JP3800288B2 - Light modulation device and display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light modulation device and a display device for performing display by modulating incident light by deformation of a mirror.
[0002]
[Prior art]
Conventionally, as a light modulation device for modulating and displaying light, for example, a device that modulates incident light by applying a voltage to an electrode provided on a substrate and tilting a mirror by its suction force or the like, There is known a technique in which a mirror is provided on a piezoelectric element in which a piezoelectric layer is sandwiched between a pair of electrode films, and the incident light is modulated by tilting the mirror by deforming the piezoelectric element.
[0003]
In addition, as a method using a piezoelectric element, a mirror film made of a thin film or the like is formed on the surface of a cantilevered piezoelectric element as shown in Japanese Patent Publication No. 9-504387, and the piezoelectric element is deformed. Thus, there has been proposed a technique in which the mirror film is bent to change the direction of incident light.
[0004]
[Problems to be solved by the invention]
However, in any case, a light modulation device using such a piezoelectric element has a cantilever-like structure that supports one end portion in the longitudinal direction of the piezoelectric element. Therefore, there is a problem in that the modulation performance is low because the light is changed in direction by being deformed in only one direction along the direction.
[0005]
In addition, a light modulation device that tilts a mirror by electrostatic attraction force or the like has a problem that it is difficult to obtain a high-gradation image because the mirror is digitally turned on and off.
[0006]
In view of such circumstances, it is an object of the present invention to provide a light modulation device that improves the light collecting performance by increasing the curvature change of the reflecting surface and improves the modulation performance, and a display device using the same. .
[0007]
[Means for Solving the Problems]
According to a first aspect of the present invention for solving the above-mentioned problems, a mirror element having a piezoelectric film composed of a piezoelectric layer and first and second electrodes sandwiching the piezoelectric layer and having a mirror film structure for reflecting light, and In the light modulation device having a drive element provided corresponding to the mirror element, the piezoelectric element has at least two through holes penetrating in the thickness direction of the mirror element, and the first and second Each of the electrodes extends to the substrate through the through hole and includes first and second extending portions for supporting the mirror element on the substrate. .
[0008]
In the first aspect, since the piezoelectric element constituting the mirror element is supported by the first and second extending portions and the entire outer edge portion of the mirror element is not fixed, the deformation efficiency of the piezoelectric element is improved.
[0009]
According to a second aspect of the present invention, in the first aspect, at least a part of the first and second extending portions is extended in a direction intersecting with a plane direction of the piezoelectric element. It is in the light modulation device characterized by this.
[0010]
In the second aspect, the mirror element is supported on the surface of the substrate while maintaining a space between the mirror element and the substrate.
[0011]
According to a third aspect of the present invention, in the first or second aspect, the mirror film structure is provided with a communication hole communicating with the through-hole independently from an outer edge portion. It is in.
[0012]
In the third aspect, the mirror film structure effectively reflects light at portions other than the communication hole.
[0013]
According to a fourth aspect of the present invention, in any one of the first to third aspects, the first and second extending portions are provided one by one in line symmetry with respect to one diagonal line of the mirror element. And the light modulation device is arranged near the center.
[0014]
In the fourth aspect, the piezoelectric element is deformed into a concave surface using the substantially central portion as a fulcrum.
[0015]
A fifth aspect of the present invention is the mirror film structure according to any one of the first to fourth aspects, wherein a voltage is applied to the piezoelectric layer of the piezoelectric element so that a region between the through holes serves as a fulcrum. The light modulation device is characterized in that light incident on the mirror film structure is modulated.
[0016]
In the fifth aspect, since the change in curvature due to the driving of the piezoelectric element becomes large, it is possible to improve the light condensing performance of light incident on the mirror film structure.
[0017]
According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the first and second extending portions are electrically connected to the driving element. On the device.
[0018]
In the sixth aspect, since the piezoelectric element and the driving element are electrically connected by the first and second extending portions, the wiring structure is simplified.
[0019]
According to a seventh aspect of the present invention, in any one of the first to sixth aspects, the first and second extending portions form the first and second electrodes on the patterned sacrificial layer. It is in the light modulation device characterized by being formed.
[0020]
In the seventh aspect, the first and second extending portions can be easily formed by using the sacrificial layer.
