KR19990066270A - 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 substrate; A light source having a first and a second surface light laser disposed adjacent to each other on the substrate and emitting light having different emission angles and wavelengths; An objective lens for focusing the light emitted from the light source to the recording surface of the recording medium; A main photodetector disposed on the substrate, the main photodetector receiving light reflected from the recording medium to detect an information signal and an error signal; It is provided on the optical path between the light source and the objective lens, and has a transparent member having a predetermined thickness and a hologram element formed on the side of the objective lens of the transparent member to diffract and transmit the light incident from the objective lens toward the photodetector. One optical element; characterized in that it is provided.

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.

FIG. 3 is a schematic configuration diagram illustrating the embodiment of the light source shown in FIG. 2.

FIG. 4 is a schematic diagram illustrating an embodiment of the photodetector shown in FIG. 2. FIG.

FIG. 5 is a schematic configuration diagram illustrating another embodiment of the photodetector illustrated in FIG. 2.

<Description of Symbols for Main Parts of Drawings>

10 ... Recording medium 41 ... Substrate 43 ... Photodetector for monitor

45 ... main photodetector 47 ... barrier plate 50 ... first surface optical laser

51, 61 ... lower electrode layer 52, 62 ... windows 53, 63 ... lower reflector layer

55, 65 ... active layer 57, 67 ... upper reflector layer

59, 69 ... upper electrode layer 60 ... second surface optical laser

70 Optical element 71 Transparent member 73 Grating

75 Hologram element 77 Reflector 81 Collimating lens

83.Objective lens

A compatible optical pickup device according to the present invention for achieving the above object, the substrate; A light source disposed adjacent to each other on the substrate and having first and second surface light lasers emitting light having different radiation angles and wavelengths; An objective lens for focusing light emitted from the light source to a recording surface of a recording medium; A main photodetector disposed on the substrate, the main photodetector receiving light reflected from the recording medium to detect an information signal and an error signal; Disposed on an optical path between the light source and the objective lens, the transparent member having a predetermined thickness and formed on the objective lens side of the transparent member to diffract and transmit light incident from the objective lens toward the photodetector; And an optical device having a hologram element.

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 an exemplary embodiment of the present invention includes a substrate 41, a light source 40 installed on the substrate 41, and light emitted from the light source 40. An objective lens 83 for focusing the recording surface of the recording medium 10 and a main photodetector disposed on the substrate 41 to receive information reflected from the recording medium 10 to detect information signals and error signals. 45 and an optical element 70 disposed on an optical path between the light source 40 and the objective lens 83.

2 and 3, the light sources 40 are disposed adjacent to each other on the substrate 41 and emit light having different emission angles and wavelengths from the first and second surface light lasers 50 ( 60). In general, the surface light laser emits light in a stacking direction of the semiconductor material layer, thereby facilitating a structural arrangement. Here, since the size of the first and second surface light laser (50, 60) is within a few tens of micrometers (㎛), the aberration caused by the light emitted from different positions is not a big problem.

The first surface light laser 50 emits red light having a wavelength of approximately 635 to 650 nm so as to be suitable for DVD, DVD-ROM, and the like, which are relatively thin disks 10a. The second surface light laser 60 emits infrared light having a wavelength of 780 nm so as to be suitable for the CD family, particularly CD-R, which is a relatively thick disk 10b.

Each of the first and second surface optical lasers 50 and 60 is sequentially stacked on the substrate 41 with lower electrode layers 51 and 61, lower reflector layers 53 and 63, and active layer 55, respectively. 65), upper reflector layers 57 and 67, and upper electrode layers 59 and 69. The lower reflector layers 53 and 63 and the upper reflector layers 57 and 67 contain impurities. Al _x Ga _1-x As Semiconductor compounds such as Ga As The compound which consists of etc. is laminated | stacked alternately several to several tens of layers. However, the lower reflector layers 53 and 63 and the upper reflector layers 57 and 67 are made of different types of impurity semiconductor materials. For example, the lower reflector layers 53 and 63 may be n-type semiconductor materials, and the upper reflector layers 57 and 67 may be p-type semiconductor materials, or vice versa.

Each of the lower reflector layers 53, 63 and the upper reflector layers 57, 67 99% It has the above high reflectance and reflects most of the light generated in the active layers 55 and 65 and transmits a very small part of the light.

Each of the lower electrode layers 51 and 61 and the upper electrode layers 59 and 69 is made of a metal having excellent electrical conductivity. Positive voltages are applied to the upper electrode layers 59 and 69 from an external power source with respect to the lower electrode layers 51 and 61.

The upper electrode layers 59 and 69 are provided with windows 52 and 62 which are generated by the active layers 55 and 65 and emit laser light transmitted through the upper reflector layers 57 and 67. Here, the light L1 emitted from the first surface light laser 50 has a larger radiation angle than the light L2 emitted from the second surface light laser 60. That is, since the emission angle of the emitted light is inversely proportional to the diameter of the windows 52 and 62, the diameter of the window 52 of the first surface light laser 50 is the window of the second surface light laser 60. It is formed smaller than the diameter of (62).

