JPH0714181A - Optical disk device - Google Patents

Abstract

PURPOSE:To obtain the optical disk device capable of stably operating a tracking servo and superior in read and write characteristics. CONSTITUTION:A moving optical part 10 is provided with a beam dislocation detecting part 12, to which a part of light emitted by a fixed optical part 20 is inputted. Then, an output signal of the beam dislocation detecting part is turned into a voltage signal proportional to a dislocation amt. of the emitting light of the fixed optical part, and the output signal of the beam dislocation detecting part and an output of a differential amplifier 22 are added up and outputted as a tracking error signal without a DC offset.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixed optical section for generating a laser beam for irradiating a recording medium and detecting a servo error signal and a read / write signal from the laser beam reflected from the recording medium. The present invention relates to an optical disc device including a so-called separation type optical head having a moving optical unit that irradiates a recording medium with laser light emitted from the recording medium and returns the laser beam reflected from the recording medium to a fixed optical unit.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing an example of a conventional optical disk device, and FIG. 4 is a schematic diagram showing a principle of a track error signal detecting operation of the push-pull type optical disk device shown in FIG. The figure which shows the case where the center line of the recording part of the recording medium and the optical axis of the optical head match, (b) shows that the optical axis of the optical head is shifted to the left with respect to the center line of the recording part of the recording medium. FIG. 5C shows a case where the optical axis of the optical head is shifted to the right with respect to the center line of the recording portion of the recording medium, and FIG. 5 shows a push-pull signal of the optical disk device of FIG. FIG. 6 is a characteristic diagram showing characteristics, FIG. 6 is a block diagram for explaining problems of the example of FIG. 3, and is a diagram showing a state when there is no positional deviation between the fixed optical unit and the moving optical unit, and FIG. FIG. 2 is a block diagram for explaining the problems of the example of FIG. Shows a state in which location shift has occurred, FIG. 8 is a characteristic diagram showing a push-pull signal in the state of FIG.

In order to realize high-speed access, an optical disk device generates a laser beam for irradiating a recording medium and a fixed optical section for detecting a servo error signal and a read / write signal from the laser beam reflected from the recording medium, A so-called separation type optical head in which a recording medium is irradiated with laser light emitted from a fixed optical section and the laser beam reflected from the recording medium is returned to the fixed optical section and is divided into two parts, a moving optical section. There are many.

Such a conventional optical disk device is shown in FIG.
As shown in FIG. 5, a spindle motor 60 is attached to a device base (not shown), and the information recording medium (recording medium) 61 is rotated by the spindle motor 60. Further, a fixed optical unit 50 having a light emitting element, a light receiving element, and an optical component is attached to the device base, and laser light is emitted from the fixed optical unit 50 to move optical as fixed optical unit outgoing light (moving optical unit incident light) 45. Incident on the section 40, and the moving optical section 4
At 0, the recording medium 61 is irradiated with the laser light, and the laser light reflected from the recording medium 61 is returned to the fixed optical unit 50 as reflected light (divided photodiode incident light) 46 of the information recording medium. In, the servo error signal and the read / write signal are detected from the reflected light.

The fixed optical section 50 is provided with a two-divided photodiode 51 having two photodiodes 51a and 51b (see FIG. 4).
1a and 51b are arranged symmetrically with respect to the center of the track of the recording medium 61.

The two-divided photodiode 51 receives the laser light reflected and diffracted by the guide groove of the recording medium 61, and outputs the output signal to the differential amplifier 52. The differential amplifier 52 inputs the output signal of the two-divided photodiode 51, amplifies the difference between them, and outputs a track error signal (push-pull signal) 53.

As shown in FIGS. 4 and 5, the push-pull method for detecting a track error is used as a recording medium 6 as shown in FIG.
The laser light reflected and diffracted by the first guide groove is received by the two-divided photodiode 51 in which the two photodiodes 51a and 51b are symmetrically arranged with respect to the center of the track, and the two photodiodes 51a are received. And 5
This is a method of calculating the difference between the output signals of 1b and outputting the track error signal (push-pull signal) 53.

