JPH0442733B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a reproducing device that optically reads recorded information from a video disc, a PCM disc, etc., and particularly relates to a reproducing device that optically reads recorded information from a video disc, a PCM disc, etc. This relates to a drive mechanism.

[Conventional technology]

A conventional device of this type is shown in FIG. In the figure, 1 is a laser light source such as He-Ne, 2 is a laser beam, 3 is a diffusion lens, 4 is a half mirror, 5 is a track tracking control mirror device, 6 is a focus control lens device, 7 is a photodetector, and 8 is a disk, 9 is a motor, 10 is a reproduction signal processing circuit, 13
12 is a track tracking control circuit; 12 is a focus control circuit;
13 is pit.

Next, the operation will be explained. After the laser light 2 emitted from the laser light source 1 is diffused by the diffusion lens 3,
After passing through a half mirror 4 and a track tracking control mirror device 5, a light spot (optical needle) on the order of microns is formed on the disk 8 by a condensing lens housed in a focus control lens device 6. On the other hand, disk 8
As shown in Figure 6, there is a pit 1 on the micron order.
3 was recorded as a spiral or concentric track. A signal is optically reproduced by maintaining the light beam 2 condensed on the micron order in an appropriate positional relationship on this micron order pit 13.

FIG. 7 is a diagram for explaining the positional relationship between the light spot and the disk. As shown in this diagram, the light beam 2 is condensed and then spread out again. Under such conditions, it is obvious that in order to perform the most efficient reproduction, it is better to reproduce near the area where the light is most concentrated. However, when the disk 8 is rotated in the direction of arrow C in FIG. 5, the recording surface of the disk 8 is rotated in the directions a, b, c in FIG.
will change as shown in. Similarly, in the relationship between the light spot and the recording track, positional deviations occur as shown in FIGS. 7b, e, and f due to meandering of the recording track, eccentricity of the disk 8, etc. Therefore, in order to always perform efficient reproduction, the light beam 2 must always be in the focal direction and in the direction perpendicular to the track.
It becomes necessary for the light spot to track the pit 13.

For this reason, in the conventional apparatus, a focus control lens device 6 and a track tracking control mirror device 5 were used. These devices each move a condenser lens up and down in the direction of arrow A perpendicular to the disk 8 (see FIG. 5), and rotate the mirror of the track tracking control mirror device 5 in the direction of arrow B. Although a detailed explanation will be omitted here, the distance between the disk 8 and the condenser lens and the amount of deviation of the light spot from the track are extracted as electrical signals by the photodetector 7, and the focus control circuit 12 and track tracking control circuit 11 are input a control signal to the focus control lens device 6 and the track tracking control mirror device 5 through the
This allows for appropriate correction.

FIG. 8 is a sectional view of a main part of a conventional focus control lens device, and FIG. 9 is a conceptual diagram of a track tracking control mirror device. In FIG. 8, the yoke 16,
A coil 18 is installed in the magnetic flux formed by the magnet 17, and by passing a control current through it, the lens frame 20 supported by the spring 15 moves in the direction of arrow A. As this spring 15, an annular grooved plate spring or the like has been used. Note that 14 is a condenser lens, and 19 is a support frame fixed to the yoke 16.

Further, in FIG. 9, 21 is a mirror corresponding to the mirror of the track tracking control mirror device in FIG.
Reference numeral 24 denotes track tracking control coils, each of which is fixed to the wire spring 22. The coil 24 is installed in the magnetic flux of the magnet 23, and the coil 24
The rotary movement is performed in the direction of arrow B by supplying a control current to the rotor.

[Problem that the invention seeks to solve]

The conventional disc playback device is constructed as described above, and uses springs 15 and 22 for focus control and track tracking control. However, when a spring is used to restrict the direction of movement as in this conventional device, mechanical resonance tends to occur, which adversely affects the characteristics of the control device. Furthermore, although the actuator is operated against the elastic force of the spring, there is always a limit to the dynamic range (linearity of the relationship between displacement and force) of the spring, which poses a problem in terms of control characteristics.

