KR20060110541A - Optical source module of double wave and its optical pick-up appratus - Google Patents

Abstract

A two-wavelength optical module and an optical pickup device with the same are provided so that it is necessary to separately compensate the distance difference of two beams by concentrating paths of the two beams emitted from the two-wavelength optical module on one point. The first and the second LD(Laser Diode) chips(31a,31b) are separated at a certain interval in one package. A diffracting element diffracts beams emitted from the first and the second LD chips(31a,31b) to the same target point. The diffracting element(34) has a V shape which has a certain angle according to a distance of the target point on the first and the second LD chips(31a,31b) in the package.

Description

Two-wavelength light source module and an optical pickup device having the same {Optical source module of double wave and its optical pick-up appratus}

1 is a block diagram showing a conventional two-wavelength optical pickup apparatus.

Figure 2 is a block diagram showing a conventional two-wavelength light source module.

3 is a view showing a position adjustment process of a conventional photodetector.

4 is a block diagram showing an optical pickup device having a two-wavelength light source module according to an embodiment of the present invention.

5 is a view showing a beam emission path in a two-wavelength light source module according to the present invention.

Figure 6 is a block diagram showing a two-wavelength light source module according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

31 ... light source module 31a, 31b ... LD chip

31c ... diffractive element 32 ... prism

33 ... half mirror 34 ... collimator lens

35 objective lens 36 disc

38.Photodetector

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a two-wavelength light source module and an optical pickup device having the same, in which the beam path of the two-wavelength laser diode can be adjusted to one beam path.

In general, optical discs have been commercialized by commercially available compact discs (CDs) and commercially available DVDs (Digital Video Discs) with improved recording capacities. As the optical disc becomes denser, the recording mark and track pitch become smaller, and the distance from the surface of the disc to the information recording surface becomes shorter. In practice, the DVD-based optical disc has a distance of 0.6 mm from the surface of the disc to the information recording surface, while the CD-based optical disc has 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-based optical disc and the CD-based optical disc are different. For example, the wavelength [lambda] C and beam size BSC of the light beam used in the optical pickup apparatus for accessing the CD series optical disk are 780 nm and 1.4 µm, respectively, and the numerical aperture NA of the objective lens is 0.35 to 0.45 should be maintained. On the other hand, the wavelength (λD) and the beam size (BSD) 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 (NAD) of the objective lens. Shall be maintained at 0.6.

1 is a block diagram showing a conventional optical pickup device to which two-wavelength LD is applied.

Referring to FIG. 1, a light source module 11 having first and second laser diode chips (hereinafter referred to as LD chips) 11a and 11b for generating different wavelengths and the light source A prism 12 for changing the light path by reflecting or transmitting the light emitted from the module 11, a half mirror 13 for changing the reflected light in the direction of the objective lens, and a collimator for changing the beam in parallel. And a lens 14, an objective lens 15 for focusing the parallel light onto the disk 16, and a photodetector 18 for receiving and detecting light reflected from the disk 16. do.

Here, a beam combiner 17 is formed between the prism 12 and the photo detector 18 to adjust the other beams to be centered in the cell centered on the optical axis adjusted beams.

The optical pickup device using the two-wavelength LD as described above will be described with reference to FIGS. 1 to 3.

As shown in FIG. 1 and FIG. 2, the light source module 11 includes a first LD chip 11a and a second LD chip 11b that generate different wavelengths in one package. The light source 1a of the first LD chip 11a is, for example, a laser diode that emits light having a wavelength of 650 nm, and is used for the relatively thin disk, for example, a DVD. The light source 1b of the second LD chip 11b is, for example, a CD laser diode for irradiating light of 780 nm wavelength, and is used for the relatively thick disk, for example, CD. These first and second LD chips 11a and 11b are arranged to be approximately (100 ± 2) μm apart.

On the optical path between the light source module 11 and the beam splitter 12, gratings for spectroscopically radiating the light emitted from the first and second light sources 1a and 1b into three beams are respectively provided. desirable.

Light generated from the light source module 11 is incident on the prism 12 and reflected in the direction of the objective lens. At this time, the prism 12 is transmitted or reflected according to the polarization direction. The beam reflected through the prism 12 is changed in the optical path in the direction of the objective lens by a half mirror 13, and the objective lens 15 in a parallel beam by a collimator lens 14 Condensed on the disk 16 through?).

Here, a spot is formed on a relatively thin disk in the first light source 1a condensed by the objective lens 15, and a spot is formed on a relatively thick disk in the second light source 1b.

Then, the beam focused on the disk 16 is moved through the objective lens 15, the collimator lens 14, the half mirror 14, the prism 12 and synthesized by the beam combiner 17 and then the photodetector. (18) is detected. The photo detector 18 is composed of three cells 18a, 18b, and 18c having a quadrature structure to detect the specular + 1st, 0th, and -1st reflected light beams, respectively. The photo detector 18 converts the light reflected from the disk into an electrical signal for tracking error detection and focus error detection.

