JPS6132733B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical head used for reading information recorded optically or holographically, and is particularly effective for simplifying devices such as optical video disks and holographic video files. It is.

Conventionally, in optical video disks or holographic video file devices, He-Ne, Ar, etc. are usually used as light sources for reading information.
Gas lasers such as the following are used. Especially He-
Ne lasers are commonly used because they are the most compact and inexpensive among gas lasers. For example, all optical video disk devices released by various companies use He--Ne lasers as light sources. However, in the current situation
The size of the He−Ne laser is 20 to 30 mm at its smallest.
They are also quite expensive, ranging in length from several tens of thousands of yen to several hundred thousand yen. Moreover, in order to guide this laser beam to the optical head for illuminating the disk, it is necessary to use many optical elements such as reflecting mirrors and prisms, which complicates the configuration of the device. This will increase the cost of A particularly big problem is that when the laser beam sequentially follows the information track,
Since the following high precision is required, it is necessary to place the laser on the same moving table as the optical head and move it, and to finely deflect the light beam. Conventionally, in order to solve this problem, the He--Ne laser and the optical head were placed on a large moving table at the same time and moved, and a deflection element such as a galvanic mirror was used to perform fine tracking. However, this resulted in the equipment being quite large. Furthermore, if the deflection surface of the deflection element changes, aberrations occur, making it impossible to form a predetermined spot on the track. Another problem is that in order to eliminate the effects of jitter caused by uneven disk rotation, conventional methods use a galvanic mirror that vibrates in the tangential direction of the disk rotation, which further complicates the device. was.

The present invention eliminates the above-mentioned drawbacks and provides an optical head that enables an inexpensive and simple optical video disk or holographic video file device. The outline of the present invention is as follows. A small and compact semiconductor laser light source is used as the laser light source, and by directly vibrating it, minute information tracks can be tracked.

Hereinafter, the present invention will be explained in detail with reference to Examples. A first embodiment of the invention is shown in FIG. A semiconductor laser 1 is bonded to a heat sink 2.
This is directly moved in the direction of the arrow by the vibration element 3 via the connecting shaft 4. A laser beam 5 emitted from the laser is focused by a lens 6 onto an information track 8 on an information board 7. When the information track 8 deviates in the direction of the arrow, the amount of deviation is detected by the detector 10 and the drive circuit 11 is operated. The output of the drive circuit 11 is input to the vibration element 3, which moves the semiconductor laser in the direction of the arrow by an amount corresponding to the amount of deviation of the information track. The frequency of movement can usually be considered to be several 10 to several 100 Hz. In this way, minute information tracks can be tracked. Note that the semiconductor laser, the vibrating element, the connecting shaft, and the lens are attached to the optical head 9. In more detail, the feedback mechanism regarding the movement of the semiconductor laser when following an information track will be explained. Figure 2 shows its configuration.

A laser beam 24 from a semiconductor laser 23 attached to a heat sink 22 illuminates an information track 21 on an information board 20 through a lens 25. Diffracted lights 27 ₁ and 27 ₂ from the information track are detected by photodetectors 26 ₁ and 26 ₂ , respectively. Now, when the information board moves relatively in the direction of the arrow, the diffracted light 27 ₁ becomes larger than the diffracted light 27 ₂ . Photodetector output
28 ₁ and 28 ₂ are input to the differential amplifier 29. By looking at the output of this differential amplifier, the direction and magnitude of movement of the information track can be known. This output causes the vibrating element drive circuit 30 to operate, the vibrating element 31 to move, and the semiconductor laser 23 to move.
also moves in the direction of the arrow, forming a feedback system for following the information track. Meanwhile, the information signal from the information track is detected by the photodetector ₂₆₃ and goes to the video amplifier 32, where the information is reproduced.