[0021]
According to an eighth aspect of the present invention, in any one of the first to seventh aspects, the surface of the piezoelectric element on the substrate side has an elastic plate and the other surface side has the mirror film structure. It is in the light modulation device characterized by this.
[0022]
In the eighth aspect, since the first and second extending portions are extended on the elastic plate side provided on one surface side of the piezoelectric element, the piezoelectric element is deformed with the elastic plate side as a fulcrum, and the other The mirror film structure in the direction is deformed.
[0023]
According to a ninth aspect of the present invention, in the eighth aspect, the mirror film structure of the piezoelectric element is configured by the second electrode on the other surface side or a reflective film provided on the second electrode. In the light modulation device characterized.
[0024]
In the ninth aspect, the second electrode or the reflective film of the piezoelectric element reflects light.
[0025]
A tenth aspect of the present invention is the light modulation device according to any one of the first to ninth aspects, wherein the driving element is a transistor provided on the substrate.
[0026]
In the tenth aspect, the piezoelectric element of each mirror element is driven via a transistor provided on the substrate.
[0027]
According to an eleventh aspect of the present invention, there is provided a light modulation device according to any one of the first to tenth aspects, a light source, light from the light source incident on the light modulation device, and the piezoelectric element of the light modulation device. An optical system that emits only one of driving and non-driving is provided.
[0028]
In the eleventh aspect, a display device that can be reduced in size and saved in space can be realized by using a light modulation device in which the change in curvature of the mirror film structure is increased to improve the light collecting performance.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments.
[0030]
(Embodiment 1)
FIG. 1 is a perspective view schematically showing the light modulation device according to the first embodiment, and FIG. 2 is a top view and a cross-sectional view showing one mirror element thereof.
[0031]
As shown in FIG. 1, the light modulation device 10 of this embodiment includes, for example, a mirror substrate 11 formed of a silicon (Si) substrate having a thickness of 500 μm and a two-dimensional array on the mirror substrate 11. The mirror element 20 is provided.
[0032]
These mirror elements 20 are provided, for example, in a two-dimensional array of 1280 × 1024 elements. For example, as shown in FIG. 2, the lower electrode film 32, the piezoelectric layer 33, and the upper layer formed on the elastic plate 31 are provided. A piezoelectric element 30 having an electrode film 34 is included. In the present embodiment, the upper electrode film 34 constituting the piezoelectric element 30 also serves as a reflective film that reflects incident light. Of course, a reflective film may be provided separately from the upper electrode film 34.
[0033]
Further, the surface of each mirror element 20 has, for example, a substantially square shape with a side of about 20 μm, and in this embodiment, a rectangular penetration that penetrates in the thickness direction is provided on one side of the mirror element 20 on the diagonal line. The holes 21 and 22 are provided so as to be line symmetric with respect to the other diagonal line of the mirror element 20.
[0034]
Each of the lower electrode film 32 and the upper electrode film 34 constituting the piezoelectric element 30 of each mirror element 20 has a mirror substrate 11 having substantially the same width as one side of the through holes 21 and 22 from the through holes 21 and 22 of the piezoelectric element 30. A lower electrode extending portion 41 and an upper electrode extending portion 42 extending to the top are provided. The lower electrode extending portion 41 and the upper electrode extending portion 42 are partially extended in a direction intersecting the plane direction of the piezoelectric element 30, and a space is provided between the mirror element 20 and the mirror substrate 11. Supports in a held state. That is, these mirror elements 20 are deformed with the region between the through holes 21 and 22 as a fulcrum. The mirror substrate 11 is provided with a driving element 50 such as a transistor for driving the piezoelectric element 30 corresponding to each piezoelectric element 30. The lower electrode extending portion 41 and the upper electrode extending portion 42 are , And each drive element 50 is electrically connected.
[0035]
Here, the widths of the lower electrode extending portion 41 and the upper electrode extending portion 42 are not particularly limited, but in order to improve the deformation efficiency of the piezoelectric element 30, the mirror element 20 is made thin enough to be supported and fixed. It is preferable. Further, the film thickness of the lower electrode extending portion 41 and the upper electrode extending portion 42, that is, the lower electrode film 32 and the upper electrode film 34 is not particularly limited as long as the mirror element 20 can be supported and fixed. It may be determined appropriately in consideration of the distortion of the above.
