JP2005085369A - Optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup device capable of separately receiving main and sub beams thereof even in the case of the laser beams of two wavelengths which a transmission path approaches. <P>SOLUTION: A photodetector 8 is provided with six light receiving elements 11 to 16 arranged in 3 lines and 2 columns for receiving reflected main beams, four light receiving elements 21 to 24 arranged in 2 lines and 2 columns for receiving first reflected subbeams, and four light receiving elements 31 to 34 arranged in 2 lines and 2 columns for receiving second reflected subbeams. In the case of using first laser beams, the main beams of the first laser beams are received by the light receiving elements 11 to 14, and the subbeams of the first laser beams are received by the light receiving elements 21 to 24 and 31 to 34. In the case of using second laser beams, the main beams of the second laser beams are received by the light receiving elements 13 to 16, and the subbeams of the second laser beams are received by the light receiving elements 23, 24, 33 and 34. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical pickup device that irradiates a disk surface with laser light, receives the reflected light, and converts it into an electrical signal, and more particularly to an optical pickup device that uses laser light of two different wavelengths.

  In an optical disk apparatus that records and reproduces data on and from an optical disk such as a DVD or a CD, the recording surface of the optical disk is irradiated with laser light from an optical pickup device, the reflected light is received, and converted into an electrical signal. Information recorded on the optical disk is converted into digital data and reproduced. In the optical disc apparatus, focus control and tracking control are performed so that the laser beam applied to the optical disc is appropriate. In order to perform these controls, the optical pickup device of the optical disk device passes the laser output from the semiconductor laser element through the diffraction grating, thereby allowing the main beam (0th order diffracted light) and two sub beams (−1st order diffracted light, +1 next time). And then irradiating the optical disk surface through a predetermined optical transmission path. Then, the reflected light of these main beams and sub beams is received and used for each control using an astigmatism method, a differential astigmatism method, or the like. In these methods, the received light intensity in each light receiving region obtained by dividing the received light into a cross from a substantially center is used. For this reason, a conventional optical pickup device uses a photodetector in which a plurality of light receiving elements are arranged in a light receiving region for receiving a main beam.

  In addition, in an optical disc apparatus capable of recording and reproducing both DVD and CD, the wavelength of the laser beam for DVD and the laser beam for CD are different, so that a laser output element that outputs laser light of each wavelength is required. . As a laser output element for outputting such two-wavelength laser light, a hybrid type laser output element each having two wavelength laser output elements in one package and one semiconductor element in one package have two wavelengths. And a monolithic laser output element that outputs the laser beam.

  In these laser output elements, the output positions of the laser light are separated by, for example, about 110 μm. For this reason, in an optical pickup device using such a laser output element, the photodetector is provided with a plurality of light receiving elements formed for each light receiving region of each laser reflected light (for example, Patent Document 1, (See Patent Document 2).

JP 2001-67712 A JP 2000-39738 A

  By the way, since the sub beam is transmitted at a predetermined distance from the main beam, the beam shape is deformed at the position where the laser reflected light reaches the photodetector. For this reason, the light receiving area of the sub beam must be larger than the light receiving area of the main beam. For example, as shown in FIG. 4, even if the light receiving area of the main beam has a square shape of about 100 μm × 100 μm, the light receiving area of the sub beam must have a rectangular shape of about 150 μm × 100 μm. However, when the laser output element that outputs laser light having two wavelengths as described above is used, the distance between the centers of the beam spots of the two laser reflected lights is only about 110 μm. Even if it is possible to form an array, the sub-beam light receiving elements cannot be formed for each laser because the laser light receiving regions overlap each other.

  Here, DVD-R / W and DVD-RAM exist as standards for DVD, and when reproducing DVD-RAM, differential astigmatism using three beams of main beam and sub beam for focus control. The method is commonly used. However, when the laser output element as described above is used, the light receiving area for the CD laser light and the light receiving area for the DVD-RAM overlap with each other, and an optical disc apparatus capable of reproducing both of them cannot be realized. .