Note that the weight of the heat sink becomes a problem when vibrating a semiconductor laser, but currently the minimum weight is 2~
Some devices weigh about 3g, so even a fairly small vibrating element can function satisfactorily. Examples of the vibrating element include piezo elements, moving magnets, and moving coils. Typically, the vibration of an information truck is several 10 to 100.
Since the distance is about μm, it is sufficient to choose one that follows this. Also, in the figure, the laser beam is converged onto the information track by one lens, but the number of lenses is not necessarily limited, and the laser beam is not necessarily focused on the information track. It does not need to be converged; for example, it may be illuminated with a parallel light beam. Other embodiments that take such a case into consideration will be shown below.

FIG. 3 shows an embodiment of the invention. in this case,
The laser beam 5 is turned into a parallel beam by the lens 6, and illuminates the information track 8. The rest is the same as the first embodiment. In both the first and second embodiments, the vibrating element vibrates the semiconductor laser light source in a direction perpendicular to the information track. In this case, the information track can be tracked with high precision by vibrating the semiconductor laser. By making the vibration direction of the semiconductor laser perpendicular to the arrow, it is possible to correct minute deviations in the direction of movement of the information track, that is, jitter.

FIG. 4 shows a third embodiment of the invention. The semiconductor laser 12 and the heat sink 13 are the vibration element 1
4 and a vibrating element 15 arranged in a direction perpendicular thereto. The laser beam 16 is focused by a lens 17 onto an information track 19 on a disk 18. The vibration direction of the vibration element 14 is equal to the direction of the information track, and the vibration direction of the vibration element 15 is perpendicular to the information track. Now, considering the displacement of the information track due to eccentricity and the jitter in the direction of rotation as displacements that occur when the disk rotates, the former is caused by the vibration of the semiconductor laser light source caused by the vibration element 15, and the latter is caused by the vibration of the semiconductor laser light source caused by the vibration element 14. This will be corrected by the vibration of the laser. Although the method of detecting the amount of deviation in this case is omitted in the figure, it can be considered to be the same as in FIGS. 1 and 2. Information in the information track includes:
Either bit information found in ordinary optical video disk systems or holograms may be considered. The size of the semiconductor laser can be reduced to about 5 mm cubed even with the addition of a heat sink, and the vibrating element can also be made to be about 1 cm cubed, making it possible to create a simple optical head that is extremely compact overall. be able to. Moreover, it is not necessary to use the number of expensive mirror prisms, and the cost can be significantly reduced. Further, in the optical head of the present invention, since the laser itself is built into the optical head and the semiconductor laser light source is directly moved within the optical head, accuracy in tracking information can be improved. However, the movement of the optical head from one track to another utilized a conventional video disk, magnetic disk head transport mechanism, etc.

In each example, the information recording medium is as follows:
Either a disk-shaped tape or a sheet-shaped one may be used.

As described above, according to the present invention, the conventional optical video disk device or holographic video file device can be greatly simplified and cost reduced, and tracking can be performed with high precision.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one embodiment of the present invention, FIG. 2 is a supplementary diagram of this embodiment, and FIGS. 3 and 4 are diagrams of other embodiments of the present invention. 1 is a semiconductor laser, 2 is a heat sink, 3 is a vibration element, 4 is a coupling shaft, 5 is a laser beam, 6 is a lens, 7 is an information board, 8 is an information track, 9 is an optical head, 10 is a photodetector, 11 is the drive circuit.

Claims (1)

[Claims] 1. At least a semiconductor laser light source, an optical means for focusing a light beam from the semiconductor laser light source onto a track on an information recording medium, and a structure for moving the semiconductor laser light source in a direction substantially perpendicular to the traveling direction of the track. an optical head having a vibrating means and movable in a direction substantially perpendicular to the traveling direction of the track, the optical head being capable of moving the light beam and the track from the light from the information recording medium generated by the irradiation of the light beam; An optical head characterized in that it is used in conjunction with means for detecting deviations of the optical head and generating a signal for the optical beam to follow the track, the signal driving the vibrating means.