JPH04349221A - Optical head - Google Patents

Abstract

PURPOSE:To surely fix a mirror for raising the optical head and to prevent the generation of an unnecessary vibration and the deformation of a mirror surface. CONSTITUTION:A mirror 41 is fixed to a carriage 11a for directing a laser beam to an objective lens by bending a light path for the laser beam directed from a semiconductor laser. The reflecting surface of this raising mirror 41 is formed in nearly ellipse. This mirror 41 is fixed with adhesive to the surface area of an adjustment member 15 whose straight lines go through the centroid of the mirror 41, extend along the moving direction of the carriage 11a and cross each other. Further, the incline adjustment member 15 is fixed to the carriage 11a while adjusting the knob of the incline adjustment member 15.

Description

[Detailed description of the invention]

[Object of the invention]

0002

[Industrial Application Field] The present invention relates to an optical head.
In particular, the present invention relates to an optical head incorporated in an optical information recording/reproducing apparatus that reproduces or records information by irradiating an optical medium with a laser beam.

0003

2. Description of the Related Art In recent years, various optical recording media such as optical disks that can optically record information have been developed. 2. Description of the Related Art Recording and reproducing devices that optically record information on an optical recording medium and then reproduce the information are being actively developed, and improvements to the optical heads incorporated in these devices are also being actively pursued. Furthermore, various improvements have been made to methods for positioning and adjusting optical components, which are important in manufacturing such optical heads. For example, this type of optical head can be adjusted in two ways as described below.

FIG. 13 shows an optical system of a conventional optical head. In this optical head, diverging light emitted from a semiconductor laser 21 is collimated by a collimating lens 22 and converted into a parallel beam, and this parallel beam is focused onto an optical recording medium 25 by an objective lens 4. Between the objective lens 4 and the collimating lens 22, a raised mirror 20 such as a triangular prism for directing the parallel beam to the objective lens 4 and the optical recording medium 2 are provided.
A beam splitter 23 is arranged to separate the detection light beam reflected from the semiconductor laser 21 from the light beam directed toward the optical recording medium 25 from the semiconductor laser 21 . The light beam separated by the beam splitter 23 is directed to a photodetector 24 via a photodetection optical system 24a.

In the optical system shown in FIG. 13, a rising mirror 20 is mounted as shown in FIG. That is, the erected mirror 20 is fixed to a mirror stand 26, and this mirror stand 26 is fixed to a base 27 with fixing screws 29.
Fixed. In order to adjust the inclination of the mirror stand 26, three adjusting screws 28 are provided around the fixing screw 29. To adjust the optical system of such an optical head, first, the relative positions of the semiconductor laser 21 and the collimating lens 22 are adjusted in the X, Y, and Z directions shown in three-dimensional coordinates, and then the relative positions of the semiconductor laser 21 and the collimating lens 22 are adjusted in the The parallelism and exit direction of the subsequent light beam can be adjusted. At this time, the beam splitter 23
remains fixed. Next, the adjusting screw 28 shown in FIG. 14 is turned to adjust the tilt of the raising mirror 20 so that the optical axis H of the raising mirror 20 is approximately perpendicular to the optical recording medium 25. Furthermore, the objective lens 4
The optical axis of the objective lens 4 is aligned with the optical axis H, and the tilt adjustment is performed in the directions shown by arrows α and γ so that the aberration of the beam spot formed on the optical recording medium 25 is minimized. It will be done.

As described above, after the adjustment of the light emitting and focusing optical system is completed, the photodetection optical system 24a and the photodetector 24 are adjusted, and the adjustment of the optical head is completed.

FIG. 15 shows a separation optical system that is smaller and lighter, has improved productivity, can be driven at high speed without vibration or optical axis tilt, and is capable of recording and reproducing information at high speed. A configuration diagram of the head is shown. In such an optical head, an objective lens 4 that irradiates and focuses a light beam onto the surface of an optical recording medium is held by a focus actuator 1, and the objective lens 4 is moved in the optical axis direction by the focus actuator 1. Driven. The focus actuator 1 is integrally formed of resin with a linear motor 50 for driving the objective lens 4 in a direction perpendicular to the optical axis direction. In this structure, a central carriage 11a to strengthen the rigidity of the tracking coil 9 is formed into a cylindrical shape, and a cavity 11h is provided in the carriage 11a to allow the passage of a light beam. There is. Further, as shown in FIGS. 16 and 17, a rising mirror 31 is provided below the objective lens 4 and is bonded to the carriage 11a. An optical system, a fixed detection optical system for detecting a light beam, and an optical recording medium, ie, an optical disk, are optically coupled. The optical head is equipped with a light transmission optical system for transmitting the light beam to the optical recording medium 25, a detection optical system and a detector for detecting the light beam reflected from the optical recording medium. You can leave it there.

