KR20070008283A - Optical pickup apparatus using holography grating - Google Patents

Abstract

An optical pickup device using a holography grating is provided to packages light sources which emit beams having different wavelengths so as to be one LD(Laser Diode) and input the respective beams emitted from the LD to one grating. A light source package(401) includes two or more light sources which generate different wavelengths. A beam splitter(403) splits the beam inputted from the light source package(401) into a main beam and two or more auxiliary beams. A collimating lens(404) adjusts the main beam and the two or more auxiliary beams split in the beam splitter(403) as collimating beams. A light condensing part(405) condenses the main beam and the two or more auxiliary beams adjusted in the collimating lens(404) at a specific position on an optical disc. A photo detecting part detects that the beam condensed by the light condensing part(405) is reflected from the optical disc. The beam splitter(403) includes a holography grating for mutually equalizing split angles of the auxiliary beams for the main beam when splitting the beams having two or more inter-different wavelengths inputted from the light source package(401) into the main beam and the two or more auxiliary beams.

Description

Optical pickup apparatus using holography grating

1 is a schematic diagram showing a schematic structure and an optical path of an example of a conventional optical pickup apparatus.

2A and 2B show the principle of optical separation of the conventional optical pickup apparatus and optical separation using the holographic diffraction grating of the present invention, respectively.

Figure 3 shows the light source package of an embodiment of the optical pickup device of the present invention as viewed from the light emitting side.

4 is a schematic diagram briefly showing an embodiment of the optical pickup apparatus of the present invention.

5 is a graph showing the level of the DPP signal with respect to the distance from the track to which the main light is irradiated to the land to which the auxiliary light is irradiated in the two types of optical discs.

FIG. 6 shows a spot where primary and auxiliary light are radiated onto two types of optical discs according to an embodiment of the optical pickup apparatus of the present invention.

{Description of main parts of the drawing}

101: CD light source and diffraction grating 102: DVD light source and diffraction grating

103: collimation lens 104: objective lens

105: photodiode

201: optical path of incident light 202: optical path of auxiliary light

203: general diffraction shot 204: holographic diffraction shot

205: auxiliary beam refracting angle of the DVD beam 206: auxiliary beam refracting angle of the BD beam

207: Auxiliary Light Refraction Angle by Holographic Diffraction

301: DVD beam light source 302: BD beam light source

401: light source package 402: beam combiner

403: beam splitter 404: collimation lens

405: light collecting means 406: optical disk

407: light detection means

501: DPP signal level graph for DVD

502: DPP signal level graph for BD

603: spot where daylight is irradiated

604: the spot to which the auxiliary light is irradiated

The present invention relates to an optical pickup device, and more specifically, to two or more optical discs using light of different wavelengths, a light source of each light having different wavelengths is bundled into a single photodiode (LD) package, and An optical pickup apparatus characterized by injecting each emitted light into one diffraction grating.

The optical pickup apparatus collects and irradiates light emitted from a light source, which is usually formed of an optical diode, on the optical disk in order to record information on the optical disk (optical recording medium) or reproduce information stored on the optical disk, and the optical disk The tracking servo reads the information stored in the optical disk from the result of photosensitive reflection, adjusts the position where the optical pickup is performed on the optical disk, and adjusts the position where the light source is focused on the track of the optical disk.

The optical pickup apparatus records and reproduces using light of different wavelengths depending on the type of optical disk. In general, an optical pickup apparatus configured to be compatible with two or more optical disks using light having different wavelengths and configured to enable optical pickup includes a light source emitting light of the wavelength for each wavelength and a light emitted from the light source. And a diffraction grating for separating into an auxiliary light and a portion for selecting the light to be collected on the optical recording medium from among the light having various wavelengths according to the optical recording medium used.

1 illustrates a schematic structure and an optical path of an example of a conventional optical pickup apparatus.

The optical pickup device shown in FIG. 1 performs optical pickup for optical discs of CD and DVD, and the light emitted from the light source emitting light having a wavelength suitable for each of the CD and DVD passes through the diffraction grating and is reflected from the mirror. The light collimates through the collimating lens and the objective lens and is focused on the optical disk, and the light reflected from the optical disk reaches the photodiode, which is a photodetector, to perform optical pickup.