That is, when the center line (track center) 61b of the recording portion 61a of the recording medium 61 and the optical axis of the optical head coincide with each other, the light is emitted from the objective lens 47 as shown in FIG. 4 (a). The beam of the generated laser light is recorded on the recording medium 6.
Since it coincides with the first recording unit 61a, the reflected and diffracted light amount 48a of the laser light reflected and diffracted by the recording unit 61a is symmetrical with respect to the track center 61b, and therefore the light amount received by the photodiode 51a and the photodiode 51b are equal. The amount of light received is equal. Therefore, the output signal of the photodiode 51a and the photodiode 51a
The output signal of b becomes equal, and the track error signal (push-pull signal) 53 of the output of the differential amplifier 52 becomes zero.

When the optical axis of the optical head is displaced to the left with respect to the center line of the recording portion 61a of the recording medium 61,
As shown in (b), the reflected and diffracted light amount 48b of the laser light reflected and diffracted by the recording portion 61a is the track center 6
The left side is stronger and the right side is weaker than 1b. Therefore, the amount of light received by the photodiode 51a becomes larger than the amount of light received by the photodiode 51b, and the output signal of the photodiode 51a becomes larger than the output signal of the photodiode 51b. The (push-pull signal) 53 becomes a positive signal.

If the optical axis of the optical head is shifted to the right with respect to the center line of the recording portion 61a of the recording medium 61, then FIG.
As shown in (c), the reflected and diffracted light amount 48c of the laser light reflected and diffracted by the recording portion 61a is the track center 6
The left side is stronger and the right side is weaker than 1b. Therefore, the amount of light received by the photodiode 51b becomes larger than the amount of light received by the photodiode 51a, and the output signal of the photodiode 51b becomes larger than the output signal of the photodiode 51a. The (push-pull signal) 53 becomes a negative signal.

The larger the deviation of the optical axis of the optical head from the center line of the recording portion 61a of the recording medium 61, the larger the recording portion 61a.
Since the difference between the left and right of the reflected and diffracted light quantity 48 of the laser light reflected and diffracted at is large, the track error signal (push-pull signal) 53 has the characteristics shown in FIG.

As shown in FIG. 3, the moving optical unit 40 can move in the radial direction of the recording medium 61 (direction of arrow A). The moving optical unit 40 is an optical prism 41 for directing the laser light incident from the fixed optical unit 50 toward the recording medium 61.
An objective lens drive device 44 for finely moving the objective lens 47 (see FIG. 4) in the focusing direction and the tracking direction, and a coarse movement motor for moving the optical prism 41 and the objective lens drive device 44 in the radial direction of the recording medium 61. 43 and irradiates the recording medium 61 with the laser beam incident from the fixed optical unit 50,
The laser light reflected from 1 is returned to the fixed optical unit 50.

The optical disk device configured as described above is
By minimizing the configuration of the moving optical unit 40, the weight is reduced and a high-speed access is realized.

[0014]

In the conventional optical disk device as described above, there is a step between the fixed optical part and the movable optical part in the inner peripheral part or the outer peripheral part of the recording medium caused by distortion of the device base or the like, and If the laser light incident on the moving optical unit shifts due to the inclination of the output light of the fixed optical unit caused by changes, etc., the detection signal of the fixed optical unit will be affected, and the track error signal (push-pull signal) will have a DC However, there is a problem that the offset occurs.

That is, as shown in FIG. 6, when there is no positional deviation (step) in the direction of arrow F between the fixed optical section 50 and the moving optical section 40, the beam of the laser light emitted from the objective lens 47. Is the same as the recording section 61a of the recording medium 61, the output signal of the photodiode 51a and the output signal of the photodiode 51b become equal, and the track error signal (push-pull signal) 53 of the output of the differential amplifier 52 is obtained. Is 0.