In the optical head constructed as described above, the inclinations of the rising mirrors 31 are adjusted to align the optical axes with each other by the following method.

An adhesive 30 is applied onto the mirror mounting surface 11i extending from the cavity 11h of the central carriage 11a, and a triangular prism-shaped raised mirror 31 is placed on the adhesive 30 layer. , the tilt of the rising mirror 31 is adjusted before the adhesive 30 is cured.

The reason why the adhesive layer 30 is interposed between the upright mirror 31 and the mirror mounting surface 11i is as follows.

The mirror 31 stands up on the mirror mounting surface 11i.
If the linear motor 50 is directly fixed with adhesive without being adjusted, the optical axis of the rising mirror 31 and the optical axis of the objective lens 4 may be It is difficult to match them completely. Therefore, by interposing the adhesive 30 between the two and adjusting the tilt of the rising mirror 31 in a predetermined direction before the adhesive 30 hardens, the tilt adjustment becomes easy and the rising mirror 31 is adjusted in a predetermined direction. -31 stable optical properties are achieved. In this way, in order to adjust the erecting mirror 31 to a predetermined position and inclination in advance, the surface of the erecting mirror 31 excluding the reflective surface 31a and the adhesive surface 31b is chucked at the time of bonding, and the erecting mirror 31 is retained.

As described above, the rising mirror 31 is arranged with a certain gap from the mirror mounting surface 11i formed integrally with the carriage 11a, and the adhesive 30 is flowed between the two. Fixed. This is because the tilt of the optical axis can be easily adjusted by interposing the adhesive 30 in the mounting gap and adjusting the tilt of the rising mirror 31 in a predetermined direction after the adhesive 30 hardens. .

[0013]

As shown in FIG. 14, in the method for adjusting an optical head in which the inclination of the rising mirror is adjusted to align the optical axis of the optical system, it is necessary to adjust the tilt of the rising mirror 20.
Since the optical axis H toward the objective lens 4 is tilted when adjusting the There is a problem that the number of man-hours is large. Further, when the optical axis H is tilted, there is also a problem that the end point position on the optical recording medium that can be read with respect to the optical head is shifted relative to the optical head.

In the method shown in FIG. 15, in order to adjust the upright mirror 31 to a predetermined position and inclination in advance,
The raising mirror 31 must be held in a certain position. For this holding method, directly stand up mirror
31 is held with strong force, but there is a problem in that holding with strong force distorts the mirror surface. Therefore, the surface opposite to the reflecting surface 31a of the rising mirror 31 is used as a chucking surface to hold the rising mirror during adhesion, and this surface is used as a chucking surface by suction using a vacuum pump or by using adhesive tape. King. In such a method,
There is a problem that chucking becomes unstable.

Furthermore, the entire surface of the upright mirror 31 is bonded to the mirror mounting surface 11i with an adhesive 30. Therefore, if an adhesive with low hardness is used, there are problems in that unnecessary vibrations such as tilt vibrations may occur, and the mirror surface may be distorted due to curing of the adhesive and thermal deformation after curing.

The present invention was made in order to eliminate the above-mentioned inconveniences, and its purpose is to securely fix the erecting mirror of the optical head, and to prevent the generation of unnecessary vibrations. Another object of the present invention is to provide an optical head that can prevent a mirror surface from being distorted.

[0017]

[Means for Solving the Problems] According to the present invention, in an optical head, a laser beam is raised by a mirror, the optical path is changed, and the laser beam is focused on an optical storage medium via an objective lens. An optical head characterized in that the upright mirror is adhesively fixed to a tilt adjustment member at a point on a straight line passing through its center of gravity, and a holding portion is provided on the tilt adjustment member.

