JP3391019B2 - Optical disc tilt detection mechanism, tilt servo mechanism, and optical disc apparatus using the same - 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 disc tilt detection method, a detection mechanism therefor, a tilt servo system, and an optical disc apparatus using the same.

[0002]

2. Description of the Related Art As an information recording medium having a large capacity, an optical disk device is becoming more important. In the optical disk device, recording and reproduction are performed by converging laser light on the recording surface of the disk by the objective lens of the optical head. At this time, the optical axis of the objective lens needs to be correctly perpendicular to the disk recording surface. The allowable value of the deviation from the vertical depends on the system, but is within several mrad, and if this is not satisfied, aberration occurs in the beam, which causes an increase in crosstalk from adjacent tracks and a decrease in signal S / N. Of the angle of the optical axis with respect to the disc recording surface, the angle component in the disc tangential direction may generally be adjusted with reference to the turntable to which the disc is fixed, and does not need to be readjusted according to the disc. However, with respect to the tilt angle, which is the component of the tilt angle in the disc radial direction, the weight of the disc itself hangs down in a bowl shape, so the tilt angle is detected and fed back for each disc so that the optical axis is always perpendicular to the disc surface. The tilt servo mechanism that changes the angle of the objective lens and the entire optical head is adopted. The element that detects the tilt angle of the disc is a tilt sensor, and is usually a light emitting diode LE.
Receives LED reflected light from the D chip and disk surface,
A two-division photodiode PD chip for differentially detecting the movement of the reflection angle is an element housed in the same can package together with a light-in / out condenser lens.

The conventional tilt sensor is provided at a position apart from the objective lens of the optical head and fixed to the head. FIG. 3 is a diagram showing the deviation of the distance between the tilt sensor on the optical head and the objective lens from the center of the disk. The optical head 50 includes an objective lens 51 and a tilt sensor 5.
When the track is moved 55 from the outermost track 53 to the innermost track 54 of the optical disc, the deviation of the objective lens 51 and the tilt sensor 52 from the center of the optical disc at the outermost track is determined by the outermost track of the tilt sensor. When the deviation from the track is represented by d, and the deviation from the innermost track of the tilt sensor on the innermost track is represented by d ′,
The amount of deviation is clearly different between the innermost circumference and the outermost circumference.

[0004]

As described above, the deviation of the irradiation position of the light from the objective lens and the tilt sensor from the center of the disc changes depending on the position of the objective lens in the radial direction of the disc. On the other hand, accurate tilt cannot be performed. As the density of disks becomes higher and the wavelength of laser light becomes shorter, the influence of disk warpage on recording characteristics is increasing more and more, and it is necessary to minimize this effect.

[0005]

