JPH0289236A - Multibeam optical head - Google Patents

Abstract

PURPOSE:To accurately allow plural spots to follow a prescribed track by adjusting the rotation of a reflection mirror arranged before an objective lens in an optical path. CONSTITUTION:The reflection mirror 4 is allowed to turn around a z axis and the 1st and 2nd beams 8, 9 projected from a two-beam semiconductor laser 1 are arranged in the x axis direction, i.e. in the jitter direction on an information recording medium 6. Since the direction cosines of the 1st and 2nd beams 8, 9 reflected by the reflection mirror 4 are changed in accordance with a rotational angle thetaz when the reflection mirror 4 is rotated around the a axis by thetaz, positional relation between the 1st and 2nd spots 10, 11 on the medium 6 is changed. Consequently, the positions of two spots 15, 16 can be accurately and easily adjusted on the same recording track or adjacent recording tracks.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a multi-beam optical head that condenses and irradiates a plurality of light beams onto an information recording medium. The present invention relates to a multi-beam optical head that can accurately guide information to an information recording track.

[Prior Art] FIG. 11 shows, for example, a conventional multi-beam optical head having two light emitting sources, including an array type two-beam semiconductor laser (1) in which light emitting points are arranged in a straight line, and this A collimator lens (2) for converting the diverging light flux from the two-beam semiconductor laser (1) into a parallel light flux, which transmits the parallel light flux from the collimator lens (2) and converts the divergent light flux from the information recording medium (6) into a parallel light flux. A beam splitter (3) for reflecting and separating the reflected light, a reflecting mirror (4) for reflecting the parallel light beam that has passed through this beam splitter (3) and making it enter the objective lens (5), and condensing the parallel light beam. optical components such as an objective lens (5), an information recording medium (6), and a lens that detects reflected light from the information recording medium (6);
and a detection optical system (7) consisting of a photodetector.

With the above configuration, the array-type two-beam semiconductor laser (1) that is the light emitting source outputs the first beam (8) and the second beam (9), respectively, by an external semiconductor laser drive circuit (not shown). It is possible to emit light independently.

These first beam (8) and second beam (9) are formed into a first spot (10) and a second spot (10), respectively, on the surface of the information recording medium (6) by an objective lens (5). 11).

In such a multi-beam optical head, various functions as described below can be realized depending on the positional relationship between the two spots (10) (It) and the recording track of the information recording medium (6). Figure 12 shows two spora l-(
10) The positional relationship between (11) and the recording track of the information recording medium (6) is shown, and (12) is the recording track. FIG. 12(a) shows a state in which two spots (10) and (11) are formed on the same recording track (12),
In such a positional relationship, for example, a so-called real-time monitor operation is performed in which information is recorded at the preceding first spot (10) and information is immediately reproduced at the second spot (11) one row later. becomes possible. Furthermore, in a rewritable information recording medium, so-called override occurs, in which new information is recorded in a preceding second spot (11) while erasing information in a preceding first spot (10). Operation becomes possible. 1st
Figure 2(b) shows a state in which two spots (10) (tt) are formed on adjacent recording tracks (12), and in this positional relationship, different information cannot be recorded or reproduced in parallel. This makes it possible to improve the information transfer speed.

In addition, the detection optical system (7) has two spora) (10)
(11) The reflected light from the information recording medium (6) is detected to generate a reproduction signal, a focus error signal, and a track error signal, but a detailed explanation of the operation will be omitted here.

v [Invention/Problem to be Solved] Since the conventional multi-beam optical head is configured as described above, there are problems h' as listed below.

That is, from the beam semiconductor laser (1) to the objective lens (
Since the optical system leading to step 5) is fixed, (1) initial adjustments are made so that the two spots (20) and (11) are accurately formed on the same recording track or on adjacent recording tracks. There must be.

(,:) In the disc-shaped information recording medium (6), the curvature of the recording trunk differs depending on the radius, but the curvature of the recording trunk must be exactly 6 points or more on the predetermined track at all radii from the innermost circumference to the outermost circumference. It won't happen.

(lii) The positional relationship between the two spots and the recording track must not change due to external environments such as 4 degrees or vibration.

subject to severe restrictions. For this reason, precise arrangement precision of each optical part and strict initial adjustment precision for the recording track of each spot are required, resulting in a problem of a marked lack of electrical productivity.