  An object of the present invention is to realize an optical disc capable of recording / reproducing all of CDs, DVD-R / Ws, and DVD-RAMs. It is an object to provide an optical pickup device that can divide and receive light.

  The present invention includes a laser beam output means for outputting first and second laser beams having different wavelengths to a disk while being shifted in parallel by a predetermined distance, and a main beam and a main beam respectively for the first and second laser beams. Light comprising: a diffraction grating that divides a beam into three beams, two sub-beams facing each side of the beam; and a light detection means that receives the reflected light from the disk surface of each beam, converts it into an electrical signal, and outputs the signal. In the pickup apparatus, the light detection means includes a sub-beam light receiving element that divides the reflected light of the sub-beam of the first laser light into four at substantially the center and receives the reflected light of the sub-beam of the second laser light in two. It has a feature.

  Further, according to the present invention, the light detection means includes a main beam light receiving element that receives the reflected light of the main beam of the first laser light and the reflected light of the main beam of the second laser light in four parts. It is characterized by.

  In this configuration, the main beam and the sub beam of the reflected light of the first laser light are received, and the main beam and the sub beam of the reflected light of the second laser light are received. Furthermore, since the light receiving area is divided for both the main beam and the sub beam, the astigmatism method using only one main beam, the phase push-pull method, or differential non-difference using the main beam and the sub beam are used. The point aberration method can be performed regardless of the type of laser beam.

  According to the present invention, the electrical signal from the sub-beam light-receiving element in the same divided region in each light-receiving region of the two sub-beams of the first laser light is added to the light detection means and output, or 2 of the second laser light. It is characterized by comprising selection means for selecting whether to output an electrical signal from the sub-beam light receiving element in each light receiving region into which the two sub beams are divided.

  In this configuration, since the output with respect to the first laser beam and the output with respect to the second laser beam are selected inside the light detection means, the light detection means is provided rather than providing an external connection terminal for each laser light individually. The number of external connection terminals is suppressed.

  According to the present invention, it is possible to configure an optical pickup device that can receive the reflected light of the main beam and the sub beam with any of two-wavelength laser beams. As a result, an optical disc apparatus that can perform focus control or tracking control using three beams regardless of the type of optical disc is configured by using one laser beam for DVD and the other laser beam for CD. be able to. That is, it is possible to configure an optical disc apparatus capable of recording / reproducing on any of DVD-R / W, DVD-RAM, and CD.

An optical disc apparatus provided with an optical pickup device according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing the main part of the optical system of the optical pickup device of the present invention.
As shown in FIG. 1, the optical pickup device includes a two-wavelength laser element 1, a diffraction grating 2, a prism 3, a wave plate 4, a reflection mirror 5, a collimator lens 6, an objective lens 7, and a photodetector 8.

  The two-wavelength laser element 1 is composed of a monolithic laser diode or the like that outputs two-wavelength laser light in a single semiconductor package, and the first laser light and the second laser light are output in parallel from a position separated by a predetermined distance. Is done. The laser light output from the two-wavelength laser element 1 passes through the diffraction grating 2 and is diffracted into a main beam (0th order diffracted light) and two sub beams (+ 1st order diffracted light and −1st order diffracted light). The prism 3 is arranged so as to transmit incident light from the two-wavelength laser element 1 side and reflect incident light from the wavelength plate 4 side by 90 °, and the main beam output from the diffraction grating 2 and two The sub beam passes through the prism 3 and propagates to the wave plate 4. The wave plate 4 polarizes input light, and the main beam and the sub beam are polarized by passing through the wave plate 4 and propagated to the reflection mirror 5. The reflection mirror 5 reflects the main beam and the sub beam in a direction perpendicular to the optical disk recording surface. The main beam and the sub beam reflected by the reflection mirror 5 sequentially pass through the collimator lens 6 and the objective lens 7, thereby forming a light spot on the surface of the optical disc recording surface.

