JP2002367214A - Variable shape mirror and optical disk information input / output device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information input and output device equipped with an optical pickup device having a shape variable mirror capable of correcting the aberrations of a laser beam. SOLUTION: This device has the shape variable mirror which has one or plural piezoelectric elements deformed by each of the piezoelectric elements by the control voltage impressed to the electrodes for the plural piezoelectric elements and is controlled in the shape of a mirror finished surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information input / output device provided with a variable shape mirror having a variable mirror surface and an optical pickup device.

[0002]

2. Description of the Related Art Generally, information storage devices using optical disks include CDs and DVDs. Since DVDs and the like have a higher recording density than CDs, the conditions for reading and writing information are becoming more stringent. For example, it is ideal that the optical axis of the optical pickup device is perpendicular to the disk surface, but in reality, the optical disk is made of resin, so it has a considerable undulation. The disk surface is not always vertical, and the disk surface may have an inclination with respect to the optical axis (hereinafter, the inclination of the disk surface with respect to the optical axis is referred to as tilt). Also, in the optical disk, as shown in FIG. 18, since the recording layer 108 has the resin layer 102a interposed, when the tilt, that is, the disk surface is tilted, the optical path of the laser beam is bent and coma is generated.
As shown in 103a and 103b, the spot cannot be correctly focused on the disk. If the coma aberration is larger than the allowable amount, a problem that reading and writing cannot be performed correctly occurs. As a means for reducing the aberration caused by the tilt, there is a method of reducing the thickness of the resin layer between the objective lens and the recording layer. Actually, in a DVD as shown in FIG. 18B, the objective lens 101b and the recording layer 1
The reason why the thickness of the resin layer 102b is smaller than that of the CD shown in FIG. 18A by half is to reduce coma aberration. However, in this method, if the recording density is to be made higher than that of a DVD, the resin layer is further thinned to reduce the influence of tilt. Can not read and write correctly. For this reason, the present situation is that the optical axis side is inclined by an actuator. As a means for optically correcting the tilt, there is a method using a liquid crystal plate described in JP-A-10-79135 as shown in FIG.

As means for correcting coma caused by tilt using a piezoelectric element, Japanese Patent Application Laid-Open No.
A method using a transparent piezoelectric element in the optical path of laser light described in US Pat.
A method using a deformable mirror using a plurality of actuators described in 3274 has been proposed.

[0004]

However, in the method of correcting the coma aberration by controlling the phase using a liquid crystal plate as disclosed in JP-A-10-79135, the amount of light is attenuated because the laser passes through the liquid crystal plate. It is difficult to obtain the energy required for writing, and from the characteristics of the liquid crystal,
In particular, it seems difficult to use it for high-frequency operation required for tangential tilt control.

Further, a high voltage is actually required to obtain a required thickness change with a single transparent piezoelectric element as disclosed in Japanese Patent Application Laid-Open No. 5-144056, which is not practical for use in an optical pickup device or the like.

Further, in the method of controlling the phase by deforming the mirror itself of the deformable mirror with a laminated piezoelectric element as disclosed in Japanese Patent Application Laid-Open No. 5-333274, wiring and the like are taken into consideration when used for small components such as an optical pickup device. Not so complicated, and the assembly cost is high. Further, even if the problems such as wiring can be solved, it is difficult to reduce the size of the multilayer piezoelectric element both technically and costly.

In order to solve the problems of the inventions described in these publications, a wavefront aberration (mainly coma) generated by a tilt of a disk surface or the like is corrected by a unimorph or bimorph shape deformable mirror using a piezoelectric element. There is a way to do it.

However, when the mirror surface is deformed, simply attaching the piezoelectric element to the mirror surface causes the mirror surface displacement of the portion where the mirror is fixed to be close to zero, so that the mirror surface shape is generated by tilt or the like. It is difficult to approach a shape that corrects aberrations that occur. In addition, it is very difficult to bring the initial shape closer to an ideal plane before deforming the mirror surface into a mirror shape that corrects aberration due to tilt or the like, that is, it is very difficult to calibrate the mirror shape.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to make a mirror surface of a deformable mirror close to a shape for correcting aberration due to tilt and the like and to make an initial shape of the mirror surface close to an ideal plane. It is an object to provide a deformable mirror that is possible.

A further object of the present invention is to provide an optical information input / output device provided with an optical pickup device having a deformable mirror capable of correcting laser beam aberration.

[0011]

According to the first aspect of the present invention,
In an optical disk information input / output device including an optical pickup device, the optical pickup device includes a deformable mirror having a variable mirror surface for controlling aberration of laser light, and the deformable mirror includes one or more piezoelectric elements. Wherein the shape of the mirror surface of the deformable mirror is controlled based on the deformation of the piezoelectric element.

According to the first aspect of the present invention, there is provided an optical pickup device capable of correcting aberration of laser light by a deformable mirror whose mirror surface shape is controlled based on deformation of one or a plurality of piezoelectric elements. An optical information input / output device can be provided.

According to a second aspect of the present invention, in the optical disk information input / output device according to the first aspect, the shape variable mirror is
It has a plurality of piezoelectric element electrodes, and the piezoelectric element is deformed for each piezoelectric element electrode by a control voltage applied to the plurality of piezoelectric element electrodes.

According to the second aspect of the present invention, a plurality of electrodes for the piezoelectric element are appropriately installed on the piezoelectric element of the deformable mirror, and the piezoelectric element is deformed for each electrode for the piezoelectric element, so that the aberration of the laser beam is improved. Optical information input / output device provided with an optical pickup device that satisfactorily corrects the above.

According to a third aspect of the present invention, in the optical disk information input / output device according to the second aspect, a piezoelectric element corresponding to the piezoelectric element electrode, wherein adjacent piezoelectric elements are deformed in opposite directions. A control voltage is applied to the plurality of piezoelectric element electrodes.

