KR20000028508A - Optical pick-up device - Google Patents

Abstract

PURPOSE: An optical pick-up device is provided to minimize a number of optical means by receiving an optical beam with a different wavelength using one light receiving element. CONSTITUTION: A luminous diode(1) emits an optical beam having a 650nm wavelength. A complex type hologram(100) emits an optical beam having a 780nm wavelength and receiving an optical beam having 650nm and 780nm optical beams. A polarization beam splitter(20) changes a penetrating path of an optical beam according to a direction of an incident optical beam. A collimator lens(40) converts the incident optical beam into a horizontal light. A focus lens(30) collect the horizontal light as an optical spot to a recording surface of an optical disk.

Description

Optical pickup device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup apparatus used for a plurality of disk series. More particularly, the present invention relates to a plurality of disk series by receiving light beams having different wavelengths corresponding to a plurality of modes using one light receiving element. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup apparatus which can be miniaturized by minimizing the number of optical means for forming light emission and light receiving paths of light beams having a plurality of wavelengths provided in the optical pickup apparatus.

Read-only CDs (hereinafter referred to as "normal CDs"), which are general optical disks, have a pitch between tracks of 1.6 mu m and a length of the pits in the tracks of 0.9 mu m- The digital multi-function disc (DVD: Digital Video Disc, hereinafter referred to as 'DVD') has a pitch between tracks of 0.87 mu m and a pit length of 0.4 mu m to 1.87 mu m. Accordingly, although the optical beams used for the general CD and the DVD are required to have optimal optical wavelengths of 780 nm and 650 nm, respectively, in general, in an optical pickup apparatus for recording / reproducing a combination of a general CD and a DVD, a 650 nm laser diode The recording / reproducing operation of the two types of optical discs (normal CD and DVD) was performed using only one (LD).

By the way, since a recordable CD (CD-R) or a rewritable CD (CD-RW) for changing a crystal structure of an optical disc medium and recording a signal is manufactured to be used only for a light beam of 780 nm, a general CD and a DVD can be used. The optical pickup apparatus used for the present invention includes a laser diode of 780 nm for recording or reproducing a signal on a CD (CD, CD-R, CD-RW), and a 650 nm for recording or reproducing a signal on a DVD (DVD). All of the laser diodes are provided, and recording / reproducing operations are performed by using corresponding laser diodes according to the type of optical disk.

In the conventional optical pickup apparatus, as shown in Fig. 1, a light beam having a specific wavelength range (780 nm or 680 nm) is emitted to form an optical spot on the recording surface of the optical disc, and the reflected light of the formed optical spot is reflected. Respective hologram pick-up modules (HPM) 10, 11 for receiving and converting them into electric signals; A polarization beam splitter (PBS) 20 for changing a transmission path of the light beam according to the direction of the incident light beam; A collimator lens 40 for converting and outputting the incident light beam into horizontal light; And a focus lens 30 for condensing the converted horizontal light into a light spot on the recording surface of the optical disk.

On the other hand, the hologram pickup module (HPM), the light emitting diode (LD) for generating a light beam having a specific wavelength range, and the light beam generated from the light emitting diode is incident to the optical disk, and reflected from the optical disk A hologram for distributing a light beam according to a formed pattern and a photo diode (PD) for receiving an optical beam and converting the light beam into electrical signals according to the distribution characteristics of the hologram are integrated.

In the conventional optical pickup apparatus configured as described above, when the optical disk is a CD, the light beam emitted from the laser diode emitting the light beam of 780 nm is shown through one grating plate as shown in FIG. 2A. After being separated into a main beam and two sub beams, the 780 nm hologram is transmitted and output from the hologram pickup module 10.

The light beam output as described above is incident to the polarization beam splitter 20, and the incident light beam is transmitted to the collimator lens 40 and then converted into horizontal light. The converted horizontal light is condensed by the focus lens 30, thereby forming light spots having a diameter of 1 탆 or less on the recording surface of the optical disk. The light spot formed as described above is reflected from the optical disk and undergoes the reverse process as described above, and is inputted into the hologram pickup module 10 and then partitioned each region of the 780 nm light receiving diode through the 780 nm hologram (a Separately incident and separated into b, c, e, and f, the electric signals A, B, C, E, and F are photoelectrically converted from the respective areas to be separated and output.

