KR100480613B1 - Optical pickup having twin laser - Google Patents

Abstract

The first and second semiconductor lasers emitting the first and second light having different wavelengths are focused on the recording medium by focusing the light emitted from the twin laser having the optical module structure onto the recording medium. Disclosed are an optical pickup configured to receive and detect reflected light by a photodetector.

The disclosed optical pickup includes a first plated beamsplitter such that a distance between the optical paths of the first and second light beams is wider than when emitted from a twin laser, and first and second lights spread by the first plated beamsplitter. The second plate-type beam splitter allows the gap between the optical paths to be narrowed again, so that the optical path difference between the first and second light beams due to the difference in the light emission points of the first and second semiconductor lasers can be corrected. It features.

Description

Optical pickup having twin laser

The present invention relates to an optical pickup having two semiconductor laser pairs, a twin laser (TWIN LD).

The twin laser is, for example, a light source module in which two semiconductor lasers, each emitting light of a wavelength suitable for a DVD and a CD, are packaged in a single package.

When the twin laser is used as a light source for DVD and CD compatible optical pickup, there are various advantages such as simplifying the structure of the compatible optical pickup.

In addition, even if the development of high-density optical information storage media using light in the blue-violet wavelength region will continue to develop, existing DVDs and CDs will continue to be marketed. Having three semiconductor lasers, which are parts of, is very disadvantageous in construction, so the use of twin lasers will be essential.

However, a problem in using twin lasers is that the light emitting points of the semiconductor laser for DVD and the semiconductor laser for CD are different, as shown in FIG.

Referring to FIG. 1, DVD and CD emitting first and second lights 3a and 5a of a wavelength suitable for recording and / or playing DVDs 1a and CDs 1b in the twin laser 2, respectively. Since the distance between the semiconductor laser chips 3 and 5 chips is about 100 to 200 µm, the optical path of the first light 3a emitted from the DVD semiconductor laser 3, that is, the first light 3a is separated. And the optical path of the second light 5a emitted from the CD semiconductor laser 5, that is, the optical axis of the second light 5a, are shifted from each other.

Accordingly, in this state, the first and second lights 3a and 5a enter the collimating lens 7, and the optical axis c of the optical system is one of the first and second lights 3a and 5a. When it is made to coincide with the optical path of the light, the other one of the first and second lights 3a and 5a is incident on the objective lens 9 at a non-axis, and the first and second lights 3a and 5a are applied. The field angles of cannot match each other. Here, the field angle is an angle at which the traveling light is made with respect to the optical axis c of the optical system and corresponds to the angle at which the light is incident on the objective lens 9.

As shown in FIG. 1, when the twin laser 2 is arranged so that the optical path of the first light 3a coincides with the optical axis c of the optical system, it is emitted from the non-axis semiconductor CD laser 5 and collimated. The second light 5a changed into parallel light by the lens 7 is incident on the objective lens 9 at a predetermined field angle.

As such, if the optical paths of the two light beams emitted by the twin laser are misaligned with each other, a field angle problem arises, thereby causing optical offset between the objective lens and the optical disk for light emitted from the non-axis light source and incidentally on the objective lens. And shift occurs. In addition, coma aberration occurs after the objective lens passes through the light incident on the off-axis.

That is, when the twin laser is provided as a light source, various problems such as field angles, optical aberrations, and positional differences of light spots formed on the photodetector occur due to differences in emission points of the two semiconductor lasers.

The present invention has been made to improve the problems caused by the difference between the light emitting point of the two semiconductor laser when applying the twin laser as a light source, and provides an optical pickup that can correct the difference in the optical path of the two light emitted from the twin laser Its purpose is to.

In order to achieve the above object, the present invention, in the optical pickup to focus the light emitted from the twin laser to the objective lens to irradiate the recording medium, and to receive the light reflected from the recording surface of the recording medium by detecting with a photodetector, The twin laser has a structure in which first and second semiconductor lasers emitting first and second light having different wavelengths are optically modulated, and an interval between optical paths of the first and second light is emitted from the twin laser. A first plate-type beam splitter which is wider than when it is formed; A second plate-type beam splitter for narrowing the distance between the optical paths of the first and second light beams generated by the first plate-type beam splitter, and having a difference in emission points of the first and second semiconductor lasers. It is characterized in that it is possible to correct the optical path difference between the first and second light.

The first plate type beam splitter may include a first surface reflecting first light incident from the twin laser and transmitting a second light, and a second light incident therein through the first surface toward the first surface. And a second surface for reflecting, wherein the second plate-type beam splitter faces the first surface of the first plate-type beam splitter, and transmits the first light and reflects and transmits the second light. And a fourth surface for reflecting and transmitting the first light and transmitting the second light.