[0036]
Further, the size of the opening of the through holes 21 and 22 in which the lower electrode extending portion 41 and the upper electrode extending portion 42 are extended does not contact at least the lower electrode extending portion 41 and the upper electrode extending portion 42. The opening area is not particularly limited, but it is preferable to make the opening area as small as possible in order to increase the area of the reflecting surface. In addition, since the deformation amount, deformation direction, and the like of the mirror element 20 change depending on the distance between the through holes 21 and 22, it is necessary to appropriately determine the positions of the through holes 21 and 22 in consideration of these.
[0037]
Moreover, although the manufacturing method of such a light modulation device 10 of this embodiment is not specifically limited, In this embodiment, it manufactured with the following processes. 3 and 4 are cross-sectional views showing a method for manufacturing the light modulation device of this embodiment.
[0038]
First, as shown in FIG. 3A, a drive element 50 made of a predetermined transistor is formed on a silicon substrate by a semiconductor process, and this is used as a mirror substrate 11. A sacrificial layer 60 is formed on the mirror substrate 11. The material of the sacrificial layer 60 is not particularly limited. For example, polysilicon or phosphorus-doped silicon oxide (PSG) is preferably used. In this embodiment, PSG having a relatively high etching rate is used.
[0039]
Next, as shown in FIG. 3B, the elastic plate 31 is formed on the sacrificial layer 60. The elastic plate 31 is patterned in a region corresponding to each drive element 50 to form elastic plate removing portions 31a and 31b. The material of the elastic plate 31 is a material that can be elastically deformed and has a predetermined rigidity, and is not particularly limited as long as it is a material that is not removed when the sacrificial layer 60 is etched in a later step. In this embodiment, after forming the zirconium layer, the elastic plate 31 made of zirconium oxide is formed by thermal oxidation in a diffusion furnace at 500 to 1200 ° C., for example.
[0040]
Next, as shown in FIG. 3C, the sacrificial layer 60 is etched from one elastic plate removing portion 31 a of the elastic plate 31 to the surface of the mirror substrate 11, so that the mirror substrate is formed in a region corresponding to the through hole 21. A sacrificial layer removing portion 61 exposing 11 was formed.
[0041]
Next, as shown in FIG. 3D, the lower electrode film 32 is formed over the entire surface of the sacrificial layer 60 and patterned. That is, the lower electrode film 32 formed on the bottom and one side wall of the sacrificial layer removing portion 61 is left as the lower electrode extending portion 41. The lower electrode extension portion 41 supports the mirror element 20 in a state where a space is maintained between the mirror element 20 and the mirror substrate 11 after the sacrificial layer 60 is completely removed in a later step.
[0042]
As a material of the lower electrode film 32, platinum or the like is suitable. As described later, when the piezoelectric layer 33 is formed by sputtering or a sol-gel method as described later, it is necessary to perform crystallization by firing at a temperature of about 600 to 1000 ° C. in an air atmosphere or an oxygen atmosphere after film formation. Because there is. That is, the material of the lower electrode film 32 must be able to maintain conductivity at such a high temperature and in an oxidizing atmosphere, particularly when lead zirconate titanate (PZT) is used as the piezoelectric layer 33. It is desirable that the change in conductivity due to diffusion of lead oxide (PbO) is small. For these reasons, in this embodiment, the lower electrode film 32 is formed by forming platinum by a sputtering method.
[0043]
Next, as shown in FIG. 4A, the piezoelectric layer 33 is formed over the entire surface of the sacrificial layer 60, and the piezoelectric layer in a region corresponding to the sacrificial layer removing unit 61 and the elastic plate removing unit 31b. 33 is removed, and through holes 21 and 22 are formed.
[0044]
The material of the piezoelectric layer 33 is preferably a lead zirconate titanate (PZT) -based material. In this embodiment, a so-called sol obtained by melting and dispersing a metal organic substance in a catalyst is applied and dried to be gelled, and further at a high temperature. It was formed using a so-called sol-gel method in which a piezoelectric layer 33 made of a metal oxide was obtained by firing. In addition, the film-forming method of this piezoelectric material layer 33 is not specifically limited, For example, you may form by sputtering method.
