JPS6214331A - Optical head - Google Patents

Abstract

PURPOSE:To prevent the generation of a track offset by providing the 1st and 2nd coils which pierce through a magnetic gap of a magnetic circuit member and have prescribed angles in the magnetic gap. CONSTITUTION:When the 1st coil 27 is conducted toward an arrow (g) and the 2nd coil 28 is conducted toward and arrow (j) respectively, the forces f1' and -f2' of motion are produced at both coils 27 and 28 respectively. An objective lens holder 17 is moved toward an arrow (k) together with a carriage 21 by the synthetic force F' of both forces f1' and -f2'. While the synthetic force -F' is produced when the coils 27 and 28 are conducted toward the arrow heads (h) and (i) respectively. Then the holder 17 is moved toward an arrow head (l) together with the carriage 21. Then the prescribed track control or the access control is carried out by controlling the condition direction, the conduction current value or the conduction time of both coils 27 and 28. Thus the stable reading reproduction signal is always secured with no track offset.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical head in an optical disc device.

(Prior Art) Generally, in an optical disc device, laser light from a semiconductor laser or the like is focused onto an optical disc to form fine tracks (
The signal is scanned at intervals of 1.6 .mu.m) to record the signal on the trunk L or read the signal on the track L.

The optical head of such an optical disk device has focus control to keep the laser beam in an appropriate convergence state (spot diameter 1 μm), track control to prevent it from deviating from the convergence point, and furthermore, to search for a desired track. Access control, these three functions are necessary.

In order to satisfy the above-mentioned functions in the optical head of a conventional optical disk device, for example, the objective lens is minutely driven in two directions, the focus direction and the track direction, by an objective lens drive mechanism to perform focus control and track control. Access control was performed by driving the entire optical head consisting of this objective lens drive mechanism and optical systems for detecting various signals. In this case, the objective lens drive mechanism is a magnet,
The optical system includes a magnetic circuit consisting of a yoke, a semiconductor laser as a light emitting source, and various optical components for detecting various signals. I couldn't.

Therefore, by separating the optical system and objective lens drive mechanism,
There is a system in which the optical system is fixed and only the objective lens drive mechanism is a movable part in order to shorten the access time. This type of conventional technology includes IEICE Technical Report (203) (1984
There is something described in January 22 Fl) P, 11-18. FIG. 2 shows a side view of the main parts of a conventional optical head.

FIG. 3 is a front view of the main part.

In FIGS. 2 and 3, the laser beam emitted from the optical system fixing part 1 is optically path-converted by a 45° mirror 2, and is directed onto an optical disk 4 through an objective lens that is appropriately driven in the focus and track directions by an objective lens drive mechanism 3. The reflected light from the optical disk 4 passes through the objective lens and the 45° mirror 2 and returns to the optical system fixing part 1. The objective lens drive mechanism 3
For example, there is one described in JP-A-58-133640. This is achieved by supporting a support body that supports the entire objective lens with an elastic member, and by passing current through two windings arranged in a magnetic circuit configured inside this drive mechanism, the objective lens supported by the support body is moved upward and downward. Two-dimensional minute driving is performed, including focus control by directional movement and track control by rotation of an objective lens eccentrically placed from the rotation center axis of the support. Access control is achieved by passing current through the windings of the bobbins 6m and 6b located in the magnetic gap of the external fixed magnetic circuits 5a and 5b as shown in FIG.
This is done by attaching a 45° mirror 2 and an objective lens drive mechanism 3 and driving the digit pace 7 along guides 8a and 8b.

(Problems to be Solved by the Invention) However, in the apparatus having the above configuration, since the support body supporting the objective lens is supported by an elastic member, unnecessary vibrations occur in the objective lens when accessing at high speed.
Since the light spot also vibrates, there is a drawback that it is impossible to accurately search for a desired track.

Furthermore, when track control is performed by driving the objective lens supported by the support body, as shown in FIG. 4, the objective lens 9
In proportion to the amount of movement δ, the optical axis of the reflected light from the optical disk 4 moves by (=2δ), causing an error in the detection of track deviation by the optical system, resulting in a deviation between the track and the convergence spot of the light beam. (track offset) is generated,
As a result, it also has the disadvantage that the read and reproduced signal is completely reduced by %.

