KR20060082359A - Optical pickup - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pick-up apparatus, and applies a wedge plate instead of a conventional cubic prism, and constitutes an optical system provided with a common monitor light receiving unit capable of monitoring two light sources. By doing so, there is an excellent effect that can increase the price competitiveness of the optical pickup.

Optical pickup, optical system, wedge plate, light source, prism

Description

Optical pick-up apparatus             

1 is a view schematically showing an optical system constituting a conventional optical pickup device

2 is a configuration diagram schematically showing an optical system of the optical pickup apparatus according to the first embodiment of the present invention.

3 is a conceptual diagram illustrating aberration when a tilted plate exists in a generally emitted light path

4 is a conceptual diagram illustrating a method of reducing aberration with a wedge plate used according to the present invention.

5 is a configuration diagram schematically illustrating an optical system of an optical pickup apparatus according to a second exemplary embodiment of the present invention.

6A and 6B are conceptual views illustrating a state in which light from a light source is incident on a monitor light receiving unit according to the present invention.

7 is a conceptual diagram illustrating a relationship between a wedge plate and a first light source used according to the present invention.

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

100,170 light source 115,175 grating element

120,121: wedge plate 125: mirror

130,410 collimator lens 135: objective lens

150: beam splitter 155: lens

160: light receiver 250: monitor light receiver

400: light source

405: tilted plate

The present invention relates to an optical pickup device, and more particularly, by applying a wedge plate instead of the expensive cubic prism, the price competitiveness of the optical pickup device can be secured, and two light sources The present invention relates to an optical pickup apparatus capable of increasing the price competitiveness of an optical pickup by configuring an optical system provided with a common monitor light receiving unit capable of monitoring the optical pickup.

In recent years, the storage medium has been changed from tape to disk due to the digitization of data, the increase in capacity, and the like, and the storage capacity of the disk has been increased by increasing the recording density for storing data on the disk.

Therefore, in compact discs (CD), in which a laser diode used as a light source has a wavelength of 780 nm, discs suitable for wavelengths of 650 nm and 405 nm have recently been developed for the purpose of large capacity.

Accordingly, various optical pickup apparatuses for recording and reproducing information on the disc have been developed so that they can be simultaneously applied to discs having different storage densities in terms of backward compatibility.

In addition, in the optical disc market, the demand for high speed recording is increasing and the demand for reducing the price of the optical pickup device is also increasing.

1 is a view schematically showing an optical system constituting a conventional optical pickup apparatus, comprising: first and second light sources 11 and 21 separately installed to generate a light beam of 650 nm and a light beam of 780 nm, respectively; Grating elements 12 and 22 for making light generated from these light sources 11 and 21 into light for disk tracking; A half mirror 13 which reflects the light generated from the first light source 11 and transmits or reflects it according to the polarization state of the incident light; A prism 30 for transmitting or reflecting light input from the half mirror 13 and the second light source 21, respectively; A collimator lens 31 for advancing the light passing through the prism 30 in parallel in a predetermined direction; A mirror (32) for reflecting light passing through the collimator lens (31); An objective lens 33 for condensing the light reflected by the mirror 32 at a point on the surface of the disk 50; A photodiode that detects reflected light reflected from the disk 50 incident through the objective lens 33, the mirror 32, the collimator lens 31, the prism 30, and the half mirror 13 and converts the reflected light into an electrical signal. 71; A first monitor photodiode (61) for detecting the light of the first light source (11) transmitted from the half mirror (13) and outputting a monitor signal; And a second monitor photodiode 62 which detects light of the second light source 21 transmitted through the prism 30 and outputs a monitor signal.

First, the operation of recording and reproducing information on the DVD will be described. In the first light source 11, light corresponding to 650 nm is generated, and the light generated in this way is changed to light for disc tracking by the grating 12. Then, it enters into the half mirror 13.

The half mirror 13 reflects a part of light incident from the first light source 11 to the prism 30, and transmits the remaining light to the monitor photodiode 61.

