JPH02183430A - Optical head - Google Patents

Abstract

PURPOSE:To contrive to make the optical head small in size and light in weight by providing a laser light source, an optical means for transforming a laser light cross sectional shape, and a movement or rotation driving means of the optical means. CONSTITUTION:An emitted light of a laser 5 is made parallel by a lens 7, made incident on a uniaxial optical member group 9, transformed to a desired cross sectional shape, and focused to the recording film surface of an optical disk 1 by an objective lens 13. At the time of reproduction, a reflected light is reflected to a detection lens 15 side by a beam splitter 11, and converted to an electric signal by a photodetector 17. The optical member group 9 consists of a cylindrical concave lens 9a and a cylindrical convex lens 9b, and a coil 9a moves. By a variation of a relative distance of the lenses, a cross section of a laser light emitted from the lens 9b is varied to circular and laterally long or longitudinally long elliptical shapes. The laser light of the laterally long elliptical shape, and the laser light of the longitudinally long elliptical shape are used for reading out a recording bit of plural tracks, and erasing the recording bit on the track, respectively, and at the time of recording data onto the track, the laser light is returned to a circular shape and used. By a magnet and the coil, the lens 9a is moved, and an optical head being light is weight and small in size is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an optical head for polishing information on or reading information from an optical disk.

(Prior Art) Optical disk devices, magneto-optical disk devices, etc. use so-called optical heads to store various information on information storage media such as optical disks and magneto-optical disks, and to store this stored information. I like to play and sip.

This conventional optical head is composed of a semiconductor laser as a laser light source, a collimator lens, a beam splitter, an objective lens, a detection lens, a photodetector, etc.
Further, optical means for correcting the ellipse of the laser beam emitted from the semiconductor laser is fixedly provided between the collimator lens and the beam splitter.

This optical means for ellipse correction is specifically provided to correct the cross-sectional shape of the laser beam emitted from the semiconductor laser, and usually corrects the cross-sectional shape of the laser beam emitted from the semiconductor laser, i.e. Since the irradiation shape of the laser light projected onto a plane perpendicular to the optical axis of the Raded light has an elliptical shape, a uniaxial optical member such as a cylindrical lens or a prism is used to correct the elliptical light into a circular shape. The setting number will be set as appropriate.

Specifically, as shown in FIG. 6, for example, the laser beam irradiated from the semiconductor laser 5 is made into parallel light by the collimator lens 7, and then the ellipse correction cylindrical concave lens 109
There is one in which correction is made into a circular shape by using a and an ellipse correction cylindrical convex lens 109b. Also,
As shown in FIG. 7, the laser beam emitted from the semiconductor laser 5 is passed through two ellipse correction prisms 209a,
It is known that correction is made into a circular shape using b.

(Problem to be Solved by the Invention) However, for example, in an optical head for a phase change/structural change erasable optical disk, in addition to the one that corrects the semiconductor laser light into a circular shape as described above, A laser beam deformed into a vertically elongated ellipse along a group or land is also required. Therefore, two semiconductor lasers and a dedicated device for correcting each of the laser beams emitted from the semiconductor lasers into a circular shape or a vertically elongated ellipse shape are required, which poses an issue for miniaturizing the optical head. was.

The present invention has been made to solve the above problems, and includes:
Using laser light emitted from a single semiconductor laser, the laser light can not only be transformed into a circular shape or a vertically elongated ellipse, but also can be transformed into a horizontally elongated ellipse, thereby significantly reducing the size and weight. The object of the present invention is to provide an optical head that can achieve the following.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a laser light source that emits laser light, and an optical system that changes the cross-sectional shape of the laser light emitted from the laser light source. and a driving means for moving the optical means in the direction of the optical axis of the laser beam or rotating it around the optical axis.

(Function) The optical head of the present invention utilizes the characteristic that when the optical means is moved in the optical axis direction or rotated around the optical axis, the cross-sectional shape of the laser beam changes depending on the moving distance or rotation m. The cross-sectional shape of the laser beam is a horizontally oblong ellipse.

It is designed to transform into a circle or a vertically oblong ellipse.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the structure of an embodiment of the present invention.

First, in FIG. 1, an optical head 3 is disposed on the lower surface side of an optical disk 1 which is rotated by a rotation drive source such as a spindle motor (not shown).

The configuration of this optical head 3 will be explained below. The semiconductor laser 5 radially emits laser light with a predetermined optical output set in advance for each recording, erasing, and reproduction. The cross-sectional shape of this emitted laser beam is 1 in the minor axis and 2 in the major axis.
．． It has an oval shape of about 5 mm.