In addition, in the above configuration, if you want to omit track control by driving the objective lens and use the access control system to perform minute track control, the objective lens drive mechanism has an internal magnetic circuit and a large capacity, so high-speed tracking is possible. It had the disadvantage of not being able to

This invention eliminates the problems described in 1 above, enables accurate high-speed access to a desired track, and has excellent high-speed followability.Furthermore, the optical axis of reflection from the optical disk does not move, so An object of the present invention is to provide an optical head that does not cause track offset.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides an optical head of an optical disk device that includes a fixed light source and an optical path of the light beam from the light source and the reflected light from the optical disk. A car horn equipped with all optical path conversion means to change the
a guide member that slidably supports the carriage in the radial direction of the optical disk; a magnetic circuit member that has a magnetic gap and is fixedly arranged in parallel to the guide member;
an objective lens holder which is engaged with the above-mentioned caliper so that the objective lens is fully mounted and can be slid in a direction substantially perpendicular to the optical disk surface; and one of the above-mentioned magnetic circuit members attached to this objective lens holder This device includes a first coil and a second coil that completely penetrate the magnetic gap and are provided at a predetermined angle to each other in the magnetic gap.

(Function) According to the present invention, by controlling the direction of energizing the first coil and the second coil attached to the objective lens holder, as well as the current value or duration of energization,
Based on the relationship between the current flowing through each coil and the magnetic field in the magnetic gap, focus control is performed by moving the objective lens holder relative to the carriage horn, and tracking is performed by moving the objective lens together with the carriage along a guide member. control or access control.

Further, according to the present invention, when performing track control, the objective lens supported by the objective lens holder and the optical path converting means mounted on the carriage move together, so that no track offset noise is generated.

(Embodiment) FIG. 1 is a perspective view of essential parts showing a first embodiment of the present invention, and FIG. 5 is a sectional view taken along line 1-1 in FIG. 1.

In FIGS. 1 and 5, Jl is an optical system including a semiconductor laser, a focus/trunk error detector, and a signal detector, and 12m and 12b are a pair of magnetic circuits, including magnets J, 9a, and J3b. and yoke member 14a
, 14b, J5a, 15b, the magnetic gear horn 16
Closed magnetic circuits having a and 16bf are respectively formed.

These optical system 11 and magnetic circuit 12 are each fixed to a frame (not shown).

17 is an objective lens holder, and on the outer peripheral surface of this objective lens holder 17, a focus control coil 18 as a first coil and track control coils J9a and J9b as second coils are connected to magnetic gears 7 16&, 16b. They are wound so that they are approximately perpendicular to each other. Further, the objective lens holder 17 has a cylindrical portion 17af at the center inside thereof,
An objective lens 20 is attached to one end thereof, and a hole J7b is provided in a part thereof for passing laser light.

2 is a carriage having a cylindrical protrusion 2i af on its upper surface, a hole 21b is opened in the protrusion 2i af, and there is a 45mm inside for optical path conversion.
° A mirror 22 is attached. Also, carriage 2
The protruding portion 22a of the objective lens holder 17 and the cylindrical portion 17a of the objective lens holder 17 are slidably engaged only in the vertical direction in the figure, and are prevented from rotating by means of a hinge 23. Further, the carrying tip 21 supports the optical disc 2 by a pair of guide shafts 25a, 25b via sliding bearings 24a, 24bf provided at both ends thereof.
6 in the radial direction (transverse track direction). Further, as described above, the objective lens holder 17 engaged with the carriage 2 is connected to the magnetic gap 76a of the pair of fixed magnetic circuits 12m and 12b.

It is configured to be movable within 16b.

The parallel light beam emitted from the optical system 1 passes through the hole 17b of the objective lens holder 17 and the hole 2 of the carrier horn 2.
1b, is reflected at a right angle by the 45° mirror 22,
The light is focused onto the recording surface of the optical disc 26 by the objective lens 2o. On the other hand, the reflected light from the optical disk 26 returns to the optical system J through the objective lens 2o and the 45° mirror 22, where a focus/track error and a signal are detected.

When a focus error is detected in the optical system 1, a current flows to the focus control coil 18 from a control circuit (not shown) based on this focus error signal, and the current flowing to the focus control coil 18 and the magnetism of each magnetic circuit 12a, 12b are Gap 16a.

