JPH031331A - Optical head device - Google Patents

Abstract

PURPOSE:To improve a transfer rate by irradiating a prism mirror arranged in a rotary body, with the plural number of beam white rotating the beam synchronously with the rotation of the rotary body and scanning a tape arranged around the rotary body, by reflected beam. CONSTITUTION:A regular rectangular cone-shaped prism mirror 10 is arranged on the rotary shaft of a rotary drum 5 and in an upper direction, a rotary panel 11 is arranged so as to be coaxial with the rotary drum 5. On an lower surface, an optical system 100' is arranged at the intervals of 90 deg. on the same circumference. In the rotary drum 5, four transmitting holes 13 are arranged on circumferential surfaces facing to the four reflecting surfaces of the prism mirror 10 and an objective lens 14 is arranged in an internal part. The rotary panel 11 is rotated and driven at the same speed while matching a phase to the rotary drum 5. Accordingly, the incidental points of the respective beam are always same on the reflecting surface of the mirror 10 and each time the rotary drum 5 is once rotated, four tracks are scanned by the respective beam. Thus, the transfer rate can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to a so-called helical scan type optical head device.

(b) Conventional technology As an optical head device using a helical scan method, for example, Japanese Patent Application Laid-Open No. 149036/1983 (GllB 7/O
85). An example of this type of device is shown in the 8th section.
As shown in the figure. In the figure, (1) is a laser diode,
(2) is a beam splitter, (3) is a collimator lens, and (4) is a photodetector. These optical systems (10
0) is located outside the rotating drum (5). or,
(6) is a motor that drives the rotating drum (5), (7) is a reflecting prism arranged on the rotation axis of the rotating drum (5),
(8) is an objective lens that focuses the reflected beam from the reflection prism (7) onto the tape (9).

In such a conventional device, the optical system (100) is mounted on a rotating drum (
5), the shape of the rotating drum (5) can be reduced in size, and furthermore, the wiring for the laser diode (1) and the detector (4) can be simplified.

Incidentally, in optical-radical devices, it is desired to record a large amount of information and to increase the transfer rate of information. here,
The recording density of information is approximately determined by the wavelength of the laser beam used, so when increasing the transfer rate,
The usual method is to increase the scanning speed of the beam. However, even in such a method, the scanning speed of the beam cannot be increased indefinitely, for example, because there is a limit to the writing speed of the tape material itself.

(c) Problems to be Solved by the Invention The present invention seeks to provide an optical head device that can improve the transfer rate.

(d) Means for Solving the Problems In view of the above problems, the present invention aims to irradiate a beam onto a mirror means disposed on a rotating body so that its slope opposite to the plane of rotation is inclined, and to use the reflected beam to An optical head device for scanning a tape placed around a body is characterized in that a plurality of the beams are provided and a beam rotation means is further provided for rotating the beams in synchronization with the rotation of a rotating body.

(e) Operation By using a plurality of beams to scan the tape, each beam can scan a plurality of tracks per revolution of the rotating body (rotating drum). However, in this case, if each beam is simply made incident on the mirror means, the beams scanning the tape will intersect in the middle as the rotating body rotates. For example, in the case shown in Fig. 9, when the rotating drum (5) rotates from the state shown in Fig. 9 (a) and reaches the state shown in Fig. 9 (b), the beam (
B) Since the incident points of (B, ) are interchanged in the vertical direction, the scanning locus of the beam on the tape becomes as shown in FIG.

According to the present invention, the beams are rotated by the beam rotation means in synchronization with the rotation of the rotating body, so that the incident points of each beam on the reflecting surface of the mirror means are always at the same position.

(f) Examples Examples of the present invention will now be described with reference to FIGS. 1 to 3. Incidentally, in this figure, the same parts as those in FIG. 8 used in the conventional example are given the same reference numerals and explanations are omitted. In this embodiment, four optical systems outside the rotating drum used in the conventional example are provided, and the optical tape is scanned with four beams.

In FIG. 1, (10) is a prism mirror in the shape of a regular square pyramid, which is disposed on the rotation axis of the rotating drum (5). Further, a rotating plate (11) is disposed above the rotating drum (5) so as to be coaxial with the rotating drum (5), and an optical system (100° )(100
'') (100') (100') are arranged on the same circumference at 90° intervals (see the top view of the rotating plate (11) shown in Figure 2). (5) includes four reflective surfaces (12) of the prism mirror (10).
(12) (12) Four through holes (13) (13) (13) (13) are arranged on the peripheral surface opposite to (12),
Objective lenses (14) (14) (14) (14) are arranged inside these through holes (113) (13) (13) (13). The rotating plate (11) is connected to each optical system (100°)
(100') (100') The beam from (100') is reflected by each reflecting surface (12) (12) of the prism mirror (10).
)(12) (12), and is rotated at the same speed and in phase with the rotating drum (5) so that the reflected beam is guided to the corresponding objective lens.

According to this embodiment, each beam scans the tape with a phase difference of 90° as the rotating drum (5) rotates, as shown in FIGS. 3(a) and 3(b). ) can scan four tracks with each beam. Therefore, when the rotating drum rotates at the same speed, it is possible to achieve a transfer rate four times that of an optical head device that scans the tape with a beam.