That is, AB is used as a focus error signal and EF is a tracking error signal among the separated output signals, and electrical signals A, B, and C in the a, b, and C regions passing through the hologram are summed to generate a high frequency component. Is reproduced and output as an RF signal.

On the other hand, when the optical disk is a DVD, the 650 nm light beam generated from the hologram pickup module 11 of Figure 2b is transmitted from the hologram pickup module 11 through the 650 nm hologram and the polarization beam splitter 20 Incident to the collimator lens 40, the light is sequentially transmitted through the collimator lens 40, and then converted into horizontal light. The converted horizontal light having different wavelengths is condensed by the focus lens 30, thereby forming a light spot having a diameter of 1 μm or less on the recording surface of the optical disc, and the light spot formed as described above is reflected from the optical disc, The electric signals input into the hologram pickup module 11 and corresponding to the amount of light detected from each of the partitioned areas a, b, c, d of the 650 nm light-receiving diode via the 650 nm hologram are A, B, C. The focus error signal corresponds to AB, the tracking error signal corresponds to a phase difference between C and D, and the high frequency signal corresponds to A + B + C + D.

However, the 650 nm hologram pickup module used when the optical disk is a DVD is complicated and difficult to manufacture, and is only sold by a specific company (eg, Sharp), which is very exclusive and expensive. .

Accordingly, FIG. 3, which is another conventional optical pickup apparatus equipped with a hologram pickup module, does not use the expensive 650 nm hologram pickup module shown in FIG. A light-receiving diode was used in place, and a rotatable translucent mirror 50 to prevent astigmatism from occurring, and a transparent plate 60 to compensate for a light path changed according to the rotation angle of the translucent mirror 50. It was configured to include more.

In the operation of the optical pickup device configured as described above, first, the light beam generated from the 650 nm light emitting diode 1 is changed by the polarization beam splitter 20 to be incident on the translucent mirror 50, and the translucent mirror 50 is applied. The light beam incident on the mirror 50 passes through the collimator lens 40 and the focus lens 30 in order to form light spots on the recording surface of the optical disk (ie, DVD). The light spot is reflected from the optical disk and passes through the focus lens 30 and the collimator lens 40 in turn, and then passes through the translucent mirror 50 and the transparent plate 60 to the 650 nm light-receiving diode 2. Will be incident.

However, by replacing the expensive 650 nm hologram pickup module as described above, the optical pickup device of FIG. 3 using each of the 650 nm light emitting diodes and the light receiving diodes, as the number of optical components to be additionally added, increases, When the path of the light beam is longer and the transmission of each optical part, the amount of light is reduced, the optical efficiency is extremely reduced, and the tolerance (error for the minimum separation distance between the optical parts) to be considered in the arrangement of the optical parts is limited. Since the signal interference is generated between each of the adjacent optical parts because it is not secured more than a value, the operation of the optical pickup device becomes unstable.

Accordingly, the present invention has been made to solve the above problems, and includes a light receiving device capable of receiving a light beam having a plurality of wavelengths, a light emitting device emitting light beams having any one of the plurality of wavelengths; It is an object of the present invention to provide an optical pickup apparatus that integrates and minimizes optical means required for light emission and light receiving path formation.

1 is a block diagram of a conventional optical pickup using a hologram pick-up module (HPM),

Figure 2a shows the internal structure of the hologram pickup module for a normal CD (read only CD),

Figure 2b shows the internal structure of the hologram pickup module for DVD (DVD),

Figure 3 is a block diagram of another conventional optical pickup device using one hologram pickup module,

Figure 4 illustrates the configuration of an embodiment in which the optical pickup device according to the present invention is applied to the hologram pickup module,

Figure 5 shows the internal structure of the hologram pickup module according to the present invention,

FIG. 6 illustrates light receiving characteristics of the light emitting diode of FIG. 5.

Figure 7 shows the configuration of another embodiment in which the optical pickup device according to the present invention is applied to the hologram pickup module.

