JPS59223942A - Optical disc device - Google Patents

Abstract

PURPOSE:To prevent the deviation of a read point by making an optical block oscillatory with the read point of a disc as an approximate center to correct the optical axis of the optical block in accordance with the inclination of the disc. CONSTITUTION:If a disc 12 is inclined by DELTAtheta, an optical block 13 is oscillated in accordance with this inclination and has an optical axis OA corrected vertically to the disc 12. A connecting member 20 is oscillated in the direction of an arrow (b) with a fulcrum 21 as the center by the rotation of a motor 28 to perform this correction. In this state, the read point of the disc is deviated to a point P'. This deviation DELTAx is corrected by the oscillatory action of the other end 20b of the connecting member 20 to the fulcrum 21. That is, in this oscillation, the oscillation of a fulcrum 25 to the fulcrum 21 is converted to the oscillation of the fulcrum 21 in the direction of an arrow (e) to the fulcrum 25 relatively by the oscillatory action of the end part 20b in the direction of an arrow (d). Then, the fulcrum 21 is moved in the direction of an arrow (f), and a feeding block 15 is moved in the direction opposite to the direction of this deviation DELTAx, and thus, the optical axis OA of the optical block 13 is corrected to a correct read point P.

Description

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

Background Art and Problem Point In the reading optical system of an optical disc device, focus control is performed so that the light beam emitted from a substitute laser light source is focused on the disc by an objective lens, and its optical axis follows the track of the disc. Tracking control is performed to match the information pit string to be formed. Then, information consisting of a bit string is read by 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 vertically incident on the disk. However, if the disk is tilted due to warpage or the like, the light beam from the laser light source will not be incident on 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 deteriorate, and in the worst case, it becomes impossible to obtain focus. Furthermore, Dinuku's warping f? Of the circumferential and radial directions of the disk, the radial direction is especially large, and it is necessary to correct the skew of the optical axis for this radial inclination.

Conventionally, such skew correction has been performed by tilting the optical system according to the inclination of the disc so that the optical axis is always perpendicular to the disc.

This conventional method will be explained with reference to FIG. First, the optical system (11) is composed of an objective lens (2) and various other optical elements, and it irradiates the disk (3) with a beam of light perpendicularly to read its contour. It has a two-axis mechanism that can perform tracking control and focus control by itself.As shown in the figure, the disc (3)
When the disc (3) is not tilted, the optical axis OA of the optical system (1) is perpendicularly incident on the read imaginary P of the disc reflective surface (3a). When the optical system (1) is tilted by Δθ as shown by the line, the optical system (1) is swung by Δθ about the center of rotation O according to the tilt of the disk (3), so that the optical axis OA is aligned with the reflective surface of the disk (3). (3a
) is configured to be incident perpendicularly to the However, in this state, the reading point on the optical axis OA of the optical system (1) is P', and the distance from the original reading point P to Δx (=7・Δ
The position will be shifted by θ]. It is sufficient if this deviation is within the range that is possible for the tracking control and focus control of the optical system (11 itself), but it may exceed that range, especially when accessing the entire optical system (1) at high speed, and the reading point may be
There was a drawback that it became impossible to read because it was out of the field of view of 11.

Various methods have been devised to solve the conventional drawback of misalignment of the reading point. First, the disc reflective surface (5a
) to the center of rotation of optical system (1) should be made as short as possible to reduce the deviation, but this method is subject to various constraints on the optical elements, etc. ) is also unfavorable and impractical from the point of view of center of gravity balance. Next, there is a method to correct the deviation of the reading point by using a feed mechanism for the entire optical system (), but this method requires that the motor of the feed mechanism has a very large dynamic range during high-speed access. There is a problem that the correction cannot follow.

Furthermore, there is a goniometer in which the optical system (1) can be oscillated by an arc-shaped guide mechanism centered on the reading point on the disk reflective surface (3a), but this device requires precision machining and is now in mass production. However, it has the disadvantage of being extremely costly.

As described above, in the past, there was a problem that the problem occurred depending on the inclination of the disk (3), and that no countermeasures were taken to solve the problem.

OBJECTS OF THE INVENTION The present invention seeks to provide an optical disc device that can correct the above-mentioned drawbacks.

Summary of the Invention The present invention includes an optical block, a feed block that holds the optical block and is transported along a guide, and a feed screw driven by a first motor.

