JPH1166603A - Optical disk drive - Google Patents

Abstract

(57) [Problem] To provide an optical disk device having good reproduction characteristics or recording / reproduction characteristics. An optical disc device includes an optical head (2) including an optical head body (3), an objective lens (4), and a tracking actuator for moving the objective lens (4), and an optical head body movement including a sled motor for moving the optical head body (3). It has a mechanism, a control means, an RF amplifier, a servo processor, a tracking driver, a thread driver, and a driver. Optical head body 3
Are a laser diode 5, a diffraction grating 50, a beam splitter 6, a collimator lens 7, a rotatable parallel plate 8 having light transmissivity, a split photodiode 9, and an inclination of the parallel plate 8. A tilt angle changing mechanism including an actuator for changing the angle.
When the inclination angle of the parallel plate 8 is changed, the optical axis 52 moves in parallel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk apparatus for reproducing or recording / reproducing an optical disk.

[0002]

2. Description of the Related Art CD (Compact Disc), CD-R
An optical disk device for reproducing an optical disk such as an OM,
2. Description of the Related Art An optical disk device that records and reproduces an optical disk having a pregroove (wobble) such as a CD-R, a CD-RW, a DVD-R, and a DVD-RAM is known.

FIG. 8 is a diagram (side view) schematically showing an optical head of a conventional optical disk device.

An optical disk device 101 shown in FIG.
An optical disc (CD-R) 19;
8 has an optical head (optical pickup) 102 that can move in the radial direction (the horizontal direction in FIG. 8). Hereinafter, the radial direction of the optical disk 19 is simply referred to as “radial direction”.

The optical head 102 includes a laser diode 1
05, beam splitter 106, collimator lens 1
07 and an optical head base (optical pickup base) 103 provided with a split photodiode 108, and the optical head main body 103 is shown so as to be movable in the radial direction and the rotational axis direction of the optical disk 19 (vertical direction in FIG. 8). And an objective lens 104 supported by a suspension spring.

In the optical disk device 101, tracking control is performed at the time of recording (writing of information) and reproducing (reading of information).
Moves in the radial direction. Also, when moving the optical head 102 to a predetermined track of the optical disc 19, the objective lens 104 moves in the radial direction.

[0007] The laser beam (light flux) 111 emitted from the laser diode 105 travels while spreading with a predetermined intensity distribution (luminance distribution) such as a Gaussian distribution during both recording and reproduction. That is, the laser beam 111 has the largest intensity (luminance) on the optical axis 112 and
The greater the distance from, the lower the strength.

In recording and reproducing, the laser diode 1 is used.
The laser light 111 emitted from the optical disc 19 passes through the beam splitter 106, is converted into a parallel light flux by the collimator lens 107, passes through the objective lens 104, and
Is condensed on the recording layer and is irradiated in the form of a spot. Further, the reflected light from the recording layer of the optical disk 19 is reflected by the beam splitter 106 via the objective lens 104 and the collimator lens 107, is bent in a right angle direction, is condensed on the light receiving surface of the divided photodiode 108, and is spot-shaped. Irradiated.

In this case, when the center of the objective lens 104 and the optical axis 112 coincide with each other, the intensity distribution of the laser beam 111 in the objective lens 104 becomes symmetric, so that the shape of the spot light on the optical disc 19 Becomes radially symmetric.

However, when the objective lens 104 moves in the radial direction, the optical axis 112 deviates from the center of the objective lens 104, and the intensity distribution of the laser beam 111 in the objective lens 104 becomes asymmetric in the radial direction. 1
9, the shape of the spot light becomes asymmetric in the radial direction. In other words, the spot light is blurred and enlarged when the intensity of the laser light 111 is low, thereby increasing the intensity of the laser light 111.
The recording / reproducing characteristics of No. 1 deteriorate. Specifically, the following inconveniences occur.