Here, each of the first and second plate-type beam splitters may have a structure in which two surfaces that are involved in reflection and / or transmission of light are parallel to each other.

In addition, each of the first and second plate type beam splitters may have a wedge type structure.

At this time, it is preferable that the outer surfaces of the first and second plate-type beam splitters that do not face each other become wedge surfaces.

On the other hand, a beam shaping prism for beam shaping the first and / or second light emitted from the twin laser; and an optical lens positioned between the twin laser and the beam shaping prism.

Here, the first and second light emitted from the twin laser is incident on the first and second plate-type beam splitter in the form of divergent light, and the optical lens and the beam shaping prism are the second plate-type beam splitter and the objective lens. And the optical lens to be incident on the beam shaping prism in the form of light that converges or diverges the first and second lights so that astigmatism can occur by the beam shaping prism. The prism may be provided to correct astigmatism generated in the first and second light in the form of divergent light by the first and / or second plate type beam splitter.

More specifically, the beam shaping prism may include a first surface on which light is incident from the second plate type beam splitter, a second surface reflecting light beams incident through the first surface, and the second surface. And a third surface reflecting the incident light reflected by the light toward the second surface so that the light is emitted through the second surface. The first to third surfaces may have a triangular structure. .

Meanwhile, the optical pickup according to the present invention is a collimating lens for converting the first and / or second light emitted in the form of divergent light from the twin laser into parallel light between the twin laser and the first plate-type beam splitter. It may further comprise;

On the other hand, in the optical pickup according to the present invention, any one of the first and the second light is a light having a wavelength suitable for recording and / or playing a DVD-based optical disc, and the other one records and / or plays a CD-based optical disc. It is an optical having a suitable wavelength, and at least part of the DVD-based optical disc and at least a part of the CD-based optical disc may be compatible.

The optical pickup according to the present invention further includes a single light source for emitting the third light, wherein any one of the first to third lights has a light having a wavelength suitable for recording and / or playing a DVD-based optical disc. One is light of a wavelength suitable for recording and / or playing a CD-based optical disc, and the other is light of a blue-violet wavelength region suitable for a high-density optical disc having a larger recording capacity than a DVD-based optical disc, and at least a part of the DVD-based optical disc, At least some of the CD-based optical discs and the high-density optical disc may be compatible.

In this case, the single light source is preferably arranged such that the third light emitted therefrom passes through the first plate-type beam splitter and is reflected by the second plate-type beam splitter to travel toward the recording medium.

The photodetector is preferably arranged to receive first and second light or first to third light reflected from the recording surface of the recording medium and transmitted through the second plate-type beam splitter.

Hereinafter, preferred embodiments of an optical pickup having a twin laser according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a perspective view schematically showing an optical pickup having a twin laser according to a first embodiment of the present invention, and FIG. 3 is a plan view schematically showing a main part of FIG.

Referring to the drawings, the optical pickup according to the first embodiment of the present invention, the twin laser (11) having the first and second semiconductor lasers (13, 15), and the incident light to focus the optical information storage For correcting the optical path difference due to the difference in the light emission point of the objective lens 37 for irradiating the optical disk 10 as a medium and the first and second semiconductor lasers 13 and 15 of the twin laser 11 And first and second plate type beam splitters 20 and 25, and a photo detector 19 for receiving information reflected from the recording surface of the optical disc 10 to detect information signals and / or error signals. . Here, reference numeral 18 denotes a detection lens. The detection lens 18 allows the light spot received by the photodetector 19 to be of an appropriate size. The detection lens 18 is provided with an astigmatism lens for generating astigmatism in the light directed to the photodetector 19, so as to assist in detecting the focus error signal by the astigmatism method.

The twin laser 11 has a structure in which the first and second semiconductor lasers 13 and 15 that emit the first and second light 13a and 15a having different wavelengths are optically modulated. Since the intervals between the light emitting points of the first and second semiconductor lasers 13 and 15 do not coincide with each other, for example, about 100 to 200 μm, the first and second lights 13a emitted from the twin lasers 11. The optical path of 15a, that is, the first and second light 13a and 15a are spaced apart.

The twin laser 11 may be provided such that the first and second semiconductor lasers 13 and 15 emit light having a wavelength suitable for CD and DVD. That is, either one of the first and second lights 13a and 15a is light of a suitable wavelength for recording and / or playing a DVD-based optical disc, and the other is used for recording and / or playing a CD-based optical disc. The twin laser 11 can be provided to be light of a suitable wavelength. In this case, the optical pickup according to the first embodiment of the present invention may employ at least a portion of the DVD-based optical disc and at least a portion of the CD-based optical disc.