  The main beam (hereinafter referred to as “reflected main beam”) and the sub beam (hereinafter referred to as “reflected sub beam”) reflected by the optical disk surface pass through the objective lens 7 and the collimator lens 6 and are reflected by the reflecting mirror 5. Then, the light passes through the wave plate 4 and is propagated to the prism 3. As described above, the prism 3 reflects the light from the wave plate 4 side by 90 °, so that the reflected main beam and the reflected sub beam are reflected by 90 ° to detect light. Propagated to vessel 8.

  The photodetector 8 reads the information recorded on the optical disc by converting the received main beam into an electrical signal.

FIG. 2 is a block diagram of the photodetector 8.
As shown in FIG. 2, the photodetector 8 includes six light receiving elements 11 to 16 arranged in 3 rows and 2 columns for receiving a reflected main beam corresponding to the light receiving element for main beam of the present invention, and the present invention. The four light receiving elements 21 to 24 arranged in 2 rows and 2 columns for receiving the first reflected sub beam, and the 2 rows and 2 columns for receiving the second reflected sub beam, corresponding to the light receiving elements for the sub beam, The four light receiving elements 31 to 34 are provided. The photodetector 8 includes wiring patterns 51 to 64 connected to each of the light receiving elements 11 to 16, 21 to 24, and 31 to 34, switches 71 to 74, and external output terminals 81 to 88.

  The light receiving elements 11 to 16 include a substantially square light receiving surface. These light receiving elements 11 to 16 split and receive the reflected main beam of the first laser beam in a square-shaped light receiving region composed of the light receiving elements 11 to 14, and form a square shape composed of the light receiving elements 13 to 16. The reflected main beam of the second laser beam is divided and received in the mold region. That is, when the first laser beam is used, the electrical signals from the light receiving elements 11 to 14 are added to read information recorded on the optical disk, and when the second laser beam is used, the light receiving element 13 is used. The information recorded on the optical disk is read by adding the electrical signals from ˜16.

  The light receiving elements 21 and 22 are provided with a substantially square light receiving surface having a long side in a direction parallel to the arrangement direction of the two beams, and the light receiving elements 23 and 24 are sides in a direction parallel to the arrangement direction of the two beams. Is a long side, and the long side is provided with a rectangular light receiving surface that is significantly longer than the short side. And the center of the cross which divides each part of the shape of the shape of the deformation field which consists of light receiving elements 21-24 corresponds with the approximate center of the 1st reflective sub beam of the 1st laser beam, and light receiving elements 23 and 24 are the 2nd laser beam. The light receiving elements 21 to 24 are arranged so as to include the light receiving region of the first reflected sub beam. By arranging the light receiving elements 21 to 24 in this way, the light receiving elements 21 to 24 receive the first reflected sub-beam of the first laser light in four parts, and the light receiving elements 23 and 24 receive the second laser light of the second laser light. One reflected sub-beam is divided into two and received.

  The light receiving elements 31 and 32 have a rectangular light receiving surface having a side substantially parallel to the arrangement direction of the two beams as a long side, and the light receiving elements 33 and 34 are parallel to the arrangement direction of the two beams. A light receiving surface having a rectangular shape with a long side as a long side and a long side significantly longer than a short side is provided. And the center of the cross which divides each part of the shape of the deformation field which consists of light receiving elements 31-34 coincides with the center of the 2nd reflected sub beam of the 1st laser beam, and light receiving elements 33 and 34 are the 2nd laser beam. The light receiving elements 31 to 34 are arranged so as to include the light receiving region of the second reflective sub beam. By arranging the light receiving elements 21 to 24 in this way, the light receiving elements 31 to 34 receive the second reflected sub-beam of the first laser light in four parts, and the light receiving elements 33 and 34 receive the second laser light of the second laser light. The two reflected sub-beams are divided into two and received.

