KR100658888B1 - Apparatus for optical pick-up - Google Patents

Abstract

The present invention relates to an optical pickup device, and more particularly, to an optical pickup device using a three wavelength laser diode.

The optical pickup device according to the present invention comprises a laser diode for generating a three-wavelength beam, a collimator lens for causing the beam to run in parallel, an objective lens for collecting the beam at the correct point of the optical disk, and reflection from the optical disk. An optical pickup apparatus including a photo detector for reading out a beam, wherein the three reflective layers are provided so that the paths of the three wavelength beams emitted from the laser diode are matched, and the incident beam is transmitted or transmitted according to the polarization direction of the incident beam. And a first beam splitter for reflecting, and a second beam splitter having a predetermined thickness such that the beam reflected from the optical disk generates a boiling point for servo detection.

Optical pickup

Description

Optical pickup device {APPARATUS FOR OPTICAL PICK-UP}

1 is a view for explaining an optical pickup device using two conventional laser diodes.

2 is a view for explaining that a laser diode having three chips is formed in one conventional package.

3 is a view for explaining an example in which chips of each wavelength are arranged in a laser diode having three chips.

Fig. 4 is a diagram for explaining the beam shape in the photo detector according to the state in which chips of each wavelength are arranged;

5 is a view for explaining an optical pickup device according to the present invention.

6 is another embodiment illustrating an optical pickup device according to the present invention.

7 is yet another embodiment illustrating an optical pickup device according to the present invention.

8 and 9 show an embodiment of the aberration correction element.

<Explanation of symbols for main parts of drawing>

10; Laser diode 11; Laser diode

20; Mirror 30; Collimator lens

40; Objective lens 50; Optical disc

60; Beam splitter 70; Cylinder lens

80; Photo detector 110; Laser diode

120; Reflection mirror 130; Collimator lens

140; Objective lens 150; Optical disc

161; First beam splitter 162; 2nd beam splitter

163; First beam splitter 164; Aberration Correction Element

170; Cylinder lens 180; Photo detector

The present invention relates to an optical pickup device, and more particularly, to an optical pickup device using a three wavelength laser diode.

An optical disc is a product that records and reproduces information by using optical characteristics, and generally has a small disc shape. In order to use an optical disc, an optical disc driver is required, and information of the optical disc is reproduced or recorded by an optical pickup device mounted inside the optical disc driver.

Such an optical pickup device includes a laser diode (LD) that generates a large beam, a photo detector (PD) that reads a beam reflected on an optical disk, and selectively reflects or transmits the beam according to a polarization direction. Beam splitter is used as an important component.

On the other hand, a mechanism called an actuator (actuator) is used to accurately form a beam on the optical disk, the actuator moves the position of the objective lens that collects the beam from the laser diode to the exact point where the information on the optical disk is recorded by the beam It is a device for improving the performance of reproducing and recording information.

Currently, two or more compatible devices capable of playing back different wavelengths such as DVD and CD have been developed, but two laser diodes must be used to play a disk.

1 is a view for explaining an optical pickup device using two conventional laser diodes.

As shown in FIG. 1, in the conventional optical pickup apparatus using two laser diodes, two laser diodes 10 and 11 are installed and a beam splitter for transmitting or reflecting an incident beam according to the polarization direction of the incident beam. (Beam Splitter) 60, a mirror 20, a collimator lens 30 for allowing the beam to run in parallel in a predetermined direction, and an objective lens 40 for collecting the beam at the correct point on the optical disk. ), An optical disk 50, a cylinder lens 70 for generating a boiling point, a photo detector 80 for reading a beam reflected on the optical disk, and the like.

The conventional optical pickup device configured as described above has a problem that the volume becomes large and the structure becomes complicated by using two laser diodes.

Furthermore, the use of three laser diodes such as CD, DVD, BD in the method of FIG. 1 presents a number of problems due to the volume and complexity of the structure.

FIG. 2 is a view for explaining the formation of a laser diode having three chips in one conventional package.

The laser diode having three chips shown in FIG. 2 emits three kinds of optical disks by emitting three wavelengths of beams (for example, CD light, DVD light, BD light) in one laser diode 10. Can play.

However, as shown in FIG. 2, when a beam of three wavelengths is emitted through one laser diode 10, the distance between the chips of each wavelength is approximately 110 μm, which is precise on the optical disc 50. There is a problem that the beam is difficult to form at the point.

In addition, since the beam is not formed at the correct position of the photo detector 80, there is a problem in that the accurate Servo signal and the RF signal cannot be detected.

FIG. 3 is a diagram illustrating an example in which chips of each wavelength are arranged in a laser diode having three chips, and FIG. 4 is a diagram illustrating beam shapes in a photo detector according to the arrangement of chips of each wavelength. .

