JPH09204675A - Optical pickup and optical disc apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a horizontal light path from a light source to a rising mirror by a method wherein a collimator lens is provided between the rising mirror and an object lens. SOLUTION: A collimator lens 25 is, a convex lens and converts a light beam reflected by a rising mirror 24 into a parallel light. For this purpose, the collimator lens 25 is provided in a light path which is bent by the rising mirror 24, i.e., in a light path perpendicular to the signal recording surface of an optical disc. With this constitution, the distance between a beam splitter 23 and the rising mirror 24 and the light path length from a semiconductor laser device 21 which is a light source to the rising mirror 24 can be selected to be shorter, so that the sizes of a double-axis actuator 30, an optical pickup 20, an optical disc apparatus 10, etc., can be reduced. Further, as the collimator lens 25 is provided between an object lens 26 and the rising mirror 24, a support shaft 32 is relatively long and hence a lens holder 32 can be held stably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compact disc (CD), a CD-ROM, a magneto-optical disc, etc.
The present invention relates to an optical pickup and an optical disc device for recording and / or reproducing a signal (referred to as “optical disc”), and particularly to an optical pickup and an optical disc device capable of reproducing a plurality of types of optical discs.

[0002]

2. Description of the Related Art Conventionally, an optical pickup for reproducing an optical disk has, for example, a semiconductor laser element as a light emitting means, a collimator lens for converting light from the semiconductor laser element into parallel light, and a parallel light from the collimator lens. Mirror as an optical path bending mirror that reflects in the direction of, an objective lens that irradiates the optical disk with the reflected light beam from the illuminating mirror, and an objective lens that holds this objective lens so that it can move in two axial directions. A biaxial actuator as an actuator, a photodetector that detects the return light from the optical disk, and a servo circuit that drives and controls the objective lens of the biaxial actuator in the focusing direction and the tracking direction based on the detection signal of the photodetector. It consists of and.

In such an optical pickup, a light beam from a light source is converted into parallel light by a collimator lens, an optical path is bent in the direction of the optical disk by a raising mirror, and the objective lens irradiates the signal recording surface of the optical disk. Then, the return light reflected by the signal recording surface is received by the light receiving surface of the photodetector to detect the recording signal.

In order to accurately detect the reproduced signal, it is necessary for the light beam from the light source to form a spot at the correct position on the signal recording surface of the optical disc. for that reason,
In the optical pickup, the objective lens that focuses the light beam from the light source on the signal recording surface of the optical disc is finely moved based on a predetermined servo signal. The servo of the objective lens includes a tracking servo for finely moving the objective lens along the radial direction of the disc with respect to the recording track of the optical disc, and a direction for approaching and separating from the signal recording surface of the optical disc along the optical axis. Focusing servo for finely moving the objective lens is performed.

[0005]

In the optical pickup having such a structure, a collimator lens for converting the light beam from the semiconductor laser element into parallel light is provided between the semiconductor laser element and the raising mirror. It is installed in. Therefore, the distance from the semiconductor laser element to the raising mirror becomes relatively long. Therefore, there is a problem that the optical pickup and the entire optical disk device are relatively large in a plane parallel to the optical disk.

In view of the above points, an object of the present invention is to provide an optical pickup and an optical disk apparatus using the same, in which the horizontal optical path from the light source to the optical path bending mirror is configured to be short. .

[0007]

According to the present invention, the above object is to provide an objective lens which irradiates a light beam emitted from a light source and reflected by an optical path bending mirror so as to focus on a signal recording surface of an optical disk. A collimator lens arranged between an optical path bending mirror and an objective lens, a light separating means for separating a light beam emitted from the light source onto the optical disk and a return light beam reflected on a signal recording surface of the optical disk. And an optical detector including a photodetector having a light receiving unit that receives a return light beam from the signal recording surface of the optical disc.

According to the above arrangement, the collimator lens for converting the light beam from the light source into parallel light is arranged between the optical path bending mirror and the objective lens. Therefore, since the collimator lens is not provided between the light source and the optical path bending mirror, the optical path length from the light source to the optical path bending mirror is shortened. As a result, the optical pickup and the entire optical disc device are downsized.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described in detail with reference to FIGS.
The embodiment described below is a preferred specific example of the present invention, and thus various technically preferable limitations are added. However, the scope of the present invention particularly limits the present invention in the following description. The embodiment is not limited to these embodiments unless otherwise stated.

