KR19990070007A - Compatible Optical Pickup Device - Google Patents

Abstract

Disclosed is a compatible optical pickup apparatus capable of interchangeably employing recording media having different formats.

The disclosed optical pickup apparatus includes a first base, a first light source provided on the first base to irradiate laser light of a predetermined wavelength region, and a first light detector provided on the first base around the first light source. And a first transparent member disposed on the first light source, and formed on the surface of the recording medium side of the first transparent member so that the light irradiated from the first light source passes straight through and the light incident from the recording medium is directed toward the first photodetector. A first optical module having a first hologram element for diffraction transmission; A second base, a second light source provided on the second base and irradiating laser light in a wavelength region different from the light emitted from the first light source, and a second light detector provided on the second base around the first light source. And a second transparent member disposed on the second light source, and formed on the recording medium side of the second transparent member so that the light irradiated from the second light source passes straight through and the light incident from the recording medium side is the second photodetector. A second optical module having a second hologram element diffraction-transmitting toward the side; A wavelength selective beam splitter disposed on an optical path between the first and second optical modules and the recording medium and selectively transmitting / reflecting according to the wavelength region of the incident light; And an objective lens disposed on an optical path between the beam splitter and the recording medium to focus light emitted from the first and second light sources onto the recording medium.

Description

Compatible Optical Pickup Device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compatible optical pickup apparatus, and more particularly, to a compatible optical pickup apparatus in which compatible recording media having different formats can be used.

In general, an optical pickup device is employed in a compact disc player (CDP), a digital multifunction disc player (DVDP), a CD-ROM driver, a DVD-ROM driver, or the like to perform recording / reproducing of information on a recording medium in a non-contact manner.

DVDP and DVD-ROM are attracting attention in the video / audio field as devices capable of high-density recording / playback. The optical pickup device employed in this DVDP employs not only digital video discs (DVDs) but also compact discs (CDs), CD-Rs (Recordables), CD-Is, and CD-Gs as recording media for compatibility. Even if so, it should be possible to record and / or reproduce information.

However, the thickness of the DVD has been standardized to a different specification from the thickness of the CD family due to mechanical disc tilt tolerance and objective lens numerical aperture. That is, the thickness of the existing CD family is 1.2mm while the DVD is 0.6mm. As such, when the CD family and the DVD have different thicknesses, spherical aberration due to the difference in thickness occurs when the optical pickup apparatus for DVD is applied to the CD family. This spherical aberration causes a problem of failing to obtain sufficient light intensity for recording the information signal or deterioration of the signal during reproduction.

Also, in the wavelength of the reproduction light source, DVD has been standardized into a wavelength range different from that of the CD family. That is, while the reproduction light source wavelength for the existing CD family is approximately 780 nm, the reproduction light source wavelength for DVD is approximately 650 nm.

Due to this difference in standardization, since information recorded on a DVD cannot be reproduced by a normal CDP, development of an optical pickup device for a DVD is required. At this time, the optical pickup device for DVD should be compatible with the existing CD family.

As described above, the conventional compatible optical pickup apparatus in consideration of the point, the first light source 21 and the first photodetector 27 to emit light of 780nm wavelength and to receive incident light as shown in FIG. ) Converts a traveling path of light irradiated from the optical module 20 formed integrally with each other, the second light source 31 emitting light having a wavelength of 650 nm, and the first and second light sources 21 and 31, respectively. First and second polarization beam splitters 25 and 33 for reflection, objective lens 17 for focusing incident light onto the disk 10, and reflected from the disk 10 and the first and second polarization beam splitters. And a second photodetector 37 for receiving the incident light through (25) and (33). Here, the first light source 21 is for a relatively thin disk 10a, such as a DVD, and the second light source 31 is for a relatively thick disk 10b, for example, a CD family.

The optical module 20 includes a substrate 22 on which a first light source 21, a first light detector 27, the first light source 21 and the first light detector 27 are installed, and the first light source 21. A housing 24 provided to surround the first light source 21 and the first photodetector 27, and a hologram element 23 that changes the traveling path according to the traveling direction of the light transmitted through the housing 24; It is configured to include.

