JPH11353676A - Optical head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always perform an optimally tracking control with respect to the positional deviation due to an aging change, an environmental change, the skew of a medium or the like. SOLUTION: This optical head is provided with a first light source 1, a second light source 12, a reflection mirror part 16d which is arranged corresponding to the second light source 12 and which reflects a light beam emitted from the light source and which is supported rotatably in a direction in which an angle of reflection is changed, a galvano-mirror 16 being a first actuator for rotating the reflection mirror part 16d, an objective lens 9 irradiating a recording medium 10 with light beams from the first and second light sources and a second actuator 11 driving the objective lens 9 in a tracking direction and the relative tracking position control between irradiating light beams from the first and second light sources is performed by the galvano-mirror 16 and also the tracking control of all irradiating light beams to be irradiated with respect to the recording medium 10 is performed by the second actuator 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head used for an information recording / reproducing apparatus for recording / reproducing a recording medium such as a card-shaped recording medium or a disk-shaped recording medium.

[0002]

2. Description of the Related Art A conventional example of an optical head used in an information recording / reproducing apparatus is disclosed in, for example, Japanese Patent Application Laid-Open No. 6-28687. In this conventional example, two light sources that respectively irradiate a recording light beam and a reproduction light beam are used, and any one of two optical paths before the two light beams from the two light sources are combined. A wedge-shaped glass plate is inserted therein, and the relative position of the irradiation spots of the two light beams on the recording medium in the tracking direction is adjusted by rotating and adjusting the wedge-shaped glass plate.

[0003]

In the above conventional example, the relative position of the irradiation spot of the two light beams on the recording medium in the tracking direction is adjusted only at the time of assembling. In the case where the error occurs or a positional deviation such as a skew of the recording medium occurs, a deviation in the tracking direction occurs.

The present invention has been made in view of the above-mentioned problems, and provides an optical head capable of always performing optimal tracking control with respect to a positional change such as a temporal change, an environmental change, and a medium skew. The purpose is to do.

[0005]

In order to achieve the above object, an optical head according to claim 1 of the present invention is provided with a plurality of light sources and at least one of the plurality of light sources, the optical head being installed in correspondence with the plurality of light sources. A reflecting mirror that reflects the emitted light beam and is rotatably supported in a direction in which the reflection angle changes, a first actuator for rotating the reflecting mirror,
An objective lens for irradiating a light beam from the plurality of light sources to a recording medium, and a second actuator for driving the objective lens in a tracking direction, the first actuator irradiating light from the at least one light source and In addition to performing relative tracking position control between irradiation light from other light sources, tracking control of all irradiation light applied to the recording medium by the second actuator is performed. .

According to a second aspect of the present invention, in the optical head, the first actuator is provided with position detecting means for detecting a rotation position of a reflection mirror assembled to the first actuator. Features.

According to a third aspect of the present invention, in the optical head, the position detecting means includes a light emitting element fixed to a non-rotating portion of the reflection mirror and a plurality of divided light receiving elements, and the light is emitted from the light emitting element. The light beam reflected by the rotating portion of the reflection mirror is received by the plurality of divided light receiving elements.

According to the first aspect of the present invention, a light beam emitted from at least one of the plurality of light sources is reflected by a reflecting mirror installed corresponding to the light source, and the light beam is reflected from another light source. The recording medium is irradiated with the light beam by the objective lens. At this time, when the reflection mirror, which is rotatably supported in a direction in which the reflection angle changes, is rotated by a first actuator, irradiation light from the at least one light source and irradiation light from another light source are emitted. When the objective lens is driven in the tracking direction by the second actuator, the tracking control of all irradiation light applied to the recording medium is performed. Optimal tracking control is always performed irrespective of a change such as a change and a skew of the medium.

According to the second aspect of the present invention, the rotation position of the reflection mirror assembled to the first actuator is detected by position detection means.

According to the third aspect of the present invention, the position detecting means is constituted by a light emitting element fixed to the non-rotating portion of the reflection mirror and a plurality of divided light receiving elements. The reflected light reflected by the rotating portion of the reflection mirror is received by the multiple-divided light receiving element.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing an overall configuration of an optical system of an optical head according to a first embodiment of the present invention. 1 in the figure
Is a first light source, 2 is a first collimating lens that converts divergent light from the first light source 1 into parallel light, 3 is a reflection mirror,
Reference numeral 4 denotes a front monitor (PD) which guides a part of the light beam from the first light source 1 (light beam reflected by the reflection mirror 3) and functions as a light amount monitor. 5 denotes a linear polarization direction of the first light source 1. A half-wave plate rotated by 90 degrees, 6 is a diffraction grating for generating a tracking error detection spot, and 7 is a diffraction grating for generating a verify spot and a lead spot.