Since pits are formed (recorded) by irradiating the optical disk 19 with the asymmetric spot light, the pits become asymmetric in the radial direction (pit recording characteristics deteriorate). Since the pits are reproduced by irradiating the asymmetric spot light, the reproduction characteristics of the pits are also deteriorated. As described above, the recording / reproducing characteristics of the pits deteriorate, that is, the jitter of the recording / reproducing signal increases.

In this case, the influence on the recording / reproducing characteristics of the pit due to the asymmetric shape of the spot light is as follows.
A problem is also encountered when playing back in an optical disk device that plays back an optical disk such as a CD or CD-ROM.
This is particularly problematic when recording in an optical disc device that records and reproduces an optical disc having a pre-groove such as RW, DVD-R, and DVD-RAM.

The pre-groove of the optical disk 19 is
While meandering at a predetermined cycle, the pregroove includes time information (ATIP: Absolute Time In Pre-Groov).
e) is recorded. When recording on the optical disk 19, for example, during cueing for recording or during recording, the pre-groove is reproduced, that is, time information is read from the pre-groove.

However, when the objective lens 104 moves in the radial direction as described above, the shape of the spot light on the optical disk 19 becomes asymmetric in the radial direction, and the reproduction characteristics of the pregroove deteriorate. That is, the wobble jitter increases.

[0015]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical disk apparatus having good reproduction characteristics or recording / reproduction characteristics.

[0016]

This and other objects are achieved by the present invention which is defined below as (1) to (5).

(1) An optical disk device that has a rotation drive mechanism for mounting and rotating an optical disk, and an optical head having a light source and an objective lens, and reproduces, records, and reproduces the optical disk. An optical component installed on the optical path of the emitted light beam so as to be able to change the inclination angle of the light beam with respect to the optical axis, and using refraction to change the position of the optical axis of the light beam; and the inclination of the optical component. A tilt angle changing mechanism for changing an angle; and control means for controlling driving of the tilt angle changing mechanism such that an optical axis of the light beam is positioned at the center of the objective lens in conjunction with movement of the objective lens. An optical disc device characterized by the above-mentioned.

(2) a shift amount detecting means for detecting a shift amount of the optical axis of the light beam from the center of the objective lens;
The optical disc according to (1), wherein the control unit controls the inclination angle of the optical component to be changed such that the deviation amount is reduced as much as possible based on a signal from the deviation amount detection unit. apparatus.

(3) An optical disc apparatus for reproducing or recording / reproducing the optical disc, comprising: a rotation drive mechanism for mounting and rotating an optical disc; and an optical head having a light source and an objective lens. An optical component installed on the optical path of the emitted light beam so as to be able to change the inclination angle of the light beam with respect to the optical axis, and using refraction to change the position of the optical axis of the light beam; and the inclination of the optical component. An optical disk device having an inclination angle setting means for setting an angle.

(4) The optical disk device according to any one of (1) to (3), wherein the optical component is a parallel plate.

(5) The optical head has a collimator lens for converting the light beam into a parallel light beam, and the optical component is disposed between the collimator lens and the objective lens. The optical disk device according to any one of (4).

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an optical disk drive according to the present invention will be described in detail based on a preferred embodiment shown in the accompanying drawings.

FIG. 1 is a block diagram showing a main part of a circuit in an embodiment of the optical disk apparatus of the present invention, and FIG.
FIG. 3 is a block diagram showing in detail an RF amplifier and a divided photodiode of an optical head of the optical disk device shown in FIG. In FIGS. 1 and 2, some of the signal lines and control lines are omitted.

The optical disk device 1 shown in these figures is a CD-R drive device for recording and reproducing an optical disk (CD-R) 19.

A spiral pre-groove (Wobble) (not shown) is formed on the optical disc 19. The pre-groove meanders at a predetermined cycle (for example, 22.05 kHz at 1 × speed), and the pre-groove includes time information (ATIP: Absolute Time In).
Pre-Groove) is recorded.

The pregroove functions as a guide groove when forming a pit (pit recording). The pregroove is reproduced, and the rotational speed of the optical disk 19 is controlled,
It is used for specifying a recording position on the optical disk 19 and the like.