The objective lens holder 17 moves up and down along the protruding portion 21a of the carriage 2 due to the force exerted by the action of the magnetic field within J6b. That is, when the focus control coil 18 is energized in the direction of arrow a, the objective lens holder 17
moves upward, and when energized in the direction of the arrow, the objective lens holder 17 moves downward. In this manner, by controlling the direction of energization of the focus control coil 18, and furthermore the value or time of energization, the objective lens 20 moves closer to or further away from the optical disk 26, and a predetermined focus control is performed.

On the other hand, when a tracking error is detected, a current flows in the same direction to the track control coils J9a and 19b from a control circuit (not shown) based on the trunk error signal, and the track control coil 19a.

The objective lens holder 17 is moved along the gear ridge 21f and the corresponding guide shafts 25th and 25b under the action of the current flowing through the magnetic circuit 19b and the magnetic field within the magnetic gear soles 16a and 16b of each magnetic circuit 12a and 12b.

That is, when the trunk control coils 19a and 19b are energized in the direction of arrow C, the objective lens holder 17 and the carriage 2 move in the direction of arrow e, and when the trunk control coils 19a and 19b are energized in the direction of arrow d, the objective lens holder 17 and the carriage 2 move. moves in the downward direction of the arrow. In this way, the objective lens 20 is connected to the optical disc 20 with the 45° mirror 22 by controlling the current direction, current value, and time for the track control coils J9a and J9b.
is moved in the radial direction, and predetermined track control is performed.

Also, access control is performed by the track control coil 19a from the control circuit based on the difference between the designated position and the current position.
, 19b, the track control coils 19a, 1
9b and the magnetic fields in the magnetic gaps 16a and 16b of each magnetic circuit J2a and 12b, the objective lens 20 is rotated at 45° as in the case of trunk control.
This is done by moving the optical disc 26 along with the mirror 22 in the radial direction. These position detecting means may be by counting the number of tracks crossed, or by using an external scale.

The above-mentioned focus control and trunk control are performed simultaneously and in a complex manner as necessary, but when performing access control, the trunk control is turned off and turned on again after the objective lens has moved by a desired amount.

Next, a perspective view of essential parts of a second embodiment of the present invention (not shown in FIG. 6) is shown. In the second embodiment shown in FIG.
Components that are the same as those in the embodiment will be designated by the same numbers and descriptions thereof will be omitted. The difference between this second embodiment and the first embodiment described above is the way the coil is wound on the objective lens holder 17. In this second embodiment, the objective lens holder 1 is used instead of the focus control coil 18 and track control coils 19a and 19b shown in FIG.
The first coil 27 is inclined at approximately 45 degrees with respect to the optical axis on the side surface of No.
A second coil 28 inclined at 5° and substantially orthogonal to the first coil 27 described above is wound on the objective lens holder 17.

Next, focus control based on the energization direction of the first coil 22 and the second coil 28 as seen from one side surface X of the objective lens holder 17 will be described using FIGS. 7A and 7B.

FIG. 7 (al is the case where the first coil 27 is energized in the direction of the arrow g and the second coil 28 is energized in the i direction; these energizations cause the first coil 27 to have a kinetic force 'l +
A motion force f2 is generated in each of the second coils 28, and the resultant force F causes the objective lens holder 17 to move in two directions. Similarly, as shown in Fig. 7 (bl), the first coil 2
By energizing coil 7 in the direction of arrow J and energizing second coil 28 in the direction of arrow J, a composite force -F is generated, and objective lens holder 17 moves downward. In this way, a predetermined focus control is performed by controlling the direction of energization to each coil 27, 28, as well as the value or time of energization.

Figure 8 (al, (bl) shows the case where track control or access control is performed. In Figure 8 (a), the first coil 27 is energized in the direction of arrow g, and the second coil 27 is energized in the direction of arrow g.
This is the case when the coil 28 is energized in the direction of arrow J, and as a result of these energizations, a kinetic force f1' is generated in the first coil 27, a kinetic force -f2' is generated in the second coil 28, and the resultant force of these is F' causes the objective lens holder 17 to move in the direction of the arrow in FIG. 6 together with the lever 2. Similarly, as shown in FIG. 8(b), by energizing the first coil 22 in the direction of the arrow and the second coil 28 in the direction of the arrow 1, a resultant force -F' is generated and the objective lens The holder 12 moves in the direction of the arrow in FIG. 6 together with the handle 2. In this way, predetermined track control or access control is performed by controlling the direction of energization of each coil 27, 28, and furthermore, the value or time of energization.