A nut screwed onto the feed screw; and a connecting member connecting the feed block and the nut; the connecting member is swingably supported on the block, the connecting member is pivotally supported on the feed block via a second fulcrum, and one end of the connecting member is provided at an eccentric position with respect to the first fulcrum. At the same time, the other end is engaged with the nut via the fourth fulcrum, and the connecting member is fixed to the feed block and moved to the second fulcrum according to the inclination l of the disk. An optical disc device comprising a second motor that swings around the center ζ,
The optical block can be oscillated approximately about the read point of the disc. Therefore, when the optical block is tilted according to the inclination of the disk and the optical axis is corrected so that it is always perpendicular to the disk, it is possible to prevent the reading point from shifting as much as possible, and always keep the original reading point. It is possible to accurately irradiate a luminous flux.

Embodiments Hereinafter, embodiments of an optical disc device to which the present invention is applied will be described based on the drawings.

First, in Figures 2 to 4, the optical system (10) is composed of an objective lens (Ql) and various other optical elements, and it irradiates a disc (121) with a light beam and reads information by the reflected light. The optical system 00) has a two-axis mechanism that can perform tracking control and focus control by itself. This optical system (10) is mounted on an optical block 03). The optical block (13) is swingably supported on the feed block 05 via a first fulcrum placed above the optical axis OA. This feeding block (19 is a pair of guides ('168') (1 (Sb) i) provided along the direction of the arrow a in FIG. 2, which is the radial direction of the disk Q2+. Therefore, the optical block (I3) is configured to be able to swing freely relative to the feed block (15) and to be movable together with the feed block 09 in the direction of arrow a.Then, the feed block (15) The movement is performed by a feed screw (181) provided below the feed block α5) along the direction of arrow a and rotated around its axis by the first motor On.

The feed block (151) and the feed screw (18) are connected by a connecting member (201). This connecting member (2o) is swingably connected to the feed block (151) via the second fulcrum (21). One end of the centrally supported part (2
The retaining portion (22) provided in optical block 0a)
The third fulcrum (2al) is provided at an eccentric position with respect to the first fulcrum (141) of the connecting member (201).The other end (20b) of the connecting member (201) The fourth fulcrum (
the fourth fulcrum (25)
is slidably engaged in a pair of vertically extending grooves (248) provided in the nut (241). It is pressed by the connecting member (spring 06 inserted between the other end (20b) of 20j) and is screwed into the feed screw (181).

Next, a worm gear (
2η is formed, and this worm gear (27) is connected to a second motor (28) fixed to the feed block (15).
The worm (29) is engaged with the worm (29). Also, this worm (29) has a worm gear 01) of a potentiometer bolt 00 fixed to the feed block (151).
is also engaged.

In the optical disc device of the present invention configured as described above, first, when the feed screw (+81) is rotated by the first motor ON, the l-(24+) screwed into the feed screw (181) is rotated. The connecting member (20
) will not be swung unless the second motor (28) is rotated, so the fourth fulcrum (
25) is pressed against 24+, the connecting member (201) and the feed block α(5) are moved as one.If the disc α2 is not tilted,
By positioning the connecting member (20) in a neutral state, the optical block [131] is also located in a neutral state, and its optical axis OA is made perpendicular to the disk (121).The neutral state of the optical block [131] is Potentiometer coming volume (10
1 has been detected.

Here, as shown by the imaginary line in FIG. 2, disk 02+ is Δ
When θ is tilted, the optical block (1) is swung according to the tilt, and its optical axis OA is corrected to be perpendicular to the disk O2.In other words, when the disk Q2+ is tilted, the second motor ( The connecting member - is rotated, and the connecting member - is swung in the direction indicated by the arrow around the second supporting point (2
) for rocking motion, and the engaging portion (221
The fifth fulcrum (J31) that is engaged with the optical block (J31) is swung in the direction of arrow C around the first fulcrum
1m, its optical axis OA is tilted Δθ, and the academic block (1
It also serves as a stopper when 31 is swung.

