KR100234261B1 - Compatible optical pickup device - Google Patents

Abstract

Disclosed is a disk compatible optical pickup device having a different format.

The disclosed apparatus comprises: a light source; An objective lens for focusing the light emitted from the light source onto the recording surface of the recording medium; A photodetector for receiving the light reflected from the recording medium and detecting an information signal and an error signal; A first light source for generating and outputting a laser beam of a predetermined wavelength region as a light source; and a second light source for generating and outputting a laser beam of a predetermined wavelength region as a light source, the first light source being disposed on the optical path between the light source and the objective lens; And a second light source for generating and outputting a laser beam of a different wavelength range from the first light source, wherein the first light source emits light from the first light source and receives the light incident via the light path changing means, A detector; And a second photodetector which is emitted from the second light source and which receives the light incident via the recording medium and the light path changing means.

Description

Compatible optical pickup device

FIG. 1 is a graph showing the sensitivity according to the wavelength of a light source when a CD-R is adopted as a recording medium.

FIG. 2 is a schematic diagram showing an optical arrangement of a conventional compatible optical pickup device. FIG.

FIG. 3 is a schematic view showing an optical arrangement of a compatible optical pickup device according to a first embodiment of the present invention; FIG.

FIG. 4 is a schematic view showing an optical arrangement of a compatible optical pickup device according to a second embodiment of the present invention; FIG.

FIG. 5 is a schematic view showing an optical arrangement of a compatible optical pickup device according to a third embodiment of the present invention; FIG.

FIG. 6 is a schematic view showing an optical arrangement of a compatible optical pickup device according to a fourth embodiment of the present invention; FIG.

7 is a schematic cross-sectional view of an integral first module employed in FIG. 6;

FIG. 8 is a schematic cross-sectional view of an integral second module employed in FIG. 6; FIG.

FIG. 9 is a schematic view showing an optical arrangement of a compatible optical pickup device according to a fifth embodiment of the present invention; FIG.

Description of the Related Art

10: recording medium 41: objective lens

45: collimating lens 51: first light source

53: first beam splitter 55: first sensor lens

57: first photodetector 61: second light source

63: second beam splitter 63: third beam splitter

67: second sensor lens 69: second photodetector

70: integrated first module 71: substrate

72: housing 73: projection window

74: hologram element 75: mount

76: lead 80: integral second module

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compatible optical pickup apparatus, and more particularly to a disc-compatible optical pickup apparatus compatible with disc-shaped recording media of different formats.

2. Description of the Related Art In general, an optical pickup device is used in a compact disc player (CDP), a digital video disc player (DVDP), a CD-ROM driver, a DVD-ROM driver or the like and performs recording / reproduction of information on a recording medium in a noncontact manner.

DVDP and DVD-ROM are high-density recording / playback devices that have been attracting attention in the field of video / audio. The optical pickup device employed in this DVDP adopts a CD family such as compact disc (CD), CD-R (recordable), CD-I and CD-G as well as a digital video disc The information recording and / or reproducing should be possible.

However, the thickness of the DVD was standardized to be different from the thickness of the CD family due to the slope tolerance of the mechanical disk and the numerical aperture of the objective lens. That is, the thickness of the existing CD family is 1.2 mm whereas the DVD is 0.6 mm. As described above, when the optical pickup device for DVD is applied to the CD family because the thicknesses of the CD family and the DVD are different from each other, spherical aberration due to the thickness difference is generated. This spherical aberration causes a problem that a sufficient light intensity necessary for recording an information signal is not obtained or a signal at the time of reproduction deteriorates.

Also, in terms of the wavelength of the reproduction light source, DVD was standardized as a wavelength region different from the CD family. That is, the wavelength of the reproduction light source for the existing CD family is approximately 780 nm, whereas the wavelength of the reproduction light source of the DVD is approximately 650 nm.

Due to such a difference in standardization, it is impossible to reproduce information recorded on a DVD with a normal CDP, and therefore, development of an optical pickup for DVD is required. At this time, the optical pickup apparatus for the DVD should be compatible with the existing CD family.