FIG. 1 shows an embodiment of an optical disk device incorporating an optical pickup according to the present invention.
In FIG. 1, an optical disk device 10 includes an optical disk 11
Spindle motor 12 as a driving means for rotationally driving the motor
And an optical pickup 13.

The spindle motor 12 is drive-controlled by the optical disk drive controller 14 and rotated at a predetermined rotation speed. As the optical disk 11, a plurality of types of optical disks can be selected and reproduced.

Further, the optical pickup 13 irradiates the signal recording surface of the rotating optical disc 11 with light to record a signal, or detects return light from the signal recording surface. The reproduction signal based on the returning light is output to the signal demodulator 15.

As a result, the recording signal demodulated by the signal demodulator 15 is error-corrected via the error correction circuit 16 and sent to an external computer or the like via the interface 17. Thus, an external computer or the like can receive a signal recorded on the optical disk 11 as a reproduction signal.

The optical pickup 13 is connected to a head access control section 18 for moving a predetermined recording track on the optical disk 11 by a track jump or the like. Further, at the moved predetermined position, a servo circuit 19 for moving the objective lens in the focusing direction and the tracking direction is connected to a biaxial actuator (described later) that holds the objective lens of the optical pickup 13. There is.

FIG. 2 shows an optical pickup incorporated in the optical disk device 10. In FIG.
The optical pickup 20 includes a semiconductor laser element 21, a grating 22 as a light splitting means, a beam splitter 23 as a light splitting means, a rising mirror 24, a collimator lens 25, an objective lens 26, a photodetector 27, and an objective lens 26. It is composed of a biaxial actuator 30 for moving in a biaxial direction.

The semiconductor laser device 21 is a light emitting device utilizing recombination emission of semiconductors and is used as a light source. The light beam emitted from the semiconductor laser device 21 is
It is guided to the grating 22.

The grating 22 is a diffraction grating for diffracting incident light, and the light beam emitted from the semiconductor laser device 21 is at least three of a main beam composed of 0th-order diffracted light and a side beam composed of plus / minus 1st-order diffracted light. Used to split the light beam into. Therefore, another splitting element such as a hologram element may be used as long as it can split and generate at least three light beams.

The beam splitter 23 is arranged with its reflection surface inclined by 45 degrees with respect to the optical axis, and separates the light beam from the grating 22 and the return light from the signal recording surface of the optical disk 11. That is, the light beam from the semiconductor laser device 21 is reflected by the reflecting surface 23 a of the beam splitter 23, and the return light is the beam splitter 23.
Through.

As shown in FIGS. 3 and 4, the raising mirror 24 is an optical path bending means and is a beam splitter 2.
The light beam reflected by 3 is reflected upward by 90 degrees, and the return light from the optical disk 11 is reflected in the horizontal direction. In this case, the rising mirror 24 is selected and arranged so that its tilt direction forms an angle of 45 degrees with respect to the track direction of the optical disk 11, that is, the tangential direction of the track (shown by the chain line L in FIG. 2). Has been done. Thereby, as will be described later, in the first light receiving portion shown in FIGS. 12 and 13, the focus error can be detected by the astigmatism method and the tracking error can be detected by the phase comparison method.

As shown in FIGS. 3 and 4, the collimator lens 25 is a convex lens and converts the light beam reflected by the rising mirror 24 into parallel light. In this case, the collimator lens 25 is arranged in the optical path bent by the rising mirror 24, that is, in the optical path perpendicular to the signal recording surface of the optical disc. As a result, the distance between the beam splitter 23 and the rising mirror 24 and the optical path length from the semiconductor laser element 21 as the light source to the rising mirror 24 are selected to be relatively short, and the biaxial actuator 30 and the optical axis are selected. The pickup 20 and further the optical disk device 10 are made compact. Further, since the collimator lens 25 is disposed between the objective lens 26 and the rising mirror 24, the support shaft 32
Is relatively long, and the lens holder 3
3 will be held stably.

