KR100624853B1 - optical unit - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an integrated optical unit, in particular having a prism for optical path conversion between a plurality of light emitting portions and a single light receiving portion, a light emitting portion and a light receiving portion for the integration of an optical device.

The integrated optical unit in the optical pickup apparatus according to the present invention is configured to reflect and transmit light sources generated from the first and second laser diodes and the first and second laser diodes installed in symmetrical directions to generate different wavelengths. A triangular pyramid-shaped reflective prism having a holographic reflecting surface, and an integrated optical module including an integrated photodetector for receiving a reflected light beam passing through the holographic reflecting surface and detecting it as an electrical signal.

Optical pickup, LD, prism, photodetector, hologram element

Description

Optical unit

1 is a block diagram showing an integrated optical unit in a conventional optical pickup device.

2 is a block diagram showing an integrated optical unit in the optical pickup apparatus according to an embodiment of the present invention.

3 is a perspective view of the integrated optical unit of FIG.

4 is a configuration diagram illustrating the hologram reflecting surface of FIG. 2.

5 is a view showing a transmission pattern from the hologram reflecting surface to the photodetector in the present invention.

6 is a schematic representation of a photo detector of the present invention;

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

100 ... Integrated Optics Module 101,102 ... Laser Diodes

110 ... reflective prism 111,112 ...

111a, 112a ... hologram reflector 113 ... light detector

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an integrated optical unit, in particular having a prism for optical path conversion between a plurality of light emitting portions and a single light receiving portion, a light emitting portion and a light receiving portion for the integration of an optical device.

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 view showing a conventional two-wavelength optical pickup apparatus.

Referring to FIG. 1, the beam guide assembly 10 includes a laser diode 11, a reflective prism 12, and a plurality of photo detectors 13 and 14 integrated with each other. It consists of an objective lens 20 for condensing on 30.

In the laser diode 11 of the beam guide assembly 10, the first LD chip and the second LD chip generating light sources having different wavelengths are configured in one package. The first light source is, for example, a laser diode for irradiating light of 650 nm wavelength, and is used as the relatively thin DVD disc. The second light source is, for example, a CD laser diode for irradiating light of 780 nm wavelength, and is used as the relatively thick CD disk. These first and second light sources are arranged approximately (100 ± 2) μm apart.

The reflective prism is manufactured in a predetermined shape, and an inclined surface 12a is formed to reflect the light emitted from the laser diode 11 at a right angle, and the reflected light beam is formed through the objective lens 20 through a disk ( 30 is condensed at one point. Here, the inclined surface 12a serves as a beam splitter capable of reflecting or transmitting light according to the polarization direction.

The light beam focused on the disk 30 is reflected and received by the first photodetector 13 through the inclined surface 12a through the objective lens 20, and the second photodetector 14 is the first photodetector 13. The reflected light received at) is received again through the reflecting surface 12b.

However, conventionally, a plurality of photodetectors are positioned at predetermined intervals inside the reflective prism, resulting in a problem that the shape of the entire unit becomes large. In addition, the conventional optical pickup apparatus controls the tracking servo and the focusing servo using signals detected from the plurality of photodetectors, which causes a complicated problem.

The present invention has been made to solve the above problems, a two-wavelength optical pickup device using an integrated optical module that integrates two laser diodes, a triangular pyramid-shaped reflecting prism, a hologram reflecting surface, and an optical detector It is an object of the present invention to provide an integrated optical unit in an optical pickup device capable of implementing the present invention.

Another object of the present invention is to provide an integrated optical unit in an optical pick-up apparatus in which the optical components can be integrated to reduce the height and the number of components.

Integrated optical unit in the optical pickup device according to the present invention for achieving the above object,

First and second laser diodes installed in symmetrical directions to generate different wavelengths, a triangular pyramid-shaped reflective prism having a hologram reflecting surface to reflect and transmit a light source generated from the first and second laser diodes, and the hologram half And an integrated optical module integrated with a photodetector which receives the reflected light beam passing through the slope and detects the reflected light beam as an electrical signal.

Preferably, the hologram reflecting surface is formed to face the first and second laser diodes at predetermined angles at the center of the inclined surface of the triangular pyramidal reflecting prism.

Preferably, the photo detector includes a main photo detector having a fourth division structure and a sub photo detector having a quad division structure respectively disposed at both sides thereof.

Hereinafter, with reference to the accompanying drawings as follows.

2 is a block diagram of an optical pickup apparatus according to an exemplary embodiment of the present invention. As shown therein, first and second laser diodes 101 and 102 which are symmetrical to the left and right and the symmetric first and second laser diodes are shown in FIG. The triangular prism 110 formed with the hologram reflecting surfaces 111a and 112a which reflects or transmits the beams generated from the beams 101 and 102, and the light disposed under the center of the triangular prism 110 and reflected from the disk, is an electrical signal. It consists of an integrated optical module 100 integrally provided with a light detector 113 for detecting.

The hologram reflecting surfaces 111a and 112a include diffractive regions, and small diffractive regions and dense diffractive regions are formed.

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

2 and 3, a triangular prism 110 is disposed in the center of the integrated optical module 100, and the first and second laser diodes 101 and 102 are symmetrical to the left and right of the triangular prism 110. Is placed.

