JP2006012286A - Aberration correction element, electronic device, and optical apparatus - Google Patents

Abstract

An aberration correction element having a curved surface with high accuracy using a piezoelectric element is provided.
A beam is reflected by a reflection film. The optical system is adjusted so that there is no aberration in this initial state. Next, when recording / reproducing is performed on another surface of the optical disk from this state, spherical aberration occurs due to the difference in the thickness of the optical disk protective layer, so that a voltage is applied to the lower electrode film 34a and the upper electrode film 34b. When an electric field is applied to the piezoelectric film 31, it is deformed so as to reduce the curvature due to piezoelectric distortion, and the spherical aberration is corrected. The lower electrode film 34a, the piezoelectric film 31, the upper electrode film 34b, and the reflective film 33 are all formed of a uniform film thickness, but the film thickness adjusting layer 32 is thin at the central portion and thick at the peripheral portion. ing. The reflecting surface is not only deformed according to the thickness distribution of the film thickness adjusting layer 32 but also deformed by the balance between the stress distribution corresponding to the thickness distribution of the film thickness adjusting layer 32 and the internal stress of each film generated at the time of fabrication. ing.
[Selection] Figure 1

Description

  The present invention relates to an aberration correction element used in an optical pickup of an optical disk device.

  As an information recording medium using an optical disk device, there are a compact disk (CD) and a digital video disk (DVD). Furthermore, in accordance with the rapid development of multimedia technology, a Blu-ray optical disc (BD) using a blue laser with a shorter wavelength than before has been developed to achieve a large capacity for reading or recording information. .

  A single optical disk device in recent years is configured to be compatible with any of the plurality of optical disks. This, on the other hand, requires high-density mounting of the optical disk device. That is, it is necessary to dispose an optical system corresponding to a plurality of optical disks in the same optical disk apparatus as in the prior art. Furthermore, apart from that, there is an increasing need for smaller and thinner optical disc devices for personal computers, particularly notebook personal computers, and there is a growing need for smaller components, higher density mounting, and smaller optical systems. It has become a big issue.

By the way, the BD is composed of two layers of disk surfaces, and it is necessary to correct spherical aberration that occurs when data of the first layer and the second layer is recorded and reproduced. Therefore, it can be said that the problem of the BD optical disk device used in the personal computer is to correct the spherical aberration with a small component. In order to solve this problem, a spherical aberration correction element using a thin film mirror using elastic deformation of a piezoelectric element has been proposed in the following patent documents, for example.
JP 2000-105306 A JP-A-10-123438 JP-A-8-21964

  However, in the standard of the BD optical disk device, the requirement for optical aberration is severe because a blue laser with a short wavelength is used and the numerical aperture (NA) is 0.85 which is larger than the conventional one. On the other hand, the above-mentioned patent document does not disclose how a deformable mirror with a strict accuracy as required for a BD optical disk can be produced.

  In general, when a method using a semiconductor process that is inexpensive and suitable for mass production is used, vapor deposition, sputtering, or the like is used for film formation, but the formed film generally has internal stress due to thermal stress or the like. For this reason, an aberration element produced by a semiconductor process always has a warp due to stress. Therefore, no matter how the mirror shape of the aberration correction element is designed by optical design, it is very difficult to make such a shape with high accuracy by a semiconductor process.

  Therefore, the problem to be solved by the present invention is to provide an aberration correction element having an accurate curved surface by using a piezoelectric element, and more specifically, by using a semiconductor process, the accuracy as in optical design. It is to produce an aberration correction element having a curved surface.

The present invention has been made in order to solve the above-described problems, and includes a substrate, a cavity part, and a film thickness adjusting layer in which the film thickness of the elastic body provided facing the cavity part is non-uniform, An aberration correction element comprising: a piezoelectric film provided facing the cavity portion; a pair of electrode films sandwiching the piezoelectric film; and an optical reflection film.

  According to the present invention, it is possible to produce a mirror having a curved surface with high accuracy according to the optical design, so that optical aberrations, particularly spherical aberration, can be reduced with high accuracy, and when used as an optical pickup, Recording / reproduction characteristics can be improved.

  According to a first aspect of the present application, a substrate, a cavity portion, a film thickness adjusting layer having a non-uniform thickness of an elastic body provided to face the cavity portion, and the cavity portion are provided. An aberration correction element comprising: a piezoelectric film; a pair of electrode films sandwiching the piezoelectric film; and an optical reflection film. Thereby, an optical reflection film having a curved surface as designed with high accuracy can be produced.