Further, the collimator lens 25 is shown in FIG.
As shown in (b) and FIG. 5, the side edge on the support shaft 32 side is 2
It is cut as shown by 5a. As a result, the support shaft 32 and the focusing coil 3 arranged around the support shaft 32 are provided.
4, It does not interfere with the focusing yoke 36 and the focusing magnet 37. Further, such a cut 25a is formed by moving the objective lens in the tracking direction as shown in FIG.
The optical path is formed parallel to the moving direction B1. Therefore, even if the cut portion 25a is formed on the side edge of the collimator lens 25, the optical disc 1 of the collimator lens 25 is formed.
The length of 1 in the track direction does not become short. Therefore, the tracking error signal is not adversely affected.

As shown in FIGS. 3 and 4, the objective lens 26 is a convex lens, and images the parallel light from the collimator lens 25 on a desired track on the signal recording surface of the rotatably driven optical disk 11. Let

The objective lens 26 is movably supported in a biaxial direction, that is, in the focusing direction and the tracking direction by a biaxial actuator 30 of a shaft sliding type, and is compatible with two different types of optical disks. Two objective lenses 26a, 26b designed to
And the biaxial actuator 30 as described below.
It is supported by a lens holder which is a movable part of so as to be selectively inserted into the optical path.

The photodetector 27 has a light receiving portion for the return light beam that has passed through the beam splitter 23. The structure of the divided light receiving portion of the photodetector 27 is shown in FIGS. 12 and 13.

Then, the semiconductor laser device 21, the grating 22, the beam splitter 23, and the raising mirror 2
4, the collimator lens 25 and the photodetector 27 are fixedly arranged on the biaxial base 31 which is a fixed part of the biaxial actuator 30.

7 and 8 show the structure of the biaxial actuator 30. 7 and 8, the biaxial actuator 30 is skew-adjusted and attached to an optical base 29 that is supported by the optical pickup 20 of FIG. 2 so as to be movable in the radial direction of the optical disk 11 along a guide 28. A shaft base 31, a support shaft 32 extending vertically on the biaxial base 31, and a substantially oval shape supported by the support shaft 32 so as to be movable in the axial direction and rotatable about the shaft. Rectangular lens holder 33
And two objective lenses 26a and 26b whose optical axes are held parallel to the support axis at a predetermined distance from the rotation axis of the lens holder and at different angular positions.

Here, the objective lens 26a is a lens having a relatively large numerical aperture NA (for example, NA = 0.6) for a high density optical disc which is, for example, a second type of optical disc, and is of the first type. Objective lens 2 with a relatively small numerical aperture (NA = 0.38) for optical discs (for example, CDs)
The diameter is larger than 6b. An objective lens 26b having a relatively small diameter is arranged on the rotation center side of the optical disc 11.

Further, the lens holder 33 is shown in FIG.
As shown in FIG. 3, a concentric cylindrical focusing coil 34 is attached to the lower side, and a pair of tracking coils 35 and 35 are attached to end surfaces on opposite sides with respect to the rotation axis thereof. ing.

On the other hand, on the biaxial base 31 of the biaxial actuator 30, a pair of focusing yokes 36 are arranged so as to face the focusing coil 34 on the opposite sides from the outside. , 36, and a pair of focusing magnets 37 mounted inside thereof,
37, tracking yokes 38 and 38 arranged to face the tracking coil 35 from the outside, respectively, and a pair of tracking magnets 39 and 39 attached to the inside thereof. .

The focusing coil 34 is formed with a small diameter so as to be arranged relatively close to the peripheral surface of the support shaft 32 separately from the tracking coil 35. The focusing yoke 36 and the magnet 37 are also close to the support shaft 32. As a result, the focusing coil 34 can be made compact as a whole and the effective conductor length can be increased.

The tracking magnet 39 is also used.
Are configured so that the polarities are opposite to each other with respect to the left and right from the center in the axial direction. For example, as shown in FIG. 9, the tracking magnet 39 has a support shaft 3
Regarding No. 2, the S pole 39a and the N pole 39b are arranged clockwise.

Further, on both sides in the circumferential direction of the tracking coil 35, magnetic bodies extending in the axial direction, for example, iron pieces 40 and 41 are attached. As a result, either one of the iron pieces 40 or 41 is bounded by the boundary 39 between the two poles 39 a and 39 b of the tracking magnet 39.
By being adsorbed so as to face c, the lens holder 33 causes the first objective lens 26a to be inserted into the optical path at the first midpoint position or the second objective lens 26b.
Is moved to a second midpoint position where it is inserted in the optical path. Note that, in FIG. 7, the lens holder 33 is shown to be located between the first midpoint position and the second midpoint position.