Here, the wavelength characteristic of the twin laser 11 in the optical pickup according to the present invention is not limited to a generally known twin laser having two semiconductor lasers that emit light of different wavelengths suitable for CD and DVD. The wavelength characteristics of the two semiconductor lasers of the twin laser 11 in the invention can be variously modified. For example, an optical pickup according to the present invention is a high-density optical disc, which is recorded and / or reproduced using at least a portion of a DVD-based optical disc and a blue violet wavelength region having a storage capacity larger than that of a DVD, for example, light having a wavelength of 405 nm. When at least some of the DVD-based optical discs can be interchangeably employed, the twin laser 11 is composed of a DVD and two semiconductor lasers that emit light of different wavelengths suitable for the high density optical disc.

The first plated beam splitter 20 allows the distance between the optical paths of the first and second lights 13a and 15a to be wider than when it is emitted from the twin laser 11, and the second plated beam The splitter 25 again narrows the gap between the optical paths of the first and second light 13a and 15a so that the optical paths of the first and second light 13a and 15a coincide.

More specifically, in the present embodiment, the first plate-type beam splitter 20 reflects the first light 13a incident from the twin laser 11 and transmits the second light 15a. 20a and a second surface 20b reflecting the second light 15a incident therethrough through the first surface 20a toward the first surface 20a, as shown in FIG. 3. As described above, the first and second surfaces 20a and 20b, that is, two surfaces in which light is involved in reflection and / or transmission, have a structure parallel to each other.

The first plate-type beam splitter 20 is inclined, for example, about 45 degrees with respect to the optical axes of the first and second light 13a and 15a incident from the twin laser 11. Here, the second surface 20b may be provided to reflect the second light 15a and transmit the first light 13a.

Since the wavelengths of the first and second light 13a and 15a are different from each other, the transmittance and reflectance of the first and second surfaces 20a and 20b of the first plate-type beam splitter 20 are changed according to the wavelength. If the coating is different, the first and second light 13a and 15a may be selectively reflected and / or transmitted as described above.

The first light 13a of the first and second lights 13a and 15a incident on the first plate-type beam splitter 20 from the twin laser 11 side is reflected by the first surface 20a and is thus the second plate. Proceeding toward the beam splitter 25, the second light 15a refracts through the first surface 20a. The second light 15a incident on the first plate-type beam splitter 20 by refracting through the first surface 20a is reflected from the second surface 20b and directed toward the first surface 20a and the first surface 20a. The second plate type in a state where the light path is parallel to the first light 13a and is separated from the light path of the first light 13a than when the light path is emitted from the twin laser 11. Proceed toward the beam splitter 25.

Accordingly, the first plated beam splitter 20 may allow a distance between the optical paths of the first and second lights 13a and 15a to be wider than when the twin laser beam 11 emits the light.

The second plate-type beam splitter 25 allows the distance between the optical paths of the first and second lights 13a and 15a to be opened by the first plate-type beam splitter 20 to be narrowed again, preferably. The optical paths of the first and second lights 13a and 15a, that is, the optical axes of the first and second lights 13a and 15a are coincident with each other.

To this end, the second plate-type beam splitter 25 acts opposite to the first plate-type beam splitter 20 with respect to the first and second lights 13a and 15a having different wavelengths, and has an appropriate thickness. It is formed to have. In this case, the second plate-type beam splitter 25 may be configured to transmit the first and second lights 13a and 15a that are reflected and returned from the recording surface of the optical disc 10. In this case, as shown in FIG. 2, the photodetector 19 may be arranged to receive light reflected from the recording surface of the optical disc 10 and transmitted through the second plate-type beam splitter 25.

More specifically, in the present embodiment, the second plate-type beam splitter 25 is opposite to the third surface 25a facing the first surface 20a of the first plate-type beam splitter 20, and vice versa. The fourth surface 25b of the third surface 25a transmits the first light 13a and the second light beam so as to perform the opposite operation to that of the first plate-type beam splitter 20. It is preferable to reflect and transmit 15a), and the fourth surface 25b is provided to reflect and transmit the first light 13a and to transmit the second light 15a. At this time, the second plate-type beam splitter 25, as can be seen in Figure 3, the third and fourth surfaces (25a, 25b), that is, two surfaces involved in the reflection and / or transmission of light is parallel to each other It is a structure.