[0045]
Furthermore, after forming a lead zirconate titanate precursor film by a sol-gel method or a sputtering method, a method of crystal growth at a low temperature by a high-pressure treatment method in an alkaline aqueous solution may be used.
[0046]
In any case, the piezoelectric layer 33 formed in this way has crystals preferentially oriented unlike the bulk piezoelectric body, and in this embodiment, the piezoelectric layer 33 is formed in a columnar shape. Has been. Note that the preferential orientation refers to a state in which the orientation direction of the crystal is not disordered and a specific crystal plane is oriented in a substantially constant direction. A columnar thin film refers to a state in which substantially cylindrical crystals are aggregated over the surface direction with the central axis substantially coincided with the thickness direction to form a thin film. Of course, it may be a thin film formed of preferentially oriented granular crystals. Note that the thickness of the piezoelectric layer manufactured in this way in the thin film process is generally 0.2 to 5 μm.
[0047]
Next, as shown in FIG. 4B, the sacrifice layer 60 is exposed from the elastic plate removing portion 31 b to the surface of the mirror substrate 11 to expose the mirror substrate 11 in a region corresponding to the through hole 22. The removal part 62 was formed.
[0048]
Next, as shown in FIG. 4C, the upper electrode film 34 is formed over the entire surface of the sacrificial layer 60 and patterned. That is, the upper electrode film 34 formed on the bottom and one side wall of the sacrificial layer removing portion 62 is left as the upper electrode extending portion 42 and the contact portion with the lower electrode film 32 is removed. The upper electrode extending portion 42 supports the mirror element 20 in a state where the mirror element 20 and the mirror substrate 11 are kept in a space after the sacrificial layer 60 is completely removed in a later step.
[0049]
In the region between the through holes 21 and 22, the piezoelectric layer 33 is sandwiched between the lower electrode film 32 communicating with the lower electrode extending portion 41 and the upper electrode film 34 communicating with the upper electrode extending portion 42. The formed piezoelectric element 30 is formed. In addition, the end of the lower electrode film 32 on the lower electrode extension portion 41 side in this region is covered with the piezoelectric layer 33 to ensure insulation from the upper electrode extension portion 42.
[0050]
The upper electrode film 34 only needs to be a highly conductive material, and many metals such as aluminum, gold, nickel, and platinum, conductive oxides, and the like can be used. In the present embodiment, since the upper electrode film 34 also serves as a reflective film, a material having high reflectivity, for example, aluminum (Al) or silver (Ag) is formed by sputtering to form the upper electrode film 34.
[0051]
Next, as shown in FIG. 4D, the sacrificial layer 60 is removed by etching. In this embodiment, since PSG is used as the material of the sacrificial layer 60, etching can be performed with hydrofluoric acid or a mixed aqueous solution of ammonium fluoride and ammonium monohydrogen difluoride.
[0052]
Thus, the light modulation device 10 of the present embodiment in which the mirror element 20 is supported and fixed with the space between the lower electrode extending portion 41 and the upper electrode extending portion 42 supported by the mirror substrate 11. Is manufactured.
[0053]
Here, the operation of the light modulation device of the present embodiment formed as described above will be described. FIG. 5 is a diagram schematically showing the light modulation device of this embodiment and the optical path of light irradiated on the light modulation device.
[0054]
The light modulation device 10 modulates light by deforming the mirror element 20. In this embodiment, the mirror element 20 is substantially flat when no voltage is applied to the piezoelectric element 30. When a voltage is applied to the piezoelectric element 30 by switching of the driving element 50, the piezoelectric layer 33 of the piezoelectric element 30 contracts in the in-plane direction, and the mirror element 20 uses the region between the support portions as a fulcrum as a mirror substrate. The upper electrode film 34 is formed as a concave mirror.
