JPH0421934B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical disk device, and more particularly to control of a reading optical system.

BACKGROUND TECHNOLOGY AND PROBLEMS In the reading optical system of an optical disk device, focus control is performed so that the light beam emitted from a laser light source is focused on the disk by an objective lens, and its optical axis is aligned with the disk. Tracking control is performed to match the information pit rows forming the track. Then, information consisting of a pit row is read by the reflected light at a spot with 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 or the like, the light beam from the laser light source will not enter the disk perpendicularly, resulting in coma aberration occurring at the reading point of the disk and degrading the reading spot. Then, the RF level, tracking error, focus error, and especially crosstalk worsen,
In the worst case, you will not even be able to get focus. In addition, the tilt due to the warpage of the disk is
Of the circumferential direction and radial direction of the disk, the radial direction is particularly large, and it is necessary to correct the optical axis skew for this radial inclination.

As such skew correction, there has conventionally been a method of tilting the optical system according to the inclination of the disk so that the optical axis is always perpendicular to the disk. The optical system in this conventional method includes all various optical elements such as a laser light source and an objective lens, and is configured to tilt the entire optical system. However, an optical system that includes all the various optical elements is large and heavy as a whole, so the dynamic characteristics of the optical system's feeding mechanism and swinging mechanism are not good, and the wiring of harnesses for connecting various signals is difficult. There were some problems, such as being troublesome.

Therefore, the inventor of the present invention constructed an optical system by separating it into a head part mainly containing an objective lens and a fixed part mainly containing a laser light source, and reflected the light beam from the fixed part by a reflecting mirror. When performing skew correction by tilting the head according to the inclination of the disk so that the light is incident on the head, we experimented with a method in which the reflecting mirror was tilted integrally with the head. However, according to this method, due to the relationship between the angle of incidence and the angle of reflection of the reflecting mirror, the light beam is tilted twice as much as the tilt of the head, and the light beam deviates from the optical axis of the objective lens and is changed when performing skew correction. A new problem has arisen in that coma aberration at the reading point of the disk is increased.

OBJECTS OF THE INVENTION The present invention aims to provide an optical disc device that can solve the above-mentioned problems.

Summary of the Invention The present invention includes an optical block that is swingably supported on a feed block around a fulcrum placed on the optical axis, and a reflecting mirror that is rotatable around the fulcrum. A light source is provided on a fixed part so as to be reflected by the reflecting mirror and irradiated onto the optical block, and the optical block is oscillated about the fulcrum in accordance with the inclination of the disk, and the optical block is also oscillated. 1/2 of the moving angle
This optical disk device is equipped with a rocking mechanism that synchronizes the reflecting mirrors at an angle of It is possible to always align the emitted light beam with the optical axis of the objective lens. Since the head part and the fixing part can be constructed separately, it is possible to take advantage of advantages such as making the head part lighter and thinner, thereby improving the dynamic characteristics of the swinging mechanism of the feeding mechanism.

Embodiment An embodiment of an optical disk device to which the present invention is applied will be described below with reference to the drawings.

First, in FIGS. 1 to 4, the head unit 10 is composed of an objective lens 11 and various other optical elements, and is used to irradiate a disc 12 with a light beam and read information from the reflected light. The head section 10 has a two-axis mechanism that can perform tracking control and focus control by itself. The head section 10 is mounted on an optical block 13. And this optical block 13 is the optical axis
It is pivotably supported on a feed block 15 via a first fulcrum 14 disposed on the OA. Note that this first fulcrum 14 is the fulcrum in the present invention.
The feed block 15 is guided by a pair of guides 16a and 16b provided along the radial direction of the disk 12, which is the direction of arrow a in FIG.
It is movable in the direction of arrow a. Therefore, the optical block 13 is configured to be swingable relative to the feed block 15 and movable together with the feed block 15 in the direction of arrow a. The movement of the feed block 15 is performed by a feed screw 18 which is provided below the feed block 15 along the direction of arrow a and is rotated around its axis by a first motor 17.

Thus, the feed block 15 and the feed screw 18 are connected by a first connecting member 20. This first connecting member 20 is swingably supported on the feed block 15 via a second fulcrum 21, and an engaging portion 22 provided at one end 20a of the first connecting member 20 is
The optical block 13 is engaged with a third fulcrum 23 provided at an eccentric position with respect to the first fulcrum 14 . The other end 20b of the first connecting member 20 is engaged via a fourth fulcrum 25 with a nut 24, which is a half nut and is screwed onto the feed screw 18. The fourth fulcrum 25 is engaged in a pair of vertically extending grooves 24a provided in the nut 24 so as to be swingable in the vertical direction. Further, the nut 24 has a spring 26 inserted between its upper end and the other end 20b of the first connecting member 20.
It is pressed by and screwed into the feed screw 18.