According to the third aspect of the present invention, by applying a control voltage to the plurality of piezoelectric element electrodes so that adjacent piezoelectric elements are deformed in the opposite direction, the vicinity of the end of the deformable mirror can be obtained. The displacement of the mirror surface shape crosses zero, and aberration correction near the end of the mirror surface becomes possible.

According to a fourth aspect of the present invention, in the optical disk information input / output device according to the second or third aspect, the plurality of electrodes for the piezoelectric elements are controlled to have the same control voltage or alternately opposite signs in the order in which they are adjacent to each other. It is characterized by applying a voltage.

According to the fourth aspect of the present invention, the same control voltage or a control voltage having an opposite sign is alternately applied to a plurality of piezoelectric element electrodes in the order in which they are adjacent to each other, so that the vicinity of the end of the deformable mirror can be improved. Thus, the displacement of the mirror surface can be zero-crossed, and the aberration can be favorably corrected near the end of the mirror surface.

According to a fifth aspect of the present invention, in the optical disk information input / output device according to the second or third aspect, the polarities of the one or more piezoelectric elements are the same or are alternately reversed in the order in which they are adjacent. It is characterized by polarity.

According to the fifth aspect of the present invention, the polarity of the one or a plurality of piezoelectric elements is the same or alternately reversed in the order in which they are adjacent to each other, so that a simple control signal voltage can be obtained. The displacement of the mirror surface shape can be zero-crossed near the end of the deformable mirror, and the aberration can be easily corrected near the end of the mirror surface.

According to a sixth aspect of the present invention, in the optical disk information input / output device according to the fifth aspect, the opposite polarities of the plurality of piezoelectric elements are formed by applying a strong electric field to the piezoelectric elements. And

According to the sixth aspect of the present invention, the opposite polarities of the plurality of piezoelectric elements are formed by applying a strong electric field to the piezoelectric elements. The displacement of the mirror surface shape can be zero-crossed, and the aberration near the end of the mirror surface can be easily corrected.

According to a seventh aspect of the present invention, in the optical disk information input / output device according to any one of the first to sixth aspects,
When the number of the piezoelectric elements is plural, the piezoelectric element has a main piezoelectric element and an auxiliary piezoelectric element, and a piezoelectric constant of the auxiliary piezoelectric element is larger than a piezoelectric constant of the main piezoelectric element.

According to the present invention, since the piezoelectric constant of the auxiliary piezoelectric element is larger than the piezoelectric constant of the main piezoelectric element, the auxiliary piezoelectric element bends more than the main piezoelectric element when the same voltage is applied. This makes it easier to make the mirror surface of the deformable mirror closer to an ideal mirror surface shape without reducing the durability of the piezoelectric element.

According to an eighth aspect of the present invention, there is provided the optical disk information input / output device according to any one of the first to seventh aspects,
When there are a plurality of the piezoelectric elements, the piezoelectric element has a main piezoelectric element and an auxiliary piezoelectric element, the thickness of the auxiliary piezoelectric element,
It is characterized in that it is thinner than the thickness of the main piezoelectric element.

According to the present invention, since the thickness of the auxiliary piezoelectric element is smaller than the thickness of the main piezoelectric element, the thickness of the auxiliary piezoelectric element is reduced to reduce the weight, and at the same time, the same voltage is applied. In this case, the auxiliary piezoelectric element bends more easily than the main piezoelectric element, and the mirror surface of the deformable mirror can be made closer to an ideal mirror surface shape.

According to a ninth aspect of the present invention, in the optical disk information input / output device according to any one of the second to eighth aspects,
When there are a plurality of the piezoelectric elements, the piezoelectric element has a main piezoelectric element and an auxiliary piezoelectric element, the size of the auxiliary piezoelectric element is smaller than the size of the main piezoelectric element, and / or
The plurality of piezoelectric element electrodes include a main piezoelectric element electrode for applying a control voltage to the main piezoelectric element and an auxiliary piezoelectric element electrode for applying a control voltage to the auxiliary piezoelectric element, and the auxiliary piezoelectric element electrode Is smaller than the size of the main piezoelectric element electrode.

According to the ninth aspect of the present invention, the size of the auxiliary piezoelectric element is smaller than the size of the main piezoelectric element, or the size of the auxiliary piezoelectric element electrode is larger than the size of the main piezoelectric element electrode. Therefore, the size of the entire mirror surface of the deformable mirror can be reduced.

The invention according to claim 10 is the invention according to claims 2 to 9
The optical disc information input / output device according to any one of the preceding claims, wherein when the plurality of piezoelectric elements are plural, the piezoelectric element has a main piezoelectric element and an auxiliary piezoelectric element, and the plural piezoelectric element electrodes are the main piezoelectric element. A main piezoelectric element electrode for applying a control voltage to the main piezoelectric element, and an auxiliary piezoelectric element electrode for applying a control voltage to the auxiliary piezoelectric element. The absolute value of the voltage applied to the auxiliary piezoelectric element electrode is The voltage is higher than the absolute value of the voltage applied to the electrode.

According to the tenth aspect of the present invention, the absolute value of the voltage applied to the auxiliary piezoelectric element electrode is larger than the absolute value of the voltage applied to the main piezoelectric element electrode. It is greatly bent, and the shape of the mirror surface can be approximated to an ideal shape.

According to an eleventh aspect of the present invention, in the optical disk information input / output device according to the second aspect, when the plurality of piezoelectric elements are provided, the piezoelectric element is a main piezoelectric element and at least two piezoelectric elements around the main piezoelectric element. One or more auxiliary piezoelectric elements, and / or the plurality of piezoelectric element electrodes include a main piezoelectric element electrode for applying a control voltage to the main piezoelectric element and an auxiliary piezoelectric element for applying a control voltage to the auxiliary piezoelectric element. An electrode for an element is provided, and at least two or more electrodes for the auxiliary piezoelectric element are provided around the electrode for the main piezoelectric element.