However, as shown in FIG. 7, the moving optical unit 4
When 0 shifts in the direction of the arrow G with respect to the fixed optical unit 50 and a position shift (step) occurs between the two, the information recording medium reflected light (two-division photodiode incident light) 46 changes to the arrow B.
Since it moves in the direction, the amount of light received by the photodiode 51a becomes larger than the amount of light received by the photodiode 51b. Therefore, even when the beam of the laser light emitted from the objective lens 47 coincides with the recording portion 61a of the recording medium 61, the output signal of the photodiode 51a and the output signal of the photodiode 51b do not become equal and the differential amplifier The track error signal (push-pull signal) 53 output from 52 does not become 0.

At this time, the track error signal (push-pull signal) 53 is in a state where the DC offset X is generated, as shown in FIG. This DC offset X is 2
It is proportional to the amount of deviation of the information recording medium reflected light (two-divided photodiode incident light) 46 on the divided photodiode 51, that is, the amount of deviation of the fixed optical portion emitted light (moving optical portion incident light) 45.

If a DC offset X is generated in the track error signal (push-pull signal) in the optical disk device, the tracking servo will not operate stably and the read / write characteristics will be adversely affected.

[0019]

An optical disk apparatus according to the present invention is a fixed optical section for generating a laser beam for irradiating a recording medium and detecting a servo error signal and a read / write signal from the laser beam reflected from the recording medium. A moving optical unit that irradiates the recording medium with the laser light emitted from the fixed optical unit and returns the laser light reflected from the recording medium to the fixed optical unit; and the fixed optical unit.
In an optical disc device including a differential amplifier that outputs an output signal of a split photodiode and outputs a push-pull signal, a part of the emitted light of the fixed optical unit is input and a voltage signal proportional to the positional deviation amount is generated. A beam position deviation detecting section for outputting and an arithmetic section for inputting an output signal of the beam position deviation detecting section and the push-pull signal and outputting a signal of a sum thereof are provided. Beam misregistration detector for inputting a part of the light emitted from the part and outputting a current signal proportional to the amount of misregistration, and a current signal output from the beam misregistration detector for conversion into a voltage signal A beam position deviation detection unit having a converter is provided.

[0020]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a characteristic diagram showing signals of respective parts of the embodiment of FIG. 1, in which (a) is a push-pull signal. And (b) is a characteristic diagram showing the output signal of the first arithmetic unit,
(C) is a characteristic diagram showing a track error signal.

In FIG. 1, a fixed optical unit 20 having a spindle motor 30, an information recording medium (recording medium) 31, and a two-divided photodiode 21 which receives reflected light (two-divided photodiode incident light) 16 from the information recording medium and a differential optical unit. The configuration and operation of the dynamic amplifier 22 are shown in FIG.
This is the same as the configuration and operation of the corresponding part of the conventional example.

The moving optical unit 10 has an optical prism 11, an objective lens 17, an objective lens driving device 14, a coarse movement motor 13 and a beam position deviation detector 12.

The structures and operations of the objective lens 17, the objective lens driving device 14 and the coarse movement motor 13 are the same as those of the corresponding parts of the conventional example of FIG. 3, respectively. The optical prism 11 directs a part of the fixed optical part emitted light (moving optical part incident light) 15 from the fixed optical part 20 toward the recording medium 31, and the rest of the beam position deviation detector 1.
The laser light reflected from the recording medium 31 is directed toward the information recording medium 31 and reflected by the information recording medium (two-division photodiode incident light).
It is returned to the fixed optical unit 20 as 16.

The beam position shift detector 12 has a fixed optical portion emitted light (moving optical portion incident light) 15 from the optical prism 11.
Part of the incident light is detected, a positional deviation (step) in the direction of arrow F is detected, and a current signal proportional to the amount of deviation is output. The output signal of the beam position shift detector 12 is converted into a voltage signal in the first arithmetic unit 24 and output as a first arithmetic unit output signal 25.

As shown in FIG. 2 (b), the output signal 25 of the first arithmetic unit is the output light of the fixed optical unit (incident light of the moving optical unit) 1
DC offset X (see FIG. 2A) generated in the track error signal (push-pull signal) 23 of the output of the differential amplifier 22 due to the positional deviation in the direction of arrow F when 5 enters the moving optical unit 10. The signals are equal in magnitude but opposite in polarity.