[0055]
In addition, the light modulation device 10 according to the present embodiment includes a light-shielding dot array 100 at a position facing the mirror element 20, for example, as shown in FIG. The light-shielding dot array 100 is made of, for example, a transparent substrate such as glass, and light-shielding dots 101 are provided to face each mirror element. The light shielding dots 101 are made of a light absorber, and examples thereof include carbon black, black pigment, and black dye dispersed in a resin. The light-shielding dot array 100 is provided in the vicinity of the focal point of the mirror element 20B in which each light-shielding dot 101 is deformed. For example, in the configuration of the present embodiment, since the deformation amount of the mirror element 20 is 0.2 μm, the light shielding dots 101 are provided at a distance of about 0.2 mm from each mirror element 20.
[0056]
In such a configuration, in the state where no voltage is applied to the piezoelectric element 30, the incident light 90 enters the upper electrode film 32 that also serves as the reflection film of the mirror element 20 </ b> A, so that the incident light 90. Is emitted in substantially the same optical path as the incident optical path. On the other hand, when the voltage is applied to the piezoelectric element 30 by the driving element 50, the mirror element 20 is deformed to become a concave mirror, and therefore after being reflected, the mirror element 20B is condensed in the focal direction of the deformed mirror element 20B. In this embodiment, since the light shielding dots 101 are provided in the vicinity of the focal point of the deformed mirror element 20 as described above, the incident light 90 is reflected and then condensed on the light shielding dots 101 to return to the incident direction. There is no. That is, when such a light modulation device 10 is used for a display device or the like, the ON / OFF control of the incident light 90 can be easily performed without applying a voltage to the piezoelectric element 30. In the above-described example, the piezoelectric element 30 is turned on when it is not deformed, and is turned off when it is deformed. Of course, the piezoelectric element 30 can be set to be reversed.
[0057]
In the light modulation device of the present embodiment described above, the area of the reflection surface that reflects incident light can be increased as compared with the light modulation device having a conventional structure. That is, the aperture ratio of the reflection surface is large, and the reflection efficiency can be improved. Further, since the incident light is reflected by deforming the piezoelectric element, the analog mirror tilt angle can be controlled, and a high gradation image can be obtained. Furthermore, since the lower electrode extending portion and the upper electrode extending portion are electrically connected to the driving element on the mirror substrate, the wiring structure of the piezoelectric element can be simplified.
[0058]
(Embodiment 2)
FIG. 6 is a top view of the light modulation device according to the second embodiment.
[0059]
In the present embodiment, two lower electrode extending portions 41 and two upper electrode extending portions 42 are provided. As shown in FIG. 6, two through holes 21 are formed along each diagonal line of the mirror element 20 </ b> C. Are provided adjacent to each other, and through holes 22 are provided at positions opposite to the respective through holes 21. Except that the respective lower electrode extending portions 41 and upper electrode extending portions 42 are formed in regions facing the through holes 21 and 22, and the mirror element 20C is supported and fixed at four locations, the embodiment 1 It is the same.
[0060]
In such a configuration of the present embodiment, since the through holes 21 and 22 have a substantially equal distance with respect to all outer edge portions of the substantially square-shaped piezoelectric element 30, the lower electrode 32 and the upper electrode When a voltage is applied to 34 to deform the piezoelectric film 33, the mirror element 20D becomes a concave mirror having a substantially uniform curved surface. Therefore, the mirror element 20 has a high degree of concentration of the reflected light. Further, since the number of the lower electrode extending portions 41 and the upper electrode extending portions 42 for supporting and fixing the mirror element 20 is doubled, the rigidity of each lower electrode extending portion 41 and the upper electrode extending portion 42 is reduced. Can do. In other words, the widths of the lower electrode extending portions 41 and the upper electrode extending portions 42 can be formed narrow. From this, since the opening area of the through-holes 21 and 22 can be made small, while the deformation amount of the mirror element 20 becomes large, the condensing degree can be improved.
[0061]
The positions of the through holes 21 and 22 are not particularly limited. For example, the two through holes 21 are provided so as to be symmetrical with respect to the other diagonal along one diagonal of the mirror element 20C. The two through holes 22 may be provided along the other diagonal line so as to be symmetrical with respect to the diagonal line provided with the through hole 21.
[0062]
Moreover, the electrode extended from each through-hole 21 and 22 is not specifically limited, For example, among the four through-holes 21 and 22, the lower electrode 32 is extended from one through-hole, and the lower electrode is extended. Even if the portion 41 is formed, and the upper electrode 34 is formed by extending the upper electrode 34 from the remaining three through holes, the same effect as the above-described embodiment can be obtained.