The conventional optical pickup apparatus shown in the above example includes a light source for emitting light having a wavelength suitable for each of CD and DVD as a separate photodiode, and separately a diffraction grating for separating the light emitted for each of the separate diodes. Equipped.

It is not desirable to have a photodiode and a diffraction grating separately for each light source as described above in that it increases the volume and cost of the optical pickup device, and bundles the photodiodes of the light source into one package and one diffraction grating therefor. It would be desirable to record and play back optical discs.

An object of the present invention devised to solve the above problems is that a diffraction grating is emitted from a photodiode in which light of different wavelengths is bundled into one package for heterogeneous discs using light of different wavelengths. It is to provide an optical pickup device for passing through the optical pickup.

The optical pickup device of the present invention devised to solve the above problems is a light source package including two or more light sources for generating different wavelengths; A beam splitter separating the light incident from the light source package into main light and at least two auxiliary lights; A collimating lens for adjusting the main light and the at least two auxiliary lights separated by the beam splitter into parallel lights; Condensing means for condensing the main light and the two or more auxiliary lights adjusted by the collimating lens to a specific position on the optical disk; And light detecting means for detecting that the light collected by the light collecting means is reflected from the optical disk, wherein the beam splitter separates two or more light having different wavelengths incident from the light source package into main light and two or more auxiliary lights. It characterized in that it comprises a holographic diffraction grating configured such that the separated angles of the auxiliary light with respect to the chief light are equal to each other.

In the present invention, the optical pickup device preferably further comprises a beam combiner for adjusting the light generated from two or more light sources of the light source package to be incident on the holographic diffraction beam in the same path.

In the present invention, it is preferable that some of the two or more light sources included in the light source package generate light belonging to a range of 400 to 450 nm and the other part generate light belonging to a range of 600 to 700 nm.

In the present invention, the holographic diffraction grating is such that the auxiliary light closest to the main light is located on a land 1.115 um away from the groove to which the main light is irradiated in a direction perpendicular to the track direction, and the main light is irradiated to a spot symmetric about the spot to which the main light is irradiated. It is preferable to separate the at least two auxiliary light.

In the present invention, some of the light sources included in the light source package generates light in the wavelength range of 400 ~ 450nm and the other part generates light in the wavelength range of 600 ~ 700nm, the holographic diffraction grating is daylight It is preferable to separate the chief and the at least two auxiliary lights so that the two auxiliary lights closest to each are located on a land 1.5 track away from the groove where the main light is irradiated on the Blu-ray disc and are irradiated to a spot which is symmetric about the spot where the main light is irradiated. .

The present invention also provides an optical disk driver apparatus comprising the above optical pickup apparatus.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In adding reference numerals to components of the following drawings, it is determined that the same components have the same reference numerals as much as possible even if displayed on different drawings, and it is determined that they may unnecessarily obscure the subject matter of the present invention. Detailed descriptions of well-known functions and configurations will be omitted.

2A and 2B show the optical separation of the conventional optical pickup and the optical separation using the holographic diffraction grating of the present invention, respectively.

2A and 2B show that the beam splitter such as a diffraction beam is directed to a direction in which light is normally incident by the incident light 201 and a beam splitter such as a diffraction beam that separates the incident light into main light and two or more auxiliary lights. The path of the two auxiliary lights 202 that are refracted and separated by the smallest angle with respect to the main light is shown.

2A and 2B respectively, two kinds of light having different wavelengths are incident on the same path (201), and in the beam splitter of FIG. 2A by the general diffraction grating 203 of the conventional optical pickup apparatus, In the beam splitter of FIG. 2B, light is separated by the holographic diffraction grating 204 of the optical pickup apparatus of the present invention, thereby forming auxiliary light 202.

2A and 2B, two kinds of light having different wavelengths incident on the beam splitters are light having a wavelength in the range of 600 to 700 nm (light used for recording and reproducing DVD, hereinafter referred to as 'DVD beam'). ) And light in the range of 400 to 450 nm (light used for recording and reproducing Blu-ray Disc, hereinafter referred to as 'BD beam').