The first and second polarization beam splitters 25 and 33 have mirror surfaces adapted to selectively transmit or reflect incident light according to the polarization direction, and may be integrally formed as shown in the optical configuration. .

The light irradiated from the first light source 21 is reflected by the first polarized beam splitter 25 toward the disk 10, and the light irradiated from the second light source 31 is the second polarized beam splitter. After being reflected at 33, it passes through the first polarizing beam splitter 25 and is directed toward the disk 10.

A λ / 4-wavelength plate for converting light of linearly polarized light into circularly polarized light and circularly polarized light into linearly polarized light on the side of the objective lens 17 side of the first polarization beam splitter 25. 11 is disposed. In addition, on the optical path between the λ / 4 wavelength plate 11 and the objective lens 17, a reflecting mirror 13 reflecting incident light in consideration of optical arrangement and a collimating lens 15 focusing the incident light Is placed.

The light irradiated from the first light source 21 is reflected by the disk 10b having a relatively thick thickness, and is reflected by the first polarization beam splitter 25. Thereafter, the light is diffracted by the hologram element 23 and then received by the first photodetector 27.

On the other hand, the light irradiated from the second light source 31 is reflected by the disk 10a having a relatively thin thickness, and passes through the first and second polarization beam splitters 25 and 33. This light passes through the detection lens 35 causing astigmatism and is received by the second photodetector 37.

As described above, the conventional compatible optical pickup apparatus constructed is complicated in its configuration and has a large number of parts. Accordingly, there is a disadvantage in that assemblability is lowered and defective factors are increased.

The present invention has been made in view of the above-described disadvantages, and an object thereof is to provide a compatible optical pickup apparatus having a structure of simplifying an optical configuration and reducing a number of components.

1 is a schematic view showing an optical arrangement of a conventional compatible optical pickup device.

2 is a schematic view showing an optical arrangement of a compatible optical pickup device according to an embodiment of the present invention.

3 is a schematic view showing the first and second hologram elements of FIG.

4 is a graph showing the transmission and diffraction efficiency according to the temperature of the first and second hologram elements shown in FIG.

<Description of Symbols for Main Parts of Drawings>

10 ... Recording medium 40 ... First optical module 41 ... First base

43.1st board 45,75 ... Lead frame 47,77 ... Wire

51 1st light source 53 ... 1st light detector 55 ... light detector for monitor

57 1st transparent member 60 1st hologram element 61,63 crystal layer

65 Liquid crystal polymer 67 Phase delay plate 70 Second optical module

71.2nd base 73 ... 2nd substrate 76 ... mount

81 ... second light source 83 ... second light detector 85 ... second transparent member

87 ... Second Hologram Element 91 ... Beam Splitter

93 ... reflective mirror 95 ... collimating lens 97 ... objective lens

In accordance with an aspect of the present invention, a compatible optical pickup apparatus includes a first base, a first light source provided on the first base to irradiate laser light in a predetermined wavelength region, and a periphery of the first light source. A first photodetector provided on the first base of the first transparent member, a first transparent member disposed on the first light source, and light formed on a side of the recording medium of the first transparent member and irradiated from the first light source A first optical module having a first hologram element which transmits straight and diffracted and transmits light incident on the recording medium toward the first photodetector; A second base, a second light source provided on the second base and irradiating laser light in a wavelength region different from that irradiated from the first light source, and a second light source provided on the second base around the first light source. A second photodetector, a second transparent member disposed on the second light source, and light formed on the side of the recording medium side of the second transparent member and irradiated from the second light source are straight through and incident from the recording medium side A second optical module having a second hologram element for diffracted transmission of the light to the second photodetector; A wavelength selective beam splitter disposed on an optical path between the first and second optical modules and the recording medium and selectively transmitting / reflecting according to a wavelength region of incident light; And an objective lens disposed on an optical path between the beam splitter and the recording medium to focus light emitted from the first and second light sources onto the recording medium.