[0063]
(Other embodiments)
Although the embodiments of the present invention have been described above, the light modulation device of the present invention is not limited to the above-described embodiments, but in any case, the curvature change of the reflecting surface is increased, and the area of the reflecting surface is increased. Is increased, the light collecting performance is improved.
[0064]
In the embodiment described above, the mirror element 20 is substantially square, but is not limited thereto, and may be any shape such as a polygon or a circle.
[0065]
In the above-described embodiment, the upper electrode film 34 that also serves as a reflective film acts as a concave mirror. However, the present invention is not limited to this, and the film forming conditions and the like may be appropriately adjusted so as to act as a convex mirror. .
[0066]
Furthermore, in the above-described embodiment, the through holes 21 and 22 are rectangular. However, the shape and size of the through holes 21 and 22 are not particularly limited, and may be any shape such as a polygon or a circle. Good. In addition, the through holes 21 and 22 may be long holes. In this case, the portions extending in the plane direction of the lower electrode extending portion 41 and the upper electrode extending portion 42 have a long structure.
[0067]
Below, the structural example of the light modulation device using other than the light-shielding dot array and the structural example at the time of making it act as a convex mirror are shown. The present invention has the effect of eliminating the need for a special optical system that condenses incident light on the reflecting surface by improving the condensing performance, but an optical system that condenses incident light may be used. Shows such a configuration.
[0068]
FIG. 7 shows a schematic configuration of a light modulation device provided with a pinhole array 110 and a microlens array 120 instead of the light-shielding dot array 100 described above. Here, the pinhole array 110 has a pinhole 111 at a position facing each mirror element 20, and each microlens array 120 has a convex lens 121 at a position facing each mirror element 20. Each pinhole 111 of the pinhole array 110 is provided near the focal point of the deformed mirror element 20B.
[0069]
In such a light modulation device, the light incident on the deformed mirror element 20B returns through the pinhole 111 of the pinhole array 110, but the light incident on the undeformed mirror element 20A is a light shielding portion of the pinhole array 110. Blocked at 112. That is, in this example, contrary to the above-described example, the case where the mirror element 20 is deformed is ON, and the case where it is not deformed is OFF.
[0070]
Note that even if the mirror element 20 is convexly deformed to the side opposite to the mirror substrate 11 and acts as a convex mirror, a light modulation device can be obtained. An example of a display device using such a light modulation device will be described later.
[0071]
In each of the embodiments described above, it is considered that when the piezoelectric element 30 is deformed, the mirror substrate 11 facing the piezoelectric element 30 is charged, and the deformation of the piezoelectric element 30 may be hindered by electrostatic force. . Therefore, in order to solve such a problem, in addition to the above-described configuration, the mirror substrate 11 facing the lower electrode film 32 or the upper electrode film 34 of the piezoelectric element 30 is further replaced with the lower electrode film 32 or the upper surface facing each other. The potential may be substantially the same as that of the electrode film 34. That is, when the opposing electrodes are grounded by the common electrode, the mirror substrate 11 is also grounded. Thereby, charging due to the potential difference between the electrode of the piezoelectric element 30 and the mirror substrate 11 does not occur, deformation of the mirror element 20 is not hindered, and a decrease in the displacement amount of the mirror element 20 can be suppressed.
[0072]
Further, for example, a counter electrode is provided on a mirror substrate facing the lower electrode film 32 or the upper electrode film 34, and the deformation of the piezoelectric element 30 is assisted between the counter electrode and the lower electrode film 32 or the upper electrode film 34. A voltage may be applied so that an electrostatic force is generated in the direction in which it is generated. In such a configuration, the amount of displacement of the mirror element 20 can be further increased, the light collection rate can be further increased, and the SN ratio can be improved.
[0073]
The light modulation device of the present invention having each configuration described above is used as a part of a display device, for example.
[0074]
8 to 10 show an example of a display device using the light modulation device of the present invention. 8 to 10 are schematic cross-sectional views of an optical system constituting the display device, and a lens, a light modulation device, and the like are greatly simplified.
