KR20050076389A - Optical pickup apparatus - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an optical pick-up apparatus, in particular, which makes it possible to configure an optical system using linear flat light instead of circular flat light.

An optical pickup apparatus according to the present invention comprises: a plurality of laser diodes for generating beams of different wavelengths; A beam splitter for transmitting or reflecting the beam according to the polarization direction; Grating for dividing the light beams generated from the plurality of laser diodes into three beams; A reflection mirror for changing the optical path of the incident beam toward the objective lens; A collimator lens positioned between the laser diode and the objective lens to make the beam a parallel beam; An objective lens for focusing the incident beam on the disk; And a sensor lens for correcting astigmatism of the reflected light beam, and a photo detector for detecting the reflected light beam reflected from the disk as an electrical signal.

Description

Optical pickup apparatus

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an optical pick-up apparatus, in particular, which makes it possible to configure an optical system using linear flat light instead of circular flat light.

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 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, 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 optical disc and the CD optical disc are different. For example, the wavelength (λC) and beam size (BSC) of the light beam used in the optical pickup apparatus for accessing an optical disc of CD series should have 780 nm and 1.4 μm, respectively, and the numerical aperture (NAC) of the objective lens. Should be between 0.35 and 0.45. 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 an optical system of a conventional optical pickup device of different wavelengths.

Referring to FIG. 1, a first light source generated from a first laser diode (CD LD) 101 is converted into circular polarized light through a correction lens (CD lens) 103 and a first quarter wave plate (QWP) 105. And the beam splitter 107 is incident on the beam splitter 107. The correction lens 103 is a lens that compensates for a mechanical position and the like so that a certain distance is maintained with the collimator lens 111 that creates a parallel beam. . The first QWP 105 generates circularly polarized light through the delay between the P wave and the S wave.

Here, the first QWP 105 is manufactured by having the glasses 105a and 105c at the entrance and exit sides and attaching the QWP 105b between the glasses 105a and 105c and nicking the exit side glass 105c. Form grating through.

The beam splitter 107 transmits or reflects an incident beam according to the polarization direction, and the reflected beam is reflected in the direction of the objective lens in the reflection mirror 109 and is converted into a parallel beam by a collimator lens 111. It is made and condensed on the disk 115 through the objective lens 113 at a point.

The first reflected light beam reflected from the disk 115 includes the objective lens 113, the collimator lens 111, the reflection mirror 109, the beam splitter 107, the half mirror 117, and the sensor lens 119. Through the light detector 121, the light is collected and detected as an electrical signal. The detected signal is used to output servo and RF control signals. Here, the sensor lens 119 is not a uniform curvature of the lens surface, but differently configured in the vertical direction and the horizontal direction to generate astigmatism.

Meanwhile, the second light source generated from the second laser diode 102 is incident on the half mirror 117 via the second QWP 118, and the half mirror 117 reflects the second light source and beam splitter 107. ) And a reflecting mirror 109, collimator lens 111, the objective lens 113 is focused on a disk.

Here, the second QWP 118 attaches the entrance and exit glass 118a and 118c to each other, and forms the grating through the nicking on the exit glass 118b.

Then, the second light beam generated from the second laser diode 102 is reflected from the disk 115, and the second reflected light beam is detected as an electrical signal to the photo detector through the reverse path and output as a servo and RF signal. .

As described above, different laser diode powers are required when removing information when recording information on the disk and when reading record information. In order to check the power state of the objective lens 113 in order to change the laser diode power as described above. As a means for detecting the optical power in the monitor PD (123).

However, in the related art, first and second QWP 105 and 118 are respectively provided to make the first and second laser diodes 101 and 102 into circularly polarized light, and the first and second QWP 105 and 118 are respectively provided. QWP 105b, 118b is provided between the glass 105a, 105c, 118a, 118c on the incidence and exit sides, and grating-etched on the exit side glass 105c, 118c. Accordingly, there is a problem in that the number of parts as a whole increases and the work process increases.

The present invention has been made to solve the above problems, and an object thereof is to provide an optical pickup apparatus capable of realizing a linear flat optical system using grating without using a conventional QWP.

Optical pickup device according to the present invention for achieving the above object,

A plurality of laser diodes generating beams of different wavelengths;

A beam splitter for transmitting or reflecting the beam according to a polarization direction;

Grating for dividing the light beam generated from the laser diode into three beams;

A reflection mirror for changing the optical path of the incident beam toward the objective lens;

A collimator lens positioned between the laser diode and the objective lens to make the beam a parallel beam;

An objective lens for focusing the incident beam on the disk;

A sensor lens for correcting astigmatism of the reflected light beam,

And a photo detector for detecting the reflected light beam reflected from the disk as an electrical signal.

Preferably, the grating is configured between each laser diode and beam splitter, the first grating dividing the first light beam from the first laser diode into three beams, and the second light beam generated from the second laser diode. And second grating dividing into beams.

Hereinafter, with reference to the accompanying drawings as follows.

2 is a block diagram showing an optical system of a conventional optical pickup device of different wavelengths.