As described above, the third and fourth surfaces 25a and 25b are formed to selectively transmit and / or reflect the first and second lights 13a and 15a in the second plate-type beam splitter 25. When the thickness of the second plate-type beam splitter 25, that is, the interval between the third and fourth surfaces 25a and 25b is well adjusted, the light of the first and second lights 13a and 15a may be adjusted. By narrowing the path spacing, the optical paths of the first and second lights 13a and 15a can be matched, and the first and second lights 13a and 15a that are reflected back from the recording surface of the optical disc 10 and then come back and are incident. ) May be transmitted through the second plate-type beam splitter 25 to be received by the photodetector 19.

Since the wavelengths of the first and second lights 13a and 15a are different from each other, as in the case of the first plated beam splitter 20, the second plated beam splitter 25 also has the third and fourth surfaces 25a. When the 25b is coated in such a manner that the transmittance and the reflectance are changed according to the wavelength, the first and second lights 13a and 15a may be selectively reflected and / or transmitted as described above.

That is, the second light 15a of the first and second lights 13a and 15a incident from the first plate-type beam splitter 20 toward the second plate-type beam splitter 25 is the third surface 25a. The light is reflected by the light toward the objective lens 37, and the first light 13a refracts through the third surface 25a. The first light 13a that is refracted through the third surface 25a and incident into the second plate-type beam splitter 25 is reflected by the fourth surface 25b to face the third surface 25a and is directed to the third surface 25a. The objective lens 37 is refracted and passed through 25a again to be parallel to the second light 15a and closer to the light path of the second light 15a than when the light path is emitted from the twin laser 11. Proceed to). At this time, when the second plate-type beam splitter 25 is formed to have an appropriate thickness, the first and second lights 13a and 15a are matched in their optical paths and proceed toward the objective lens 37.

Accordingly, the second plate-type beam splitter 25 narrows the distance between the optical paths of the first and second lights 13a and 15a more than when it is emitted from the twin laser 11, The optical paths of the first and second lights 13a and 15a can be matched.

At this time, since the distance between the optical paths of the first and second light 13a and 15a is widened by the first plate-type beam splitter 20 as described above, the first and second light 13a and 15a. The second plate-type beam splitter 25 for matching the optical path of the can be formed to a thickness that can be manufactured and mass produced.

For example, when the optical path spacing between the light emitted from the twin laser 11 is 150 μm, one plate-shaped beam splitter is used to match the optical paths of the two light emitted from the twin laser 11. For example, a plate-shaped beam splitter having a thickness of about 200 μm is required. However, it is difficult to mass-produce a plate-type beam splitter having a thin thickness as described above and applicable to optical pickup, and thus, a single plate-type beam splitter is used to match two optical paths. Optical pickup is difficult to realize.

However, as in the present invention, the interval between the optical paths of the first and second light 13a and 15a emitted from the twin laser 11 using two plate-shaped beam splitters 20 and 25. In the structure in which the gaps between the light paths of these light 13a and 15a are narrowed again to match the light paths, it is possible to manufacture and mass-produce the required plate-shaped beam splitter.

According to the inventor's confirmation, for example, when the thickness of the first plate-type beam splitter 20 is approximately 1.1 mm and the thickness of the second plate-type beam splitter 25 is approximately 0.7 mm, the first And the optical paths of the second lights 13a and 15a. At this time, since the plate-shaped beam splitter having a thickness of about 1.1 mm or 0.7 mm can be manufactured and mass produced, the optical pickup according to the present invention can be realized.

On the other hand, the optical pickup according to the present invention further comprises a single light source 17 which emits a third light 17a having a wavelength different from that of the first and second lights 13a and 15a. At least some of the DVD-based optical discs and at least some of the high-density optical discs 10 and HD-DVD-based optical discs having a recording capacity larger than that of the DVD may be adopted.

When the twin laser 11 is adapted to emit the first and second light 13a, 15a of a wavelength suitable for DVD and CD, the single light source 17 is a blue violet wavelength suitable for the high density optical disk 10. For example, the semiconductor laser may emit a third light 17a having a wavelength of 405 nm.

2 and 3 are examples in which the single light source 17 is arranged such that the third light 17a emitted therefrom passes through the first plate-type beam splitter 20 and moves toward the second plate-type beam splitter 25. Shows. If the single light source 17 is arranged as shown in Figs. 2 and 3 so that the third light 17a is directed toward the optical disc 10 via the first and second plate-type beam splitters 20 and 25, In addition, there is an advantage that a separate optical path changing device for converting the traveling path of the third light 17a may not be provided.