Track error signal (push-pull signal)
23 and the output signal 25 of the first calculation unit are output to the second calculation unit 26.
To enter. The second calculation unit 26 adds them and outputs the second calculation unit output signal 27. This second arithmetic unit output signal 27 becomes a track error signal having no DC offset, as shown in FIG. 2 (c).

[0028]

As described above, in the optical disk device of the present invention, the moving optical unit is provided with the beam position deviation detecting unit for inputting a part of the light emitted from the fixed optical unit, and the output signal of the beam position deviation detecting unit is output. Tracking servo is performed by using a voltage signal proportional to the amount of deviation of the output light from the fixed optical unit, adding the output signal of the beam position deviation detector and the output of the differential amplifier, and outputting it as a track error signal with no DC offset. This has the effect of enabling stable operation, and thus has the effect of providing an optical disk device with excellent read / write characteristics.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing signals of various parts of the embodiment of FIG.
(A) is a characteristic diagram showing a push-pull signal, (b) is a characteristic diagram showing a first arithmetic unit output signal, and (c) is a characteristic diagram showing a track error signal.

FIG. 3 is a block diagram showing an example of a conventional optical disc device.

4A and 4B are schematic diagrams showing the principle of the detection operation of the track error signal of the optical disc apparatus of FIG. 3, where FIG. 4A shows the case where the center line of the recording portion of the recording medium and the optical axis of the optical head are aligned. FIG. 2B is a diagram showing a case where the optical axis of the optical head is displaced to the left with respect to the center line of the recording portion of the recording medium,
FIG. 6C is a diagram showing a case where the optical axis of the optical head is displaced to the right with respect to the center line of the recording portion of the recording medium.

5 is a characteristic diagram showing characteristics of a push-pull signal of the optical disk device of FIG.

6 is a block diagram for explaining the problem of the example of FIG. 3, and is a diagram showing a state when there is no positional deviation between the fixed optical unit and the moving optical unit.

7 is a block diagram for explaining the problem of the example of FIG. 3, and is a diagram showing a state when a positional deviation occurs between a fixed optical unit and a moving optical unit.

8 is a characteristic diagram showing a push-pull signal in the state of FIG.

[Explanation of symbols]

10/40 Moving optical part 11/41 Optical prism 12 Beam position deviation detector 13/43 Coarse movement motor 14/44 Objective lens driving device 15/45 Fixed optical part outgoing light (moving optical part incident light) 16/46 Information recording Medium reflected light (two-division photodiode incident light) 17/47 Objective lens 20/50 Fixed optical part 21/51 Two-division photodiode 22/52 Differential amplifier 23/53 Track error signal (push-pull signal) 24 First calculation Part 25 First calculation unit output signal 26 Second calculation unit 27 Second calculation unit output signal 30/60 Spindle motor 31/61 Information recording medium (recording medium) 48a / 48b / 48c Reflected diffracted light quantity 51a / 51b Photodiode 61a Recording Part 61b Center line (track center)

Claims (2)

[Claims] 1. A fixed optical section which generates a laser beam for irradiating a recording medium and detects a servo error signal and a read / write signal from the laser beam reflected from the recording medium; and the fixed optical section which is emitted from the fixed optical section. A moving optical unit that irradiates the recording medium with the laser beam and returns the laser beam reflected from the recording medium to the fixed optical unit, and an output signal of a two-divided photodiode of the fixed optical unit is input to push-pull. In an optical disk device including a differential amplifier that outputs a signal, a beam position deviation detection unit that inputs a part of the emitted light of the fixed optical unit and outputs a voltage signal proportional to the position deviation amount; An optical disk device, comprising: an arithmetic unit for inputting an output signal of a shift detecting unit and the push-pull signal and outputting a signal of a sum thereof. 2. A beam position deviation detector for inputting a part of the light emitted from the fixed optical section and outputting a current signal proportional to the position deviation amount, and a current signal output from the beam position deviation detector. 2. A beam position deviation detection unit having a converter for converting the voltage signal into a voltage signal is provided.
The optical disk device described.