JPS6258431A - Optical pickup device - Google Patents

Abstract

PURPOSE:To always attain a stable characteristic in a tracking direction without the influence of the position in the focusing direction of a condenser lens by constituting a device so that the center of the magnetic flux generated in the second coil by a magnetic circuit acts upon a part nearer to the condenser lens than the center of gravity of a moving part in the movable range where the movable part is moved in the direction approximately vertical to a carrier face. CONSTITUTION:When a movable part 54 is placed in the about center of the moving range in a focusing direction, the center B of the magnetic flux due to a magnetic circuit 60 is a length (l) nearer to a condenser lens 50 than the center G of gravity of the movable part 54 and distances from the center G of gravity of the movable part 54 to upper and lower flat springs 58 are equal to (m) together, and therefore, the movable part 54 is shaked in the tracking direction near a resonance point f2 in the tracking direction of flat springs 58. Since the center of the propulsion generated in a tracking coil 53 coincides with the center B of the magnetic flux and is nearer to the condenser lens 50 than the center G of gravity of the moving part 54, the condenser lens 50 responds normally to the input signal to the tracking coil 53.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical disc device for recording, reproducing, or erasing information by condensing a laser beam onto a rotating disc-shaped record carrier using a condensing lens. -Relates to pickup devices.

Conventional technology In recent years, optical disk devices have been rapidly becoming popular.
There is a need to improve the performance of optical pickups, which are one of the elemental technologies that determine the performance of this type of device.

Hereinafter, a conventional optical pick-up tube will be explained with reference to the drawings. In FIG. 4 (&), 9 is a condenser lens that focuses the laser beam onto the disk. 10 is a coil that drives the condenser lens 9 in a direction substantially perpendicular to the disk surface (hereinafter referred to as the focus coil 10), and 11 is a coil that drives the condenser lens 9 in the radial direction of the disk (hereinafter referred to as the tracking coil 11). It is. The condenser lens 9, focus coil 10, and tracking coil 11 are integrally fixed by adhesive or other means to form a movable part 30.

In FIG. 4(b), reference numeral 12 denotes a transfer table, and a mirror 13 having a reflective surface inclined at 45 degrees with respect to the incident light is integrally formed in the center thereof. The substantially parallel laser light incident in the direction of the arrow passes through the circular opening 14 in the transfer table 12 and is reflected upward by the mirror 13. 16 is a metal plate spring, rubber,
It is a flexible support member (hereinafter simply referred to as the leaf spring 15) made of resin or a combination thereof, and one end of the support member is fixed to the transfer table 12 by adhesive or other means.

Reference numeral 16 is rotatably supported by a bearing on the transfer table 12. The leaf spring 16 is fixed to the upper end A1 of the movable part 30 by a fixed part λ'1, and fixed to the lower end part 2 of the movable part 30 by a fixed part A/2. As a result, the movable part 30 is supported so as to be movable with respect to the transfer table 12 in a direction substantially perpendicular to the disk surface (vertical direction in the drawing).

In FIG. 4(0), the magnetic circuit includes magnets 18. It consists of a yoke 19, and a focus coil 1o and a tracking coil 11 are inserted into the gap B'I+B2. The outer diameter of the bearing 16 comes into contact with the slope of the rail 17, and as the bearing 16 rolls on the rail 17, the transfer table 12 slides. The opening 20 is for passing substantially parallel incident light to the disk and reflected light from the disk.

Next, the operation of the conventional device will be explained.

The magnetic circuit shown in FIG. 4(C) is common to the focus coil 1o and the tracking coil 11, and has a magnetic flux in a direction perpendicular to the magnetic gap B++ B2.

Focus coil 1 within magnetic gaps B, B2
Since the effective current flow direction for generating electromagnetic force at zero is the direction of the arrow 31, the movable portion 3° moves in a direction substantially perpendicular to the disk surface (vertical direction in the drawing). In the 7-orcus direction, since the leaf spring 16 is sufficiently soft compared to the rigidity of the transfer table 12, only the movable part 30 moves while being supported by the leaf spring 15. The leaf spring 16 has damping characteristics, and the focus direction has a low frequency f.
It has a resonance point near 1°, that is, 3Q to 6oHz, and the frequency characteristics in the focus direction have general characteristics as shown in FIG. 6 (al).