Here, the first light source used in the first laser diode LD1 101 is, for example, a laser diode that irradiates light of 650 nm wavelength, and is used as the relatively thin DVD disc. The second light source generated by the second laser diode (LD2) 102 is, for example, a CD laser diode for irradiating light of 780 nm wavelength, and is used as the relatively thick CD disk. Alternatively, in the case of a two-wavelength diode, the other laser diode may be a blue laser diode.

And, as shown in (a) (b) of Figure 3, the triangular prism 103, the inclined surfaces (111, 112) are formed on the left and right in a triangular pyramid shape, the diffraction so that the beam is reflected or transmitted on the inclined surfaces (111, 112) The hologram reflecting surfaces 111a and 112a are formed.

Here, the inclined surfaces 111 and 112 form an inclination angle of approximately 30 to 60 degrees, and the first and second hologram reflecting surfaces 111a and 112a formed in a circular shape at the center thereof are engraved with a diffraction grating in a horizontal direction and an oblique direction as shown in FIG. 4. Diffraction zones are formed. The diffraction region is divided into a dense diffraction region and a small diffraction region, and reflects or transmits a beam depending on the polarization direction.

In addition, the first and second hologram reflecting surfaces 111a and 112a form approximately 45 degrees with respect to beams generated from the first and second laser diodes 101 and 102 and are reflected at a substantially right angle.

The beams reflected from the first and second hologram reflecting surfaces 101 and 102 travel in the direction of the objective lens and are focused on the disk, and the beams reflected from the disk reflect the hologram reflecting surfaces 111a and 112a of the triangular prism 110, respectively. Permeate. In this case, the hologram reflecting surfaces 111a and 112a allow the reflected light beams reflected from the disk to be transmitted in the direction perpendicular to the center.

Here, the reflective beams traveling in the disc direction from the first and second hologram reflecting surfaces 111a and 112a and the beams reflected and transmitted from the disk move along the corresponding path. The first light source is reflected or transmitted at the first hologram reflecting surface 111a, and the second light source is reflected or transmitted at the second hologram reflecting surface 112a.

The hologram reflecting surfaces 111a and 112a separate the reflected light beam as shown in FIG. 5 to form an image on the photodetector 113. To this end, a photo detector 113, which is a light receiving element that receives the reflected light beams transmitted to the first and second hologram reflecting surfaces 111a and 112a, is disposed below the center of the triangular prism 110. That is, the reflected light beam transmitted to the first hologram reflecting surface 111a corresponding to the first light source is detected as an electrical signal by the photodetector 113, and the second hologram reflecting surface 112a corresponding to the second light source. The reflected light beam transmitted through is detected by the photodetector 113 as an electrical signal.

As shown in FIG. 6, the photodetector 113 is configured as a single unit to receive the beams passing through the first and second hologram reflecting surfaces 111a and 112a at right angles. The photodetector 113a and the sub photodetectors 113b and 113c of the 4 division structure which are symmetrical to both sides are comprised. The photo detector 113 detects the three beams diffracted by the hologram reflecting surfaces 111a and 112a to obtain a tracking server, a focusing servo, and an RF signal.

That is, the focusing error detection signal FE uses the main beam 113a, and the detection signal is as follows.

FE = (FE1-FE2) + (FE3-FE4)

When the tracking error is detected, a differential push-pull (Dpp) is used. The tracking error detection signal is as follows.

Dpp = Mpp-k * Spp = ((FE3 + FE4)-(FE1 + FE2))-k ((F + H)-(E + G))

Where Mpp is the differential push-pull signal for the main beam, Spp is the differential push-pull signal for the sub-beam, and k is the optimal tracking because the amount of light detected from the sub light detector is too small for the amount of light from the main light detector. The gain is applied to the detection signal of the sub-photodetector so that an error signal is detected. This can be determined by the ratio of the amount of light of diffracted zeroth order light and primary light. As such, the differential push pool is a method of amplifying a signal.

The high frequency signal RF is obtained as the sum of the main beams, which is as follows.

RF = FE1 + FE2 + FE3 + FE4

In this way, the servo signal and the RF signal are extracted from the image formed on the photodetector 113.

Accordingly, by integrating the triangular prism 110, the left and right symmetric diodes 101 and 102 and the lower photodetector 113 integrally, the overall height of the pickup can be reduced and the number of parts can be reduced.

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 integrated optical unit in the optical pickup device according to the present invention, the number of optical components is provided by integrally providing a symmetrical diode, a triangular prism having a hologram reflecting surface, and a photo detector on the left and right sides of the integrated optical unit. It can reduce and reduce the overall height of the pickup.

Claims (3)

A first laser diode and a second laser diode in which beams of different wavelengths are generated; The beam generated by the first laser diode is reflected to reproduce or record data on the optical recording medium, and then the first hologram reflecting surface and the beam generated by the second laser diode are reflected so that the reflected beam is diffracted and transmitted. A reflecting prism having a second hologram reflecting surface formed such that a reflected beam is diffracted and transmitted after reproducing or recording data on a recording medium; A photodetector for receiving a beam passing through the hologram reflecting surface and detecting the beam as an electrical signal; And an optical module including the optical module formed therein so as to support the first laser diode, the second laser diode, and the reflective prism and to place the photo detector under the reflective prism. . The method of claim 1, And the hologram reflecting surface of the reflecting prism is formed at a 45 degree inclination with the traveling path of the beam generated from the first laser diode and the second laser diode. The method of claim 1, And the photo detector comprises a main photo detector having a fourth division structure and a sub photo detector having a quad division structure respectively disposed at both sides thereof.

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