  The wiring pattern 51 connects the light receiving element 11 and the switch 71, and the wiring pattern 52 connects the light receiving element 12 and the switch 72. The wiring pattern 53 connects the light receiving element 13 and the switches 71 and 73, and the wiring pattern 54 connects the light receiving element 14 and the switches 72 and 74. The wiring pattern 55 connects the light receiving element 15 and the switch 73, and the wiring pattern 56 connects the light receiving element 16 and the switch 74. The switch 71 is connected to the external terminal 81 and switched so that the external terminal 81 is electrically connected to one of the wiring patterns 51 and 53, and the switch 72 is connected to the external terminal 82, and the external terminal 82 is connected to the wiring pattern 52. , 54 so as to be conducted. The switch 73 is connected to the external terminal 83 and switched so that the external terminal 83 is electrically connected to one of the wiring patterns 53 and 55, and the switch 74 is connected to the external terminal 84, and the external terminal 84 is connected to the wiring pattern 54. , 56 is switched so as to be conducted.

  The wiring pattern 57 connected to the light receiving element 21 and the wiring pattern 61 connected to the light receiving element 31 are connected to the input side of the adder 91, and the output side of the adder 91 is connected to the external terminal 85 via the wiring pattern 65. doing. The wiring pattern 58 connected to the light receiving element 22 and the wiring pattern 62 connected to the light receiving element 32 are connected to the input side of the adder 92, and the output side of the adder 92 is connected to the external terminal 86 via the wiring pattern 66. doing. The wiring pattern 59 connected to the light receiving element 23 and the wiring pattern 63 connected to the light receiving element 33 are connected to the input side of the adder 93, and the output side of the adder 93 is connected to the external terminal 87 via the wiring pattern 67. doing. The wiring pattern 60 connected to the light receiving element 24 and the wiring pattern 64 connected to the light receiving element 34 are connected to the input side of the adder 94, and the output side of the adder 94 is connected to the external terminal 88 via the wiring pattern 68. doing.

  Next, a method for reading information recorded on an optical disk and a method for performing focus control and tracking control using the optical pickup having such a configuration will be described.

(1) When Using First Laser Light Here, a case where DVD laser light (wavelength 650 nm) is used as the first laser light will be described.

The DVD laser light output from the two-wavelength laser element 1 is reflected on the surface of the DVD recording surface through the optical path described above and is input to the photodetector 8. The reflected main beam of the DVD laser light is received by the light receiving elements 11 to 14, and the first and second reflected sub beams are received by the light receiving elements 21 to 24 and the light receiving elements 31 to 34. The received beam is converted into an electric signal according to its intensity and transmitted to the external terminals 81 to 88 via the wiring pattern.
Here, voltages corresponding to the beams received by the light receiving elements 11 to 14 are A, B, C, and D, respectively, and voltages corresponding to the beams received by the light receiving elements 21 to 24 are G1, H1, I1, respectively. Assume that J1 is a voltage corresponding to the beam received by the light receiving elements 31 to 34, and G2, H2, I2, and J2.

  Switching signals are input to the switch circuits 71 to 74. When the switching is sequentially performed and signals are output to the external terminals 81 to 84, the switching is stopped and the predetermined wiring pattern and the external terminals 81 to 84 are made conductive. . That is, when DVD laser light is used, the wiring pattern 51 is conducted to the external terminal 81, the wiring pattern 52 is conducted to the external terminal 82, the wiring pattern 53 is conducted to the external terminal 83, and the wiring pattern 54 is connected to the external terminal. 84 is conducted.

  By making such a connection, the voltages A, B, C, and D are transmitted from the light receiving elements 11 to 14 to the external terminals 81 to 84. Therefore, it is possible to acquire an RF signal by adding them. The information recorded on the DVD can be read.

In the case of DVD-R / W, since the focus error detection uses an astigmatism method using one beam, the focus error signal (FE) is
FE = (A + D)-(B + C)
It is. Thereby, focus control at the time of DVD-R / W recording / reproduction can be performed by using the voltages A to D output from the external terminals 81 to 84.
On the other hand, to the external terminals 85 to 88, voltages G1 + G2, H1 + H2, I1 + I2, and J1 + J2 are obtained by adding the voltages corresponding to the received beam intensities in the same region of the first sub-beam and the second sub-beam through the adders 91 to 94. Is being transmitted.

