JPH0329779Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to an optical disk device, and particularly to control of a reading optical system.

BACKGROUND TECHNOLOGY AND PROBLEMS In the reading optical system installed in the pick-up of an optical disk device, focus control is performed so that the light beam emitted from the laser light source is focused on the disk through the objective lens, and the light beam is focused on the disk through the objective lens. Tracking control is performed so that the axis coincides with the information pit row forming the track of the disk. Then, information consisting of a pit row is read as reflected light by a spot having a finite spread determined by the wavelength of the laser light source and the numerical aperture of the objective lens. Therefore, during reading, it is necessary to always make the optical axis of the light beam from the laser light source perpendicular to the disk. However, if the disk is tilted due to warping, etc., the light beam from the laser light source will not enter the disk perpendicularly, and this will cause coma aberration at the reading point of the disk, degrading the reading spot. become. As a result, the RF level, tracking error,
Focus errors, especially crosstalk, worsen, and in the worst case, it becomes impossible to obtain focus. Incidentally, the inclination due to warpage of the disk is particularly large in the radial direction of the circumferential direction and the radial direction of the disk, and it is necessary to correct the optical axis skew for this inclination in the radial direction.

Conventionally, for such skew correction, a method has been adopted in which the optical system is tilted according to the inclination of the disk so that the optical axis is always perpendicular to the disk.
This conventional method will be explained with reference to FIG.

The pick-up reading optical system 1 is an objective lens 2.
It is composed of various optical elements, and the information is read by irradiating the disk 3 with a beam of light perpendicularly. Note that the optical system 1 has a two-axis mechanism that can perform tracking control and focus control by itself. When the disk 3 is not tilted as shown by the solid line, the optical axis OA of the optical system is perpendicularly incident on the reading point P of the reflective surface 3a of the disk 3. However, when the disk 3 is tilted by θ ₁ as shown by the imaginary line with respect to the radial direction a, the optical system 1 is rotated by θ ₁ around the rotation center O according to the inclination of the disk 3. The optical axis OA' is configured to be incident perpendicularly to the reflective surface 3a of the disk 3. However, in this state, the reading point at optical axis OA′ is
P', and Δx (=l・θ ₁ ) from the original reading point P
The position will be shifted by the amount. It is fine as long as this deviation is within the range that is possible for the tracking control and focus control of the optical system 1 itself, but it may exceed that range, especially when accessing the entire optical system 1 at high speed, and the reading point will be out of the field of view of the optical system 1. reading becomes impossible.

Various methods have been devised to solve this problem of reading point deviation. First, the distance l from the disk reflective surface 3a to the rotation center O of the optical system 1.
It is possible to reduce the deviation by shortening as much as possible, but this method is subject to various restrictions on optical elements etc.
Moreover, it is unfavorable and impractical from the viewpoint of the balance of the center of gravity of the optical system 1. Next, there is a method to use the feed mechanism of the entire optical system 1 to correct the deviation of the reading point, but this method requires correction of the optical system 1 during high-speed access unless the motor of the feed mechanism has a very large dynamic range. There is a problem that it becomes impossible to follow.
Furthermore, there is a goniometer in which the optical system 1 can be rotated using an arc-shaped guide mechanism centered on the reading point on the disk reflective surface 3a, but this device requires precision machining and is not suitable for mass production. However, it has the disadvantage of being extremely costly.

As described above, conventionally, when the optical system 1 is tilted according to the inclination of the disk 3 and the optical axis is corrected perpendicularly to the disk 3, there is a drawback that the reading point is shifted, and no countermeasures have been taken. There was an impractical problem.

Purpose of the invention The present invention provides an optical disc device that solves the above problems.

Summary of the invention The invention consists of a motor that is driven according to the inclination of the disk, a feed screw that is rotated by the motor, and a reading optical system that is rotatably provided on the pickup body and that is connected to the feed screw. A first gear that meshes with the pickup, and a second gear that is provided on the pickup main body and meshes with the feed screw are provided, and the first gear tilts the reading optical system and the second gear tilts the pickup. The main body is moved in the radial direction of the disk. This allows the optical axis of the reading optical system to always reach the correct reading point.

Embodiment FIG. 2 shows a first embodiment of the present invention.

In the figure, an optical system 10 is composed of an objective lens 11 and various other optical elements, and is configured to irradiate a disc 12 with a light beam and read information using the reflected light. This optical system 10 has a two-axis mechanism that can perform tracking control and focus control by itself. This optical system 10 is mounted on a pickup main body 13. The pickup main body 13 also includes a skew correction motor 14.
A feed gear 15 rotated by the motor 14 is further provided extending in the radial direction a. This feed gear 15 has a gear 16.
are meshed with each other, and this gear 16 is connected to the optical system 10 with a shaft 17.
It is established by The pick-up body 13 further includes a gear 18 and a gear 19 integrally connected to a shaft 20.
The gear 18 is meshed with the feed screw 15.

A feed motor 2 is mounted on the side of the pick-up main body 13.
A feed screw 22 rotated by a rotor 1 is provided extending in the radial direction a, and the gear 19 is meshed with the feed screw 22. This causes the pickup body 13 to move along the shaft 23 in the radial direction a.
It is made movable.

In the above configuration, if the disk 12 is not tilted as shown by the solid line, the optical axis OA reaches the point P on the reflective surface 12a of the disk 12, and normal reading is performed. When the disk 12 is tilted by θ ₁ as shown by the imaginary line, this tilt θ ₁ is detected by a detection device to be described later, and the motor 14 is rotated in accordance with the detection signal. This causes the gear 16 to rotate and the optical system 10 to be tilted by θ ₁ .

