JPS6332738A - Disk reproducing device - Google Patents

Abstract

PURPOSE:To make control at high accuracy by providing a turning body slidable around the axial line, supporting a condensing means to make the optic axis parallel to the axial line deviating from the axial center, and providing a thrust driving device for controlling focus deviation that slides along the axial line. CONSTITUTION:A condensing lens 3 having the optic axis deviated from the axial center of a shaft 43 and becomes parallel to the axial line is attached in a supporting plate 44. A part of the shaft 43 supported by a slide bearing made of low friction material is notched and a tracking coil 42 is attached to conform to the center axis. A controlling coil 18 is coupled to the shaft 43, and magnets 39, 17 are provided opposite to coils 42, 18. Current is applied in the coil 18, and the focus position is corrected by shifting the shaft 43, supporting plate 44 and the lens 35 in the direction A. Track trace position controlling current is applied in the coil 42, and the shaft 43 and supporting plate 44 are rotated in the direction B and the lens 35 is turned in the direction at right angles to the track. By making control by driving single turning body and separating the direction of rotation and sliding, miniaturizing and control of high accuracy can be attained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a playback 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, 15 is a track tracking control mirror device, 6 is a focus control lens device, 7 is a photodetector, and 8 is a 9 is a motor, 10 is a reproduction signal processing circuit, 11 is a track tracking control circuit, 12 is a focus control circuit, and l3 is a pit.

Next, the operation will be explained. A laser beam 2 emitted from a laser light source 1 is diffused by a diffusion lens 3, and then passed through a half mirror 4.
After passing through the track tracking control mirror device 5, a condensing lens housed in the focus control lens device 6 forms a micron-order light spot (optical needle) on the disk 8. On the other hand, the disk 8 has pits 13 on the order of microns in the bridge shown in Figure 6, forming a spiral or concentric trunk! 1. recorded. A signal is optically reproduced by maintaining the optical beam 12 focused on the micron order in a proper positional relationship on the pit 13 on the micron order.

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 the disk 8 is rotated in the direction of the arrow C in Fig. 5, the initial waviness of the disk 8, vibrations caused by the motor 9, external holes, etc. cause the recording surface of the disk 8 to move as shown in Figs. 7 a, b, and c.
will change as shown in. Similarly, in the relationship between the light spot and the recording track, positional deviations occur as shown in FIGS. 7d, e, and r due to meandering of the recording trunk, eccentricity of the disk 8, etc. 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 focus 13 in the focal direction and in the direction perpendicular to the track.

For this reason, in the conventional device, a focus control lens device 6 and a trunk tracking control mirror device 5 were used. These devices each move a condensing lens up and down in the direction indicated by the arrow perpendicular to the disk 8 (see FIG. 5), and rotate the mirror of the track tracking mm mirror V device 5 in the direction of arrow B.

Although a detailed explanation will be omitted here, the distance between the disk 8 and the condensing 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 1
2 and the trunk tracking control circuit 11 to send the control signal to the focus control lens device 6 and the track tracking control mirror device 5.
, and appropriate corrections are made accordingly.

No. 8yJ is a sectional view of a main part of a conventional focus control lens device, and No. 9m is a conceptual configuration diagram of a track tracking control mirror device. In FIG. 8, a coil 1B is installed in the magnetic flux formed by the yoke 16 and the magnet 17, and by passing a control current through it, the lens frame 20 supported by the spring 15 moves in the direction indicated by the arrow. As this spring 15,
Annular grooved leaf springs were used. Note that 14 is a condenser lens, and 19 is a support frame fixed to the yoke 16.

In addition, in FIG. 9, 21 is the track tracking 11 in FIG.
A mirror 24 corresponding to the mirror of the 11il mirror device is a track tracking control coil, and each is fixed to a wire spring 22. The coil 24 is installed in the magnetic flux of the magnet 23, and is rotated in the direction of arrow B by passing a control current through the coil 24.

(Problems to be Solved by the Invention) The conventional disc playback device is configured as described above, and uses the springs 15 and 22 for focus control and track tracking control.However, the conventional disk playback device operates like this. When a spring is used to regulate the direction, these mechanical resonances tend to occur, which adversely affects the characteristics of the control device.Also, the device operates against the elastic force of the spring. There is always a limit to the dynamic range (linearity of the displacement-force relationship) of a spring, which poses a problem in terms of control characteristics.

In addition, 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. there were.

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 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, a semiconductor laser light source, an objective lens, and a photodetector, and is eccentric from the axis. a light condensing means supported at a position such that its leading axis is substantially parallel to the axis; a rotating device for controlling trunk displacement by rotating the rotating body; A thrust drive device for controlling defocusing is provided.

[Effect]

In this invention, since the control for track deviation and focus deviation is performed 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 those that are performed using 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. At the same time, linearity is improved and the dynamic range is expanded. Furthermore, since the optical system is integrated, the optical system becomes compact and easy to replace, and since the light source and the objective lens move simultaneously, the precision of the light spot shape is improved.

〔Example〕

Here, before a detailed explanation of the present invention, the basic configuration of the present invention will be explained with reference to FIG. 2. FIG. 2 shows a cross-sectional view of the driving mechanism of the condensing means. 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 It is supported by a slide bearing 40 provided in the body, and is slidable 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. Reference numeral 30 denotes a semiconductor laser light source, 31 a collimating lens, and 35 a condensing lens. They are mounted parallel to each other.

42 is a track tracking control coil (hereinafter referred to as a tracking coil), and this coil 42 is shown in FIG.
As shown in FIGS. 1 and 2B, a portion of the shaft 43 is cut out, and the coil 42 is attached so as to coincide with the central axis of the shaft 43. 39 is a magnet provided to face the tracking coil 42.

A focus position control coil (hereinafter referred to as focus control coil) 18 is also coupled to the shaft 43. 17
37 is a magnet provided to face the focus control coil 18, and 37 is a yoke.

Next, the effects of the above device 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
The support plate 44 moves in the direction of arrow A, and the condensing lens 35 also moves in the direction of arrow A, so that the focal position is corrected. Further, when a track tracking position control current is supplied to the tracking coil 42, the shaft 43 and the support plate 44 rotate in the direction of arrow B, and the condenser lens 35 rotates in a direction perpendicular to the trunk. This is in the direction of arrow B in FIG. 4, and actually draws an arc, but the track tracking control amount is about 0.2 to 0.3 wr, and the distance between the condenser lens 35 and the central axis of the shaft 43 The error can be almost ignored if it is set to be more than a few cranes9.Next, in Figure 1, an embodiment of the present invention based on the above-mentioned basic configuration is explained with reference to Figure 1, which is the same as Figure 2. Reference numerals indicate the same parts, and in this embodiment, a semiconductor laser is used as the laser light source, and an optical system, that is, the laser light source 30. SELFOC lens as objective lens 45. and the photodetector 7 are all attached to the support plate 44. Note that the other configurations and control operations are the same as those of the apparatus shown in FIG. 2 above.

In this embodiment, the focus position control and the track tracking control are realized by a device that drives one rotating body, so it is possible to reduce the size, and since no spring is used to regulate the direction of movement, Mechanical resonance is less likely to occur, and the dynamic range (linearity of Kerr displacement) is dramatically increased.

Furthermore, the rotation and sliding directions of the shaft are separated, so there is almost no interference between them (all directions of movement of the shaft are controlled, so there is no problem with disturbances as long as they are within the control range).

Furthermore, since the optical system is integrated, the optical head becomes more compact and replaceable, which is desirable from a practical standpoint. In addition, in the example of FIG. 2, only the condenser lens 35 of the optical system moves during each control, so strictly speaking, the shape of the light spot changes, but in this embodiment, the light source moves from the light source to the objective Since the lens moves as one, there is no change in the spot shape, and there is no offset of the lens, making it possible to perform highly accurate control.

〔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, 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, the optical axis of the focusing means can always be kept perpendicular to the disk surface in both cases of track shift control and focus shift control. Simplification of a device that controls track deviation and focus deviation of a light condensing means without reducing the accuracy of reading signals from a disk surface.

This has the effect of realizing miniaturization, improving the linearity of track deviation and defocus control, and expanding the dynamic range and improving responsiveness.

In addition, since the condensing means consisting of the semiconductor laser light source, objective lens, and photodetector is integrated, the optical head becomes more compact and replaceable, and the optical system is integrated for each control. Because it moves, there is no change in spot shape, etc., and there is an effect that highly accurate control can be performed.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the configuration of the main parts of an embodiment of the present invention, FIG. 2 is a diagram showing the basic configuration of the invention, and FIG. 3(a)
, (bl is a diagram showing the installation state of the rotary drive coil and shaft in the device shown in Figure 2, Figure 3 (a) is a front view, and Figure 3 middle) is the bb line thereof. A cross-sectional view, FIG. 4 is a diagram showing the direction of track tracking on the disk, and FIG.
The figure is a sectional view showing the configuration of the main parts of a conventional optical playback device.
FIG. 6 is a diagram showing the relationship between the disk and the trunk, FIG. 7 is a diagram illustrating the positional relationship between the focused light beam and the pits on the disk, and FIG. 8 is a cross-sectional view of a conventional focus control lens device. 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... Coil for focus control, 42... Coil for tracking control, 19... Support frame, 30... Semiconductor laser light source, 31... Collimating lens, 35... Condenser lens, 40...Slide bearing, 43...Shaft, 44...Support plate, 45...Selfoc lens. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) Detecting the misalignment of the light spot with respect to the information track of the disc on which information is recorded and the defocus of the light spot with respect to the information recording surface of the disc, and adjusting the position of the light condensing means that forms the light spot on the said track. The information track is controlled according to the detected amount of deviation and defocus, and the information is read out optically from the information track by the light spot irradiated from the controlled condensing means, which is rotatable around a certain axis. and a rotating body that is slidable along the axis; a semiconductor laser light source; an objective lens for focusing laser light from the light source onto the disk; and a photodetector for detecting reflected light from the disk. 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 disc playback device comprising: a rotation device that controls track deviation; and a thrust drive device that controls the focus deviation by sliding the rotation body along the axis.