JP3442756B2 - Optical disk drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device for recording or reproducing information on an information recording medium such as an optical disk. [0002] As is well known, a compact disk (C
As represented by D) and a laser disk (LD), an optical disk device that reproduces information using a laser beam is widely used. Recently, the optical disk device has been used as a storage device of a computer. [0003] When recording / reproducing information on / from an optical disk, it is performed by focusing a laser beam on the optical disk surface using an objective lens to form a spot. The smaller the spot size, the higher the recording density on the optical disk. In order to increase the recording density of information that can be recorded on an optical disk, it is effective to shorten the wavelength of a laser beam used and increase the numerical aperture (hereinafter referred to as NA) of an objective lens. It is also important to make the optical axis of the objective lens perpendicular to the optical disk as much as possible, and to suppress coma caused by tilting the optical axis. Since the angle at which coma aberration is generated is proportional to the wavelength and inversely proportional to the cube of NA, the allowable angle deviation decreases as the recording density increases, and the component accuracy and assembly accuracy must be improved. However, optical disks are generally manufactured by injection molding, and inevitably warp and other distortions occur, and the optical disk surface is tilted. Also, the optical disk itself warps due to its own weight. When such an inclination of the optical disk surface is divided into two components, a circumferential direction and a radial direction, the inclination caused by the disk in the circumferential direction is a rotation synchronization component of the optical disk, and this correction requires a high-speed driving device. On the other hand, in the tilt caused by the disk in the radial direction, there is a component that is a function of the radial position of the disk in addition to the rotation synchronization component of the optical disk, and the component that is a function of the radial position of the disk is corrected. By itself, the amount of generation of coma aberration is considerably improved. For this reason, an optical disk device having an actuator capable of correcting tilt in the radial direction as shown in FIG. 7 having a drive device for correcting the tilt in the disk radial direction has been devised. FIG. 7 is a schematic diagram showing a configuration of main components of an optical disc device provided with a conventional tilt correction device. Referring to FIG. 7, an optical disk 101 includes a turntable 104 mounted on a spindle motor 103.
It is mounted on a tower and rotates. The spindle motor 103 is attached to the base 102. Objective lens 116
Has a small optical axis tilt tolerance of the objective lens 116 with respect to the disk 101. The objective lens 116 is mounted on the objective lens holder 114 of the objective lens driving device 112.
A shaft 115 in the objective lens driving device is inserted into a hole provided in the objective lens holder 114, and the objective lens
Is focused on the optical disk 101 and rotated about the axis 116, the focal position can be adjusted to a desired track position on the optical disk 101. The base 113 of the objective lens holder 114 is connected to the carriage 105. The carriage 105 also includes optical elements such as a laser diode and a light receiving element (not shown) and a sensor for detecting the inclination of the optical disk 101 with respect to the carriage 105 (not shown). The carriage 105 includes guide rails 106 a and 106 b fixed on the sub-base 109.
Thus, the optical disk 101 is supported so as to be movable in the radial direction. By driving the feed screw motor 108 for driving the feed screw 107, the carriage 105 is driven.
Moves. Note that the objective lens driving device is positioned on the carriage 105 such that the extension of the locus of the center of the objective lens 116 passes through the rotation center of the turntable 104. The sub base 109 includes shafts 111a and 111b.
To the base 102 so as to be rotatable and parallel to the circumferential direction of the sub-base rotating motor 110. Based on the signal from the tilt sensor described above, the sub-base rotating motor 110 is controlled so that the optical axis of the objective lens 116 corrects the tilt of the optical disc 101. As described above, in the conventional optical disk device, the base has a double structure of the base 102 and the sub-base 109, and when arranged horizontally as shown in FIG. 7, a space is required in the width direction. It is also possible to make the paper double in the vertical direction on the paper surface, but in this case, a space is required. Further, since the large sub-base is rotated, a space for moving the sub-base is required up and down. In general, an optical disc device must include various components such as an electronic circuit board, a base support mechanism, a housing, and a loading mechanism (not shown). There was a problem that the whole had to be enlarged. In addition, a large driving force is required to move a large movable portion, and there are also problems such as an increase in power consumption due to an increase in responsiveness and energy required for driving. In addition, as described in Japanese Utility Model Publication No. 5-10249, a carriage 3 on which an optical pickup 4 is mounted is described.