In consideration of this point, there has been disclosed a disc-compatible optical pickup apparatus of a variety of different formats.

These conventional disc compatible optical pick-up devices use a single light source to focus on overcoming the problems caused by the disc-to-disc thickness difference. That is, the compatible optical pickup device employs a light source that emits light of a short wavelength (approximately 650 nm) conforming to the DVD format. In this case, deterioration of about 5% is generated as compared with the optical pickup device employing a light source that emits light in the wavelength region of 780 nm, but this is not a big problem because it is within the tolerance range during reproduction.

However, when a CD-R, which is a recordable disc that is one of the CD family, is adopted as the recording medium, when using a light source that emits light in a wavelength region of approximately 650 nm, as shown in FIG. 1, Differs from the case where a light source that emits light in a wavelength region is used. Since the conventional CD-R has an organic dye film recording layer as is widely known, when light of a wavelength region of 650 nm is used due to the difference in sensitivity, a serious problem that data recorded on the CD-R is destroyed is caused.

To solve this problem, a new type of CD-R recording medium is being developed. Such a solution is not a fundamental solution for protecting data already recorded on a CD-R that has become widely available.

In order to overcome such a problem, a compatible optical pickup device employing two light sources as shown in FIG. 2 has been disclosed.

As shown in the figure, the light source includes a first light source 21 that emits light having a wavelength of 635 nm and a second light source 31 that emits light having a wavelength of 780 nm. The first light source 21 is for a relatively thin disc 10a such as a DVD and the second light source 31 is for a relatively thick disc 10b such as a CD family.

The light emitted from the first light source 21 is reflected by the polarization beam splitter 23 and directed toward the disk 10. [ At this time, an interference filter 33, a quarter wave plate 11, a hologram element 13, and an objective lens 15 are positioned on the optical path between the polarization beam splitter 23 and the disk 10. The interference filter 33 reflects the light emitted from the second light source 31 to be directed to the disc 10 and transmits the light incident from the disc 10 side. The 1/4 wave plate 11 is an optical member for converting the phase of incident light. The light irradiated from the first light source 21 and the second light source 31 passes through the quarter wave plate 11 twice and is directed to the polarization beam splitter 23 in a state where the phase is changed by 180 degrees And passes through the polarization beam splitter 23 to be formed into a photodetector 17 for detecting an information signal and an error signal. The hologram element 13 has a predetermined diffraction pattern formed at the center of its surface. Since the light emitted from the first light source 21 is incident on a region larger than the region where the diffraction pattern is formed, the light passes through the hologram element 13 in a state of being not diffracted, that is, So that it is formed on the disk 10a.

On the other hand, the light emitted from the second light source 31 is diffracted by the hologram element 13 at a predetermined angle of divergence. The diffracted +1 diffracted light is formed on the disc 10b having a relatively large thickness.

The objective lens 15 allows the light emitted from the first light source 21 and the second light source 31 to be connected to the recording surface of the disc 10. At this time, the light emitted from the first light source 21 and the light emitted from the second light source 31 form light spots at different positions.

As described above, the compatible optical pick-up apparatus provided can be used even when a CD-R is adopted as the recording medium by using two wavelengths. However, since it includes the hologram element in which the diffraction pattern is formed for the predetermined area, it is the same as that using the substantially doublet lens, so that the assembly and the optical arrangement are difficult. Also, there is an advantage of using one photodetector, but it is difficult to assemble two optical beams having different wavelengths because the optical axis alignment of the photodetector is required at the same time.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a compatible optical pickup apparatus which can adopt a disc having a different format and which has a simple structure.

According to an aspect of the present invention, An objective lens for focusing the light emitted from the light source onto the recording surface of the recording medium; A photodetector for receiving the light reflected from the recording medium and detecting an information signal and an error signal; And a light path changing means disposed on an optical path between the light source and the objective lens for changing the path of light incident thereon, the optical pickup device comprising: a light source for generating and emitting laser light of a predetermined wavelength range A first light source (21); And a second light source (31) for generating and outputting a laser beam of a different wavelength region from the first light source (21), wherein the light beam emitted from the first light source and transmitted through the recording medium and the light path changing means A first photodetector for receiving light incident via the first photodetector; And a second photodetector which is emitted from the second light source and receives the light incident through the recording medium and the light path changing means.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3 is a schematic view showing an optical arrangement of a compatible optical pickup device according to the first embodiment of the present invention.

