JP2000048381A - Tracking error detecting method, and optical pickup and optical disk device adjusted by the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tracking error detecting method by which the yield of a product is improved by extending the allowable range of mounting errors at the time of mounting a light emitting section, and to provide an optical pickup and an optical disk device which are adjusted by the method. SOLUTION: In this tracking error detection method, output signals are detected by divided photodetectors 4 and 5, which are at least bisected in a tangential direction tan of an optical disk 11. Then the output signals are compared with each other based on a preset reference. Thus the photodetectors 4 and 5 are selected corresponding to the comparison result and a tracking error signal TE is obtained by a phase difference method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a tracking error detection method for obtaining a tracking error signal by a phase difference method, an optical pickup adjusted by the tracking error detection method, and an optical disk apparatus.

[0002]

2. Description of the Related Art With the recent development of technology, an information recording medium having a larger recording capacity has been developed. An example of this information recording medium is a DVD (Digital Vid).
There are optical disks such as eoDisc). An optical pickup is used for recording and / or reproducing such an optical disk.

FIG. 18 is a sectional view showing the structure of a light receiving / emitting element of a conventional optical pickup. Light emitting / receiving element 129
Includes a light emitting / receiving element 129 (DVD-LC) in which the light irradiation unit 107, the prism 121, the front photo detector 111, and the rear photo detector 112 are integrated. The optical pickup 113 is equipped with a tracking control circuit as a circuit section for accurately tracing a track formed on the signal recording surface of the optical disk.

When reproducing information recorded on, for example, a signal recording surface of an optical disk (hereinafter, referred to as a recording surface), the optical pickup 113 transmits light from the light irradiation unit 107 to the recording surface of the optical disk that is driven to rotate. Irradiate light. The optical pickup 113 reproduces information by detecting the return light 126 reflected on the disk surface by the photodetector 111 or the like. In the case of this reproduction, etc.,
The tracking control circuit performs tracking control based on a tracking error signal so that the light emitted from the optical pickup 113 accurately traces the center of the track on which pits and the like of the optical disk are formed.

As the tracking control method, for example, a three-spot method, a push-pull method, a top-hold push-pull method, a differential push-pull method, and a DPD (Diff
A renual phase detection (phase difference method) and the like are known. As a tracking control method in recording and / or reproducing information on an optical disk such as a DVD, a DPD method is mainly employed.

FIG. 19 is a block diagram showing a conventional tracking control circuit to which the DPD method is applied. The tracking control circuit 109 generates the tracking error signal TE by the DPD method as described below. The optical pickup 113 performs tracking control based on the tracking error signal TE so that light emitted from the light emitting / receiving element 129 traces a track.

The tracking control circuit 109 includes a front photo detector 111, a rear photo detector 11
2. High-band summing amplifiers 113, 114, 115, 11
6. It has phase comparators 117 and 118 and an addition amplifier 119.

Return light 12 from optical pickup 113
6 is reflected in the prism 121 as shown in FIG. 18 and received by the front photo detector 111 and the rear photo detector 112. The front photodetector 111 is divided into a tangential direction tan and a radial direction rad as shown in FIG.

The front photodetector 111 is shown in FIG.
9 includes each element 111a forming the upper half and 111b forming the lower half. The elements 111a and 111b are based on the amounts of light received, respectively, in A and E, B and F, C and G, D and H in FIG.
So as to take the sum signal of the high-band summing amplifiers 113 and 1
14 (hereinafter, the element 111b is omitted because it is substantially the same). Then, the high band addition amplifier 114
And 115 are output from the phase comparator 11
7, and the phases are compared. D as a phase difference signal
A PD signal is generated. The two DPD signals from the phase comparators 117 and 118 are respectively added by an addition amplifier 119, and a tracking error signal TE is generated based on this signal. The optical pickup 113 performs tracking control based on the tracking error signal.

The light irradiating section 107 is mounted on the light receiving / emitting element 129 used for generating the tracking error signal TE. When assembling the optical pickup 113 as described above, the light irradiating section 107 is positioned so that the semiconductor laser element 107a having a semiconductor laser element for irradiating light can accurately irradiate the recording surface of the optical disc. Need to be attached.