In this case, the first and second surfaces 20a and 20b of the first plated beam splitter 20 may be in addition to the selective reflection and / or transmission characteristics of the first and second lights 13a and 15a. It is preferable that it is provided so that the 3rd light 17a may be transmitted. In addition, the third surface 25a of the second plate type beam splitter 25 is provided to reflect and transmit the third light 17a at an appropriate ratio, and the fourth surface 25b is formed of the third light ( 17a), which transmits the third light 17a reflected from the recording surface of the optical disc 10 and transmitted through the second plate type beam splitter 25 to receive the information signal when the high density optical disc 10 is employed. It is preferred that the photodetector 19 be used to detect error signals.

Here, the third surface 25a of the second plate-type beam splitter 25 has a third light 17a in addition to the selective reflection and / or transmission characteristics for the first and second lights 13a and 15a. It is also possible to reflect all, and a structure having a separate photo detector 19 for detecting the information signal and / or error signal for the high-density optical disk 10 is also possible.

On the other hand, the optical pickup according to the first embodiment of the present invention, the first and second light 13a emitted from the twin laser 11 via the first and second plate-type beam splitters 20 and 25. It is preferable to further include a beam shaping prism 35 for beam shaping 15a and an optical lens 31 positioned between the second plate-shaped beam splitter 25 and the beam shaping prism 35.

As is well known, when divergent light passes through a plate-shaped beam splitter disposed obliquely to an optical path, astigmatism occurs in the divergent light transmitted therethrough.

In the first embodiment of the present invention, the second light 15a passes through the first plate type beam splitter 20 twice, and the first light 13a passes through the second plate type beam splitter 25. Since the first and second lights 13a and 15a which are transmitted twice and are incident on the first and / or second plate-type beam splitter 25 are divergent light, the first and second light pick-ups in the optical pickup according to the present invention are used. Astigmatism may appear approximately twice as large in the first and second beams 13a and 15a via the second plate-type beam splitter 20 and 25 as compared to a structure that transmits the plate-type beam splitter once. .

Therefore, in the optical pickup according to the present invention, the beam shaping prism 35 and the optical lens 31 indicate that astigmatism is caused by the beam shaping prism when the light converging or diverging is incident on the beam shaping prism. Inversely, the astigmatism generated in the first and second light beams 13a and 15a by the first and / or second plate-type beam splitters 20 and 25 can be canceled and corrected. It is preferred to be constructed and arranged.

That is, in order to intentionally generate an astigmatism in the beam shaping prism 35, the first and second light 13a of the divergent light type in which the optical lens 31 is incident from the second plate type beam splitter 25 side. Arranged to change the light 15a to slightly converging or diverging light so that the first and second lights 13a and 15a are incident on the beam shaping prism 35 in the form of converging or diverging light, and the beam shaping prism Reference numeral 35 denotes the first and / or second plate-type beam splitters 20 and 25 to offset and correct astigmatism generated in the first and second lights 13a and 15a. It is preferable to be configured to generate astigmatism in the second lights 13a and 15a.

For example, as shown in FIGS. 4 and 5, the beam shaping prism 35 may include a first surface 35a through which light is incident from the second plate-type beam splitter 25, and a first surface ( The second surface 35b reflects light incident to the inside through 35a and emits light toward the objective lens 37, and the light reflected from the second surface 35b and incident to the second surface 35b. It is provided with a third surface (35c) for reflecting toward the 35b) to be emitted through the second surface (35b), the first to third surfaces (35a, 35b, 35c) has a triangular structure.

In this case, it is preferable that the first surface 35a of the beam shaping prism 35 is inclined with respect to the incident first and second light 13a and 15a. The third surface 35c of the beam shaping prism 35 may be disposed in parallel with the traveling paths of the first and second lights 13a and 15a.

When the first and second lights 13a and 15a are incident on the beam shaping prism 35 having the above-described structure from the second plate-type beam splitter 25, the first and second lights 13a ( 15a is refracted through the first surface 35a to be incident on the second surface 35b, and is reflected from the second surface 35b to face the third surface 35c. The first and second light 13a and 15a are reflected from the third surface 35c toward the second surface 35b and refracted through the second surface 35b toward the objective lens 37.

At this time, the beam shaping prism 35 having the structure described above generates the first and second lights 13a and 15a while passing through the first and / or second plate beam splitters 20 and 25. Astigmatism occurs in a direction orthogonal to the astigmatism, whereby astigmatism generated by the first and / or second plate type beam splitters 20 and 25 is canceled out and corrected.

Here, when the thickness of the plate-shaped beam splitter is very thin (0.2 mm or less), astigmatism does not greatly occur, but such a thin plate-shaped beam splitter has difficulty in mass production as described above, and thus is difficult to apply. Since the first and second plate-type beam splitters 20 and 25 applied to the optical pickup according to the present invention have a large thickness of, for example, 0.2 mm or more, which needs to consider astigmatism, the first and second as described above. It is necessary to offset the astigmatism generated by the two-plate beam splitters 20 and 25, and by canceling and configuring the beam shaping prism 35 and the optical lens 31 as described above, It is possible.