Next, a worm gear 27 is formed on the protruding end 20c of the first connecting member 20, and this worm gear 27 is engaged with a worm 29 of a second motor 28 fixed to the feed block 15. A worm gear 31 of a potentiometer 30 fixed to the feed block 15 is also engaged with the worm 29.

On the other hand, a first fulcrum 14 of the optical block 13 is coaxial and extends inward, and a second connecting member 33 is rotatably supported on the first fulcrum 14. This second connecting member 33 has a reflecting mirror 34 in the center thereof, and a fifth fulcrum 35 is provided at one end 33a at an eccentric position with respect to the center of rotation. The fifth fulcrum 35 is engaged with an engaging portion 36 provided at the bent end 20d of the first connecting member 20. Note that the first and second connecting members 20 and 33 and their related parts constitute a swinging mechanism as referred to in the present invention.

Next, a fixing portion 37 is provided below the disk 12 at a position spaced apart from the feed block 15 by a predetermined distance in the lateral direction. This fixed part 37 has various optical elements including a laser light source 42. The light beam emitted from the laser light source 42 is reflected by the reflection mirror 34 of the second connecting member 33, and is reflected by the head portion 10 of the optical block 13.
It is configured to be irradiated with.

In the optical disk device of the present invention configured as described above, first, when the feed screw 18 is rotated by the first motor 17, the nut 24 screwed onto the feed screw 18 is moved. . Since the first connecting member 20 is not swung unless the second motor 28 is rotated, the other end 20
When the fourth fulcrum 25 of 0b is pressed by the nut 24, the first connecting member 20 and the feed block 15
and are moved together as one. and disk 1
2 has no inclination, the first connecting member 20 is positioned in a neutral state, so that the optical block 13 is also positioned in a neutral state, and its optical axis OA is aligned with the disk 1.
It is perpendicular to 2. Note that the neutral state of the optical block 13 is detected by a potentiometer 30.

Here, as shown by the imaginary line in Figure 2, disk 1
2 is tilted by Δθ, the optical block 13 is swung according to the tilt, and its optical axis OA is corrected to be perpendicular to the disk 12. That is, when the disk 12 is tilted, the second motor 28 is rotated, and the first connecting member 20 is swung about the second fulcrum 21 in the direction of arrow b. At this time, the third fulcrum 23, which is used for swinging motion of one end 20a of the first connecting member 20 with respect to the second fulcrum 21 and is engaged with the engaging portion 22 of the one end 20a, supports the first fulcrum 14. The center is swung in the direction of arrow e. Therefore, the optical block 13 has its optical OA tilted by Δθ and is corrected perpendicularly to the disk 12. Incidentally, the inclination of the optical block 13 is detected by a potentiometer 30, and the potentiometer 30 also serves as a stopper when the optical block 13 is oscillated.

Therefore, when the first connecting member 20 is swung, the first connecting member 20 relative to the second fulcrum 21
For swinging motion of the bent end 20d of the bent end 20d.
The second connecting member 3 engaged with the engaging portion 36 of
The fifth fulcrum 35 of No. 3 is swung about the first fulcrum 14 in the direction of arrow g. That is, the second connecting member 3
3, the optical block 13 is swung separately. As will be described in detail later, the second connecting member 33 is
It is swung at an angle of Δθ/2. Therefore, by swinging the reflection mirror 34 of the second connecting member 33 at an angle of Δθ/2, the light beam from the fixed part 37 is tilted by Δθ and is aligned with the optical axis OA of the optical block 13. Ru.

By the way, in this state, the reading point on the disk reflective surface 12a becomes P', which is shifted by Δx from the original reading point P. However, the deviation Δx of the lever is corrected by the swinging motion of the other end 20b of the first connecting member 20 with respect to the second fulcrum 21. That is, when the first connecting member 20 is swung,
This is for swinging the other end 20b of the first connecting member 20 with respect to the second fulcrum 21 in the direction of arrow d.
4 is pressed against the fourth fulcrum 25 of the other end 20b.
However, since the nut 24 is screwed onto the feed screw 18 and cannot be moved laterally, the second fulcrum 21
The swing of the fourth fulcrum 25 relative to the fourth fulcrum 25 is converted into a relative swing of the second fulcrum 21 in the direction of the arrow e with respect to the fourth fulcrum 25, as shown by the imaginary line in FIG. . And the fourth fulcrum 25 is Natsu 2
4, the second fulcrum 21 is moved in the direction of the arrow f, which is the lateral direction. Therefore, the feed block 15 is the optical block 1.
The reading point P is moved (returned) in the opposite direction to the deviation Δx when the optical block 13 is tilted, and the optical axis OA of the optical block 13 is corrected to the original reading point P.