[0011]

However, the position of the spot on the photodetector 111 in the tangential direction tan (tangential direction) in the photodetector 111 due to a mounting height error or the like when the semiconductor laser element 107a is mounted. Poor accuracy. The amplitude of the DPD signal may be reduced due to a positional shift at the time of mounting the semiconductor laser element 107a, which may hinder tracking servo. Therefore,
When the semiconductor laser element 107a is mounted on the light receiving / emitting element 129, the mounting tolerance must be reduced to increase the positioning accuracy. Therefore, it is difficult to improve the yield when manufacturing the optical pickup 113 as a product.

Therefore, the present invention solves the above-mentioned problems, and improves the yield of products by expanding the allowable range of the mounting error when mounting the light emitting section. The tracking error detecting method can be adjusted by the tracking error detecting method. It is an object of the present invention to provide an optical pickup and an optical disk device which are provided.

[0013]

SUMMARY OF THE INVENTION The object of the present invention is to provide a light detector in which light is emitted by a light emitting section and return light reflected by a signal recording surface of an optical disk or a reflection surface equivalent thereto is detected by a photodetector. A tracking error detection method for acquiring a tracking error signal by a phase difference method based on an output signal of the photodetector,
An output signal is detected by at least two split photodetectors in the tangential direction of the optical disc, and the output signals are compared based on a preset reference. This is achieved by a tracking error detection method, characterized in that a tracking error signal is obtained by a phase difference method by selecting a tracking device.

In the present invention, the light emitted by the light emitting section is reflected, and is reflected on the signal recording surface of the optical disk or a reflection surface equivalent thereto. The return light is received by a photodetector composed of at least two split photodetectors. Each split photodetector outputs a signal for each split photodetector based on the received light. The output signals are
The comparison is performed based on a preset standard. Then, a suitable split photodetector is selected from the plurality of split photodetectors based on the comparison result, and a tracking error signal is obtained by the phase difference method.

[0015]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Although the embodiments described below are preferred specific examples of the present invention, various technically preferable limitations are given. However, the scope of the present invention is not limited to the following description. It is not limited to these forms unless otherwise stated.

The terms used in the following description are defined as follows. The “tangential direction” indicates, for example, a direction corresponding to a tangential direction of the optical disc, a direction along a recording track of the optical disc, and is substantially the same as the tracking direction. The “spot” indicates the light receiving position of the light received by the photodetector (photodetector), and the “spot shift (spot position shift)” refers to the return light that is emitted by attaching the light emitting unit when assembling the optical pickup. This indicates that the spot is shifted from a predetermined position, for example, in the tangential direction when light is received. "DPD (Differential Pha
The “se Detection signal” indicates a signal serving as a basis for acquiring a tracking error signal by comparing output signals from the respective photodetectors by a phase difference method.

First Embodiment FIG. 1 shows an example of the configuration of an optical disk device incorporating an optical pickup adjusted by a tracking error detection method according to a first embodiment of the present invention. FIG.
In the optical disk device 10, a spindle motor 12 as a driving unit for driving the optical disk 11 to rotate,
An optical pickup 13 is provided. Here, the spindle motor 12 is connected to the optical disk drive controller 14.
, And is rotated at a predetermined rotation speed. The optical disc 11 is, for example, a DVD (Digital Vid).
eo Disc).

The optical pickup 13 records a signal on a signal recording surface of the rotating optical disk 11, or receives a return light from the signal recording surface 11a and demodulates a signal based on the detection signal. A reproduction signal based on the return light 26 is output to the device 15.

As a result, the recording signal demodulated by the signal demodulator 15 is subjected to error correction via the error correction circuit 16 and is output to the interface 17 (for example, SCSI (Smal).
l Computer System Interfa
ce) to an external computer or the like. As a result, the external computer or the like
Can be received as a reproduction signal.

The optical pickup 13 is connected to a head access control unit 18 for moving the optical pickup 11 to a predetermined recording track on a signal recording surface of the optical disk 11 by a track jump or the like. Further, at the moved predetermined position, the objective lens 22 is moved in the focusing direction Fo and the tracking direction Tr with respect to a biaxial actuator (not shown) that holds the objective lens 22 of the optical pickup 13 as shown in FIG. A servo circuit 19 for performing the operation is connected. The optical pickup 13 is provided with a tracking control circuit 9 (not shown in FIG. 1) described later.

