JPH09115148A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a stable track follow-up characteristic by prevent the decrease of the gain of a tracking error signal even if a sliding base and the arm of a biaxial driving section are extended by a temp. rise. SOLUTION: This pickup device supports an optical pickup 5 having an objective lens 7, an optical block, etc., on the sliding base 2 freely movable in a direction orthogonal with the recording track line direction of an optical disk 3 by means of the biaxial driving section 6 for moving the pickup in a focusing direction and a tracking direction and detects the tracking error signal by a three spot system. In such a case, the mounting section 9 of the sliding base 2 of the biaxial driving section 6 is positioned on the side opposite to a shaft 4 freely slidably supporting the sliding base 2 interposing the objective lens 7 between them.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel optical pickup device. Specifically, in an optical pickup device that obtains a tracking error signal by a so-called three-spot method, a three-spot array is formed by expansion and contraction due to temperature of a slide base on which the optical pickup is mounted, a biaxial driving unit that supports the optical pickup, and the like. The present invention relates to a technique for preventing the gain of a tracking error signal from decreasing due to a change in the angle of the direction with respect to the track line direction.

[0002]

2. Description of the Related Art FIGS. 5 to 7 schematically show a conventional optical pickup device.

One end of the slide base a is slidably supported by a shaft b, and the slide base a is in the radial direction of the optical disc c.
That is, the optical disk is moved in a direction orthogonal to the track line direction of the recording track formed on the optical disk c, that is, in the direction indicated by arrow A in FIG.

Optical pickup e having an objective lens d
Are supported on the side of the slide base a facing the optical disc c via the biaxial drive part f, and the objective lens d is orthogonal to the optical disc c by the biaxial drive part f, that is, the focusing direction (arrow). F) and the radial direction of the optical disk c, that is, the tracking direction (arrow T).
It is designed to be moved in the direction indicated by.

The optical pickup device obtains a tracking error signal by the so-called three-spot method and controls the tracking of the optical pickup e accordingly. That is, as shown in FIG. 7, the light emitted from the light source is divided into 0th-order light g0 (main spot), + 1st-order light + g1, and -1st-order light -g1 by a grating (diffraction grating), and is divided by the main spot g0. Writes and reads signals, + 1st order light + g
A difference signal (EF) signal between the E signal detected from 1 and the F signal detected from −1st order light −g1 is detected as a tracking error signal to perform tracking.

[0006]

By the way, the above-mentioned 3
In the method of obtaining the tracking error signal by the spot method, the slide base a and the biaxial drive section f are increased due to the temperature rise.
When the arm of the optical disk extends, so-called Rd shift (R is the distance from the center of the optical disk c to the center of the main spot g0, d is the main spot g when the spot position is shifted).
0 from the initial position, d = 0 and E signal and F
The phase difference with the signal is designed to be 180 degrees. ), The phase difference between the E signal and the F signal (hereinafter referred to as “E
F phase difference ". ) Is deviated from 180 degrees, the gain of the tracking error signal decreases, and there is a problem that the track following becomes unstable.

The state shown by the solid line in FIG. 7 is a normal state of three spots, that is, the state of d = 0. In this state, as shown in the graph on the left side of FIG. Is 1
With a phase difference of 80 degrees, the (EF) signal has maximum gain. When d = 0, the phase difference between the E signal and the F signal does not change at the inner circumference and the outer circumference of the optical disk c.

However, when the temperature of the slide base a and the arms of the biaxial drive part f expands as shown in FIG. 6 due to the temperature rise (the extending direction of the slide base a is indicated by a solid arrow, the arm of the biaxial drive part f is The extension direction is indicated by a dashed arrow, the extension amount of the slide base a is Δd1, and the extension amount of the arm of the biaxial drive unit f is Δd2.), D = d1
+ D2> 0, so-called Rd shift occurs, the angle of the arrangement direction of the three spots with respect to the track line direction h changes, and the EF phase difference is 1 as shown in the graph on the right side of FIG.
The gain deviates from 80 degrees, and the gain of the (EF) signal decreases. Then, the larger the value of d and the closer to the inner circumference of the optical disc c, the greater the angle change with respect to the track line direction h of the arrangement direction of the three spots, and the phase difference between the E signal and the F signal from 180 degrees. The gap is large. This situation is shown in the graph of FIG. In the graph, the horizontal axis is R
(Mm), the vertical axis represents the EF phase difference (deg), and the line types shown on the right side are as follows.
Dotted lines indicate −1st order light, and the numerical value on the right side of the line type indicates d (mm). In addition, only for d = 0, the 0th order light, the + 1st order light, and the −1st order light are shown by solid lines.