Then, the light is transmitted by the prism 30 and becomes parallel light to the collimator lens 31, and is reflected by the mirror 32 to be incident on the objective lens 33.

Thereafter, the light is collected by the objective lens 33 and focused on the disk 50.

Here, the disk 50 is a DVD.

The light reflected from the disk 50 is incident on the photodiode 71 through the objective lens 33, the mirror 32, the collimator lens 31, the prism 30, and the half mirror 13. The photodiode 71 converts the incident light into an electrical signal and outputs the electrical signal.

In addition, in the operation of recording and reproducing information on the CD, light corresponding to 780 nm is generated in the second light source 21, and the light is changed to the disk tracking light by the grating 12 to the prism 30. Incident.

The prism 30 reflects a part of the light incident from the second light source 21 to the prism 30, and transmits the remaining light to the monitor photodiode 62.

The light reflected by the prism 30 becomes parallel light in the collimator lens 31, is reflected by the mirror 32, is incident on the objective lens 33, and is collected by the objective lens 33 to collect the disk ( Focused on 50).

Here, the disk 50 is a CD.

As in the case of the above-described DVD, the light reflected from the disc 50 is transferred through the objective lens 33, the mirror 32, the collimator lens 31, the prism 30, and the half mirror 13. The photodiode 71 is incident on the photodiode 71, and the photodiode 71 converts the incident light into an electrical signal and outputs the electrical signal.

As described above, in the prior art, the price of the optical pickup device is high by using a conventional expensive cubic prism, and two monitor light receiving units for monitoring two light sources are installed, which is disadvantageous in terms of price. There is this.

In order to solve the problems described above, the present invention can secure the price competitiveness of the optical pickup device by applying a wedge plate instead of the expensive cubic prism, and can monitor two light sources. An object of the present invention is to provide an optical pickup device capable of increasing the price competitiveness of an optical pickup by configuring an optical system provided with a common monitor light receiving unit.                         

A first preferred aspect for achieving the above objects of the present invention comprises: first and second light sources that generate and emit first and second light, respectively, and are spaced apart from each other;

A wedge plate that transmits a part of the incident light, including the light emitted from the first light source, and reflects the rest of the light, and a surface opposite to one surface thereof is wider than one surface thereof;

A beam splitter for reflecting a portion of the light emitted from the second light source to the wedge plate and transmitting the remaining portion, and reflecting or transmitting a portion of the incident light;

A mirror configured to reflect incident light including light incident from the wedge plate;

A collimator lens for advancing the light reflected from the mirror in parallel in a predetermined direction;

An objective lens for condensing light through the collimator lens on a disk;

A light receiving unit converting the light reflected from the disk into an electrical signal when it is detected through an objective lens, a collimator lens, a mirror, a wedge plate, and a beam splitter;

There is provided an optical pickup device comprising an optical pickup device configured to include a monitor light receiving unit which detects light emitted from the first and second light sources and outputs a monitor signal.

A second preferred aspect for achieving the above objects of the present invention comprises: first and second light sources which generate and emit first and second light, respectively, and are spaced apart from each other;                         

A wedge plate for transmitting the light emitted from the first light source and reflecting the light emitted from the second light source;

A beam splitter for reflecting a portion of the light emitted from the second light source to the wedge plate and transmitting the remaining portion, and reflecting or transmitting a portion of the incident light;

A collimator lens configured to propagate the light reflected by the beam splitter in parallel in a predetermined direction;

A mirror configured to reflect incident light including light through the collimator lens;

An objective lens for condensing the light reflected by the mirror onto a disk;

A light receiving unit converting the light reflected from the disk into an electrical signal when it is detected through an objective lens, a mirror, a collimator lens and a beam splitter;