  The second invention of the present application is characterized in that the film thickness of the film thickness adjusting layer varies in a discrete gradation from 0.01 μm to 10 μm. Thereby, it is possible to accurately produce a mirror curved surface having an arbitrary shape.

  The third invention of the present application is characterized in that the film thickness distribution of the film thickness adjusting layer is axisymmetric. Thereby, spherical aberration can be corrected effectively.

  A fourth invention of the present application is characterized in that the film thickness distribution of the film thickness adjusting layer is a convex shape that is thick at the center and thin at the periphery. Thereby, it is possible to correct spherical aberration with high accuracy.

  The fifth invention of the present application is characterized in that the film thickness distribution of the film thickness adjusting layer is a concave shape that is thin at the center and thick at the periphery. Thereby, it is possible to correct spherical aberration with high accuracy.

  The sixth invention of the present application is characterized in that the film thickness adjusting layer is formed by a semiconductor process using a gray scale resist. Thereby, the film thickness adjusting layer can be manufactured with low cost and high accuracy.

  The seventh invention of the present application is characterized in that the gray scale resist is formed directly or indirectly by a drawing exposure apparatus using a laser or an electron beam. Thereby, a film thickness adjustment layer can be produced with high accuracy.

  The eighth invention of the present application is characterized in that the gray scale resist is formed using a gray scale mask. Thereby, the film thickness adjusting layer can be manufactured with low cost and high accuracy by mass production.

  The ninth invention of the present application is characterized in that the film thickness adjusting layer has a similar shape of a basis function in Zernike expansion. Thereby, an aberration correction element capable of correcting all optical aberrations can be provided.

  The tenth invention of the present application is characterized in that the film thickness adjusting layer is a film other than the reflective film. As a result, an accurate curved mirror can be obtained without degrading the optical characteristics of the reflective film formed of the dielectric laminated film.

An eleventh invention of the present application is characterized in that a film thickness adjusting layer is provided on the cavity side, and the film thickness adjusting layer is formed by a shadow effect of the cavity using an isotropic film forming method. This
It is possible to easily produce the film thickness adjusting layer without using special equipment.

  A twelfth aspect of the present invention is characterized in that a film thickness adjusting layer is provided on the cavity side, and the film thickness adjusting layer is formed by a shadow effect of the cavity using an isotropic etching method. Thereby, the film thickness adjusting layer can be easily produced without using special equipment.

  The thirteenth invention of the present application is characterized in that the film thickness adjusting layer is processed and formed by a picosecond laser or a femtosecond laser. Thereby, a film thickness adjusting layer having an arbitrary curved surface shape with high accuracy can be produced.

  A fourteenth aspect of the present invention is an electronic apparatus equipped with the aberration correction element according to any one of the first to thirteenth aspects. Accordingly, it is possible to provide an electronic device using an inexpensive and small aberration correction element in all electronic devices that require aberration correction, such as a digital camera and a mobile phone with a camera, as well as the optical pickup.

  A fifteenth aspect of the present invention is an optical device including the aberration correction element according to any one of the first to thirteenth aspects. This makes it possible to provide an optical device using an inexpensive and small aberration correction element in any optical device that requires aberration correction, such as an astronomical telescope, a microscope, and a camera.

(Embodiment 1)
Hereinafter, an embodiment of the present invention will be described. First, FIG. 10 shows a basic configuration example of an optical pickup in the optical disk device. First, a beam emitted from the light source 18 in the P polarization is transmitted through the polarization beam splitter 15, is transmitted through the quarter wavelength plate 14, is reflected by the aberration correction element 1, and is transmitted through the quarter wavelength plate 14 again to be S polarization. Then, it is reflected by the polarizing beam splitter 15, passes through the quarter-wave plate 13, is reflected by the rising mirror 17, is condensed by the objective lens 12, and forms a spot on the optical disk 11.

  The beam reflected by the optical disk 11 passes through the objective lens 12 again, is reflected by the rising mirror 17, passes through the quarter-wave plate 13 and becomes P-polarized light, passes through the polarization beam splitter 15, and passes through the light receiving element. 16 is reached. The light incident on the light receiving element 16 is converted into an electric signal.