Hereinafter, exemplary embodiments of a compatible optical pickup apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 2, a compatible optical pickup apparatus according to a preferred embodiment of the present invention may generate and irradiate light of different wavelength regions and receive light reflected from the recording medium 10, respectively. And disposed on an optical path between the second optical modules 40 and 70, the first and second optical modules 40 and 70, and the recording medium 10, selectively according to the wavelength region of the incident light. A wavelength selective beam splitter 91 for transmitting / reflecting, and disposed on an optical path between the beam splitter 91 and the recording medium 10 and exiting from the first and second optical modules 40 and 70. And an objective lens 97 for focusing the collected light onto the recording medium 10.

The first optical module 40 includes a first base 41, a first light source 51 provided on the first base 41 to irradiate laser light in a predetermined wavelength region, and the first light source ( 51 a first photodetector 53 provided on the first base 41 in the vicinity, a first transparent member 57 disposed on the first light source 51, and the first transparent member 57. Formed on the side of the beam splitter 91 so that the light emitted from the first light source 510 passes straight through and the light incident from the recording medium 10 is diffracted and transmitted toward the first photodetector 53. One hologram element 60 is provided.

The first base 43 is provided with a first substrate 43 through which the first light source 51 and the first photodetector 53 are electrically connected, and the first substrate 43 is externally connected to the first base 41. A plurality of lead frames 45 electrically coupled to each other, and wires 47 connecting the first substrate 43 to the first light source 51 and the first photodetector 53, are further provided.

The first light source 51 is a semiconductor laser that irradiates light of a predetermined wavelength, and is preferably a surface light laser that emits light in a stacking direction of the semiconductor material layers constituting the first light source 51. For example, the first light source 51 emits light having a red wavelength in the region of about 635 to 650 nm so as to be suitable when the relatively thin disk 10a is employed as the recording medium 10.

The first transparent member 57 is installed in the first base 41 so as to be spaced apart from the upper surface of the first light source 51 by a predetermined interval to transmit incident light. The first hologram element 60 is installed on a surface of the first transparent member 57 that faces the beam splitter 91.

As shown in FIG. 3, the first hologram element 60 includes a pair of crystal layers 61 and 63 and a liquid crystal polymer 65 positioned between the crystal layers 61 and 63. It is preferable that it is a polarization hologram element. The polarization hologram element diffracts incident light into a 0th order beam and a 1st order beam, and when the 0th order beam is S-polarized, the primary beam becomes P-polarized light, and when the 0th order beam is P-polarized light, the primary beam is S-polarized .

FIG. 4 is a graph showing diffraction efficiency and transmittance for P-polarized light and S-polarized light according to temperature in the polarization hologram device shown in FIG. 3.

As shown, the light of P polarization in the range of approximately 0 ° C. to 60 ° C. has a transmittance of about 90% or more and a diffraction efficiency of less than about 5%. The light of S-polarized light has a diffraction efficiency of about 70% and a transmittance of about 5%.

Therefore, when considering the characteristics of the polarization hologram element and the transmission / diffraction efficiency according to the polarization, the amount of light received by the first light detector 53 by suppressing the loss of the light irradiated from the first light source 51 to the maximum Can be increased.

As described above, when the polarization hologram element is employed as the first hologram element 60, it is preferable to further include a phase delay plate 67, for example, lambda / 4 wavelength plate, which changes in the polarization direction of transmitted light. Do. This phase delay plate 67 is located between one crystal layer 61 and the liquid crystal polymer 65, as shown in FIG.

In addition, the first optical module 40 is a monitor photodetector installed on the first substrate 43 around the first light source 51 to monitor the amount of light emitted from the first light source 51. It is preferable to further include (55). In this case, a reflecting member 59 is provided on a portion of the surface of the first transparent member 57 facing the first light source 51 so as to reflect a part of the light emitted from the first light source 51. . The reflective member 59 may be a reflective coating film formed on the first transparent member 57.