Next, referring to FIGS. 5 and 6, conditions will be described in which the deviation of the reading point P is corrected and the reflecting mirror 34 is oscillated by Δθ/2 so that the light beam is aligned with the optical axis OA. First, in FIG. 5, the first fulcrum 14, the second fulcrum 21, the third fulcrum 23, the fourth fulcrum 25, and the fifth fulcrum 35 are set to O, O', Q, R, and S, respectively.
Let Δθ' be the swing angle of the first connecting member 20 for tilting the optical axis OA of the optical block 13 by Δθ when the disk 12 is tilted by Δθ. Assuming that Δθ is minute and the deviation Δx of the reading point P is equal to the amount of movement of the fourth fulcrum 25, then OP×Δθ=O′R×Δθ′ Since the amount of movement of the third fulcrum 23 is equal, OQ ×Δθ=O′Q×Δθ′ In order for the above two equations to hold true with arbitrary Δθ and Δθ′, OP/OQ=O′P/O′Q. In other words, if the ratio of the distance between the reading point P and the third fulcrum 23 to the first fulcrum 14 is equal to the ratio of the distance between the fourth fulcrum 25 and the third fulcrum 23 to the second fulcrum 21, then The deviation Δx of the reading point P becomes equal to the amount of movement of the fourth fulcrum 25. If the fourth fulcrum 25 is not moved as shown in FIG. 6, the movement of the fourth fulcrum 25 is converted into the movement of the second fulcrum 21, thereby moving the feed block 15. Therefore, the optical block 13 is also moved by Δx, and the deviation of the reading point P is corrected.

Next, in order to tilt the light beam reflected by the reflection mirror 34 by Δθ, from the relationship between the incident angle and the reflection angle,
All that is required is to tilt the reflecting mirror 34 by Δθ/2.

That is, in FIG. 5, since the amount of movement of the third fulcrum 23 is equal, OQ×Δθ=O′Q×Δθ′ Also, since the amount of movement of the fifth fulcrum 35 is equal, OS×Δθ/2=O′S× Δθ′ From the above two equations, O′Q/OQ=2×O′S/OS. In other words, the ratio of the distance between the second fulcrum 21 and the first fulcrum 14 to the third fulcrum 23 is twice the distance of the second fulcrum 21 to the fifth fulcrum 35 and the distance of the first fulcrum 14. If the ratio is equal to, the swing angle of the reflecting mirror 34 is set to Δθ/2 with respect to the swing angle Δθ of the optical block 13. Therefore, the light beam reflected by the reflecting mirror 34 is directed to the optical block 13.
Similarly, it is tilted by Δθ and aligned with its optical axis OA.

That is, according to the present invention, when the optical block 13 is oscillated by the oscillation of the first connecting member 20,
The deviation of the reading point P is always mechanically and automatically corrected by the first connecting member 20 moving the feed block 15. Therefore, as shown in FIG. 3, the optical block 13 is always oscillated about the reading point P as the approximate center, and when the optical axis OA is tilted according to the inclination of the disk 12 to be perpendicular to the disk 12. Misalignment of the reading point P can be prevented. Note that the approximate center means that the deviation of the reading point P is extremely small and is within a range that can be easily controlled by the tracking control and focus control of the optical system 10 itself. Since the swinging of the optical block 13 and the accompanying correction of the deviation of the reading point P are simultaneously performed by the first connecting member 20, the skew correction can be performed extremely reliably.

When the skew correction is performed as described above, the first connecting member 20 connects the second connecting member 33 provided with the reflecting mirror 34 at an angle that is half the swing angle of the optical block 13. Rock in sync. Therefore, when the optical block 13 is swung according to the inclination of the disk 12, the light beam reflected by the reflecting mirror 34 always aligns with the optical axis of the objective lens 11.
Since the optical axis OA coincides with the optical axis OA, the occurrence of comatic aberration due to the light beam deviating from the optical axis OA of the objective lens 11 is completely prevented.

Further, according to the present invention, the head portion 10 and the fixing portion 37
Since the head section 10 can be constructed separately, the dynamic characteristics of the feeding mechanism and the swinging mechanism can be improved by making the head section 10 lighter and thinner. Furthermore, it becomes extremely easy to route harnesses for connecting various signals. In addition, since the adjustment part of the laser light source 42 is located in the fixed part 37, the adjustment is extremely easy.
Various advantages can be taken advantage of by separating the fixing part 37 from the fixing part 37.