As a result, when the objective lens 26a is inserted into the optical path, the iron piece 41 faces the boundary 39c between the two magnetic poles 39a and 39b of the facing tracking magnet 39, as shown in FIG. As a result, the lens holder 33 is at the first midpoint position, and the magnetic flux flows as indicated by the arrow, so that the lens holder 33 is held at the first midpoint position. Here, when a driving current is applied to the tracking coil 35, the lens holder 33 is swung around the support shaft 32 with the first midpoint position as a reference, so that the objective lens 26a moves. The tracking is performed by moving in the tracking direction which is substantially the tangential direction.

When a reverse current is applied to the tracking coil 35, the magnetic field generated in the tracking coil 35 repels the magnetic pole 39a of the tracking magnet 39, as shown in FIG. The tracking coil 35 moves so as to face the magnetic pole 39b. As a result, the iron piece 40 on the opposite side faces the boundary 39c between the magnetic poles 39a and 39b of the tracking magnet 39, the lens holder 33 is moved to the second midpoint position, and the objective lens 26b is in the optical path. Will be inserted into.

Further, as shown in FIG. 11, the semiconductor laser device 21 has an output power suitable for the optical detector depending on the type of the optical disc and the type of the optical disc to be reproduced. Is adjusted by the laser light adjusting circuit 42. In FIG. 11, a laser light adjusting circuit 42 includes a laser control power source 43 for applying a drive voltage to the semiconductor laser element 21 and a monitor phototransistor 44 for receiving light from the semiconductor laser element 21 adjacent to the semiconductor laser element 21. The laser control power supply 43 appropriately adjusts the drive current supplied to the semiconductor laser element 21 based on the detection signal from the phototransistor 44, so that the laser light is emitted from the semiconductor laser element 21. The emitted light amount of the generated light beam is appropriately adjusted.

Further, the connection line to the phototransistor 44 is grounded through the changeover switch 45 and the two variable resistors 46 and 47. Of the two variable resistors 46 and 47, the variable resistor 46 is adjusted so as to give an optimum amount of emitted light to a high density optical disc which is, for example, the second type of optical disc. The variable resistor 47 is adjusted so as to give an optimum amount of emitted light to the first type optical disc, for example. This allows the changeover switch 4 to be selected depending on the format of the optical disc to be reproduced.
The semiconductor laser device 21 is switched by switching 5
Emits a light emission amount optimum for the format of the optical disc to be reproduced.

The photodetector 27 is divided into three by the grating 22 as shown on the left side of FIG.
Of the main beam, it is composed of a first light receiving portion 27a that receives the central main beam and second and third light receiving portions 27b and 27c that receive the side beam. The first light receiving portion 27a is further divided into four light receiving portions A, B, C, D which are vertically and horizontally divided into four. In addition, the second and third light receiving portions 27b and 27c are the light receiving portions 27b and 27c.
The light receiving portions E, F, G, and H are divided into two in the direction in which a and 27c are arranged.

Here, the first light receiving portion 27a having the four light receiving portions A, B, C and D divided into four vertically and horizontally is used to perform focusing servo by the astigmatism method, as described later. The necessary light receiving portions are arranged in a divided manner, and at the same time, a tracking error signal can be generated by the phase difference method described later for the second type disk. In order to do so, the raising mirror 24 of FIGS. 3 and 4 is selected and arranged so that the inclination direction thereof forms an angle of 45 degrees with the track direction (tangential direction) of the optical disk 11. ing. As a result, the optical axis that enters the rising mirror 24 from the beam splitter 23 and the returning optical axis that the return light from the optical disk enters the beam splitter 23 after being reflected by the rising mirror 24 are indicated by L1 in FIG. 45 to track direction (tangential direction)
It is inclined at a certain angle and is away from the spindle motor. For this reason, the first light receiving portion 27a of the photodetector described later can perform both focus error detection by the astigmatism method and tracking error detection by the phase comparison method.

Here, each of the light receiving portions A, B, C, D, E,
The detection signals from F, G, and H are converted into current and voltage by operational amplifiers, respectively, and then the error correction circuit 16 described above generates a tracking error signal and a focusing error signal.
9 is input. The tracking error signal and the focusing error signal are generated by the error correction circuit 16 according to the format of the optical disc.
This is performed as follows.