Such an optical pickup device is a compatible optical pickup device and can be used interchangeably with discs of different thicknesses. In other words, one of the CD / DVD discs is a relatively thin DVD disc and the other can be applied to both relatively thick CD discs.

Here, since two light sources are used, all of the light spots formed on the photodetector 23 fall without forming at one point. This is caused by the interval d between two LD chips 11a and 11b.

That is, when the alignment of the cells 18a, 18b, and 18c of the photodetector 18 is based on the first reflected light beam 1a 'as shown in FIG. 3, the second reflected light beam 1b' is directed to either side. It is biased and formed on the photodetector 18. Then, the servo signal and the reproduction signal can be detected only for the optical disc corresponding to the first reflected light beam 1a ', and the servo signal and the reproduction signal for the optical disc corresponding to the second reflected light beam 1b' cannot be detected. do.

This compensates for the difference in the distance between the two beams formed when the disc returns to the photodetector (PD) 18. As shown in FIG. 3, the PD plate 28 is moved (X, Y). The first reflected light beam, i.e., the DVD spot 1a ', is formed on the light detector. As a result, the beam is aligned to the center of the three cells 18a, 18b, and 18c in the center 0th order beam, and the DVD defocus adjustment is performed at this time.

Then, the beam combiner located in front of the photodetector is moved to adjust the second reflected light beam, that is, the CD spot 1b ', to be in the center of the cell.

However, conventionally, a step is generated between the two beams due to the manufacturing method for generating two wavelengths when adjusting the position (X, Y) of the photodetector 18 of the pickup for DVD recording using the two wavelength LD. That is, the optical axes do not coincide with each other because the first and second light sources are approximately (100 ± 2) μm apart from each other in the light source module. Thus, in order to compensate for the difference in the distance between the two beams reflected from the disk and confined to the photodetector 18, the ± first order beam is detected using the beam combiner 17 in front of the photodetector 18. Adjust to center the cell.

Accordingly, since the beam combiner 17 must be provided on the optical path to adjust the two beam spots, there is a problem that the product price is increased due to the increase in the size of the optical pickup device and the increase in the number of parts. .

It is a first object of the present invention to provide a two-wavelength light source module in which a beam emitted from the two-wavelength light source module is concentrated at one point.

The second object of the present invention is to provide an optical pickup device having a two-wavelength light source module which can not compensate the difference in the distance between the two beams by concentrating two beam paths emitted from the two-wavelength light source module at any one point. In providing.

A third object of the present invention is to provide an optical pickup apparatus having a two-wavelength light source module that can focus the beams emitted from two LD chips by using a beam of one LD chip.

Two wavelength light source module according to the present invention for achieving the above object,

First and second LD chips spaced at predetermined intervals in one package;

And a diffraction element diffracting the beams emitted from the first and second LD chips to the same target point.

Preferably, the diffractive element is characterized in that the "V" shape having a predetermined angle according to the distance of the target point on the first and second LD chip.

And, the optical pickup device having a two-wavelength light source module according to an embodiment of the present invention,

A light source module having first and second LD chips spaced at predetermined intervals in one package and including a diffraction element diffracting the first or second light source generated from the first and second LD chips at the same target point; ;

Reflection and transmission means for forming target points of the first and second light sources, and reflecting or transmitting the light source in the objective lens direction or vice versa according to the incident direction;

Optical path switching means for guiding a beam transmitted from the prism toward an objective lens;

An objective lens for irradiating the disk with the incident beam;

And a photodetector for receiving the reflected beam reflected from the disk.

Preferably, the diffractive element is characterized in that the "V" shape having a predetermined angle according to the distance of the target point on the first and second LD chip.

Focus adjustment is performed on the light sources of the first and second LD chips using any one of the first and second light sources.

Hereinafter, with reference to the accompanying drawings as follows.

Figure 4 is a block diagram showing an optical pickup device having a two wavelength light source module of the present invention, Figure 5 is a view showing a beam path of the two wavelength light source module according to the present invention.

4 and 5, the first and second LD chips 31a and 31b and the diffraction element 31c are provided in one package, and the first and second light sources 30a and 30b are disposed at the same target point. A light source module 31 for emitting the light; A prism 32 for reflecting or transmitting the generated light source in the direction of the objective lens or the reverse path thereof; A half mirror 33 for guiding the beam transmitted from the prism 32 toward the objective lens; A collimator lens 34 for changing the beam traveling in the objective lens direction in parallel; An objective lens 35 for condensing a beam on the disk 36; And a photodetector 38 which receives the reflected light beam transmitted from the prism 34 and detects it as an electrical signal.

The light source module 31 is a two-wavelength light source module, in which first and second LD chips 31a and 31b are spaced at predetermined intervals, and have a “V” shape symmetrical to a center thereof on the first and second LD chips. Of the diffraction elements 31c are integrally formed as a package.

