JPH04162235A - Optical type apparatus for recording and reproducing information - Google Patents

Abstract

PURPOSE:To make it possible to obtain an optical head the whole of which is made small in size, by a construction wherein a light source and a means of generating one sub-beam at least are formed on the same base and a means of controlling the position of the sub-beam in relation to a main beam is formed on the same base. CONSTITUTION:A beam emitted from a semiconductor laser 1 is reflected by a prism 2 and applied to a reflection type diffraction grating 3. The diffraction grating 3 is an element for generating sub-beams by a three-beam method, for instance. A reflected beam is thereby divided into three beams and a main beam 5 is used for recording and/or reproduction of information, while sub- beams 6a and 6b are used for tracking servo. The diffraction grating 3 is so formed as to be rotatable around the axis of rotation passing through the center thereof substantially, and by the rotation of the grating, positions of the sub- beams 6a and 6b in relation to the main beam 5 are changed. According to this constitution, a small-sized and highly precise component can be manufactured and the whole of an optical head can be made small in size.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides information recording and/or recording using at least one main beam and at least one sub beam that irradiates an optical recording medium having at least one track. The present invention also relates to an optical information recording and reproducing device that performs reproduction.

[Conventional technology]

In recent years, there has been research into optical recording media such as compact discs, write-once optical discs, and rewritable magneto-optical discs, and optical information recording and reproducing devices that record and/or reproduce information on these media. Development is gaining momentum. Furthermore, research is being carried out on not only disk-shaped recording media but also card-shaped recording media.

In order to increase the recording capacity of such optical recording media, the distance between tracks is close to each other on the order of microns, and in order to accurately record and/or reproduce information, it is necessary to adjust the objective lens to the position of the target track. It is necessary to detect the positional deviation as a tracking error signal and perform tracking servo.

An example of a conventional tracking error signal detection method will be described below.

FIGS. 9(a) and 9(b) are partially enlarged views of the medium surface of the optical recording medium.

In the figure, reference numeral 30 indicates a track previously formed on the medium surface in the form of a groove or a band-like region having a different rate of reversal. Here, the three beam spots 31, 32, and 33 are irradiated so that the main beam spot 32 is in the center of the track 30, and the sub beam spot 3L 33 is in the middle of the track 30, and the directions are directed toward the arrows. Scan in the direction of. Then, a tracking error signal is derived by subtracting the detection signals obtained by detecting the reflected lights of the beam spots 31 and 33, respectively, and based on this signal, the beam spot 31.3 is determined at pz.
2. While controlling the irradiation position of 33, beam spot 3
In step 2, information 34 is recorded in the track 30 as shown in FIG. 9(a), or information 34 already recorded in the track 30 is reproduced as shown in FIG. 9(b).

In addition, as another technology, although not specifically explained using diagrams, two of the three beam substrates for trunking are used.
Japanese Patent Application No. 61-82928 proposes a method of performing tracking by irradiating parts of the two beam spots 31 and 33 so as to cover different tracking tracks.

However, with this method, when the positional relationship between the track and the three beam spots, that is, the attitude, shifts, the way the two sub beams are applied to the track changes, resulting in a change in the shape of the tracking signal. there is a possibility. For example, although the guide section of the rough access mechanism of the apparatus usually has high straightness, the posture of the recording medium and the optical head may change due to the precision of parts and assembly precision. In addition, in the case of a disk-shaped recording medium,
As shown in FIG. 10, if the trajectory St Sz of the optical head due to rough access does not pass through the center O of the disk and there is an offset d, then the inner circumference N+Nz of the disk and the outer circumference F, Fz are the radius of the track. Because of the difference in the tangential direction of the track (T, , -
T, , □, Tt1 T-z) will change. Therefore, 3 beams (T,,31+T,,:l□+TR33;
Even if there is no change in the attitude of Tfffl+Tts□, Tts3), the way the sub beam is applied to the track changes. Furthermore, due to the eccentricity of the disk, or in the case of a card-shaped recording medium, due to the skew of the card, a positional deviation occurs between the track and the spots of the three beams.

In such a case, there is an additional problem in that the characteristics of the tracking servo system tend to become even more unstable if there is an influence of disturbances such as noise or defects in the recording medium.

To solve these problems, for example, there is an actuator (grid driving means) disclosed in Japanese Patent Laid-Open No. 1-176335. As shown in FIG. 11, in this actuator, a piezoelectric element 41 that receives a drive signal from a grid drive circuit 40 expands and contracts depending on the strength of the voltage of this drive signal, and a projection 42 that is engaged with one end of the piezoelectric element 41 expands and contracts depending on the strength of the voltage of this drive signal. The diffraction grating holder 43 is rotated in the direction of the double arrow through the diffraction grating, and the diffraction grating 44 fixed to this holder is rotated, so that two of the three beams passing through this diffraction grating are centered around the main beam. It rotates to control how the sub-beam is applied to the track.