There is provided an optical pickup device including a monitor light receiving unit that detects light emitted from the first and second light sources and outputs a monitor signal.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 2 is a schematic diagram illustrating an optical system of an optical pickup apparatus according to a first exemplary embodiment of the present invention. First and second lights are generated and emitted, respectively, and are spaced apart from each other. and; A wedge plate 120 which transmits a part of the incident light including the light emitted from the first light source 110 and reflects the rest of the light; A beam splitter (150) for reflecting a part of the light emitted from the second light source (170) to the wedge plate (120) and transmitting the rest, and reflecting or transmitting a part of the incident light; A mirror (125) for reflecting incident light including light incident from the wedge plate (120); A collimator lens 130 for traveling the light reflected from the mirror 125 in a parallel direction; An objective lens 135 for condensing light through the collimator lens 130 to the disk 200; When the light reflected from the disk 200 is detected through the objective lens 135, the collimator lens 130, the mirror 125, the wedge plate 120, and the beam splitter 150, the light receiver 160 converts the electric signal into an electrical signal. )Wow; And a monitor light receiver 250 which detects light emitted from the first and second light sources 110 and 170 and transmitted from the wedge plate 120 and the beam splitter 150 to output a monitor signal.

Here, it is preferable that a lens 155 is further provided between the light receiving unit 160 and the beam splitter 150 to condense the light transmitted from the beam splitter 150.

Further, the light emitted from the first and second light sources 110 and 170 is disc-tracked between the first light source 110 and the wedge plate 120 and between the second light source 170 and the beam splitter 150. It is preferable that grating elements 115 and 175 made of molten light are further provided.

In addition, the first and second light sources 110 and 170 may be laser diodes, and the light receiver 160 and the monitor light receiver 250 may be photodiodes.

In addition, it is preferable that the disk 200 is one of two disks which are selectively switched so that the recording surface thereof is coincident with the objective lens focus.

Preferably, the two discs are any one of a CD and a DVD, a CD and a BD (Blu-ray Disc), and a DVD and a BD.

In addition, the disk 200 of FIG. 2 may be any one of a CD, a DVD, and a BD (Blu-ray Disc).

In the first embodiment of the present invention configured as described above, the light emitted from the first and second light sources 110 and 170 is reflected by the wedge plate 120 and the beam splitter 150, respectively, and is reflected by the mirror 125 to collimator lens 130. The light becomes parallel light through the light beams, and is focused by the objective lens 135 and focused on the disk 200.

The light reflected from the disk 200 is incident on the light receiving unit 160 through the objective lens 135, the collimator lens 130, the wedge plate 120, the beam splitter 150, and the lens 155. Is converted into a signal.

Meanwhile, the light emitted from the first and second light sources 110 and 170 is partially reflected by the wedge plate 120 and the beam splitter 150, and the remaining light is transmitted to be incident to the monitor light receiving unit 250. The light receiver 250 detects the incident light and outputs a monitor signal.

3 is a conceptual diagram illustrating aberration when a tilted plate exists in a light path that is generally emitted, and is generally a tilted plate in the light path that is emitted from the light source 400 to the collimator lens 410. If 405 is present, astigmatism and coma occur, and this aberration can be calculated through Equations 1 and 2 below.

As can be seen in Equations 1 and 2 above, when the tilted plate is disposed in the divergent light section, the number is proportional to the thickness of the plate, the tilted angle and the NA of the collimator lens.

At this time, when the plate thickness t of the square plate shape is 1.5 mm, NA is 0.12, the tilt angle u is 30 °, and the wavelength λ of the light is 660 nm, the aberration is calculated.

Astigmatism = 0.341 lambda rms and coma = 0.0601 lambda rms.

Therefore, the total wave front aberration is approximately 0.383 lambda rms.

In general, since the total wave front aberration of the optical pickup device requires 0.07 lambda rms or less, when using this rectangular plate-shaped plate, the aberration is so large that the jitter becomes large when the signal of the optical disc is read or recorded. The deterioration of the RF signal is severe and the performance of the optical pickup device may not be achieved.

FIG. 4 is a conceptual view illustrating a method of reducing aberration with a wedge plate used according to the present invention, and extends by a wedge angle θ at the plate-shaped plate surface of FIG. 3. By placing the wedge plate 406 in the diverging optical path, astigmatism and coma aberration are reduced to minimize aberration.

Since the tilted wedge plate is significantly different from the rectangular plate shape plate as shown in FIG. 3, astigmatism and coma aberration cannot be calculated using Equations 1 and 2. FIG.

