JP2001134968A - Optical head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical head capable of tracking control that excels in high-speed follow-up ability. SOLUTION: An optical head is equipped with a riser mirror 2 which reflects a laser beam coming from a light source in a focus direction, an objective lens 4 which converges the laser beam thus reflected by this riser mirror 2 in a manner that a beam spot is formed on an optical recording medium D, and a carriage 1 which supports this objective lens 4 and the riser mirror 2, and the carriage 1 is freely movable in a tracking direction by the driving force of a driving means 5 which is loaded on this carriage 1 and includes coils 50A, 50B for generating the driving force, and the riser mirror 2 is designed so that its angle can be freely changed in the tracking direction by the driving force of the driving means 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head used for writing data on an optical recording medium such as an optical disk and reading data from the optical recording medium. The optical disk referred to in this specification includes a magneto-optical disk on which data is written or read by a magnetic field modulation method or an optical pulse modulation method.

[0002]

2. Description of the Related Art An example of a conventional optical head is shown in FIG.
The illustrated optical head H is configured by mounting a rising mirror 91 and an objective lens 92 on a carriage 90. In the optical head H, a laser beam traveling in a horizontal direction from a light source (not shown)
When the laser light travels through the opening 90a, the laser light passing through the opening 90a is reflected upward by the rising mirror 91 and enters the objective lens 92. Then, the laser light is focused by the objective lens 92 and the optical disc D
A beam spot is formed on the recording surface of. The objective lens 92 includes one or a plurality of lenses, and is supported so as to be displaceable in the focus direction so that focusing control can be performed. The focus direction in this specification is a direction facing the recording surface of the optical disc D, and is a direction indicated by an arrow fs in FIG.

A carriage 90 is supported by a pair of horizontal guide members 93, and a pair of voice coil motors 8 are provided.
Reciprocating movement in the tracking direction by the driving force of. The tracking direction referred to in this specification is a direction that intersects a track of the optical disc D, and is a direction indicated by an arrow Tg in FIG. Voice coil motor 8
Is composed of a magnet 80 and a yoke 81 fixed and provided separately from the carriage 90, and a coil 82 loosely fitted to a part of the yoke 81 and attached to the carriage 90. . According to the voice coil motor 8, the magnetic flux generated by the magnet 80 and
The interaction with the magnetic field generated by the current flowing through the coil 82 allows the carriage 90 to move in the tracking direction. By the movement of the carriage 90, the positioning control of the optical head H, that is, the operation of detecting the target track of the optical disc D (seek operation), and the position where the optical head H writes or reads data is shifted from the target track. (Tracking control) so as not to cause the following.

[0004]

In recent years, the storage capacity of optical disks has been increased, and there has been a strong demand for faster recording / reproducing processes. Therefore, high-speed responsiveness is required for focusing control and tracking control. The focusing control is performed by displacing the objective lens 92 in the focus direction. In this case, the movable part is small in size and light in weight. Therefore, the displacement of the movable member can be performed at a high speed, and focusing control can be relatively easily performed at a high speed.

However, regarding tracking control,
In addition to the carriage 90 on which the objective lens 92 and the rising mirror 91 are mounted, it is necessary to displace the entire optical head H including the coil 82 attached to the carriage 90 in the tracking direction. The overall size and weight of these movable parts are significantly larger than those for performing focusing control. Therefore, it is difficult to move the movable part to a predetermined position at high speed and with high accuracy. Therefore, conventionally, it is difficult to cope with high-speed tracking control as compared with focusing control, and there has been a problem that the tracking follow-up residual tends to increase with the speeding up of data recording / reproducing processing on an optical disc. .

The present invention has been conceived under such circumstances, and has as its object to provide an optical head capable of performing tracking control excellent in high-speed tracking.

[0007]

DISCLOSURE OF THE INVENTION In order to solve the above problems, the present invention employs the following technical means.

An optical head provided by the present invention forms a rising mirror for reflecting a laser beam traveling from a light source in a focus direction, and forms a beam spot of the laser beam reflected by the rising mirror on an optical recording medium. Lens, and a carriage supporting the objective lens and the rising mirror, and the carriage is provided with a driving force generating coil mounted on the carriage. An optical head, which is movable in a tracking direction by a driving force of a driving unit including: the rising mirror can freely change an angle in the tracking direction by a driving force of the driving unit. It is characterized by that.