On the other hand, since the effective current flow direction for generating electromagnetic force in the tiger knocking coil 11 is the vertical direction in the drawing, the movable portion 3o moves in the radial direction of the disk (arrow 32).

The frequency characteristics in the tracking and access directions have characteristics that are slightly different from general characteristics.

That is, when electromagnetic force is generated in the tracking coil 11,
This electromagnetic force is applied to the condensing lens 9. It is transmitted to the transfer table 12 via the leaf spring 16. Leaf spring 161d) racking, access direction with damping characteristics, 1~2KH2
It has a relatively high resonant frequency f2. Therefore, in a region where the input signal frequency to the tracking coil 11 is sufficiently lower than f2, the movable part 30 including the condenser lens 9 and the transfer stage 12 move together, but the input signal frequency is lower than r2. In a sufficiently high region, the plate spring 15 is essentially absent, and the transfer table 12 does not move, and only the movable part 3o including the condenser lens 9 moves. is a constant proportional to the amplitude of the input voltage.

By the way, the mass of the movable part in the tracking and access directions changes depending on the frequency as described above.

In other words, at a frequency lower than f2, the mass of the movable part 30'
1+the mass M20 of the transfer table 12 is the sum of υ, and at a frequency higher than r2, only the mass M1 of the movable part 3o becomes. Therefore, as shown in FIG. 5(b), the amplitude X becomes TE/(M1+M2), f2(!), and /M1, f2 at a frequency higher than f2, as shown in FIG. 5(b).

Therefore, ideally, the characteristics in the tracking and access directions are such that the phase is raised at r2, and the characteristics are similar to those obtained when the phase is compensated by a circuit.

Problems to be Solved by the Invention However, with the configuration of the magnetic circuit and coil as described above, there is no problem in the focus direction, but there are problems in the tracking and access directions.

The operation of the above-mentioned conventional device in the tracking and access directions will be explained assuming various cases of actual use. FIG. 6 is a schematic cross-sectional view of the conventional device described above. FIG. 6 shows a case where the conventional device operates ideally, and its characteristics are as shown in FIG. 5(b).

In other words, as shown in FIG. 6, the gap B1+ of the magnetic circuit in which the height of the magnet 18 and the yoke 19 are made equal.
When the center B in the height direction of B2 and the center of gravity G of the movable part 30 are at the same position, the condenser lens 9 above the movable part 30
and the lower A2 normally respond to the input signal to the tracking coil 11, and the condenser lens 9 and the coil 2 move in parallel in the direction perpendicular to the plane of the paper in the same phase. Therefore, the frequency characteristics of the condensing lens 9 are as shown in FIG. 6(b).

However, in actual use, since the movable part 30 also moves in the focus direction, the gap B1 of the magnetic circuit. B
The center B of 2 and the center of gravity G of the movable part 3o do not necessarily match in the height direction.

FIG. 7 (&l, (b) is a further schematic representation of FIG. 6, and shows a state in which the center B of the gap B1+B2 and the center of gravity G of the movable part 30 do not coincide. 30 moves upward in the focusing direction.At this time, since the heights of the gaps B1 and B2 of the magnetic circuit do not change, the center of gravity G of the movable part 30 and the center of the gaps B, B, B2 naturally change. At this time, since the center of magnetic force B by the magnetic circuit acts on the movable part 30 below the center of gravity G, the movable part 30 is moved to the resonance point f2 of the leaf spring 15 in the traction and shaking direction. The center of gravity G of the movable part 3o will make a rocking motion as shown by the arrow in the figure in the vicinity, and the center of gravity G of the movable part 3o will normally respond to the input signal to the tiger king coil 11.
It is the lower part of M2. Therefore, the movement of the condensing lens 9, which requires frequency characteristics, is originally controlled by the tracking coil 1.
The phase will be reversed with respect to the input signal to 1. FIG. 8(a) shows the phase characteristics of the condensing lens in this state. Naturally, when this happens, it becomes impossible to follow the eccentricity of the track on the condensing lens 91i disk, making it impossible to record and reproduce information.

On the other hand, as shown in FIG. 7(b), when the movable part 30 moves downward in the focus direction, it is obvious that the center of gravity G of the movable part 3o and the center of the gap B1 + 82 B will be off.