3 and 4, the shape of the beam formed on the photo detector 80 is also changed depending on whether chips of each wavelength are arranged in the T direction, the R direction, or the mixed direction of the T direction and the R direction.

That is, in the drawing, if the chip emitting the DVD beam is in the center of the laser diode 10, the DVD light is formed at the center of the photo detector 80, and as described above, the CD light is caused by the distance between the chips of each wavelength. And the BD light are formed at positions away from the center of the photo detector 80.

Therefore, the accurate Servo signal and the RF signal cannot be detected for the CD light and the BD light.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides an optical pickup apparatus capable of detecting an accurate servo signal and an RF signal in reproducing three types of optical disks using laser diodes emitting three wavelengths. For that purpose.

The optical pickup device according to the present invention comprises a laser diode for generating a three-wavelength beam, a collimator lens for causing the beam to run in parallel, an objective lens for collecting the beam at the correct point of the optical disk, and reflection from the optical disk. An optical pickup apparatus including a photo detector for reading out a beam, wherein the three reflective layers are provided so that the paths of the three wavelength beams emitted from the laser diode are matched, and the incident beam is transmitted or transmitted according to the polarization direction of the incident beam. And a first beam splitter for reflecting, and a second beam splitter having a predetermined thickness such that the beam reflected from the optical disk generates a boiling point for servo detection.

In addition, an aberration correction device for correcting astigmatism or spherical aberration is further included between the first beam splitter and the optical disk.

The optical pickup apparatus may further include a cylinder lens for detecting a focus error.

In addition, the first beam splitter may be divided into two beam splitters having two reflective layers, respectively, according to the beam arrangement of the laser diode.

Hereinafter, an optical pickup apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

5 is a view for explaining an optical pickup device according to the present invention.

FIG. 5 illustrates a case where chips of each wavelength of the laser diode 110 are arranged in the R direction, in which chips of each wavelength in FIG. The case where the R (Radial) direction and the T direction are mixed and arranged will be described separately.

However, the basic gist of the present invention does not differ depending on the arrangement of the chip in the R direction, the T direction, or a mixture of the R direction and the T direction, and only slightly differs in the position and operation of the components.

Referring to FIG. 5, the present invention is provided with a laser diode 110 for emitting lasers of three wavelengths (eg, BD light, CD light, DVD light), and at each of the wavelengths of the laser diode 110. The distance between the chips is formed to about 110㎛.

The wavelengths emitted by the three chips BD, DVD, and CD are 405 nm, 650 nm, and 780 nm. Of course, the wavelength emitted may vary depending on the type of chip installed, the manufacturer, and the manufacturing process.

The centers of the three beams are emitted through different paths according to the distance between the chips, and the first beam splitter 161 having a predetermined thickness allows the three beams to coincide. In addition, the first beam splitter 161 selectively transmits or reflects the incident beam according to the polarization direction of the incident beam.

The first beam splitter 161 is formed with three reflective layers, for example, the BD light is reflected from the front reflective layer of the first beam splitter 161 to the optical disk 150, and the DVD light is the intermediate reflective layer. And the CD light is reflected by the back reflection layer of the first beam splitter 161 and travels toward the optical disc 150 in a path consistent with the BD light. Here, the thickness of the first beam splitter 161 and the position of the reflective layer may be appropriately adjusted according to the spacing of the chips emitting three beams.

Thus, it is possible to compensate for the image due to the bevel angle of the beam emitted from the three chips.

The beam passing through the first beam splitter 161 is a reflecting mirror 120, a collimator lens 130 that allows the beam to run in parallel in a predetermined direction, and an object that collects the beam at an exact point on the optical disk. Through the lens 140 is formed in the correct position of the optical disk 150.

Here, the reflective mirror 120 is to reduce the size or volume of the optical pickup device may be optionally required in some cases.

Meanwhile, as the CD light and the DVD light are reflected by the rear reflection layer and the intermediate reflection layer of the first beam splitter 161, astigmatism, coma, and spherical aberration may be generated according to the distance between the reflection layers.

This is not a problem when the spacing between the reflective layers of the first beam splitter 161 is small, that is, when the spacing of the three chips is very small.

Astigmatism and spherical aberration can be corrected by including an aberration correcting element 164 between the first beam splitter 161 and the reflecting mirror 120 or between the reflecting mirror 120 and the collimator lens 130. Since the aberration correcting element 164 corrects only aberration, not changing the path of the beam, the aberration correcting element 164 does not significantly reduce the light efficiency.

Meanwhile, in the case of coma aberration, the influence is insignificant, and can be corrected by the tilt triaxial actuator or the image compensation objective lens 140.

The beam reflected from the optical disk 150 passes through the objective lens 140, the collimator lens 130, the reflection mirror 120, and the aberration correction element 164, and passes through the first beam splitter 161. .