Further, according to the present invention, in the optical head that raises a laser beam by a raising mirror, changes the optical path, and focuses the laser beam on an optical storage medium via an objective lens, the raising mirror An optical head is provided, characterized in that the mirror is an elliptical mirror.

[0019]

[Operation] With the above means, the problem of distorting the mirror surface is solved because the raised mirror is not directly held, and the tilt of the raised mirror can be adjusted while it is reliably chucked, making it easy to adjust the tilt. becomes possible.

Furthermore, by gluing the standing mirror at a point on a straight line that passes through its center of gravity, it is possible to suppress the center of gravity and suppress the occurrence of tilting vibrations of the mirror, and the bonding area is 1/2 of that when bonded on the mirror surface. Even if a low-grade adhesive is used, the mirror surface will not be distorted due to curing of the adhesive and thermal deformation after curing.

[0021] Since the elliptical mirror is manufactured by diagonally cutting a cylindrical glass rod, it is possible to obtain a mirror that is easy to manufacture and has a highly accurate end face shape. Further, by using an elliptical shape, it is possible to minimize the mass of the mirror with respect to the projected area in the X direction and to obtain a raised mirror that can increase the effective area.

Furthermore, by using an elliptical mirror, even if the light beam is deflected by an external vibration or the like and a part of the light beam having a circular cross section passes outside the reflecting surface of the elliptical mirror, the elliptical shape remains. The light beam reflected from the reflective surface of the mirror maintains a substantially circular cross section.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments of the optical head of the present invention will be described below with reference to FIGS. 1 to 12 and 15.

An optical head according to an embodiment of the present invention includes:
It has an optical system as shown in FIG. 3, and has substantially the same structure as the optical head shown in FIG. 15. Therefore, the structure will be explained with reference to FIG. 15 again. In the optical head of the present invention, a light beam from a light source, that is, a semiconductor laser 21 is converted into a parallel beam by a collimator lens 22, and the parallel beam is input to a beam splitter 23. A light beam having an elliptical cross section is converted into a circular light beam by a prism on the incident side of the beam splitter 23. The light beam that has passed through this beam splitter 23 passes through a beam shift correction plate 51 and is reflected by a galvanometer mirror 52 that is rotated around its axis as shown by arrow I. The light beam reflected by the galvanometer mirror 52 is directed toward a carriage 11a movably mounted on a guide rail (not shown). The parallel beam directed toward the carriage 11a passes through the resin cavity 11h of the carriage 11a, and is reflected by the upright mirror 41 fixed to the cavity 11a, as shown in FIG.
It is directed towards the objective lens 4. The parallel beam is focused onto an optical recording medium (optical disk) 25 by this objective lens 4. The diverging light beam reflected from the optical recording medium 25 is again converted into a parallel beam by the objective lens 4, reflected by the rising mirror 41, passes through the cavity 11h, and is again sent to the galvanometer mirror 52 and beam shifter. The light is returned to the beam splitter 23 via the correction plate 51. The reflected light beam from the optical recording medium 25 is reflected by the beam splitter 23, separated by a detection optical system 54 including a focus detection optical system, and detected by detectors 55, 56, and 57, respectively. Information recorded on the optical recording medium 25 is reproduced by processing the signal from the detection optical system 54. Further, a focus signal and a track signal are generated by processing detection signals from the detectors 56 and 57 in a focus and track detection circuit (not shown).

As shown in FIG. 15, a focusing coil 3 that is driven in response to a focus signal is fixed to a frame 2 to which an objective lens 4 is attached. It is supported movably along the optical axis of 4. Also,
A tracking coil 12 that is driven in response to a tracking signal is fixed in the cavity 11h, and fixed parts are provided at both ends of the tracking coil 12 to which rollers that roll on guide rails are fixed. There is. Although not shown, the area where the carriage 11a travels includes a focusing coil 3 and a tracking coil 1.
a focusing magnetic circuit and a tracking magnetic circuit that generate magnetic fields interlinked with the magnetic fields generated from the magnetic fields 2 and 2 to generate a driving force that moves the objective lens 4 along the optical axis and a driving force that causes the carriage 11a to travel along the guide rail; A magnetic circuit is provided. Therefore, the focusing coil 3 is driven in response to a focus signal from the focusing detection circuit, and the objective lens 4 is moved along the optical axis, so that the objective lens 4 is maintained in a focused state. the result,
The light beam from the objective lens 4 forms a minimum beam spot on the optical recording medium 25. Further, in response to a tracking signal from the track detection circuit, the tracking coil 12 is driven to move the carriage 11a, and the galvano mirror 52 is rotated by a small angle to direct the light beam reflected from the galvano mirror 52. is slightly changed. As a result, the objective lens 4 is maintained in the on-track state, and a desired tracking guide on the optical recording medium is tracked by the focused light beam from the objective lens 4. For details of the structure of the separating optical system shown in FIG. 15, please refer to Japanese Patent Application Laid-Open No. 3-98454.