The skew cam 15 and the arm 4E are in contact with each other in order to rotate the optical disc in the radial direction of the optical disc for tilt correction. However, the skew cam 15 and the arm 4E
Are in point contact with each other in a direction perpendicular to each other, so if the skew cam 15 is rotated many times for tilt correction or seek is repeated, the durability of the contact surface will be insufficient such as wear. there were. As described above, in the conventional optical disk device, the mechanism for correcting the tilt of the optical disk becomes large, so that the optical disk device itself becomes large. was there. Another problem is that the durability of the tilt correction mechanism is insufficient. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, to reduce the size of the tilt mechanism, and to provide an optical disk device having excellent durability. [0014] In the optical disk apparatus of the present invention SUMMARY OF THE INVENTION comprises a carriage mounting the optical head for reproducing information from an optical disk to rotate, the light head mounted on said carriage, said optical disk A guide rail for moving in the radial direction, and along the guide rail
Movably supported and pivots the carriage
A slider that can be mounted parallel to the guide rail, and the eccentric cam shaft for tilting the carriage in a radial direction of the optical disc, provided on the eccentric cam shaft,
A line contact with the carriage and the carriage
A tilting means for rotating the eccentric cam shaft provided with the buffering member, and a tilt detecting means for detecting a tilt of the optical disc. According to the detected tilt amount, the eccentric cam shaft and the
The carriage is tilted by rotating a buffer member . The eccentric cam shaft is rotated in order to move the carriage in a direction to eliminate the influence of the tilt of the optical disk, thereby moving the carriage up and down in the radial direction of the optical disk. Is line contact. As a result, the same line contact as the carriage and the slider with excellent durability can be achieved, and a mechanism with excellent durability against tilt operation can be realized. By providing a cushioning member between the eccentric cam shaft and the carriage, wear of both contacts is reduced, and durability can be increased. It is characterized in that a slider movable along the guide rail is provided, and the carriage is provided on the slider. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing the configuration of main components of an optical disk device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of the optical disk device taken along line AA 'in FIG. 1, and FIG. Among them, a perspective view showing a schematic configuration diagram of the carriage 7 and the tilt mechanism, FIG. 4 is a diagram schematically showing the movement of the carriage 7 by the tilt mechanism of FIG. 3, and FIG. 5 is a perspective view from the C direction of FIG. is there. In this embodiment, the spindle motor 3
Is directly attached to a base (not shown), and is not tilted. The spindle motor 3 is provided with a turntable 5. The optical disc 1 is mounted on the turntable 5, and the optical disc 1 is rotated by rotating the spindle motor 3. In order to reproduce or record information from the entire surface of the optical disk 1, an optical head 8 having objective lenses 14 and 15 is provided on the carriage 7. The objective lens
Among the objective lenses 14 and 15, for example, the objective lens 14 is an objective lens that does not require the inclination correction in the disk radial direction.
Laser light passing through 14 is 780 nm (for CD-ROM disc playback)
The objective lens 15 requires tilt correction in the radial direction of the disc, and the laser beam passing through the objective lens 15 is 650 nm (for reproducing a DVD disc). The optical head 8 is provided on the carriage 7. However, the carriage 7 is not guided by the guide rails 8a and 8b for moving the optical head 8 to the radius of the optical disc 1, and the slider 30 is provided with rotating pins 31a and 31b coaxially mounted on the carriage 7. Shaft hole 301
Has been inserted. And the slider 30 is a slider
The guide rail 8 is inserted into the shaft hole 301 and the U-shaped groove 302 provided in 30.
a and 8b are passed along the guide rails 8a and 8b so as to be movable along the guide rails 8a and 8b, and can be moved in the disk radial direction by a feed motor (not shown). That is,
As shown in FIG. 5, by moving the slider 30 in the radial direction of the optical disc 1 along the guide rails 8a and 8b,
The carriage 7 connected to the slider 30 by the rotating pins 31a and 31b and provided with the optical head 8 also moves. The carriage 7
Is provided with a tilt sensor for detecting a tilt amount of the optical disc 1 described later. Note that the tilt sensor may be provided in the optical head 8. Instead of directly detecting the tilt amount, the tilt amount may be changed, and the jitter amount or error rate of the reproduced signal may be monitored, and the tilt amount may be measured indirectly by finding the best tilt amount. Next, the tilt mechanism of the optical disc 1 in the radial direction will be described. As shown in FIGS. 3 (a) and 3 (b),
The directions of a and 31b are perpendicular to the rotation axis of the spindle motor 3 and parallel to the axis perpendicular to the guide rails 8a and 8b. In FIG. 3, the carriage 7 includes rotating pins 31a and 31b.