As shown in FIG. 2A, in a beam splitter using a general diffraction grating, an angle at which auxiliary light is refracted with respect to main light (the direction in which light is incident) is differently adjusted according to the wavelength of incident light 201. The angle θ that the auxiliary light refracts with respect to the main light

The beam splitter is set to achieve the following relationship. (λ: wavelength of light, P: track pitch of optical disk)

As shown in FIG. 2A, the angle of refraction 205 with respect to the main light of the auxiliary light of the DVD beam and the angle of refraction with respect to the main light of the auxiliary light of the BD beam are set to have different values by the relationship as shown in the above equation. Therefore, different diffraction beams and different beam splitters had to be used to form auxiliary light of different wavelengths such as a DVD beam and a BD beam.

Figure 2b is a light splitting in the beam splitter of the optical pickup device of the present invention, the optical pickup device of the present invention bundles two or more light sources for generating light of different wavelengths in a single package, the light generated from the light source package Optical separation using a single beam splitter.

The beam splitter includes a holography grating, and the holography diffraction splits the incident light into the main light and the auxiliary light so that the angles of refraction of the auxiliary light with respect to the main light have different wavelengths, such as a DVD beam and a BD beam. It is designed to be the same for two or more kinds of incident light.

In FIG. 2B, the incident light 201 forms an auxiliary light having a specific angle of refraction 207 with respect to the main light by a beam splitter including the holographic diffraction beam 204 designed as described above, wherein the angle of refraction 207 of the auxiliary light is incident light. This is no different in the case of the DVD beam and the case of the BD beam.

Figure 3 shows the light source package of an embodiment of the optical pickup device of the present invention as viewed from the light emitting side.

The light source package of the optical pickup apparatus of the present invention includes two or more light sources for generating light of different wavelengths, and the light source package of FIG. 3 includes two light sources for generating a DVD beam and a BD beam, respectively.

In FIG. 3, the light source 301 of the DVD beam and the light source 302 of the BD beam are positioned on the same light source package, and the light source 301 of the DVD beam is positioned 110 mm apart from each other by different positions on the light source package.

Light generated from two or more light sources included in the light source package as shown in FIG. 3 is incident on one beam splitter and is separated by the same holographic diffraction grating. Since the subsequent optical paths vary depending on the path and position of the beam splitter and the holographic diffraction grating, the light paths are formed such that light generated from light sources having different positions of the light source package is incident on the beam splitter and the holographic diffraction grating through the same path. It is preferred that a device for matching is provided in the optical path between the light source package and the beam splitter. This will be described with reference to FIG. 4.

4 is a schematic diagram briefly showing an embodiment of the optical pickup apparatus of the present invention.

In the embodiment of Figure 4, the optical pickup device includes a light source package 401 including two or more light sources for generating light having different wavelengths, combining the light generated from the different light sources of the light source package into one light path A beam combiner (402), a beam splitter (403) for refracting light generated from different light sources in which the optical paths are combined into one in the beam combiner, and splitting the light into main light and two or more auxiliary lights; A collimator lens (404) for adjusting the chief and auxiliary light separated by the beam splitter to parallel light, and the chief and auxiliary light adjusted to the parallel light in the collimator lens on the optical disk 406 to record or read information. Condensing means 405 and light detecting means 208 for detecting the light reflected by the light collecting means on the optical disk.

In the above embodiment, the light source package 401 includes two or more light sources for generating light of different wavelengths, and the light source is preferably composed of a photodiode or the like as a conventional light source provided in the optical pickup device.

In the above embodiment, the beam combiner 402 adjusts light generated from two or more light sources included in the light source package to be incident on the beam splitter 403 in the same path. Two or more light sources of the light source package are different from each other so that the light paths generated from the light sources are different from each other. Thus, when the light splitters enter the beam splitter with different paths, subsequent light paths are different from each other. Depending on the configuration of the collimating lens, the light collecting means and the light detecting means may be necessary.