Therefore, the present invention is an optical design program under the condition that the plate thickness t (thickness of the central axis) is 1.5 mm, NA is 0.12, the tilt angle u is 30 °, and the wavelength of light λ is 660 nm. The aberration was calculated in Code V. The astigmatism was calculated as 0.0033λrms, and the coma aberration was calculated as 0.0132λrms.

That is, comparing the aberration amount with the case of FIG. 3 without the wedge angle, it can be seen that the astigmatism is reduced to less than one hundredth, and the coma aberration is also reduced to less than one fifth.

For this reason, the wedge plate can minimize the path difference between the sagittal light and the tangential light perpendicular to the sagittal light, thereby reducing the aberration.

 Therefore, the wedge plate described above can be applied to the optical pickup apparatus because the total wavefront number is 0.0172 lambda rms, which is equal to or less than 0.07 lambda rms, which is the wavefront aberration required level of the optical pickup apparatus.

FIG. 5 is a schematic diagram illustrating an optical system of an optical pickup apparatus according to a second exemplary embodiment of the present invention. First and second lights are generated and emitted, respectively, and are spaced apart from each other. and; A wedge plate (121) for transmitting the light emitted from the first light source (110) and reflecting the light emitted from the second light source (170); A beam splitter (150) for reflecting a part of the light emitted from the second light source (170) to the wedge plate (120) and transmitting the rest, and reflecting or transmitting a part of the incident light; A collimator lens 130 for traveling the light reflected by the beam splitter 150 in parallel in a predetermined direction; A mirror (125) for reflecting incident light including light through the collimator lens (130); An objective lens 135 for condensing the light reflected by the mirror 125 on the disk 200; A light receiving unit 160 for converting light reflected from the disk 200 into an electrical signal when it is detected through an objective lens 135, a mirror 125, a collimator lens 130 and a beam splitter 150; And a monitor light receiver 250 for detecting the light emitted from the first and second light sources 110 and 170 and transmitted from the beam splitter 150 to output a monitor signal.

According to the second embodiment of the present invention configured as described above, the light emitted from the first and second light sources 110 and 170 is transmitted and reflected by the wedge plate 121 and is reflected by the beam splitter 150 through the collimator lens 130. It becomes parallel light, is reflected by the mirror 125, is collected by the objective lens 135, and is focused on the disk 200.

In addition, the light reflected from the disk 200 is incident to the light receiving unit 160 through the objective lens 135, the mirror 125, the collimator lens 130, the beam splitter 150, and the lens 155. Converted into an electrical signal.

In addition, the light emitted from the first and second light sources 110 and 170 is partially transmitted from the beam splitter 150 to be incident on the monitor light receiver 250, and the monitor light receiver 250 detects the incident light. Outputs the monitor signal.

6A and 6B are conceptual views illustrating a state in which light of a light source is incident on a monitor light receiving unit according to the present invention. First, the wedge plate and the beam splitter in FIG. 2, which is the first embodiment of the present invention, are the second embodiment of the present invention. In FIG. 5, the beam splitter is shown as '500' as shown in FIG. 6A. The wedge plate and the beam splitter reflect some of the light emitted from the light source and transmit the remaining light to enter the monitor light receiver 250.

However, as shown in FIG. 6B, when a part of the light emitted from the light source is positioned so as not to be incident on the wedge plate or the beam splitter 500, and the wedge plate or the beam splitter 500 is configured to reflect the light of the incident light source, the light source Most of the light emitted from is reflected, and a small amount of light (within about 1% of the total light) is not irradiated to the wedge plate or the beam splitter 500, but is incident directly to the monitor light receiver 250.

That is, in FIG. 2, the wedge plate 120 is positioned so that a part of the light emitted from the first light source 110 is incident on the monitor light receiving unit 250, and the remaining light is incident and reflected to be emitted to the mirror 125. .

And, the beam splitter 150 of FIG. 2 is positioned so that a part of the light emitted from the second light source 170 is incident on the monitor light receiving unit 250, and the remaining light is incident and reflected to be emitted to the wedge plate 120. do.