In the present invention, a rising mirror 41 as shown in FIGS. 11 and 12 is employed in the structure of the separation optical system shown in FIG.
is attached within the carriage 11a as shown in FIGS. 1 and 2. That is, the raised mirror 41 is as shown in FIG.
As shown in the figure, a cylindrical glass rod 17 is prepared which is cut in advance so that the set surface is at the end in the longitudinal direction, and the glass rod 17 is sliced diagonally to produce the glass rod. Therefore, the raised mirror 41 has an elliptical columnar outer shape, and its reflective surface 41a is also formed substantially elliptical. As shown in FIGS. 1 and 2, this rising mirror 41 is
The cut surface is brought into contact with the base of the tilt adjustment member 15 as a reference surface 41b, and the back surface thereof is adhered to the slope surface 16 of the tilt adjustment member 15. Here, the upright mirror 41 is bonded to the tilt adjustment member 15 on a straight line passing through its center of gravity. Tilt adjustment member 15 to which a rising mirror 41 is fixed
is placed on the fixed part of the carriage 11a with a small gap, with its knob 15a held by a jig (not shown),
Adhesive 30 is poured between the two and solidified, thereby fixing the tilt adjustment member 15 to the carriage 11a. The raised mirror 41 is not limited to glass, and may be made of plastic such as resin. In this case, the raised mirror 41 is formed by direct injection molding without being cut out from the rod-shaped body.

When the inclination adjustment member 15 is fixed to the carriage 11a, a small gap is provided between the two, and this gap facilitates adjustment of the inclination adjustment member 15. That is,
Tilt adjustment member 15 equipped with an elliptical raised mirror 41
If the linear motor 50 is directly adhesively fixed to the carriage 11a without adjustment, the optical axis will be tilted with respect to the erecting mirror 41 due to variations in the assembly precision of the linear motor 50 or the precision of the parts of the linear motor 50. It is difficult to avoid this. Therefore, the adhesive 30 is interposed in the installation gap of the folding mirror 41, and the mirror is
Adjustment becomes easy by adjusting the inclination of 41 in a predetermined direction. Therefore, stable optical characteristics of the rising mirror 41 can be realized.

The reflecting surface of the rising mirror 41 is formed into an elliptical shape as described above, but this elliptical mirror 41 is different from a mirror having a rectangular reflecting surface as shown in FIG. As a result, the reflective surface of the mirror can be effectively utilized, and the weight of the mirror itself can be reduced. That is, as shown in FIG. 4, it is possible to reduce the mass of the mirror relative to the projected area in the X direction by the shaded area.

Furthermore, the light beam directed from the galvanometer mirror 52 to the rising mirror 41 is a parallel beam with a substantially circular cross section, but the beam spot B. S. The shape is formed into an ellipse that is substantially similar to the shape of the reflecting surface 41d of the rising mirror 41, as shown in FIG. When the galvanometer mirror 52 is slightly rotated in response to the tracking signal, the direction of the light beam is changed and the beam spot on the rising mirror 41 is slightly displaced. The beam spot is largely displaced due to poor adjustment of the optical system or vibrations caused by external disturbances, causing the beam spot to rise and cause the reflection surface 41d of the mirror 41 to rise.
In some cases, the light beam is directed outward, but even in such a case, the cross section of the light beam reflected from the rising mirror 41 is
A substantially circular beam spot is maintained on the optical recording medium. In other words, when the raised mirror has a rectangular reflecting surface as shown in FIG. 4, when a part of the light beam is directed outside the reflecting surface, a part of the ellipse will change as shown by diagonal lines in FIG. The missing light beam is reflected, and a perfectly circular beam spot is not formed on the optical recording medium, resulting in a tracking error being detected by the tracking detection system even though the track is in alignment. Furthermore, there is a possibility that an error may occur in the reproduced signal. On the other hand, when a part of the light beam is directed outside the reflective surface of the raised mirror 41 having an elliptical reflective surface as shown in FIG. 7, on the reflective surface 41d, As shown by diagonal lines, a beam spot approximately in the shape of an ellipse is formed, and a light beam having a substantially circular cross section is reflected onto the optical recording medium.