In the first and second embodiments described above, the case where the first coil and the second coil form a substantially right angle to each other in the magnetic gap has been described. Of course, the present invention can also be implemented in the case where a predetermined angle is formed.

Further, in the first embodiment and the second embodiment, the magnetic circuits are arranged as a pair on both sides of the magnetic circuit member, but if high-speed operation is not particularly required, either one of the magnetic circuits may be arranged. It is also possible to have only one magnetic circuit around the entire circumference.

(Effects of the Invention) As described above in detail, the optical head of the present invention has the following features:
The magnetic circuit for focus control and the magnetic circuit for track access control (radial drive) are shared and can be fixed outside the movable part, which significantly reduces the mass of the movable part and enables high-speed access. , and high-speed followability of trunk control can also be ensured.

Furthermore, since the optical head of the present invention has a configuration in which the objective lens is directly driven, the objective lens does not vibrate even during high-speed access, making it possible to accurately search for a desired track.

Furthermore, when the optical head of the present invention drives the objective lens in the track access (radial) direction, the objective lens moves together with the 45° mirror, so the optical axis of the laser beam always passes through the center of the objective lens. Therefore, the reflected optical axis from the disk does not move and track offset does not occur, and a stable read and reproduced signal can be obtained at any time.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the main parts of the first embodiment of the present invention, FIG. 2 is a side view of the main parts of a conventional optical head, FIG. 3 is a front view of the main parts of a conventional optical head, and FIG. 4 is a front view of the main parts of a conventional optical head. An explanatory diagram showing the movement of the optical axis of reflection from the disk in a conventional optical head, FIG. 5 is a sectional view taken along line 1--2 in FIG. 1, and FIG. 6 is a perspective view of the main part of the second embodiment of the present invention. Figure 7 (al, (b) is the second
FIG. 8 (a) is an explanatory diagram of focus control in the embodiment of
), (b) is an explanatory diagram of track control or access control in the second embodiment. 1 No. Optical system, 12a, 12b... Magnetic circuit, 1
3 a, 13 b --- magnet, J4a, J4b, J
5a, J5b... Yoke member, 16a, 16b...
Magnetic gap, 17... Objective lens holder, 77a
...Cylindrical portion, J7b...hole, 18...focus control coil, J9a, 19b...track control coil, 2o...objective lens, 2no...carriage,
21m...Cylindrical protrusion, 22...Mirror, 23.
...Bin, 24a...Sliding bearing, 25a, 25b
...Guide shaft, 26...Optical disc, 27
...first coil, 28...second coil. Puku-kasu control V False explanation 2 7th plan q To "F/7 morning 7) l! 1 Thj year 77 pi Su] Wholesale 1 (
My sister's begging Akido Figure 8 Procedural amendment (voluntary) 4o. 60-father-in-law/11B

Claims (4)

[Claims] (1) An optical head of an optical disk device that reproduces or records information on an optical disk includes a fixed light source and an optical path changing means for changing the optical path of the light beam from the light source and the reflected light from the optical disk. a carriage mounted thereon; a guide member that slidably supports the carriage in the radial direction of the optical disk; and a guide member fixedly arranged in parallel to the guide member,
a magnetic circuit member comprising a magnet and a yoke member and having a magnetic gap between the magnet and the yoke member; and a magnetic circuit member that is engaged with the carriage so as to be slidable in a direction substantially perpendicular to the surface of the optical disk. an objective lens holder that mounts an objective lens disposed between the optical disk and the optical path converting means; and an objective lens holder that is attached to the objective lens holder and that penetrates the magnetic gap of the magnetic circuit member. What is claimed is: 1. An optical head comprising: a first coil and a second coil arranged as shown in FIG. (2) The light beam from the light source is a parallel light beam projected parallel to the guide member, and the optical path converting means is a mirror surface having a mirror surface forming an angle of approximately 45° with respect to the optical disc surface. An optical head according to claim 1, characterized in that: (3) The first coil and the second coil are arranged at substantially right angles to each other in the magnetic gap,
Or the optical head according to item 2. (4) The optical head according to any one of claims 1 to 3, wherein the magnetic circuit members are arranged as a pair on both sides of the objective lens holder.