KR20090064636A - Optical pickup device - Google Patents

Abstract

The present invention relates to an optical pickup apparatus capable of supporting both BD / HD-DVD / DVD / CD media.

An optical pickup apparatus according to an embodiment of the present invention, the first light source unit for emitting a laser light of a wavelength corresponding to the DVD / CD; A second light source unit emitting laser light of a wavelength corresponding to HD-DVD / BD; A first objective lens having a numerical aperture suitable for HD-DVD / DVD / CD; A second objective lens having a numerical aperture suitable for BD; And a prism that reflects or passes the laser light emitted from the first light source unit or the second light source unit or the laser light reflected from the optical disk.

Through the present invention, it is possible to implement an optical pickup device having a low cost and a compact size.

Description

Optical pickup device {OPTICAL PICK-UP DEVICE}

The present invention relates to an optical pickup apparatus capable of supporting both BD / HD-DVD / DVD / CD media.

As the demand for high quality video processing increases, the data storage capacity of the optical disc is also required to be large. As a result, recently, high-density rewritable optical recording media capable of recording and storing high-definition video data and high-quality audio data for a long time have been introduced.

CD is an optical storage medium for recording and / or reproducing information using an optical lens having a wavelength of 780 nm and an objective lens of 0.45 or 0.5, and a DVD having a light and numerical aperture (NA) of 650 nm. ) Is an optical storage medium for recording and / or reproducing information using an objective lens of 0.6 or 0.65.

On the other hand, as the blue laser for generating / emitting short-wavelength laser light in the wavelength range of about 400 nm becomes practical, an optical information recording medium capable of recording information at a higher density has been developed and spread.

ADO (Advanced Optical Disc), called high-definition DVD (HD-DVD), is an optical information recording medium that uses 405 nm wavelength light and uses a numerical aperture objective lens such as DVD to record and / or reproduce information. .

The HD-DVD has a higher recording density than the DVD because it uses light having a short wavelength and has an advantage over the BD in terms of compatibility of optical pickup because it uses an objective lens having a numerical aperture such as DVD.

BD is an optical information recording medium for recording and / or reproducing information using light having a wavelength of 405 nm and an objective lens having a numerical aperture of 0.85, and has a high recording capacity of about 25 GB. The BD has recently been researched and developed at various angles, and has been spotlighted as a high density optical information recording medium suitable for recording high-definition video information.

As these various kinds of high density optical information recording media are developed / developed, the optical pickup apparatus has developed into a compatible type capable of recording and / or reproducing information by making the high density optical information recording medium and the low density information recording medium compatible.

1 is a block diagram showing a configuration of a general optical disk drive.

A general optical disc drive includes an optical disc 21, which is a recording medium on which information is recorded, reproduced, and erased by a laser, a pickup unit 11 for recording / reproducing management information including data recorded on the optical disc 21; Servo unit 12 for controlling the operation of the pickup unit 11, to demodulate the reproduction signal received from the pickup unit 11 to a desired signal value or to record on the optical disc 21 as a signal to be recorded. And a signal processor 14 for modulating and transmitting a signal of a required type, a memory 15 for storing various kinds of information necessary for disc reproducing, and a microcomputer 13 for controlling the operation of the component. The recording and reproducing section 10 is configured including the above components.

The pickup 11 may include an optical lens such as an objective lens driven by a laser light source such as a laser diode, a collimator lens, a focus actuator or a tracking actuator, a polarizing beam splitter, a cylindrical lens, a photo detector for converting light into an electrical signal, Or a front monitor diode for monitoring the laser output during recording and reproduction.

The microcomputer 13 detects the reflected light from the optical disc 21, calculates the reflected light amount from the detected reflected light, and generates an RF signal representing the total sum of the reflected light amounts for each region of the photodiode. In addition, the microcomputer 13 generates a focus error signal FES, which is a signal for detecting out of focus of the laser of the pickup unit 11, by astigmatism. In addition, the microcomputer 13 generates a tracking error signal TES, which is a signal for detecting a track misalignment of the laser of the pickup unit 11, using a push-pull method or the like.

The memory 15 stores various kinds of information necessary for disc reproducing. Generally, the memory 15 includes RAM and ROM to store a control program, a theoretical length of each pit and land, or a probability of existence in a combination of each pit and land. do.

The control unit 23 is responsible for the control of the entire component.

The decoder 22 finally decodes the output data under the control of the controller 23 and provides it to the user.