In the optical head having such a configuration,
By changing the angle of the rising mirror, the angle of incidence of the laser beam on the objective lens can be changed, and the position of the beam spot formed on the optical recording medium can be moved in the tracking direction. On the other hand, since the angle change of the rising mirror is performed by using the driving force of the driving means for moving the carriage in the tracking direction, for example, a dedicated mirror for changing the angle of the rising mirror is used. Unlike the case where the drive source is newly mounted on the carriage, it is possible to suppress an increase in the total weight of components mounted on the carriage.
Therefore, in the present invention, when tracking control is performed, while the carriage is moved in the tracking direction at substantially the same speed as the conventional optical head, the following residual that cannot be dealt with only by the movement of the carriage is:
It is possible to quickly and delicately deal with the change of the angle of the rising mirror and eliminate it, and it is possible to perform tracking control that is superior in high-speed follow-up performance as compared with the related art.

In a preferred embodiment of the present invention, a shaft for supporting the rising mirror is rotatably mounted on the carriage, and the driving means includes a coil and a moving member for moving the carriage. A voice coil motor configured by combining a magnet disposed around a region, wherein the coils are first coils respectively connected to the shafts and capable of generating a couple for rotating the shafts. And a second coil.

According to this configuration, the rising mirror can be rotated by the couple generated by the first coil and the second coil of the voice coil motor for moving the carriage in the tracking direction. Can,
By this rotating action, the angle of the rising mirror can be appropriately changed. With such a configuration, a mechanism for changing the angle of the rising mirror can be simplified, which is suitable for suppressing an increase in the number and weight of components mounted on the carriage, and It is also possible to increase the reliability and reliability of the angle changing operation of the rising mirror.

In another preferred embodiment of the present invention, the voice coil motor moves the carriage when the current in the same direction is applied to each of the first coil and the second coil. The first couple and the second coil are configured to generate the couple when currents in different directions are supplied to the first coil and the second coil, respectively.

According to such a configuration, the operation of moving the carriage in the tracking direction and the operation of changing the angle of the rising mirror by switching the direction of the current flowing through the first coil and the second coil. Can be easily switched, and tracking control can be facilitated.

Other features and advantages of the present invention will become more apparent from the following description of embodiments of the present invention.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be specifically described below with reference to the drawings.

1 to 4 show an example of an optical head according to the present invention. 1, the optical head A according to the present embodiment is incorporated in an optical disk device B which rotates the optical disk D while horizontally supporting the optical disk D on a spindle 60, and includes a rising mirror 2, an actuator Each of the objective lens 3 and the objective lens 4 is mounted on the carriage 1. The optical disc device B is also provided with a pair of voice coil motors 5 for moving the carriage 1 in a tracking direction indicated by an arrow Tg.

The carriage 1 is guided and supported by a pair of bar-shaped guide members 61 so as to be movable in the tracking direction below the optical disk D. The rising mirror 2 is attached to a shaft body 20 rotatably held by the carriage 1 as well shown in FIGS. 2 and 3, and as will be described later, the first and second coils 5.
By the action of 0A and 50B, it is possible to rotate together with the shaft body 20. In the rising mirror 2, a laser beam emitted from a laser diode (not shown) and then passed through a collimator lens and made into parallel light travels through an opening hole 10 provided on one side surface of the carriage 1. It is configured to come. As shown in FIG. 2, the rising mirror 2 plays a role of reflecting the laser light upward and making the laser light incident on the objective lens 3 located above the rising mirror 2.

The objective lens 4 focuses the laser beam reflected by the rising mirror 2 to form a beam spot on the recording surface Da of the optical disk D. The objective lens 4 may be composed of a single lens. However, from the viewpoint of increasing the data recording density of the optical disc D by suppressing the spherical aberration and increasing the numerical aperture, the objective lens 4 is constituted by combining a plurality of lenses. Sometimes it is. The objective lens 4 is supported by the actuator 3 with its lens axis L extending in the focus direction (vertical direction in the present embodiment).

The actuator 3 is displaceable in the focus direction, and is supported by the carriage 1 via a leaf spring 30 that can be bent and deformed in the focus direction. As shown in FIG. 3, coils 31 are provided on both side edges in the width direction of the actuator 3, and magnets 32 facing the coils 31 are fixedly provided on the carriage 1. Have been. When the coil 31 is energized, the actuator 3
The interaction between the current and the magnetic flux generated by the magnet 32 allows the displacement by a predetermined amount in any of the upward and downward directions. In the optical head A, by the operation of the actuator 3,
Focusing control is performed. In the present embodiment, the objective lens 4 is supported by a so-called one-dimensional actuator that can be displaced only in the focus direction, but the present invention is not limited to this. In the present invention, for example, the objective lens 4 may be supported by a two-dimensional actuator that can be displaced in a focus direction and a horizontal direction (tracking direction or track direction) perpendicular to the focus direction.