However, as described above with reference to FIG. 2B, the beam splitter is incident so that the main light is in a straight direction of the incident light, and the auxiliary light has a path having the same refractive angle with respect to the same main light even though the light is generated from different light sources. The light exits the main light and the auxiliary light in the same path. If the light source package is adjusted so that light generated from light sources having different positions is incident on the beam splitter in the same path, subsequent light paths become the same, thereby simplifying operation of components after the beam splitter. Accordingly, it is preferable that a beam combiner is provided in the optical path between the light source package and the beam splitter to adjust light generated from different light sources to be incident on the beam splitter in the same path.

The beam combiner preferably combines the light paths by adjusting the light generated from a specific light source so as to have the same path as the light generated from the specific light source without changing the path thereof.

In the above embodiment, the beam splitter is configured to separate the two or more mutually different light incident from the light source package into the main light and the two or more auxiliary lights, so that the separated angles of the auxiliary light with respect to the main light are equal to each other. Include. In the holographic diffraction grating, separation of the main light and the auxiliary light from the light sources having different wavelengths from each other at the same refractive angle is not significantly different from that described with reference to FIG. 2B.

In this embodiment, the collimating lens 404 adjusts the main light and the auxiliary light to parallel light so that the main light and the auxiliary light refracted by the beam splitter can be focused on one focal point on the optical disc by the condensing means 405 later. do.

In this embodiment, the condensing means 405 condenses the light emitted from the light source and incident on the information surface of the optical disc to write or read data on the optical disc. The light collecting means preferably includes an objective lens as the light collecting means in a conventional optical pickup apparatus.

In the above embodiment, the light detecting means 407 detects the result of the light condensed on the optical disk by the light collecting means. The light detecting means detects the light reflected from the optical disc and converts the light into an electrical signal. The optical detection means reads the data recorded on the optical disc from the result of the conversion, and also obtains an error signal for focusing or tracking servo from the detection state. . The photodetecting means is preferably composed of a photodiode for sensing light.

As described above, the splitting of the light into the main light and the two or more auxiliary lights in the beam splitter mainly uses the three-beam push pull method (differential push pull method, DPP (Differential Push Pull method)) of the method of acquiring the error signal for the tracking servo. To do that.

In the push-pull method, the light emitted from the light source is split into two or more auxiliary lights positioned before and after the main light in the optical separation means such as a diffraction grating, and the relative position of the auxiliary light with respect to the main light varies depending on the track pitch of the optical disk used. . The main light is irradiated to the groove on the optical disc, and a high level DPP signal is obtained which makes tracking servo by the push-pull method easier when the two auxiliary lights are irradiated to the land on the optical disc so as to be symmetric about the spot where the main light is irradiated.

However, in the optical pickup apparatus of the present invention, the refraction angles between the main light and the auxiliary light are the same even by light having different wavelengths by holographic diffraction included in the beam splitter. It is necessary to obtain a high level of DPP signal for easier tracking servo, for which it is preferable that two or more auxiliary lights are irradiated on a land at a position symmetrical with respect to the main light. The holographic diffraction grating of the present invention may be set such that the angle of refraction of the auxiliary light with respect to the main light varies for each type of optical disc, and it is also preferable to set a predetermined angle of refraction so that the auxiliary light is irradiated onto the land in common for several types of optical discs. .

5 is a graph showing the level of the DPP signal with respect to the distance from the track to which the main light is irradiated to the land to which the auxiliary light is irradiated in the two types of optical discs.

In the graph of Fig. 5, the level of the DPP signal with respect to the distance from the track to which the main light is irradiated to the land to which the auxiliary light is irradiated in the two optical discs of the DVD and the Blu-ray Disc (BD) is displayed. When the optical discs to which the optical pickup apparatus of the present invention is the object of the optical pickup are the DVD and the BD, it is preferable to adjust the position at which the auxiliary light is irradiated so that the DPP level has a maximum value for both the optical discs.

As shown in the graph, when the auxiliary light is irradiated on a land at a position approximately 1.115 占 퐉 away from the groove to which the main light is irradiated in the direction perpendicular to the track direction, a maximum value DPP signal can be simultaneously obtained for the DVD and the BD. The irradiation position of the auxiliary light whose maximum value is the DPP signal is a land about 3.5 tracks away from the groove to which the main light is irradiated on the BD based on the number of tracks, and about 1.5 tracks away from the groove to which the main light is irradiated on the DVD.