That is, in the case of the optical disc of the first type, as shown in FIG. 12, the focusing error signal F
CS is each light receiving portion A, B, C, D of the first light receiving portion 27a.
From the detection signals Sa, Sb, Sc, Sd from, by the adders 49, 50 and the subtractor 51, based on the so-called astigmatism method,

[Equation 1] Is calculated by In addition, the tracking error signal TR
K is the adder 52, based on the so-called three-spot method, from the detection signals Se, Sf, Sg, Sh from the respective light receiving parts E, F and the third light receiving parts G, H of the second light receiving part 27b. 53 and subtractor 54

[Equation 2] Is calculated by

On the other hand, in the case of the second type of high-density optical disc, for example, as shown in FIG. 13, the focusing error signal FCS is the same as in the case of the first type of the optical disc. Each light receiving portion A of the light receiving portion 27a of
Based on the so-called astigmatism method from the detection signals Sa, Sb, Sc, Sd from B, C, D, by the adders 49, 50 and the subtractor 51,

It is calculated by Further, since the tracking error signal TRK of the second type of optical disc cannot be obtained by the so-called three-spot method as in the case of the first type of optical disc, each of the light receiving units A of the first light receiving unit 27a,
From the detection signals Sa, Sb, Sc, Sd from B, C, D, the phase comparison circuit 55 outputs the output signal (Sa + Sc) of the adder 49 and the output signal (Sb + Sd) of the adder 50.
Is obtained by phase comparison (phase comparison method).

FIG. 14 is a diagram for explaining the phase comparison method as the tracking error detection method. FIG.
The central column in (a) shows a state in which the spot S1 of the light beam (main beam) is on-track in the pit P on the signal recording surface of the optical disc. The left column on both sides of this central column shows the state in which the spot S1 is detracked from the track to the left in the figure. The pits P in each column show a state in which they are gradually moving from the bottom to the top of the column relative to the spot S1, and the spot S on the signal recording surface is shown.
In the spots S2 shown on the 1st side, the darkened portions of the spots formed on the divided light receiving portions in FIG. 14B are shown in the shaded state.

In the left column of FIG. 14A, the spot S1 is detracked to the left of the pit P. At this time, in the spot S2, the dark portion first appears in the lower left,
The output signal (S) of the adder 50 corresponding to the divided light receiving units B and D
The output signal of (b + Sd) decreases. Then, the output signal (Sa + Sc) also drops. That is, since the output signal of (Sb + Sd) changes before the output signal of (Sa + Sc), the output signal of (Sb + Sd) is (Sa + S).
The phase advances from the output signal of c). On the contrary, in FIG.
In the right column of (a), the spot S1 is detracked to the right of the pit P. In this case, contrary to the above, (Sa +
The output signal of (Sc) leads the phase of the output signal of (Sb + Sd).

The phase comparison circuit 55 shown in FIG.
Output signal (Sa + Sc) and the output signal of the adder 50 (S
The tracking error signal is generated by phase comparison of (b + Sd) based on the above principle. The phase comparison circuit 55 is, for example, the two signals (Sa +
For Sc) and (Sb + Sd), the rising and falling edges of these sum signals are detected, the difference signals are sample-held at the rising and falling timings, and the difference between the sample-hold signals is taken. ,
Although the tracking error signal is used, the present invention is not limited to this, and it is also possible to use a phase comparison circuit of any other configuration. For example, when the level of the detection signal becomes low,
Since large noise is likely to be mixed in this defective portion, two signals (Sa + Sc) and (S
A bias signal of the same phase may be added to (b + Sd).