As shown in the figure, the end of the carriage 7 moves vertically in the drawing. This corresponds to the carriage 7 moving in the vertical direction on the paper centering on the rotation pins 31a and 31b (not shown) on the left in FIG. 2, and the carriage 7 extending in the vertical direction on the paper in FIG. It corresponds to moving in the direction. As shown in FIG. 3, the carriage 7 is provided with bearings 35a and 35b, in which bushes 34 are provided as buffer members for preventing the contact between the carriage 7 and the eccentric cam shaft 33 from being worn. The rotation pins 31c and 31d of the bush 34 are fitted, and the bush 34 can rotate around the rotation pins 31c and 31d with respect to the carriage 7 and move in the rotation axis direction. The bush 34 is pressed against the eccentric cam shaft 33 because the coil spring 32 generates a preload in a direction to attract the carriage 7 and the slider 7. Eccentric cam shaft 33
1, as shown in FIG. 2, parallel to the guide rails 8a and 8b, one end is rotatably supported by a base (not shown), and the other end is connected to the tilt motor 12, and can be rotated by the tilt motor 12. It is. Further, the eccentric cam shaft 33 is eccentric as shown in FIGS. When the tilt motor 12 rotates, the eccentric cam shaft 33 rotates. As a result, the bush 34 becomes eccentric camshaft 3
In accordance with 3, the rotating pins 31c and 31d slide in the bearings 35a and 35b, respectively, so that the rotating pins 31c and 31d move in the vertical direction and the vertical direction in FIG. At this time,
Carriage 7 on which bush 34 is movably supported
Rotates the slider 30 around the rotation pins 31a and 31b. The movement of the carriage 7 by the tilt mechanism using the eccentric cam shaft 33 will be described with reference to FIG. The operation is exaggerated for the sake of explanation. In FIG. 4, in order to show the relationship between the movement of the eccentric cam shaft 33 and the carriage 7, the carriage 7, the bush 34, the rotating pins 31b and 31d are shown.
Only shown. FIG. 4 (ii) shows a state where the inclination of the carriage 7 with respect to the optical disc 1 in the radial direction of the optical disc 1 is zero. As a result of the tilt detection described later, if the optical disk 1 is tilted upward in the drawing, the carriage 7 needs to be in the state shown in FIG. 4 (i). Therefore, when the eccentric cam shaft 33 is rotated by the tilt motor 12 (not shown), the bush 34 is moved upward in the drawing.
Thereby, the carriage 7 can be changed from the state of FIG. 4 (ii) to the state of FIG. 4 (i). Note that the carriage 7 is
While rotating about the rotation center 1b, the bush 34 is rotated by a rotation pin 31 fitted into a bearing 35b provided on the carriage 7.
The rotation of the bush 34 with respect to the carriage 7 about the rotation center d does not change the inclination of the bush 34 with respect to the eccentric cam shaft 33. Similarly, when the optical disk 1 is tilted downward in the drawing, the carriage 7 needs to be in the state shown in FIG. 4 (iii). Therefore, when the eccentric cam shaft 33 is rotated by the tilt motor 12 (not shown), the bush 34 is accordingly moved downward in the drawing. Thereby, the carriage 7 can be changed from the state of FIG. 4 (ii) to the state of FIG. 4 (iii). Next, a tilt sensor according to an embodiment of the present invention will be described with reference to FIG. FIG. 6 is a diagram showing the configuration and operation of the tilt sensor. The tilt sensor of this embodiment is a radial tilt sensor for detecting the amount of tilt of the optical disc 1 in the radial direction, and is mounted on the slider 30. The tilt sensor includes an LED (Light-emitting diode (Light Emitting Diode)) (not shown) with a lens (not shown) (which may be an LD (Laser Diode)) as a light emitting unit, and a four-divided PD (Phote Ditector) 38 as a light receiving element. Note that 4
Instead of the divided PD 37, two position sensors arranged in the TAN direction in FIG. 6 may be used. The light emitted from the LED is split by the half mirror 39 fixed to the carriage 7 into light that is transmitted and travels toward the optical disc 1 and light that is reflected and travels toward the quadrant PD 38. The transmitted light is reflected on the same radius of the optical disc 1 as the position where the light emitted from the optical head 8 is focused, and returns to the four-divided PD 38. The light reflected from the half mirror 39 enters the cells 38a and 38b, which are the light receiving elements of the four-divided PD. Cells 38a, 38
The radial inclination of the half mirror 39, that is, the inclination of the optical head 8 in the radial direction can be measured from the difference between the outputs b. Similarly, the light reflected by the optical disc 1 enters the cells 38c and 38d of the four-divided PD 38, and the cells 38c and 38d