In view of this, the present invention provides stable track followability by preventing the gain of the tracking error signal from decreasing even if the slide base or the arm of the biaxial drive section expands due to temperature rise. It is an issue.

[0010]

In order to solve the above problems, the optical pickup device of the present invention slidably supports the slide base with the objective lens sandwiching the mounting portion of the biaxial drive unit to the slide base. It is located on the opposite side of the shaft.

Therefore, according to the present invention, the extension due to the temperature rise of the arm of the biaxial drive portion is canceled by the extension due to the temperature rise of the slide base, and the angle of the arrangement direction of the three spots with respect to the track line direction changes. Therefore, the gain of the tracking error signal is prevented from decreasing.

In another optical pickup device of the present invention, one end of a shaft that slidably supports a slide base is rotatably supported, and a free end, which is the other end, is moved according to a temperature change. It was done like this.

Therefore, according to the present invention, by moving the free end of the shaft and inclining the slide base with respect to the track line direction, the angle of the arrangement direction of the three spots with respect to the track line direction is corrected to a normal state. Therefore, it is possible to suppress the decrease in the gain of the tracking error signal.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The details of the optical pickup device of the present invention will be described below with reference to the illustrated embodiments.

1 and 2 schematically show a first embodiment 1 of the optical pickup device of the present invention.

The slide base 2 is slidably supported by a shaft 4 extending parallel to a line passing through the center of the optical disc 3, and is moved in a direction orthogonal to the track line direction of the optical disc 3 by a driving means (not shown). It has become.

An optical pickup 5 is supported on the side of the slide base 2 facing the optical disk 3 via a biaxial drive section 6. The optical pickup 5 includes an objective lens 7, an optical block including a light source, a photodetector, and the like, and required members (not shown). Light emitted from the light source irradiates the recording surface of the optical disc 3 through the objective lens. Then, the signal is recorded, or the return light reflected by the recording surface of the optical disc 3 is detected to read the recorded signal. In addition, the light emitted from the light source is converted into the 0th-order light g0 (main spot), +1 by a grating (diffraction grating).
Main light g is divided into next light + g1 and -1st light -g1.
Signals are written and read by 0, + 1st order light +
A difference signal (EF) signal between the E signal detected from g1 and the F signal detected from −1st-order light −g1 is detected as a tracking error signal to perform tracking.

An arm 8 of the biaxial drive section 6 is supported by the slide base 2 via a mounting section 9. The optical pickup 5 is moved by the biaxial drive unit 6 in the direction orthogonal to the recording surface of the optical disc 3, that is, in the focusing direction and the radial direction of the optical disc 3, that is, in the tracking direction.

The mounting portion 9 is the slide base 2
It is located on the opposite side of the shaft 4 with the objective lens 7 interposed therebetween.

Therefore, in the optical pickup device 1 described above, even if the slide base 2 and the arm 8 of the biaxial drive unit 6 extend due to the temperature rise, the extension direction of the slide base 2 (solid line arrow 10 in FIG. 2). 2) and the extension direction of the arm 8 of the biaxial drive unit 6 (indicated by the dashed arrow 11 in FIG. 2) are opposite to each other, and the slide base 2
Expansion amount Δd1 and expansion amount Δd1 of the arm 8 of the biaxial drive unit 6
2 and 2 act to cancel each other, and d = Δd1−Δd2
Therefore, the Rd shift does not occur or becomes small even if the Rd shift occurs, the EF phase difference does not largely deviate from 180 degrees, and the gain of the tracking error signal is maintained.