FIG. 2 is a plan view showing a configuration example of a part of the optical pickup of FIG. In FIG. 2, the optical pickup 13 includes a light receiving / emitting element 29, a collimator lens 23,
And an objective lens 22 (light focusing means).

The light emitting / receiving element 29 has two light emitting / receiving sections stacked in two stages. Each light emitting / receiving section is formed by integrating a semiconductor laser element as a light emitting element and a photodetector as a light receiving element. It is configured.

The collimator lens 23 is a lens for converting the light emitted from the light irradiation section 7 having the semiconductor laser element of the light receiving / emitting element 29 into parallel light.

The objective lens 22 can be any object provided that it has a function of focusing light on the signal recording surface 11a (recording surface) of the optical disk 11.
Not only an optical lens but also a hologram element having a lens function can be used. In this embodiment, for example, the objective lens 22 is a convex lens, and emits light from the light receiving / emitting element 29 to the signal recording surface 1 of the optical disk 11 that is driven to rotate.
An image is formed on a desired track 1a. Further, the objective lens 22 is driven by a biaxial actuator (not shown).
It is supported so as to be movable in two axial directions, ie, a tracking direction Tr and a focusing direction Fo.

FIG. 3 is a sectional view showing a section of the light emitting and receiving element of FIG. The light receiving / emitting element 29 is provided on the first semiconductor substrate 30.
A second semiconductor substrate 7d is mounted thereon, and a semiconductor laser element 7a (light emitting unit) as a light emitting element is mounted on the second semiconductor substrate 7d. The semiconductor laser element 7a is provided on the first semiconductor substrate 30 in front of the semiconductor laser element 7a.
A prism 21 having a rectangular parallelepiped shape provided with an optical path branch surface 21c (incident portion) is disposed in the vicinity thereof, and is joined by, for example, a transparent resin adhesive.

FIG. 4 is a circuit block diagram showing the above-described tracking control circuit and a circuit for realizing the tracking error detection method according to the first embodiment of the present invention. The tracking control circuit 9 and the like include a front photodetector 2 (hereinafter simply referred to as a photodetector unless otherwise specified), a rear photodetector 3, high-band addition amplifiers 33, 34, 35, 36, and phase comparators 37, 38.
And a selection switch 39, and is connected to the amplitude comparator 40.

The light-receiving / emitting element 29 is divided into a front photodetector 2 and a rear photodetector 2 as shown in FIG. 4 because the recording pits of the optical disk are extremely small in order to correspond to a high-density optical disk such as a DVD. 3 is used. In the following description, mainly the front photo detector 2 will be described.

As shown in FIG. 4, the photodetector 2 is provided in the tangential direction tan of the disk 11 shown in FIG.
A first photodetector pair 4 (split photodetector) and a second photodetector pair 5 (split photodetector) which are split so as to be divided into two parts from the center.

The first photodetector pair 4 is shown in FIG.
Is divided into four parts in the radial direction rad so as to be approximately bisected right and left from the center. As a result, the first photodetector pair 4 includes the elements 4a and 4a, respectively.
b, 4c and 4d. The first photodetector pair 4 has the elements 4b and 4c in the radial direction r so that they are finely divided in the vicinity of the received spot SP.
The configuration is such that the width is reduced at the ag.

The photo detectors 4a and 4b are connected to the high-band summing amplifier 33, and are connected to the photo detector 4c.
And 4d are connected to a high-band summing amplifier 34. The high-band summing amplifiers 33 and 34 are respectively connected to the spot SP
The output signals from the photodetectors 4a and 4b and the photodetectors 4c and 4d based on the output signals detected by the above are added.

When the signals from the high-band addition amplifiers 33 and 34 are input, the amplitude comparator 37 detects which one of the signals is advanced in phase and outputs the signal as a comparison result of the amplitude. The 1DPD signal 47 is output to the amplitude comparator 40.

The second photodetector pair 5 includes the first
The photodetector pair 4 has substantially the same configuration as the photodetector pair 4, and outputs a second D
The PD signal 48 is output.