The light beam transmitted through the diffraction grating 7 is guided to the prism 8, reflected by the beam splitter surface 8a of the prism 8, and reaches the beam splitter surface 8b. Most of this light beam is reflected by the beam splitter surface 8b, guided to the objective lens 9, condensed into a minute spot by the objective lens 9, and irradiated onto the recording medium 10. At that time, the objective lens 9
Is finely driven by an actuator (second actuator) 11 for focusing and tracking,
This allows the objective emission light to follow a fixed position with respect to the displacement of the recording medium 10. The transmittance Tp and the reflectance Rs of the beam splitter surfaces 8a and 8b of the beam splitter 8 are set to, for example, Tp = Rs = 100% on the beam splitter surface 8a, and Tp = Rs = 50% on the beam splitter surface 8b. Shall be set to

After the light beam reflected by the recording medium 10 is guided again to the objective lens 9, a part of the light beam passes through the beam splitter surface 8b and is guided to the return optical system. This return optical system includes a condenser lens 17 for detecting a focus error signal by an astigmatism method and a concave cylindrical lens 18, and a light beam emitted from the return optical system passes through a reflection mirror 19. The light is guided to the photodiode 20.

On the other hand, the divergent light from the second light source 12
After being converted into parallel light by the collimating lens 13 of
The light is reflected by the reflecting mirror surface 16a of the galvanomirror (first actuator) 16. The reflected light passes through a diffraction grating 14 for generating a tracking error detection spot, and then passes through a diffraction grating 15 for generating a verify spot and a lead spot. The transmitted light is reflected by the total reflection surface 8c of the prism 8 and transmits through the beam splitter surface 8a, so that the light passes through substantially the same optical path as the light beam from the first light source.

FIG. 2 is a diagram showing one configuration example of the galvanomirror of the optical head according to the first embodiment. The galvano mirror 16 includes a reflection mirror section 16d having reflection mirror surfaces 16a and 16b, a front monitor (PD) 16c, and the like. An actuator mechanism including members 21a, 21b, and 22 to 24 described below is a reflection mirror. The portion 16d is rotatably supported in a direction in which the reflection angle changes. here,
For example, 95% of the parallel light 25 transmitted through the collimating lens 13 that converts the divergent light from the second light source 12 into parallel light is reflected by the reflecting mirror surface 16a of the galvanomirror 16,
It is assumed that the transmittance and the reflectance of the reflecting mirror surface 16a are set so that 5% is transmitted.

The transmitted light from the reflection mirror surface 16a passes through the reflection mirror surface 16b almost 100%, and then passes through a through hole 26a of a mirror holder 26 used to fix the reflection mirror portion 16d. The light beam passing through the through-hole 26a is applied to the front monitor (PD) 16 fixed to the yoke 22.
c and functions as a light amount monitor,
Are detected.

The reflecting mirror section 16d fixed to the mirror holder 26 is fixed to the yoke 22 via a hinge section 24, and is supported so as to be rotatable in the incident plane. The hinge 24 is made of an elastic member such as a resin. Since the coil 23 is wound around the mirror holder 26, the mirror holder 26 is rotatable in a direction in which the reflection angle changes according to the coil current by the magnetic flux of the magnets 21a and 21b.

FIG. 3 is a diagram showing another configuration example of the galvanomirror of the optical head according to the first embodiment. The galvanometer mirror 16 is obtained by changing the shape of the mirror holder 26 in the configuration example of FIG.
The position of 6d will also be changed. In FIG. 3, the entry of the front monitor (PD) 16c is omitted.

FIG. 4 is a diagram showing an example of a configuration in which a rotation position detecting mechanism of a reflection mirror unit is provided on a galvanometer mirror of the optical head according to the first embodiment. The rotation position detection mechanism includes a light emitting element 44 and a plurality of divided light receiving elements (two divided light receiving elements in this embodiment) 45a and 45b fixed to the yoke 22 which is a non-rotating part. This galvanometer mirror 16
Then, after the light beam emitted from the light emitting element 44 is reflected on the surface (upper surface in the drawing) of the mirror holder 26 which is a rotating portion,
The light is received by the two-segment light receiving elements 45a and 45b fixed to the yoke 22, which is a non-rotating part.
A differential signal of (signal from 5a)-(signal from 45b) gives a position signal of the reflection mirror unit 16d.