FIG. 6 shows a spot where primary and auxiliary light are radiated onto two types of optical discs according to an embodiment of the optical pickup apparatus of the present invention.

6 shows the light irradiated onto the Blu-ray Disc BD (601), and the lower part shows the light irradiated onto the DVD (602).

In FIG. 6, the spot 603 to which the main light is irradiated is located in the groove, the spot 604 to which the auxiliary light is irradiated is located on the land, and the spots to which the auxiliary light is irradiated on the BD and DVD are respectively symmetrical with respect to the spot to which the main light is irradiated. Exists at the location.

The relative position of the spot to which the auxiliary light is irradiated with respect to the spot to which the main light is irradiated is not different from each other in the BD and the DVD, and in the BD, two spots in which the auxiliary light is irradiated to the land 3.5 tracks away from the groove to which the main light is irradiated are located, and in the DVD, Two spots in which the auxiliary light is irradiated are located in a land 1.5 tracks away from the groove to which the main light is irradiated.

As described above, the tracking servo can be more easily performed by irradiating the auxiliary light to a position capable of maximizing the level of the DPP signal with respect to the heterogeneous optical discs at the same time.

By using one of the above light source packages and using a holographic diffraction grating, an optical pickup apparatus in which an auxiliary light is formed with the same refractive angle with respect to the main light with respect to light having different wavelengths is a device such as a conventional optical disc driver for recording and reproducing an optical disc. It may be provided as a portion for the optical pickup in.

As described above, it has been described with reference to the preferred embodiment of the present invention, but those skilled in the art various modifications and changes of the present invention without departing from the spirit and scope of the present invention described in the claims below I can understand that you can.

As described above, according to the present invention, even when performing optical pickup for optical disks using light having different wavelengths, the light source is provided in one package, and only one beam splitter for separating the light generated from the light source is provided. There is an advantage that the configuration of the pickup device is simplified.

Claims (6)

A light source package including two or more light sources generating different wavelengths; A beam splitter separating the light incident from the light source package into main light and at least two auxiliary lights; A collimating lens for adjusting the main light and the at least two auxiliary lights separated by the beam splitter into parallel lights; Condensing means for condensing the main light and the two or more auxiliary lights adjusted by the collimating lens to a specific position on the optical disk; And light detecting means for detecting that the light collected by the light collecting means is reflected from the optical disk, wherein the beam splitter separates two or more light having different wavelengths incident from the light source package into main light and two or more auxiliary lights. The optical pickup apparatus of claim 1, further comprising a holographic diffraction beam configured to have separate angles of the auxiliary light with respect to the main light. The optical pickup apparatus of claim 1, further comprising a beam combiner for adjusting light generated from two or more light sources of the light source package to be incident on the holographic diffraction beam in the same path. Optical pickup device. The method of claim 1, wherein some of the two or more light sources included in the light source package generate light in a range of 400 to 450 nm and others generate light in a range of 600 to 700 nm. Optical pickup device. 2. The holographic diffraction grating of claim 1, wherein the holographic diffraction grating is irradiated to a spot in which an auxiliary light closest to the main light is located on a land 1.115 um away from the groove to which the main light is irradiated, in a direction perpendicular to the track direction, and is symmetric about a spot to which the main light is irradiated. The optical pickup device, characterized in that to separate the main light and at least two auxiliary light. The holographic diffraction grating of claim 1, wherein some of the light sources included in the light source package generate light in a range of 400 to 450 nm, and others generate light in a range of 600 to 700 nm. Is to separate the main and two auxiliary lights so that the two auxiliary lights closest to the main light are located on a land 1.5 track away from the groove where the main light is irradiated on the Blu-ray disc and are irradiated to a spot symmetrically about the spot where the main light is irradiated. Optical pickup device characterized in that. An optical disk driver apparatus comprising the optical pickup apparatus of any one of claims 1 to 5.

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