The amplitude comparator 40 is a circuit block for comparing the amplitudes of a plurality of input signals. The amplitude comparator 40 is provided, for example, outside the optical pickup 13. The amplitude comparator 40 is, for example, an inspection device or an adjusting device such as an oscilloscope in a test / prototype stage of the optical pickup 13 or a predetermined inspection / adjustment device in a manufacturing stage of the optical pickup 13. When the optical disc 11 is arranged to rotate, the amplitude comparator 40 makes the following determination based on the return light 26.

The amplitude comparator 40 includes a first DPD signal 47 and a second DP signal from the phase comparators 37 and 38, respectively.
The amplitude of the D signal 48 is compared. The amplitude comparator 40 has a first
When the amplitude of the DPD signal 47 is larger than the amplitude of the second DPD signal 48, the selection switch 39 is turned on at the contact 39a.
And the first DPD signal 47 is selected. Amplitude comparator 40
In the opposite case, the selection switch 39 is set to the contact 39
The b-side is turned on, and the second DPD signal 48 is selected to efficiently generate the tracking error signal TE.

In other words, a criterion for the phase comparator 40 to select a photodetector pair is that the amplitude is large when each output signal from the photodetector pair is compared.

The optical pickup is configured as described above. Next, a procedure for adjusting the optical pickup by the tracking error detecting method according to a preferred embodiment of the present invention will be described. The optical pickup 13 is provided with a semiconductor laser element 7a for irradiating the optical disc 11 with light in a manufacturing stage. When the semiconductor laser element 7a is mounted on the optical pickup 13, for example, the positioning accuracy of the optical disk 11 in the radial direction rad is conventionally ensured, but the positioning accuracy in the tangential direction tan may not be ensured in some cases. Was. Accordingly, in the optical pickup 13 to which the semiconductor laser element 7a is attached, for example, when the optical disc 11 is arranged as shown in FIG. 6, the spot SP on the photodetector 2 may be shifted from the center position as shown in FIG. there were.

Therefore, as shown in FIG.
In the state where the spot SP exists, the tracking control circuit 9 and the like in FIG. 4 are operated. The first photodetector pair 4 and the second photodetector pair 5 output signals to the high-band addition amplifiers 33 and 34 and the high-band addition amplifiers 35 and 36 according to the amount of received light as shown in FIG. High-band summing amplifier 3
In steps 3 and 34, the input signals are added, and a phase comparator 37 is added.
Output to The high-band addition amplifiers 35 and 36 add the input signals and output the added signals to the phase comparator 38.

The phase comparators 37 and 38 compare the phases of the two input signals and output a first DPD signal 47 and a second DPD signal 48 as a phase difference signal to the amplitude comparator 40. I do.

The amplitude comparator 40 compares the amplitudes of the first DPD signal 47 and the second DPD signal 48 input as described above, and selects the switch 39 so that the larger one is selected as described above. To the contact 39a or the contact 39
b is turned ON, and one of the first photodetector pair 4 and the second photodetector pair 5 is selected. Such a selection may be made once, for example, during assembly. Thus, the first DPD signal 47 or the second DPD
When the PD signal 48 is selected and the trace shift occurs on the track on the disk surface of the optical disk 11 as shown in FIG. 7A or 7B, the tracking control circuit 9 and the like generate a good tracking error signal TE. can do.

According to the first embodiment of the present invention, the light emitted by the semiconductor laser element 7a is reflected and reflected on the signal recording surface 11a of the optical disk 11 or a reflection surface equivalent thereto. The return light 26 is received by the photodetector 2 including the first photodetector pair 4 and the second photodetector pair 5 divided into at least two parts. Each first
Each of the photodetector pair 4 and the second photodetector pair 5 outputs a signal based on the received light.
The output signals are compared based on a preset criterion. Then, a suitable split photodetector is selected from the plurality of first photodetector pairs 4 and the second photodetector pairs 5 based on the comparison result, and the tracking error signal TE is obtained by the phase difference method.

When assembling the optical pickup 13, the semiconductor laser element 7a is connected to the light emitting / receiving element 2 as described above.
Since the photodetector 2 can be adjusted so that the optical pickup 13 performs good tracking error detection after being attached to the optical pickup 9, the mounting error (LD mount error) of the semiconductor laser element 7a to the light receiving / emitting element 29 and the like are caused. It is possible to increase the allowable error in the mounting accuracy with respect to the spot displacement.