The optical disk device 1 has a turntable and a spindle motor 18 for rotating the turntable, and has a rotation drive mechanism (not shown) for mounting and rotating the optical disk 19 on the turntable.

The optical disk device 1 comprises an optical head (optical pickup) 2 which can move in the radial direction of the optical disk 19 (radial direction of the turntable) with respect to the loaded optical disk 19 (turntable), and An optical head main body moving mechanism (not shown) including a sled motor 17 for moving the head 2 in the radial direction, that is, an optical head main body (optical pickup base) described later of the optical head 2 in the radial direction; , RF amplifier 12, servo processor 13, tracking driver 14, thread driver 15, amplifier 31,
It has a driver 32 and a casing (not shown) for housing these. Hereinafter, the radial direction of the optical disk 19 is simply referred to as “radial direction”.

The control means 11 is usually constituted by a microcomputer (CPU), and includes a thread motor 17, a spindle motor 18, an optical head 2, an RF amplifier 12, a servo processor 13, an amplifier 31, etc.
Performs overall control.

FIG. 3 shows the optical head 2 of the optical disk device 1.
FIG. 2 is a diagram (side view) schematically showing

The optical head 2 shown in FIG. 1 is a three-beam type optical head. The optical head 2 includes an optical head main body (optical pickup base) 3 and an objective lens ( (A condenser lens) 4.

The objective lens 4 is mounted on a lens holder 41 having a light shielding property. This lens holder 41
Are supported by a suspension spring (not shown) provided on the optical head main body 3, and the objective lens 4 and the lens holder 41 are moved relative to the optical head main body 3 in the radial direction (the left-right direction in FIG. 3) and the optical disk 19 (turntable). 3) (in the vertical direction in FIG. 3). When the objective lens 4 deviates from its neutral position (middle point), the objective lens 4 is urged toward the neutral position by the restoring force of the suspension spring. Hereinafter, the direction of the rotation axis of the optical disk 19 will be simply referred to as “the direction of the rotation axis”.

The optical head body 3 includes a laser diode (light source) 5, a diffraction grating (GRT) 50, a beam splitter 6, a collimator lens 7, and a light-transmitting (substantially transparent) parallel flat plate. (Optical component) 8 and a split photodiode (light receiving element) 9.

The diffraction grating 50, the beam splitter 6, the collimator lens 7, and the parallel flat plate 8 are provided between the laser diode 5 and the objective lens 4, respectively.
In addition, they are installed in this order on the optical path of the laser light (light flux) 51 emitted from the laser diode 5. Therefore, the parallel plate 8 is composed of the collimator lens 7 and the objective lens 4.
Located between.

When the laser light 51 emitted from the laser diode 5 passes through the diffraction grating 50,
By 0, the laser beam is split into a main laser beam and two sub-laser beams. That is, the main laser beam and the
And the two sub-laser lights are respectively emitted. Pit formation (recording), pit reproduction, pre-groove reproduction, etc.
This is performed using the main laser beam. It should be noted that FIG.
Among the two laser beams, only the main laser beam is shown.

Here, the intensity (luminance) of each laser beam is set so that the intensity of the main laser beam is k times (k is a coefficient of 1 or more) the intensity of the sub laser beam.

When the directions of the respective laser beams are compared as a push-pull signal, the phase of one sub-laser beam is advanced by 180 ° with respect to the main laser beam, and the other sub-laser beam is advanced with respect to the main laser beam. The phase of the light is delayed by 180 ° (so that the phase of one sub-laser beam and the phase of one sub-laser beam are the same), that is, the spot light of the main laser beam is The spot light of the sub laser beam is set so as to be irradiated between the track and a track adjacent to the track when the track is illuminated upward.

In the following description, representatively,
The main laser light among the two laser lights will be described.

The laser beam 51 emitted from the laser diode 5 travels while recording (writing information) and reproducing (reading information) while spreading with a predetermined intensity distribution (luminance distribution) such as a Gaussian distribution. That is, the intensity (brightness) of the laser light 51 on the optical axis 52 is the highest, and the intensity decreases as the distance from the optical axis 52 increases.