FIG. 4 is a diagram showing another embodiment of the present invention, in which each optical system (
100°) (100°) (100') (100°
) to each reflective surface (12) (1) of the prism mirror (10)
2) Three beams are made to enter each of (12) and (12). According to this embodiment, it is possible to simultaneously scan three tracks with three beams emitted from one optical system, and therefore, one
Twelve tracks can be scanned per revolution.

Therefore, according to this embodiment, it is possible to achieve a transfer rate three times higher than that of the previous embodiment, and furthermore, compared to the conventional example, a transfer rate of 1
Double the transfer rate can be achieved.

FIG. 3 is a diagram showing still another embodiment of the present invention. In this embodiment, instead of rotating the beam emitted from the optical system, an image rotating prism for rotating the beam is arranged between the optical system and the reflecting prism. The image rotating prism (15) is arranged to rotate about the rotation axis of the rotating drum (5) and is rotated in the same direction as the rotating drum (5). With this configuration, each beam is always incident on the same position with respect to the reflecting surface of the reflecting prism (7).

This principle will be explained using FIG. 6.

This figure shows the image rotation prism (]B5 and the reflection prism (7) viewed from above, and the upper surfaces of both prisms are 2
The one with heavy edges will be more expensive. Suppose now that we focus on the beam (B,). The beam (B) enters the image rotating prism (15) from the (0) mark and exits from the X) mark. Therefore, the beam (B1) is reflected by the reflecting prism (7
) is incident at the (x) mark. It is assumed that both prisms (7) and (15) are rotated clockwise from FIG. 13A and reach the states shown in FIG. Along with this rotational movement, the image rotating prism (1) of the beam (B)
The input point and the exit point for 5) move along the dotted line loci shown in FIGS. 5(b) and 5(c). That is,
The entrance point rotates counterclockwise around the rotation axis (1), and the exit point rotates clockwise around the sleeve (2). Further, the rotational speed of each point is equal to the rotational speed of the image rotating prism (15).

Now, the image rotation prism (15) of the beam (B1)
Considering the emission point for the image rotation prism (15), this emission point rotates on the image rotation prism (15) in the same direction and at the same speed as the image rotation prism (15) as described above. Furthermore, since the image rotating prism (15) itself is rotating, the emission point rotates around the axis (2) with respect to the ground at twice the speed of the image rotating prism (15). The reflecting prism (7) is an image rotating prism (15) with respect to the ground.
), the output point ends up rotating in the same direction and at the same speed as the reflecting prism (7).

As described above, the beam (B,) is rotated in synchronization with the rotation of the rotating drum (5), so that the beam (B,) is always incident on the same portion of the prism mirror (7). Also, based on the same principle, the beam (B,) is also incident on the same portion of the prism mirror (7). The beam (B,) is an image rotation pnosm (15)
Since the beam (Bt) is incident on the image rotating prism (15) coincident with the rotation axis of the beam (Bt), it is not rotated with the rotation of the image rotating prism (15). ), so it also coincides with the rotation axis of the beam (B,
) to the prism mirror (7) also does not change.

As described above, according to this embodiment, each beam can be rotated at the same speed and in the same direction as the rotating drum (5) by the action of the image rotating prism (15), so each beam can be rotated by the reflecting prism (15). 7), so that the reflected beam from the reflecting prism (7) can always be emitted from the side surface of the rotating drum (5) in the same state. Therefore, the scanning axes traces do not intersect when scanning the tape, and each beam scans the tape in the seventh direction.
As shown in the figure, diagonal scanning is possible.

In this embodiment, since there is no need to rotate the optical system including the electric circuit system such as the laser diode and photodetector, the connection between the internal circuit system and the electric elements in the optical system is simpler than in the previous embodiment. It can also have the effect of being able to do things differently.

In this embodiment, three beams are used as scanning beams, but it is also possible to use more multi-beams.

(G) Effects of the Invention As described above, according to the present invention, it is possible to scan a plurality of tracks per revolution of one rotating body (rotating drum), so the data transfer rate can be significantly improved.

[Brief explanation of drawings]

Fig. 1 is a side sectional view showing an embodiment of the present invention, Fig. 2 is a bottom view of a rotary plate according to the embodiment, and Figs. Figure 4 is a top view of main parts of another embodiment;
Figures 5(a) and 5(b) are side views of other main parts, and Figure 6(a).
)(b)(c) are top views of essential parts of the same embodiment, FIG. 7 is a diagram showing the scanning locus of the tape according to the same embodiment, FIG. 8 is a side sectional view showing the conventional example, and FIGS. 9 and 7J10. The figure is a diagram showing an example in which a multi-beam is applied to a conventional example, and a diagram showing a tape scanning locus at that time. (7), (10)...Reflecting prism, prism mirror (mirror means) (11), (15)...Rotating plate, image rotating prism (beam rotating means)

Claims (1)

[Claims] (1) In an optical head device that irradiates a beam onto a mirror means disposed on a rotating body so that the reflective surface is inclined with respect to the rotating plane, and scans a tape placed around the rotating body with the reflected beam. . An optical head device comprising a plurality of beams and a beam rotation means for rotating the beams in synchronization with the rotation of a rotating body.