※ Explanation of code for main part of drawing

1: Light emitting diode (LD) 2: Light receiving diode (PD)

10,11: hologram pickup module (HPM) 20: polarized beam splitter (PBS)

21: thin film translucent mirror 50: translucent mirror

30: Focus Lens 40: Collimator Lens

60: transparent plate 100: hybrid hologram pickup module

An optical pickup apparatus according to the present invention for achieving the above object comprises a plurality of light emitting means for emitting light beams of different wavelengths corresponding to a plurality of modes; One photoelectric conversion means for converting the plurality of light beams of different wavelengths into an electrical signal; And optical means for causing the plurality of light beams to be incident on the recording medium, and for receiving the light reflected after the incidence to the photoelectric conversion means.

In the optical pickup apparatus according to the present invention configured as described above, when a light beam having different wavelengths, each of which is emitted from a plurality of light emitting means, is incident on the recording medium by optical means and then reflected from the recording medium, the reflected light is reflected from each other. Light beams having different wavelengths are received by the optical means into one photoelectric conversion means, and the photoelectric conversion means converts the light beams having the different wavelengths received into electrical signals.

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

Figure 4 shows the configuration of an embodiment in which the optical pickup device according to the present invention is applied to the hologram pickup module, the light emitting diode (1) for emitting a light beam having a wavelength of 650nm; A mixed hologram 100 which emits a light beam having a wavelength of 780 nm and receives a light beam of 650 nm and 780 nm; A polarization beam splitter (PBS) 20 for changing a transmission path of the light beam according to the direction of the incident light beam; A collimator lens 40 for converting and outputting the incident light beam into horizontal light; And a focus lens 30 for condensing the converted output horizontal light into an optical spot on a recording surface of the optical disk, wherein the mixed hologram 100 is formed of a material, as shown in FIG. Co-Hologram, in which the shape (depth, depth, pitch interval, etc.) is formed differently from the 650 nm hologram or the 780 nm hologram, and incident into each region which is characteristically separated according to the formation pattern of the mixed hologram A 650 nm / 780 nm light-emitting diode and a 780 nm light-emitting diode for photoelectric conversion of the light beam to be converted into light are integrated.

The operation of the optical pick-up apparatus according to the present invention configured as described above, as in the conventional example, is performed from the 780 nm light emitting diode integrated in the mixed hologram pickup module 100 when the seated optical disc is a CD. The light beam is output via a mixed hologram (Co-Hologram), and when the seated optical disk is a DVD, a light beam of 650 nm is emitted from the 650 nm light emitting diode (1).

The light beam having a specific wavelength range (780 nm or 650 nm) that emits light as described above is formed by an external polarization beam splitter 20 to form an optical path in the optical disk direction and enter the collimator lens 40. The incident light beam is converted into horizontal light by the collimator lens 40 and then formed into a light spot on the recording surface of the optical disk by the focus lens 30.

As described above, the optical spot formed on the optical disk recording surface passes through the focus lens 30 and the collimator lens 40, and then the optical path is changed by the polarizing beam splitter 20 so that the optical holographic pickup module 100 can be moved into the mixed hologram pickup module 100. The incident and incident light beams pass through a mixed hologram (Co-Hologram) in the mixed hologram pickup module 100, thereby partitioning the plurality of regions (a, b, c, d) as shown in FIG. It is separated into the / 780nm combined light-emitting diode.

On the other hand, as the 650/780 nm combined light receiving diode, as shown in Fig. 6, a light receiving diode having a characteristic of having a light receiving rate is remarkable for a light beam having a wavelength range within 650 nm to 780 nm.

As described above, the light beams separated and input into the areas a, b, c, and d are then converted into and outputted as electrical signals A, B, C, and D corresponding to the amount of light incident in each area. Among the output electrical signals, AB is used as a focusing error signal, CD is a tracking error signal, and A + B + C + D is used as an RF signal of a high frequency component.

On the other hand, when the wavelength range of the light beam is 780 nm (when the optical disk is a CD), the tracking error signal is a (CD), that is, the difference of the electrical signal, whereas, when the wavelength range of the light beam is 650 nm (optical disk) Is a DVD, the tracking error signal corresponds to the phase difference of (CD).