Each voice coil motor 5 is provided with first and second coils 50A and 50B, a magnet 51, and a yoke 52. The magnet 51 and the yoke 52 constitute a magnetic circuit in a broad sense. The yoke 52 is made of a ferromagnetic material, and is formed in a rectangular frame shape in a plan view, as best seen in FIG. The yoke 52 extends in parallel with the base 52c to which the magnet 51 is fixedly attached,
And guide portions 52a and 52b separated into upper and lower stages.

First and second coils 50A, 50B
Are mounted on the carriage 1 so as to overlap each other vertically. More specifically, a pair of flange portions 21 are continuously provided at both ends of the shaft body 20 that supports the rising mirror 2. First and second coils 50 </ b> A, 50 </ b> A, 50B are connected to each other. Guide portions 52a and 52b of the respective yokes 52 are inserted into the first and second coils 50A and 50B, respectively. In the voice coil motor 5, when a current flows through the first and second coils 50 A and 50 B, the interaction between the current and the magnetic flux by each magnet 51 causes the first and second coils 50 A and 50 B to interact. Is generated so as to move along the guide portions 52a and 52b. Of course, since the first and second coils 50A and 50B have a structure attached to the carriage 1 via the shaft body 20, the carriage 1 is moved by the above-mentioned force to the guide portions 52a and 52b and the pair of guide members 61. It is possible to move along.

The magnitude and direction of the current flowing through each of the first and second coils 50A and 50B can be individually controlled. When currents in the same direction flow through the first and second coils 50A and 50B, the directions of the driving forces generated by the coils 50A and 50B coincide with each other. Along the tracking direction. The moving speed can be controlled by the magnitude of the current. In contrast, the first and second coils 50A, 50A
B, when a current flows in the opposite direction, for example, as shown in FIG. 4, the first and second coils 50A, 50A,
The directions N1 and N2 to which each of 50B tries to move are opposite to each other. Then, the first and second coils 50A and 50B generate a couple T that rotates the shaft body 20 around its center. The rising mirror 2 is configured to rotate in the tracking direction together with the shaft body 20 by the couple T. At this time, the movement of the carriage 1 in the tracking direction can be stopped. First and second coils 50
If the directions of the currents flowing through A and 50B are switched in the opposite directions, the shaft body 20 and the rising mirror 2 can be rotated in the direction opposite to the direction shown in FIG. As described above, in the optical head A, the operation of moving the carriage 1 in the tracking direction and the rotation of the rising mirror 2 in the tracking direction are performed by switching the direction of the current flowing through the first and second coils 50A and 50B. Operation can be selectively performed.

Next, the operation of the optical head A having the above configuration will be described.

First, in order to write data to or read data from the optical disk D, it is necessary to control the positioning of the optical head A in the tracking direction while the optical disk D is rotated at a high speed by the spindle 60. The positioning control includes a seek operation for moving the optical head A to a position corresponding to a target track on the optical disk D at a high speed, and a beam spot of a laser beam from the target track, as described in the related art. And a tracking control operation for following the vehicle so as not to shift. As a method of detecting the position of the target track, for example, a conventionally known method of a track servo system or a data track servo system may be used, and specific contents thereof will be omitted.

The above-described seek operation can be performed by moving the carriage 1 in the tracking direction by supplying currents in the same direction to the first and second coils 50A and 50B of the voice coil motor 5. The carriage 1 has a pair of first and second coils 50A, 50B.
Is mounted, and the number of coils mounted on the carriage 1 is larger than that of the conventional optical head H shown in FIG. 6, but the carriage 1 and all the components mounted on the carriage 1 And the total weight of the movable part can be made not much different from the total weight of the movable part of the conventional optical head H. In the optical head A of the present embodiment, the size of each of the coils 50A and 50B is made larger than that of the conventional voice coil motor by the number of the coils 50A and 50B of the voice coil motor 5 mounted on the carriage 1. The driving force required for operating the carriage 1 properly can be obtained while reducing the size. Therefore, in practice, the weight of the movable portion of the optical head A does not increase in proportion to the increase in the number of coils of the voice coil motor 5, and the increase in the total weight of the movable portion can be appropriately reduced. Can be suppressed. As a result, the operation of moving the optical head A in the tracking direction and disposing the optical head A at a position corresponding to the target track can be performed at the same speed as the conventional one.