A tilt detecting mechanism for an optical disc according to a first aspect of the present invention has a shaft fixed to the optical head in a gap between the optical head of the optical disc device and the optical disc. A tilt sensor for detecting the tilt angle of the optical disc is arranged at one end across the rotation axis, and the guide pin is fitted with a rotation plate having a guide pin at the other end across the rotation axis. And having a slidable guide groove, the optical head is provided with a grooved guide fixed to a carriage frame to which a guide rail for translational movement between tracks of an optical disk is attached,
The guide path of the guide groove is defined by the optical head.
Along with the translational movement in the radial position on the
When the id pin is guided in the guide groove,
The rotational displacement of the tilt sensor along the optical disk surface
At any position on the optical disk radial position of the optical head.
Where the tilt sensor tilts on the optical disk
The detection position is always in front of the objective lens of the optical head.
It is located at the same radial position as the radial position on the optical disc.
It is characterized in that it is formed as . Further, an optical disk tilt detector of the invention according to claim 2 of the present invention.
The structure is the guide groove of the invention according to claim 1.
The center line of the guide direction is the center of the objective lens of the optical head.
On the innermost track of the optical disc, and
When the tilt sensor is also located on the innermost track
, The center position of the guide pin is T1,
Set the center of the objective lens to the outermost track of the optical disc.
And the tilt sensor is also located at the outermost track.
The center position of the guide pin when it is positioned at
2. Center the objective lens of the optical head with the optical disc.
Between the innermost track and the outermost track
Positioned on the track and the tilt sensor is in the middle
Center position of the guide pin when positioned on the track
When the position is T3, an inflection connecting T1, T2 and T3
It is characterized by a smooth curve with no points. Also,
According to a third aspect of the present invention, there is provided a tilt servo mechanism for an optical disk, wherein tilt detection output of the tilt detecting mechanism according to the first or second aspect of the present invention is used to indicate a tilt displacement of a carriage frame supporting the optical disk with respect to the optical disk surface. It is characterized in that it is returned to the driving means.
An optical disk device according to a fourth aspect of the present invention includes the tilt servo mechanism according to the third aspect of the invention.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. 1A and 1B are views showing an embodiment of the configuration of a tilt detecting mechanism for an optical disc of the present invention, in which FIG. 1A is a plan view and FIG. 1B is a front view. The optical disc 100 and the optical head 1 have the positional relationship shown in FIG. The optical head 1 that performs recording and reproduction by condensing laser light on the optical disc 100 by the objective lens 3 is provided with a tilt detection mechanism. The tilt detection mechanism detects the tilt angle of the optical disc 100 at one end with the shaft fixed to the optical head being the rotation shaft 4 in the gap between the optical head 1 and the upper surface of the optical head 1. The tilt sensor 6 is attached to the rotary shaft 4
The optical head 1 is translated between tracks of the optical disc 100, with a base 5 which is a rotary plate having a guide pin 7 at the other end with the guide pin 7 interposed therebetween and a guide groove 8 into which the guide pin 7 is slidable. It is composed of a grooved guide 9 fixed to a carriage frame 11 to which a guide rail 10 for movement is attached.

The operation of this embodiment will be described. Specific positions of the trajectory along which the optical head 1 is guided and moved by the guide rail 10 are indicated by the positions 3a and 3b of the objective lens 3. When the optical head 1 is in the middle of the recording / reproducing area of the disc 100, for example, when the position of the objective lens is at 3a, it is assumed that the objective lens 3 and the tilt sensor 6 are set at the same radial position of the optical disc 100. When the optical head 1 moves and moves from 3a to 3b at the position of the objective lens, the guide pin 7 moves along the guide groove 8 provided in the guide 9 fixed to the carriage frame 11. At the same time when the guide pin 7 slides in the guide groove 8, the base 5 rotates, and the tilt sensor 6 provided with the guide pin 7 and the rotating shaft 4 interposed therebetween.
Also rotates. If the shape of the guide groove 8 is set correctly. The position of the tilt sensor 6 with respect to the optical disc surface can be set at the same radial position from the center of the objective lens 3 and the disc 100 at the radial position. Even when the optical head 1 moves from the position 3b to the position 3b at the position of the objective lens,
The distance of the tilt sensor 6 from the center of the optical disc following the guidance of the guide groove 8 can be made equal to the distance of the objective lens from the optical disc.

The amount of rotation of the tilt sensor 6 about the rotation axis 4 along with the movement of the objective lens 3 at the radial position of the optical disk 10 is determined by the curve drawn by the guide groove 8 provided in the guide 9. This curve is analytically and mechanically determined by determining the radial position of the optical disk of the objective lens 3, the distance between the objective lens 3 and the tilt sensor 6, the distance between the tilt sensor 6 and the guide pin 7 and the rotation axis 4. It can also be designed easily by using static CAD.

FIG. 2 is an example in which the guide groove 8 is formed by using mechanical CAD. Ln (n = 1, 2, 3) is the position of the objective lens, Sn is the position of the rotation axis of the base 5 having a tilt sensor at one end and guide pins at the other end, and Tn is the position of the guide pin. n = 1 indicates that the objective lens is located on the innermost track of the optical disc, n = 3 indicates that it is located on the outermost track, and n = 2 indicates that the objective lens is located between the innermost track and the outermost track. I assume that you are doing. Radius O-L centered on the center position O of the spindle of the optical disk
Write the circles 53, 54 and 56 of 1, O-L2 and O-L3.
Next, circles 63, 64, and 66 with S1, S2, and S3 as the centers and the radius to the distance to the center of the tilt sensor are written. The intersection of these two circles is the position of the tilt sensor.
The position T of the guide pin is located on the extension of the line connecting the rotation axis Sn of the rotary plate from the position of the tilt sensor at each track position.
n is determined. From the position of three points T1, T2, T3,
The radius R and the center X of the arc of the center line of the guide groove are determined. In this way, the guide groove is designed.