According to the eleventh aspect of the present invention, the main piezoelectric element and at least two or more auxiliary piezoelectric elements exist around the main piezoelectric element, and / or an electrode for the main piezoelectric element and an electrode for the main piezoelectric element. Since there are at least two or more auxiliary piezoelectric element electrodes around the electrodes, it is possible to finely adjust the shape of the zero-crossing part, and to make the initial shape of the mirror surface closer to an ideal plane.

According to a twelfth aspect of the present invention, in the optical disk information input / output device according to the second aspect, when there are a plurality of the piezoelectric elements, the piezoelectric elements have at least two or more main piezoelectric elements, and / or The plurality of piezoelectric element electrodes have a main piezoelectric element electrode for applying a control voltage to the main piezoelectric element and an auxiliary piezoelectric element electrode for applying a control voltage to the auxiliary piezoelectric element, and the main piezoelectric element electrode Is characterized by having at least two or more.

According to the twelfth aspect of the present invention, since at least two or more main piezoelectric elements are present and / or at least two or more main piezoelectric element electrodes are present, aberration correction near the center of the mirror surface can be achieved. Fine adjustment, correction of aberrations generated in a plurality of directions of the laser beam, fine adjustment of the mirror surface shape at the zero-crossing point, and the like can be easily performed. Further, the initial shape of the mirror surface can be easily brought close to an ideal plane.

According to a thirteenth aspect of the present invention, in the optical disk information input / output device according to the second aspect, the piezoelectric element comprises:
It is characterized by being controlled independently by the plurality of piezoelectric element electrodes.

According to the thirteenth aspect, since the control voltage is applied to each of the plurality of piezoelectric element electrodes completely independently, it is possible to finely adjust the shape of the entire mirror surface of the deformable mirror. Also, the initial shape of the mirror surface can be satisfactorily approximated to an ideal plane.

According to a fourteenth aspect of the present invention, in the deformable mirror having a variable mirror surface, one or a plurality of piezoelectric elements are provided, and the shape of the mirror surface is controlled based on the deformation of the piezoelectric element. And

According to the fourteenth aspect of the present invention, the shape of the deformable mirror can be made close to a shape for correcting aberration due to tilt and the like, and the initial shape of the mirror can be made close to an ideal plane. A mirror can be provided.

[0039]

Next, an embodiment of the present invention will be described with reference to the drawings.

First, the basic structure of the deformable mirror according to the present invention will be described with reference to FIG. 1A is a perspective view of the deformable mirror of the present invention, FIG. 1B is a plan view of the deformable mirror seen from the mirror surface side of FIG. 1A, and FIG. 1C is shown in FIG. Line AA '
It is sectional drawing of the direction along. In the deformable mirror of the present invention, the mirror material 1 is mounted on the upper surface of the mirror substrate 6, and the insulating layer 7 is mounted on the lower surface of the mirror substrate 6. Insulating layer 7
The common electrode 4 is installed under the common electrode 4, the main piezoelectric element 2 and the auxiliary piezoelectric element 9 are mounted under the common electrode 4, and the individual electrodes 5 are provided under the main piezoelectric element 2 and the auxiliary piezoelectric element 9, respectively. (The main piezoelectric element individual electrode which is an individual electrode for applying a control voltage to the main piezoelectric element: 5a, the auxiliary piezoelectric element individual electrode which is an individual electrode for applying a control voltage to the auxiliary piezoelectric element: 5b)
Is installed. Here, the upper and lower expressions are expressed such that the mirror side is an upper side in a sectional view. The mirror section having the above-described structure is fixed to the mirror fixing member 8 by the mirror fixing section 3 of the mirror section. The mirror fixing member 8 has convex portions on two opposing sides as shown by the dotted circles in FIG.
The mirror is fixed by the mirror fixing part 3 shown in the plan view of FIG. 2 fixed in the mirror part of the deformable mirror
Since two opposing sides other than the side (mirror fixing part 3) are not fixed, the whole is more easily deformed than when all four sides of the mirror part are fixed. In addition, FIG.
As is apparent from FIG. 1C, the mirror fixing portion 3, the main piezoelectric element 2, and the individual electrodes 5 in the plan view seen from the mirror surface side in FIG. 1B are transparent so as to explain their positions. It is expressed, and in fact, is not visible from the mirror surface side but exists on the opposite side of the mirror surface.

Next, the operation of the deformable mirror according to the present invention will be described with reference to FIG. The horizontal axis in FIG.
In the A ′ cross section, the vertical axis represents the displacement of the mirror surface with respect to the plane.

First, the case where the auxiliary piezoelectric element 9 is not used, that is, no voltage is applied to the auxiliary piezoelectric element individual electrode 5b will be described. In the deformable mirror shown in FIG.
It is assumed that the common electrode 4 is grounded, the polarity of the main piezoelectric element 2 is uniformly in the same direction, and a positive voltage is applied to one of the main piezoelectric element individual electrodes 5a and a negative voltage is applied to the other. The mirror substrate 6 does not expand and contract when a voltage is applied, but the main piezoelectric element 2 expands and contracts when a voltage is applied. If a positive voltage is applied to the main piezoelectric element individual electrode 5a, the main piezoelectric element 2 at the portion where the individual electrode 5a is installed contracts, and if a negative voltage is applied, the main piezoelectric element individual electrode 5a is installed. Of the main piezoelectric element 2 of the main piezoelectric element 2
When a positive voltage is applied to the mirror material 1, the mirror surface of the mirror material 1 is convex, and when a negative voltage is applied to the main piezoelectric element individual electrode 5a, the mirror surface of the mirror material 1 is concave. As a result, the deformable mirror shown in FIG. 1 has a curved cross-sectional shape as shown in FIG. When a reverse voltage is applied to the two main piezoelectric element individual electrodes 5a, the cross-sectional shape is opposite to that of FIG. However, when the auxiliary piezoelectric element is not used, the shape of the surface of the deformable mirror is such that the entire mirror ends of the two opposing sides are fixed to the mirror fixing member 3, and FIG.
The displacement near the mirror end shown in (b) is about zero without zero-crossing with respect to a plane having a mirror surface shape before applying a voltage. Now, it is assumed that the ideal mirror surface shape of the deformable mirror required to correct the wavefront aberration of the laser beam due to the tilt is as shown in FIG. With the mirror surface shape of the deformable mirror when the auxiliary piezoelectric element shown in FIG. 2B is not used, aberration correction near the mirror end cannot be performed as compared with the ideal mirror surface shape shown in FIG. 2A.