As described above, the tracking error detecting method capable of improving the yield of the product by expanding the allowable range of the mounting error when mounting the semiconductor laser element 7a and the tracking error detecting method adjusted by the tracking error detecting method. Optical pickup 13 and an optical disk device can be provided.

Second Embodiment FIG. 8 is a circuit block diagram showing a tracking control circuit and a circuit for realizing a tracking error detection method according to a second embodiment of the present invention. Since the tracking control circuit 9 and the like in FIG. 8 have the same configuration as those in the tracking control circuit 9 and the like in the first embodiment in FIG. 4, portions different from those in the first embodiment will be described below. I do. In the tracking control circuit 9 of FIG. 8, the amplitude comparator 40 existing in the tracking control circuit 9 of FIG. 4 does not exist, and instead, the high band addition amplifiers 43 and 44 are provided.
And an RF amplitude comparator 41. Here, RF is an abbreviation of Radio Frequency, and indicates a reproduced signal when information recorded on the signal recording surface 11a of the optical disk 11 is reproduced. Further, in this embodiment, for example, as shown in FIG.
A mirror 28 having a reflection surface equivalent to the recording surface may be arranged.

As described in the first embodiment, the signals detected by the first photodetector pair 4 and the second photodetector pair 5 are supplied to the high-band addition amplifiers 43 and 34 and the high-band addition amplifiers 33 and 34 and 35, respectively. 3
6, the added signals are input. The high-band addition amplifiers 43 and 44 add the input signals and output the added signals to the RF amplitude comparator 41.

The RF amplitude comparator 41 compares the amplitudes of the input signals and determines, for example, the smaller of the amplitude of the RF signal (reproduced signal) in the first photodetector pair 4 or the second photodetector pair 5. The selection switch 39 is switched to the contact 39a or 39b so as to make a selection.

Accordingly, the selection criterion of the RF amplitude comparator 41 is, for example, the smaller of the amplitude of the RF signal among the first photodetector pair 4 and the second photodetector pair 5.

The reason for selecting a photodetector pair that outputs an RF signal with a small amplitude in this way will be described in the third embodiment. However, the smaller the amount of light received by the photodetector, the smaller the DPD signal as a phase difference signal. Is larger.

As in the first embodiment, the high-band addition amplifiers 43 and 44 and the RF signal comparator 41 are provided outside the optical pickup 13, for example. That is, the first
As in the embodiment, the above adjustment may be performed once, for example, at the stage of manufacturing (assembling) the optical pickup 13.

According to the second embodiment of the present invention, effects similar to those of the first embodiment can be obtained.

Third Embodiment FIG. 9 is a block diagram showing a tracking control circuit and a circuit for realizing a tracking error detection method according to a third embodiment of the present invention. In the tracking control circuit 9 and the like in FIG. 9, the portions denoted by the same reference numerals as those in the tracking control circuit 9 and the like in the first embodiment and the second embodiment have the same configuration. Will be described. In the tracking control circuit 9 of FIG. 9, the DC addition amplifiers 45 and 46 and the DC amplitude comparator 42 are used instead of the high band addition amplifiers 43 and 44 of FIG.
Exists. Here, DC is DirectCurr.
ent, which indicates the amount of received light. In this embodiment, the mirror 28 does not have to rotate.

The signals detected by the first photodetector pair 4 and the second photodetector pair 5 are supplied to the DC addition amplifiers 45 and 46 by the high-band addition amplifiers 33 and 34 and 35 and 36 as described in the first embodiment. , Are added. The high-band addition amplifiers 43 and 44 add the input signals and output the added signals to the DC addition amplifiers 45 and 46, respectively.
The DC addition amplifiers 45 and 46 further add the input signals.

The DC addition amplifiers 45 and 46 output output signals having output characteristics as shown in FIGS. 10 and 11, for example, to the DC amplitude comparator 42 in FIG. D
The C amplitude comparator 42 compares the input signals as shown in FIGS. 10 and 11 and, for example, of the first photodetector pair 4 or the second photodetector pair 5, whichever has the smaller amount of received light (for example, FIG. The selection switch 39 is switched to the contact 39b side so as to select the second photodetector pair 5) having the output characteristic. That is, the selection switch 39 switches to the contact 39a or 39b side so as to select a photodetector pair having a small amount of received light. The reason for selecting a photodetector pair having a small amount of received light is as follows.