On the other hand, the beam shaping prism 35 having the structure as described above may be able to fold the traveling path of the first and second light 13a (15a) incident from the twin laser 11 side by 90 degrees, the light according to the present invention Pickup has the advantage that a reflection mirror, which is generally employed in optical pickup, is required to bend the optical path of the light 90 degrees.

On the other hand, the optical pickup according to the present invention has a wedge as shown in FIG. 6 instead of a structure in which two surfaces involved in the reflection and / or transmission of the first and second lights 13a and 15a are parallel to each other. It may be provided with the first and second plate type beam splitters 70 and 75 having a structure.

FIG. 6 schematically shows a main part of an optical pickup according to a second exemplary embodiment of the present invention, in which the first and second plate type beam splitters 70 and 75 each have a wedge type structure. Except for the optical pickup according to the first embodiment of the present invention, the optical configuration is substantially the same.

In the present embodiment, the first and second plate beam splitters 70 and 75 are formed so that the outer surfaces which do not face each other are wedge surfaces.

That is, the first plated beam splitter 70 reflects the same wavelength as the first and second surfaces 20a and 20b of the first plated beam splitter 20 according to the first embodiment of the present invention. And / or first and second surfaces 70a and 70b adapted to exhibit transmission characteristics, and the second surface 70b is formed as a wedge surface.

In addition, the second plate-type beam splitter 75 reflects the same wavelength as the third and fourth surfaces 25a and 25b of the second plate-type beam splitter 25 according to the first embodiment of the present invention. And / or third and fourth surfaces 75a and 75b configured to exhibit transmission characteristics, and the fourth surface 75b is formed as a wedge surface.

Since the first and second plate-type beam splitters 70 and 75 are inclined with respect to the optical paths of the first and second light 13a and 15a, the first and second light 13a and 15a. Is a small amount, but not negligible, in comparison to the astigmatism generated by the first and / or second plate type beam splitter 75 in the first and second lights 13a, 15a in the form of divergent light. Corresponding coma aberration may occur.

Such coma aberration can be eliminated by forming the first and second plate-type beam splitters 70 and 75 in a wedge-like structure that is symmetrical with each other as in the present embodiment.

As described above, the optical pickup according to the first and second embodiments of the present invention includes an optical lens (not shown) so that the first and second lights 13a and 15a diverging or converging are incident on the beam shaping prism 35. 31 is arranged to form a finite optical system, so that the first and second light beams 13a and 75 are formed by the first plate-type beam splitters 20 and 70 and / or the second plate-type beam splitters 25 and 75. The astigmatism generated in 15a) is canceled by the beam shaping prism 35.

The optical pickup according to the first and second embodiments of the present invention as described above is a twin-laser between the optical lens 31 and the twin laser 11 which functions similar to the collimating lens in the conventional optical pickup. Since the first plate-type beam splitter 20 and 70 and the second plate-type beam splitter 25 and 75 functioning to match the optical axis of the light emitted from 11) and function as the optical path changer are disposed, Since the optical path length of the optical system can be shortened, it can be used as a slim optical pickup applied to a device with a large space constraint such as a notebook computer.

Meanwhile, the optical pickup according to the present invention may be formed in a structure suitable for a system capable of sufficiently securing the mechanical distance. 7 and 8 show an optical pickup according to the third and fourth embodiments of the present invention having a structure suitable for a system capable of sufficiently securing the mechanical distance.

Referring to FIG. 7, the optical pickup according to the third embodiment of the present invention, when compared with the first embodiment of the present invention described with reference to FIGS. 2 and 3, has a twin laser 11 and a first plate type beam. Between the splitters 20, a collimating lens 81 for converting the first and / or second light 15a emitted from the twin laser 11 into parallel light is provided, and the second plate-type beam splitter 25 is provided. ) And the objective lens 37 are characterized in that the optical lens 31 and the beam shaping prism 35 in the first embodiment of the present invention are excluded. In FIG. 7, reference numeral 85 denotes a reflection mirror for bending the paths of the first and second lights 13a and 15a by 90 degrees. Here, the members having the same optical characteristics as in FIGS. 2 and 3 and having substantially the same or similar functions are denoted by the same reference numerals as in FIGS. 2 and 3, and repeated descriptions thereof are omitted.

As in the optical pickup having the optical configuration shown in Fig. 7, the first and / or second light 13a, 15a is applied to the first and second plate-type beam splitters 20, 25 in the form of parallel light. When incident, the astigmatism is suppressed unlike the optical pickup according to the first and second embodiments of the present invention.