In the present invention, by applying a control voltage to the main piezoelectric element 2 and a control voltage in an appropriate direction to the auxiliary piezoelectric element individual electrode 5b, the mirror surface of the deformable mirror is also used by using the auxiliary piezoelectric element 9. Deform. Here, it is assumed that the polarity of the auxiliary piezoelectric element 9 is in the same direction as the polarity of the main piezoelectric element 2. FIG.
A control voltage is also applied to the auxiliary piezoelectric element individual electrode 5b so as to have a shape similar to the ideal mirror shape shown in FIG. That is, according to the above-described example, the auxiliary piezoelectric element 9 contracts such that the mirror surface becomes convex on the auxiliary piezoelectric element individual electrode 5b adjacent to the main piezoelectric element individual electrode 5a which is concave by the main piezoelectric element. A positive voltage may be applied, and a negative voltage may be applied to the other auxiliary piezoelectric element individual electrode 5b. As a result, the mirror surface shape of the deformable mirror of the present invention deformed by the auxiliary piezoelectric element 9 is shown in FIG. Due to the deformation of the mirror surface by the auxiliary piezoelectric element 9, as shown in FIG. 2C, the mirror surface near the mirror end is similar to the ideal mirror surface shape shown in FIG. The displacement of the shape crosses zero. Therefore, aberration correction near the mirror end is also possible. However, in order to correct the aberration of the laser beam at the mirror end, it is necessary that the laser beam collimated and incident on the deformable mirror of the present invention does not protrude from between BB '. Here, B and B 'are positions where the displacement of the mirror surface by the auxiliary piezoelectric element 9 is maximum in the AA' section in FIG.

Next, the configuration of the optical disk information input / output device of the present invention using the deformable mirror of the present invention will be described. FIG. 3 shows a block diagram of the optical disk information input / output device of the present invention. As shown in FIG. 3, the optical disk information input / output device of the present invention includes a deformable mirror 10 of the present invention, an optical disk 11,
Objective lens and objective optical system 12, rising mirror 13, polarization beam splitter 14, laser element and laser optical system 1
5, comprising a light detection element and a light detection optical system 16. Laser light emitted from the laser element is converted into parallel light by the laser optical system, passes through the polarizing beam splitter 14, is reflected by the deformable mirror 10, is further reflected by the rising mirror 13, and is collected by the objective lens and the objective optical system 12. The light is focused on the optical disk 11. The laser light reflected from the optical disk 11 passes through the objective lens and the objective optical system 12, is reflected by the rising mirror 13, is reflected again by the shape deformable mirror 10, passes through the polarization beam splitter 14, and passes through the polarization detection optical system. The light is collected and detected by the light detection element. The light detecting element is also provided with a detecting element for tilt detection. FIG. 3
In the above, portions other than the optical disk 11 correspond to the optical pickup device.

Next, the correction of the wavefront aberration of the laser beam in the optical disk information input / output device of the present invention will be described. FIG.
In the optical disk information input / output device of the present invention, when the optical disk 11 is tilted, the wavefront of the laser light reflected and returned from the optical disk 11 is disturbed and coma aberration occurs. The wavefront aberration of the laser light returning from the tilted optical disk and entering the mirror surface of the deformable mirror 10 is represented by a contour line as shown in FIG. 4 with respect to the cross section of the light beam of the laser light. Here, the direction of the cross section of the laser beam corresponding to the direction in which the optical disk is tilted is the AA 'direction in FIG.
That is, a wavefront aberration whose sign changes along the AA 'direction occurs.

In order to cancel the wavefront aberration generated by such a tilt, the deformable mirror of the present invention shown in FIG.
The optical pickup device is installed on the optical axis of the optical pickup device as shown in FIG. 3 so that the AA ′ direction in FIG. 1 and the AA ′ direction in FIG. By controlling the shape of the mirror surface such that a convex surface and a concave surface are formed in the AA ′ direction in FIG. 1 by the operation of the deformable mirror of the present invention, correction of wavefront aberration (coma aberration) due to tilt or Reduction is possible. Here, for the sake of simplicity, the correction of the wavefront aberration of the laser beam will be described with reference to FIG. 5, focusing only on the AA ′ direction in FIG.

FIG. 5A is a diagram showing the wavefront aberration of the laser light in the direction AA ′ in FIG. Here, the vertical axis of FIG. 5 represents the wavefront aberration, and the horizontal axis represents the shape of the deformable mirror of the present invention shown in FIG. 1 in the direction of AA ′ in FIG. 1 and the direction of AA ′ in FIG. If it is installed, the horizontal axis in FIG. 5 is the same as the axis in the AA ′ direction of the deformable mirror shown in FIG. The wavefront aberration of FIG. 5A is the wavefront aberration of the light reflected by the deformable mirror when the optical disk 11 is tilted and the mirror surface of the deformable mirror 10 is completely flat in the optical system of FIG. . If the optical disk 11 is not tilted and is perpendicular to the optical axis of the laser beam, no wavefront aberration as shown in FIG.
The wavefront coincides with the horizontal axis. FIG. 5B is a diagram showing the wavefront aberration of reflected light when the deformable mirror shown in FIG. 1 is operated so as to intentionally generate aberration, and the aberration-free light is irradiated on the deformable mirror. is there. Now, suppose that the optical disc is tilted, and the wavefront aberration of the reflected light from the optical disc is shown in FIG.
Assume that Here, the shape of the deformable mirror is controlled such that the wavefront aberration of the light reflected by the deformable mirror when the optical disc is not tilted is as shown in FIG. At this time, the wavefront aberrations of FIGS. 5A and 5B cancel each other, and the wavefront aberration of the reflected light from the deformable mirror becomes as shown in FIG. ) Can reduce the wavefront aberration.