The reflective surface of the rising mirror 41 does not have to have an elliptical outer shape, but only the substantial reflective surface is elliptical. For example, as shown in FIG. 8, an elliptical reflective surface 41R is formed on a rectangular surface, and a non-reflective surface 41R is formed around it.
It may be coated with N. The mirror 41 shown in FIG. 8 can provide the function of an iris. That is,
When a light beam having a projected cross section larger than the elliptical reflecting surface 41R is incident on the rising mirror 41,
The light beam is vignetted on the non-reflective surface 41N and the reflective surface 41R of the lever
The reflected beam will have a circular cross section regardless of the cross-sectional shape of the incident light beam. In other words, the non-reflection surface 41N has a function as an iris, and has a function of shaping the cross-sectional shape of the light beam into a circle.

In the embodiment described above, the inclination adjusting member 15 to which the erecting mirror 41 is attached is adjusted in advance to a predetermined position and a predetermined inclination. In the structure shown in FIGS. 1 and 2, the knob 15 of the elliptical raised mirror 41 is
a is chucked, adhesive is applied to the area where a straight line passing through the center of gravity of the mirror 41 passes through the adjustment member 15, and the mirror 4
1 is fixed, and the bottom surface of the adjustment member 15 is glued to the fixed surface 16 of the carriage 11a so that the knob 15a is adjusted so that the mirror optical axis coincides with the moving direction of the carriage 11a, and the reflective surface 41a is adjusted to a predetermined position. Adjusted to have a tilt.

As described above, when adjusting the optical head, that is, adjusting the inclination of the erecting mirror 41 to align the optical axis, the erecting mirror 41 is preliminarily attached to the inclination adjustment member 15 provided with the knob 15a. is glued to. Therefore, when adjusting the inclination, the knob 15a can be reliably chucked without directly holding the mirror 41, thereby preventing distortion of the mirror surface caused by directly holding the mirror 41. It can be prevented.

Furthermore, the carriage 11a and the tilt adjustment member 1
Since the adhesive method uses an adhesive method in which the adhesive 30 flows into the gap between the adhesive 30 and the mirror 41 and hardens, adjusting the tilt of the mirror 41 to a predetermined position and inclination is possible before the adhesive 30 hardens. can be done reliably and easily.

Furthermore, since the upright mirror 41 is adhesively fixed to the mirror mounting surface on a straight line that passes through the mirror's center of gravity 14g and coincides with the moving direction of the mirror, the mirror can be moved quickly. Because the inertial force that is generated at the time passes through the bonding point and matches the reaction force that occurs at the bonding point in a straight line, rotational movement is difficult to occur, and abnormal vibrations may occur even if the bonding part does not have sufficient adhesive strength. do not have. Therefore, the adhesive area is less than 1/2 of the mirror surface, and even if adhesives with low hardness are used, unnecessary vibrations can be prevented. , an optical head that does not distort the mirror surface is realized.

Furthermore, since the elliptical raised mirror 41 is manufactured by cutting the cylindrical glass rod 17 diagonally,
A mirror with good manufacturability and high end face shape accuracy can be obtained, and at the same time, unnecessary parts can be omitted from the projected area in the X direction in the figure, and as a result, the weight of the raised mirror can be kept to a minimum. The effective area can be made sufficiently large.

Moreover, since the raised mirror 41 can be provided with a cut surface and the cut surface can be used as the reference surface 41b for positioning by abutting against the inclination adjustment member 15, easy and highly accurate assembly is possible. .