As shown in the figure, the compatible optical pickup device includes a light source for generating and emitting laser light, an objective lens 41 for connecting the light emitted from the light source to the recording surface of the recording medium, And a photodetector for detecting an information signal and an error signal by receiving light.

The light source includes a first light source 51 that generates and emits light in a wavelength region, for example, approximately 650 nm, suitable for a recording medium 10 having a relatively thin disk 10a such as a DVD or a DVD-ROM, And a second light source 61 for generating a light in a wavelength region, for example, approximately 780 nm, which is suitable for a CD family, in particular, CD-R, which is a disk 10b having a relatively thick thickness as the recording medium 10. Here, the first light source 51 and the second light source 61 are disposed on different optical paths, and are selectively driven according to the type of the disc 10 employed as the recording medium. The driving mechanism of the first light source 51 and the second light source 61 may be a manual mode in which the user selects the recording medium 10 in accordance with the type of the employed recording medium 10, , And it is widely known, so a detailed description thereof will be omitted.

The objective lens 41 is a member that focuses the light emitted from the light source to form a light spot on the recording medium 10 and is mounted on an actuator (not shown) to correct focus and track error . The objective lens 41 may be machined such that its spherical surface is suitable for any one of recording media having different thicknesses, and may be manufactured by the present applicant in Korean Patent Application No. 95-31679 (an objective lens device and a stabilized focus servo signal A method of discriminating discs having different thicknesses, a method of reproducing and recording information from discs having different thicknesses, and a method of producing lenses), and Korean Patent Application No. 96-13918 And an optical pickup apparatus employing this objective lens apparatus) can be employed.

In addition, the photodetector includes a first photodetector 57 and a second photodetector 69. The first photodetector 57 emits light from the first light source 51 and receives light incident via the recording medium 10 and the optical path changing means. The second photodetector 69 emits light from the second light source 61 and receives light incident via the recording medium 10 and the optical path changing means. The first and second photodetectors 57 and 69 are formed of at least two divisional plates. The first and second photodetectors 57 and 69 receive the signals converted by the division plates and converted into the current signals by differential or sum-amplification, , Track error signal and focus error signal.

And three beam splitters 53, 63 and 65 as the optical path changing means. The first beam splitter 53 is disposed on the optical path between the first light source 51 and the objective lens 41 and transmits and / or reflects the light emitted from the first light source 51, So that the light incident on the side of the recording medium 10 is directed to the first photodetector 57. In this case, The first beam splitter 53 divides incident light into a predetermined ratio, passes the beam partially, and reflects the remaining beams. As shown in the drawing, the first beam splitter 53 is preferably used as a flat plate, and the triplet prisms may be connected to each other, that is, a cubic type. In the case where the first beam splitter 53 is employed as a flat plate, the optical arrangement of the first light source 51 and the first photodetector 57 is determined in consideration of astigmatism as shown in FIG. 3 . On the other hand, when the first beam splitter 53 is employed in a cubic configuration, the optical positions of the first light source 51 and the first optical detector 57 may be arranged as shown in FIG. 3 However, they can be arranged to be replaced with each other.

The second beam splitter 63 is disposed on the optical path between the first beam splitter 53 and the objective lens 41 and reflects the light emitted from the second light source 61, 41, and transmits the light incident from the recording medium 10 side. The third beam splitter 65 is disposed on the optical path between the first beam splitter 53 and the second beam splitter 63 and is emitted from the second light source 61, And the light beam transmitted through the second beam splitter 63 is directed to the second photodetector 69. In this way, Each of the first, second, and third beam splitters 53, 63, and 65 may be coated to selectively transmit or reflect light in a predetermined wavelength region.