The collimator lens 7 converts the laser light radially emitted from the semiconductor laser 5 into parallel light.

- The axial optical member group 9 changes the cross-sectional shape of the laser beam that has passed through the collimator lens 7 and been converted into parallel light. Specifically, as shown in Figure 2),
This -axial optical member group 9 is a cylindrical concave lens 9a.
, a magnet 9C and a coil 9d for moving the cylindrical convex lens 9b and the cylindrical concave lens 9a in the optical axis direction, and the cylindrical concave lens 9a and the coil 9d are integrally constructed.

The beam splitter 11 transmits the incident laser light from the direction of the semiconductor laser 5 toward the optical disk 1, while the transmitted laser light is reflected by the optical disk 1 and enters the beam splitter 11 again toward the photodetector 17, which will be described later. reflect to.

The objective lens 13 focuses the laser light that has passed through the beam splitter 11 toward the recording surface of the optical disk 1, and converts the laser light that is reflected from the recording surface and enters radially into parallel light.

The detection lens 15 focuses the laser beam reflected by the beam splitter 11 toward the photodetector 17 .

Next, the operation of this embodiment will be explained.

In FIG. 1, laser light emitted from a semiconductor laser 5 is converted into parallel light by a collimator lens 7. When writing information on the optical disc 3, the semiconductor laser light is modulated according to the recorded information.

The laser beam shaped into parallel light by the collimator lens 2 is
, - The beam is incident on the axial optical member group 4 and has a circular cross section.

It is suitably transformed into a horizontally oblong elliptical cross section and a vertically oblong elliptical cross section. These lights with various cross-sectional shapes can be used depending on the purpose. - The laser beam that has passed through the axial optical member group 9 is incident on the objective lens 13 through the beam splitter 11. Then, the laser beam focused on the recording film surface of the optical disc 1 by the objective lens 13 is
Erase or play.

When reproducing information, reflected light from the optical disc 1 is reflected by the beam splitter 11 toward the detection lens 15 side, and is incident on the photodetector 17.

Thereby, the reflected light from the optical disc 1 is converted into an electrical signal by the photodetector 11, and a data signal is obtained.

Next, the function of the uniaxial optical member group 4 will be explained with reference to FIGS. 2(a) and 3.

As described above, the -axis optical member group 4 is composed of a cylindrical concave lens 9a and a cylindrical convex lens 9b, and of these two lenses, the cylindrical concave lens 9a moves linearly in the optical axis direction. That is, the coil 9d and the cylindrical concave lens 9a are integrated, and the cylindrical concave lens 9a moves in the optical axis direction together with the coil 9d by the coil 9d and the magnet 9C. In this case, when the relative distance between the cylindrical concave lens 9a and the cylindrical convex lens 9b changes, the cross-sectional shape of the laser beam emitted from the cylindrical convex lens 9b changes depending on the relative distance. That is, when the distance between the two is maintained at a certain distance, the shape becomes circular; when it is further away, it becomes a vertically elongated ellipse, and when it is closer, it changes to a horizontally elongated ellipse. The cylindrical concave lens 9a moves in three stages as described later, and the laser beam of the semiconductor laser 5 is transformed into three shapes: a circular shape, a horizontally oblong elliptical shape, and a vertically long elliptical shape depending on the moving distance. The configuration is as follows.

To explain the operation in detail, first, as shown in FIG.
When moving to the side, the elliptical light 1 is transformed into a vertically elongated ellipse (indicated by ■ in the figure) as described above. The length of the vertically elongated ellipse can be arbitrarily adjusted by adjusting the distance between the cylindrical concave lens 9a and the cylindrical convex lens 9b,
Therefore, the cylindrical concave lens 9a and the cylindrical convex lens 9 are arranged so that they form a vertically long ellipse with a desired length.
All you have to do is set the distance from b.

Next, when the cylindrical concave lens 9a is moved toward the cylindrical convex lens 9b, the laser light from the semiconductor laser 5 is transformed into circular light indicated by . In this case, the semiconductor laser 5 is corrected into a circular shape by the silitorically concave lens 9a and the convex lens 9b. Furthermore, when the cylindrical concave lens 9a is further moved toward the cylindrical convex lens 9b, the laser beam of the semiconductor laser 5 is transformed into a horizontally elongated ellipse shape as shown by ▪, as shown in FIG. 3(C). Since the length of the horizontally long ellipse is determined by the distance between the cylindrical concave lens 9a and the cylindrical convex lens 9b, the distance may be set in advance so that the horizontally long ellipse has a desired length as described above. In the above embodiment, the cylindrical concave lens 9a is moved in the optical axis direction with respect to the cylindrical convex lens 9b, but the cylindrical convex lens 9a is not limited to this.
Of course, b may be moved relative to the cylindrical concave lens 9a.