3 and 4 show a second embodiment 1A of the optical pickup device of the present invention.

The slide base 12 is slidably supported by a shaft 13 extending in parallel with a line passing through the center of the optical disc 3, and is moved in a direction orthogonal to the track line direction of the optical disc 3 by a driving means (not shown). It has become.

On the side of the slide base 12 facing the optical disc 3, the optical pickup 14 is provided with the biaxial drive unit 1.
5 is supported. The optical pickup 14 includes an objective lens 16, an optical block including a light source, a photodetector, and the like, and required members (not shown). Light emitted from the light source irradiates the recording surface of the optical disc 3 through the objective lens. Then, the signal is recorded, or the return light reflected by the recording surface of the optical disc 3 is detected to read the recorded signal. Further, the light emitted from the light source is divided into 0th-order light g0 (main spot), + 1st-order light + g1, and -1st-order light -g1 by a grating (diffraction grating), and a signal is written and read by the main spot g0. ,
E signal detected from + 1st order light + g1 and -1st order light -g1
A tracking error signal is detected by detecting a difference signal (E−F) signal from the F signal detected from the tracking error signal.

An arm 17 of the biaxial drive section 15 is supported by the slide base 2 via a mounting section 18. The optical pickup 14 is moved by the biaxial drive unit 15 in the direction orthogonal to the recording surface of the optical disc 3, that is, the focusing direction and the radial direction of the optical disc 3, that is, the tracking direction.

The mounting portion 18 is located on the slide base 12 closer to the shaft 13 than the objective lens 16.

The shaft 13 is rotatably supported at one of its supporting ends, that is, the end 19a located on the outer peripheral side of the optical disc 3, and the other end, that is, the inner peripheral side of the optical disc 3. The end portion 19b located at is a free end. The outer end 19a of the shaft 13 is supported by a chassis (not shown) by a support member 20, and the shaft 13
The free end 19b of is supported by a support member 21 that is movable with respect to a chassis (not shown).

The mounting member 22 is made of a material that expands when the temperature rises, and one end of the mounting member 22, that is, the end 22a opposite to the side facing the support member 21 is fixed to a chassis (not shown), and the fixed end 22a The support member 21 is elastically contacted to the opposite end 22b by an elastic member, for example, a spring 23.

Therefore, the above optical pickup device 1A
In this case, even if the slide base 12 or the arm 17 of the biaxial drive unit 15 expands due to the temperature rise and the position of the objective lens 16 moves from the normal position, at the same time, The mounting member 22 also expands and its supporting end 22b moves in the direction indicated by the arrow 24 in FIG. 3, whereby the free end 19b of the shaft 13 moves in the direction indicated by the arrow 24, and the shaft 13 is moved from the initial position. The direction in which the tilt, the optical pickup 14, and more specifically the moving direction of the objective lens 16 is always directed to the center of the optical disc 3, that is,
The direction is orthogonal to the track line direction (shown by the one-dot chain line in FIG. 4) or the direction substantially orthogonal to the track line direction. Therefore, the angles of the arrangement directions of the spots g0, + g1, and -g1 with respect to the track line direction hardly change. Therefore, the Rd shift does not occur or the Rd shift occurs only slightly, and the EF phase difference is small. The gain of the tracking error signal is maintained without largely deviating from 180 degrees.

In the second embodiment, the mounting member 22 is not made of a material that expands due to a temperature rise.
For example, the temperature is detected by a temperature sensor which is formed by using a ceramic piezoelectric element and is arranged at an appropriate location, and an appropriate voltage is applied to the ceramic piezoelectric element in accordance with the temperature so that the free end 19b of the shaft 13 is moved. You may make it move in parallel.

In addition, both ends of the shaft supporting the slide base are movably supported, and R
Both ends of the shaft may be moved in a direction of canceling the deviation.

[0031]

As is apparent from what has been described above, the optical pickup device of the present invention includes an optical pickup having an objective lens, an optical block, etc., via a biaxial drive portion for moving the optical pickup in the focusing direction and the tracking direction. In the optical pickup device, which is supported by a slide base movable in a direction orthogonal to a recording track line direction of an optical recording medium to detect a tracking error signal by a three-spot method, the slide base of the biaxial drive section is provided. The mounting portion is attached to the opposite side of the shaft that slidably supports the slide base with the objective lens interposed therebetween.