The encoder 24 converts a signal input under a control of the controller 23 into a signal of a specific format, for example, an MPEG2 transport stream, in order to record data desired by a user on a recording medium. 14) to provide.

As described above, FIG. 1 includes the components of the recording and reproducing apparatus of the optical disc drive. In connection with the reproduction, the optical disc 21, the recording and reproducing section 10, and the decoder 22 are used. In this case, the recording and playback section 10 and the encoder 24 will be used under the control of the control section 23.

As described above, the optical disc 21 is a CD (Compact Disc), a DVD (Digital Versatile Disc), or an HD-DVD (According to Numerical Aperture (NA) or wavelength of light of an objective lens for focusing light). High Definition DVD), BD (Blueray Disc) and the like.

According to the type of the optical disk inserted into the optical pickup device, if the configuration of the pickup unit 11 and the like all different, there is a problem in terms of cost and inefficient.

Therefore, the necessity of an optical pickup device capable of coping with the different optical disc media has emerged, and a number of products have been released at present. However, due to the high selling price and the size of the product, the consumer has not received a favorable response.

SUMMARY OF THE INVENTION The present invention has been made to solve the above object, and an object of the present invention is to propose an optical pickup device which is economical and compact.

Another object of the present invention is to propose an optical pickup capable of simultaneously recording / reproducing BD, HD-DVD, DVD and CD, which are proposed as next-generation optical pickup devices.

In order to solve the above problems, the present invention proposes an optical pickup device.

An optical pickup apparatus according to an embodiment of the present invention, the first light source unit for emitting a laser light of a wavelength corresponding to the DVD / CD; A second light source unit emitting laser light of a wavelength corresponding to HD-DVD / BD; A first objective lens having a numerical aperture suitable for HD-DVD / DVD / CD; A second objective lens having a numerical aperture suitable for BD; And a prism that reflects or passes the laser light emitted from the first light source unit or the second light source unit or the laser light reflected from the optical disk.

Through the present invention, a compact optical fiber having a competitive price that can be employed in a DVD or HD-DVD, a next-generation optical storage media, and a conventional CD and DVD to ensure stable performance and to be adopted in a conventional DVD driver or recorder Pick-up device can be implemented.

The present invention relates to an optical pickup device capable of supporting both BD / HD-DVD / DVD / CD media.

An optical pickup apparatus according to an embodiment of the present invention, the first light source unit for emitting a laser light of a wavelength corresponding to the DVD / CD; A second light source unit emitting laser light of a wavelength corresponding to HD-DVD / BD; A first objective lens having a numerical aperture suitable for HD-DVD / DVD / CD; A second objective lens having a numerical aperture suitable for BD; And a prism that reflects or passes the laser light emitted from the first light source unit or the second light source unit or the laser light reflected from the optical disk.

Preferably, the first objective lens and the second objective lens are disposed in a radial direction, and the second objective lens is positioned at an outer circumference of the first objective lens.

Preferably, the apparatus further includes a light receiving element that receives the laser light reflected from the optical disk and converts the laser light into an electrical signal.

Preferably, the apparatus further comprises a diffraction grating for transforming the laser light into diffraction light in the form of a plurality of linearly flat light, wherein the diffraction grating is located at the front of the light receiving element.

Preferably, the apparatus further comprises a coma aberration compensating element for compensating coma aberration generated in the first objective lens or the second objective lens, wherein the coma aberration compensating element is a liquid crystal device.

The first spherical aberration compensating element or the second spherical aberration compensating element may further include a first spherical aberration compensating element positioned in the front part of the first objective lens and a second spherical aberration compensating element positioned in the front part of the second objective lens. The aberration compensation element is a collimator lens.

Preferably, the first light source unit is a 2-wavelength 1-chip laser diode for DVD / CD, and the 2-wavelength 1-chip laser diode for DVD / CD includes two light emitting points capable of oscillating laser diodes having different wavelengths. The two light emitting points are spaced 110um apart from each other.

Preferably, the prism includes a first prism positioned in front of the first objective lens to reflect or pass the laser light, and a second prism positioned in front of the second objective lens to reflect or pass the laser light; The first prism and the second prism are configured to be heterogeneous.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily understand and implement the present invention.

2 is a schematic exploded view of an optical pickup apparatus 100 according to an embodiment of the present invention.