Here, the switching of the three-spot method and the phase comparison method of the tracking error signal is performed by discriminating the format of the optical disc to be reproduced. FIG. 15 shows that, based on the discrimination of the optical disc format,
It is a block diagram which shows the structure for obtaining different tracking error signals. In the figure, the objective lens 26 is finely moved in the tracking direction by a biaxial actuator 30. The biaxial actuator 30 is driven by the tracking servo circuit 64. The tracking servo circuit 64 constitutes a part of the servo circuit 19 shown in FIG. 1 and includes a tracking error signal calculation circuit 62 and an objective lens drive circuit 61. The tracking error signal calculation circuit 62 has a tracking error signal calculation section for the three-spot method and the phase comparison method shown in FIGS. 12 and 13, respectively. Then, the tracking error signal calculation circuit 62 selects the calculation unit of the three-spot method or the phase comparison method according to the instruction of the disc discriminating unit 63 as the selection unit, and calculates the tracking error signal in each calculation unit. Then, it is given to the objective lens drive unit 61.
The disc discriminating unit 63 discriminates whether the type of the optical disc to be reproduced is the first type optical disc or the second type optical disc, and calculates the tracking error signal corresponding to each type of disc. To the arithmetic circuit 62 for the tracking error signal.

Specifically, the disc discriminating unit 63 determines, for example, from the photodetector, the ID of the optical disc set at that time.
After reading the result, the first type optical disc or the second type
It is determined whether the type of optical disk is. Alternatively, the disc discriminating unit 63 discriminates the type of the optical disc by using the photodetector 27 or another photodetector to obtain the detection result based on the difference in the reflected light amount of the light due to the difference in the substrate thickness of the set optical disc. To do. Further, the photodetector 27 measures the number of tracks for a fixed distance in the radial direction of the optical disc set at that time, and outputs the measurement result to the disc discriminating unit 63. Based on this, the disc discriminating unit 63 can discriminate the optical disc by various methods such as discriminating the type of the optical disc and outputting the discrimination result to the arithmetic circuit 62 for the tracking error signal. Further, without automatically discriminating the type of the optical disc set at that time, the user selects an operator as the selection unit 62 and calculates information on the type of the optical disc set by the user at that time to calculate the tracking error signal. It may be provided to the circuit 62.

The optical disk device 10 incorporating the optical pickup according to the present embodiment is configured as described above and operates as follows. When reproducing a high-density optical disc, which is a second type of optical disc, first, the lens holder 33 is at the first midpoint position as shown in FIG. 2, and the objective lens 26a is in the optical path. The iron piece 41, which is inserted into the lens holder 33 and is attached to the lens holder 33, faces the boundary 39c of the tracking magnet 39. Here, the spindle motor 12 of the optical disc device 10 is rotated, so that the optical disc 11 is rotationally driven. And the optical pickup 2
0 is moved in the radial direction of the optical disk 11 along the guide 28, so that the optical axis of the objective lens 26a is
Access is performed by moving the optical disk 11 to a desired track position.

In this state, in the optical pickup 20, the light beam from the semiconductor laser element 21 is split into three light beams by the grating 22 and then reflected by the reflecting surface 23a of the beam splitter 23 to stand up. It is reflected toward the optical disk 11 by the raising mirror 24. Furthermore, the light beam is converted into parallel light by the collimator lens 25, and passes through the objective lens 26a to the optical disk 11.
An image is formed on the signal recording surface of. At this time, the objective lens 26a
Thus, the numerical aperture is appropriately set to, for example, NA = 0.6 corresponding to the high density optical disc, and the light beam is correctly imaged on the signal recording surface of the optical disc 11. The return light from the optical disk 11 is again the objective lens 26a, the collimator lens 25, and the raising mirror 24.
Through the beam splitter 23, and the photodetector 2
Image at 7. As a result, the recording signal of the optical disc 11 is reproduced based on the detection signal of the photodetector 27.

At this time, from the detection signal from the photodetector 27, the signal demodulator 15 detects the tracking error signal by the phase comparison method as shown in FIG. 13 and the focusing error signal by the astigmatism method. To be detected. Then, the optical disc drive controller 14
The servo circuit 19 causes the focusing coil 34 to
Also, the drive current to the tracking coil 35 is servo-controlled. Accordingly, by controlling the drive current of the focusing coil 35, the magnetic field generated in the focusing coil 35 acts on the magnetic fields of the focusing magnet 37 and the focusing coil 36, so that the lens holder 33 is attached to the support shaft 32. Along with that, the movement is adjusted in the focusing direction to perform focusing. Also,
The magnetic field generated in the tracking coil 35 acts on the magnetic field generated by the tracking magnet 39 and the tracking yoke 38, whereby the lens holder 33
However, the oscillation is adjusted around the support shaft 32 with the first midpoint position as a reference, and the objective lens 26a is moved and adjusted in the tracking direction which is substantially the tangential direction to perform the tracking servo.