By the way, in this state, the reading point on the disc reflective surface (12B) becomes P', which is shifted by ΔX from the original reading point P. However, the deviation ΔX of the lever is caused by the second fulcrum (21
) is corrected by the swinging action of the other end (20b) of the connecting member (a). In other words, when the connecting member @) is swung, the connecting member (
For swinging the other end (20b) of 201 in the direction of arrow d,
The nut (2.1) is pressed against the fourth fulcrum 1 at the other end (20b). However, the nut (24) l is the feed screw 081.
Because it is screwed into the 4th fulcrum (251 swing,
As shown by the imaginary line in the figure, the second fulcrum (2t) swings relative to the fourth fulcrum (25) in the direction of arrow e. And since the fourth fulcrum (25) can slide in the vertical direction with respect to the nut (2 (a)),
The second fulcrum 01) is moved in the direction of arrow f, which is the lateral direction. Therefore, the feed block (15) is the optical block (13).
) is moved (returned) in the opposite direction to the deviation ΔX of the reading point P when tilting the optical block (13
) is corrected to the original reading point P.

Next, conditions for correcting the deviation of the reading point P will be explained with reference to FIGS. 5 and 6. First, in Fig. 5, the first fulcrum (141, second fulcrum c!1), sixth fulcrum (23-input fourth fulcrum (c)) are set to 0.0', Q, R, respectively, and the disk α2 ) is tilted by Δθ, the swing angle of the connecting member (20) for tilting the optical axis OA of the optical block (13) by Δθ is assumed to be Δθ'. Assuming that Δθ is minute, the reading point P
If the deviation ΔX is equal to the amount of movement of the fourth fulcrum (25), then OPxΔθ=0' RxΔθI Since the amount of movement of the third fulcrum (23) is equal, OQxΔθ
= O'Q x Δθ' In order for the above two equations to hold true using Rendo's Δθ and Δθ', UP o'1t OQ O'Q. In other words, the reading point P for the first fulcrum circle and the third
If it is equal to the ratio of the distance between the fourth fulcrum (25) and the third fulcrum (23) with respect to the second fulcrum (21), then the deviation ΔX of the reading point P is is equal to the amount of movement of the fourth fulcrum (25). If the fourth fulcrum (25) is not moved as shown in FIG. is moved. Therefore, the optical block (131) is also moved by ΔX, and the deviation of the reading point P is corrected.

That is, according to the present invention, when the optical block 03) is swung by the oscillation of the connecting member (201), the deviation of the reading point P is caused by the connecting member (201) moving the feed block 09. Then, it will be automatically corrected mechanically as usual.

Therefore, as shown in FIG. 6, the optical block (13) is always oscillated about the reading point P as an approximate center, and tilts the optical axis OA according to the inclination of the disc (+21) to tilt the optical axis OA to the disc (+21).
121, the reading point P can be prevented from shifting. Note that the approximate center means that the deviation of the reading point P is extremely small and is within a range where tracking control and focus control of the optical system (10) itself can be easily performed. Since the rocking of the optical block (13) and the accompanying correction of the deviation of the reading point P are simultaneously performed by the connecting member (2I), skew correction can be performed extremely reliably. Since the pressure does not depend on the feeding mechanism, it can sufficiently cope with high-speed access of the feeding mechanism.

Next, detection of the inclination of the disk (121) will be explained based on FIG. 7.

As shown in the figure, within the optical system QOJ, the luminous flux emitted from a laser light source consisting of a semiconductor laser, for example, is
The light passes sequentially through the wavelength plate 051 and the objective lens aυ and is focused as a fine spot on the disk reflective surface (12a).

Then, the reflected light beam reflected and diffracted by the disk reflective surface (12a) passes through the objective lens fi1), the wavelength plate f451° beam splitter (44), and the convex lens (46) in order, and then passes through the photodetector (4n). Here, if the disk 021 is tilted by Δθ in the radial direction, ie, the arrow a direction, the disk (
The reflected light beam from the side 13 is laterally displaced by 2-Δθ·fl with respect to the optical axis OA, assuming that the focal lengths of the objective lens 0υ and the convex lens (46) are fl and f2, respectively. The reflected light flux projected onto the light receiving surface of the photodetector (4η) is
Radial direction a'elJ projected as shown in FIG.
It is laterally displaced by l. The displacement distance ΔL is: S: The optical path length between the convex lens (41i1) and the light receiving surface of the photodetector (4η).