The optical pickup apparatus 100 according to an exemplary embodiment of the present invention emits a laser beam having a wavelength corresponding to HD-DVD / BD and a first light source 111 for emitting a laser beam having a wavelength corresponding to DVD / CD. A second light source unit 112 having a numerical aperture suitable for HD-DVD / DVD / CD, a second objective lens 132 having a numerical aperture suitable for BD; And a prism 150 for reflecting or passing the laser light emitted from the first light source 111 or the second light source 112 or the laser light reflected from the optical disk.

The first and second light source units 111 and 112 detect a focus / tracking signal for recording / reproducing audio / video data on an optical disk on which a track pitch of a predetermined shape is formed or for accurately reading information data recorded at the track pitch. In order to emit laser light for the light source, the first and second light source parts 111 and 112 may include a laser diode LD.

The first light source unit 111 emits laser light having a wavelength corresponding to the DVD / CD. In general, since the DVD uses laser light having a wavelength of about 650 nm, and the CD uses laser light having a wavelength of about 780 nm, the first light source 111 may be internally configured to emit light having different wavelengths. Can be.

Preferably, the first light source 111 may include a 2-wavelength 1 chip laser diode for DVD / CD. The two-wavelength one-chip laser diode for DVD / CD will be described in detail with reference to FIG. 3.

3 is a diagram schematically illustrating a configuration of the first light source unit 111 according to an embodiment of the present invention. As described above, the first light source 111 includes two different light emitting points 113 and 114 to emit laser light having a wavelength corresponding to the DVD / CD.

For example, the laser light of 650 nm, which is a wavelength corresponding to the DVD, may be emitted from the first light emitting point 113, and the laser light of 780 nm, which is a wavelength corresponding to the CD, may be emitted from the second light emitting point 114. And vice versa, of course.

The first light source unit 111 may include a semiconductor chip (not shown) for emitting laser light having different wavelengths, and thus may have a structure in which the plurality of semiconductor chips are packaged in a hybrid shape.

In addition, the first light emitting point 113 and the second light emitting point 114 should be spaced apart by an appropriate distance (d) in order to prevent the laser light of different wavelengths from interfering with each other.

Preferably, the first light emitting point 113 and the second light emitting point 114 may be spaced apart from each other 110um, the 110um spaced distance is the most optimal distance to minimize the size of the component without interference phenomenon to be.

As described above, by providing an optical system capable of emitting two wavelengths, it is possible to minimize the space of components occupied by the optical device, thereby facilitating miniaturization of the product, and significantly reducing the price of the product by reducing the number of components. have.

Returning to FIG. 2, the first and second objective lenses 131 and 132 condense incident diffracted light onto a track pitch of an optical disc storing predetermined image and audio data information.

As described above, the first objective lens 131 performs a condensing role for HD-DVD / DVD / CD media, and the second objective lens 132 performs a condensing role for BD media.

Since the first objective lens 131 collects HD-DVD, DVD, or CD media, the first objective lens 131 has a structure in which the curvature may be variably changed in order to collect the different optical disc media.

The light receiving element 120 detects a tracking / focusing error signal (TES / FES) for an optical disc by performing calculation on the light distribution of the light spot formed by the diffracted light incident through the optical means. 120 includes a first light receiving element 121 corresponding to HD-DVD / DVD / CD and a second light receiving element 122 corresponding to BD.

The prism 150 serves to reflect or pass the laser light emitted from the first light source unit 111 or the second light source unit 112 or the laser light reflected from the optical disk, and the prism 150 is the A first prism 151 positioned in front of the first objective lens 131 for reflecting or transmitting the laser light and a second prism positioned in front of the second objective lens 132 for reflecting or transmitting the laser light ( 152).

In addition, as shown in FIG. 2, the first prism 151 and the second prism 152 may be configured as a release unit.

Hereinafter, an operation of the optical pickup apparatus 100 according to an embodiment of the present invention will be described.

The light of the CD wavelength (780 nm) or the light of the DVD wavelength (650 nm) emitted from one of the two light emitting points 113 and 114 included in the first light source 111 is directed to the incident light in a predetermined direction. It is reflected by the beam splitter 161 which diverges, and is reflected at a right angle by the predetermined mirror 162 and guided through the first prism 151.

Here, the prism 151 may pass through a diffraction grating (not shown), which will be described in detail with reference to FIG. 4.

The laser beam passing through the first prism 151 has a form of a linearly polarized diffraction beam having a predetermined diffraction coefficient. The laser beam is converted into a parallel diffraction beam by a first collimator lens 141, and the wavelength plate The diffraction beam in the form of parallel light having a predetermined diffraction coefficient incident in parallel by the first collimator lens 141 into the circular diffraction beam, and enter the first objective lens 131. Let's do it.