At this time, since the center of magnetic force B due to the magnetic circuit acts on the movable part 30 above the center of gravity, the movable part 30
0 is the resonance point f of the leaf spring 15 in the tracking direction
At around 2, there will be a rocking motion as shown by the arrow in the figure.

However, at this time, the difference from the state shown in FIG. 7(a) is that the center of magnetic force B due to the magnetic circuit is acting above the center of gravity G of the movable part 30, so that the input to the tracking coil °11 is It is the condenser lens 9 above the center of gravity G of the movable part 3o that responds normally to the signal. Therefore, the phase characteristic of the condensing lens 9 becomes as shown in FIG. 8(b), and recording and reproduction on the disk can be performed normally.

As explained above, in the conventional apparatus, depending on the position of the movable part 30 including the condenser lens 9 in the focus direction, the condenser lens 9 does not respond normally to the eccentricity of the disk, and In some cases, it became impossible to record and reproduce information.

In view of the above-mentioned problems, the present invention provides an optical pickup that can always obtain stable characteristics in the tracking direction without being affected by the position of the condenser lens in the focus direction.

Means for Solving the Problems In order to solve the above problems, the optical pickup of the present invention includes a transfer table movable in the radial direction of a disk-shaped record carrier, and a light source that directs substantially parallel light onto the surface of the carrier. A condensing lens that condenses light, and a first coil that drives the condensing lens in a direction substantially perpendicular to the carrier surface.

a second coil that drives the condensing lens in the radial direction of the carrier; a movable part that integrally fixes the condensing lens, the first coil, and the second coil; At the lower end, the other end is fixed to the transfer table, and there are two flexible support members, upper and lower, that support the movable part in a state that it can move in a direction approximately perpendicular to the carrier surface, and a magnetic field that generates thrust in this coil. A circuit is provided, and the center generated in the second coil by this magnetic circuit acts closer to the condenser lens than the center of gravity of the movable part within the movable range of the movable part in a direction substantially perpendicular to the carrier surface. It has various configurations.

Operation As described above, the present invention is directed to a position where the center of the thrust of the tracking coil that drives the movable part including the condensing lens in the radial direction of the disc-shaped record carrier is located in the direction perpendicular to the surface of the disc-shaped record carrier of the movable part. By configuring the structure so that the center of gravity of the movable part always acts toward the condensing lens without being affected by It is designed to respond normally to input signals to the coil.

EXAMPLE Hereinafter, an optical photoconverter according to an example of the present invention will be explained with reference to the drawings.

FIGS. 1(2L) and 1(b) are exploded perspective views of an optical pickup in an embodiment of the present invention. In the figure, 50 is a condensing lens that focuses the laser beam onto the disk 51. 52 is a coil (hereinafter referred to as focus coil 52) that drives the condenser lens 50 in a direction substantially perpendicular to the surface of the disk 51, and 53 is a coil (hereinafter referred to as tracking coil) that drives the condenser lens 5° in the radial direction of the disk 51. 53). The condensing lens 5o, the focusing coil 62, and the tracking coil 53 are integrally fixed by adhesive or other means to form a movable part 54.

Reference numeral 55 denotes a transfer table, and a mirror 56 having a reflective surface inclined at 45 degrees with respect to the incident light is integrally formed in the center thereof. A substantially parallel laser beam incident from the arrow passes through a circular opening 57 in the transfer table 55 and is reflected upward by a mirror 56. 58 is a metal plate spring.

It is a flexible support member (hereinafter referred to as a leaf spring 58) made of rubber, resin, or a combination thereof, and one end thereof is fixed to the transfer table 55 by means of adhesive or the like. 5
Reference numeral 9 denotes a bearing, which is rotatably supported by the transfer table 55. The leaf spring 58 is fixed to the upper end part 1 of the movable part 64 by a fixed part A'1, and fixed to the lower end part 2 of the movable part 54 by a fixed part A'2. As a result, the movable part 54 moves to the transfer table 5.
5 so as to be movable in a direction substantially perpendicular to the disk surface 51 (up and down direction in the drawing). In addition, the upper and lower two leaf springs 5
The spring constants of 8 are set equal. In addition, the movable part 5
Fixed part AI+ A2 of the upper and lower leaf springs 58 from the center of gravity of 4
The distances are also set to be approximately equal.