  The aberration correction element in the aberration correction element 1 performs the aberration correction operation by changing the curvature of the mirror surface by being supplied with a control voltage from the driver IC 20. The electric signal obtained by the driver IC 20 is calculated by the calculation device 21 to calculate the spherical aberration amount, and the value of the control voltage applied to the aberration correction element 1 is fed back.

  FIGS. 11A and 11B are enlarged views of the objective lens 12, the optical disk 11, and the aberration correction element 1 in FIG. 10, respectively. The optical disk 11 has a two-layer structure, and can have information on the first surface 51 and the second surface 52 on the optical disk substrate 50. The beam 40 is condensed by the objective lens 12, refracted by the optical disk surface 53, and is focused on one of the first surface 51 and the second surface 52.

FIG. 11A shows a case where recording / reproduction is performed on the second surface 52. In this case, the power supply 54 of the driver IC 20 is turned off, and the piezoelectric film 31 is in an initial state at the time of manufacture. Here, since the aberration correction element 1 is simple, only the piezoelectric film 31 is shown. FIG. 11B shows a case where recording / reproduction is performed on the first surface 51. In this case, the power supply 54 of the driver IC 20 is turned on, and the piezoelectric film 31 is deformed from the initial state due to piezoelectric distortion. is doing. In this embodiment, the piezoelectric film 31 has a relatively large curvature in the initial stage, and is deformed to a relatively small curvature when an electric field is applied.

  Next, an aberration correction element according to the present invention will be described with reference to FIGS. 1 (a), 1 (b), and 1 (c).

  FIG. 1A, FIG. 1B, and FIG. 1C are diagrams showing the aberration correction element 1 in FIG. 10 with the substrate facing down, respectively. FIG. 1A is a perspective view from above of the aberration correction element according to the present invention, and FIG. 1B is a perspective view from the substrate side. FIG.1 (c) shows sectional drawing in the cross section AB in Fig.1 (a). The aberration correction element 1 includes a substrate 35, a lower electrode film 34a, a piezoelectric film 31, an upper electrode film 34b, a film thickness adjusting layer 32, and a reflective film 33 in order from the bottom. Reference numerals 37 and 38 denote electrode pads.

  A part of the substrate 35 has a circular cavity 39. The inside of the cavity 39 is composed only of the lower electrode film 34a excluding the substrate, the piezoelectric film 31, the upper electrode film 34b, the film thickness adjusting layer 32, and the reflective film 33, and the film thickness is relatively larger than the part other than the cavity. It becomes a very thin film. Therefore, the structure is easily deformed by stress due to heat or piezoelectric strain. Particularly, as shown in FIG. 1C, the film inside the cavity 39 is deformed into a certain shape as an initial state due to internal stress generated during film formation.

  The beam 40 is reflected by the reflective film 33. In one form, the optical system is adjusted to eliminate aberrations in this initial state. Next, when recording / reproducing is performed on another surface of the optical disk from this state, spherical aberration occurs due to the difference in the thickness of the optical disk protective layer, so that a voltage is applied to the lower electrode film 34a and the upper electrode film 34b. When an electric field is applied to the piezoelectric film 31, it is deformed so as to reduce the curvature due to piezoelectric distortion, and the spherical aberration is corrected. The lower electrode 34a, the piezoelectric film 31, the upper electrode 34b, and the reflective film 33 are all formed of a uniform film thickness, but the film thickness adjusting layer 32 is thin at the central portion and thick at the peripheral portion. . The reflective surface is not only deformed according to the thickness distribution of the film thickness adjusting layer 32, but is also deformed by the balance between the stress distribution corresponding to the thickness distribution of the film thickness adjusting layer and the internal stress of each film generated during the production. This is an important difference from the conventional technology.

  The embodiments of the present invention will be described in detail with respect to the initial shapes of the film thickness adjusting layer and the aberration correction element. FIG. 2 is a simplified view of FIG. 1C with respect to internal stress. As shown in FIG. 2, it is assumed that the film structure is composed of films having two types of internal stresses, ie, a tensile film 41 and a film thickness adjusting layer 32 of the compressed film from the bottom. That is, the tensile film 41 has a contraction stress, and the film thickness adjustment layer has an extension stress. In this case, as a result of the upper film extending and the lower film contracting in the vicinity of the circumference of the thin film, an upward convex bending moment acts. In the vicinity of the circumference, the thin film is fixed to the substrate, so that a reaction force 42 of the bending moment is generated. The action works, and as a result, the entire film has a downwardly convex shape.