The beam past the first beam splitter 161 passes through a second beam splitter 162 formed to a predetermined thickness, wherein the second beam splitter 162 is formed to a suitable thickness for focusing servo generation. That is, since the thickness t1 of the first beam splitter 161 cannot make a boiling point for generating the servo, the second beam splitter 162 is provided to generate the boiling point.

Meanwhile, the first beam splitter 161 and the second beam splitter 162 may be integrally formed and may be adjacent to each other. In addition, the first beam splitter 161 may be installed separately according to the arrangement direction of each chip.

The beam passing through the second beam splitter 162 is precisely formed at the center of the photo detector 180 through the cylinder lens 170 for focus error detection. The cylinder lens 170 may be omitted depending on the shape of the second beam splitter 162.

6 is another embodiment illustrating an optical pickup device according to the present invention.

In FIG. 6, chips having respective wavelengths are arranged in the T direction, and descriptions of the same configuration and operation as those described with reference to FIG. 5 will be omitted.

As shown in FIG. 6, the centers of the three beams are emitted through different paths according to the distance between the three chips. Or " total mirror ".

The first beam splitter 161 is formed with three reflective layers, and thus it is possible to compensate for an image due to the bevel angle of the beam emitted from the three chips.

The beam passing through the first beam splitter 161 is provided with an aberration correction element 164, a collimator lens 130 that allows the beam to run in parallel in a predetermined direction, and collects the beam at an exact point on the optical disk. Through the objective lens 140 is formed at the correct position of the optical disk 150.

In addition, the reflective mirror 120 may be selectively installed.

The beam reflected from the optical disk 150 is reflected by the first beam splitter 161 after passing through the objective lens 140, the collimator lens 130, and the aberration correcting element 164.

The beam past the first beam splitter 161 passes through a second beam splitter 162 formed to a predetermined thickness, wherein the second beam splitter 162 is formed to a suitable thickness for focusing servo generation.

The beam passing through the second beam splitter 162 is precisely formed at the center of the photo detector 180 through the cylinder lens 170 for focus error detection.

Therefore, it is possible to ensure that the beams emitted from the three chips are exactly at the center of the photo detector 180.

7 is another embodiment for explaining the optical pickup device according to the present invention.

FIG. 7 shows a case where chips of each wavelength are arranged in a mixture in the T and R directions.

As shown in FIG. 7, the centers of the three beams are emitted to different paths according to the distance between the three chips, and through one first beam splitter 161, one beam is matched with the path of the other beam. The other third beam splitter 163 allows the other beam to coincide with the path of the other beam.

That is, in the embodiment shown in FIG. 7, unlike the embodiment shown in FIGS. 5 and 6, a third beam splitter 163 is further installed.

This is for correcting beams emitted by the chips arranged in the T and R directions, and the beams emitted from the chips arranged in the R direction are corrected through one first beam splitter 161, and the T direction. The beams emitted from the chips arranged as are corrected through the other third beam splitter 163.

Except for this difference, the embodiment described in FIGS. 5 and 6 and the operating principle thereof are the same.

Accordingly, the beams passing through the two first beam splitters 161 and the third beam splitter 163 are directed toward the optical disk 150 in a state consistent with the path of the reference beam.

8 and 9 show an embodiment of the aberration correcting element.

The aberration correcting element 164 is formed in a concentric pattern as shown in FIG. 8, and when a beam having a predetermined wavelength is transmitted through the pattern, a phase difference is generated.

For example, when the aberration correction element 164 is applied to a DVD beam, a phase difference of 360 degrees is generated when a beam of 405 nm and 780 nm is transmitted, so that the CD beam or BD beam is not affected, and the beam of 650 nm (DVD When the beam is passed, the phase difference is given to correct the beam.

In some cases, the aberration correction element 164 may be formed for each of the two beams.

As a result, as shown in FIG. 10, the optical pickup device according to the present invention can be seen that all three beams are exactly formed at the center of the photo detector.

The present invention has an advantage of providing an optical pickup apparatus capable of detecting accurate servo signals and RF signals in reproducing three types of optical disks by using laser diodes emitting three wavelengths.

Claims (4)

A laser diode generating a beam of three wavelengths, wherein chips of each wavelength are arranged mixed in a tangential direction and a radial direction; A first beam splitter for matching a path of a beam emitted from the chips arranged in the radial direction, A third beam splitter for matching a path of a beam emitted from the chips arranged in the tangential direction; And a second beam splitter integrally formed with the first beam splitter at a predetermined thickness such that the beam reflected from the optical disk generates a boiling point for servo detection. The method of claim 1, And an aberration correcting element for correcting astigmatism or spherical aberration between the first beam splitter and the optical disk. The method of claim 1, And a cylindrical lens for detecting a focus error of the beam passing through the second beam splitter. The method of claim 1, The first beam splitter and the third beam splitter are each provided with two reflective layers and separated according to the chip arrangement of the laser diode.

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