[Problem to be solved by the invention]

The method of using a piezoelectric element as shown in the conventional example described above has the problem that it is difficult to miniaturize the mechanism for rotating the diffraction grating, and the optical head becomes large. Also,
Since the piezoelectric element requires a high driving voltage, there are problems with the power supply and the like.Furthermore, since the element itself is fragile, there are problems such as being susceptible to impact. Further, even when piezoelectric elements are not used, it is difficult to miniaturize the rotation/adjustment mechanism with a normal structure, which poses a major obstacle to miniaturizing the drive section. Furthermore, the conventional configuration required assembly and adjustment, which was disadvantageous in terms of cost and accuracy.

In the present invention, an optical information recording/reproducing device using a plurality of beams has a means for controlling the position of the sub beam with respect to the main beam, and at the same time, the drive section thereof is miniaturized, thereby reducing the overall size of the optical head. The aim is to realize the following.

[Means and operations for solving the problems] In order to achieve the above object, the present invention forms a light source and a means for generating at least one sub-beam on the same substrate, and also provides a means for generating at least one sub-beam. By forming means for controlling the position of the sub beam relative to the main beam on the same substrate, it is possible to obtain a stable tracking error signal by controlling the position of the sub beam relative to the main beam. This makes it possible to form the control means using a method that applies semiconductor processes, making it possible to make small and highly accurate parts, making it possible to downsize the entire optical head, and furthermore, making it possible to create optical information recording and reproducing devices. It becomes possible to significantly shorten the assembly, adjustment, and other processes of the device, and it becomes possible to achieve higher precision and lower costs.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

The first part is a conceptual diagram showing an embodiment of the optical recording/reproducing apparatus of the present invention. In this figure, 1 is a semiconductor laser (light source), 2 is a prism, 3 is a reflection type diffraction grating, and 4 is a semiconductor substrate. The beam emitted from the semiconductor laser 1 is
The light is reflected by the prism 2 and irradiated onto the reflective diffraction grating 3. The diffraction grating 3 is an element for generating sub-beams in the three-beam method, and the reflected beam is divided into three.

The main beam 5 is for recording and/or reproducing information, and the sub beams 6a and 6b are for tracking servo.

As shown in the figure, the diffraction grating 3 is formed to be rotatable around a rotation axis passing through the center of the grating, and by this rotation, it is possible to change the position of the sub beam with respect to the main beam. be. An actuator for rotating the diffraction grating 3 is formed on the back side of the diffraction grating 3 in the figure (not shown in FIG. 1).

FIG. 2 is a partial plan view of this actuator (with the sacrificial layer shown in FIG. 3 removed), and FIG. 3 is a cross-sectional view thereof. This actuator can be formed on the silicon substrate 7 using a technique called micromachining that uses semiconductor processes such as polycrystalline silicon deposition and etching. The first embodiment of the reflection type diffraction grating driving actuator according to the present invention can be formed, for example, as follows.

An insulating layer 8 of a nitride film is formed on the silicon-based FiT, and a silicon dioxide layer 9a called a sacrificial layer is provided thereon in a shape as shown. A polycrystalline silicon layer is provided on this assembly in the shape shown in the figure to form a rotor 10 and a stator 11. After another silicon dioxide layer 9b called a sacrificial layer is provided on this assembly so as to have a shape as shown, a bearing 12, which is a holding member for the rotor 10, is formed. In the actuator having such a structure, after forming the diffraction grating as described below with reference to FIG. 4, the sacrificial layers 9a and 9b are removed together with the sacrificial layer 9c shown in FIG. Be able to rotate. As shown in FIG. 2, this actuator is composed of a 4-ball rotor 10 and an 8-ball stator 11. On the stator side, a set of two electrodes a and b are arranged for 4 m. For example, when voltage is applied to electrode a, electrostatic attraction is generated between it and the rotor 8, causing the rotor to rotate counterclockwise. rotate,
When voltage is applied to the electrodes, the rotor rotates clockwise.

Next, as shown in FIG. 4, a silicon dioxide layer 9c as a sacrificial layer is further provided on the actuator of FIG. It is provided so as to be connected to the polycrystalline silicon of the rotor 10. Next, a reflection type diffraction grating 14 is formed in the central flat portion of the polycrystalline silicon layer 13. This reflection type diffraction grating 14 can be formed, for example, as shown in FIG. 5(b) by covering the polycrystalline silicon layer 13 with a mask 15 and etching it as shown in FIG. 5(a). I can do it.