Next, for example, when reproducing the first type of optical disk (eg, CD), a reverse current is applied to the tracking coil 35 so that the tracking coil 35 is mounted on the lens holder 33 as described above. The other iron piece 4
The lens holder 33 is rotated around the support shaft 32 and moved to the second midpoint position so that 0 faces the boundary 39c of the tracking coil 39. This allows
The objective lens 26b is inserted in the optical path.

Here, similarly, the optical disk device 10
The spindle motor 12 rotates to rotate the optical disk 11. Then, the optical pickup 20 is moved along the guide 28 in the radial direction of the optical disc 11, so that the optical axis of the objective lens 26b is moved to a desired track position of the optical disc 11, thereby performing access. Be done.

In this state, in the optical pickup 20, the light beam from the semiconductor laser element 21 is split into three light beams by the grating 22 and then reflected by the reflecting surface 23a of the beam splitter 23 to stand up. It is reflected toward the optical disk 11 by the raising mirror 24. Further, the light beam is converted into parallel light by the collimator lens 25, and passes through the objective lens 26b to the optical disk 11.
An image is formed on the signal recording surface of.

At this time, the numerical aperture is appropriately set to, for example, NA = 0.38 by the objective lens 26b corresponding to the optical disc of the first type, and the light beam is correctly reflected on the signal recording surface of the optical disc 11. It will form an image. The return light from the optical disk 11 passes through the objective lens 26b, the collimator lens 25, and the raising mirror 24 again,
The light passes through the beam splitter 23 and forms an image on the photodetector 27. Thereby, based on the detection signal of the photodetector 27,
The recorded signal on the optical disk 11 is reproduced.

At this time, from the detection signal from the photodetector 27, the signal demodulator 15 detects the tracking error signal by the three-spot method as shown in FIG. 12, and the focusing error signal by the astigmatism method. Is detected. Then, the optical disc drive controller 1
4, the servo circuit 19 causes the focusing coil 3
4 and the drive current to the tracking coil 35 is servo-controlled. Accordingly, by controlling the drive current of the focusing coil 35, the magnetic field generated in the focusing coil 35 acts on the magnetic fields of the focusing magnet 37 and the focusing coil 36, so that the lens holder 33 is attached to the support shaft 32. Along with that, the movement is adjusted in the focusing direction to perform focusing. Further, the magnetic field generated in the tracking coil 35 causes the tracking magnet 39 and the tracking yoke 3 to move.
By interacting with the magnetic field from the lens holder 3,
3 is oscillated and adjusted around the support shaft 32 with the second midpoint position as a reference, and the objective lens 26a is moved and adjusted in the tracking direction which is substantially a tangential direction to perform tracking.

As described above, in the above-described embodiment, the collimator lens 25 of the optical pickup 20 is provided between the rising mirror 24 and the objective lens 26, not between the semiconductor laser element 21 which is the light source and the rising mirror 24. It is arranged in between. As a result, the optical path length from the light source to the raising mirror is relatively short, so that the optical pickup 2
0, and the entire optical disk device is compact.

The optical disk device 1 according to the above embodiment.
0 and the optical pickup 20, the magnetic pole 39a of the tracking magnet 39 is the S pole and the magnetic pole 39b is the N pole.
Although it is set to the pole, it may have the opposite polarity. In this case, if the direction of the current flowing through the tracking coil 35 is reversed, the lens holder 33 similarly performs tracking at the first midpoint position and the second midpoint position. Further, in the optical disc device 10 and the optical pickup 20 according to the above-described embodiment, the lens holder 33 holds the two objective lenses 26a and 26b, but the present invention is not limited to this, and three or more objective lenses are held. Then, each objective lens may be selectively inserted into the optical path by the interaction between the tracking coil 35 and the tracking magnet 39,
Alternatively, it is obvious that only one objective lens may be held as usual.

[0057]

As described above, according to the present invention, since the collimator lens is arranged between the raising mirror and the objective lens, the horizontal optical path from the light source to the raising mirror is short. An optical pickup and an optical disk device configured as described above are provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of an embodiment of an optical disk device incorporating an optical pickup according to the present invention.

FIG. 2 is a plan view showing a configuration of an optical pickup in the optical disc device of FIG.