During recording and reproduction, the laser diode 5
The laser light 51 emitted from the optical disc passes through the diffraction grating 50, passes through the half mirror surface 61 of the beam splitter 6, is converted into a parallel light beam by the collimator lens 7, passes through the parallel flat plate 8, passes through the objective lens 4, and passes through the objective lens 4. The light is condensed on the 19 recording layers and irradiated in the form of spots. The reflected light from the recording layer of the optical disk 19 is converted into a parallel light beam by the objective lens 4, passes through the parallel flat plate 8, passes through the collimator lens 7, is reflected by the half mirror surface 61 of the beam splitter 6, and is reflected at right angles (see FIG. 3 and the light is converged on the light receiving surface of the divided photodiode 9 and irradiated in the form of a spot.

As shown in FIG. 2, the divided photodiode 9
Are six light receiving parts 91, 92, 93, 94, 95 and 96, that is, light receiving parts 93 and 94 for receiving the above-mentioned main laser light reflected on the optical disk 19 and one of the above-mentioned sub-lights reflected on the optical disk 19 Light receiving units 91 and 92 for receiving the laser beam, and light receiving units 95 and 9 for receiving the other sub-laser beam reflected by the optical disk 19 described above.
6.

As described above, when compared as a push-pull signal, the phase of the spot light 97 on the light receiving surfaces of the light receiving portions 91 and 92 is different from that of the spot light 98 on the light receiving surfaces of the light receiving portions 93 and 94. The spot light 99 on the light receiving surfaces of the light receiving portions 95 and 96 advances by 180 ° and is compared with the spot light 98 on the light receiving surfaces of the light receiving portions 93 and 94.
Is delayed by 180 ° (the phase of the spot light 97 on the light receiving surfaces of the light receiving units 91 and 92 and the light receiving units 95 and 9
No. 6 has the same phase as the spot light 99 on the light receiving surface).

Each light receiving section 91 of the divided photodiode 9
From 96 to 96, currents (voltages) corresponding to the amounts of received light are output, and these currents, that is, the respective signals (detection signals) a to f are input to the RF amplifier 12, respectively. The subsequent operation of the optical disk device 1 will be described later in detail.

The parallel flat plate 8 shown in FIG. 3 has a circular shape and is rotatable about a shaft 46 extending in the radial direction.
It is installed so that the inclination angle with respect to the optical axis 52 can be changed. In this case, the parallel plate 8 has an axis 46 whose optical axis 5
2 and so as to be perpendicular to each of the radial directions.

In the present invention, the shape of the parallel plate 8 is
There is no particular limitation, other than circular, for example, oval, square,
It may be a rectangle or the like.

FIG. 6 is a side view showing the parallel plate 8.
As shown in the figure, when the perpendicular 83 of the parallel plate 8 is parallel to the optical axis 52, the position of the optical axis 52 does not change, but as shown in FIG. When tilted with respect to 52, for example, when the laser beam 51 travels from the bottom to the top in FIG. 6, the optical axis 52 is refracted in a predetermined direction when entering from the surface 81. When exiting from 82, it is refracted in the opposite direction. Thereby, the optical axis 5
2, the optical axis 52 is parallel to the distance L
Moving. In other words, the optical path of the laser beam 51 moves parallel L while maintaining its intensity distribution. This distance L changes according to the inclination angle of the parallel plate 8 with respect to the optical axis 52, that is, the angle (incident angle i) between the perpendicular 83 of the parallel plate 8 and the optical axis 52.

The same applies to the case where the laser beam 51 travels from top to bottom in FIG. That is, the optical axis when the laser light 51 travels from bottom to top in FIG. 6 matches the optical axis when the laser light 51 travels from top to bottom in FIG.

Here, assuming that the thickness of the parallel plate 8 is D, the refractive index of the parallel plate 8 is n, the incident angle is i, and the refraction angle is r, the following equation (1) is satisfied, and the optical axis 52 is The moved distance L is represented by the following equation (2).