A mechanism for tilting the tilt detection output of the tilt sensor 6 of the tilt detecting mechanism described above to drive the entire carriage frame 11 supporting the optical head 1 is provided, and by returning to this, a feedback control system is assembled to form a tilt servo. Mechanism can be configured. As a result, the objective lens can always irradiate the disc surface with the beam in a state almost perpendicular to the disc.

Further, when the tilt servo mechanism described above is used in an optical disc device, an optical disc device which can always maintain stable recording and reproducing characteristics and can perform high density recording and reproducing is realized.

[0012]

As described above, according to the tilt detecting mechanism of the present invention in which the base for holding the tilt sensor by the guide groove is rotated, the tilt sensor is provided at an arbitrary position on the disk radial position of the optical head. Since the objective lens and the disc are always at the same radial position, it is possible to detect the same amount of warp as the focusing position of the objective lens on the disc surface.
By applying the tilt servo based on this detection amount, the objective lens can always irradiate the disk with the beam in a state almost perpendicular to the disk. Therefore, even when a high-density disc is used, there is an effect that the recording / reproducing characteristics can always be maintained stably.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, in which (A) is a plan view and (B) is a front view.

FIG. 2 is a diagram showing a designing method by drawing of the present invention.

FIG. 3 is a diagram expressing a deviation of a distance between a tilt sensor on an optical head and an objective lens from a disc center.

[Explanation of symbols]

1 optical head 3 Objective lens 4 rotation axes 5 base 6 Tilt sensor 7 Guide pin 8 guide grooves 9 Grooved guide 10 Guide rail 11 carriage frame 50 optical head 51 Objective lens 52 Tilt sensor 53 outermost track 54 Innermost track 55 moving tracks 100 optical disks

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B ^7/ 09-7/10

Claims (4)

(57) [Claims] 1. A tilt sensor for detecting a tilt angle of an optical disk at a gap between the optical head of the optical disk device and the optical disk, the axis being fixed to the optical head is a rotation axis, and the rotation axis is sandwiched between the two ends. A rotary plate having a guide pin at the other end across the rotary shaft and a guide groove into which the guide pin is fitted and slidable, and the optical head translates between tracks of an optical disk. A guide with grooves fixed to a carriage frame to which a guide rail for moving is attached is provided, and a guide locus of the guide groove is such that the optical head has the optical disc.
Along with the translational movement in the radial position on the
When the id pin is guided in the guide groove,
The rotational displacement of the tilt sensor along the optical disk surface
At any position on the optical disk radial position of the optical head.
Where the tilt sensor tilts on the optical disk
The detection position is always in front of the objective lens of the optical head.
It is located at the same radial position as the radial position on the optical disc.
Tilt detection mechanism of the optical disc, characterized in that it is formed so that. 2. The center line in the guide direction of the guide groove is the center of the objective lens of the optical head,
Located on the innermost track, and with the tilt sensor in front
When the guide pin is positioned on the innermost track,
The center position is T1, the center of the objective lens of the optical head is the
It is located on the outermost track and the tilt sensor is in front
When the guide pin is positioned on the outermost track,
The center position is T2, and the center of the objective lens of the optical head is the center of the optical disc.
A tiger in the middle between the innermost track and the outermost track
The tilt sensor and the tilt sensor is in the middle position.
Set the center position of the guide pin when it is positioned on the rack.
If T3, then there is no inflection point connecting T1, T2, and T3.
The curved line according to claim 1, wherein the curved line is a smooth curve.
Optical disc tilt detection mechanism. 3. A tilt servo mechanism for an optical disc, wherein the tilt detection output of the tilt detection mechanism according to claim 1 is returned to a means for driving a tilt displacement of a carriage frame supporting the optical disc with respect to the optical disc surface. . 4. An optical disk device comprising the tilt servo mechanism according to claim 3 .