Next, another example of the - optical axis optical member group 9 will be described. FIG. 2(b) shows the configuration, in which the -axis optical member group 9 rotates around the optical axis. That is,
-A coil 9'' and a magnet 9e are provided on the outer periphery of the axial optical member group 9, and -the axial optical member group 9 and the coil 9f are integrated.Therefore, by energizing the coil 9f, 1 The axial optical member group 9 is configured to rotate around the optical axis together with the coil 9f.A cylindrical concave lens 9
When a and the cylindrical convex lens 9b are rotated around the optical axis, the cross-sectional shape of the laser beam emitted from the cylindrical convex lens 9b changes. That is, the distance between the cylindrical concave lens 9a and the cylindrical convex lens 9b is
The shape of the laser beam can be changed by rotating both of them around the optical axis while holding them at appropriate positions for ellipse correction.

To explain the operation, first, in the state shown in FIG. This state is the same as the state described in FIG. 3 (3) of the previous embodiment. When the uniaxial optical member group 9 is rotated from this state by 90'' around the optical axis, the laser beam from the semiconductor laser 1 is shaped like a horizontally long ellipse as shown by ■, as shown in FIG. 4(b). Therefore, in this embodiment, the laser beam of the semiconductor laser 5 can be transformed into a circular shape or a horizontally oblong elliptical shape.

FIGS. 5A and 5B are enlarged views of the recording surface of the optical disc 1, showing the recording bits 23 formed on the lands 21 of the recording film 19. The light from the semiconductor laser 5 transformed into a horizontally long ellipse as described in the above embodiment is shown as a horizontally long elliptical light 25 in the fifth image).
Recorded bits 23 of a plurality of tracks 21, 21 can be used for multi-track read simultaneously.

Furthermore, the above-mentioned vertically elongated elliptical light can be used as an erase beam for a phase change/structure change erasable optical disk. The laser beam 27 having a vertically elongated elliptical shape shown in FIG. Used to return to circular light.

Therefore, in the embodiment shown in FIG. When recording data on the optical disc 1, a circular laser beam may be used, and when erasing data recorded on the optical disc 1, a vertically elongated elliptical laser beam may be used.

This allows a semiconductor laser to be used as an optical head for a phase change/structural change type erase-pull optical disk.

Since parts such as the collimator lens can be used in common, the optical head can be made much smaller and lighter. Moreover, it can be transformed into a horizontally oblong ellipse shape, so if it is used for multi-reading, the transfer rate can be more than doubled when reading data from an optical disc, and the performance of the optical head can be improved. .

Moreover, in the embodiment shown in FIG. 2 υ, the shape is circular.

Since it can be transformed into a horizontally long elliptical shape, the circular shape can be used for recording, and the horizontally long elliptical shape can be used for multi-reading.

[Effects of the Invention] As explained above, according to the present invention, the optical means is moved in the direction of the optical axis or rotated around the optical axis, so that the cross-sectional shape of the laser beam can be changed to, for example, a circle, an elongated ellipse, or an elongated ellipse. As a result, parts such as a semiconductor laser can be used in common for the recording circular spot and the vertically elongated elliptical spot for erasing on a phase-change/structure-change erasable optical disk, making the optical head significantly smaller. It can be made lighter and lighter.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 (2nd image) is a block diagram showing the main part structure of the present invention, and FIG. Figure 3 (O), (ω. FIG. 5(a) is a perspective view showing the state in which the surface of the optical disc is irradiated with a horizontally elongated elliptical spot, FIG. 7 and 7 are configuration diagrams respectively showing conventional circular correction devices. 1... Semiconductor laser 2... Collimator lens 3.
... Optical disk 4 ... - Axial optical member group 9 ... Cylindrical concave lens 10 ... Cylindrical convex lens ... Coil 2 ... Magnet 9 ... Horizontal elliptical light 20 ... Vertical elliptical light

Claims (1)

[Scope of Claims] A laser light source that emits a laser beam; an optical means that changes the cross-sectional shape of the laser beam that is emitted from the laser light source; and an optical means that moves the optical means in the optical axis direction of the laser beam, or An optical head comprising: a drive means for rotating around an optical axis.