Furthermore, when attempting to simplify the mechanism by using a semiconductor laser as a laser light source, there is a problem in that it is difficult to miniaturize and simplify the overall structure by applying the conventional focal position control device and track tracking control device described above. Ta.

This invention was made in view of the above-mentioned drawbacks of the conventional technology, and it is possible to simplify and downsize the device without reducing the accuracy of reading signals from the disk surface, and to improve the linearity of control. It is an object of the present invention to provide a disc playback device that can expand the control dynamic range and improve response characteristics.

[Means for solving problems]

The disc playback device according to the present invention includes a rotating body that is rotatable around a certain axis and movable along the axis, and an optical axis of the rotating body that is located at a position eccentric from the axis. a light condensing means supported in parallel; a track tracking control coil provided on the rotating body for controlling the track deviation; and a track tracking control coil provided on the rotating body separately from the track tracking control coil. A focus position control coil for controlling the focus shift; and a focus position control coil provided on a fixed part outside the axis line and facing each of the coils, together with the track tracking control coil. It is equipped with a magnet for rotating the moving body and a magnet for moving the rotating body together with the focal position control coil.

[Effect]

In this invention, control for track deviation and focus deviation is performed using one rotating body that is rotatable around a certain axis and movable along the axis. The device is smaller and simpler than a separate device, and since a spring is not used as a means for regulating the direction of movement as in the past, resonance during drive control is prevented. , linearity is improved,
And the dynamic range expands.

Furthermore, since each coil is placed on the rotating body side and each magnet on the stationary side, the weight of the rotating part is reduced and the magnetic path configuration on the magnet side is facilitated.Furthermore, each coil can be placed separately. As a result, interference between the magnetic fluxes caused by both coils is reduced, and the winding work of the coils becomes easier.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a sectional view of a main part of an embodiment of the present invention, and in the figure, the same reference numerals as in FIGS. 5 to 8 indicate the same or corresponding parts. A shaft 43 is partially supported by a slide bearing 40 provided on the yoke 16 and is movable and rotatable. The slide bearing 40 is made of a material with an extremely low coefficient of friction, such as Teflon. A support plate 44 is connected to the shaft 43 and constitutes a rotating body together with the shaft 43. 30 is a semiconductor laser light source, 31 is a collimating lens, and 35 is a condensing lens constituting a condensing means. It is attached in such a way that it is parallel to the central axis.

42 is a track tracking control coil (hereinafter referred to as a tracking coil);
2 is a shaft 43 as shown in FIGS. 2a and b.
A portion of the coil 42 is cut out, and the coil 42 is attached so as to be aligned with the central axis of the shaft 43. A focus position control coil (hereinafter referred to as focus control coil) 18 is also provided on the shaft 43 at a position apart from the tracking coil 42. Numerals 39 and 17 are magnets provided on the fixed side facing the tracking coil 42 and the focus control coil 18, respectively, and 37 is a yoke.

Next, the effects will be explained.

In the apparatus configured as described above, when a focus position control current is supplied to the focus control coil 18, the shutter 43 and the support plate 44 move in the direction of arrow A, and condensing lens 35 also moves in the direction of arrow A. The focus position is corrected. or,
When a track tracking position control current is supplied to the tracking coil 42, the shaft 43 and the support plate 4
4 rotates in the direction of arrow B, and the condenser lens 35 rotates in a direction perpendicular to the track. This is in the direction of arrow B in Fig. 3, and actually draws an arc, but the track tracking control amount is about 0.2 to 0.3 mm, and the distance between the condenser lens 35 and the central axis of the shaft 43 is several mm or more. The error can be almost ignored.

With this configuration, the focus position control and the track tracking control are realized by a device that drives one rotating body, so it is possible to achieve miniaturization, and since each of the heavy magnets mentioned above is provided on the fixed side, The weight of the rotating portion is reduced, resulting in better responsiveness, and the configuration of the magnetic path becomes easier than when each magnet is provided on the rotating side. Further, since the tracking coil 42 and the focus control coil 18 are provided separately, there is almost no interference between the magnetic fluxes of the two coils, improving each control precision and widening the dynamic range. Further, the winding work becomes easier.