FIG. 12 is a diagram showing an example of the amplitude of the output signal with respect to the amount of spot deviation in the tangential direction in the photodetector of the predetermined light emitting / receiving element. FIG.
The plus and minus of the spot shift (spot position shift) as the horizontal axis in FIG.
(A) to (C) are based on the spot shift directions.

FIGS. 14 to 17 are circuit diagrams each showing a DPD signal (phase difference signal) detection method by the DPD method. FIG. 14 shows a method (hereinafter referred to as an α method) of detecting the phase difference between the respective RF signals after adding the RF signals (reproduction signals) of the elements arranged diagonally to each other.

As shown in FIG. 14, the photodetector 1
Reference numeral 21 denotes two light-receiving elements 121a, 121b, and 1 each divided vertically and horizontally, that is, in the tangential direction tan and the radial direction rad of the optical disk.
21c and 121d (hereinafter, referred to as elements) are formed. In the DPD method, diagonal elements 121a and 121a are formed by a photodetector 121, respectively.
1c and the outputs of 121b and 121d are output to a high-band addition amplifier 122 and a high-band addition amplifier 123, respectively.
And a method of generating a tracking error signal TE by comparing the phases with each other.

FIGS. 15 and 16 show a method of comparing the output phases of two elements radially adjacent to each other on the disk surface among the four elements constituting the photodetector (hereinafter, β-F method and β method, respectively). −
R system). FIG. 17 shows the β-F method and the β-F method.
A method (hereinafter, referred to as a γ method) that takes a difference between respective outputs of the F method is shown.

Referring to FIG. 12, the characteristics of the β-F system and the β-R system described with reference to FIGS. 15 and 16, respectively, are shifted in the directions opposite to each other with respect to spot displacement. That is, when a spot shift occurs, the β-F method and β-R
The schemes have different characteristics. The elements (photodetectors corresponding to 4a, 4b, 4c and 4d in FIG. 9 in the β-F system and 5a, 5b,
When the area of the spot SP on the photodetectors corresponding to 5c and 5d is shifted in a direction to decrease (FIG. 1)
In the case of the first photodetector pair 4 in 1 (A)), the amplitude of the DPD signal tends to increase.

This is because the contrast of the phase difference of the RF signal is larger in a portion of the spot SP on the photodetector 2 closer to the outer peripheral portion.

As in the first embodiment, the DC area addition amplifiers 45 and 46 and the DC signal comparator 42 are provided outside the optical pickup 13, for example. That is, the first
As in the embodiment, the above adjustment may be performed once, for example, at the stage of manufacturing (assembling) the optical pickup 13.

According to the third embodiment of the present invention, effects similar to those of the first embodiment can be obtained.

The present invention is not limited to the above embodiment. Embodiments of the present invention are not limited to those described above, and a recording medium in which a track corresponding to a pit for outputting an RF signal is formed even if the track of the recording medium does not have physical irregularities. Can be applied to Further, the embodiments of the present invention can be applied to an optical pickup for recording and / or reproducing data from any optical disc on which tracking control is performed by the phase difference method.

[0062]

As described above, according to the present invention, a tracking error detecting method capable of improving the yield of products by expanding the allowable range of the mounting error when mounting the light emitting section, and the tracking error detecting method. An optical pickup and an optical disk device adjusted by the detection method can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of the configuration of an optical disc device incorporating an optical pickup adjusted by a tracking error detection method according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a configuration example of a part of the optical pickup of FIG. 1;

FIG. 3 is a cross-sectional view showing a cross section of the light receiving and emitting element of FIG. 2;

FIG. 4 is a circuit block diagram showing a tracking control circuit and a circuit for realizing a tracking error detection method according to the first embodiment of the present invention.

FIG. 5 is a view showing spots on the photodetector in FIG. 4;

FIG. 6 is a sectional view showing a state where a mirror is arranged on the optical pickup of FIG. 2;

FIG. 7 is a diagram showing spots on the photodetector of FIG. 4 at the time of reproduction of an optical disk or the like.