Here, the second beam splitter 63 and the third beam splitter 65 may be formed in a cubic shape as well as a flat plate shape as shown in the figure. In the case where the second beam splitter 63 and the third beam splitter 65 are of a flat plate type, when the light emitted from the first light source 51 passes through the two beam splitter 63 and 65 ) Should not cause astigmatism. To this end, the second beam splitter 63 and the third beam splitter 65 are positioned in their optical configuration, tilted in opposite directions so as to cancel the astigmatism from each other. Preferably, the slope of the second beam splitter 63 differs from the slope of the third beam splitter 65 by 180 degrees.

A collimating lens 45 may be further provided on the optical path between the objective lens 41 and the second beam splitter 63. And the first light source 51 is positioned at a focal position of the collimating lens 45. Therefore, the light emitted from the first light source and passing through the collimating lens 45 becomes parallel light. On the other hand, the second light source is disposed at a position that is out of focus of the collimating lens 45, that is, shorter than the focal distance. Therefore, the light emitted from the second light source 61 and passing through the collimating lens 45 is diverged as light near to parallel light as in A. The reason why the light emitted from the second light source 61 and passed through the collimating lens 45 is used as the divergence angle is that when the objective lens is manufactured so as to fit the disk 10a having a relatively small thickness To suppress generation of spherical aberration depending on the wavelength of the light source used and the thickness difference of the recording medium.

Light emitted from the first light source 51 and passing through the collimating lens 45 and the objective lens 41 is condensed on a relatively thin recording medium 10a and emitted from the second light source 61 The light passing through the collimating lens 45 and the objective lens 41 is formed on the recording medium 10b having a relatively large thickness.

A first sensor lens 55 is provided on the optical path between the first beam splitter 53 and the first photodetector 57 to adjust the focus position of the light incident on the first photodetector 57, May be further included. In this way, the optical arrangement of the first photodetector 57 can be facilitated by further including the first sensor lens 55. In addition, the first sensor lens 55 adjusts the curvature so that the longitudinal focal position and the lateral focal position of the light passing through the first sensor lens 55 are different, causing astigmatism. Therefore, the first photodetector 57 can detect the focus error signal by the astigmatism method.

A second sensor lens 67 may further be provided on the optical path between the third beam splitter 65 and the second photodetector 69. The structure and function of the second sensor lens 67 are substantially the same as those of the first sensor lens 55. [

Referring to FIG. 4, a compatible optical pickup device according to a second embodiment of the present invention will be described.

As shown in the figure, the compatible optical pickup apparatus according to the second embodiment of the present invention is substantially the same as the compatible optical pickup apparatus according to the first embodiment described with reference to FIG. However, in the optical configuration, the optical position of the second beam splitter 63 and the third beam splitter 65 is changed. Members using the same reference numerals as those of the third embodiment are the same or similar members to those of the third embodiment, and detailed description thereof will be omitted.

The second beam splitter 63 is disposed on the optical path between the first beam splitter 53 and the objective lens 41 and reflects the light emitted from the second light source 61 to form the objective lens 41 , And transmits the light incident from the recording medium 10 side. The third beam splitter 65 is disposed on the optical path between the objective lens 41 and the second beam splitter 63 and receives the light incident from the first light source 51 and the second light source 61 And reflects the light emitted from the second light source 61 and reflected by the recording medium 10 to convert the path of the light toward the second photodetector 69.

The second beam splitter 63 and the third beam splitter 65 are formed in a cubic shape as shown in the figure so that the shape of the light emitted from the second light source 61 is not deformed by the astigmatism desirable.

Referring to FIG. 5, a compatible optical pickup device according to a third embodiment of the present invention will be described.

As shown, the compatible optical pickup apparatus according to the third embodiment of the present invention is substantially the same as the compatible optical pickup apparatus according to the first embodiment described with reference to FIG. In the optical arrangement, however, the optical position of the second beam splitter 63 is changed, and the role of the third beam splitter 65 is partially changed. Here, the same reference numerals as in the third embodiment are used The members which are the same or similar to those of the third embodiment are not described in detail.