FIG. 5 is a diagram showing another configuration example in which the galvanomirror of the optical head according to the first embodiment is provided with a rotation position detecting mechanism for the reflection mirror unit. This rotation position detecting mechanism includes a light emitting element 46 and a plurality of divided light receiving elements (two-divided light receiving elements in the present embodiment) 47a and 47b fixed to the yoke 22 which is a non-rotating part. A certain mirror holder 26
, And a pin hole 49 is formed in the flag element 48. In the galvanometer mirror 16, a part of the light beam emitted from the light emitting element 46 passes through the pinhole 49 of the flag element 48 fixed to the mirror holder 26 which is a rotating part, and
Light is received at 7a and 47b, and a position signal of the reflection mirror unit 16d is obtained by a differential operation of (signal from 47a)-(signal from 47b) as in the above configuration example.

In the configuration example shown in FIG.
Although a pinhole is provided in 8, the flag element 48 may be provided without a pinhole, and the position signal of the reflection mirror section 16d may be obtained using vignetting by the flag element. In this embodiment, a galvanomirror is used as the first actuator. However, a tracking control may be performed using a piezoelectric element or the like instead. In this case, the control frequency cannot be set as high as that of a normal electromagnetic actuator, but is effective for low-frequency relative tracking control for correcting a deviation due to a change in environmental temperature or the like.

Next, the operation of the present embodiment will be described. FIG.
FIG. 3 is a diagram showing a spot arrangement when a light beam from a first light source 1 is irradiated on a recording medium 10 in the first embodiment. 7A to 7C respectively show a diffraction grating 7b for generating a lead spot (the diffraction grating 15b also has the same shape), a diffraction grating 6 for generating a tracking error detection spot, and a verifying spot. FIG. 9 is a diagram illustrating a shape of a grating surface of a diffraction grating 7a (the diffraction grating 15a also has the same shape) for generating the laser beam. In this case, the spot rows formed by the respective diffraction surfaces are 30
The zero-order light 33 on each diffraction surface is used as a recording spot and a spot for focus error signal detection. Note that a grating portion using SiO ₂ or the like is formed in each diffraction grating.

A spot 34 on the recording medium 10 shown in FIG.
Reference numerals a and 34c denote primary lights of the diffraction grating 7b in FIG. 7A, which are used for reproducing tracks adjacent to the recording tracks. The spots 34b and 34d are shown in FIG.
This is the secondary light of the diffraction grating 7b shown in (a) and is used for reproducing a track two tracks away from the recording track. The spots 35a and 35b are primary lights of the diffraction grating 6 shown in FIG. 7B, and are used for detecting a tracking error signal by the three-beam method by performing a differential operation of the reflected light amount of each spot. Can be Further, the spot 36a
Reference numerals 36b and 36b denote primary lights of the diffraction grating 7a in FIG. 7C, which are used to reproduce and verify pits immediately after recording.

In the case where reproduction and verification are performed simultaneously during recording, there arises a problem that a modulation signal of recording power is superimposed on the reproduction signal and the verification signal. The problem can be solved by employing a circuit for normalizing the reproduced signal and the verify signal using a forward monitor signal, a signal not subjected to pit modulation, and the like.

FIG. 8 shows the first light source 1 in the first embodiment.
FIG. 3 is a diagram showing a spot arrangement when a light beam from the light source and a light beam from the second light source 12 are simultaneously irradiated onto the recording medium 10, wherein a solid line indicates a spot formed by a light beam from the light source 1, 3 shows a spot by the light beam of FIG. In this case, the recording spot 33 corresponding to the first light source 1 is disposed on the track 38, and the recording spot 37 corresponding to the second light source 12 is disposed on the adjacent track 39.
By arranging in this manner, it is possible to continuously record two tracks at a time, and it is possible to improve the recording transfer rate to about twice that of the conventional case. This is advantageous because the time required for the process can be reduced to about half.