This invention was made to solve the above-mentioned problems, and it is possible to accurately position multiple spots emitted from a multi-beam semiconductor laser and formed on the surface of an information recording medium at predetermined positions on any recording track. The objective is to obtain a multi-beam optical head that can lead to the relationship.

[Means for Solving the Problems 1] A multi-beam optical head according to the present invention includes a collimator and
A reflective mirror provided to guide the parallel light flux emitted from the lens to the objective lens is rotatable.

[Function] In the present invention, by rotating the reflecting mirror, the 19 spots formed on the surface of the information recording medium are accurately guided to a predetermined positional relationship in any recording track.

[Example] Hereinafter, a first example of the present invention will be described with reference to FIGS. 1 and 2.

In Fig. 1, the reflecting mirror (4) is rotatable around two axes, and its pond has the same configuration as Fig. 11 shown in the conventional example, and the seat in the figure (with respect to the vote axis) is shown in Fig. 1. , the first beam (8) and the second beam (9) emitted from the 2-bit semiconductor laser (1) are aligned in one direction with jitter in the X-axis direction, that is, on the surface of the information recording medium (6). .

Next, the operation will be explained. Rotate the reflecting mirror (4) to 0 around the Z axis.
When the information recording medium (6 ) on the surface of the first subo-nod (10) and the second spot (
ll) changes.

Figure 2 shows how the two spora) (10) and (11) change in the radial direction (y) on the surface of the information recording medium (6).
(in the axial direction) and jitter in one direction.

In Figure 2, the black circle/mark is the first subo throat (10)
position, the white circle mark is the position of the second spot (11),
Furthermore, as calculation conditions, for example, the focal length of the objective lens is 4 + nm, the first spot (lO) and the second spora)
The initial interval of (11) was set to 20 μm. As shown in Fig. 2, the rotation angle θ-Q mrad of the reflecting mirror (4)
(10) and (11) both have the same radial position, that is, the same recording track 1. However, when θ2≠Omrad, the two spots (10) and (11) are displaced differently in the radial direction, so it is possible to obtain the relative displacement in the radial direction. Therefore, by rotating the reflecting mirror (4), it is possible to accurately and easily adjust the positions of the two spots (10) (It) to the same recording track or to adjacent recording tracks. At this time, the two spots (10) and (11) are displaced in the radial direction as well as in the jitter direction, but even if the jitter is displaced in the jitter direction, it does not pose a problem in actual operation.

In the above embodiment, the reflecting mirror (4) is rotatable around two axes, but the following arrangement may be made. FIG. 3 shows a second embodiment, in which the reflection mirror (4) is rotatable around the y-axis.

Figure 4 shows the two spots (10) (1) in Figure 3.
1), and the calculation conditions are the same as in the case of FIG. 2. In Figure 4, there are two spots) (IQ
)(11) is different from that shown in FIG. 2, but since a relative displacement occurs in the radial direction, the same effect as in the first embodiment can be obtained.

Furthermore, the following configuration may be used. FIG. 5 shows a third embodiment, in which a first beam (8) and a second beam (9) from a two-beam semiconductor laser (1) are aligned in the y-axis direction. The reflective mirror (4) rotates around the Z axis or y
It is rotatable around the axis (in the jitter direction on the information recording medium surface).

Figure 6 shows how the two droplets (10) and (11) change when the rotation angle θ2 or θ is given to the reflecting mirror (4) in Figure 5. The changes in the case of the angle θ1 and the case of the rotation angle θa are approximately the same.

In other words, the centers of the two spots (lO) (11) are displaced by dl in the radial direction, and the two spots (10') (11) have an opening in the radial direction spanning d and t. arise. Figure 7 is a diagram showing the above d,,d, calculated under the same conditions as Figure 2, and shows the relative position between the two spots (10) and (11) depending on the rotation angles θ□ and θa. Since a displacement d2 in the radial direction occurs, the same effect as described above also occurs.

+U in the radial direction of the two spots (lO) (11)
A radial displacement can be obtained, but in addition to the necessary displacement, a similar displacement occurs in the radial direction or jitter direction. Although these displacements do not pose a big problem in practice, it is desirable that they be as small as possible.