Next, regarding the tracking control, in addition to moving the carriage 1 in the tracking direction,
It can also be performed by rotating the rising mirror 2. That is, as described with reference to FIG. 4, the rising mirror 2 includes the first and second coils 50A and 50A.
When an electric current flows in the opposite direction to B, it rotates in the tracking direction and its angle changes. When the angle of the rising mirror 2 changes as described above, the traveling direction of the laser beam reflected by the rising mirror 2 and then directed toward the objective lens 4 changes, so that the beam formed on the recording surface Da of the optical disc D is changed. The spot can be displaced in the tracking direction. The operation of displacing the beam spot by changing the angle of the rising mirror 2 can be performed at a higher speed than the operation of moving the carriage 1 in the tracking direction. Further, the direction in which the beam spot is displaced and the amount of the displacement can be appropriately and accurately controlled by adjusting the direction and magnitude of the current flowing through the first and second coils 50A and 50B. . Therefore, the tracking follow-up residual that cannot be eliminated only by the movement operation of the carriage 1 can be properly eliminated by the displacement of the beam spot due to the change in the angle of the rising mirror 2.

In the optical head A, the angle of the rising mirror 2 can be changed using the first and second coils 50A and 50B constituting the voice coil motor 5. Therefore, as described above, it is possible to suppress an increase in the total weight of the carriage 1 serving as a movable member when the carriage 1 is moved in the tracking direction and various components mounted on the carriage 1, and to perform tracking control in addition to a seek operation. Even when the carriage 1
The movement performance of the vehicle can be prevented from deteriorating.

The specific configuration of the optical head according to the present invention is not limited to the above-described embodiment, and various design changes can be made.

In the present invention, for example, as shown in FIG. 5, a slider 71 may be attached to the carriage 1 via a suspension 70, and the slider 71 may support a part or all of the objective lens 4. it can. According to such a configuration, when the optical disk D rotates at a high speed, the air flows into the gap between the surface of the optical disk D and the slider 71, so that the slider 71 can follow the surface of the optical disk D in a non-contact manner. As a result, coma caused by the tilt of the optical disc D can be eliminated or reduced.

In the above embodiment, the optical head incorporated in the optical disk device has been described as an example.
The present invention is not limited to this. The optical recording medium referred to in the present invention includes a card-shaped recording medium such as a magneto-optical card. Therefore, the optical head according to the present invention can be configured as an optical head used in an apparatus for writing data to a magneto-optical card or reading data, for example.

[0031]

As described above, the optical head according to the present invention is formed on the optical recording medium by changing the angle of the rising mirror while suppressing an increase in the weight of components mounted on the carriage. The beam spot can be displaced in the tracking direction. Therefore, while moving the carriage in the tracking direction at substantially the same speed as that of the conventional optical head, the following residual that cannot be dealt with only by the movement of the carriage is quickly and delicately dealt with by changing the angle of the rising mirror. This can be eliminated, and tracking control that is superior in high-speed tracking performance than before can be performed.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing an example of an optical head according to the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a sectional view taken along the line III-III of FIG. 1;

FIG. 4 is a schematic explanatory view of a structure for rotating a rising mirror.

FIG. 5 is a sectional view of a main part showing another example of the present invention.

FIG. 6 is a perspective view showing a conventional example.

[Explanation of symbols]

 Reference Signs List A optical head D optical disk 1 carriage 2 rising mirror 4 objective lens 5 voice coil motor 20 shaft 50A first coil 50B second coil 51 magnet 52 yoke

Claims (3)

[Claims] 1. A rising mirror for reflecting a laser beam traveling from a light source in a focus direction, and an object for condensing a beam spot of the laser beam reflected by the rising mirror on an optical recording medium. A lens, and a carriage supporting the objective lens and the rising mirror, and the carriage includes a driving force generating coil mounted on the carriage. An optical head which is movable in a tracking direction by a driving force of a means, wherein the rising mirror is capable of freely changing an angle in the tracking direction by a driving force of the driving means. An optical head. 2. A carriage, on which a shaft supporting the rising mirror is rotatably mounted, wherein the driving means includes a coil, a magnet disposed around a moving area of the carriage, and a magnet. And a first coil and a second coil, each of which is coupled to the shaft body and capable of generating a couple for rotating the shaft body. The optical head according to claim 1, wherein: 3. The voice coil motor moves the carriage in the tracking direction when currents in the same direction are applied to the first coil and the second coil, respectively. Coil and the second
The optical head according to claim 2, wherein the couple is generated when currents in different directions are supplied to the respective coils.