  On the other hand, in the central portion, the bending moment generated by the internal stress is convex upward, but since the entire film is deformed downward, the internal stress is a resistance force against the deformation of the entire film. That is, the internal stress generated at the time of manufacture suppresses the deformation of the film in the central portion. Therefore, when the present invention is used, the film thickness is relatively thicker in the peripheral part than in the central part, and the film thickness is relatively thin in the central part. On the other hand, the compressive force is relatively small in the central portion, and the resistance force against the deformation of the entire film is relatively small. Therefore, the deformation in the downward direction of the film is also promoted.

Thus, the use of the present invention has an effect of increasing the downward deformation of the film in both the central portion and the peripheral portion. This effect is equally effective whether the initial shape is a flat surface or a curved surface. As described above, by using the present invention, it is possible to obtain a larger deformation than the conventional technique.

  Another embodiment of the present invention is shown in FIG. In FIG. 3, the film structure is composed of a compression film 41 and a tensile film thickness adjusting layer 32 from the bottom. In this case, in the vicinity of the circumference of the thin film, the upper film contracts and the lower film expands, resulting in a downward convex bending moment. Since the thin film is fixed to the substrate near the circumference, a reaction force 42 of the bending moment is generated. However, the other end of the bending moment slightly away from the circumference receives the couple 43, and the whole film is caused near the circumference. The action of pushing up works, and as a result, the whole film becomes a convex shape. On the other hand, in the central portion, the bending moment generated by the internal stress is convex downward, but since the entire film is deformed upward, the internal stress is a resistance force against the deformation of the entire film. That is, in the central part, the internal stress generated during the production hinders the deformation of the film. Therefore, when the present invention is used, the film thickness is relatively thicker at the peripheral part than at the central part, and the film thickness is relatively thin at the central part. On the other hand, since the contraction force is relatively small in the central portion and the resistance force against the deformation of the entire film is relatively small, the deformation in the upward direction of the film is also promoted. As described above, the use of the present invention has the effect of increasing the upward deformation of the film in both the central portion and the peripheral portion, as in the above embodiment. This effect is equally effective whether the initial shape is a flat surface or a curved surface. As described above, by using the present invention, it is possible to obtain a larger deformation than the conventional technique.

  Another embodiment of the present invention is shown in FIG. The film configuration is composed of a tensile film 41 and a film thickness adjusting layer 32 of a compressed film from the bottom. For the same reason as described in FIG. 2, the entire film has a downwardly convex shape. In this embodiment of the present invention, the film thickness in the peripheral part is relatively smaller than that in the central part, and the film thickness is relatively thick in the central part. While suppressing the downward deformation of the film, the compression force is relatively large at the center, and the resistance force against the deformation of the entire film is relatively large. To do. As described above, the use of the present invention has an effect of suppressing downward deformation of the film in both the central portion and the peripheral portion. Thus, by using this invention, the deformation | transformation which is too big by internal stress can be suppressed and a desired shape can be obtained.

  Another embodiment of the present invention is shown in FIG. In FIG. 5, the film structure is composed of a compression film 41 and a tensile film thickness adjusting layer 32 from the bottom. In this case, for the same reason as described in FIG. 3, the entire film has an upwardly convex shape. Therefore, when the present invention is used, the film thickness is relatively thinner in the peripheral part than in the central part, and the film thickness is relatively thick in the central part. On the other hand, the contraction force is relatively large in the central portion, and the resistance force against the deformation of the entire film is relatively large. Therefore, the upward deformation of the film is also suppressed. As described above, by using the present invention, as in the above embodiment, the film can be prevented from being deformed in the upward direction in the central portion and the peripheral portion, and a desired shape can be obtained.

  In the above explanation, a film having two types of internal stresses, a compression film and a tensile film, is simply laminated. However, in general, a case where the film is composed of either a compression film or a tension film, or a compression film is used. The same idea can be applied when a membrane and a tensile membrane are mixed.

In the case of manufacturing an aberration correction element, materials and manufacturing conditions are limited. Even in the case where only a flat surface can be manufactured with the conventional technology, a shape that is greatly deformed by using the film thickness adjusting layer according to the present invention is thus obtained. Can be produced. Of course, even when a deformed shape can be obtained by the conventional technique, a larger deformation is possible by using the present invention. This means that the curvature of the reflecting surface of the aberration correction element can be increased, and thus there is an effect that the aberration correction range becomes larger than that of the prior art. In addition, by using the present invention, even when there is a tendency to become too large due to internal stress, deformation can be suppressed and a desired shape can be obtained.