FIG. 1(C) is a sectional view of a main part of an assembled optical pickup according to an embodiment of the present invention. In the figure, the magnetic circuit 6o includes magnets 61. It consists of a yoke 62, and a focus coil 52° and a tracking coil 53 are inserted into the gap B1+B2. In this magnetic circuit 60,
The center position of the magnet 61 and yoke 62 in the height direction is set to 4.
The center position of the magnet 61 is set closer to the condenser lens 5o than that of the yoke.

In this embodiment, the set amount 4 is set to be slightly larger than half of the maximum movement amount of the movable portion 54 in the focus direction.

The outer diameter of a bearing 69 is in contact with the slope of the rail 63, and as the bearing 59 rolls on the rail 63, the transfer table 55 slides in the radial direction of the disk 51.

The operation of the optical pickup of the present invention configured as above will be explained.

In FIG. 1, the magnetic circuit 60 is connected to the focus coil 52.
．． It is common to the tracking coil 63 and has a magnetic flux in a direction perpendicular to the magnetic gap B1+ 82. Magnetic gap B1. Since the effective current flow direction in B2 for generating electromagnetic force in the focus coil 52 is the direction of the arrow 64, the movable portion 54 moves in a direction substantially perpendicular to the surface of the disk 51 (in the vertical direction in the drawing). In the focus direction, since the plate spring 58 is sufficiently soft compared to the rigidity of the transfer table 55, only the movable part 54 moves while being supported by the plate spring 58. The leaf spring 58 has a damping characteristic and has a pitch of 30 to 60H2 in the focus direction.
The movable portion 54 has a resonance point at a low frequency f1, and the frequency characteristics of the movable portion 54 in the focus direction have general characteristics as shown in FIG. 5(a), as explained in the conventional example.

On the other hand, since the effective current flow direction for generating electromagnetic force in the tracking coil 63 is the vertical direction in the drawing, the movable portion 54 moves in the radial direction of the disk 61 (arrow 64). This movement in the tracking and access directions is slightly different from general characteristics. As explained in the operation of the conventional example, the mass of the movable part 54 is M1 + the mass of the transfer table 55 is '
2+The resonant frequency of the leaf spring 58 in the tracking direction is f2
+The input signal frequency to the tracking coil 53 is f.

When the amplitude of the condensing lens 50 of the movable part 54 is assumed to be X, the frequency characteristic of the condensing lens 5o is as shown in FIG. 5(b).

The actual usage state of the optical pickup of this embodiment configured as described above will be explained using the schematic diagram shown in FIG. 2.

FIG. 2(a) shows a state in which the movable portion 54 is in the middle of its movable range in the focus direction. At this time, the center B of the magnetic flux generated by the magnetic circuit 60 is l closer to the condenser lens 5o than the center of gravity G of the movable part 540, and the distance from the center of gravity G of the movable part 54 to the upper and lower leaf springs 58 is also equal to m. Therefore, leaf spring 5
In the vicinity of the resonance point f2 in the tracking direction of 8, the movable part 5
4 swings in the tracking direction as shown by the arrow in the figure. The center of the thrust generated in the tracking coil 53 is located at the same position as the magnetic flux center B, and is closer to the condenser lens 50 than the center of gravity G of the movable part 54, so the condenser lens 50 receives the input signal to the tracking coil 53. respond normally.

FIG. 2(b) shows the state when the movable portion 54 has moved maximum upwardly within the movable range in the focus direction. In this case as well, the center of magnetic flux B is closer to the condenser lens 50 by 41 than the center of gravity G of the movable part 54, so the center of thrust of the tracking coil 53 is closer to the condenser lens 5o than the center of gravity G of the movable part 64. , and the condensing lens 5o normally responds to the input signal to the tracking coil 53. In this case, since β1 is a small value, the movable part 6
4 moves approximately in parallel in the tracking direction as shown by the arrows in the figure.

Further, FIG. 2(C) shows a case where the movable portion 64 has moved downward to the maximum within the movable range in the focus direction. In this case, the center of gravity G of the movable part 64 is also the center of magnetic flux B.
is located closer to the condenser lens 5o by 12, so the condenser lens 50 normally responds to the input signal to the tracking coil 63.

As shown in FIG. 3, the phase characteristics of the condenser lens 50 in the tracking direction in FIGS. 2(a), (b), and (C) explained above are near the resonance point f2 of the flat spring 68 in the tracking and sinking directions. , and the characteristics are equivalent to phase compensation using a servo circuit.