8, the optical pickup according to the fourth embodiment of the present invention, when compared to the third embodiment of the present invention, the first and second plate-type beam splitters 70 and 75 of the wedge-shaped structure It is characterized by the points provided. Here, the members having the same optical properties as those in the previous embodiments and having substantially the same or similar functions are denoted by the same reference numerals as in the previous embodiments, and repeated descriptions are omitted.

As shown in Fig. 8, if the first and second plate-type beam splitters 70 and 75 are wedge-shaped structures as in the second embodiment of the present invention, the first and second plate-type beams are arranged at an angle. The splitters 70 and 75 can suppress the coma aberration from occurring in the first and second lights 13a and 15a. Of course, astigmatism is suppressed because the first and / or second light 13a and 15a are incident on the first and second plate-type beam splitters 70 and 75 in the form of parallel light.

Here, the optical pickup according to the third and fourth embodiments of the present invention described with reference to FIGS. 7 and 8 is emitted from the twin laser 11 between the twin laser 11 and the collimating lens 81. A beam shaping prism (not shown) may be further provided for beam shaping the first and / or second lights 13a and 15a.

When the optical pickup according to the present invention as described above has a beam shaping prism, the optical utilization efficiency is good, and the optical pickup according to the present invention can be easily switched for recording as the twin laser 11 is developed. There is one advantage.

In the above, the optical pickup according to the present invention has been described and illustrated as having an optical configuration as shown in FIGS. 2 and 6 to 8, but the optical configuration of the optical pickup according to the present invention may be variously modified.

That is, in the optical pickup according to the present invention, the first plate type beam splitter for matching the optical paths of the twin laser 11 and the first and second light 13a and 15a emitted from the twin laser 11. Various modifications and other embodiments of the optical configuration are possible except for the 20 and 70 and the second plated beam splitter 25 and 75. Therefore, the true technical protection scope of the optical pickup according to the present invention will be defined by the claims.

As described above, the optical pickup according to the present invention provides a first plate type beam splitter for further widening the distance between the optical paths of the two light beams emitted from the twin laser, and narrows the interval between the two optical paths. Since the second plate-type beam splitter for matching the two optical paths is provided, it is possible to correct the difference between the light emitting points of the two semiconductor lasers of the twin laser.

According to the present invention, since the twin laser is provided as the light source, the overall structure of the optical pickup is simplified.

In addition, according to the present invention, by adding one more light source, at least some of the existing CD-based optical discs and at least some of the DVD-based optical discs suitable for the development of high-density optical discs having a storage capacity larger than that of DVDs in the future It is possible to easily apply to the optical pickup to employ the optical disk compatible.

In addition, according to the present invention, the thicknesses of the first and second plate-type beam splitters can be made sufficiently thick to enable mass production and manufacturing.

1 is a view schematically showing the main configuration of a conventional optical pickup having a twin laser,

2 is a perspective view schematically showing an optical pickup with a twin laser according to a first embodiment of the present invention;

3 is a plan view schematically showing the main part of FIG.

4 is a perspective view showing the beam shaping prism of FIG.

5 is a front view of the beam shaping prism of FIG. 4;

6 is a plan view schematically showing a main part of an optical pickup according to a second embodiment of the present invention;

7 is a view showing an optical configuration of an optical pickup according to a third embodiment of the present invention;

8 is a view showing an optical configuration of an optical pickup according to a fourth embodiment of the present invention.

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

11 ... Twin Laser 13,15 ... First and Second Semiconductor Lasers

13a, 15a, 17a ... first to third light 17 ... single light source

19 ... Photodetector 20,70 ... First plate beam splitter

20a, 70a ... Page 1 20b, 70b ... Page 2

25, 75 ... 2nd plate type beam splitter 25a, 75a ... 3rd side

25b, 75b ... Page 4 31 ... Optical Lens

35.Beam shaping prism 35a, 35b, 35c ... first to third side

37.Objective lens 81.Collimating lens

Claims (19)