In the above embodiment, the shape of the mirror is an elliptical mirror manufactured by diagonally cutting the cylindrical glass rod 17 shown in FIG. The adhesion is adjusted so that the reflective surface has a predetermined inclination when attached to the adjustment member 15.
The present invention is not limited to this, and the shape of the mirror may be a triangular mirror 20 as shown in FIGS. 9 and 10.
5a may be provided on either a rectangular surface excluding the reflective surface 20a and the bonding surface 20b, or a set of triangular surfaces, and may be used as a chucking surface for holding the reflective mirror 20 during bonding.

[0038]

[Effects of the Invention] As explained above, in the present invention, when adjusting the optical head, the upright mirror is bonded in advance to the tilt adjusting member provided with the knob, so that when adjusting the tilt, Since the knob can be reliably chucked without directly holding the mirror, it is possible to prevent distortion of the mirror surface caused by directly holding the mirror. In addition, since we use an adhesive method in which adhesive flows into the gap between the structure and the tilt adjustment member and solidifies, it is recommended that the mirror be adjusted to a predetermined position and tilt before the adhesive hardens. , the tilt can be adjusted reliably and easily. Furthermore, since the upright mirror is bonded and fixed to the mirror mounting surface at a point on a straight line in the moving direction passing through the center of gravity of the mirror, the bonding area can be less than 1/2 of the mirror surface. Even if an adhesive with low hardness is used, unnecessary vibrations can be prevented from occurring, and the mirror surface will not be distorted due to curing of the adhesive and thermal deformation after curing.

Furthermore, since the elliptical raised mirror is manufactured by cutting a cylindrical glass rod diagonally, it is easy to manufacture and a mirror with high end face shape precision can be obtained.
The mass of the mirror relative to the projected area in the direction can be kept to a minimum, and the effective area can be increased.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a mounting structure of a rising mirror incorporated in an optical head according to an embodiment of the optical head of the present invention;

FIG. 2 is an enlarged cross-sectional view of a part of FIG. 1;

FIG. 3 is a schematic diagram showing an optical system of an optical head of the present invention incorporating the structure shown in FIGS. 1 and 2;

[Figure 4] Figures 1 and 2
A perspective view of a general reflective mirror shown for comparison with the elliptical raised mirror shown in

[Figure 5] Figures 1 and 2
A plan view showing a normal beam spot formed on the reflective surface of the elliptical raised mirror surface shown in

FIG. 6 is a plan view showing a beam spot formed on the reflective surface of the raised mirror surface shown in FIG. 4;

FIG. 7 is a plan view showing a beam spot formed on the reflective surface of the elliptical raised mirror surface shown in FIGS. 1 and 2;

FIG. 8 is a plan view showing a modified example of the raising mirror incorporated in the optical head of the present invention;

FIG. 9 is a side view showing another embodiment of the raising mirror incorporated in the optical head of the present invention;

FIG. 10 is a side view showing still another embodiment of the raising mirror incorporated in the optical head of the present invention;

FIG. 11 is a perspective view showing an example of a cylindrical member for manufacturing a raised mirror used in the optical head of the present invention;

[Figure 12] Figure 1
A perspective view showing an example of a raised mirror made from the cylindrical member shown in 1.

FIG. 13 is a diagram schematically showing the arrangement of the optical system of a conventional optical head;

FIG. 14 is a sectional view showing the mounting structure of the rising mirror shown in FIG. 13;

FIG. 15 is a perspective view showing an example of the structure of a separation optical head;

FIG. 16 is a sectional view showing the mounting structure of the rising mirror shown in FIG. 15;

FIG. 17 is an enlarged cross-sectional view of a part of the mounting structure shown in FIG. 16;

[Explanation of symbols]

4...Objective lens, 3...Focusing coil 11a... Carriage 12...Tracking coil, 15...Tilt adjustment member 15a... knob part 21... semiconductor laser, 25... optical recording medium, 30...adhesive, 41... Stand-up mirror, 41g...reflective surface.

Claims (2)

[Claims] 1. In an optical head that raises a laser beam with a raising mirror, changes the optical path, and focuses the laser beam on an optical storage medium via an objective lens, a straight line passing through the center of gravity of the raising mirror. An optical head characterized in that the above point is adhesively fixed to a tilt adjusting member, and a holding portion is provided on the tilt adjusting member. 2. An optical head that raises a laser beam by a raising mirror, changes the optical path, and focuses the laser beam on an optical storage medium via an objective lens, wherein the raising mirror is an elliptical mirror. An optical head characterized by: