JPS6256580B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reproducing device for optically reading out recorded information from a video disc, a PCM disc, etc., and more particularly to a driving mechanism for a light condensing means that forms a light spot on the disc surface.

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 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 is a track control circuit, 12 is a focus control circuit, and 13 is a pit.

Next, the operation will be explained. A laser beam 2 emitted from a laser light source 1 is diffused by a diffusing lens 3, passes through a track tracking control mirror device 5, and is focused on a micron-order light spot (optical needle) by a condensing lens housed in a focus control lens device 6 on a disk 8. form. On the other hand, as shown in FIG. 2, pits 13 on the order of microns are recorded on the disk 8 as spiral or concentric tracks. A signal is optically reproduced by maintaining the light beam 2 focused on the micron order on this micron order pit 13 in an appropriate positional relationship. FIG. 3 is a diagram for explaining the positional relationship between the light spot and the disk, in which the light beam 2 is focused and then spread out again. It is obvious that in order to perform the most efficient reproduction, it is better to reproduce near where the light is most concentrated. However, when the disk 8 is rotated in the direction of the arrow C, the recording surface of the disk 8 changes as shown in FIG. . Similarly, in the relationship between the light spot and the recording track, positional deviations occur as shown in FIGS. 3(d), (e), and (f) due to meandering of the recording track, eccentricity of the mounting of the disk 8, etc. Therefore, it is necessary for the light spot of the light beam 2 to always track the pit 13 in the focal direction and in a direction perpendicular to the track. For this purpose, a focus control lens device 6 and a track tracking mirror device 5 have been used in conventional devices. Each of these devices moves a condenser lens up and down in the direction of arrow A perpendicular to the disk 8, and rotates a mirror 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 optical detector 7, and then sent via the focus control circuit 12 and the track tracking control circuit 11. A control signal is input to the focus control lens device 6 and the track tracking mirror device 5, and appropriate corrections are made. Figure 4 is a sectional view of the main parts of a conventional focus control lens device.
FIG. 5 is a conceptual diagram of the track tracking mirror device. In FIG. 4, a coil 18 is placed in the magnetic flux formed by the yoke 16 and the magnet 17, and by passing a control current through it, the spring 15 is
The lens frame 20 supported by moves in the direction of arrow A. As this spring 15, an annular grooved plate spring or the like has been used.

Further, in FIG. 5, 21 is a mirror, 22 is a wire spring, and 24 is a coil, each of which is fixed to the wire spring. The coil 24 was placed in the magnetic flux of the magnet 23, and had a structure in which it was rotated in the direction of arrow B by passing a control current through the coil 24.

Since the conventional reproducing device is configured as described above, mechanical resonance of the springs 15 and 22 tends to occur, which adversely affects the characteristics of the control device. Further, since the spring operates against the elastic force of the spring, there is always a limit to the dynamic range (linearity of the displacement-force relationship) of the spring, which has been a problem. In addition, when using a semiconductor laser as a laser light source to simplify the mechanism, 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. It was hot.

In order to eliminate the drawbacks of the conventional device as described above, the present invention makes it possible to displace the track tracking control coil and the focal position control coil as one unit, and
The invention further uses a current component parallel to the optical axis of the condensing lens of the control current flowing through the coil for track tracking control, and the second invention further uses reflected light from a half mirror to form a light spot. As a result, it is an object of the present invention to provide a disc playback device that is less likely to cause mechanical resonance and can be made smaller and simpler as a whole.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 6 is a sectional view of essential parts of an embodiment of the present invention.
30 is a semiconductor laser light source, 31 is a collimating lens, 35 is a condensing lens, 37 is a yoke, 39 is a magnet, 40 is a slide bearing, 42 is a coil, 43 is a shaft, and 44 is a support plate.

The coil 42 is arranged as shown in FIGS. 7a and 7b.
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.

Next, the operation will be explained. The coils 18 and 42 are attached to the shaft 43, and the condenser lens 35 is attached to the shaft 43 via a support plate 44 so that its optical axis is located parallel to and eccentric to the central axis of the shaft 43. is attached to. A portion of the shaft 43 is slidably and rotatably supported by a slide bearing 40 provided on the yoke 16. This slide bearing 40 is made of a material with an extremely low coefficient of friction, such as Teflon. In the device configured as described above, when a focus position control current is supplied to the coil 18, the shaft 43 moves in the direction of arrow A, and the focus position is corrected. When a track tracking position control current is supplied to the coil 42, the shifter 43 rotates in the direction of arrow B, and the condenser lens 35 moves in a direction perpendicular to the track. In this case, driving force can be obtained using only the current component of the control current flowing through the coil 42 that is parallel to the optical axis of the condenser lens 35. This is in the direction of arrow B in Figure 8, and actually draws an arc, but
The track tracking control amount is about 0.2 to 0.3 mm, and the distance between the central axis of the condenser lens 35 and the shaft 43 is calculated as a number.
If it is set to mm or more, the error can be almost ignored.

With this configuration, the coil for focal position control and the coil for track tracking control can be integrated into a displaceable support, which prevents mechanical resonance from occurring and allows for miniaturization.Furthermore, the springs used in conventional devices can be reduced. Therefore, there is no mechanical resonance, and the dynamic range (force-displacement linearity) increases dramatically. Furthermore, since the rotation and sliding directions of the shaft are separated, there is almost no interference between them, and since all directions of movement of the shaft are controlled, there is no problem with the influence of external disturbances as long as they are within the control range.

In addition, when the emitted light from the semiconductor laser is transmitted through a half mirror and guided to the condenser lens as in the conventional device, since the half mirror is tilted with respect to the optical axis, the incident angle of light at each part is different, and the half mirror Due to refraction due to thickness, the magnetic flux shifts and aberrations occur, but if the emitted light from the semiconductor laser is reflected by a half mirror and guided to the condenser lens as in the example, such aberrations will not occur and high precision light will be produced. Spots can be formed on the disk. FIG. 9 is a sectional view of another embodiment of the present invention, in which a semiconductor laser is used as the laser light source, and all optical systems are mounted on a support plate, where 45 is a self-occurring lens. With this configuration, the optical head becomes more compact and replaceability is improved, which is preferable from a practical point of view.

As described above, according to the present invention, the track tracking control coil and the focal position control coil can be integrally displaced, and as a first invention, the track tracking control further includes a condenser lens for controlling the control current flowing through the coil. Since a current component parallel to the optical axis is used, and as a second invention, reflected light from a half mirror is used to form a light spot, mechanical resonance is less likely to occur and a light spot can be formed with high precision. In addition, it is possible to obtain a disc playback device that can be made smaller and simpler as a whole.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the configuration of the main parts of a conventional optical playback device, Figure 2 is a diagram showing the relationship between the disk and the track, and Figure 3 is a diagram showing the positional relationship between the condensed light beam and the pit on the disk. 4 is a cross-sectional view of a conventional focus control lens device, FIG. 5 is a conceptual configuration diagram of a conventional track tracking mirror device, and FIG. 6 is a main part of an embodiment of the present invention. 7a and 7b are views showing the installation state of the rotary drive coil and shaft in the embodiment shown in FIG. 6, where a is a front view and b is a view along line bb of a FIG. 8 is a cross-sectional view showing the direction of track tracking on the disk, and FIG. 9 is a cross-sectional view of another embodiment of the invention. In the figure, 2 is a laser beam, 4 is a half mirror, 7 is a photodetector, 8 is a disk, 16 and 37 are yokes, 17 and 39 are magnets, 18 and 42 are coils, 19 is a support frame, and 30 is a semiconductor laser. A light source, 35 a condensing lens, 40 a slide bearing, 43 a shaft, and 44 a support plate. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A light condensing means for forming the light spot by detecting a track deviation of the light spot with respect to the information track of the disk on which information is recorded and a focus deviation of the light spot with respect to the information recording surface of the disk. The position is controlled according to the detected amounts of the track deviation and defocus, and the information is optically read out from the information track by the light spot irradiated from the controlled condensing means, wherein the information recording A first coil wound to generate magnetic flux substantially parallel to the information recording surface and a second coil wound to generate magnetic flux substantially perpendicular to the information recording surface are provided, a support body capable of integrally displacing the first and second coils; the support body is located at a position eccentric from the magnetic flux center line of the second coil, the optical axis of which is approximately the same as the magnetic flux center line of the second coil; A light condensing means supported in parallel, provided at a base movably holding the support, acts on a current component parallel to the optical axis of the current flowing through the first coil to cause the track deviation. displacing the support body so as to control the second
A disc playback device comprising a magnetic mechanism for displacing the support body by acting on a current flowing through the coil to control the defocus. 2. The disc playback device according to claim 1, wherein the first coil includes a straight portion parallel to the optical axis of the light condensing means. 3 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 condensing lens 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. In a device that optically reads information from the information track using the light spot irradiated from the controlled condensing lens according to the detected amount of defocus, the magnetic flux is directed approximately parallel to the information recording surface. A first coil wound to generate a magnetic flux, and a second coil wound to generate a magnetic flux in a direction substantially perpendicular to the information recording surface are provided. a support body capable of integrally displacing the coil of
A condensing lens supported by the support so that its optical axis is substantially parallel to the magnetic flux center line of the second coil, and arranged so that its output optical axis is approximately perpendicular to the optical axis of the condensing lens. a half mirror that reflects the emitted light from the semiconductor laser and guides it to the condensing lens; and a half mirror that transmits the reflected light from the disk obtained through the condensing lens through the half mirror. a photodetector that receives light;
The support member is disposed at a base portion that displaceably holds the support member, the support member is displaceable so as to control the track deviation in cooperation with the first coil, and the support member is displaceable in cooperation with the second coil so as to control the track deviation. A disc playback device comprising a magnetic mechanism for displacing the support to control defocus.