FIG. 9 is a view showing the arrangement of the light receiving portions of the photodiode 20 corresponding to the spot arrangement of FIG. The light receiving sections 40a to 40d shown in FIG. 9 are used to receive the spot 33 in FIG. 8, and {(signal from 40a) + (signal from 40c)} − ｛(signal from 40b) + (signal from 40d) ) By calculating｝, a focus error signal from the first light source 1 is obtained. Similarly, the light receiving portions 41a to 41d shown in FIG. 9 are used for receiving the light of the spot 37 in FIG. 8, and {(signal from 41a) + (signal from 41c)}.
By calculating − {(signal from 41b) + (signal from 41d)}, a focus error signal by the second light source 12 is obtained.

Since only one actuator for driving the objective lens in the focus direction is used in the present embodiment, either one of the two types of focus error signals is used, or an average of two is used. And the like can be used with arbitrary weighting. In addition, recording is performed using one of the two light sources,
When reproducing with the other light source, the focus error signal of the recording light source is used when importance is placed on the recording accuracy, and the focus of the reproduction light source is used when it is desired to remove the influence of disturbance to various servo systems during recording. An error signal may be used, and selection can be made according to the situation.

Further, the light receiving portions 42a, 42b,
43a and 43b are used for detecting a tracking error signal. That is, the tracking error signal TE1 of the spot of the first light source 1 is obtained by a differential operation of TE1 = (signal from 42a) − (signal from 42b),
Tracking error signal T of the spot of the second light source 12
E2 is obtained by a differential operation of TE2 = (signal from 43a) − (signal from 43b).

The tracking error signal TE1 is fed back to an actuator 11 for driving the objective lens 9 shown in FIG. 1 through a first servo circuit, which will be described later, whereby the first light source 1 and the second light source 12
The tracking control of the spot on the recording medium 10 is performed. Here, when a relative optical axis shift occurs between the irradiation light from the first light source 1 and the irradiation light from the second light source 12, the spot of the first light source 1 is accurately controlled by the tracking control. However, the tracking of the spot of the second light source 12 is caused by the relative optical axis shift. In order to solve this problem, the tracking error signal TE3 corresponding to the relative tracking deviation is set to TE3 = TE2
The difference may be obtained by a differential operation of −TE1 and fed back to the galvanometer mirror 16 shown in FIG. 1 via a second servo circuit described later.

FIG. 10 is a block diagram showing the configuration of the servo circuit used in the first embodiment. The servo circuit includes a differential amplifier 51 that performs a differential operation for obtaining a tracking error signal TE1, a phase compensator 52 that performs phase compensation on the tracking error signal TE1 input from the differential amplifier 51, A second servo circuit 54 including a driver 53 for driving the second actuator 11 based on the output signal of the detector 52, a differential amplifier 55 for performing a differential operation for obtaining a tracking error signal TE2,
A differential amplifier 56 for performing a differential operation for obtaining the tracking error signal TE3, a phase compensator 57 for performing phase compensation on the tracking error signal TE3 input from the differential amplifier 56, and an output signal of the phase compensator 57 And a first servo circuit 59 composed of a driver 58 for driving a first actuator (galvanometer mirror) 16 based on the above.

In the first embodiment, the recording spots are arranged and fixed on the adjacent tracks. Alternatively, the track intervals may be changed and controlled by an arbitrary number of tracks at any time. It is. In this case, it is assumed that the area of the light receiving portion of the photodiode for the second light source in FIG. 9 is enlarged in advance according to the track movement range.

In the first embodiment, the number of light sources is two. However, a similar configuration can be realized even when three or more light sources are used.

It should be noted that the present invention is not limited to the above-described one, and various modifications or changes can be added. For example, the present invention may be configured as in the following additional items. A plurality of light sources, and a reflecting mirror installed corresponding to at least one of the plurality of light sources and reflecting the light emitted from the light sources and supported rotatably in a direction in which the reflection angle changes, A first actuator for rotating the reflection mirror, an objective lens for irradiating light rays from the plurality of light sources to a recording medium, and a second actuator for driving the objective lens in a tracking direction, The first actuator performs relative tracking position control between the irradiation light from the at least one light source and the irradiation light from the other light sources, and controls all of the irradiation of the recording medium by the second actuator. An optical head for performing tracking control of irradiation light (Additional Item 1). 2. The optical head according to claim 1, wherein the first actuator includes a position detecting unit that detects a rotation position of a reflection mirror assembled to the first actuator. ).