The light-receiving surface of the photodetector (4'71) is formed of two light-receiving areas A%B lined up in the projected radial direction a' as shown in the figure.The number and arrangement of these light-receiving areas A1B In order to simplify the explanation, the detection of the inclination of the disk (12) is limited to only the radial direction a, and no consideration is given to tracking control and focus control. By obtaining an output difference of 3.%B = 8ASB, the second Tanabata (28) is rotated in the forward and reverse directions according to the output difference Sa, and the optical block 0 is swung to move forward. The axis OA can always be tilted perpendicularly to the disk (12).

Note that the connecting member ( )) in the present invention is not limited to the shape shown in the embodiments, and can be modified in various ways.

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

Effects of the Invention The present invention provides an optical block, a feeding block that holds the optical block and is transported along a guide, and a first
A feed screw driven by a motor, a nut into which the feed screw is screwed, and a connecting member connecting the feed block and the nut, and the optical block is arranged on the optical axis. The feed block ζ is swingably supported through a first fulcrum, the connecting member is swingably supported on the feed block via a second fulcrum, and one end of the connecting member is is engaged with a third fulcrum provided at an eccentric position with respect to the first fulcrum, and the other end is engaged with the nut via the fourth fulcrum, so that the nut is fixed to the feed block and is fixed to the inclination of the disk. Since the optical disc device is provided with a second motor that swings the connecting member around the second fulcrum in response to the swinging movement of the connecting member, when the optical block is swung by the swinging of the linking member, The deviation of the reading point is always mechanically and automatically corrected by the connecting member moving the feed block. Therefore, the optical block is always oscillated with the reading point as the approximate center, and when the optical block is tilted according to the tilt of the disk and the optical axis is corrected so that it is always perpendicular to the disk. , it is possible to prevent the reading point from slipping as much as possible, and it is possible to always accurately irradiate the original reading point with the light beam.

In the skew correction of the present invention, the movement of the optical block and the correction of the deviation of the reading point caused by the movement are simultaneously performed by the connecting member, so that the operation can be performed extremely reliably. Furthermore, since the skew correction of the present invention does not depend on the feeding mechanism, it can sufficiently cope with high-speed access by the feeding mechanism.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a reading optical system of a conventional optical disc device. FIGS. 2 to 8 show an embodiment of an optical disc device to which the present invention is applied, in which FIG. 2 is a front view showing a state in which the optical block is swung, and FIG. A front view showing the state in which the feed block has been moved, Figure 4 is I of Figure 2.
A cross-sectional view along the V-IV line, Figures 5 and 6 are diagrams showing the conditions under which the deviation of the reading point is corrected, and Figures 7 and 8 are optical diagrams explaining the method for detecting the tilt of the disc. FIG. 2 is a cross-sectional view along the optical axis of the system and a plan view of the light-receiving surface of the photodetector. In addition, in the code used for 1st control, there is an optical system (12
・・・・・・・・・・・・・・・Disc A3・
・・・・・・・・・・・・・・・・・・Optical block Qa
・・・・・・・・・・・・・・・・First fulcrum α・・・・・・・・・・・・・・・・・・・Feed block (1
6a) (16b)-Guide (171...... 1st motor (Group I...) ...Feed screw (21)...Connecting member (20a)...One end (2
0b)......Other end (21)...
・・・・・・・・・・・・・・・Second fulcrum ■)・・・・
......Third fulcrum C4...
・・・・・・・・・・・・・・・Natsuto(ha)・・・・・・
・・・・・・・・・・・・・Fourth fulcrum (a)・・・・
.....This is the second motor. Agents Masaru Saturn〃 Yoshio Tsunekako〃 Shun Sugiura Negative. Figure 2 Figure 3

Claims (1)

[Claims] an optical block, a feed block that holds the optical block and is transported along a guide, a feed screw driven by a first motor, a nut screwed onto the feed screw, the feed block and the above. a connecting member that connects between the optical block and the nut, the optical block is swingably supported on the feed block via a first fulcrum disposed on the optical axis, and the optical block is pivotably supported on the feeding block via a first fulcrum disposed on the optical axis, and The connecting member is pivotably supported on the feed block via a fulcrum, one end of this connecting member is engaged with a sixth fulcrum located eccentrically with respect to the first fulcrum, and the other end is connected to the nut ζ. A second Tanabata is engaged via the fourth fulcrum, is fixed to the feed block, and swings the connecting member about the second fulcrum in accordance with the inclination of the disk. An optical disc device consisting of