Referring to FIG. 2, first and second gratings, which are divided into three beams by using the first and second laser diodes 201 and 202 generating different wavelengths, the correcting lens 203 and the diffraction phenomenon of the incident beam, are divided into three beams. (203, 218), a beam splitter (207) for transmitting or reflecting a beam according to the polarization direction, a reflection mirror (209) for reflecting an incident beam in the objective lens direction, a collimator lens (211) for making the beam into a parallel beam, The objective lens 213 for condensing the incident beam on the disk 215, the half mirror 217, the sensor lens 205 for correcting astigmatism of the reflected light beam, and the reflected light beam reflected from the disk 215. And a monitor PD 223 for measuring the optical power condensed on the disk 215.

Referring to the accompanying drawings, the optical pickup device according to an embodiment of the present invention configured as described above is as follows.

Referring to FIG. 2, the first light source generated from the first laser diode (eg, CD LD) 201 may be circularly polarized through the CD lens 203 and the first grating 205. The converted lens is incident on the beam splitter 207. The correction lens 203 is a lens that compensates for a mechanical position and the like so as to maintain a certain distance from the collimator lens 211 that creates a parallel beam. . The first grating 205 is an optical device that splits a beam into three beams by constructive and destructive interference using a diffraction phenomenon of light.

Here, the first grating 205 solves only the grating, which is the single element, without using the first QWP as shown in FIG. 1, thereby configuring the linear flat optical system.

The first light beam passing through the first grading 205 is reflected by the beam splitter 207, and the reflected first light beam is reflected in the direction of the objective lens in the reflection mirror 209 and is a collimator lens. It is made into a parallel beam by 211 and is condensed at one point on the disk 215 through the objective lens 213.

The first reflected light beam reflected from the disk 215 is an objective lens 213, a collimator lens 211, a reflection mirror 209, a beam splitter 207, a half mirror 217, and a sensor lens 219. The light is collected by the photodetector 221 and detected as an electrical signal. The detected signal is used to output servo and RF control signals. Here, the sensor lens 119 is not a uniform curvature of the lens surface, but differently configured in the vertical direction and the horizontal direction to generate astigmatism.

At this time, the first reflected light beam detected by the photo detector 221 is detected as shown in FIG. That is, FIG. 3 is a product light model (CD-LPC-711) (a) is the main light beam using the first QWP (with QWP), (b) is the first grating without the first QWP (without QWP) ) Is the main light beam. These two main light beams hardly cause measurement errors in beam size and beam shape. That is, the same optical performance can be obtained without using the existing QWP using only a single first grating.

On the other hand, the second light beam generated from the second laser diode (eg, DVD LD) 202 passes through the second grading 218 and is incident on the half mirror 217, and the half mirror 217 emits the second light beam. The light is reflected and collected at a point on the disk through the beam splitter 207, the reflection mirror 209, the collimator lens 211, and the objective lens 213.

Here, the second grating 218 is an optical device that splits a beam into three beams by constructive and destructive interference by using a diffraction phenomenon of light, and does not have a second optical QWP as shown in FIG. It consists of a linearly polarized optical system.

Then, the second light beam generated from the second laser diode 202 is reflected from the disk 215, and the second reflected light beam is detected as an electrical signal to the photo detector 221 through the reverse path, so that the servo and RF signals Is output.

At this time, the second reflected light beam is detected by the photodetector 221. As shown in FIG. 4, (a) of the product model (DVD-LPC-711) is detected by using a second QWP (with QWP). Main and sub light beams, and (b) are main and sub light beams detected using only the second grating of the present invention (without QWP). As compared, the two main beams and the sub beams are almost identical in beam size and beam shape, so there is little measurement error.

As described above, different laser diode powers are required when removing information when recording information on the disk and when reading record information. Thus, to check the power state of the objective lens 213 in order to change the laser diode power. As a means for detecting the optical power in the monitor PD (223).

In this way, the linearly polarized optical system is constructed using only the first and second gratings, and thus the same beam size and beam shape are detected without using the existing QWP. You do not have to do this. In addition, the product can be replaced with domestically produced products to secure price competitiveness.

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, the optical pickup device according to the present invention simply installs the grating without using the conventional QWP, thereby realizing the linear polarization optical system instead of the circular polarization optical system, and providing the conventional QWP. Since there is no need to use, there is an effect that can reduce the optical component.

1 is a block diagram showing a conventional optical pickup device.

2 is a block diagram showing an optical pickup device according to an embodiment of the present invention.

Figure 3 is a shape of the main beam when using the CD LD of the prior art and the present invention.

4 is a shape diagram of the main and sub-beams when using the DVD LD of the prior art and the present invention.

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

201 ... first laser diode 202 ... second laser diode

203 ... correction lens 205,218 ...

207 ... beam splitter 209 ... reflective mirror

211 ... collimator lens 213 ... objective lens

215 ... Disk 217 ... Half Mirror

219 sensor lens 221 photodetector

Claims (2)

A plurality of laser diodes generating beams of different wavelengths; A beam splitter for transmitting or reflecting the beam according to a polarization direction; Grating for dividing the light beam generated from the laser diode into three beams; A reflection mirror for changing the optical path of the incident beam toward the objective lens; A collimator lens positioned between the laser diode and the objective lens to make the beam a parallel beam; An objective lens for focusing the incident beam on the disk; A sensor lens for correcting astigmatism of the reflected light beam, And an optical detector for detecting the reflected light beam reflected from the disk as an electrical signal. The method of claim 1, The grating is configured between each radar diode and the beam splitter, and includes a first grating for dividing the first light beam from the first laser diode into three beams and a second light beam generated from the second laser diode into three beams. And a second grating.