Next, regarding the detection of the inclination of the disk 12, the seventh
This will be explained based on the diagram and FIG. First, as shown in FIG. 7, within the fixed part 37, a beam of light emitted from a laser light source 42 made of, for example, a semiconductor laser passes through a prism beam splitter 43 and a collimator lens 44, and is irradiated onto a reflecting mirror 34. Note that 45 is a photodetector of the adjustment section.
The light beam reflected by the reflecting mirror 34 passes through the beam splitter 46, the 1/4 wavelength plate 47, and the objective lens 11 in this order, and is focused on the disk reflecting surface 12a as a fine spot. The reflected light beam reflected and diffracted by the disk reflective surface 12a passes through the objective lens 11, the quarter-wave plate 47, the beam splitter 46, and the convex lens 48 in order.
The light is incident on the light receiving surface of the photodetector 49. Here, when the disk 12 is tilted by Δθ in the radial direction of the arrow a, the reflected light flux from the disk 12 side to the beam splitter 46 changes the focal length of the objective lens 11 and the convex lens 48 to f ₁ , If it is f ₂ , then there is a lateral displacement of 2·Δθ·f ₁ with respect to the optical axis OA. The reflected light beam projected onto the light receiving surface of the photodetector 49 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·Δθ·f ₁ s: the optical path length between the convex lens 48 and the light receiving surface of the photodetector 49.

The light-receiving surface of the photodetector 49 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 Sa = S _A
By obtaining −S _B , depending on the output difference Sa,
By rotating the second motor 28 in forward and reverse directions, the optical block 13 can be oscillated so that its optical axis OA can always be tilted perpendicularly to the disk 12.

Note that the first connecting member 20 and the second connecting member 33, which constitute the swinging member in the present invention,
is not limited to the shape shown in the example,
Various modifications are possible.

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

Effects of the Invention The present invention allows an optical block to be supported swingably relative to a feed block around a fulcrum placed on the optical axis, and is provided with a reflecting mirror that is rotatable around the fulcrum. A light source is provided on a fixed part so as to be reflected by the reflecting mirror and irradiated onto the optical block, and the optical block is oscillated about the fulcrum in accordance with the inclination of the disk, and the optical block is also oscillated. 1/2 of the moving angle
Since this is an optical disk device equipped with a swinging mechanism that synchronously swings the reflecting mirrors at an angle of When correcting so that the light beam is reflected by the reflecting mirror, the light beam reflected by the reflecting mirror can always be made to coincide with the optical axis of the objective lens. Therefore, the occurrence of comatic aberration due to deviation of the light beam from the optical axis of the objective lens is completely prevented. Moreover, in this case, as shown in the embodiment, since the optical block can always be oscillated with the reading point as the approximate center, it is possible to prevent the reading point from shifting as much as possible, and the light beam is always directed to the original reading point. Can be irradiated accurately.

Furthermore, since skew correction can be performed in an optical system in which the head section and the fixed section are separated, the dynamic characteristics of the feeding mechanism and the swinging mechanism are improved by making the head section lighter and thinner. Furthermore, it is possible to take full advantage of the various advantages of separating the head section and the fixed section, such as the ease of routing harnesses for connecting various signals.

[Brief explanation of drawings]

The drawings show an embodiment of an optical disk device to which the present invention is applied, in which Fig. 1 is an exploded perspective view of the main parts, and Fig. 2 is a front view showing a state in which the optical block is swung. , Fig. 3 is a front view showing the state in which the feed block has been moved, and Fig. 4 is the - of Fig. 2.
5 and 6 are cross-sectional views taken along lines, and are explanatory diagrams for explaining the conditions under which the deviation of the reading point is corrected and the light beam reflected by the reflecting mirror is aligned with the optical axis, and FIG. FIG. 8 is 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. Also, in the symbols used in the drawings, 10...
Head part, 11... Objective lens, 12... Disk, 13... Optical block, 14... First fulcrum, 15... Feed block, 17... First motor, 18... Feed screw, 20... ...first connecting member, 21...second fulcrum, 23...third fulcrum,
24...Natsuto, 25...Fourth fulcrum, 28...
Second motor, 33... Second connection member, 34...
. . . reflecting mirror, 35 . . . fifth fulcrum, 37 . . . fixed portion, 42 . . . laser light source.

Claims (1)

[Claims] 1. An optical block is swingably supported with respect to a feed block around a fulcrum placed on the optical axis, a reflecting mirror is provided that is rotatable around the fulcrum, and a light source of the optical block is provided on a fixed part. The optical block is configured to be reflected by the reflective mirror and irradiated onto the optical block, and the optical block is swung around the fulcrum in accordance with the inclination of the disk, and the oscillation angle is 1/2 of the oscillation angle of the optical block. An optical disk device comprising a swinging mechanism for synchronously swinging the reflecting mirror at an angle of .