The position detecting means is a plate-like flag element having a light emitting element and a plurality of divided light receiving elements fixed to a non-rotating part of the reflecting mirror and a pinhole fixed to a rotating part of the reflecting mirror. 3. The optical head according to claim 2, wherein a light beam emitted from the light emitting element is received by the plurality of divided light receiving elements via a pinhole of the plate-shaped flag element. Appendix 3). The position detecting means is composed of a light emitting element and a multi-split type light receiving element fixed to a non-rotating part of the reflection mirror and a plate-like flag element fixed to a rotation part of the reflection mirror,
3. The optical head according to claim 2, wherein a light beam emitted from the light emitting element is vignetted at a tip end of the plate-shaped flag element to be received by the multi-segmented light receiving element. Item 4). Generating a third tracking error signal by performing a differential operation between the first tracking error signal and the second tracking error signal;
2. The optical head according to claim 1, wherein the feedback of the third tracking error signal to the first actuator performs relative tracking error position control of one irradiation light and the other irradiation light. Appendix 5).

[0035]

As described above, according to the present invention,
Since the relative position in the tracking direction of the irradiation spot of two light rays of the light rays from the plurality of light sources on the recording medium is continuously controlled, environmental change such as temporal change, temperature, etc.
Optimal tracking control can always be performed with respect to misalignment such as skew of the medium. In addition, since a plurality of recording light sources are controlled simultaneously, the recording transfer rate is improved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an overall configuration of an optical system of an optical head according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration example of a galvano mirror of the optical head according to the first embodiment.

FIG. 3 is a diagram illustrating another configuration example of the galvanomirror of the optical head according to the first embodiment.

FIG. 4 is a diagram illustrating an example of a configuration in which a rotation position detecting mechanism of a reflection mirror unit is provided on a galvano mirror of the optical head according to the first embodiment.

FIG. 5 is a diagram illustrating another configuration example in which a rotation position detection mechanism of a reflection mirror unit is provided on a galvanomirror of the optical head according to the first embodiment.

FIG. 6 is a diagram illustrating a spot arrangement when a recording medium is irradiated with a light beam from a first light source in the first embodiment.

FIGS. 7 (a) to 7 (c) show the grating planes of a diffraction grating for generating a lead spot, a diffraction grating for generating a tracking error detection spot, and a diffraction grating for generating a verifying spot, respectively. It is a figure showing a shape.

FIG. 8 is a diagram showing a spot arrangement when light beams from first and second light sources are simultaneously irradiated on a recording medium in the first embodiment.

FIG. 9 is a diagram showing a light receiving portion arrangement of a photodiode corresponding to the spot arrangement of FIG. 8;

FIG. 10 is a block diagram illustrating a configuration of a servo circuit used in the first embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st light source 2 1st collimating lens 3 reflection mirror 4 forward monitor (PD) 5 1/2 wavelength plate 6, 7, 14, 15 diffraction grating 8 prism 8a, 8b beam splitter surface 8c total reflection surface 9 objective lens DESCRIPTION OF SYMBOLS 10 Recording medium 11 Actuator (2nd actuator) 12 2nd light source 13 2nd collimating lens 16 Galvano mirror (1st actuator) 16a, 16b Reflection mirror surface 16c Front monitor (PD) 16d Reflection mirror part 17 Light collection Lens 18 Concave cylindrical lens 19 Reflection mirror 20 Photodiode

Claims (3)

[Claims] 1. A plurality of light sources, and a plurality of light sources, which are installed corresponding to at least one of the plurality of light sources, reflect light emitted from the light sources, and are supported rotatably in a direction in which a reflection angle changes. Reflecting mirror, a first actuator for rotating the reflecting mirror, an objective lens for irradiating a light beam from the plurality of light sources to a recording medium, and a second actuator for driving the objective lens in a tracking direction And the first actuator performs relative tracking position control between irradiation light from the at least one light source and irradiation light from another light source, and controls the recording medium by the second actuator. An optical head characterized in that tracking control of all irradiation light to be irradiated is performed. 2. The light according to claim 1, wherein said first actuator comprises a position detecting means for detecting a rotational position of a reflection mirror assembled to said first actuator. head. 3. The position detecting means comprises a light-emitting element fixed to a non-rotating portion of the reflection mirror and a plurality of divided light-receiving elements, and a light beam emitted from the light-emitting element is turned by a rotation portion of the reflection mirror. 3. The optical head according to claim 2, wherein the reflected light is received by the plurality of divided light receiving elements.