Therefore, according to the present invention, the extension due to the temperature rise of the arm of the biaxial drive section is canceled by the extension due to the temperature rise of the slide base, and the angle of the arrangement direction of the three spots with respect to the track line direction changes. Therefore, the gain of the tracking error signal is prevented from decreasing. As a result, stable track followability can be obtained.

Further, another optical pickup device of the present invention is a recording track line of an optical recording medium via a biaxial drive section for moving an optical pickup having an objective lens, an optical block and the like in a focusing direction and a tracking direction. In an optical pickup device that is supported by a slide base that is movable in a direction orthogonal to the direction and detects a tracking error signal by a 3-spot method, one end of a shaft that slidably supports the slide base is rotated. It is movably supported, and the free end, which is the other end, is moved according to the temperature change.

Therefore, according to the present invention, by moving the free end of the shaft and inclining the slide base with respect to the track line direction, the angle of the arrangement direction of the three spots with respect to the track line direction is corrected to a normal state. Therefore, it is possible to suppress the decrease in the gain of the tracking error signal. This makes it possible to obtain stable track followability.

[Brief description of the drawings]

FIG. 1 is a first of the optical pickup device of the present invention together with FIG.
This figure shows an embodiment of the present invention, and is a schematic perspective view.

FIG. 2 is a schematic plan view.

FIG. 3 is a second of the optical pickup device of the present invention together with FIG.
This figure shows an embodiment of the present invention, and is a schematic perspective view.

FIG. 4 is a schematic plan view showing the operation.

5 shows an example of a conventional optical pickup device together with FIGS. 6 and 7, and is a schematic perspective view.

FIG. 6 is a schematic plan view.

FIG. 7 is a schematic plan view showing a problem.

FIG. 8 is a graph showing the gain of the tracking error signal, in which the left side shows the EF phase difference of 180 degrees, and the right side shows the EF phase difference deviated from 180 degrees.

FIG. 9 is a graph showing the effect of Rd shift on the EF phase difference.

[Explanation of symbols]

 1 Optical Pickup Device 2 Slide Base 3 Optical Disc (Optical Recording Medium) 4 Shaft 5 Optical Pickup 6 2 Axis Drive 7 Objective Lens 9 Attachment 1A Optical Pickup 12 Slide Base 13 Shaft 14 Optical Pickup 15 2 Axis Drive 16 Objective lens 19a One end of shaft 19b Free end of shaft 22 Attachment member (member that expands and contracts depending on temperature)

Claims (5)

[Claims] 1. An optical pickup having an objective lens, an optical block, and the like is movable in a direction orthogonal to a recording track line direction of an optical recording medium through a biaxial driving unit that moves the optical pickup in a focusing direction and a tracking direction. In an optical pickup device supported on a slide base and detecting a tracking error signal by a three-spot method, the attachment part of the biaxial drive part to the slide base is slidable with the objective lens sandwiched therebetween. An optical pickup device characterized in that it is located on the side opposite to the supporting shaft. 2. An optical pickup having an objective lens, an optical block, etc., is movable in a direction orthogonal to a recording track line direction of an optical recording medium via a biaxial drive section that moves the optical pickup in a focusing direction and a tracking direction. In an optical pickup device which is supported by a slide base and detects a tracking error signal by a three-spot method, one end of a shaft which slidably supports the slide base is rotatably supported, and the other end thereof is rotatably supported. An optical pickup device characterized in that a free end is moved according to a temperature change. 3. The optical recording medium is an optical disc,
The optical pickup device according to claim 2, wherein the free end of the shaft is located on the inner peripheral side of the optical disc. 4. The optical pickup device according to claim 2, wherein the free end of the shaft is elastically pressed against and held by a member that expands and contracts according to temperature. 5. The optical pickup device according to claim 3, wherein the free end of the shaft is elastically pressed against and held by a member that expands and contracts according to temperature.