In the case of DVD-RAM, since focus error detection uses a differential astigmatism method using three beams, the focus error signal (FE) is:
FE = (A + D)-(B + C) -k1 [{(G1 + G2) + (J1 + J2)}-{(H1 + H2)-(I1 + I2)}] (k1 is a preset constant)
It is. Thus, focus control during DVD-RAM recording / reproduction can be performed by using the voltages A to D, the voltages G1 + G2, H1 + H2, I1 + I2, and J1 + J2 output from the external terminals 81 to 88.

In addition, since the DPD method is used for tracking control during DVD playback, the tracking error signal (TEr) during playback is
TEr = ΔPH [(A + D) − (B + C)]
That is, the phase difference between the voltage (A + D) and the voltage (B + C). Thereby, tracking control at the time of DVD reproduction | regeneration can be performed by using the voltage AD output from the external terminals 81-84.

In addition, since the DPP method is used for tracking control during DVD recording, the tracking error signal (TEw) during recording is
TEw = (A + C)-(B + D) -k2 [{(G1 + G2) + (I1 + I2)}-{(H1 + H2)-(J1 + J2)}] (k2 is a preset constant)
It is. Thereby, tracking control at the time of DVD recording can be performed by using the voltages AD output from the external terminals 81 to 88, the voltages G1 + G2, H1 + H2, I1 + I2, and J1 + J2.

(2) Case where Second Laser Light is Used Here, a case where CD laser light (wavelength 780 nm) is used as the second laser light will be described.

The laser beam for CD output from the two-wavelength laser element 1 is reflected on the surface of the CD recording surface through the optical path described above and is input to the photodetector 8. The reflected main beam of the CD laser light is received by the light receiving elements 13 to 16, and the first and second reflected sub beams are received by the light receiving elements 23 and 24 and the light receiving elements 33 and 34. The received beam is converted into an electric signal according to its intensity and transmitted to the external terminals 81 to 88 via the wiring pattern.
Here, the voltages corresponding to the beams received by the light receiving elements 13 to 16 are C, D, E, and F, respectively, and the voltages corresponding to the beams received by the light receiving elements 23 and 24 are I1 and J1, respectively. The voltages corresponding to the beams received by the elements 33 and 34 are I2 and J2, respectively.

  Switching signals are input to the switch circuits 71 to 74. When the switching is sequentially performed and signals are output to the external terminals 81 to 84, the switching is stopped and the predetermined wiring pattern and the external terminals 81 to 84 are made conductive. . That is, when the CD laser beam is used, the wiring pattern 53 is conducted to the external terminal 81, the wiring pattern 54 is conducted to the external terminal 82, the wiring pattern 55 is conducted to the external terminal 83, and the wiring pattern 56 is connected to the external terminal. 84 is conducted.

  By performing such a connection, voltages C, D, E, and F are transmitted from the light receiving elements 13 to 16 to the external terminals 81 to 84. Therefore, an RF signal can be acquired by adding these voltages. The information recorded on the CD can be read.

Also in the case of a CD, since the focus error detection uses the astigmatism method using one beam, the focus error signal (FE) is
FE = (C + F)-(D + E)
It is. Thereby, the focus control at the time of CD recording / reproducing can be performed by using the voltages C to F output from the external terminals 81 to 84.
On the other hand, the DPP method is used for tracking control during CD recording, and the tracking error signal (TEw) during recording is
TEw = (C + E) − (D + F) −k3 [{(G1 + I1) − (H1 + J1)} + {(G2 + I2) − (H2 + J2)}] (k3 is a preset constant)
It is. Here, in the case of CD laser light, no sub beam is input to the light receiving elements 21, 22, 31, 32, so that the voltages G 1 + G 2, H 1 + H 2 are not output from the external terminals 85, 86, Only the voltages I1 + I2 and J1 + J2 are output, but the above formula is satisfied by using the voltages C to F output from the external terminals 81 to 84 and the voltages I1 + I2 and J1 + J2 output from the external terminals 87 and 88. Therefore, tracking control during CD recording can be performed.
By using the above-described configuration as shown in FIG. 3, the 3-beam method can be used for CD tracking error detection.