[Embodiment 1] FIG. 6 shows a first embodiment of the present invention.
Shown in FIGS. 6A to 6C are cross-sectional views of the mirror portion where the mirror fixing member 8 is not shown, and the thick lines drawn on the individual electrodes are connection means for connecting the electrodes. 6A, the main piezoelectric element 2 has a common electrode 4 and a main piezoelectric element individual electrode 5a, the common electrode 4 is grounded, and the same control voltage is applied to the two main piezoelectric element individual electrodes 5a. It has become. An auxiliary piezoelectric element 9 having a common electrode 4 and an auxiliary piezoelectric element individual electrode 5b is adjacent thereto, the common electrode 4 is grounded, and the auxiliary piezoelectric element individual electrode 5b is connected to the main piezoelectric element individual electrode 5a. The same control voltage is applied. The arrows in the figure indicate the polarization direction when a strong electric field is applied via the individual electrodes and polling is performed. The polarities (polarization directions) of adjacent piezoelectric elements are opposite to each other. For this reason, by always applying a voltage in the same direction as the control voltage applied to each individual electrode, the mirror surface crosses zero as shown in FIG. FIG.
6B shows an example in which the main piezoelectric element 2 is separated for each individual electrode, and FIG. 6C shows an example in which the main piezoelectric element and the auxiliary piezoelectric element are combined into one piezoelectric element and only the individual electrodes are divided. And each has the same effect as that of FIG.

Embodiment 2 FIG. 7 shows a second embodiment of the present invention.
Shown in FIGS. 7A to 7C are cross-sectional views of the mirror portion where the mirror fixing member 8 is omitted, and the lines drawn to the electrodes are wiring means for connecting the electrodes. FIG. 7A shows that the main piezoelectric element 2 has a common electrode 4 and a main piezoelectric element individual electrode 5a, the common electrode 4 is grounded, and the two main piezoelectric element individual electrodes 5a.
Are applied with opposite control voltages. An auxiliary piezoelectric element 9 having a common electrode 4 and an auxiliary piezoelectric element individual electrode 5b is adjacent thereto, the common electrode 4 is grounded, and an adjacent main piezoelectric element individual electrode 5a is adjacent to the auxiliary piezoelectric element individual electrode 5b. A control voltage opposite to the above is applied. The arrows in the figure show the polarization directions when a strong electric field is applied through the individual electrodes and polling is performed, and all of them are polarized in the same direction. Therefore, by inverting the voltage applied to each of the adjacent individual electrodes, the mirror surface crosses zero as shown in FIG. 5C, and the aberration can be corrected to the mirror end. FIG. 7B shows an example in which the main piezoelectric element 2 is separated for each electrode. FIG. 7C shows a case where the main piezoelectric element and the auxiliary piezoelectric element are combined into one piezoelectric element, and only the individual electrodes are divided. This is an example, and each has the same effect as that of FIG.

[Embodiment 3] FIG. 8 shows a third embodiment of the present invention.
Shown in FIG. 8 is a cross-sectional view of the mirror portion in which the mirror fixing member 8 is not shown. The basic structure is the same as that shown in FIG. 1, but the material of the main piezoelectric element 2 and the material of the auxiliary piezoelectric element 9 are different. That is, the piezoelectric constant of the piezoelectric material of the auxiliary piezoelectric element 9 is larger than the piezoelectric constant of the piezoelectric material of the main piezoelectric element 2. Therefore, even if the same voltage is applied to the main piezoelectric element 2 and the auxiliary piezoelectric element 9, the auxiliary piezoelectric element 9
5C, the inclination of the zero-crossing portion in FIG. 5C can be made steeper even with the same voltage, and the shape becomes closer to an ideal mirror surface shape.

[Embodiment 4] FIG. 9 shows a fourth embodiment of the present invention.
Shown in FIG. 9 is a cross-sectional view of the mirror unit in which the mirror fixing member 8 is not shown. The basic structure is the same as that shown in FIG. 1, but the thickness of the main piezoelectric element 2 and the thickness of the auxiliary piezoelectric element 9 are different. That is, the thickness of the auxiliary piezoelectric element 9 is smaller than the thickness of the main piezoelectric element 2. Therefore, the main piezoelectric element 2
Even if the same voltage is applied to the auxiliary piezoelectric element 9, the auxiliary piezoelectric element 9 is more easily bent, the inclination of the zero crossing portion in FIG. 5C can be made steeper, and the mirror surface approaches an ideal mirror surface shape.

Embodiment 5 FIG. 1 shows a fifth embodiment of the present invention.
0 is shown. FIG. 10 is a cross-sectional view of the mirror section in which the mirror fixing member 8 is not shown. The basic structure is the same as that shown in FIG. 1, but the size of the main piezoelectric element 2 and the auxiliary piezoelectric element 9
Are greatly changed from those in the embodiment shown in FIGS. Also, the piezoelectric materials and thicknesses of the main piezoelectric element 2 and the auxiliary piezoelectric element 9 are changed from those in FIGS. 8 and 9 so that the thickness of the auxiliary piezoelectric element 9 is smaller than the thickness of the main piezoelectric element 2 and the piezoelectric material of the auxiliary piezoelectric element 9 Is made larger than the piezoelectric constant of the piezoelectric material of the main piezoelectric element 2. Therefore, even when the same voltage is applied, the auxiliary piezoelectric element 9 is more easily bent than the main piezoelectric element 2, so that the size of the auxiliary piezoelectric element 9 can be reduced, and the size of the entire mirror is reduced. be able to.