The second optical module 70 includes a second base 71, a second light source 81 provided on the second base 71 to irradiate laser light in a predetermined wavelength region, and the second light source ( 81, a second photodetector 83 provided on the second base 71 in the vicinity, a second transparent member 85 disposed on the second light source 81, and the second transparent member 85; Formed on the side of the beam splitter 91 so that the light irradiated from the second light source 81 passes straight through and the light incident from the recording medium 10 is diffracted and transmitted toward the second photodetector 83. A second hologram element 87 is provided.

The second base 71 has a second substrate 73 through which the second light source 81 and the second photodetector 83 can be electrically connected, and the second substrate 73 to the outside. A plurality of lead frames 75 electrically coupled to each other, and wires 77 connecting the second substrate 73 to the second light source 81 and the second photodetector 83 are further provided.

The second light source 81 is a semiconductor laser for irradiating light of a predetermined wavelength. For example, the second light source 81 emits light having an infrared wavelength of about 780 nm so as to be suitable when the relatively thick disk 10b is employed as the recording medium 10. As shown in the drawing, the second light source 81 is a corner light emitting laser mounted on the side wall of the mount 76 and irradiates light to the edge thereof, or is installed on a substrate similarly to the first light source 51. It may be a surface light laser for emitting light in the stacking direction of the semiconductor material layers.

The second transparent member 85 is installed on the second base 71 so as to be spaced apart from the upper surface of the second light source 81 by a predetermined interval and transmits incident light. The second hologram element 87 is disposed on a surface of the second transparent member 85 that faces the beam splitter 91.

As described above, when approximately 780 nm is used, since the light efficiency is not largely a problem, the second hologram element 87 employs a conventional hologram element that diffracts incident light into zero order light and primary light.

The beam splitter 91 selectively transmits / reflects according to the wavelength of incident light. For example, light of approximately 635 to 650 nm wavelength which is incident toward the mirror surface 91a is reflected, and light of approximately 780 nm wavelength is transmitted.

The objective lens 97 focuses the light irradiated from the first optical module 40 onto a relatively thin disk 10a, and the light irradiated from the second optical module 70 has a relatively thick thickness. The thick disk 10b is focused.

A collimating lens 95 may be further provided on the optical path between the beam splitter 91 and the objective lens 97 to focus incident incident light into a parallel light. In addition, the optical mirror may further include a reflection mirror 93 as shown in FIG. 2.

Hereinafter, an operation of a compatible optical pickup apparatus according to an exemplary embodiment of the present invention will be described with reference to the drawings.

First, when a relatively thin disk 10a such as a DVD is used as the recording medium 10, the light irradiated from the first optical module 40 is used as the effective light.

For example, when the light irradiated from the first light source 51 is light of P polarization, and the first hologram element 60 is a polarization hologram element having polarization transmission / diffraction efficiency with temperature as shown in FIG. 4, The 0th order light by the polarization hologram element is light of P polarization, and the 1st order light is S polarization light. Accordingly, most of the light irradiated from the first light source 51 and transmitted through the first transparent member 57 passes straight through the first hologram element 60 and is directed toward the wavelength selective beam splitter 91.

Here, the light of P-polarized light transmitted through the liquid crystal polymer 65 of the first hologram element 60 becomes circularly polarized light while passing through the phase delay plate 67. The light is reflected by the mirror surface 91a of the beam splitter 91 and then changed in parallel in the collimating lens 95. The light is focused while passing through the objective lens 97 so as to have a relatively thin disk 10a. It is concluded. Thereafter, the light reflected from the disk 10a passes through the objective lens 97 and the collimating lens 97, and then is reflected from the mirror surface 91a of the beam splitter 91 to the first hologram element 60. Reentry The re-incident light is selectively changed in polarization direction in accordance with the information recording of the disc 10a, and passes through the phase delay plate 67 to become light of S-polarized light. When the light whose polarization direction is changed is transmitted through the hologram element 60, the zeroth order beam becomes S-polarized light and the primary beam becomes P-polarized light. Therefore, most of the light incident from the disk side is diffracted and transmitted to the first photodetector 53.