FIG. 3 is a block diagram showing another wiring pattern of the photodetector 8.
The photodetector 8 shown in FIG. 3 selects and connects the switch 75 for selecting and connecting the external terminal 85 to one of the wiring patterns 65 and 59 and the external terminal 86 for selecting any of the wiring patterns 66 and 60. A switch 76, a switch 77 for selecting and connecting the external terminal 87 to any one of the wiring patterns 67 and 63, and a switch 78 for selecting and connecting the external terminal 88 to any one of the wiring patterns 68 and 64 are provided. The other structure is the same as that of the photodetector shown in FIG.

  With such a configuration, I1, J1, I2, and J2 can be output from the external terminals 85 to 88, respectively.

A three-beam method is generally used for tracking control during CD playback, and the tracking error signal (TEr) at this time is
TEr = (I1 + J1) − (I2 + J2)
It is. Thereby, tracking control at the time of CD reproduction | regeneration can be performed by using voltage I1, J1, I2, J2 output from the external terminals 85-88.

  With the configuration as described above, it is possible to configure an optical pickup device capable of receiving the main beam and the two sub beams separately, regardless of the type of the optical disk. As a result, an optical disc apparatus capable of performing focus control and tracking control using either the three beam method or the one beam method can be configured without depending on the type of the optical disc. That is, it is possible to configure an optical disc apparatus that can perform recording and reproduction without depending on the type of the optical disc.

The block diagram which shows the principal part of the optical system of the optical pick-up apparatus of this invention Block diagram of photodetector 8 Block diagram showing another wiring pattern of the photodetector 8 The figure which shows the arrangement pattern of the light receiving element of the conventional photodetector

Explanation of symbols

1-2 wavelength laser element 2-diffraction grating 3-prism 4-wave plate 5-reflection mirror 6-collimator lens 7-objective lens 8-photodetectors 11-16-light receiving elements 21-24 for main beam-first sub beam Light receiving elements 31-34, second sub-beam light receiving elements 51-68, wiring patterns 71-78, switches 81-88, external terminals 91-94, and adders

Claims (4)

Laser beam output means for outputting first and second laser beams having different wavelengths parallel to each other by a predetermined distance, and the first and second laser beams are opposed to the main beam and both sides of the main beam, respectively. In an optical pickup device comprising: a diffraction grating that divides a beam into three sub-beams; and a light detection means that receives the reflected light from the disk surface of each beam, converts it into an electrical signal, and outputs it.
The light detecting means divides the reflected light of the sub-beam of the first laser light into four at a substantially center, and receives the reflected light of the sub-beam of the second laser light in two, and receives the sub-beam light receiving element.
The electric signals from the light receiving elements in the same divided region in the respective light receiving regions of the two sub beams of the first laser light are added and output, or the light receiving regions of the divided light receiving regions of the two sub beams of the second laser light are received. Selecting means for selecting whether to output an electrical signal from the element;
An optical pickup device comprising: a light receiving region for the main beam of the first laser light; and a light receiving element for main beam for receiving the main beam of the second laser light by dividing the light into four parts. Laser beam output means for outputting first and second laser beams having different wavelengths parallel to each other by a predetermined distance, and the first and second laser beams opposed to the main beam and both sides of the main beam, respectively. In an optical pickup device comprising a diffraction grating that divides a beam into three sub-beams, and a light detection means that receives the reflected light from the disk of each beam, converts it into an electrical signal, and outputs it.
The light detection means includes a sub-beam light receiving element that divides the reflected light of the sub-beam of the first laser light into four at substantially the center and receives the reflected light of the sub-beam of the second laser light in two. An optical pickup device characterized by the above.   The light detecting means adds and outputs an electric signal from a light receiving element in the same divided area in each light receiving area of the two sub beams of the first laser light, or the two sub beams of the second laser light are divided. 3. The optical pickup device according to claim 2, further comprising selection means for selecting whether to output an electrical signal from the light receiving element in each light receiving region.   4. The light detection unit according to claim 2, wherein the light detection unit includes a main beam light receiving element that receives the main beam of the first laser light and the main beam of the second laser light by dividing the light into four parts. Optical pickup device.

Images