[Embodiment 6] FIG. 1 shows a sixth embodiment of the present invention.
It is shown in FIG. FIG. 11 is a cross-sectional view of the mirror portion where the mirror fixing member 8 is not shown. The basic structure is the same as that shown in FIG. 1, except that the main piezoelectric element individual electrode 5a and the auxiliary piezoelectric element individual electrode 5b can be applied with a control voltage independently of each other. The absolute value of the control voltage applied to the electrode 5b is relatively larger than the absolute value of the voltage applied to the main piezoelectric element individual electrode 5a.
For this reason, the auxiliary piezoelectric element 9 can be more easily bent, the inclination of the zero crossing portion in FIG. 5C can be made steeper, and the mirror surface approaches an ideal mirror surface shape.

[Embodiment 7] FIG. 1 shows a seventh embodiment of the present invention.
It is shown in FIG. FIG. 12 is a cross-sectional view of the mirror section in which the mirror fixing member 8 is not shown. The basic structure is the same as that shown in FIG. 1, but there is an additional auxiliary piezoelectric element 9 a next to the auxiliary piezoelectric element 9. In this example, the polarization directions of the piezoelectric elements are the same, and the control voltages of the adjacent piezoelectric elements are opposite to each other. FIG. 13 is a diagram for comparing the mirror surface shape of the deformable mirror with and without the additional auxiliary piezoelectric element 9a shown in FIG. The dotted line indicates the mirror shape when there is no additional auxiliary piezoelectric element 9a, and the solid line indicates the mirror surface shape when there is the additional auxiliary piezoelectric element 9a. With the additional auxiliary piezoelectric element 9a, the slope of the portion where the zero crossing occurs can be made steeper, and the mirror surface shape becomes even more ideal. Also in the above-described embodiment, it is needless to say that the electrodes may be divided using a common piezoelectric element, or individual piezoelectric elements may be used.

[Embodiment 8] FIG. 1 shows an eighth embodiment of the present invention.
It is shown in FIG. The basic structure is the same as that shown in FIG.
The mirror material 1 is attached to the mirror substrate 6, and an insulating layer 7 is attached to a surface of the mirror substrate 6 opposite to the mirror material 1. The common electrode 4 is attached below the insulating layer 7, the main piezoelectric element 2 and the auxiliary piezoelectric element 9 are attached below the common electrode 4, and the individual electrodes 5 are attached below each. The mirror section having such a structure is fixed to the mirror fixing member by the mirror fixing section 3. In FIG. 14, the auxiliary piezoelectric element 9 is divided into a plurality of parts by the auxiliary piezoelectric element individual electrodes 5b, so that a control voltage can be individually applied. In this embodiment, since the auxiliary piezoelectric element 9 is divided into a plurality of parts by the auxiliary piezoelectric element individual electrodes 5b, fine adjustment of the shape of the zero crossing portion is possible. Also, the initial shape of the mirror surface can be made closer to an ideal plane.
For this embodiment, instead of dividing the individual electrodes, individual piezoelectric elements may be used, and the number of divided individual electrodes or the number of piezoelectric elements may be larger or smaller than in this embodiment. It goes without saying that it is good.

Embodiment 9 FIG. 1 shows a ninth embodiment of the present invention.
It is shown in FIG. The basic structure is the same as that shown in FIG.
The mirror material 1 is attached to the mirror substrate 6, and an insulating layer 7 is attached to a surface of the mirror substrate 6 opposite to the mirror material 1. The common electrode 4 is attached below the insulating layer 7, the main piezoelectric element 2 and the auxiliary piezoelectric element 9 are attached below the common electrode 4, and the individual electrodes 5 are attached below each. The mirror section having such a structure is fixed to the mirror fixing member by the mirror fixing section 3. In the case of the example of FIG.
Are divided into a plurality of parts by the main piezoelectric element individual electrodes 5a, so that a control voltage can be individually applied to each.
As described above, since the main piezoelectric element 2 is divided into a plurality of parts by the main piezoelectric element individual electrodes 5a, fine adjustment of the shape of the zero crossing portion and fine adjustment of the mirror shape in the direction perpendicular to the AA 'direction are performed. It becomes possible. Also, the initial shape of the mirror surface can be made closer to an ideal plane. For this embodiment, instead of dividing the individual electrodes, individual piezoelectric elements may be used, and the number of divided individual electrodes or the number of piezoelectric elements may be larger or smaller than in this embodiment. It goes without saying that it is good.

[Embodiment 10] FIG. 16 shows a tenth embodiment of the present invention. The basic structure is the same as that shown in FIG. 1. A mirror substrate 1 has a mirror material 1 attached thereto, and an insulating layer 7 is attached to a surface of the mirror substrate 6 opposite to the mirror material 1. The common electrode 4 is attached below the insulating layer 7, the main piezoelectric element 2 and the auxiliary piezoelectric element 9 are attached below the common electrode 4, and the individual electrodes 5 are attached below each. The mirror section having such a structure is fixed to the mirror fixing member by the mirror fixing section 3. In the case of the example of FIG.
Are divided into a plurality of parts by the main piezoelectric element individual electrodes 5a, so that a control voltage can be individually applied to each of them.
The auxiliary piezoelectric element 9 is also divided into a plurality of parts by the auxiliary piezoelectric element individual electrode 5b, so that a control voltage can be individually applied to each. Since the main and auxiliary piezoelectric elements are divided into a plurality of parts by the individual electrodes 5a and 5b in this manner, fine adjustment of the shape of the zero-crossing portion and fine adjustment of the mirror shape in the direction perpendicular to the AA 'direction, Further, not only tilt correction in the AA 'direction but also tilt correction in a direction perpendicular to the AA' direction can be easily performed.
Also, the initial shape of the mirror surface can be made closer to an ideal plane. For this embodiment, instead of dividing the individual electrodes, individual piezoelectric elements may be used, and the number of divided individual electrodes or the number of piezoelectric elements may be more or less than in this embodiment. Needless to say.