Next, the first objective lens 131 records the light spots present on the respective optical disks, and the reflected light is recorded in the first objective lens 131, the first collimator lens 141, the mirror 162, The first light receiving element 121 is finally reached via the beam splitter 161 and the like.

The first light receiving element 121 detects a tracking / focusing error signal (TES / FES) for the optical disk by performing calculation on the light distribution of the light spot formed by the diffracted light incident through the optical means.

A detailed description of the calculation of the light spot distribution of the light receiving device 120 or the method of detecting the tracking / focusing error signal (TES / FES) will be omitted.

The light of the HD-DVD / BD wavelength (405 nm) emitted from the second light source unit 112 reflects the HD-DVD light and passes the BD light in the second prism 152. Therefore, the HD-DVD light is focused on the disc through the first objective lens 131 by the first prism 151 toward the first prism 151 and passes through the same path as described above. The laser beam reaches 121.

The BD light passes through the second prism 152, and the laser light passing through the second prism 152 has a form of a linearly polarized diffraction beam having a predetermined diffraction coefficient, which is parallel by the second collimator lens 142. A diffracted beam in the form of a circular light from a diffracted beam in the form of a parallel light having a predetermined diffraction coefficient which is converted into an optical diffraction beam and is incident in parallel by the second collimator lens 142 by a wave plate (not shown). Is converted into the second objective lens 132.

Next, the second objective lens 132 records the light spots present in the respective optical disks, and the reflected light passes through the second objective lens 132 and the second collimator lens 142 and the second prism. Reflected at 152 finally reaches the second light receiving element 122.

The second light receiving element 122 detects a tracking / focusing error signal (TES / FES) for the optical disk by performing calculation on the light distribution of the light spot formed by the diffracted light incident through the optical means.

The configuration and principle of the first prism 151 and the second prism 152 will be described with reference to FIGS. 4A and 4B.

4A and 4B are schematic diagrams for briefly explaining a configuration of the second prism 152.

The second prism 152 may replace the conventional expensive polarization conversion element by using a single laser diode to correspond to the BD and the HD-DVD through the PS coating. As shown in FIGS. 4A and 4B, the use of the PS coating in the second prism 152 transmits the P fine BD laser light and reflects the S fine HD-DVD laser light.

In addition, the BD laser light passes through a wave plate (Quarter Wave Plate (QWP) once in the incident path, once in the reflection path, and twice in total, whereby the P wave is transformed into an S wave, reflected by the optical disk, and again, the second prism ( When reaching 152, it is reflected by the second prism 152 and finally reaches the second light receiving element 122.

As shown in FIG. 4B, the second prism 152 performs PS coating to separately reflect or transmit P waves and S waves with respect to laser light having a wavelength of 405 nm.

Accordingly, the paths of the HD-DVD laser light and the BD light emitted from the second light source unit 112 may be separated by the second prism 152 to finally reach different paths and different light receiving elements 121 and 122. To induce.

5 is an exemplary view illustrating an arrangement example of the first and second objective lenses 131 and 132 included in the optical pickup apparatus 100 according to an exemplary embodiment of the present invention.

As shown in FIG. 5, the first objective lens 131 and the second objective lens 132 are disposed in the radial direction of the optical disc 200. Preferably, the second objective lens 132 is formed of the first objective lens 132. It may be positioned on the outer circumference of the objective lens 131.

As shown in Fig. 5, by arranging the objective lens 130 in the radial direction on the same line in the radial direction of the optical disc 200, the recording / reproducing operation of data for different wavelengths can be made more efficient. Make sure

6A and 6B are exemplary views comparing the conventional scheme (FIG. 6A) to the position of the diffraction grating 171 with the scheme (FIG. 6B) according to the embodiment of the present invention.

The diffraction grating 171 diffracts the incident laser light to form a diffraction beam in the form of a linear flat light having a predetermined diffraction coefficient, specifically, a diffraction coefficient of 0th order, + 1st order, and -1st order. do.

As shown in FIG. 6A, the conventional method has a problem in that the tracking servo of the optical disc 200 cannot be performed accurately because the diffraction grating 171 is positioned on a common path of the transmitter and the receiver.