Referring to the accompanying drawings, a two-wavelength light source module and an optical pickup device having the same according to an exemplary embodiment of the present invention configured as described above will be described.

First, referring to FIGS. 4 and 5, each of the first and second LD chips 31a and 31b mounted in the two-wavelength light source module 31 generates light sources having wavelengths corresponding to different types of optical disks. The first LD chip 31a generates the first light source 30a having a wavelength of 635 to 650 nm corresponding to the DVD-based optical disk, and the second LD chip 31b generates the second light source 30b having a 780 nm wavelength corresponding to the CD-based optical disk. Will occur. As another example, two of CD, DVD, and BD may be mounted.

In this case, the two-wavelength light source module 31 includes a diffraction element 31c together with the first LD chip and the second LD chip 31a and 31b. The diffractive element 31c is a diffractive reflection mirror, spaced apart from the first and second LD chips by a predetermined distance, and has a structure in which left and right symmetry is performed around the center of the first and second LD chips. For example, it has a "V" shape. Both wing surfaces of the “V” face the first LD chip and the second LD chip, and diffracts the beams emitted from the two LD chips to be collected at one point at the same target point.

The first and second light sources 30a and 30b emitted from the light source module 31 are concentrated at one target point of the prism 32, and thus the beams transmitted or reflected in the prism 32 in accordance with the polarization direction are concentrated. The path is one path.

The beam reflected by the prism 32 is converted by the half mirror 33 to the path of the beam in the direction of the objective lens, and the collimator lens 34 is positioned between the prism 32 and the objective lens 35 to direct the beam. In parallel, the objective lens 35 condenses the incident beam onto the disk 37. Here, light emitted from the first LD chip 31a forms light spots on a relatively thin disk, and light emitted from the second LD chip 31b forms light spots on a relatively thick disk. Here, the lenses disposed in the optical path may be changed to another lens or an optical module, and in particular, the prism may be configured as another lens because the prism is a kind of beam splitter.

In this way, the light spot formed on the disk 37 is reflected and retrogrades to pass through the objective lens 35, the collimator lens 34, the half mirror 33, and the prism 32 to be received by the photodetector 38. That is, the reflected light beams of the two-wavelength light source are respectively detected with the existing combiner removed.

Accordingly, the beam path traveling in the direction of the objective lens and the beam path traveling in the direction of the photodetector are moved in the same line, so that the beam emitted from the specific LD chip 31a or 31b detects the electrical signal by the photodetector 38. In this case, the focus adjustment of the two LD chips 31a and 31b may be performed through one focus adjustment.

6 shows a structure of a two-wavelength light source module 31 according to the present invention. As shown in the figure, the diffraction element 31c having a "V" shape is disposed on the LD chips 31a and 31b in the interior 31d of the cap 31e. The diffractive element 31c is spaced apart from the LD chips 31a and 31b at predetermined intervals, and both wing surfaces are formed at a predetermined angle θ from the center. This angle may be adjusted according to the distance between the LD chips and the distance to the prism.

 So far, the present invention has been described with reference to the preferred embodiments, and those skilled in the art to which the present invention pertains to the detailed description of the present invention and other forms of embodiments within the essential technical scope of the present invention. Could be implemented. Here, the essential technical scope of the present invention is shown in the claims, and all differences within the equivalent range will be construed as being included in the present invention.

As described above, according to the optical pickup device according to the present invention, by diffracting the beam emitted from the light source module having the two-wavelength LD chip to the same target point, the paths of the two beams are aligned into one beam path. It is effective to adjust two wavelengths with one focus adjustment. Accordingly, there is an effect of reducing the time required for focusing and reducing the parts used for two adjustments.

Claims (6)

First and second LD chips spaced at predetermined intervals in one package; And a diffraction element diffracting the beams emitted from the first and second LD chips to the same target point. The method of claim 1, The diffractive element is a two-wavelength light source module, characterized in that the "V" shaped to form a predetermined angle according to the distance of the target point on the first and second LD chip in the package. A light source module having first and second LD chips spaced at predetermined intervals in one package and including a diffraction element diffracting the first or second light source generated from the first and second LD chips at the same target point; ; Reflection and transmission means for forming target points of the first and second light sources, and reflecting or transmitting the light source in the objective lens direction or vice versa according to the incident direction; Optical path switching means for guiding a beam transmitted from the prism toward an objective lens; An objective lens for irradiating the incident beam to the disk; And a photodetector for receiving the reflected beam reflected from the disk. The method of claim 3, wherein The diffraction element is an optical pickup device having a two-wavelength light source module having a "V" shape to form a predetermined angle according to the distance of the target point on the first and second LD chip. The method of claim 3, wherein The diffraction element is an optical pickup device having a two-wavelength light source module, characterized in that having a symmetrical or asymmetrical shape. The method of claim 1, The optical pickup device having a two-wavelength light source module, characterized in that the focus adjustment to the light source of the first and second LD chip using the light source of any one of the first or second light source.

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