N · sin r = sin i (1)

L = D (sin i-cos i · tan r) (2)

As a constituent material of the parallel plate 8, for example,
Various glasses, various resins, and the like are included.

In the optical disk device 1, the parallel plate 8 is located between the collimator lens 7 and the objective lens 4, and the parallel light beam enters the parallel plate 8.
Occurrence of aberration can be prevented.

The optical head body 3 has a tilt angle changing mechanism (not shown) provided with an actuator 33 for rotating the parallel plate 8 (changing the tilt angle of the parallel plate 8 with respect to the optical axis 52). I have.

The optical head 2 includes an optical head main body 3.
In contrast, a focusing actuator (not shown) for moving the objective lens 4 in the rotation axis direction and a tracking actuator 16 for moving the objective lens 4 in the radial direction with respect to the optical head body 3 are provided.

The displacement of the optical axis 52 of the laser beam 51 in the radial direction from the center of the objective lens 4 due to the radial movement of the objective lens 4 by the split photodiode 9 and the RF amplifier 12 described above. (A size and a direction thereof) are configured.

Next, the operation of the optical disk device 1 will be described. The optical head 2 emits and receives light to and from the recording layer of the optical disc 19 while performing tracking control and focus control on a predetermined track, thereby recording and reproducing the optical disc 19. Hereinafter, typically, the tracking control will be described.

As shown in FIGS. 1 and 2, the signals a to f output from the divided photodiodes 9 of the optical head 2 are shown.
Are input to the RF amplifier 12, respectively.

The RF amplifier 12 generates a push-pull signal PP and a tracking error signal TE based on these signals a to f.

The push-pull signal PP corresponds to the optical axis 52 of the laser beam 51 in the radial direction from the center of the objective lens 4.
Of the displacement and its direction (hereinafter simply referred to as “optical axis 52”).
(Amount of deviation of the signal).

The tracking error signal TE
Is the objective lens 4 in the radial direction from the center of the track.
Is a signal indicating the magnitude and direction of the shift of the center of the objective lens 4 (the amount of shift of the objective lens 4 from the center of the track).

More specifically, as shown in FIG.
3 is input to the positive input terminal of the differential amplifier 121, and the signal d output from the light receiving unit 94 is input to the negative input terminal of the differential amplifier 121. Then, the difference value between the signal c and the signal d is output from the differential amplifier 121 as a push-pull signal PP. The push-pull signal PP is input to the positive input terminals of the amplifier 31, the servo processor 13, and the differential amplifier 123, respectively.

The push-pull signal PP is represented by the following equation (3).

PP = cd (3)

The signal a output from the light receiving section 91 and the signal e output from the light receiving section 95 are respectively input to the positive input terminal of the differential amplifier 122 and the signal b output from the light receiving section 92 is input. The signal f output from the light receiving unit 96 is input to the negative input terminal of the differential amplifier 122. Then, the difference value between the signals a and e and the signals b and f is multiplied by k and output from the differential amplifier 122. This signal is input to the negative input terminal of the differential amplifier 123.

The difference value between the push-pull signal PP and the signal from the differential amplifier 122 is output from the differential amplifier 123 as a tracking error signal TE. This tracking error signal TE is
Is input to

The tracking error signal TE
Is represented by the following equation (4).

TE = (cd) −k / 2 · {(a + e) − (b + f)} (4)

The servo processor 7 generates a tracking servo signal by inverting the phase of the tracking error signal TE. This tracking servo signal is output from the tracking drive terminal 21 and input to the tracking driver 14.

The tracking driver 14 drives the tracking actuator 16 based on the tracking servo signal. This tracking actuator 16
Drives the objective lens 4 toward the center of the track. That is, tracking servo is applied.

The servo processor 7 generates a thread servo signal having a voltage value proportional to the amount of deviation of the objective lens 4 from the neutral position by passing the tracking servo signal through a low-pass filter (not shown). This thread servo signal is output from the thread drive terminal 22 and input to the thread driver 15.