  Furthermore, the present invention has the effect of finely adjusting the initial shape. In order to hold the aberration correction element using a thin film originally, it is necessary to fix the peripheral portion. Therefore, the deformed shape is inevitably a Gaussian shape. However, for example, when correcting spherical aberration, the reflection surface of the aberration correction element needs to be a spherical surface, and a part of the Gaussian-type reflective film must be a spherical surface. Even in such a case, if the present invention is used, an arbitrary initial shape can be obtained by designing the shape of the film thickness adjusting layer, and a spherical shape can be freely created. Furthermore, by designing the film thickness adjusting layer and making many portions of the Gaussian shape spherical, it is possible to increase the number of elements and reduce the cost of the elements. If the initial shape can be designed arbitrarily, even when an electric field is applied to the piezoelectric film, it is deformed based on the shape, so that the designed shape can be obtained regardless of whether the voltage is on or off. Further, when it is necessary to correct aberrations other than spherical aberration, such as coma, if the present invention is used, the thickness adjustment layer can be corrected by designing it according to the wavefront shape to be corrected. More generally, it is possible to correct arbitrary aberrations by designing in a shape similar to the basis function of Zernike expansion.

  A method for producing the film thickness adjusting layer according to the present invention will be described. When using a semiconductor process, first a film with a uniform film thickness is formed as in the prior art, a resist is applied, and then a curved surface with relatively rough discrete gradation by multiple exposure using a binary mask multiple times. It is possible to produce a resist having Finally, the resist shape can be transferred by etching. A more effective method is to perform gray scale exposure of the resist using a gray scale drawing apparatus capable of changing the exposure intensity. In this method, the number of gradations can be increased, so that although it is discrete, a substantially continuous curved surface can be obtained. In addition to the method of drawing directly on the resist, it is also possible to expose the resist using a gray scale mask whose transmittance changes discretely or virtually continuously. In this case, when a gray scale mask is used together with a stepper having a reduction optical system, productivity can be improved and cost can be reduced.

  In the case where the film thickness adjusting layer is provided on the cavity side separately from the method using the gray scale resist or the gray scale mask, the film thickness adjusting layer can be produced by utilizing the shadow effect of the cavity. When producing a convex film thickness adjusting layer, after forming the cavity, the film is formed from the cavity side using sputtering, vapor deposition, CVD, etc., thereby forming a film with a non-uniform film thickness due to the shadow effect of the cavity. be able to. On the other hand, in the case of forming a concave film thickness adjusting layer, similarly, by performing etching such as RIE from the cavity side, etching can be performed with a non-uniform film thickness due to the shadow effect of the cavity.

Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 6 is a cross-sectional view of an aberration correction element according to the present invention. The substrate 35 is made of Si having a thickness of 298 μm, and a surface of both surfaces is formed with 1 μm thick thermally oxidized Si 36, and the substrate 35 is sandwiched between the thermally oxidized Si 36. From the bottom of the drawing on the substrate 35, Ir—Ti alloy of the lower electrode film 34a, 0.2 μm, PZT (lead zirconate titanate) of the piezoelectric film 31, 2 μm, Ti of the upper electrode film 34b, 0.2 μm are sputtered. Thus, 0.8 μm of the reflective film 33 made of a dielectric multilayer film made of TiO ₂ and TnO ₂ is sequentially laminated by vapor deposition.

A part of the thermally oxidized Si 36 at the bottom of the substrate, the substrate 35, and the thermally oxidized Si 36 at the top of the substrate are partially removed by RIE to form a circular cavity 39 having an inner diameter of 1.5 mm, and then the SiO of the film thickness adjusting layer 32 is formed by sputtering from the back side of the substrate. ₂ was formed. The film thickness adjusting layer 32 has a substantially spherical convex shape with a central portion of 0.2 μm and a peripheral portion of 0.8 μm due to the shadow effect of the cavity 39. The inside of the cavity 39 is composed of a thin film having a total thickness of only 3.4 μm at the center and 4 μm at the periphery, including the film thickness adjusting layer 32, the lower electrode film 34a, the piezoelectric film 31, the upper electrode film 34b, and the reflective film 33. ing. Before the film thickness adjusting layer 32 was formed, the inside of the cavity was substantially flat, but after etching, it was deformed upward and the radius of curvature at the center was 20 mm. When a DC voltage of 5 V was applied to this aberration correction element, it was deformed downward and the radius of curvature was 220 mm.