In addition, the beam splitter 150 of FIG. 5 is positioned so that a part of the light emitted from the first and second light sources 110 and 170 is incident on the monitor light receiving unit 250, and the remaining light is incident and reflected to the collimator lens 130. It is configured as possible.

In addition, the wedge plate and the beam splitter may be configured to transmit according to the polarization state of the incident light, thereby allowing the light reflected from the disk to enter the light receiving unit.

Therefore, in the case of Fig. 6B, all the light emitted from the light source and sent to the disk can be sent to the disk, so that the light efficiency is high, and high speed recording and reproduction can be performed.

Then, the light reflected from the disk is transmitted and incident to the light receiving portion.

FIG. 7 is a conceptual diagram illustrating a relationship between a wedge plate and a first light source used according to the present invention, wherein light emitted from the first light source 110 is incident angle α (10 ° <α <45 °). It is preferable to install the wedge plate 120 to be incident to.

As described above, the present invention can secure the price competitiveness of the optical pickup device by applying a wedge plate instead of the expensive cubic prism, and can monitor two light sources. By configuring the optical system provided with the common monitor receiving unit, there is an excellent effect that can increase the price competitiveness of the optical pickup.                     

Although the invention has been described in detail only with respect to specific examples, it will be apparent to those skilled in the art that various modifications and variations are possible within the spirit of the invention, and such modifications and variations belong to the appended claims.

Claims (8)

First and second light sources that generate and emit the first and second lights, respectively, and are spaced apart from each other; A wedge plate that transmits a part of the incident light, including the light emitted from the first light source, and reflects the rest of the light, and a surface opposite to one surface thereof is wider than one surface thereof; A beam splitter for reflecting a portion of the light emitted from the second light source to the wedge plate and transmitting the remaining portion, and reflecting or transmitting a portion of the incident light; A mirror configured to reflect incident light including light incident from the wedge plate; A collimator lens for advancing the light reflected from the mirror in parallel in a predetermined direction; An objective lens for condensing light through the collimator lens on a disk; A light receiving unit converting light reflected from the disk into an electrical signal when detected through an objective lens, a collimator lens, a mirror, a wedge plate, and a beam splitter; And a monitor light receiver configured to detect light emitted from the first and second light sources and output a monitor signal. First and second light sources that generate and emit the first and second lights, respectively, and are spaced apart from each other; A wedge plate for transmitting the light emitted from the first light source and reflecting the light emitted from the second light source; A beam splitter for reflecting a portion of the light emitted from the second light source to the wedge plate and transmitting the remaining portion, and reflecting or transmitting a portion of the incident light; A collimator lens configured to propagate the light reflected by the beam splitter in parallel in a predetermined direction; A mirror configured to reflect incident light including light through the collimator lens; An objective lens for condensing the light reflected by the mirror onto a disk; A light receiving unit converting the light reflected from the disk into an electrical signal when it is detected through an objective lens, a mirror, a collimator lens and a beam splitter; And a monitor light receiver configured to detect light emitted from the first and second light sources and output a monitor signal. The method according to claim 1 or 2, The wedge plate and the beam splitter, A part of the light emitted from the first and second light sources is positioned so as not to be incident, The monitor light receiver, And pick up light emitted from said first and second light sources and not incident to said wedge plate and beam splitter. The method according to claim 1 or 2, Between the light receiving unit and the beam splitter, And a lens for condensing the light transmitted from the beam splitter. The method according to claim 1 or 2, The first and second light sources are laser diodes, And the light receiving unit and the monitor light receiving unit are photodiodes. The method according to claim 1 or 2, The disk, And an optical pickup device which is optionally switched so that its recording surface is one of two disks coinciding with the objective lens focus. The method of claim 1, The disk, An optical pickup apparatus, which is any one of a CD, a DVD, and a BD (Blu-ray Disc). The method of claim 1, The wedge plate is provided so that the light generated from the first light source is incident at an incident angle α (10 ° <α <45 °).

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