In addition, since no springs are used to regulate the direction of movement, mechanical resonance is less likely to occur, and the dynamic range (linearity of force-displacement) has been dramatically improved in conjunction with the above-mentioned separate coils. becomes larger. Furthermore, the rotation and sliding of the shaft are separated in their operating directions, and as mentioned above, each coil is provided separately, so there is almost no interference between them, and all directions of shaft movement are controlled. , there is no problem as long as the influence of disturbance is within the control range.

FIG. 4 is a sectional view of another embodiment of the invention,
A semiconductor laser is used as a laser light source, and all optical systems are mounted on a support plate 44, and 45 is a self-occurring lens. Other configurations and control operations are the same as in the above embodiment.

In such an embodiment, the optical head becomes more compact and replaceable, which is preferable from a practical standpoint.

〔Effect of the invention〕

As described above, the disc playback device according to the present invention includes a rotating body that is rotatable around a predetermined axis and movable along the axis, and a rotating body that is located at a position eccentric from the axis of the rotating body. a light condensing means supported so that its optical axis is substantially parallel to the axis; a track tracking control coil provided on the rotating body for controlling the track deviation; and a track tracking control coil provided on the rotating body. a focus position control coil for controlling the focus shift, which is provided separately from the coil for controlling the focal position; A magnet for rotating the rotary body together with the track tracking control coil, and a magnet for moving the rotary body together with the focus position control coil are provided. In both cases of control and control for defocusing, it is possible to maintain a state perpendicular to the disk surface at all times, making it possible to simplify and downsize the device without reducing the accuracy of reading signals from the disk surface. This has the effect of improving the linearity of control of deviation and defocus, expanding the dynamic range of control, and improving response characteristics.

In addition, each of the above coils is provided on a rotating body, and
Since each magnet is provided on the fixed side,
The weight of the rotating part does not increase and responsiveness can be improved, and the configuration of the magnetic path is easier.Furthermore, since each coil is provided separately, interference between magnetic fluxes from both coils is reduced, improving control accuracy. This also has the effect of making the winding work easier.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the configuration of a main part of an embodiment of the present invention, and FIGS. 2a and 2b are views showing how the rotary drive coil and shaft are attached in the embodiment shown in FIG. 1. , FIG. 2a is a front view, FIG. 2b is a sectional view taken along line bb--b, FIG. 3 is a diagram showing the direction of track tracking on the disk, and FIG. 4 is a sectional view of another embodiment of the present invention. Figure 5 is a sectional view showing the configuration of the main parts of a conventional optical playback device, Figure 6 is a diagram showing the relationship between the disk and the track, and Figure 7 is the position of the condensed light beam and the pit on the disk. FIG. 8 is a sectional view of a conventional focus control lens device, and FIG. 9 is a conceptual diagram of a conventional track tracking control mirror device. 2...Laser beam, 7...Photodetector, 8...Disk, 13...Pit, 16, 37...Yoke,
17, 39... Magnet, 18... Focus control coil, 42... Tracking coil, 19...
...Support frame, 30...Semiconductor laser light source, 31...
Collimating lens, 35... Condensing lens, 40...
...Slide bearing, 43...Shaft, 44
...Support plate, 45...Self-cleanse. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1 Detecting the track deviation of the light spot with respect to the information track of the disk on which information is recorded and the focal deviation of the light spot with respect to the information recording surface of the disk, and adjusting the position of the light focusing means that forms the light spot according to the track deviation and the focus deviation of the light spot with respect to the information recording surface of the disk. The information is optically read out from the information track by the light spot irradiated from the controlled light condensing means according to the detected amount of defocus,
A rotating body that is rotatable around a predetermined axis and movable along the axis, and an optical axis supported at a position eccentric from the axis of the rotating body so that its optical axis is substantially parallel to the axis. an optical means, a track tracking control coil provided on the rotating body for controlling the track deviation, and a focal point provided on the rotating body separately from the track tracking control coil for controlling the focus deviation. a position control coil; and a magnet provided on a fixed part outside the axis of each coil and facing each coil, and for causing the track to rotate the rotating body together with the tracking control coil. and a magnet for moving the rotating body together with the focal position control coil.