JPH031752B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording/reproducing apparatus for recording information at high density on an information recording carrier such as a disk, or for reproducing information from an information recording carrier recorded at high density.

When recording information at high density on a disc-shaped information recording carrier that does not have a guide groove, or when reproducing this information, a position control system is required to precisely control the position of the recording/reproducing head that records or reproduces the information. Generally necessary. In such a recording/reproducing device, in order to perform position control, it is necessary to calculate the relative positional error between the information track on which the information to be reproduced is recorded as a time-series signal and the recording/reproducing head that should follow the information track. a positional error detecting means for detecting the positional error; a driving means for driving the entire recording/reproducing head or a part thereof as a movable body in order to displace the relative position of the recording/reproducing head with respect to the information track; In general, a control circuit for operating the driving means to cancel the positional error in accordance with the positional error signal thus obtained, and a holding means for holding the movable body in a predetermined posture are generally required. The above-mentioned recording/reproducing head is a part that writes information by directly applying a state change to the information recording carrier, or reads information by directly detecting a state change of the information recording carrier,
For example, in the case of magnetic recording and reproducing, there is a magnetic head, in the case of optical recording and reproducing, the optical head performs recording and reproducing using a light spot, and in the case of capacitive type, the static head reads information with a stylus. Each capacitive head corresponds to this.

In the control system configured as described above, in order to stabilize the control operation, it is extremely important to have good characteristics of the holding means.

Hitherto, as the above-mentioned holding means, a sliding guide or support by an elastic body has often been used. However, the sliding type guide has the disadvantage that it wears out after long-term use, and also has the disadvantage that the movable body is susceptible to undesired displacement due to minute gaps.

On the other hand, when an elastic body is used as the holding means, rubber or a plate-shaped spring is generally used as the elastic body. An advantage of using rubber as the elastic body is that the spring itself has less resonance and the control system is less likely to oscillate. However, since rubber generally has poor temperature characteristics and generally has a small elastic modulus, it has the disadvantage that it is difficult to increase the suppressing force against displacement of a movable body in an unfavorable direction due to shape anisotropy. Ta. On the other hand, a plate-shaped spring made of a material with a high elastic modulus has the advantage that it has a large force that suppresses the displacement of the movable body in an unfavorable direction, and that it is easy to maintain the posture of the movable body in a predetermined state. However, on the other hand, it has the disadvantage that the control system tends to become unstable due to noticeable resonance of the spring itself.

FIG. 1 shows a schematic configuration of an actuator for focus control of an optical recording/reproducing apparatus as a conventional example of position control of a recording/reproducing head of a disk recording/reproducing apparatus. Focus control is to control the position of the information recording carrier in a direction perpendicular to the information recording surface. This conventional example will be explained below. The light beam 1 is focused by a focusing lens 2 and forms a light spot 8 on an information track 7 on a disc-shaped information record carrier 6. A coil 5 is coupled to the focusing lens 2, and the coil 5 is inserted into a gap of a magnetic circuit constituted by a magnetic yoke 3 and a permanent magnet 4. Therefore, when current flows through the coil 5, an electromagnetic force is generated, and the focusing lens 2 is driven in the vertical direction in the figure. That is, magnetic yoke 3, permanent magnet 4
The coil 5 constitutes a driving means. At this time, the focusing lens 2 is connected to two spiral plate springs 9.
Since the upper and lower ends are held by the springs a and 9b (hereinafter simply referred to as springs 9a and 9b, respectively), the optical axis is displaced in parallel without being tilted. When the information recording carrier 6 moves up and down and a vertical position error occurs, it is detected as a focus error of the optical spot 8, and the control system is configured by feeding back the focus error and driving the focusing lens 2. be done. The springs 9a and 9b are generally made of a metal spring material such as phosphor bronze.

FIG. 2 shows the transmission characteristics of an actuator consisting of a conventional holding means in which the spring is made of phosphor bronze with a thickness of 50 μm and the driving means. At this time, the outer diameter of the spring is 20 mm and the inner diameter is 6.5 mm. As shown in the figure, the resonance of the spring itself causes disturbances in the amplitude characteristics at frequencies above 1KHz, and also causes a delay in the phase. For this reason, when the gain intersection frequency of the control system is set to 700 Hz or more, oscillation is likely to occur, resulting in unstable operation.

As a result of many experiments, we have found that by using polyimide film as the spring material, the resonance of the spring itself can be extremely reduced, the temperature characteristics are good, and the posture of the movable body can be maintained sufficiently. discovered. Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 3 shows a conceptual diagram of the main parts of the first embodiment of the present invention. As in the case of FIG. 1, this embodiment relates to position control in the optical axis direction of a focusing lens of an optical recording/reproducing apparatus, that is, focus control. The substantially parallel light beam 10 is focused by a focusing lens 11 onto the information surface of the information record carrier 15 to form a light spot. The reflected light from the information recording carrier 15 is condensed by the focusing lens 11 and becomes a parallel reflected light beam again. The reflected light beam is separated from the light beam 10 by a beam splitter 16 and is incident on a focus error detector 12 . The focus error detector 12 detects the focus error of the light spot and outputs a focus error signal. The configuration of the focus error detector 12 is not particularly limited, but for example, one that utilizes astigmatism (for example, see Japanese Patent Application Laid-Open No. 53-39123), or one in which the intensity distribution of the reflected light beam is relative to the plane containing the optical axis. It is possible to use a method using the Foucault method (for example, see Japanese Unexamined Patent Application Publication No. 53-28404), which makes it asymmetric. The focus error detector 12 constitutes tracking error detection means.
The control circuit 13 includes the focus error detector 12
The focus error signal obtained is amplified, and further phase compensation is performed, and an output signal is supplied to the actuator 14. The actuator 14 controls the focusing lens 11 by the output signal of the control circuit 13.
is driven in the vertical direction in the figure so as to cancel out the focus error. A focus control system is configured by the closed loop as described above. In this figure, the actuator 14 is conceptually shown juxtaposed with the focusing lens 11, but in reality, the actuator and the focusing lens 11 have the same configuration as in FIG. That is, the actuator 14 is composed of a circular electrodynamic drive means and a holding means made of a spiral spring material.

