JPH0413771B2 - - 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, 11
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 light beam 2 condensed on the micron order is placed on this pit 13 on the micron order.
By maintaining the proper positional relationship, the signal is optically regenerated.

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 spreads out again after being focused. 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, disk 8
When rotated in the direction of arrow C in FIG. 5, the recording surface of the disk 8 changes as shown in FIGS. become. Similarly, the relationship between the optical spot and the recording track may change due to meandering of the recording track, eccentricity of the disk 8, etc.
Misalignment occurs as shown in Figures d, e, and f. Therefore, in order to perform efficient reproduction at all times, it is necessary for the light spot of the light beam 2 to always track the pit 13 in the direction of the focal point and in the direction perpendicular to the track.

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 operating direction as in this conventional device, these mechanical resonances tend to occur, which adversely affects the characteristics of the control device. In addition, although the spring is operated against the elastic force of the spring, the dynamic range of the spring (linearity of the relationship between displacement and force)
There was always a limit to this, which caused problems 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 which can expand the dynamic range of control and improve response characteristics.

[Means for solving problems]

A disc playback device according to the present invention includes a rotating body that is rotatable around a certain axis and slidable along the axis, and an optical axis of the rotating body that is located eccentrically from the axis. A light condensing means supported so as to be substantially parallel to each other, a track tracking control coil provided on the rotating body, a focal position control coil, and a magnet provided on the fixed side; A coil and a magnet rotate the rotary body around the axis to control track deviation, and the focal position control coil and magnet cause the rotary body to slide along the axis to control defocus. It was designed to do so.

[Effect]

In this invention, since the track shift and the focus shift are controlled using one rotating body that is rotatable around a certain axis and slidable along the axis, each control The device is smaller and simpler than the one that uses a separate device, and since a spring is not used as a means to regulate the direction of movement as in the past, resonance during drive control is prevented. At the same time, linearity is improved and dynamic range is expanded. Furthermore, each control is performed by disposing each coil on the rotating body side and the magnet on the stationary side, so the weight of the rotating part is reduced and the magnetic path configuration on the magnet side is facilitated.

〔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. 43 is a shaft, a part of which is supported by a slide bearing 40 provided on the yoke 16, so that it can slide and rotate freely. 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 and control coil (hereinafter referred to as a focus control coil) 18 is also coupled to the shaft 43. Numerals 39 and 17 are magnets provided on the fixed side so as to face the tracking coil 18 and the focus control coil 18, respectively, and 37 is a yoke. The coils and magnets are arranged symmetrically with respect to the axis of the shaft 43.

Next, the effects will be explained.

In the device configured as described above, when a focus position control current is supplied to the focus control coil 18, the shaft 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 track tracking control are realized by a device that drives one rotating body, which allows for miniaturization.Also, since the heavy magnet is provided on the fixed side, the rotating body can be easily controlled. The weight of the parts is reduced and responsiveness is improved, and the construction of the magnetic path becomes easier than when the magnet is provided on the rotating side.

Furthermore, since no spring is used to regulate the direction of movement, mechanical resonance is less likely to occur, and the dynamic range (force-displacement linearity) is dramatically increased. Furthermore, since the rotation and sliding directions of the shaft are separated, there is almost no interference between them, and all directions of movement of the shaft are controlled, so there is no problem with the influence of disturbances as long as they are 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, according to the disc playback device of the present invention, a rotating body that is rotatable around a certain axis and slidable along the axis is provided, and a rotating body that is eccentric from the axis of the rotating body is provided. A light condensing means is supported at a position such that its optical axis is substantially parallel to the axis, and the rotating body is rotated about the axis to control track deviation, and the rotating body is rotated along the axis. Since the focus shift is controlled by sliding the optical axis of the condensing means,
In both cases of track deviation control and focus deviation control, it is possible to always maintain a state perpendicular to the disk surface, and to prevent track deviation and focus deviation of the focusing means without reducing the accuracy of reading signals from the disk surface. This has the effect of simplifying and downsizing the control device, improving the linearity of track shift and focus shift control, expanding the dynamic range of control, and improving response characteristics.

In addition, since the drive structure of the rotating body is composed of a tracking coil and a focal position control coil provided on the rotating body, and a magnet provided on the fixed side, the weight of the rotating part is not increased and responsiveness is improved. This has the effect of making the magnetic path better and making the configuration of the magnetic path easier.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the structure of the flat 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 cross-sectional view taken along line bb--b, FIG. 3 is a diagram showing the direction of tracking on the disk, and FIG. 4 is a cross-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 light, 7... Photodetector 8... Disk, 13... Pit, 16, 37... Yoke, 1
7, 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)

[Scope of Claims] 1. The position of a light condensing means that detects a track deviation of a light spot with respect to an information track of a disk on which information is recorded and a focus deviation of the light spot with respect to the information recording surface of the disk, and forms the light spot. is controlled according to the detected amounts of the track deviation and defocus, and information is optically read out from the information track by the light spot irradiated from the controlled condensing means, around a certain axis. a rotating body that is rotatable and slidable along the axis; and a light condensing means supported at a position eccentric from the axis of the rotating body so that its optical axis is substantially parallel to the axis. , a track tracking control coil for controlling the track deviation and a focus position control coil for controlling the focus deviation, each provided on the rotating body, and a coil provided on the fixed part facing each of the coils; and a magnet for rotating the rotating body together with the track tracking control coil and sliding the rotating body together with the focal position control coil. 2. Claim 1, characterized in that the track tracking control coil, the focal position control coil, and the magnets provided opposite to them are each provided at symmetrical positions with respect to the axis. Disc playback device described.