The sled motor 17 is driven by the sled driver 15 when the voltage of the sled servo signal reaches the starting voltage value of the sled motor 17.
By driving the thread motor 17, the optical head main body 3 moves, that is, follows the objective lens 4.

When the thread motor 17 is driven based on the thread servo signal, the degree of amplification of the thread servo signal is determined by the amount of movement of the preceding objective lens 4 in the radial direction and the optical head that follows the objective lens 4. The amount of movement of the main body 3 in the radial direction is the same, and the objective lens 4 is preset so as to always be located at the neutral position.

In such tracking control, as shown in FIG. 4, when the objective lens 4 moves to the right in FIG. 4, the level (voltage value) of the push-pull signal PP becomes
The level corresponds to the shift amount x of the optical axis 52. The push-pull signal PP is amplified by the amplifier 31 and input to the driver 32. The driver 32 drives the actuator 33 based on the amplified push-pull signal PP.

By driving the actuator 33, as shown in FIG. 5, the parallel flat plate 8 rotates a predetermined amount (predetermined angle) clockwise in FIG. By changing the inclination angle of the parallel plate 8 (perpendicular line 83 of the parallel plate 8) with respect to the optical axis 52, the optical axis 52 moves (translates) toward the right side in FIG. The axis 52 coincides with the center of the objective lens 4. In other words, servo is applied so that the displacement x of the optical axis 52 approaches 0, that is, the optical axis 52 and the center of the objective lens 4 coincide.

On the contrary, the objective lens 4 is
When the parallel plate 8 moves to the middle left side, the parallel plate 8 rotates counterclockwise in FIG. 3, and the optical axis 52 moves to the left side in FIG. ,
As described above, the optical axis 52 coincides with the center of the objective lens 4.

In the optical disc apparatus 1, not only in the case of the tracking control described above, but also in the case where the optical axis 52 and the center of the objective lens 4 are deviated, as described above, The inclination angle of the parallel plate 8 with respect to the optical axis 52 is changed so as to coincide with the center of the parallel plate 8.

For example, in the optical disc apparatus 1, when the optical head 2 is moved to a predetermined track (target track) of the optical disc 19, that is, when the objective lens 4 is moved to the target track, the optical axis 52 and the center of the objective lens 4 are moved. The inclination angle of the parallel flat plate 8 with respect to the optical axis 52 is changed so that is equal to.

As described above, according to the optical disk device 1, the tracking control or the optical head 2
Move to the target track of the optical disc 19,
The optical axis 52 and the center of the objective lens 4 can be matched in conjunction with the movement of the objective lens 4.

For this reason, the laser beam 51 in the objective lens 4
Of the spot light on the optical disk 19 is symmetrical (for example, substantially circular) in the disk radial direction.
Recording / reproducing characteristics are improved.

More specifically, the pit recording / reproducing characteristics are improved, that is, EFM (Eight to Fourteen Modulatio).
n) Jitter is reduced.

Further, the reproduction characteristics of the pregroove are improved, that is, the wobble jitter is reduced.

In the optical disk device 1, since the parallel plate 8 is used as an optical component for changing the position of the optical axis 52, the occurrence of aberration can be prevented.

Next, the inclination angle setting means for setting the inclination angle of the parallel plate 8 with respect to the optical axis 52 will be described.

FIG. 7 is a perspective view showing a configuration example of the inclination angle setting means. As shown in FIG.
0 has a flat plate holder 42 on which the parallel flat plate 8 is mounted, and a base 43.

The plate holder 42 has four holes formed at equal angular intervals, and each hole has a screw 4
4 has been inserted.

The base 43 has an opening 431 and four screw holes 432 screwed with the corresponding screws 44. Further, four elastic members 45 are fixed to the upper side of the base 43 in FIG. The shaft 46 described above is fixed to a side surface of the base 43.