[Eleventh Embodiment] FIG. 17 shows an eleventh embodiment of the present invention. Although the basic structure is the same as that shown in FIG. 1, there is no common electrode, and the main piezoelectric element 2 has a main piezoelectric element individual electrode 5a and a main piezoelectric element rear surface individual electrode 5d,
The auxiliary piezoelectric element 9 is provided with an auxiliary piezoelectric element individual electrode 5b and an auxiliary piezoelectric element back surface individual electrode 5e. For this reason, a control voltage can be individually applied to each piezoelectric element, so that not only the shape near the zero cross of the mirror surface but also the whole shape of the mirror can be finely adjusted. Also, the initial shape of the mirror surface can be made closer to an ideal plane. Further, since the common electrode is not used, the control voltage can be applied to each piezoelectric element completely independently, so that the voltage width of the control voltage is about half that of the common electrode. For this embodiment, instead of dividing the individual electrodes, individual piezoelectric elements may be used, and the number of divided individual electrodes or the number of piezoelectric elements may be larger or smaller than in this embodiment. It goes without saying that it is good.

Although the embodiments have been described to explain the present invention, it goes without saying that the present invention can be applied without being limited to these embodiments. For example, a combination of the features of the deformable mirror shown in each embodiment may be used.
Further, the shape of the division is not limited to the shape of the embodiment, and may be a curved shape or a polygonal shape.

In the embodiment, the deformable mirror for correcting the wavefront aberration of the laser light generated by the tilt has been described. However, the mirror arrangement can be deformed by effectively utilizing the arrangement of the electrodes and the polarity of the piezoelectric element. The state may be controlled and used for aberration correction such as spherical aberration and astigmatism correction.

In the present invention described above, the mirror material 1 is used.
Is, for example, a deposited film of Au or a dielectric multilayer film, and the insulating layer 7 is a thermal oxide film or an insulating material deposited by a CVD method (gas phase chemical deposition method). The common electrode 4 and the individual electrode 5 are made of a highly conductive material or a metal film. When a high-temperature process is used in the process of manufacturing the deformable mirror, Pt is used.
For example, a film resistant to high temperatures is desirable. The piezoelectric element may be a piezoelectric ceramic such as PZT (trade name) or a piezoelectric polymer such as PVDF (polyvinylidene fluoride), a thin plate of the piezoelectric element may be attached, and the piezoelectric element film is formed on the mirror substrate side. You may. The mirror substrate 6 is preferably made of silicon,
A hard material such as ceramics or glass, or a polymer material such as PET (polyethylene terephthalate) or polyimide may be used. If the silicon substrate has a high resistivity and is close to an insulator, the insulating layer can be omitted.

[0062]

As described above, according to the present invention, it is possible to make the mirror surface of the deformable mirror closer to a shape for correcting aberrations due to tilt and the like, and to make the initial shape of the mirror surface closer to an ideal plane. Further, it is possible to provide an optical information input / output device including an optical pickup device having a deformable mirror capable of correcting laser beam aberration.

[0063]

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a basic structure of a deformable mirror according to the present invention. (A) a perspective view, (b) a plan view seen from a mirror surface side,
(C) It is sectional drawing of the AA 'direction.

FIG. 2 is a diagram illustrating a change in the shape of a cross section taken along the line AA ′ of the mirror surface in the deformable mirror according to the present invention. (A) The ideal mirror surface shape for correcting the wavefront aberration, (b) the mirror surface shape when the auxiliary piezoelectric element is not used, and (c) the mirror surface shape when the auxiliary piezoelectric element is also used.

FIG. 3 is a block diagram of the entire optical disc information input / output device including the shape changing mirror of the present invention.

FIG. 4 is a contour diagram of wavefront aberration of laser light generated by tilt.

FIG. 5 is a diagram illustrating correction of a wavefront aberration in an AA ′ section by the deformable mirror of the present invention. (A) A wavefront aberration diagram of a laser beam generated by tilt, (b) a wavefront aberration diagram generated by the deformable mirror of the present invention, and (c) a wavefront aberration diagram corrected by the deformable mirror of the present invention. .

FIG. 6 is a view showing a first embodiment of a deformable mirror according to the present invention. (A) An embodiment using the deformable mirror having the basic structure shown in FIG. 1, (b) an example in which the main piezoelectric element is divided, and (c) an example in which the main piezoelectric element and the auxiliary piezoelectric element are integrated into one.

FIG. 7 is a view showing a second embodiment of the deformable mirror according to the present invention. (A) An embodiment using the deformable mirror having the basic structure shown in FIG. 1, (b) an example in which the main piezoelectric element is divided, and (c) an example in which the main piezoelectric element and the auxiliary piezoelectric element are integrated into one.

FIG. 8 is a view showing a third embodiment of the deformable mirror according to the present invention.

FIG. 9 is a view showing a fourth embodiment of the deformable mirror according to the present invention.

FIG. 10 is a view showing a fifth embodiment of the deformable mirror according to the present invention.

FIG. 11 is a view showing a sixth embodiment of the deformable mirror according to the present invention.

FIG. 12 is a view showing a seventh embodiment of the deformable mirror according to the present invention.

FIG. 13 is a diagram illustrating an effect of a deformable mirror on a shape change in a seventh embodiment of the present invention.

FIG. 14 is a view showing an eighth embodiment of the deformable mirror according to the present invention.

FIG. 15 is a view showing a ninth embodiment of the deformable mirror according to the present invention.

FIG. 16 is a view showing a tenth embodiment of the deformable mirror of the present invention.

FIG. 17 is a view showing an eleventh embodiment of the deformable mirror of the present invention.