[0075]
The display device shown in FIG. 8 includes a metal halide lamp 210 that is a light source and a reflector 211 having a radiation surface shape, a half mirror 220 that makes light from the metal halide lamp 210 incident on the light modulation device 10, and an output from the light modulation device 10. A projection lens 230 that forms an image of incident light and a screen 240 that displays an image formed by the projection lens 230 are provided.
[0076]
Such a display device has a metal halide lamp 210 that is a light source, and light emitted from the metal halide lamp 210 is reflected by the reflector 211 to be incident on the half mirror 220 and reflected by the half mirror 220. Is incident on the light modulation device 10. The half mirror 220 may be a cube type half prism.
[0077]
Among the mirror elements 20 constituting the light modulation device 10, the mirror element 20B that is driven and deformed via the drive element 50 functions as a concave mirror, and the light incident on the deformed mirror element 20B is reflected and shielded. It is condensed toward the dots 101 and does not return to the half mirror 220 direction. On the other hand, the light incident on the undeformed mirror element 20A is reflected and imaged on the screen 240 which is an image plane by the projection lens 230.
[0078]
With the configuration of the optical system as described above, each mirror element 20 constituting the light modulation device 10 corresponds to a pixel on the screen 240, and the mirror element 20 is turned on and off, that is, not deformed or deformed. The display image on the screen 240 can be changed.
[0079]
As the screen 240, a reflective screen or a transmissive screen can be used.
[0080]
In the optical system shown in FIG. 8, only about half of the light emitted from the light source 210 illuminates the light modulation device 10 by the half mirror 220, and the other half is wasted through the half mirror 220. Light. Furthermore, only half of the light reflected by the light modulation device 10 passes through the half mirror 220 and travels toward the projection lens 230. That is, the light that reaches the screen 240 from the light source is attenuated to about ¼ of the light emitted from the light source 210 even if ideally estimated that there is no loss in the middle.
[0081]
In the display device shown in FIG. 9, the energy radiated from the light source is guided to the screen 240 in principle without loss by using three polarizing beam splitters 221, 222, and 224 instead of the half mirror 220. .
[0082]
As shown in the drawing, light emitted from a metal halide lamp 210 as a light source is reflected by a parabolic reflector 211 and converted into substantially parallel light, and enters a first polarization beam splitter 221. Hereinafter, it is assumed that the polarization beam splitter 221 transmits P-polarized light and reflects S-polarized light.
[0083]
Since the light emitted from the light source 210 is natural light whose vibration direction is in a random direction, the P-polarized component (indicated by p in the figure) is transmitted through the first polarizing beam splitter 221 and the S-polarized component ( Is reflected). The reflected S-polarized component light enters the adjacent second polarizing beam splitter 222, is reflected there, and exits the second polarizing beam splitter 222 as S-polarized light. On the other hand, the P-polarized light transmitted through the first polarizing beam splitter 221 is converted into S-polarized light by the half-wave plate 223 provided on the exit surface of the first beam splitter 221. Therefore, the light incident on the third polarizing beam splitter 224 is aligned with the S-polarized light.
[0084]
All of the light incident on the third polarization beam splitter 224 as S-polarized light is reflected in the direction of the light modulation device 10, but 1 provided on the surface of the third polarization beam splitter 224 on the light modulation device 10 side. The light is converted into circularly polarized light by the / 4 wavelength plate 225 and is incident on the light modulation device 10.
[0085]
The light reflected by the reflecting film of the mirror element 20 constituting the light modulation device 10 becomes circularly polarized light that is polarized in the opposite direction to the circularly polarized light of the incident light, and this time becomes P-polarized light by the quarter wavelength plate 225. 3 is incident on the beam splitter 224. In principle, all the P-polarized light is transmitted without reaching the projection lens 230 without being reflected by the third beam splitter 224.
[0086]
As described above, by aligning the vibration direction of the light emitted from the light source, there is no loss of light as in the case of using a half mirror, and the energy emitted from the light source is guided to the screen without any loss in principle. Can do. That is, a display device capable of bright display can be configured.