The base 43 is mounted on the optical head main body 3 so as to be rotatable about a shaft 46, and can control the movement of the optical axis 52 during operation in the same manner as described above.

The flat plate holder 42 is mounted on the base 43 by screwing each screw 44 into a corresponding screw hole 432.
Attached to. In this case, the holder 42 is pressed against the head of each screw 44 by the restoring force of the elastic member 45.

In the inclination angle setting means 40, the inclination angle of the parallel flat plate 8 with respect to the optical axis 52 is adjusted by adjusting the insertion amount of an arbitrary one of the four screws 44 into the screw hole 432. .

When assembling the optical disc apparatus 1, the tilt angle of the parallel plate 8 with respect to the optical axis 52 is set by the tilt angle setting means 40 so that the optical axis 52 and the center of the objective lens 4 coincide. Can be.

Next, an example of a method of setting the tilt angle of the parallel plate 8 with respect to the optical axis 52 by the tilt angle setting means 40 will be described.

At the time of assembling the optical disc apparatus 1, a signal (for example, a push-pull signal PP) indicating the amount of displacement of the optical axis 52 in the radial direction from the center of the objective lens 4 generated based on the signal from the divided photodiode 9 ) And the waveform of a signal indicating the amount of displacement of the optical axis 52 in the direction perpendicular to the radial direction (the direction of the axis 46) from the center of the objective lens 4, while each of the amounts of displacement is zero.
The inclination of the parallel plate 8 with respect to the optical axis 52 is set by adjusting the insertion amount of the predetermined screw 44 into the screw hole 432 such that

The optical disk device of the present invention is the same as the above-described CD.
-R drive device, other than this, for example, CD-R
Various optical disk devices for recording and reproducing optical disks having a pre-groove such as W, DVD-R, DVD-RAM,
The present invention can be applied to various optical disk devices for reproducing optical disks such as CDs (compact disks) and CD-ROMs.

The optical disk device of the present invention has been described based on the illustrated embodiment. However, the present invention is not limited to this, and each component may have any configuration having the same function. Can be replaced by

For example, in the above embodiment, the parallel plate 8 is used as an optical component for changing the position of the optical axis 52. In the present invention, however, the optical component uses the refraction to adjust the optical axis of the light beam. There is no particular limitation as long as the position can be changed. For example, a prism may be used. However, as described above, a parallel plate is preferable in that the occurrence of aberration can be prevented.

In this embodiment, the drive of the tilt angle changing mechanism is controlled by the closed loop control so that the optical axis 52 is positioned at the center of the objective lens 4. It may be performed by loop control. In the case of open loop control, for example, the following can be performed.

A signal (for example, a tracking servo signal) input to the tracking driver 14 is amplified by a predetermined factor and input to the driver 32 to drive the actuator 33, thereby changing the inclination angle of the parallel plate 8 with respect to the optical axis 52. I do. In this case, the amplification factor and the like are set in advance so that the distance L in which the optical axis 52 moves and the distance in which the objective lens 4 moves are the same.

In the present invention, the tilt angle of the optical component (for example, the parallel plate 8 or the prism) in any direction with respect to the optical axis may be changed by the tilt angle changing mechanism.

[0099]

As described above, according to the optical disk apparatus of the present invention, the light beam incident on the objective lens, that is, the intensity distribution (luminance distribution) of the light beam in the objective lens becomes symmetrical. Can be made symmetric (for example, substantially circular) in the radial direction of the optical disk. Therefore, the recording / reproducing characteristics of the optical disk device are improved.

If the optical axis of the light beam deviates from the center of the objective lens, for example, in the case of a one-beam type optical head,
In the push-pull signal, a DC component corresponding to the deviation is included, and when this DC component is large, in the tracking control, the objective lens may not be able to be positioned at the center of the track. According to the present invention, the optical axis of the light beam can be made coincident with the center of the objective lens, whereby the DC component is made substantially zero, that is, the offset accompanying the movement of the objective lens is improved (prevented). can do.

When the optical component is disposed between the collimator lens and the objective lens, since a parallel light beam enters the optical component, it is possible to prevent the occurrence of aberration.

In the case where an inclination angle setting means for setting the inclination angle of the optical component is provided, the initial setting is made so that the optical axis of the light beam coincides with the center of the objective lens when assembling the optical disk apparatus. It can be carried out.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main part of a circuit in an embodiment of an optical disk device of the present invention.

FIG. 2 is a block diagram showing in detail an RF amplifier and a divided photodiode of an optical head of the optical disk device shown in FIG. 1;

FIG. 3 is a diagram (side view) schematically showing an optical head of the optical disk device shown in FIG. 1;

FIG. 4 is a diagram (side view) schematically showing an optical head of the optical disk device shown in FIG. 1;

5 is a diagram (side view) schematically showing the optical head of the optical disk device shown in FIG.

FIG. 6 is a side view showing a parallel plate of the optical disk device shown in FIG. 1;

FIG. 7 is a perspective view showing a configuration example of a tilt angle setting unit in the present invention.

FIG. 8 is a diagram (side view) schematically showing an optical head of a conventional optical disk device.

[Explanation of symbols]

Reference Signs List 1 optical disk device 2 optical head (optical pickup) 3 optical head main body (optical pickup base) 4 objective lens (condensing lens) 5 laser diode (light source) 50 diffraction grating 6 beam splitter 61 half mirror surface 7 collimating lens 8 parallel flat plate 81, 82 surface 83 perpendicular line 9 split photodiode (light receiving element) 91 to 96 light receiving section 97 to 99 spot light 11 control means 12 RF amplifier 121 to 123 differential amplifier 13 servo processor 14 tracking driver 15 thread driver 16 tracking actuator Reference Signs List 17 thread motor 18 spindle motor 19 optical disk 21 tracking drive terminal 22 thread drive terminal 31 amplifier 32 driver 33 actuator 40 inclination angle setting means Reference Signs List 1 lens holder 42 flat plate holder 43 base 431 opening 432 screw hole 44 screw 45 elastic member 46 axis 51 laser beam (light flux) 52 optical axis 101 optical disk device 102 optical head (optical pickup) 103 optical head main body (optical pickup base) 104 Objective lens 105 Laser diode 106 Beam splitter 107 Collimating lens 108 Split photodiode 111 Laser beam 112 Optical axis

Claims (5)

[Claims] 1. An optical disk device for reproducing or recording / reproducing the optical disk, comprising: a rotation drive mechanism for mounting and rotating an optical disk; and an optical head having a light source and an objective lens. An optical component that is installed on the optical path of the light beam to be able to change the inclination angle of the light beam with respect to the optical axis, and changes the position of the optical axis of the light beam by using refraction; and the inclination angle of the optical component. And a control means for controlling the driving of the tilt angle changing mechanism so that the optical axis of the light beam is located at the center of the objective lens in conjunction with the movement of the objective lens. An optical disc device characterized by the above-mentioned. 2. The apparatus according to claim 1, further comprising a shift amount detecting unit configured to detect a shift amount of an optical axis of the light beam from a center of the objective lens, wherein the control unit determines the shift amount based on a signal from the shift amount detecting unit. 2. The optical disk device according to claim 1, wherein control is performed to change the inclination angle of the optical component so that the amount is reduced as much as possible. 3. An optical disc device for reproducing or recording / reproducing the optical disc, comprising: a rotation drive mechanism for mounting and rotating an optical disc; and an optical head having a light source and an objective lens. An optical component that is installed on the optical path of the light beam to be able to change the inclination angle of the light beam with respect to the optical axis, and changes the position of the optical axis of the light beam by using refraction; and the inclination angle of the optical component. An inclination angle setting means for setting an angle. 4. The optical disk device according to claim 1, wherein said optical component is a parallel flat plate. 5. The optical head according to claim 1, wherein the optical head has a collimator lens for converting the light beam into a parallel light beam, and the optical component is disposed between the collimator lens and the objective lens. An optical disk device according to any one of the above.