Therefore, the fourth embodiment shown in FIGS. 8 and 9 below eliminates the above-mentioned unnecessary displacements and obtains only the necessary displacements, with reference numbers (1) to ( 11) is the same part as that in FIG.

(13) is the beam splitter (3) and reflection mirror (4)
A second reflecting mirror is disposed between the two mirrors and is rotatable around the Z axis. In FIG. 8, the first beam (8) and the second beam (9) from the two-beam semiconductor laser (1) are emitted so that they are within the Xy plane on the coordinate axes in the figure, and the first The reflecting mirror (4) is rotatable around the Z axis. On the other hand, in Fig. 9, two beams (8) (9) from a two-beam semiconductor laser (one
can be rotated so that it lies within the XZ plane.

Next, the operation will be explained. In the above-described embodiment, the second reflecting mirror (13) has two spots (10) and (11) that are originally required, in addition to the relative displacement in the radial direction. occur −
In order to maximize the effect, the rotation angle of the first reflecting mirror (4) in FIGS. 8 and 9 must be The second reflecting mirror (13) may be rotated by θ2/2 or θy/2 in conjunction with θ2 or θ. Figure 10 shows two spots (1
0) (11) is a diagram showing how the rotation angle θ8 changes.
Alternatively, only the required relative displacement in the radial direction is generated depending on θ. Note that the calculation conditions are the same as in the case of FIG.

As described above, according to the fourth embodiment, the rotatable second reflection mirror (13) is provided, and the second reflection mirror (4) is rotated in conjunction with the rotation of the first reflection mirror (4). By rotating the mirror (13) at an angle that is half the rotation angle of the first reflecting mirror (4), a relative displacement in the radial direction can be caused in the two spots (10) and (11). This makes it possible to accurately and easily adjust the positions of the two spots (10) and (11) to the same recording track or to adjacent recording tracks.

Note that the spot position adjustment described in each of the above embodiments is
This may be done as an initial adjustment when installing the multi-beam optical head into the destination disk device, or the tracking error signal of each spot may be detected while the optical disk device is in operation, and the servo mechanism may adjust each spot and recording track. It is also possible to always maintain a predetermined positional relationship.

Further, in the above embodiment, a two-beam multi-beam optical head is shown, but three or more beams may be used.

[Effects of the Invention] As is clear from the above description, in the present invention, the reflection mirror provided in front of the objective lens in the optical path can be rotated and adjusted, so that multiple spots can be accurately aligned to a predetermined recording track. It can be followed, has high reliability, and has the effect of improving mass productivity.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of essential parts of a first embodiment of the present invention, FIG. 2 is a line diagram showing the state of each spot on the surface of an information recording medium according to the first embodiment, and FIG. FIG. 4 is a line diagram showing the state of each spot on the information recording medium surface according to the second embodiment. FIG. 5 is a perspective view of the main part of the third embodiment. FIG. 6 is a diagram showing the state of each spot on the information recording medium surface according to the third embodiment, FIG. 7 is a detailed diagram, and FIGS. 8 and 9 are main parts of the fourth embodiment. A perspective view, FIG. 1O is a line diagram showing the state of each spot on the surface of an information recording medium according to the fourth embodiment, FIG. 11 is a perspective view of main parts of a conventional multi-beam optical head, and FIG. FIG. 3 is a partial perspective view showing the relationship between spots and recording tracks. (1)...2-beam (multi-beam) semiconductor laser,
(2)... Collimator lens, (3)... Beam splitter, (4) (13)... Reflection mirror, (5)...
Objective lens, (6)... Information recording medium, (10) (11)
)··spot. In each figure, the same reference numerals indicate the same or corresponding parts. Form 1 Figure 5:, Sentence 1-Things Renis 10, II: Spot Tofti'Riettce1

Claims (1)

[Claims] a multi-beam semiconductor laser having a plurality of light emitting sources;
A collimator lens converts the diverging light beam from the multi-beam semiconductor laser into a parallel light beam; a beam splitter separates the light beam irradiated onto the information recording medium from the reflected light from the information recording medium; In the multi-beam optical head, the multi-beam optical head includes a reflecting mirror for converting the direction of a light beam into a direction, and an objective lens for condensing and irradiating a light spot onto the information recording medium, the reflecting mirror disposed in front of the objective lens. A multi-beam optical head characterized by being rotatable.