However, as shown in FIG. 6B, the optical pickup apparatus according to the exemplary embodiment of the present invention places an optical disc to form a diffraction beam having a diffraction coefficient of ± 1 order by placing the diffraction grating 171 in a light receiving unit alone path. It is not necessary to diffract before reaching 200 so that the tracking servo of the optical disc 200 can be more accurately performed.

In addition, by disposing the diffraction grating 171 differently from the conventional method, it is possible to effectively remove the noise caused by the dual layer.

FIG. 7 is an exemplary view for explaining a process of enhancing a radiation angle through an adjusting process of the prism 150, the mirror 162, and the light source unit 110 of the optical pickup apparatus according to an exemplary embodiment.

In order to realize a compact pickup device by minimizing the size of the optical pickup device, an optical component such as a prism or a mirror may be used as a method of closely contacting elements to a mounting surface of an injection-molded base without additional processing as in the conventional method. There is too much to assemble.

Thus, as shown in FIG. 7, the optical component such as the prism 150, the mirror 162, the laser diode 110, or the objective lens 130 may be rotated up, down, left, or right in various degrees of freedom. After the adjustment is performed, an assembly process is performed after checking the position and the radiation angle of the prism 150 or the mirror 162.

After the adjustment process and the X and Y axis adjustment of the laser diode, each optical path can be assembled without distortion of the radiation angle.

In addition, various errors may occur when data is recorded and reproduced. Aberrations that may occur in the optical pickup device typically include coma or spherical aberration.

The coma abberation is an aberration caused by a mismatch between an image generated by a laser beam passing through a central portion and a peripheral portion of the lens. When the coma aberration occurs, the quality of an image of a peripheral portion is deteriorated.

8A and 8B illustrate a first embodiment for compensating for coma aberration generated in an optical pickup apparatus according to an embodiment of the present invention.

When assembling the first objective lens 131, which is the objective lens for HD-DVD / DVD / CD, and the second objective lens 132, which is the objective lens for BD, located in the actuator, one of the two lenses is first assembled and In consideration of the coma aberration characteristics of the assembled objective lens, the remaining objective lenses are assembled as shown in FIG. 8A to have the same coma aberration characteristics.

Since the optical path of the optical component assembled to the pre-assembled optical pick-up base 181 is ideally adjusted by the laser diode / mirror / prism, the optical path is present in the optical pick-up base 181 as described above. Independently of the optical system, if the actuators with two objective lenses are independently assembled so that the coma aberration characteristics are the same, one of the different optical systems is selected, and the optical system of the other optical system is adjusted to minimize the coma aberration of the optical system. Also, as shown in FIG. 8B, the coma aberration may be adjusted to the minimum without shifting the optical axis between the optical system existing in the optical pickup base 181 and the objective lens of the actuator.

9A and 9B are diagrams illustrating a second exemplary embodiment for compensating for coma aberration generated in the optical pickup apparatus according to the exemplary embodiment of the present invention.

The optical pickup apparatus according to the present invention may include a coma aberration compensating element for compensating coma aberration generated in the objective lens, and the coma aberration compensating element may be a liquid crystal device.

In order to secure a tolerance, the optical pickup apparatus according to the embodiment of the present invention may include two coma aberration compensating elements, and the two coma aberration compensating elements are respectively located at the front of each objective lens. It is desirable to.

9A schematically illustrates a coma aberration occurring in the optical pickup apparatus in a graph form. As shown in FIG. 9A, the coma aberration generated in the optical pickup device may be locally distributed differently.

By adding or subtracting coma aberration by the amount corresponding to the rectangles 191 of FIG. 9A, the absolute amount of coma aberration generated in the optical pickup apparatus as shown in FIG. 9B can be greatly reduced. have.

FIG. 10 schematically illustrates an apparatus configuration for compensating spherical aberration generated in the optical pickup device according to an embodiment of the present invention.

The spherical abberation is an aberration inevitably designed by the surface of a mirror or a lens artificially, and the rays incident in parallel at adjacent portions of the optical axis are different at one point, but are incident far away from the optical axis. The light rays do not form an image at one point and generate an error, which is called spherical aberration.

In the optical pickup apparatus according to an embodiment of the present invention, the spherical aberration can be compensated for all the media by driving the collimator lens. Each optical disc has layers at different positions depending on the type thereof, and a single disc may have a plurality of layers.

Such spherical aberration can be compensated by appropriately driving the collimator lens 140 as shown in FIG. 10, and configured to drive the first collimator lens 141 and the second collimator lens 142, respectively. Can be.