Another embodiment according to the present invention is shown in FIG. FIG. 7 is a cross-sectional view of an aberration correction element according to the present invention. The substrate 35 is made of Si having a thickness of 298 μm, and a surface of both surfaces is formed with 1 μm thick thermally oxidized Si 36, and the substrate 35 is sandwiched between the thermally oxidized Si 36. From the bottom of the drawing on the substrate 35, Ir—Ti alloy of the lower electrode film 34a, 0.1 μm, PZT (lead zirconate titanate) of the piezoelectric film 31, 2 μm, Ti of the upper electrode film 34b, 0.4 μm are sputtered. Thus, the reflective film 33, 0.8 μm, made of a dielectric multilayer film made of TiO ₂ and TnO ₂ is sequentially laminated by vapor deposition. A circular cavity 39 having an inner diameter of 1.5 mm was formed by partially removing the thermally oxidized Si 36 at the bottom of the substrate, the substrate 35, and the thermally oxidized Si 36 at the top of the substrate in order. After the formation of the cavity, SiO ₂ of the film thickness adjusting layer 32 was newly formed by sputtering from the cavity side. Due to the shadow effect by the cavity, a substantially spherical film thickness adjusting layer 32 having a central portion of 0.9 μm and a peripheral portion of 0.1 μm was formed. Before the film thickness adjustment layer 32 was formed, the inside of the cavity was deformed downward with respect to the substrate, and the radius of curvature at the center was 200 mm. It was deformed into a convex shape, and the radius of curvature at the center was 32 mm. When a DC voltage of 5 V was applied, it was deformed upward and the curvature changed to 234 mm.

  Another embodiment according to the present invention is shown in FIG. FIG. 8 is a sectional view of an aberration correction element according to the present invention. Only the inside of the cavity is shown for simplicity. The substrate 35 is made of Si having a thickness of 278 μm, and a surface of both surfaces is formed with 1 μm thick thermally oxidized Si 36, and the substrate 35 is sandwiched between the thermally oxidized Si 36. From the bottom of the drawing, Ir—Ti alloy of the lower electrode film 34a, 0.2 μm, PZT (lead zirconate titanate) 1 μm of the piezoelectric film 31, Ti of the upper electrode film 34b, 0.1 μm are sputtered on the substrate from the bottom. Ag reflective films 33 and 1 μm were sequentially stacked by vapor deposition. The thermally oxidized Si 36 and the substrate 35 below the substrate were partially removed by RIE, and the circular cavity 39 having an inner diameter of 1.5 mm was formed while leaving the thermally oxidized Si above the substrate. After the formation of the cavity, a resist was applied on the remaining thermally oxidized Si, and a convex film thickness adjusting layer 32 was formed by a gray scale exposure apparatus with 8 discrete gradations.

  FIG. 9 is a contour diagram showing the thickness distribution after the film thickness adjusting layer 32 is produced. The film thickness adjusting layer 32 had a film thickness of 1 μm at the central part and a film thickness of 0.2 μm at the peripheral part. When the radius of curvature at the center after fabrication was 80 mm and the film thickness adjusting layer 32 was not formed, the radius of curvature of 15 mm could be reduced, and the curvature as designed could be achieved.

As described above, the case where the beam is incident on the aberration correction element perpendicularly has been described, but even when the beam is incident obliquely, the same argument can be made by changing the shape of the aberration correction element to an ellipse, and the beam incident at any angle. The present invention is preferably applied to the above. Moreover, only the example in which the reflecting surface is concave has been shown, but the present invention is also effective for a convex reflecting surface depending on the optical system. The above example is only a preferable example. As long as the present invention is used, dynamic spherical aberration can be effectively corrected by using any practical piezoelectric film 31 and elastic body. For example, the piezoelectric film 31 includes PZT (lead zirconate titanate), quartz, LiNbO ₃ , LiTaO ₃ , KNbO ₃ , ZnO, AlN, Pb (Zr, Ti) O ₃ , PVDF (polyvinylidene fluoride), and the like. Can be used. Moreover, Ni, Ti, Cu, Cr, Au, Pt, etc. can be used as an electrode. Reflective films include dielectric multilayer films using oxides such as SiO ₂ , TiO ₂ , and TnO ₂ , noble metals such as Au, Ag, and Cu that take into account corrosive properties, and various types according to the reflectivity of the beam wavelength used Can be selected. The example of the shape of the diaphragm is circular, but the effect of the present invention can be obtained with any shape as long as it is an axisymmetric polygon. In this embodiment, the optical pickup has been described. However, the present invention can naturally be applied to other optical devices.