The inclination of the optical disc 1 can be measured from the output difference of 38d. Then, in the optical disk drive device of the present embodiment, the tilt motor 12 is driven to tilt the optical head 8 so that the tilt of the optical head 8 measured by the tilt sensor of FIG. This allows the light emitted from the optical head 8 to be perpendicularly incident on the optical disc 1. In this embodiment, the rotation pin 3
By inclining the directions of 1a and 31b, it is possible to adopt a configuration in which the inclination of the objective lens 15 can be optimally corrected. As a result, the optical disk of the objective lens 15 located at a position deviated from the radial line segment from the center of the optical disk 1
The amount of tilt in the circumferential direction of 1 is reduced, thereby reducing coma aberration, thereby enabling recording or reproduction on a higher density optical disc. It should be noted that the details of the reduction of the inclination in the circumferential direction due to the arrangement of the two objective lenses are omitted since JP-A-2001-184688 has a detailed description. The rotary pins 31a, 3a of this embodiment
Instead of 1b, an elastic support mechanism such as a leaf spring hinge can be used, and a tilt sensor is built in the optical head 8, and the tilt sensor measures the tilt of the optical disc 1 with respect to the optical head 8. Thus, tilt control can be performed. Instead of directly detecting the tilt amount, the tilt amount may be changed, and the jitter amount or error rate of the reproduced signal may be monitored, and the tilt amount may be measured indirectly by finding the best tilt amount. According to the present embodiment, in order to perform radial tilt correction, satisfactory radial tilt correction can be performed using only the carriage 8 and parts around the carriage 8 without moving the base. In addition, since the distance between the optical head 8 and the optical disk 1 hardly changes, the operating range of the optical head 8 in the focus direction hardly needs to be widened for radial tilt compensation, so that the optical head 8 does not increase in size. The optical head 8 has a mechanism for moving the objective lenses 14 and 15 in the focus direction without tilting the lenses. However, it is very difficult to move the objective lenses 14 and 15 without tilting at all, and the operation direction in the focus direction is short. The shorter the
Less inclination is required. If the objective lenses 14 and 15 are tilted, coma also occurs, so that the objective lens travel distance in the focus direction is extended for radial tilt compensation,
As a result, it is meaningless that the objective lenses 14 and 15 are tilted. Therefore, it is not necessary to extend the operating range in the focusing direction. This is because it is not necessary to design and manufacture the actual optical head 8 and the cost is increased. And is very advantageous. The carriage 7 has a rotating bush 3
It is in contact with the eccentric camshaft 33 through 4. This contact state is a line contact, which is the same as the state in which the slider 30 is in contact with the guide rails 8a and 8b, and is not a point contact. As described above, according to the present invention, it is possible to reduce the size of the tilt mechanism and provide an optical disk device having excellent durability.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view showing a configuration of main components of an optical disc device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the optical disc device taken along line AA ′ of FIG. FIG. 3 is a perspective view showing a schematic configuration diagram of a carriage 7 and a tilt mechanism in FIG. FIG. 4 is a diagram schematically showing the movement of a carriage 7 by the tilt mechanism of FIG. 3; FIG. 5 is a perspective view from the direction C in FIG. 1; FIG. 6 is a diagram showing the configuration and operation of a tilt sensor. FIG. 7 is a schematic diagram showing a configuration of main components of a conventional optical disk device.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B ^7/ 09-7/10

Claims (1)

(57) a carriage for mounting an optical head for reproduction of the Claims 1] Information from the rotating optical disk, the optical head mounted on the carriage, is moved in the radial direction of the optical disc And a guide rail for moving along the guide rail.
A slider on which the carriage is rotatably mounted; an eccentric cam shaft parallel to the guide rail for tilting the carriage in a radial direction of the optical disk; and an eccentric cam shaft provided on the eccentric cam shaft. Line contact with carriage
And a buffer portion rotatable with respect to the carriage.
Material, a cam rotating means for rotating the eccentric cam shaft provided with the cushioning member, and a tilt detecting means for detecting a tilt of the optical disc, and according to a tilt amount detected by the tilt detecting means. The eccentric cam shaft and the loose
An optical disc device characterized in that the carriage is tilted by rotating an opposing member .