The first photodetector 53 detects an error signal and an information signal for the relatively thin disk 10a from the received signal.

Therefore, by increasing the light utilization efficiency by adjusting the transmission / diffraction using the polarization hologram element, the optical power received by the first photodetector 53 can be increased without increasing the power of the first light source 51. Can be.

Here, a part of the light irradiated from the first light source 51 is reflected by the reflecting member 59 provided on one surface of the first transparent member 57 and then received by the monitor photodetector 55, from which The light output of the first light source 51 is controlled.

On the other hand, when the disk 10b having a relatively thick thickness is employed as the recording medium, the light irradiated from the second light source 81 is used as the effective light.

The light emitted from the second light source 81 passes through the second transparent member 85, the second hologram element 87, and the beam splitter 91 in a straight line, and is then focused by the objective lens 97 to have a thickness. It forms on the relatively thick disk 10b. The light reflected by the disk 10b passes through the objective lens 97 and the beam splitter 91 and then re-injects into the second hologram element 87. The second hologram element 87 diffracts incident light so that the light reincident by the hologram pattern is directed to the second photodetector 83. The second photodetector 83 detects an error signal and an information signal for the relatively thin disk 10b from the received signal.

The compatible optical pickup device according to the present invention configured as described above improves the light utilization efficiency by using a polarization hologram element, thereby solving the problem of low power of the surface light laser employed as the first light source and being received by the first photodetector. The amount of light can be increased.

In addition, by modularizing the two light sources and the two photodetectors having different wavelengths, the optical pickup structure can be simplified to improve assembly and facilitate optical alignment.

Claims (6)

A first light source provided on the first base, the first light source provided on the first base to irradiate laser light of a predetermined wavelength region, the first light detector provided on the first base around the first light source, and the first light source A first transparent member disposed on the first transparent member, and formed on a surface of the recording medium side of the first transparent member so that light irradiated from the first light source passes straight through and light incident from the recording medium is diffracted toward the first photodetector. A first optical module having a first hologram element for transmitting; A second base, a second light source provided on the second base and irradiating laser light in a wavelength region different from that irradiated from the first light source, and a second light source provided on the second base around the first light source. A second photodetector, a second transparent member disposed on the second light source, and light formed on the side of the recording medium side of the second transparent member and irradiated from the second light source are straight through and incident from the recording medium side A second optical module having a second hologram element for diffracted transmission of the light to the second photodetector; A wavelength selective beam splitter disposed on an optical path between the first and second optical modules and the recording medium and selectively transmitting / reflecting according to a wavelength region of incident light; And an objective lens disposed on an optical path between the beam splitter and the recording medium to focus the light emitted from the first and second light sources onto the recording medium. The method of claim 1, wherein the first light source is a surface light laser that emits light of a red wavelength in the stacking direction, and the second light source is a semiconductor laser that emits light of the infrared wavelength in the stacking direction. Compatible optical pickup device. The method of claim 2, wherein the first hologram element, And a pair of crystal layers and a liquid crystal polymer positioned between the crystal layers, wherein the polarization hologram elements vary the transmission efficiency and diffraction efficiency according to the polarization state of the incident light. 4. The compatible optical pickup apparatus of claim 3, further comprising a phase delay plate positioned between the liquid crystal polymer and one crystal layer to change a polarization direction of incident light. The method according to any one of claims 1 to 4, wherein the first optical module, A reflection member installed on a part of the surface of the first transparent member that faces the first light source and reflecting a part of the light irradiated from the first light source; And a monitor photodetector mounted on the first base around the first light source to receive the light reflected from the reflective member to detect the amount of light emitted from the first light source. Optical pickup device. 6. The compatible optical pickup apparatus of claim 5, wherein the reflective member is a reflective coating film formed on a part of a surface of the first transparent member facing the first light source.