The first and second surface optical lasers 50 and 60 are manufactured by the same manufacturing process, and the two surface optical lasers 50 and 60 are electrically insulated by the blocking plate 47 interposed therebetween. .

The objective lens 83 is mounted and driven in an actuator (not shown) to correct focus error and track error. By the spherical aberration, the objective lens 83 focuses the incident light so that the focal position of the light incident on the paraxial region and the focal position of the light incident on the circular axis region are different. Accordingly, light L1 having a large emission angle emitted from the first surface optical laser 50 is focused while passing through the optical element 70 and passing through the axial region of the objective lens 83 so that its thickness is relatively high. It forms on the thin disk 10a. On the other hand, the light L2 emitted from the second surface optical laser 60 has a small emission angle, and is transmitted through the optical element 70 and focused while passing through the paraxial region of the objective lens 83 to have a relatively thick thickness. It forms on the thick disk 10b.

Here, the collimating lens 81 may be further provided between the optical element 70 and the objective lens 83 so that the light irradiated from the light source 40 is incident on the objective lens 83 in parallel.

The optical element 70 is disposed on an optical path between the light source 40 and the collimating lens 81, and has a transparent member 71 having a predetermined thickness and the objective lens of the transparent member 71. A hologram element 75 formed on one side of the surface 83 to diffract and transmit light incident from the objective lens 83 toward the main photodetector 45, and the light source 40 of the transparent member 71. And a grating 73 formed on the side opposite the. The hologram element 75 linearly transmits light incident from the light source 40 and diffracts the light incident from the disk 10 to convert the path of the light. The thickness of the transparent member 71 is designed in consideration of the optical width between the hologram element 75 and the grating 73.

Here, the main photodetector 45 is disposed on the substrate 41 to receive the light diffracted by the hologram element 75.

The grating 73 diffracts and transmits the light irradiated to the light source 40 with a 0 th order beam, a ± 1 st order beam, ..., so that the track error signal can be detected by the 3-beam method.

On the other hand, a part of the surface facing the light source 40 of the optical element 70 reflecting member 77 for reflecting a part of the light irradiated from the light source 40 toward the monitor photodetector 43 which will be described later ) Is preferably further provided. The reflective member 77 may be formed by coating the optical device 70.

The monitor photodetector 43 is installed on the substrate 41 around the light source 40, and receives the light reflected from the reflective member 77 to detect the amount of light emitted from the light source 40. do.

The main photodetector 45 receives the light reflected from the recording medium 10 and diffracted through the hologram element 75 to receive the focus error signal for each of the two disks 10a and 10b having different thicknesses, The track error signal and the information signal (RF signal) are detected. For this purpose, the main photodetector 45 preferably has a structure as shown in FIGS. 4 and 5, respectively.

As shown in Fig. 4, the main photodetector 45 is divided into ten. Here, reference numeral 46 denotes a photodetector structure having an array of 2x4 structures, and reference numerals 47 and 48 each represent a photodetector structure provided around the photodetector structure having the 2x4 array to detect a track error signal. The structure is shown.

When a relatively thin disk 10a is employed as the recording medium, the light irradiated from the first surface light laser 50 is used as the effective light. At this time, the 0th order beams for detecting the information signal and the focus error signal are received on the partition plates A, B, C, and D of the main photodetector 45, and the track error signals are detected on the partition plates I, J, respectively. ± 1st order beams are received.

Accordingly, in the case of the disk 10a, the focus error signal FES, the track error signal TES, and the information signal RFS may be represented by Equation 1 below.

FES = (A + C)-(B + D)

TES = I-J

RFS = A + B + C + D

On the other hand, when the relatively thick disk 10b is employed as the recording medium, the light irradiated from the second surface light laser 60 is used as the effective light. At this time, the 0th order beams for detecting the information signal and the focus error signal are received on the partition plates E, F, G, and H of the main photodetector 45, and the track error signals are detected on the partition plates I, J, respectively. ± 1st order beams are received. Here, the ± first order beam received by the divider is received at a position different from the ± first order beam of the disk 10a having the above thickness.

In this case, the focus error signal FES ', the track error signal TES', and the information signal RFS 'may be represented by Equation 2.

FES '= (E + G)-(F + H)

TES '= I-J

RFS = E + F + G + H

In addition, the main photodetector 45 may be divided into eight, as shown in FIG. Here, reference numeral 46 'denotes a photodetector structure having an array of 2x3 structures.

When a relatively thin disk 10a is employed as the recording medium, the light irradiated from the first surface light laser 50 is used as the effective light. At this time, the 0th order beams capable of detecting the information signal and the focus error signal are received on the split plates A, B, E, and F of the main photodetector 45, and the track error signals are detected on the split plates G, H, respectively. ± 1st order beams are received.

Therefore, in the case of the disk 10a, the focus error signal FES, the track error signal TES, and the information signal RFS may be represented by Equation 3 below.