In addition, the optical pickup device according to an embodiment of the present invention uses a LDD (Laser Diode Device) without using a monitor PDIC (MPD) for DVD / CD.

That is, unlike the related art, when used in an APC using I / V Amp embedded in the LDD and a light receiving element embedded in the LD itself, the number of parts required for the device can be reduced without using an external front monitor light receiving element. In addition, it is possible to implement a miniaturization spatially to enable a thin product.

In addition, in order to prevent the heat source of the LDD from affecting the optical pickup apparatus and deteriorating aberration characteristics, it is preferable to design a predetermined interval between the main PCB and the pickup base to increase the thermal resistance to the heat source of the LDD.

So far, the present invention has been described with reference to preferred embodiments thereof, and a person of ordinary skill 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 scope should be interpreted as being included in the present invention.

1 is a block diagram showing a configuration of a general optical disk drive.

2 is a schematic exploded view showing an optical pickup apparatus according to an embodiment of the present invention.

3 is a view schematically showing a configuration of a first light source unit according to an embodiment of the present invention.

4A and 4B are schematic diagrams for briefly explaining a configuration for the second prism.

5 is an exemplary view showing an arrangement example of first and second objective lenses included in an optical pickup apparatus according to an exemplary embodiment of the present invention.

6A and 6B are exemplary views showing a comparison between a conventional method and a method according to an embodiment of the present invention with respect to the position of a diffraction grating.

FIG. 7 is an exemplary view for explaining a process of increasing a radiation angle through an adjusting process of a prism, a mirror, and a light source unit of the optical pickup apparatus according to an embodiment of the present invention; FIG.

8A and 8B illustrate a first embodiment for compensating for coma aberration occurring in an optical pickup apparatus according to an embodiment of the present invention.

9A and 9B illustrate a second embodiment for compensating for coma aberration occurring in the optical pickup apparatus according to an embodiment of the present invention.

FIG. 10 is a schematic block diagram of an apparatus for compensating spherical aberration generated in the optical pickup apparatus according to the exemplary embodiment of the present invention. FIG.

      ※ Description of the main parts of the drawings ※

100: optical pickup device 200: optical disk

111: first light source unit 112: second light source unit

113: first light emitting point 114: second light emitting point

121: first light receiving element 122: second light receiving element

131: first objective lens 132: second objective lens

141: first collimator lens 142: second collimator lens

151: first prism 152: second prism

161: beam splitter 162: mirror

171: diffraction grating 181: optical pickup base

Claims (15)

A first light source unit emitting laser light of a wavelength corresponding to the DVD / CD; A second light source unit emitting laser light of a wavelength corresponding to HD-DVD / BD; A first objective lens having a numerical aperture suitable for HD-DVD / DVD / CD; A second objective lens having a numerical aperture suitable for BD; And And a prism for reflecting or passing the laser light emitted from the first light source or the second light source or the laser light reflected from the optical disk. The method of claim 1, And the first objective lens and the second objective lens are arranged in a radial direction. The method of claim 2, And the second objective lens is positioned at an outer circumference of the first objective lens. The method of claim 1, And a light receiving element which receives the laser light reflected from the optical disk and converts the laser light into an electrical signal. The method according to claim 1 or 4, And a diffraction grating for transforming the laser light into a plurality of linearly diffracted diffraction light. The method of claim 5, And the diffraction grating is positioned at a front side of the light receiving element. The method of claim 1, And a coma aberration compensating element for compensating coma aberration generated in the first objective lens or the second objective lens. The method of claim 7, wherein And said coma aberration compensating element is a liquid crystal element. The method of claim 1, A first spherical aberration compensating element positioned in the front part of the first objective lens; And And a second spherical aberration compensating element positioned in the front part of the second objective lens. The method of claim 9, And the first spherical aberration compensating element or the second spherical aberration compensating element is a collimator lens. The method of claim 1, And the first light source unit comprises a 2-wavelength 1 chip laser diode for a DVD / CD. The method of claim 11, The two-wavelength one-chip laser diode for the DVD / CD is characterized in that it comprises two light emitting points capable of oscillating laser diodes of different wavelengths. The method of claim 12, The two light emitting points are optical pickup device, characterized in that spaced apart from each other 110um. The method of claim 1, The prism is, A first prism positioned in front of the first objective lens to reflect or pass a laser beam; And And a second prism positioned in front of the second objective lens to reflect or pass the laser light. The method of claim 14, And the first prism and the second prism are integrally formed with a heterogeneous body.

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