FIG. 8 is a circuit block diagram showing a tracking control circuit and a circuit for realizing a tracking error detection method according to a second embodiment of the present invention.

FIG. 9 is a circuit block diagram showing a tracking control circuit and a circuit for realizing a tracking error detection method according to a third embodiment of the present invention.

FIG. 10 is a diagram showing output characteristics of a first photodetector pair.

FIG. 11 is a diagram showing output characteristics of a second photodetector pair.

FIG. 12 is a diagram showing an amplitude with respect to a spot shift.

FIG. 13 is a view showing a state of a spot shift on the photodetector of FIG. 4;

FIG. 14 is a diagram showing a configuration example of an α-type circuit in FIG. 10;

FIG. 15 is a diagram showing a configuration example of a circuit of the β-F system in FIG. 10;

FIG. 16 is a diagram showing a configuration example of a circuit of the β-R system in FIG. 10;

FIG. 17 is a diagram showing a configuration example of a γ-type circuit in FIG. 10;

FIG. 18 is a cross-sectional view illustrating a configuration of a light receiving / emitting element of a conventional optical pickup.

FIG. 19 is a circuit block diagram showing a configuration of a conventional tracking control circuit.

[Explanation of symbols]

4. First photodetector pair (split photodetector)
5 ... second photodetector pair (split photodetector)
7a: semiconductor laser element (light emitting unit), 10: optical disk device, 11: optical disk, 13: optical pickup, 29: light receiving / emitting element, 39: selection switch, 39a ...・ Contact, 39b ... Contact, 41
... RF amplitude comparator, 42 ... DC amplitude comparator, 4
5 DC addition amplifier, 46 DC addition amplifier

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference)

Claims (7)

[Claims] 1. A light-emitting portion emits light, a return light reflected by a signal recording surface of an optical disk or a reflection surface equivalent thereto is received by a photodetector, and a position is determined based on an output signal of the photodetector. What is claimed is: 1. A tracking error detection method for obtaining a tracking error signal by a phase difference method, wherein output signals are respectively detected by at least two divided photodetectors in a tangential direction of an optical disc, and the output signals are set in advance. A tracking error detection method, wherein a comparison is made based on a criterion, the divided photodetector is selected according to the comparison result, and the tracking error signal is obtained by a phase difference method. 2. The tracking according to claim 1, wherein a criterion for selecting the split photodetector is that an amplitude is large when phase difference signals based on output signals from the split photodetectors are compared with each other. Error detection method. 3. The tracking error detection method according to claim 1, wherein a criterion for selecting the split photodetector is that the amplitude is small when reproduction signals output from the split photodetectors are compared with each other. 4. The tracking error detection method according to claim 1, wherein a criterion for selecting the divided photodetector is that the amount of received light among the divided photodetectors is small. 5. The tracking error detection method according to claim 1, wherein the selection of the split photodetector is performed at the stage of assembling the optical pickup. 6. A light source for emitting light, a light converging means for irradiating the light emitted from the light source so as to be focused on a signal recording surface of a rotationally driven optical disc, and two light converging means. A biaxial actuator for driving and adjusting in the axial direction; and a divided photodetector divided into at least two parts in the tangential direction of the optical disc, and an output signal from each of the divided photodetectors divided in at least two parts in the tangential direction of the optical disc. And detecting the output signals by comparing the output signals with each other based on a preset reference, selecting the split photodetector in accordance with the comparison result, and acquiring the tracking error signal by a phase difference method. An optical pickup characterized by the following. 7. A drive unit for rotating and driving an optical disk, and a light source irradiating the rotating optical disk with light from a light source via a light focusing unit, and returning the light from the signal recording surface of the optical disk to the light focusing unit. An optical pickup that is detected by a photodetector composed of at least two divided photodetectors in the tangential direction of the optical disc, and a biaxial actuator that supports the light converging means so as to be movable in biaxial directions. A signal processing circuit that generates a reproduction signal based on a detection signal from the photodetector; and a servo circuit that moves the light focusing unit in two axial directions based on the detection signal from the photodetector. Detecting an output signal with a split photodetector divided at least into two in the tangential direction of the optical disc, By comparing the signals based on a preset reference, the divided photodetector is selected according to the comparison result, and the tracking error signal is obtained by a phase difference method. Optical disk device.