FES = (A + E)-(B + F)

TES = G-H

RFS = A + B + E + F

On the other hand, when the relatively thick disk 10b is employed as the recording medium, the light irradiated from the second surface light laser 60 is used as the effective light. At this time, the 0th order beams capable of detecting the information signal and the focus error signal are received by the partition plates B, C, D, and E of the main photodetector 45, and the track error signals are detected by the partition plates G, H, respectively. ± 1st order beams are received.

In this case, the focus error signal FES ', the track error signal TES', and the information signal RFS 'may be represented by Equation 4.

FES '= (B + D)-(C + E)

TES '= G-H

RFS = B + C + D + E

As such, in the case of the eight-part partition, the partitions B and E are shared for two disks having different thicknesses.

Hereinafter, an operation of the compatible optical pickup apparatus according to an exemplary embodiment of the present invention will be described with reference to FIG. 2 as an example in which a relatively thin disk 10a such as a DVD is employed. In this case, the light irradiated from the first surface light laser 50 uses the effective light. That is, the divergent light emitted from the first surface light laser 50 is diffracted into at least three beams while passing through the grating 73. The diffracted beam passes straight through the hologram element 75 and then becomes parallel light while passing through the collimating lens 83. This parallel light passes through the circular axis region of the objective lens 83 and forms on the relatively thin disk 10a, and is reflected back toward the objective lens 83. The reflected light passes through the objective lens 83 and the collimating lens 83, and is then diffracted by the hologram element 75 and received by the main photodetector 45. The main photodetector 45 is composed of 10 divisions or 8 divisions, and independently converts light received at each partition plate. On the other hand, the light irradiated from the first surface light laser 50 and reflected from the reflective member 77 is received by the monitor photodetector 43 provided on the substrate 1. Since the output light amount of the first surface light laser 50 can be known from the received light signal, the light output of the first surface light laser 50 can be controlled based on this.

On the other hand, when the relatively thick disk 10b is employed as the recording medium, the second surface optical laser 60 is used as the light source and another partition plate of the main photodetector 45 is used. Since the disc 10a is different from the case where the recording medium is employed as the recording medium, the detailed description thereof will be omitted.

As described above, the compatible optical pickup device according to the present invention employs two surface optical lasers having different radiation angles as a light source, an optical element in which a hologram element and a grating are integrally formed, and an 8-division or 10-divided main photodetector. By adopting this, the number of parts can be reduced, the structure can be simplified, and the size can be reduced.

Claims (8)

A substrate; A light source disposed adjacent to each other on the substrate and having first and second surface light lasers emitting light having different radiation angles and wavelengths; An objective lens for focusing light emitted from the light source to a recording surface of a recording medium; A main photodetector disposed on the substrate, the main photodetector receiving light reflected from the recording medium to detect an information signal and an error signal; Disposed on an optical path between the light source and the objective lens, the transparent member having a predetermined thickness and formed on the side of the objective lens of the transparent member to diffract and transmit light incident from the objective lens toward the photodetector; Optical device having a hologram element; Compatible optical pickup device comprising a. The method of claim 1, wherein each of the first and second surface light lasers A lower electrode layer stacked on the substrate; A lower reflector layer formed on the lower electrode layer and made of a semiconductor material containing a plurality of impurities; An active layer formed on the lower reflector layer and generating laser light; An upper reflector layer formed on the active layer and made of a plurality of impurity semiconductor materials of a semiconductor type different from the lower reflector layer; And And an upper electrode layer formed on an upper surface of the upper reflector layer, the upper electrode layer having a window through which light generated by the active layer is emitted. 2. The compatible optical pickup apparatus of claim 1, further comprising a blocking plate interposed between the first surface laser and the second surface laser to electrically insulate them. The laser beam of claim 1, wherein the first surface light laser emits light having an infrared wavelength, and the second surface light laser emits light having a red wavelength. The window of the first surface light laser is smaller than the window of the second surface light laser so that the emission angle of the light emitted from the second surface light laser is smaller than that of the light emitted from the first surface light laser. Compatible optical pickup device characterized in that. The optical device according to any one of claims 1 to 4, wherein the optical element is And a grating formed on a surface of the transparent member facing the light source to diffract and transmit incident light. The light emitting apparatus according to any one of claims 1 to 4, further comprising: a reflection member disposed on a portion of the transparent member facing the light source and reflecting a part of the light emitted from the light source; And a monitor photodetector provided on the substrate around the light source to receive the light reflected from the reflective member and detect the amount of light emitted from the light source. The method of claim 1, wherein the main photodetector, Eight split plates each having a 2 × 4 array structure for photoelectric conversion independently so as to detect focus error signals and information signals for recording media having different thicknesses; And two partition plates provided around the partition plates of the 2x4 array structure so as to detect a track error signal for the recording medium. The method of claim 1, wherein the main photodetector, Six partition plates each having a 2 × 3 array structure for photoelectric conversion independently so as to detect focus error signals and information signals for recording media having different thicknesses; And two partition plates provided around the partition plates of the 2x3 array structure so as to detect a track error signal for the recording medium.