In this example, a polyimide film with a thickness of 125 μm was used as the spring material. As a result, the transfer characteristics of the actuator were significantly improved. FIG. 4 shows the transfer characteristics of the actuator of this embodiment. As shown in the figure, 1KHz
Since the resonance of the actuator 14 in the above is extremely small, stable control can be performed even when the gain intersection frequency of the focus control system is set to 700Hz or higher, and the control gain is stable at 60dB or higher for frequencies below 30Hz. I was able to secure it.

FIG. 5 is an exploded perspective view showing a specific structural example of an actuator portion that can be used in the present invention. This example also relates to position control of an optical recording/reproducing device. The focusing lens 21 is held by a holding means consisting of two springs 22a and 22b, and its posture is maintained. Both ends A and A' of the springs 22a and 22b are fixed ends. The focusing lens 21 is driven in a direction perpendicular to the optical axis by a first driving means consisting of coils 23a, 23b and magnetic circuits 24a, 24b.
5 and magnetic circuits 26a and 26b in the optical axis direction. The springs 22a and 22b have a detailed structure as shown in FIG. 6a. That is, the two polyimide films 31a and 31b are fixed in parallel to each other by molding their ends and central parts into resin. Further, the polyimide films 31a and 31b have holes in their molded parts, which solves the drawback that polyimide generally has poor adhesive properties and prevents the polyimide films from falling out. . As shown in Fig. 6 b, c, and d, the molded part of the polyimide film (the shaded part in the figure)
A similar effect can also be obtained by providing a protrusion or a cutout in place of the hole. Also,
A printed wiring 32 is formed on the polyimide film 31a, and the printed wiring 3
2 through the coils 23a, 23b or 2
5 can be powered. Thereby, there is no need to connect the movable coil and the fixed part with a floating wire, and disconnection accidents due to vibration can be extremely reduced. The overall configuration of the control system in this example is the third
It is basically the same as the figure, and includes a first control loop including a tracking error detector as a tracking error detection means for detecting a tracking error that is a position error in the direction perpendicular to the optical axis, and 2 of the second control loop including a focus error detector that detects a focus error that is a position error.
It has two control loops.

FIG. 7 shows the transfer characteristics of the actuator of this example. FIG. 7a shows a direction perpendicular to the optical axis of the actuator (driving direction of the first driving means);
FIG. 7b shows the transmission characteristics in the optical axis direction (the driving direction of the second driving means).
As is clear from the figure, it is possible to perform stable control by setting the gain intersection frequency of both the first control loop and the second control loop to 1 KHz or more.

It should be noted that the polyimide film molding method and printed wiring formation described above are not limited to the spring shape of this example, and can generally be implemented with any spring shape.

As explained above, the present invention satisfies the conditions required by a device that records or reproduces high-density information, such as a video disc player. The intersection frequency generally needs to be 700Hz or higher.

) Movable bodies to be driven by position control are generally lightweight.

) It is necessary to maintain a predetermined posture as a movable body through position control.

In order to satisfy this unique condition, we have discovered that a holding means using a polyimide film is extremely effective, and as a result, we have made it possible to realize an information processing device with stable position control operations.

In the above description, an optical recording/reproducing apparatus was taken as an example, but it is clear that the present invention is also effective in information recording/reproducing apparatuses of other types. For example, a polyimide film can be used as a holding means for a magnetic head in a magnetic recording and reproducing apparatus, and as a holding means for a stylus in a capacitance type reproducing apparatus.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway perspective view of a conventional actuator, Fig. 2 is a transfer characteristic diagram of a conventional actuator, Fig. 3 is a conceptual diagram of main parts of an embodiment of the present invention, and Fig. 4 is a diagram of the same embodiment. Actuator transfer characteristic diagram,
FIG. 5 is an exploded perspective view showing a specific example of an actuator that can be used in the present invention, FIGS. FIG. 3 is a transfer characteristic diagram of the actuator of the embodiment. 23a, 23b, 25...Coil, 22a, 2
2b... Spring, 12... Focus error detector,
13... Control circuit, 14... Actuator, 1
5... Information record carrier, 24a, 24b, 26a,
26b...Magnetic circuit.

Claims (1)

[Scope of Claims] 1. A recording/reproducing head for recording information on or reading information from an information track on an information recording carrier; a position error detection means for detecting a relative positional error of the recording/reproducing head with respect to the information track; A drive means for displacing the entire recording/reproducing head or a part thereof as a movable body, and control for operating the drive means in a direction in which the position error is canceled in accordance with a position error signal obtained by the position error detection means. A position control loop is configured including a circuit and a holding means for holding the movable body in a predetermined posture, and the gain intersection frequency of this position control loop is 700 Hz or more, and the holding means uses a polyimide film as a spring material. A recording/reproducing device characterized in that it is used as a. 2. The recording/reproducing device according to claim 1, wherein a printed wiring is formed on the spring material, and power is supplied to a drive coil included in the movable body via the printed wiring. . 3. The spring material is fixed by molding its end in resin, and the molded end has at least one of a hole, a protrusion, and a cutout. The recording/reproducing device according to item 1.