Now, assume that the distance between the center O of the gear 16 and the reflecting surface 12a is l, and the pitch radius of the gears 16, 18, and 19 are γ _A , γ _B , and γ _C , respectively. Further, the rotation angle of the gear 18 when the gear 16 is rotated by θ ₁ rotation by the motor 14 is assumed to be θ _B. Therefore, the rotation angle of the gear 19 is also θ _B. When the gear 19 rotates by θ _B , the pickup body 13 moves to the right in the figure by γ _C θ _B. That is, the center O of the gear 16 moves by γ _C θ _B.

Here, if we set γ _B l = γ _C γ _A , γ _A θ ₁ =
Since γ _B θ _B , lθ ₁ = lγ _B /γ _A・θ _B = γ _C γ _A θ _B / γ _A = γ _{C θ B} θ ₁ ≒0, then ltanθ ₁ = γ _C θ _BThe above By selecting each value as follows, skew control can be performed without shifting the reading point P.

FIG. 3 shows a second embodiment of the present invention.
Portions corresponding to those in FIG. 2 are given the same reference numerals.

In this embodiment, a pick-up support base 24 is provided on a shaft 25, and this support base 24 is moved in the direction a by a feed motor 21 through engagement between a feed screw 22 and a half nut 26 provided on the support base 24. , the pick-up body 13 is moved along a shaft 23 on a support stand 24. This pick-up body 1
3 is moved by rotation of the gear 19 while meshing with a rack gear 27 provided on the support base 24.

According to the above configuration, the motor 14 is driven in response to the detection signal of the inclination θ ₁ of the disk 12, so that substantially the same operation as in the case of FIG. 2 is performed, and the optical system ₁₀ is and is moved by γ _C θ _B , so that the optical axis OA' can reach the normal reading point P.

Next, an embodiment of the device for detecting the inclination of the disk 12 will be described with reference to FIG.

As shown in the figure, within the optical system 10, a light beam from a laser light source 30 made of, for example, a semiconductor laser passes through a collimator lens 31, a beam splitter 32, a 1/4 wavelength plate 33, and an objective lens 11. The light is connected to the reflective surface 12a as a minute spot. The reflected light beam reflected and diffracted by the disk reflective surface 12a is reflected by the objective lens 11, 1/
The light passes through the four-wavelength plate 33, the beam splitter 32, and the convex lens 34, and enters the light receiving surface of the photodetector 35. Here, if the disk 12 is tilted by θ ₁ in the radial direction a, the reflected light flux from the disk 12 side to the beam splitter 32 will be as follows, assuming that the focal lengths of the objective lens 11 and the convex lens 34 are f ₁ and f ₂ , respectively. It is laterally displaced by 2·θ ₁ ·f ₁ with respect to the optical axis OA. The reflected light beam projected onto the light receiving surface of the photodetector 35 is directed in the radial direction as shown in FIG.
Lateral displacement to the a′ side. The displacement distance ΔL is ΔL=f ₂ −s/f ₂ ·2·θ ₁ ·f ₁ s: the optical path length between the convex lens 34 and the light receiving surface of the photodetector 35.

The light-receiving surface of the photodetector 35 has two light-receiving areas A, which are lined up in the projected radial direction a' as shown in the figure.
It is formed from B. In order to simplify the explanation, the number and arrangement of the light receiving areas A and B limit the detection of the inclination of the disk 12 to only the radial direction a, and consideration is not given to tracking control and focus control. It has not been.
And the output difference between these light receiving areas A and B is S _a = S _A
By obtaining −S _B , depending on the output difference S _a ,
By rotating the motor 14 in forward and reverse directions, the pickup main body 13 can be rotated so that its optical axis OA can always be tilted perpendicularly to the disk 12.

Although one embodiment of the present invention has been described above, the optical disc device of the present invention includes video discs,
It can be applied to audio disks and various other information processing disks.

Effects of the invention The optical system is always substantially rotated (moved in the embodiment) with the reading point as the approximate center, and
The optical system is tilted according to the inclination of the disk and the optical axis is corrected so that it is always perpendicular to the disk, which prevents the reading point from shifting and ensures that the light beam is always directed to the correct reading point. Can be irradiated accurately. Furthermore, since the skew correction of the present invention does not depend on the feeding mechanism, it can sufficiently cope with high-speed access of the feeding mechanism.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a reading optical system of a conventional optical disk device, FIG. 2 is a side view showing a first embodiment of the present invention, and FIG. 3 is a side view showing a second embodiment. 4 and 5 are a cross-sectional view along the optical axis of the optical system and a plan view of the light-receiving surface of the photodetector, illustrating a method for detecting the inclination of the disk. In addition, in the symbols used in the drawings, 10...optical system, 12...disk, 13...pickup body, 14...skew correction motor, 15...feed screw, 16...gear, 18...gear, P ...This is a reading point.

Claims (1)

[Scope of utility model registration request] A detection means for detecting the inclination of the disk, a motor driven in accordance with a detection signal obtained from this detection means, a feed screw rotated by this motor, and a reading optical system rotatably provided on the pickup body. a first gear provided on the pickup body and meshing with the feed screw; and a second gear provided on the pickup main body and meshing with the feed screw; the first gear tilting the reading optical system; An optical disk device in which the second gear moves the pickup main body in the radial direction of the disk so that the optical axis of the reading optical system always reaches the reading point of the disk.