  As described above, according to the present invention, it is possible to perform highly accurate spherical aberration correction that is very small, power-saving, and excellent in responsiveness. Therefore, a CD / DVD drive recorder, decoder, CD / It can be used for an optical pickup used in a DVD drive or the like, in particular, an optical pickup using a blue laser or an optical apparatus that requires correction of aberration.

The figure which shows the aberration correction element by this invention The figure of the aberration correction element in one embodiment of the present invention The figure of the aberration correction element by another embodiment of the present invention The figure of the aberration correction element by another embodiment of the present invention The figure of the aberration correction element by another embodiment of the present invention The figure which shows embodiment of this invention The figure which shows another embodiment of this invention The figure which shows another embodiment of this invention Contour diagram showing thickness distribution of film thickness adjusting layer in the present invention The figure which shows the optical system containing the aberration correction element in this invention The figure which shows operation | movement of the aberration correction element by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Aberration correction element 11 Optical disk 12 Objective lens 13 1/4 wavelength plate 14 1/4 wavelength plate 15 Polarizing beam splitter 16 Light receiving element 17 Rising mirror 18 Light source 20 Driver IC
DESCRIPTION OF SYMBOLS 21 Arithmetic apparatus 31 Piezoelectric film 32 Film thickness adjustment layer 33 Reflective film 34 Electrode film 34a Lower electrode film 34b Upper electrode film 35 Substrate 36 Thermal oxidation Si
37 Electrode pad 38 Electrode pad 39 Cavity 40 Beam 41 Tension film 42 Reaction force 43 Couple 50 Optical disk substrate 51 First surface 52 Second surface 53 Optical disk surface 54 Power supply

Claims (15)

A substrate, a cavity part, a film thickness adjusting layer having a non-uniform thickness of an elastic body provided facing the cavity part, a piezoelectric film provided facing the cavity part, and the piezoelectric film An aberration correction element comprising: a pair of electrode films sandwiching an optical film; and an optical reflection film. The aberration correction element according to claim 1, wherein the film thickness adjusting layer changes in a discrete gradation from 0.01 μm to 10 μm. 2. The aberration correction element according to claim 1, wherein the film thickness distribution of the film thickness adjusting layer is axisymmetric. The aberration correction element according to claim 1, wherein the film thickness distribution of the film thickness adjusting layer is a convex shape that is thick at the center and thin at the periphery. The aberration correction element according to claim 1, wherein the film thickness distribution of the film thickness adjusting layer is a concave shape that is thin at the center and thick at the periphery. 6. The aberration correction element according to claim 1, wherein the film thickness adjusting layer is formed by a semiconductor process using a gray scale resist. 7. The aberration correction element according to claim 6, wherein the gray scale resist is formed directly or indirectly by a drawing exposure apparatus using a laser or an electron beam. The aberration correction element according to claim 6, wherein the gray scale resist is formed using a gray scale mask. 6. The aberration correction element according to claim 1, wherein the film thickness adjusting layer has a shape similar to a basis function in Zernike expansion. The aberration correction element according to claim 1, wherein the film thickness adjusting layer is a film other than a reflective film. The aberration correction element according to claim 1, wherein the film thickness adjusting layer is provided on a cavity side, and the film thickness adjusting layer is formed by a shadow effect of the cavity by using an isotropic film forming method. 2. The aberration correction element according to claim 1, wherein the film thickness adjusting layer is provided on the cavity side, and the film thickness adjusting layer is formed by a shadow effect of the cavity using an isotropic etching method. 2. The aberration correction element according to claim 1, wherein the film thickness adjusting layer is processed and formed by a picosecond laser or a femtosecond laser. An electronic apparatus comprising the aberration correction element according to claim 1. An optical apparatus comprising the aberration correction element according to claim 1.

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