In this embodiment, even when the magnetic flux center Bfl tracking coil 53 is not in operation, it is set closer to the condenser lens 50 than the center of gravity of the movable part 540, but the tracking coil 6
It goes without saying that it is sufficient to satisfy the above conditions only during operation 3.

As described above, according to this embodiment, the upper and lower two leaf springs 58
The distances from the fixed part AI+mu 2 to the center of gravity G of the movable part 540 are set to be approximately equal, and the magnetic flux center B of the magnetic circuit 60 is set to the center of gravity G of the movable part 54 (in the focus direction of the movable part 54). slightly larger than half of the maximum movement range)
Since the condenser lens 5o is set in advance to be close to the condenser lens 50, the condenser lens 5o is close to the movable part 54 in the tracking direction.
The tracking coil 53 can be moved normally in response to an input signal without being affected by the position in the focus direction of the tracking coil 53.

Effects of the Invention As described above, the present invention includes a condensing lens, a first coil that drives the condensing lens in a direction substantially perpendicular to the surface of the disk-shaped record carrier, and a condensing lens that drives the condensing lens in the radial direction of the carrier. Second to do
a movable part consisting of these condensing lenses, a first coil, and a second coil, and two upper and lower flexible support members that support this movable part so as to be movable in a direction substantially perpendicular to the carrier surface. , the center of the thrust generated in the second coil by the magnetic circuit is more concentrated than the center of gravity of the movable part within the movable range in the direction approximately perpendicular to the carrier surface of the movable part. By configuring the lens to act in a direction closer to the optical lens, the movement of the condensing lens in the radial direction of the disk-shaped carrier is caused by the second movement regardless of the position of the movable part in the direction substantially perpendicular to the carrier surface. The coil can be made to respond normally to input signals in any usage state, and can achieve good operation.

[Brief explanation of the drawing]

Figures 1 (&), (b) and (C) are an exploded perspective view and a sectional view of essential parts of an optical big amplifier device according to an embodiment of the present invention, and Figures 2 (&), (b) and (C) is its schematic diagram, Figure 3 is its custom-made diagram, and Figures 4 (a) and (b)
), (C) is an exploded perspective view of a conventional optical pickup device, FIG. 5 is its characteristic diagram, FIG. 6 is its schematic diagram, FIG. 7 is its schematic diagram, and FIG. 8 is its characteristic diagram. . 50...Condensing lens, 51...Disc, 52...Focusing coil, 53...
・Tracking coil, 64...Movable part, 55
...Transfer table, 66...Mirror, 58...
...Plate spring, 6o...Magnetic circuit, 61...
...Magnet, 62...Yoke. Name of agent: Patent attorney Toshio Nakao and one other person A1
Figure 52-1 L-/7”51-・-Union Sk No. 2 Figure 1, -1 shi〆Fig. 3 7 Oath 1 La, Z ξ J7
1-Cusco f9 IJ--Ikki-men f9--Cuzco Kuko
-1'6 - 15-m-ηb (Ne□ Kō-qb Shu 1-11 Nog 11-l No. 8 Zushouhekyo C edition) for Kungkyo (H2゜

Claims (2)

[Claims] (1) A transfer table movable in the radial direction of the disk-shaped record carrier, a condensing lens that condenses substantially parallel light from the light source onto the carrier surface, and a condensing lens that focuses the condensing lens approximately perpendicular to the carrier surface. a first coil that drives the condenser lens in a radial direction of the carrier; a second coil that drives the condenser lens in a radial direction of the carrier; and the condenser lens, the first coil, and the second coil are integrally fixed. a movable part, one end of which is fixed to the upper and lower ends of the movable part and the other end to the transfer table, supporting the movable part in a state that it can move in a direction substantially perpendicular to the carrier surface. It includes two upper and lower flexible support members and a magnetic circuit that generates thrust in the coil, and the center of the thrust generated in the second coil by the magnetic circuit is directed in a direction substantially perpendicular to the carrier surface of the movable part. An optical pickup device characterized in that within a movable range, the optical pickup device is configured to act closer to the condenser lens than the center of gravity of the movable part. (2) When the second coil operates, the center of thrust by the second coil is closer to the condenser lens than the center of gravity of the movable part.
The optical pickup device described in Section 1.