The third beam splitter 65 is disposed on the optical path between the first beam splitter 53 and the objective lens 41 and reflects the light emitted from the second light source 61, And reflects light incident from the recording medium 10 side. The second beam splitter 63 is disposed on the optical path between the second light source 61 and the third beam splitter 65 and transmits or receives light incident from the third beam splitter 65. [ Or guided to the second photodetector (69).

It is preferable that the first, second and third beam splitters 53, 63 and 65 are provided in a flat plate shape as shown in FIG. At this time, the first beam splitter 53 and the third beam splitter 65 are arranged symmetrically with respect to each other at the slope. The first light source 51 is disposed on the optical axis of the objective lens 41 so that light generated and emitted from the first light source 51 is transmitted through the first beam splitter 53 and converged on the recording medium 10, .

The first, second, and third beam splitter 53, 63, and 65 may be formed in a cubic shape as well as a planar shape as mentioned above.

Referring to FIG. 6, a compatible optical pickup device according to a fourth embodiment of the present invention will be described.

As shown in the figure, a first light source 51 and a second light source 61 having different wavelengths from each other and a light source 51, which emits light from each of the two light sources 51 and 61 via the recording medium 10, And an objective lens 41 for converging the light emitted from the two light sources 51 and 61 onto the recording surface of the recording medium 10. The first optical detector 57 and the second optical detector 69, .

The compatible optical pick-up apparatus according to the fourth embodiment of the present invention is substantially the same as the compatible optical pick-up apparatus according to the first embodiment described with reference to FIG. 3, The first light source 51 and the first photodetector 57 and / or the second light source 61 and the second photodetector 69 are formed by the integrated modules 70 and 80, respectively.

In the case where the first light source 51 and the first photodetector 57 are formed of the integral first module 70, the first beam splitter 53 as shown in FIGS. Adoption is unnecessary. In the case where the second light source 61 and the second photodetector 69 are formed by the integrated second module 80, as shown in FIGS. 3 to 5, the third beam splitter 65 ) Is unnecessary. Therefore, the optical path changing means includes at least one beam splitter 47, and by removing the first beam splitter 53 and / or the third beam splitter 65, the structure of the optical system can be simplified, The efficiency can be increased.

At this time, it is preferable that the beam splitter 47 is provided in a flat plate shape. In the case where the flat plate type beam splitter 47 is employed, the integral first module 70 will be described with reference to FIG.

A housing 72 having a substrate 71 and an emission window 73 surrounding the substrate 71 and a hologram element 74 provided in the emission window 73 as shown in FIG.

The substrate 71 is provided with a first light source 51 and a first photodetector 57 on the upper surface thereof. When the edge light emitting laser is employed as the first light source 51, the first light source 51 is coupled to the substrate 71 via the mount 75. The housing 72 functions to protect the first light source 51 and the first photodetector 57. The integrated first module 70 also includes a plurality of leads 76 formed through the substrate 71 for driving the first light source 51 and the first photodetector 57 . The hologram element 74 emits light from the first light source 51 and enters the first photodetector 57 via the objective lens (FIG. 41) and the recording medium (FIG. 10) . Since the hologram element 74 is widely known, detailed description thereof will be omitted. The hologram element 74 is inclined at a slope of a symmetrical shape with respect to the slope of the planar beam splitter 47. By inclining in this manner, it is possible to prevent the light emitted from the first light source 51 and incident on the recording medium 10 from being distorted.

FIG. 8 is a cross-sectional view showing a second module 80 integrated with a cigarette integrating the second light source 61 and the second photodetector 69; The integrated second module 80 has a structure in which a second light source 61 and a second photodetector 69 are provided in place of the first light source 51 and the first photodetector 57, The first module 70 is substantially the same as the first module 70 except that the device 74 is disposed perpendicular to the traveling direction of the light emitted from the second light source 61. Therefore, the description thereof will be omitted.

Here, the members having the same reference numerals as those of the third embodiment are the same or similar to those of the third embodiment, and a detailed description thereof will be omitted.

Referring to FIG. 9, a compatible optical pickup device according to a fifth embodiment of the present invention will be described.