In the optical pickup to focus the light emitted from the twin laser to the objective lens to irradiate the recording medium, and to receive the light reflected from the recording surface of the recording medium with a photodetector to detect the light, The twin laser has a structure in which the first and second semiconductor lasers, respectively, emitting the first and second light having different wavelengths are optically modular. A first surface reflecting the first light incident from the twin laser and transmitting a second light; and a second surface reflecting the second light incident therein through the first surface toward the first surface; A first plate-type beam splitter for causing a gap between the optical paths of the first and second light to be wider than when emitted from the twin laser; A third surface facing the first surface of the first plate-shaped beam splitter and transmitting the first light and reflecting and transmitting the second light, the first light reflecting and transmitting, and the second light transmitting And a second plate-type beam splitter configured to narrow the distance between the optical paths of the first and second light beams spread by the first plate-type beam splitter. The optical pickup of claim 1, wherein the optical path difference of the first and second light due to the difference in the light emitting point of the second semiconductor laser can be corrected. delete The optical pickup of claim 1, wherein each of the first and second plate-type beam splitters has a structure in which two surfaces that are involved in reflection and / or transmission of light are parallel to each other. The optical pickup of claim 1, wherein each of the first and second plate-type beam splitters has a wedge-shaped structure. The optical pickup according to claim 4, wherein the first and second plate-type beam splitters have a wedge surface with outer surfaces not facing each other. The optical pickup of claim 1, wherein each of the first and second plate-type beam splitters has a structure in which two surfaces that are involved in reflection and / or transmission of light are parallel to each other. The optical pickup of claim 1, wherein each of the first and second plate-type beam splitters has a wedge-shaped structure. 8. The optical pickup of claim 7, wherein the first and second plate-type beam splitters have a wedge surface with outer surfaces not facing each other. The beam shaping prism according to any one of claims 1 and 3 to 8, further comprising: a beam shaping prism for beam shaping the first and / or second light emitted from the twin laser; And an optical lens positioned between the twin laser and the beam shaping prism. The method of claim 9, wherein the first and second light emitted from the twin laser is incident to the first and second plate-type beam splitter in the form of divergent light, The optical lens and the beam shaping prism are positioned between the second plate-type beam splitter and the objective lens, The optical lens is incident on the beam shaping prism in a form of light that converges or diverges the first and second lights so that astigmatism can occur by the beam shaping prism. And the beam shaping prism is configured to correct astigmatism generated in the first and second beams in the form of divergent light by the first and / or second plate type beam splitter. The beam shaping prism of claim 10, wherein the beam shaping prism comprises: a first surface on which light is incident from the second plate type beam splitter; a second surface on which the light beam is incident through the first surface; And a third surface reflecting the incident light reflected from two surfaces toward the second surface to emit the light through the second surface, wherein the first to third surfaces form a triangular structure. Optical pickup. 12. The optical disc of claim 10, wherein one of the first and second lights has a wavelength suitable for recording and / or playing a DVD-based optical disc, and the other has a wavelength suitable for recording and / or reproducing a CD-based optical disc. An optical pickup comprising optical, wherein at least a portion of a DVD-based optical disc and at least a portion of a CD-based optical disc are compatible. The method according to claim 1, wherein the first and / or second light emitted from the twin laser in the form of divergent light is separated between the twin laser and the first plate-type beam splitter. And a collimating lens for converting the light into parallel light. 15. The optical disc of claim 13, wherein one of the first and second lights has a wavelength suitable for recording and / or playing a DVD-based optical disc, and the other has a wavelength suitable for recording and / or reproducing a CD-based optical disc. An optical pickup comprising optical, wherein at least a portion of a DVD-based optical disc and at least a portion of a CD-based optical disc are compatible. 9. The light according to any one of claims 1 and 3 to 8, wherein any one of the first and second lights is a light having a wavelength suitable for recording and / or playing a DVD-based optical disc, and the other is a CD-based light. An optical pickup having a wavelength suitable for recording and / or reproducing an optical disk of the optical disk, wherein at least a portion of the DVD-based optical disk and at least a portion of the CD-based optical disk are compatible. 9. The apparatus of claim 1, further comprising: a single light source for emitting the third light. One of the first to third lights is light having a wavelength suitable for recording and / or playing a DVD-based optical disc, the other is light having a wavelength suitable for recording and / or playing a CD-based optical disc, and the other is a DVD. It is light of a blue-violet wavelength region suitable for a high density optical disc having a larger recording capacity than the optical disc of the series, and at least part of the DVD series optical disc, at least a part of the CD series optical disc, and the high density optical disc are compatible. Optical pickup. 17. The optical pickup according to claim 16, wherein the single light source is arranged such that the third light emitted therefrom passes through the first plated beam splitter and is reflected by the second plated beam splitter toward the recording medium. . 18. The optical pickup according to claim 17, wherein the photodetector is arranged to receive first to third light reflected from the recording surface of the recording medium and transmitted through the second plate type beam splitter. 9. The optical detector according to any one of claims 1 to 3, wherein the photodetector is arranged to receive first and second light reflected from the recording surface of the recording medium and transmitted through the second plate-type beam splitter. Optical pickup characterized by.