FIG. 7 illustrates a configuration of another embodiment in which the optical pickup device according to the present invention is applied to a hologram pickup module, except that the polarizing beam splitter 20 is replaced with a thin film translucent mirror 21 to reduce manufacturing cost. It is comprised including the same component as FIG. 4, The angle (theta) in which the light beam emitted from the said 650 nm light emitting diode 1 is incident on the said thin film translucent mirror 21 surface is in the range of 45 degrees-60 degrees. Is set in.

In the optical pickup device configured as described above, when the seated optical disk is a DVD, the angle at which the light beam emitted from the 650 nm light emitting diode 1 forms the surface of the thin film translucent mirror 21 is within the range described above. = 45 ° + α), the 650 nm light beam emitted from the 650 nm light emitting diode 1 is incident and transmitted from the plane of the thin film translucent mirror 21 at an angle of θ, thereby allowing a collimator lens ( 40) and the objective lens 30 are sequentially scanned onto the recording surface of the optical disk.

On the contrary, when the seated optical disk is a normal CD, the light emitting path having the same length as the light emitting path formed when the seated optical disk is a DVD is formed, but the 780nm in the hybrid hologram pickup module 100 is formed. The light beam emitted from the light emitting diode (not shown) is incident to the thin film translucent mirror 21 at an angle δ greater than 45 ° and then reflected therein, and the collimator lens 40 is the same as the light beam of 650 nm. And an objective lens 30 are scanned onto the recording surface of the optical disk.

Each light beam (650 nm or 780 nm) reflected from the optical disk is incident on the thin film translucent mirror 21 through the objective lens 30 and the collimator lens 40 and then reflected to the hologram pickup module 100. The light is received by the 650/780 nm combined light-emitting diode in the circuit) and converted into the corresponding electric signals.

Another embodiment of the present invention described above, when compared to the optical pickup device in which the 650 nm light emitting diode 1 and the mixed hologram pickup module 100 described with reference to FIG. The manufacturing cost can be reduced by replacing the semi-transparent mirror 21, and each light beam (650 nm) does not exceed 60 ° in an angle (θ = 45 ° + α) formed with the incident surface of the 650 nm light beam. Increasing the inclination α of the thin film translucent mirror that determines the angle (θ, δ) of 780 nm) with the incident surface makes it possible to reduce the size of the device.

The optical pickup apparatus according to the present invention configured and operated as described above receives light beams having different wavelengths corresponding to plural modes by one light receiving diode, thereby reducing manufacturing cost and shortening the light receiving path. It is a very useful invention which minimizes optical loss and aims at miniaturization of an optical pickup device.

Claims (9)

An optical pickup apparatus capable of processing a light beam signal of a plurality of modes, A plurality of light emitting means for emitting light beams of different wavelengths corresponding to the mode; One photoelectric conversion means for converting the plurality of light beams of different wavelengths into an electrical signal; And And optical means for causing the plurality of light beams to be incident on a recording medium, and receiving the light reflected after the incidence to the photoelectric conversion means. The method of claim 1, And the optical means comprises a light beam separator for transmitting part of the incident light and reflecting part of the incident light. A plurality of light emitting means for emitting light beams having different wavelengths, respectively; One photoelectric conversion means integrated with any one of the plurality of light emitting means and converting the plurality of light beams received into an electrical signal; And And optical means for forming the light emitting and receiving paths. The method of claim 3, And the photoelectric conversion means further comprises a hologram for separating and transmitting the received light beam into partial light of a predetermined pattern. The method of claim 3, And any one of the light emitting means integrated with the photoelectric conversion means emits a CD-based light beam. The method of claim 3, And the different wavelengths are CD and DVD series, respectively. A plurality of light emitting means for emitting light beams of different wavelengths; A thin film translucent mirror which transmits and reflects light beams having different wavelengths to be incident on the recording medium in the same path; And And a photoelectric conversion means for converting light beams having different wavelengths, which are reflected from the recording medium after the incidence and re-reflected by the thin film translucent mirror, into electrical signals. The method of claim 7, wherein And said photoelectric conversion means is integrally formed with light emitting means for emitting a light beam reflected by said thin film translucent mirror. The method of claim 7, wherein The thin film semi-transparent mirror is provided so that the surface thereof is in the range of 45 ° to 60 ° with the transmitted incident beam.