[0087]
FIG. 10 shows a configuration of a display device according to another embodiment. This display device uses the light modulation device 10A that does not have the light-shielding dot array 100 and acts as a convex mirror when each mirror element 20 is driven, and the third polarizing beam splitter 224 and the projection lens of the device of FIG. A predetermined divergent light that passes through the third beam splitter 224 is transmitted to the projection lens 230 between the lens 250 and the minute mirror 251 that blocks parallel light. The projection lens 230 forms an image on the screen 240 with light that has passed through the lens 250 with a predetermined divergent light.
[0088]
In such a configuration, the light incident on the undeformed mirror element 20 </ b> A of the light modulation device 10 </ b> A is reflected as parallel light and reaches the lens 250, but this light is a minute mirror disposed in the vicinity of the focal point of the lens 250. The light is condensed and diverged by 251 and does not reach the screen 240. On the other hand, since the light incident on the deformed mirror element 20B reaches the lens 250 as divergent light emitted from the virtual light source 260, the light reaches the projection lens 230 without being blocked by the minute mirror 251 and is projected. As a result, an image is formed on the screen 240.
[0089]
In the above description, a display device using one light modulation device has been described as the display device. However, as conventionally known, three light modulation devices are used, and each light modulation device is It goes without saying that the present invention can also be used as a color display device that modulates red, green, and blue light, and color-synthesizes and projects the modulated light.
[0090]
【The invention's effect】
As described above, in the present invention, each of the first and second electrodes of the piezoelectric element constituting the mirror element is extended from each through hole provided on the diagonal line of the piezoelectric element. It was made to support and fix on a board | substrate by an installation part. Thereby, the end portion of the piezoelectric element becomes a free end, the deformation efficiency is improved, the area of the reflection surface of the mirror element can be increased, and incident light can be efficiently modulated.
[0091]
Further, since the incident light is reflected by deforming the piezoelectric element, the analog mirror tilt angle can be controlled, and a high gradation image can be obtained.
[0092]
Furthermore, the wiring structure of the piezoelectric element can be simplified by electrically connecting the first and second extending portions extending from the first and second electrodes to the driving element on the substrate. There is an effect that can be done.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an outline of a light modulation device according to a first embodiment of the invention.
FIGS. 2A and 2B are a top view and a cross-sectional view of a main part of the light modulation device according to the first embodiment of the invention. FIGS.
FIG. 3 is a cross-sectional view illustrating the method for manufacturing the light modulation device according to the first embodiment of the invention.
FIG. 4 is a cross-sectional view illustrating the method for manufacturing the light modulation device according to the first embodiment of the invention.
FIG. 5 is a schematic cross-sectional view of an optical system of the light modulation device according to the first embodiment of the invention.
FIG. 6 is a top view of main parts of an optical modulation device according to Embodiment 2 of the present invention.
FIG. 7 is a schematic cross-sectional view of an optical system of a light modulation device according to another embodiment of the present embodiment.
FIG. 8 is a schematic cross-sectional view of an optical system constituting a display device using a light modulation device according to another embodiment of the present invention.
FIG. 9 is a schematic cross-sectional view of an optical system constituting a display device using a light modulation device according to another embodiment of the present invention.
FIG. 10 is a schematic cross-sectional view of an optical system constituting a display device using a light modulation device according to another embodiment of the present invention.
[Explanation of symbols]
10 Light modulation device
11 Mirror substrate
20 mirror elements
21, 22 Through hole
30 Piezoelectric elements
31 Elastic plate
32 Lower electrode membrane
33 Piezoelectric layer
34 Upper electrode film
41 Lower electrode extension
42 Upper electrode extension
50 Drive elements

Claims (2)

A mirror element having a piezoelectric film composed of a piezoelectric layer and first and second electrodes sandwiching the piezoelectric layer and having a mirror film structure for reflecting light; and a drive element provided corresponding to the mirror element. In the light modulation device,
The piezoelectric element has at least two through holes penetrating in the thickness direction of the mirror element, and the first and second electrodes are respectively extended to the substrate through the through holes and An optical modulation device comprising first and second extending portions for supporting a mirror element on the substrate.   The light modulation device according to claim 1, a light source, and light from the light source is incident on the light modulation device and emits only one of the piezoelectric element of the light modulation device when driven or not driven. A display device comprising: an optical system.

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