As shown in the figure, a first light source 51 and a second light source 61 having different wavelengths from each other and a light source 51, which emits light from each of the two light sources 51 and 61 via the recording medium 10, And an objective lens 41 for converging the light emitted from the two light sources 51 and 61 onto the recording surface of the recording medium 10. The first optical detector 57 and the second optical detector 69, .

The compatible optical pick-up apparatus according to the fifth embodiment of the present invention is substantially the same as the compatible optical pick-up apparatus according to the third embodiment substantially described with reference to FIG. 5, and in order to simplify its optical configuration, And the second light source 61 and the second photodetector 69 are formed by the integrated module 80. Here, the first light source 51, the first beam splitter 53, the first photodetector 57 and the first sensor lens 55 have functions, structures, and optical arrangements as shown in FIG. 5 And is the same as that described with reference to the third embodiment, a detailed description thereof will be omitted. In this way, it is preferable that the employed beam splitter 47 (53) is provided in a flat plate shape and is inclined so as to be symmetrical to each other.

As described above, the compatible optical pickup device includes two light sources for emitting light of different wavelengths, that is, a first light source and a second light source, It is possible to fundamentally prevent the data from being destroyed during reproduction of the information recorded on the CD-R made up of the family, particularly the organic dye recording layer. In addition, by using two light sources selectively, it is possible to extend the life of a device employing the compatible optical pickup device. By using two photodetectors, it is easy to arrange the optical pickup device optically.

Claims (7)

A first light source for emitting light of a predetermined wavelength; A second light source for emitting light having a wavelength different from that of the light emitted from the first light source; An objective lens for focusing the light emitted from the first and second light sources onto a recording medium; A first photodetector for receiving the light emitted from the first light source and reflected by the recording medium; A second photodetector for receiving the light emitted from the second light source and reflected by the recording medium; Wherein the first light source is disposed on an optical path between the first light source and the objective lens so as to transmit and / or reflect light emitted from the first light source toward the objective lens, A first beam splitter for converting the traveling path thereof toward the detector; A second beam splitter disposed on an optical path between the first beam splitter and the objective lens for reflecting the light emitted from the second light source to be directed toward the objective lens and for converting the path of light incident on the recording medium side, Wow ; A third beam splitter disposed on an optical path between the recording medium and the second photodetector, the third beam splitter converting the path of the light so that the light incident on the recording medium side is directed to the second photodetector; Wherein the optical pickup device comprises: The optical pickup apparatus according to claim 1, wherein the second beam splitter is arranged to reflect light emitted from the second light source to be directed toward the objective lens, and transmit the light incident on the recording medium side, Is arranged on the optical path between the first and second beam splitter and is arranged so that the light emitted from the second light source and transmitted through the recording medium to the second beam splitter is directed to the second photodetector And the optical path changing means is adapted to change the optical path. The optical pickup apparatus according to claim 1, wherein the second beam splitter is arranged to reflect light emitted from a second light source to be directed toward the objective lens, and transmit light incident on the recording medium side, and the third beam splitter And a second beam splitter which is disposed on an optical path between the objective lens and the second beam splitter and transmits the incident light through the first light source and the second light source and reflects the light emitted from the second light source, And the optical path of the light is changed so as to be directed toward the second optical detector. The optical pickup apparatus according to claim 1, wherein the second beam splitter is arranged to reflect light emitted from a second light source to be directed toward the objective lens, and to reflect light incident on the recording medium side, and the third beam splitter And the second beam splitter transmits and / or reflects the light incident on the second beam splitter to guide the light to the second photodetector. 5. The objective lens of any one of claims 1 to 4, further comprising: a collimating lens for collimating the divergent light incident on the optical path between the first light source and the second light source and the objective lens into parallel light or near- Wherein the optical pickup device further comprises a lens. 6. The objective lens of claim 5, wherein the second light source is positioned within a focal length of the collimating lens so that light emitted from the second light source and passing through the collimating lens is directed to the objective lens with a predetermined divergence angle Wherein the optical pickup device comprises: The apparatus according to any one of claims 1 to 4, further comprising a first sensor lens capable of adjusting a focus position of light incident on the first photodetector on a front optical path of the first photodetector Wherein the optical pickup device comprises: