JP2827186B2 - Optical disk warpage detection method and optical pickup - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk warpage detecting method for detecting the optical disk warpage and an optical pickup employing the warp detecting system.

[0002]

2. Description of the Related Art FIGS. 7 and 8 show a conventional optical pickup. In FIG. 1, a laser beam emitted from a laser diode 1 is split into three light beams by a diffraction grating 2, transmitted through a beam splitter 3, converted into parallel rays by a collimator lens 4, and controlled by a biaxial actuator (not shown). Condensed by the objective lens 5 and form three light spots arranged on the signal surface of the optical disk 6 in the jitter direction (distribution direction of the disk), and the return light reflected on the signal surface of the optical disk 6 returns along the same path. The light passes through the objective lens 5 and the collimator lens 4, is reflected at right angles by the beam splitter 3, passes through the plano-concave lens 7 and the cylindrical lens 8, and irradiates the photodetector 9. The base 10 of the optical pickup having the above-described optical components is mounted on the guide rail 1 in the disk radial direction.
1 guides the disk in the radial direction.

Conventionally, a tilt sensor 12 for detecting the warp of the optical disk 6 is provided on the upper surface of the base 10. The tilt sensor 12 has a structure in which light receiving elements 14 are arranged on the left and right of the light emitting diode 13 in the disk radial direction, and light emitted from the light emitting diode 13 is reflected by the optical disk 6 and received by the light receiving elements 14 and 15, When the optical disk 6 is warped, the warpage is detected based on the difference between the outputs of the two light receiving elements 14 and 15.

That is, FIG. 10 shows a state in which the optical disk 6 has no warp. At this time, the light reflected by the optical disk 6 irradiates the two light receiving elements 14 and 15 equally, and therefore, the two light receiving elements 14 and 15 Is zero, and the disk warp signal θe is θe = EF = 0. As shown in FIG. 9, when a warp in the + θ direction occurs (a tilt in which the outer peripheral side of the disk is lowered is defined as a warp in the + θ direction), the reflected light makes the light receiving element 15 on the outer peripheral side of the disk strong and weakens the light receiving element 14 on the inner peripheral side. Irradiation, and therefore, the disk warp signal θe at this time is θe = EF <0. When the warp in the -θ direction occurs as shown in FIG. 11, the reflected light irradiates the light receiving element 15 on the disk outer peripheral side weakly and strongly irradiates the light receiving element 14 on the inner peripheral side contrary to the case of FIG. 9, Therefore, the disk warpage signal θe is θe = EF> 0. Thus, the disk warp signal θ detected by the tilt sensor 12
e is transmitted to the mechanical tilt motor of the mechanical tilt mechanism,
The mechanical chassis supporting the guide rail 11 is tilted, and the attitude of the optical pickup is controlled so that the light beam irradiating the optical disc 6 is perpendicular to the optical disc 6. In the case of a small optical disk having a diameter of 12 cm or the like, the warpage is not a particular problem. Since an error may occur in signal detection, it is necessary to control the attitude of the optical pickup by detecting the warp of the optical disk as described above.

[0005]

As described above, the conventional disk warpage detection method uses the base 10 of the optical pickup.
Since the tilt sensor 12 is provided on the upper surface of the optical pickup 6 so as to face the optical disk 6, the size of the optical pickup is increased by the amount of the tilt sensor 12, the weight is increased, and this is an obstacle to cost reduction. In addition, actual opening flat 1-181
No.124 "Tilt servo device for optical disk player"
Is a main beam and a pair of sensors on the signal recording surface of the optical disc.
Sub-beams that irradiate
To detect the warpage of the disc from the light receiving shape of the
A tilt servo device is disclosed. However,
This tilt servo device is located on the signal recording surface of the optical disc.
The resulting pair of light spots becomes the main beam light spot
The irradiation pattern is deviated in the front-back and left-right directions.
The light spot of the pair of sub-beams and the main beam
The line connecting the light spots of the
It was oblique to the radius line. For this reason,
The shape of the received sub beam is the curvature of the optical disk in the radial direction.
Not only due to the effect of
Sound, for example, even if there is no warpage of the optical disc
Regardless, the mounting posture of the optical disc is
The optical disk may be warped due to the inclination.
It is an illusion as if it were actually
Useless posture control despite no need for posture control
Results in a playback signal leak from the adjacent track
(Crosstalk)
Was something.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned conventional drawbacks, and eliminates the need to separately provide a tilt sensor for detecting the warp of an optical disk in order to control the attitude of the optical pickup. It is an object of the present invention to provide an optical disk warpage detection method and an optical pickup which can reduce the size, weight, and cost.

[0007]

According to the present invention, there is provided a method for detecting a warp of an optical disk, comprising separating a laser beam emitted from a laser light source of an optical pickup into at least two light beams of a main beam and a sub beam. The main beam and the sub beam are spotted on the optical disc .
Irradiate the signal surface of the optical disk so as to line up on the radius line extending from the center , and among the return light reflected by the optical disk of both beams, the return light of the main beam is received by the optical sensor for detecting the focusing error, and the focusing error is detected. In addition, a warp detection signal is obtained by detecting a defocus of a sub-beam on a disk signal surface generated when the optical disk is warped by a warp detection optical sensor for receiving return light of the sub-beam.

Further , in the optical disk warpage detecting method according to the present invention, the laser light emitted from the laser light source of the optical pickup is divided into a main beam and two left and right sub-beams.
Split into three light beams, and irradiates these three light beams onto the optical disk signal surface such that the light spots are arranged on a radius line extending from the center of the optical disk, and guides the return light reflected by the optical disk to an optical component that generates astigmatism The central main beam of the three return lights transmitted through the optical component is received by a four-split optical sensor for detecting a focusing error, and the two left and right sub-beams are detected by two four-split optical sensors for detecting warpage. The positive and negative defocusing of the left and right light beams on the disk signal surface, which occur when the optical disk is warped, are detected by the two 4
It is characterized by detecting the warpage of the optical disk by detecting the output of the split optical sensor by the astigmatism method.

Further , the optical pickup of the present invention comprises a diffraction grating for separating laser light emitted from a laser light source into three light beams of a main beam and two sub-beams on the left and right sides thereof, and the three light beams are converted into light beams. Means for irradiating the signal surface of the optical disk such that the spots are arranged in the radial direction of the disk, an optical component for transmitting the return light reflected by the optical disk to generate astigmatism in the transmitted light, and a main part of the three return lights A four-split optical sensor for detecting a focusing error that receives a beam, and two four-split optical sensors for detecting a warp that receive two left and right sub-beams respectively, and the right and left sub-beams generated when the optical disc is warped Wherein positive and negative defocus on the signal surface of the disk is detected from the outputs of the two quadrant optical sensors. It is intended.

[0010]

In the above arrangement, the main beam is received by the focusing error detecting optical sensor, and the focusing error is detected. When the main beam is in just focus, the defocus of the sub beam is detected. That is, if the optical disk is warped, the main beam extends from the center of the optical disk when the main beam is in just focus.
The sub-beams arranged on the radiating line defocus (the focal point deviates from the optical disk signal surface). Therefore, by detecting the defocus of the sub beam by the optical sensor for detecting the warp, the warp of the optical disk can be detected.

The second and third aspects of the present invention provide a
In this case, two sub-beams are used by being separated into two light beams, and both the detection of the focusing error by the main beam and the detection of the defocus of the sub-beam are performed by the astigmatism method.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a front view showing an internal optical system of an optical pickup 20 according to an embodiment of the present invention. A laser diode 21 as a laser light source, and a laser beam emitted from the laser diode 21 are divided into a main beam and two right and left beams. Diffraction grating 2 for separating into three light beams of sub-beam
2. A first beam splitter 23 and an objective lens 24 are sequentially provided in a linear array in a direction perpendicular to the surface of the optical disk 6. In the diffraction grating 22, three light spots A, B, and C formed on the signal surface of the optical disk 6 are arranged in a radial direction of the disk, that is, on a radial line extending from the center of the optical disk 6 (left and right directions in FIGS. 1 and 2). Laser light is divided into three. In the three-beam method as a tracking error detection method, the sub-beam for tracking error detection is slightly shifted in the radial direction of the disk, but this shift is a slight shift such that a part of the light spot is applied to the signal track. Substantially, three light spots are arranged in the tangential direction of the disk, which is significantly different from the case of the present invention. Further, a second beam splitter 25, a plano-concave lens 26, a cylindrical lens 27, and a 12-split optical sensor 28 are sequentially provided on the side of the first beam splitter 23, and tracking is performed below the second beam splitter 25. A two-division optical sensor 29 for error detection is provided. As shown in FIG. 3 and the like, the 12-split optical sensor 28 includes a 4-split optical sensor A for detecting a focusing error at the center, and two 4-split optical sensors B provided on both sides for detecting warpage.
C. A1, A2, A
3, 4-element optical sensor B consisting of four elements A4
Consists of four elements B1, B2, B3, B4,
The quadrant optical sensor C is composed of four elements C1, C2, C3 and C4. The two-divided optical sensor 29 for detecting the tracking error is composed of two elements E and F divided in the disk radial direction as shown in FIG.

In the optical pickup 20, the laser beam emitted from the laser diode 21 is split into three light beams by a diffraction grating 22, and the first beam splitter 2
3 and condensed by the objective lens 24,
Are formed on the signal surface of the optical disk 1 in the radial direction of the disk. The return light reflected by the optical disk 6 returns through the same path, passes through the objective lens 24, is reflected by the first beam splitter 23 in a right angle direction, and then enters the second beam splitter 25. The return light that has entered the second beam splitter 25 is separated into transmitted light and reflected light. The three return lights that have passed through the second beam splitter 25 pass through a plano-concave lens 26 and a cylindrical lens 27 and irradiate a 12-split optical sensor 28. In this case, as shown in FIG. 3 or FIG. 4, the main beam irradiates the central four-divided optical sensor A for detecting a focusing error, and the two left and right sub-beams are used for detecting warpage.
The four quadrant optical sensors B and C are irradiated. Of the three return lights reflected by the second beam splitter 25,
The two sub-beams are guided out of the split optical sensor 29, and only the central main beam illuminates the split optical sensor 29.

The central 4-split optical sensor A for receiving the main beam is used for detecting a focusing error by the astigmatism method. FIG. 4 shows the beam shapes of the three quadrant optical sensors A, B, and C when the optical disc 6 has no warp. FIG.
FIG. 4A shows a case where the distance is too close, and FIG. 4C shows a case where the distance is too far. As shown in FIG.
The beam shapes in the four quadrant optical sensors A, B, and C are all the same, and in the case of just focus,
If it is too close, it will be a vertically long ellipse due to astigmatism (the beam shape in FIG. 4A will be referred to as vertically long), and if it is too far, it will be a horizontally long ellipse due to astigmatism. The focusing error detection signal EE is given by FE = (A1 + A3)-(A2 + A4). The two quadrant optical sensors B and C for detecting the warp do not relate to the focusing error detection itself.

Two quadrant optical sensors B and C for receiving the left and right sub-beams are used for detecting the warpage of the optical disk. FIG. 3 shows the beam shapes of the three quadrant optical sensors A, B, and C when the optical disk 6 is warped and when the optical disk 6 is not warped, in which case the main beam is just focused. It is sufficient if the disk warpage can be detected at the time of just focus. FIG. 3B shows the case where there is no warp, FIG. 3A shows the case where the warp in the + θ direction (warp in which the disk outer peripheral side is lowered is referred to as the warp in the + θ direction), and FIG. There are cases. FIG.
When there is no warpage (b), it is exactly the same as (b) in FIG. When there is a warp in the + θ direction in FIG. 3A, the quadrant optical sensor B corresponding to the light spot 13 on the outer peripheral side of the disk has a vertically long ellipse (corresponding to the case where the optical disk is too close), and the light spot on the inner peripheral side of the disk. The quadrant optical sensor C corresponding to C has a horizontally long ellipse (corresponding to a case where the optical disk is too far away). When there is a warp in the −θ direction in FIG. 4C, the beam shapes of the two quadrant optical sensors B and C are vertically and horizontally opposite to those in the case of the warp in the + θ direction. As described above, the defocus of the left and right sub-beams when the main beam is just focused is reversed in sign and the inclination of the optical disk can be obtained from the difference in the amount of defocus. Therefore, the disk warpage signal θe is given by − (C1 + C3 + B2 + B4)...

A two-division optical sensor 29 for detecting the main beam reflected by the second beam splitter 25 is used for tracking error detection by a normal push-pull method. The tracking error detection signal TE is as follows: TE = EF.

The attitude control of the optical pickup 20 when the optical disk 6 is warped will be described with reference to FIG. 6. As described above, a subtracter is obtained from the outputs of the two quadrant optical sensors B and C of the optical pickup 20 as described above. The disk warp signal θe obtained through 34 is input to a mechanical tilt motor 36 via a phase compensation circuit 35 to drive the mechanical tilt motor 36, and the worm wheel 38 is rotated by a worm 37 fixed to its output shaft. A vertical screw 39 integral with the worm wheel 38 is rotated, and one end of a mechanical chassis 40 with which the screw 39 is screwed is raised and lowered to incline the mechanical chassis 40.
The optical pickup 20 is inclined together with the guide rail 41 fixed above the optical pickup 20. In this way, the attitude of the optical pickup 20 is controlled so that the light beam of the optical pickup 20 is perpendicularly incident on the signal surface of the optical disk 6. The mechanical mechanism shown in FIG. 6 is a conventionally known mechanism.

Although the disk warpage signal θe is obtained by using two sub-beams in the embodiment, it is also possible to obtain a disk warp signal by using only one sub-beam. For example, in FIG. 3, the following signals .theta.e 'and .theta.e' = (B1 + B3)-(B2 + B4) obtained only from the outputs of the four-divided optical sensor B can be used as the disk warpage signals.

In the present invention, the focusing error is detected using the main beam. However, the focusing error detection method itself can be performed by a method other than the astigmatism method. Also, the defocus detected by the sub-beam can be determined by a method other than the astigmatism method.

[0020]

According to the present invention, a laser beam is separated into at least two light beams of a main beam and a sub beam, a focusing error is detected by the main beam, and a defocus of the sub beam is detected at the time of just focusing. Te, since to detect the warp of the optical disk, it is not necessary to provide a separate tilt sensor, miniaturization of the optical Pikkuatsupu, lightweight, it becomes easy to realize a cost reduction, yet the main beam and sub-beams
The light spot on the radius line extending from the center of the optical disc
It irradiates the optical disk signal surface side by side.
A pair of light generated on a signal recording surface of an optical disc, for example,
The spot is before and after the main beam light spot.
Conventional equipment that adopts an irradiation pattern that deviates in the horizontal direction
Just the effect of the optical disk's radial warping
Not affected by the tangential tilt of the optical disc.
No need to actually control the attitude by tilt servo.
Despite the use of unnecessary posture control, cross
It does not invite talk and warps the optical disc
Excellent tilt control, etc.
It works.

Further, according to the present invention, a defocus is detected by an astigmatism method by separating the light into three light beams of a main beam and two sub beams on the right and left sides thereof, and receiving the two sub-beams by four-division optical sensors. I decided to
Effective miniaturization , weight reduction and cost reduction can be achieved.
It has effects such as being able to do .

[Brief description of the drawings]

FIG. 1 is a front view of an internal optical system of an optical pickup according to one embodiment of the present invention.

FIG. 2 is an explanatory diagram of a position of a light spot formed on a signal surface of an optical disk by three light beams in the optical pickup.

FIGS. 3A and 3B are diagrams for explaining a disk warpage detection method in the optical pickup; FIG. 3A shows a case of warpage in the + θ direction, FIG. 3B shows a case without warpage, and FIG.
This is the case of warping in the direction (both are at the time of just focus).

FIGS. 4A and 4B illustrate a focusing error detection method in the optical pickup. FIG. 4A is a case where the disk is too close, FIG. 4B is a case of just focus, and FIG. Is the case.

5 is a diagram illustrating a tracking error detection method of the optical pickup.

FIG. 6 is an explanatory diagram of a mechanical tilt servo mechanism for controlling the attitude of the optical pickup.

FIG. 7 is a front view showing an internal optical system of a conventional optical pickup.

FIG. 8 is a side view of the same.

FIG. 9 is a diagram for explaining a disk warpage detection method using a tilt sensor of a conventional optical pickup, and is a diagram in the case where a warp occurs in the + θ direction on the optical disk.
FIG. 4 is a diagram showing a state of reflected light from the optical disk in the tilt sensor, and FIG.

FIG. 10 is a view for explaining a disk warpage detection method using a tilt sensor of a conventional optical pickup and in a case where there is no warp in the optical disk. FIG. 10A shows the state of reflected light from the optical disk in the tilt sensor. (B) is an explanatory diagram of the light receiving state of the light receiving element.

FIG. 11 is a diagram for explaining a disk warpage detection method using a tilt sensor of a conventional optical pickup, and is a diagram in a case where a warp occurs in the -θ direction on the optical disk. FIG. (B) is an explanatory diagram of the light receiving state of the light receiving element.

[Explanation of symbols]

 Reference Signs List 6 optical disk 20 optical pickup 21 laser diode 22 diffraction grating 23 first beam splitter 24 objective lens 25 second beam splitter 28 12-split optical sensor 29 2-split optical sensor A 4-split optical sensor for detecting focusing error B, C warpage 4-split optical sensor for detection

Claims (3)

(57) [Claims] A laser beam emitted from a laser light source of an optical pickup is separated into at least two light beams of a main beam and a sub beam, and the main beam and the sub beam are separated by a radius at which a light spot extends from the center of the optical disk.
Irradiate the signal surface of the optical disk so as to line up with the line, and among the return light reflected by the optical disk of both beams, the return light of the main beam is received by the optical sensor for detecting the focusing error, and the focusing error is detected. A method for detecting a warp of an optical disk, comprising detecting a defocus of a sub-beam on a disk signal surface generated when a warp occurs by a warp detecting optical sensor for receiving return light of the sub-beam to obtain a warp detection signal. . 2. A laser beam emitted from a laser light source of an optical pickup is separated into three light beams, a main beam and two sub beams on the left and right sides thereof, and the three light beams are extended from the center of the optical disk. Irradiate the optical disk signal surface so as to line up on the radius line, guide the return light reflected from the optical disk to the optical component that generates astigmatism, and focus the central main beam among the three return lights transmitted through this optical component. The disk signal surface of the right and left light beams generated when the optical disk is warped, while receiving the two sub-beams on the left and right by the four-divided optical sensor for detection and receiving the two left and right sub-beams by the two four-divided optical sensors for warp detection, respectively. The positive and negative defocus in the optical disc is detected by the astigmatism method from the outputs of the two quadrant optical sensors for detecting the warpage, and the A method for detecting warpage of an optical disk, comprising detecting warpage. 3. A diffraction grating for separating a laser beam emitted from a laser light source into three light beams of a main beam and two sub beams on the left and right sides thereof, and a light spot extending from the center of the optical disk. Means for irradiating the signal surface of the optical disk so as to be aligned with the radial line , optical components for transmitting the return light reflected by the optical disk and generating astigmatism in the transmitted light, and receiving the central main beam of the three return lights A four-split optical sensor for detecting a focusing error and two four-split optical sensors for detecting warpage that respectively receive two left and right sub-beams, and a disc signal of left and right sub-beams generated when the optical disc is warped Positive and negative defocus in the plane
An optical pickup that detects from the output of a split optical sensor.