the first and second light beams 1a and 1b having different wavelengths are incident on the bi-dispersion lens 52, the first and second light beams 1a and 1b are emitted from the exit surface of the second triangular prism 52b. The light paths coincide.

Triangular surfaces are continuously arranged on the surface of the grating plate 54 as shown in FIG. The first and second light beams 1a and 1b are focused on the inclined surface of the grating plate 54 by the convex lens 52 and then reflected to match the light paths.

The two convex lenses 58 and 60 as shown in FIG. 10 are arranged side by side on the optical axis such that the imaging planes of the first and second light beams 1a and 1b condensed by the first convex lens 58 are set differently. After the second light beam 1b is focused on an image plane between the first convex lens 58 and the second convex lens 60, the second light beam 1b is incident on the second convex lens 58, and the first light beam 1a is The focus is formed on the image forming surface on the second convex lens 60. As such, the first and second light beams 1a and 1b incident on the second convex lens 60 pass through the first and second convex lenses 58 and 60, and the first and second light beams 1a and 1b. The paths of are matched.

As shown in FIG. 11, the convex lens 62 and the concave red 64 are focused on the incident surface of the concave lens 64 by the first and second light beams 1a and 1b condensed by the convex lens 58. Are arranged side by side on the optical axis. The first and second light beams 1a and 1b are focused on the concave lens 64 by the convex lens 62 and then converted into parallel beams by the concave lens 64 so that the optical paths coincide.

In the birefringent plate 46 as shown in FIG. 12, the refractive indices of the e direction and the o direction are different. When the first light beam 1a in the polarization direction, such as the e direction, is incident on the birefringent plate 46, the light is transmitted without being refracted, while the second light beam 1b in the polarization direction, such as the o direction, is refracted. This difference in refractive index makes the optical paths of the first and second light beams 1a and 1b coincide.

13 is a diagram illustrating an optical pickup apparatus according to another exemplary embodiment of the present invention.

Referring to FIG. 13, an optical pickup apparatus according to the present invention includes a two-wavelength light source 32 having first and second LD chips 32a and 32b embedded therein, and first and second sources generated from the two-wavelength light source 32. An objective lens 40 for condensing the two light beams 1a and 1b onto each of the first recording surface 22a and the second recording surface 22b of the optical disc 22, the two-wavelength light source 32 and the objective lens 40 A collimator lens 34, a beam splitter 36, and a 45 ° reflector 10, which are arranged side by side, a photodetector 44 for converting the light beam reflected from the optical disk 22 into an electrical signal, and a photodetector ( An oblate plate 70 is provided for focusing reflected light beams of different wavelengths traveling toward 44. The first and second light beams 1a and 1b generated from the two-wavelength light source 32 are converted into parallel light by the collimating lens 34, and the object is passed through the beam splitter 36 and the 45 ° reflector 38. The lens 40 collects the light on the recording surfaces 22a and 22b of the optical disk 22. The light beams focused on the recording surfaces 22a and 22b of the optical disc 22 are incident toward the sensor lens 42 via the 45 ° reflector 40 and the reflecting surface of the beam splitter 36 in the direction of the optical path. The reflected light beam incident on the sensor lens 42 is focused on the oblate surface 70 of the oblate plate 70. The incident surface of the oblate plate 70, that is, the oblate surface 70, is concave in the same shape as the surface of the rugby ball. The oblate plate 70 is installed to be inclined at a predetermined angle with respect to the optical axis. Reflected light beams having different wavelengths incident on the oblate plate 70 are focused by the oblate surface 70a and are focused on the PD chip 44a of FIG. 5 formed in the photodetector 44. As a result, the oblate plate 70 serves to collect the reflected light beams of different wavelengths on one PD chip 44a. Accordingly, the photodetector 44 is composed of one PD chip 44a by the oblate plate 70.

As described above, the optical pickup device according to the present invention is installed between the two-wavelength light source and the collimation lens to match the optical paths of the light beams having different wavelengths incident from the two-wavelength light source or between the sensor lens and the photodetector. Thus, only one photodetector can be installed in the optical pickup device for heterogeneous optical disc access by an optical path matching optical system that focuses reflected light beams having different wavelengths at the same focus on the photodetector.

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. 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 (10)

A light source generator for generating light beams having different wavelengths on one substrate; And optical path adjusting means for matching the optical paths of the light beams. The method of claim 1, An objective lens for focusing the light beams on an optical disc; A photodetector for converting the reflected light beam reflected from the optical disk into an electrical signal; A beam splitter for guiding the light beams toward an objective lens and guiding the reflected light beams toward the photodetector; A collimating lens for converting the light beam traveling toward the objective lens into parallel light; And a sensor lens for condensing the reflected light beam on the photodetector. The method of claim 2, The optical path adjusting means is installed between the light source generating unit and the collimating lens to match the optical path of the light beams. The method of claim 3, wherein The optical path adjusting means is any one of a flat plate and a wedge plate. The method of claim 3, wherein And the optical path adjusting means is a triangular prism. The method of claim 3, wherein And said optical path adjusting means is a grating element having a sawtooth cross section of the incident surface. The method of claim 3, wherein And the optical path adjusting means is combined with two convex lenses spaced at a predetermined distance on the optical axis. The method of claim 3, wherein And the optical path adjusting means is combined with a convex lens and a concave lens spaced apart by a predetermined distance on the optical axis. The method of claim 2, And the optical path adjusting means is arranged between the sensor lens and the photodetector to match a light beam incident to the photodetector. The method of claim 9, The optical path control means is an optical pickup device, characterized in that the incident surface is formed of an oblate surface.