FIG. 6 shows a second embodiment of an actuator for driving a reflective diffraction grating according to the present invention. Since the required amount of angular displacement of the diffraction grating is not so large, it is not necessarily necessary to use a rotary actuator as shown in FIG. In this embodiment, the diffraction grating 16 is formed using a cantilever beam method, and a hinge 18 is formed on a cantilever beam 17 that is a supporting portion of the diffraction grating 16, so that the hinge 18 is used as the center of rotation. This cantilever beam 1
7 is integrally formed with a substrate (not shown). Furthermore, a comb-like actuator is used as the actuator. This includes comb teeth 19 formed integrally with the diffraction grating 16, and comb teeth shaped electrodes 20a formed integrally with the substrate.
and 20b, and when a voltage is applied to one of these electrodes, the comb teeth 19 are drawn between the comb teeth of this one electrode due to electrostatic attraction. This force causes the hinge 18
A moment centered at is generated, and the attitude of the diffraction grating 16 can be changed. In this embodiment, elastic deformation is used to change the posture, and the structure can be simplified compared to a rotary type.

In a third embodiment of the actuator for driving a reflective diffraction grating according to the present invention shown in FIG. 7, a reflective diffraction grating 24 is supported by two cantilevers 22a and 22b integrally formed on a substrate 21. There is. These two cantilevers 22a and 22b each have two hinges 23a,
24a, 23b, and 24b are formed. The actuator is similar to that shown in FIG. 6, and consists of comb teeth 25 integrally formed on the diffraction grating 24 and comb teeth shaped electrodes 26 integrally formed on the substrate 21. In this embodiment, there are two beams 22a and 22b, a substrate 21, a diffraction grating 24, and four hinges 23a and 23b.

24a and 24b constitute a four-bar link, and the center of rotation can be located near the center of the diffraction grating. Therefore, compared to the embodiment of FIG. 6 in which the center of rotation is at the position of the hinge 18, the amount of displacement of the movable part of the actuator (<the teeth 25) is suppressed to a small value, and the rotation angle of the diffraction grating is the same as that of FIG. It is possible to obtain

In a fourth embodiment of the actuator according to the present invention shown in FIG. 8, the diffraction grating 27 is circular, and the comb teeth 28 and the comb tooth-shaped electrodes 29a, 29b are located on concentric circles.

This structure allows the generated force to be used more efficiently as a moment.

In the above embodiments, a stable tracking error signal is obtained by making the sub beams applied to adjacent tracks constant, but the application of the present invention is not limited to this. For example, it can be applied to obtain a tracking error signal by wobbling the sub beam. It goes without saying that the present invention can be applied not only to those that use the sub-beam for tracking, but also to two-beam optical heads that enable simultaneous verification and multi-track reading, for example.

〔Effect of the invention〕

In the present invention, it is possible to obtain a stable tracking error signal by controlling the position of the sub-beam with respect to the main beam, and a method in which the sub-beam generating means and position control means are applied to a semiconductor process. Since it is possible to form the optical head with small size and high precision, it is possible to make the entire optical head smaller. Furthermore, by forming the optical element integrally with the substrate, the assembly, adjustment, and other processes of the optical information recording/reproducing device can be significantly shortened, and higher precision and lower costs can be achieved.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing an embodiment of an optical recording/reproducing apparatus according to the present invention; FIG. 2 is a partial plan view showing a first embodiment of an actuator used in the optical recording/reproducing apparatus according to the present invention; 3 and 4 are cross-sectional views showing the sequential manufacturing steps of the actuator shown in FIG. 2, FIGS. 5(a) and (b) are diagrams showing an example of forming a diffraction grating, and FIG. FIG. 7 is a partial perspective view showing a second embodiment of an actuator used in an optical recording/reproducing device according to the same technology. FIG. 7 is a partial perspective view showing a third embodiment of the same, and FIG. 8 is a fourth embodiment of the same. 9(a) and (b) are diagrams showing a method for recording and reproducing information on an optical recording medium. Figure 11 is a diagram for explaining the problems associated with recording and playback shown in ).
FIG. 2 is a sectional view showing a conventional actuator. 1... Semiconductor laser (light source) 2... Prism 3,
14.16.27...Reflection type diffraction grating 4.7.21.
・Board ・・Main beams 6a, 6b...
Sub-beam 8...Insulating layer 9a, 9b, 9
c...Sacrificial layer 10...Rotor 11...Stator 12...Hair ring 13...
Polycrystalline silicon layer 15...mask 17, 22a
, 22b--cantilever beams 18, 23a, 23b,
24a, 24b--hinge 19, 25.28...
Comb teeth 20a, 20b, 26a, 26b, 29a,
29b... Electrode FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, FIG. 7, FIG. 8, FIG. 9, and FIG. 10 S. Figure 11

Claims (1)

[Claims] 1. In an optical information recording and reproducing device that records and/or reproduces information using at least one main beam and at least one sub beam that irradiates an optical information recording medium having at least one track for recording information. , characterized in that a light source and a means for generating at least one of the sub-beams are formed on the same substrate, and a means for controlling the position of the sub-beam with respect to the main beam is formed on the same substrate. Optical information recording and reproducing device.