FIG. 3 is a vertical cross-sectional view taken along the optical path from the semiconductor laser element to the raising mirror, the collimator lens, and the objective lens in the optical pickup of FIG.

4 is a sectional view of a biaxial actuator in the optical pickup of FIG.

5 is a plan view showing an optical system in the optical pickup of FIG.

6 is a side view showing an optical system in the optical pickup of FIG.

7 is a perspective view of a biaxial actuator in the optical pickup of FIG.

FIG. 8 is an exploded perspective view of the biaxial actuator of FIG.

9 is a schematic plan view showing a magnetic circuit at a first midpoint position of a lens holder in the biaxial actuator of FIG.

10 is a schematic plan view showing a state when the lens holder in the biaxial actuator of FIG. 7 is moved from a first midpoint position to a second midpoint position.

11 is a circuit diagram showing a configuration of a laser light adjusting device for a semiconductor laser element in the optical pickup of FIG.

12 is a circuit diagram showing a configuration example of a tracking error detection circuit in the case of reproducing a first type optical disc in the optical pickup of FIG.

13 is a circuit diagram showing a configuration example of a tracking error detection circuit in the case of reproducing a high density optical disc in the optical pickup of FIG.

FIG. 14 is a diagram for explaining the principle of detecting a tracking error of the optical pickup of the present embodiment.

FIG. 15 is a block diagram showing a configuration for obtaining different tracking error signals based on the determination of the type of optical disc in the optical pickup of the present embodiment.

[Brief description of reference numerals]

10 ... Optical disk device, 11 ... Optical disk, 1
2 spindle motor 13 optical pickup 14 optical disk drive controller 15
... signal demodulator, 16 ... error correction circuit, 17 ... interface, 18 ... head access control unit, 20 ... optical pickup, 21 ...
・ Semiconductor laser device, 22 ... Grating, 23
... Beam splitter, 24 ... Stand-up mirror, 2
5 ... Collimator lens, 26, 26a, 26b ...
-Objective lens, 27 ... Photodetector, 28 ... Guide, 29 ... Optical base, 30 ... Biaxial actuator, 31 ... Biaxial base, 32 ... Support shaft, 33
... Lens holder, 34 ... Focusing coil, 35 ... Tracking coil, 36 ... Focusing yoke, 37 ... Focusing magnet,
38 ... Tracking yoke, 39 ... Tracking magnet, 39a, 39b ... Magnetic pole, 40,
41 ... Iron piece, 42 ... Laser light adjusting device, 43 ...
..Laser control device, 44 ... Monitor light receiving element, 45 ... Changeover switch, 46, 47 ... Variable resistance, 48 ... Operational amplifier, 49, 50, 52, 5
3 ... Adder, 51, 54 ... Subtractor, 55 ...
Phase comparison circuit

Claims (3)

[Claims] 1. An objective lens for irradiating a light beam emitted from a light source and reflected by an optical path bending mirror to focus on a signal recording surface of an optical disc, and an objective lens disposed between the optical path bending mirror and the objective lens. A collimator lens, a light separating unit for separating a light beam emitted from the light source onto the optical disc and a return light beam reflected on the signal recording surface of the optical disc, and receiving the return light beam from the signal recording surface of the optical disc. An optical pickup comprising: a photodetector having a light receiving section for 2. The optical pickup according to claim 1, wherein a side edge portion of the collimator lens is cut out in parallel with a direction in which the objective lens moves in the tracking direction. 3. A light beam emitted from a light source is reflected toward an optical disc by an optical path bending mirror,
A means for radiating a spot onto the signal recording surface of the optical disc through the objective lens by converting it into parallel light by the collimator lens, and a light detecting means having a light receiving portion for receiving the returning light beam from the signal recording surface of the optical disc. An objective lens driving unit that can move the objective lens at least in a tracking direction; a calculation unit that obtains a tracking error signal based on a signal from a light receiving unit of the light detection unit; and based on the tracking error signal, Servo means for supplying a driving current to the objective lens driving means, and the collimator lens is provided between the optical path bending mirror and the objective lens for condensing the light beam from the light source on the signal recording surface of the optical disc. The side edge of this collimator lens is flat in the direction in which the objective lens moves in the tracking direction. Optical disc apparatus characterized by being ablated.