FIG. 18 is a diagram illustrating generation of coma due to tilt of the optical disc. It is a figure in (a) CD and (b) DVD.

FIG. 19 is a view of a conventional liquid crystal plate.

FIG. 20 is a diagram of a conventional transparent piezoelectric element.

FIG. 21 is a view of a conventional deformable mirror using a plurality of actuators.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 mirror material 2 main piezoelectric element 3 mirror fixing part 4 common electrode 5 individual electrode 5 a main piezoelectric element individual electrode 5 b auxiliary electric element individual electrode 5 c additional auxiliary piezoelectric element individual electrode 5 d main piezoelectric element backside individual electrode 5 e auxiliary piezoelectric element backside individual electrode Reference Signs List 6 mirror substrate 7 insulating layer 8 mirror fixing member 9 auxiliary piezoelectric element 9a additional auxiliary piezoelectric element 10 shape variable mirror 11 optical disk 12 objective lens and objective optical system 13 startup mirror 14 polarization beam splitter 15 laser element and laser optical system 16 light Detection element and light detection optical system 101a Objective lens for CD 101b Objective lens for DVD 102a Disk for CD 102b Disk for DVD 103a Laser beam spot on CD 103b Laser beam spot on DVD 108 Recording layer

Claims (14)

[Claims] 1. An optical disk information input / output device including an optical pickup device, wherein the optical pickup device includes a deformable mirror having a variable mirror surface shape for controlling aberration of laser light, Alternatively, the optical disk information input / output device has a plurality of piezoelectric elements, and the shape of the mirror surface of the deformable mirror is controlled based on the deformation of the piezoelectric elements. 2. The deformable mirror has a plurality of piezoelectric element electrodes, and the piezoelectric element is deformed for each piezoelectric element electrode by a control voltage applied to the plurality of piezoelectric element electrodes. 2. The optical disk information input / output device according to claim 1, wherein: 3. A piezoelectric element corresponding to the piezoelectric element electrode, wherein a control voltage is applied to the plurality of piezoelectric element electrodes so that adjacent piezoelectric elements are deformed in opposite directions. The optical disk information input / output device according to claim 2. 4. The optical disk information input / output according to claim 2, wherein the same control voltage or a control voltage having an opposite sign is alternately applied to the plurality of piezoelectric element electrodes in the order in which the electrodes are adjacent to each other. apparatus. 5. The optical disk information input / output device according to claim 2, wherein the polarities of the one or more piezoelectric elements are the same, or are alternately opposite in the order in which they are adjacent. . 6. The optical disk information input / output device according to claim 5, wherein the opposite polarities of the plurality of piezoelectric elements are formed by applying a strong electric field to the piezoelectric elements. 7. When there are a plurality of piezoelectric elements, the piezoelectric element has a main piezoelectric element and an auxiliary piezoelectric element, and the piezoelectric constant of the auxiliary piezoelectric element is larger than the piezoelectric constant of the main piezoelectric element. 7. The optical disk information input / output device according to claim 1, wherein the input / output device is an optical disk information input / output device. 8. When there are a plurality of piezoelectric elements, the piezoelectric element has a main piezoelectric element and an auxiliary piezoelectric element, and the thickness of the auxiliary piezoelectric element is smaller than the thickness of the main piezoelectric element. The optical disk information input / output device according to any one of claims 1 to 7, wherein 9. When there are a plurality of the piezoelectric elements, the piezoelectric element has a main piezoelectric element and an auxiliary piezoelectric element, and the size of the auxiliary piezoelectric element is smaller than the size of the main piezoelectric element, and / or The plurality of piezoelectric element electrodes include a main piezoelectric element electrode for applying a control voltage to the main piezoelectric element and an auxiliary piezoelectric element electrode for applying a control voltage to the auxiliary piezoelectric element. 9. The optical disk information input / output device according to claim 2, wherein a size of the electrode is smaller than a size of the main piezoelectric element electrode. 10. When there are a plurality of piezoelectric elements, the piezoelectric element has a main piezoelectric element and an auxiliary piezoelectric element, and the plurality of piezoelectric element electrodes are main piezoelectric elements for applying a control voltage to the main piezoelectric element. An element electrode and an auxiliary piezoelectric element electrode for applying a control voltage to the auxiliary piezoelectric element, wherein the absolute value of the voltage applied to the auxiliary piezoelectric element electrode is the absolute value of the voltage applied to the main piezoelectric element electrode. 10. The optical disk information input / output device according to claim 2, wherein the value is larger than the value. 11. When there are a plurality of the piezoelectric elements, the piezoelectric element has a main piezoelectric element and at least two or more auxiliary piezoelectric elements around the main piezoelectric element, and / or the plurality of piezoelectric elements. The main electrode has a main piezoelectric element electrode for applying a control voltage to the main piezoelectric element, and an auxiliary piezoelectric element electrode for applying a control voltage to the auxiliary piezoelectric element. The auxiliary electrode is provided around the main piezoelectric element electrode. 3. The optical disk information input / output device according to claim 2, comprising at least two or more piezoelectric element electrodes. 12. When there are a plurality of the piezoelectric elements, the piezoelectric element has at least two or more main piezoelectric elements, and / or the plurality of piezoelectric element electrodes apply a control voltage to the main piezoelectric element. 3. The optical disk according to claim 2, further comprising an electrode for a main piezoelectric element, and an electrode for an auxiliary piezoelectric element for applying a control voltage to the auxiliary piezoelectric element, wherein the number of the main piezoelectric element electrodes is at least two. Information input / output device. 13. The optical disk information input / output device according to claim 2, wherein the piezoelectric element is independently controlled by the plurality of piezoelectric element electrodes. 14. A deformable mirror having a variable mirror surface shape, comprising one or more piezoelectric elements, wherein the shape of the mirror surface is controlled based on the deformation of the piezoelectric element.