JP3800292B2 - 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 reflection mirror.
[0002]
[Prior art]
Conventionally, as a light modulation device for performing display by modulating 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 electrostatic force, 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, since the light modulation device using such a piezoelectric element has a cantilever structure supporting one end in the longitudinal direction of the piezoelectric element, there is a problem that sufficient curvature cannot be obtained on the surface of the piezoelectric element. is there. Further, in order to obtain a sufficient curvature on the surface of the piezoelectric element, there is a problem that the length in the longitudinal direction of the piezoelectric element, that is, the length of the beam must be increased.
[0005]
In view of such circumstances, it is an object of the present invention to provide a light modulation device and a display device that improve curvature change and light collection performance.
[0006]
[Means for Solving the Problems]
A first aspect of the present invention that solves the above problems includes a mirror element having a piezoelectric element composed of a piezoelectric layer and a pair of lower and upper electrodes sandwiching the piezoelectric layer and having a mirror film structure that reflects light; In the light modulation device having a drive element provided corresponding to the mirror element, the mirror element has two support portions of outer edge portions facing each other in the in-plane direction across the center of the mirror element. The optical modulation device is characterized in that the piezoelectric element supported by the substrate and constituting the mirror element is provided only at the outer edge of the mirror element.
[0007]
In the first aspect, since the mirror element is supported by the substrate only at two points on the outer edge and the other part is a free end, the change in curvature can be increased, and the piezoelectric element can be connected to the mirror element. Since the film thickness of the other part is thin only provided at the outer edge part, the other part is easily deformed by driving the piezoelectric element, and the curvature change becomes larger.
[0008]
According to a second aspect of the present invention, in the first aspect, the length between the support portions of the mirror element is shorter than the length in a direction substantially perpendicular to the direction between the support portions. In the modulation device.
[0009]
In the second aspect, since the length between the free ends is longer than the length between the support portions, the deformation amount of the mirror element by driving the piezoelectric element is improved.
[0012]
In a preferred aspect of the present invention, the mirror element is deformed to the opposite side of the substrate with the support portion as a fulcrum by applying a voltage to the piezoelectric layer of the piezoelectric element. In the light modulation device, a portion other than the piezoelectric element is deformed to the substrate side.
[0013]
In this aspect, since the piezoelectric element of the mirror element and the other part are deformed in the opposite direction, the curvature change of the mirror element is further increased.
[0014]
In a preferred aspect of the present invention, there is provided a light modulation device characterized in that a surface area of a piezoelectric active portion which is a substantial driving portion of the piezoelectric element is 5 to 50% of a surface area of the mirror element.
[0015]
In such an aspect, the mirror element can be efficiently deformed by setting the ratio of the piezoelectric active portion of the mirror element within a predetermined range.
[0016]
In a preferred aspect of the present invention, the light modulation device is characterized in that a region other than the piezoelectric active portion which is a substantial drive portion of the piezoelectric element of the mirror element is composed of at least the lower electrode.
[0017]
In this aspect, since the film thickness of the region other than the piezoelectric active part of the mirror element is thin, the deformation amount is improved.
[0018]
In a preferred aspect of the present invention, the region other than the piezoelectric element of the mirror element includes the upper electrode and an elastic plate provided on the substrate side of the piezoelectric element.
[0019]
In this aspect, since the film thickness of the region other than the piezoelectric element of the mirror element is thin, the deformation amount is improved.
[0020]
In a preferred aspect of the present invention, the lower electrode is covered with the piezoelectric layer constituting the piezoelectric element except for the wiring lead portion.
[0021]
In this aspect, since the end surface of the lower electrode on the mirror element is covered with the piezoelectric layer, a short circuit between the lower electrode and the upper electrode is reliably prevented.
[0022]
According to a preferred aspect of the present invention, a recess is provided in a region corresponding to each mirror element of the substrate, and the mirror element is provided so as to close the recess of the substrate and is finally removed. The light modulation device is characterized in that the light modulation device is formed of a thin film formed in the above.
[0023]
In such an embodiment, when the sacrificial layer is filled in the recess, the mirror element can be easily formed in a region facing the recess by a thin film process.
[0024]
In a preferred aspect of the present invention, the piezoelectric element has an elastic plate on the substrate side.
[0025]
In this aspect, since the elastic plate is provided on the substrate side of the piezoelectric element, the piezoelectric element is deformed to the side opposite to the substrate.
[0026]
In a preferred aspect of the present invention, the piezoelectric element has the mirror film structure on a surface opposite to the substrate.
[0027]
In this aspect, since one surface side of the piezoelectric element is bonded to the substrate by the support portion, the piezoelectric element is deformed with the support portion as a fulcrum, and the mirror film structure on the other surface is deformed.
[0028]
According to a third aspect of the present invention, there is provided the light modulation device according to the first or second aspect, a light source, light from the light source incident on the light modulation device, and the piezoelectric element of the light modulation device. And an optical system that emits only one of reflected light during driving or non-driving.
[0029]
In the third aspect, a display device capable of projecting a clearer image can be realized by using a light modulation device that increases the curvature change of the mirror film structure to improve the light collecting performance.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments.
[0031]
(Embodiment 1)
FIG. 1 is a perspective view illustrating an outline of the light modulation device according to the first embodiment, and FIG. 2 is a top view and a cross-sectional view illustrating a mirror element in one pixel. 2B is a cross-sectional view taken along the line AA ′ in FIG. 2A, and FIG. 2C is a cross-sectional view taken along the line BB ′ in FIG.
[0032]
As shown in the figure, the light modulation device 10 of this embodiment includes a mirror substrate 11 and mirror elements 20 provided on the mirror substrate 11 in a two-dimensional array.
[0033]
The mirror substrate 11 is made of, for example, a silicon (Si) substrate having a thickness of 500 μm, and a recess 12 having an opening slightly larger than the mirror element 20 is formed in a region corresponding to each mirror element 20.
[0034]
Each mirror element 20 is provided in a two-dimensional array of, for example, 1280 × 1024 elements corresponding to each recess 12 on the mirror substrate 11, and two outer edge portions facing each other across the center of each mirror element 20. It is supported on the mirror substrate 11 by the point support portions 20a and 20b. In the present embodiment, each mirror element 20 has a substantially square shape with a side of about 20 μm, and one opposing corner is a support part 20a, 20b.
[0035]
In the present embodiment, the recess 12 of the mirror substrate 11 is basically a substantially square opening slightly larger than the mirror element 20, but one opposite corner is opposed to the mirror element 20. An overhang portion 13 is provided to project to the area. That is, portions of the mirror element 20 corresponding to the overhanging portion 13 are support portions 20a and 20b, respectively, and each mirror element 20 is mounted on the mirror substrate 11 only by the two support portions 20a and 20b at the outer edge portions. The other parts are all free ends.
[0036]
In addition, the structure of the support parts 20a and 20b of the mirror element 20 is not particularly limited, and may be any structure.
[0037]
Each mirror element 20 includes a piezoelectric element 30 formed of a lower electrode film 32, a piezoelectric layer 33, and an upper electrode film 34 formed on an elastic plate 31, as shown in FIG. In addition, in this embodiment, a piezoelectric element in a region where voltage distortion occurs due to application of voltage to both electrodes of the piezoelectric element 30, that is, a region facing the concave portion 12 of the mirror substrate 11, is referred to as a piezoelectric active portion 30a. In this embodiment, such a piezoelectric element 30 is formed only at the outer edge of each mirror element 20, and the part other than the piezoelectric active part 30 a of the mirror element 20 is constituted by an elastic plate 31 and a lower electrode film 32. The lower electrode film 32 also serves as a reflective film for reflecting incident light.
[0038]
Here, the piezoelectric elements 30 provided on the outer edge portions of the mirror elements 20 have a substantially uniform width so that the surface area ratio of the piezoelectric active portions 30a is about 5 to 50% of the surface area of the mirror elements 20. Preferably, the deformation efficiency of the mirror element 20 is improved.
[0039]
Further, the upper electrode film 34 constituting such a piezoelectric element 30 is an individual electrode of each piezoelectric element 30 and extends on the mirror substrate 11 through one support portion 20a of the mirror element 20, and C -It is electrically connected to a driving element (not shown) such as a MOS transistor. On the other hand, the lower electrode film 32 is a common electrode of each piezoelectric element 30 and extends on the mirror substrate 11 via the other support portion 20 b of the mirror element 20. It is connected.
[0040]
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 the method of manufacturing the light modulation device of this embodiment, and are cross-sectional views taken along the line AA ′ of FIG.
[0041]
First, as shown in FIG. 3A, in this embodiment, the mirror substrate 11 is a silicon single crystal substrate provided with a drive element composed of a C-MOS transistor. The mirror substrate 11 is patterned, A recess 12 having a predetermined shape is formed in a region where each mirror element 20 is formed.
[0042]
Next, as shown in FIG. 3B, the sacrificial layer 60 is filled in the recess 12. Although the method is not particularly limited, for example, in this embodiment, after the sacrificial layer 60 is formed on the entire surface of the mirror substrate 11, the sacrificial layer 60 in a region other than the concave portion 12 is removed by patterning and sacrificed in the concave portion 12. Layer 60 was filled.
[0043]
The material of the sacrificial layer 60 is not particularly limited. For example, polysilicon, phosphorus-doped silicon oxide (PSG), boron-phosphorus-doped silicon oxide (BPSG), or the like is preferably used. In this embodiment, the etching rate is relatively high. Fast PSG was used.
[0044]
Next, as shown in FIG. 3C, an elastic plate 31 is formed over the entire surface of the mirror substrate 11 and patterned for each mirror element 20 by etching or the like. At this time, at least the elastic plate 31 in the region facing the peripheral edge of each recess 12 is removed to form the elastic plate removing portion 31a, and a part of the sacrificial layer 60 is exposed.
[0045]
The material of the elastic plate 31 is not particularly limited as long as it is a material that can be elastically deformed and has a predetermined rigidity and is not removed when the sacrificial layer 60 is etched in a later step. In the embodiment, after the zirconium layer is formed with a thickness of about 0.2 μm, the elastic plate 31 is made of zirconium oxide by thermal oxidation in a diffusion furnace at 500 to 1200 ° C., for example.
[0046]
Next, as shown in FIG. 3D, the sacrificial layer 61 is further filled into the elastic plate removing portion 31a. Although the method is not particularly limited, for example, in this embodiment, after the sacrificial layer 61 is formed on the entire surface of the elastic plate 31, the sacrificial layer 61 other than the elastic plate removing portion 31a is removed.
[0047]
The sacrificial layer 61 is used to prevent the elastic plate removing portion 31a from being filled with each layer when forming each layer constituting the piezoelectric element 30 in a process described later.
[0048]
Next, as shown in FIG. 4A, a lower electrode film 32 is formed on the entire surface of the mirror substrate 11 and patterned.
[0049]
Further, as the material of the lower electrode film 32, platinum or the like is suitable. As will be described later, when the piezoelectric layer 33 is formed by a sputtering method or a sol-gel method, it is crystallized by firing at a temperature of about 600 to 1000 ° C. in an air atmosphere or an oxygen atmosphere after the film formation. It is necessary. 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.
[0050]
In the present embodiment, since the lower electrode film 32 also serves as a reflective film, it is desirable that the material has a high light reflectance. For these reasons, in this embodiment, the lower electrode film 32 is formed by forming platinum by a sputtering method.
[0051]
In the present embodiment, the lower electrode film 32 is formed on the elastic plate 31, but the present invention is not limited to this, and the lower electrode film 32 may also serve as the elastic plate 31.
[0052]
Next, as shown in FIG. 4B, a piezoelectric layer 33 is formed on the lower electrode film 32 and patterned corresponding to each piezoelectric element 30. That is, the piezoelectric layer 33 is formed only on the outer edge portion of each lower electrode film 32 patterned on each sacrificial layer 60.
[0053]
Here, the material of the piezoelectric layer 33 is preferably a lead zirconate titanate (PZT) -based material. A so-called sol in which a metal organic substance is dissolved and dispersed in a catalyst is applied, dried, gelled, and further baked at a high temperature. Thus, the piezoelectric layer 33 made of a metal oxide was obtained by using a so-called sol-gel method. The method for forming the piezoelectric film 33 is not particularly limited. For example, the piezoelectric film 33 may be formed by a spin coating method such as a sputtering method or a MOD method (organic metal thermal coating decomposition method).
[0054]
Further, after forming a lead zirconate titanate precursor film by a sol-gel method, sputtering method, MOD method or the like, a method of crystal growth at a low temperature by a high pressure treatment method in an alkaline aqueous solution may be used.
[0055]
In any case, the piezoelectric layer 33 formed in this way has crystals preferentially oriented unlike a 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.
[0056]
Next, as shown in FIG. 4C, the upper electrode film 34 is formed over the entire surface of the mirror substrate 11 and then patterned to form the upper electrode film 34 on each piezoelectric layer 33.
[0057]
The upper electrode film 34 only needs to be a highly conductive material, and many metals such as aluminum, gold, nickel, platinum, and silver, conductive oxides, and the like can be used. Similarly to the lower electrode film 32, the upper electrode film 34 may also serve as a reflective film. In this case, it is preferable to use a material that has conductivity and high light reflectance.
[0058]
Thereafter, as shown in FIG. 4 (d), the sacrificial layers 60 and 61 in each recess 12 are removed from the surface of the sacrificial layer 61 in the elastic plate removing portion 31a by etching, thereby supporting at two points on the outer edge portion. Thus, the mirror element 20 of the present embodiment is formed.
[0059]
In this embodiment, since PSG is used as the material of the sacrificial layer 60, etching is performed with a hydrofluoric acid aqueous solution. When polysilicon is used, etching can be performed with a mixed aqueous solution of hydrofluoric acid and nitric acid, or with an aqueous potassium hydroxide solution.
[0060]
Here, the operation of the light modulation device of the present embodiment formed as described above will be described. 5 is a schematic diagram illustrating a driving state of the light modulation device of the present embodiment, and FIG. 6 is a diagram schematically illustrating an optical path of light irradiated to the light modulation device of the present embodiment. .
[0061]
In the light modulation device of the present embodiment, the mirror element 20 is substantially flat when no voltage is applied to the piezoelectric element 30, and when the voltage is applied to the piezoelectric element 30 of the mirror element 20 and the piezoelectric element 30 is driven, the piezoelectric element 30. The piezoelectric layer 33 contracts in the in-plane direction, and as shown in FIG. 5, the outer edge portion of the mirror element 20 provided with the piezoelectric element 30 is away from the mirror substrate 11 (upward direction in the figure). Transforms into Further, the central portion of the mirror element 20 where the piezoelectric element 30 is not provided is deformed to the concave portion 12 side (downward in the figure) of the mirror substrate 11, opposite to the outer edge portion. That is, when the mirror element 20 is deformed, it acts as a substantially concave mirror, and the modulation efficiency of incident light can be improved.
[0062]
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 absorbing material, 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 20 in which each light-shielding dot 101 is deformed.
[0063]
In such a configuration, when no voltage is applied to the piezoelectric element 30, the incident light 70 enters the lower electrode film 32 that is a reflection film of the mirror element 20 at a substantially right angle. The light is emitted in substantially the same optical path as the incident optical path. On the other hand, since the mirror element 20 is deformed into a substantially concave mirror in a state where a voltage is applied to the piezoelectric element 30, it is condensed in the focal direction of the deformed mirror element 20 after being reflected. In this embodiment, since the light shielding dots 101 are provided near the focal point of the deformed mirror element 20 as described above, the incident light 70 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 70 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.
[0064]
As described above, in the present embodiment, the mirror element 20 is supported on the mirror substrate 11 by the two support portions 20a and 20b of the outer edge portions facing each other across the center thereof. Compared with the mirror element, a larger curvature change can be obtained. Further, since the piezoelectric element 30 is provided only at the outer edge portion of the mirror element 20, when the piezoelectric element 30 is driven, the mirror element 20 in a region other than the piezoelectric element 30 is displaced to the side opposite to the piezoelectric element 30. In addition, since the entire mirror element 20 acts as a concave surface, the light collecting performance is improved. Furthermore, since the piezoelectric element 30 provided in each mirror element 20 only needs to be relatively small, power consumption can be suppressed.
[0065]
In the present embodiment, the mirror element 20 is supported on the mirror substrate 11 at one opposite corner, but the present invention is not limited to this, and two points facing each other across the center of the mirror element 20. If so, it may be supported at any two points on the outer edge.
[0066]
(Embodiment 2)
FIG. 7 is a diagram illustrating the light modulation device according to the second embodiment. 7A is a top view showing a main part of the light modulation device, FIG. 7B is a cross-sectional view taken along the line CC ′, and FIG. 7C is a line DD ′. It is sectional drawing.
[0067]
In the present embodiment, as shown in FIG. 7, an upper electrode film 34 is provided on the entire surface of the mirror element 20A, and the upper electrode film 34 also serves as a reflective film that reflects light.
[0068]
That is, in the present embodiment, the upper electrode film 34 constituting the piezoelectric element 30 is formed on the entire surface over a region facing the piezoelectric layer 33 and the elastic plate 31 on the mirror element 20A. On the other hand, the lower electrode film 32 is present in the piezoelectric layer 33 except for the wiring lead portion, and the part other than the piezoelectric element 30 of the mirror element 20A is formed by only the elastic plate 31 and the upper electrode film 34. The curvature change of the mirror element 20A is increased. Further, the end face of the lower electrode film 32 is covered with the piezoelectric layer 33 to prevent a short circuit between the lower electrode film 32 and the upper electrode film 34. Other structures are the same as those in the first embodiment.
[0069]
In such a configuration, the entire mirror element 20A is covered with the upper electrode film 34 that also serves as a reflection film, so that the reflectance of light can be improved and the reliability can be improved.
[0070]
In the above-described configuration, the upper electrode film 34 is provided after the piezoelectric layer 33 is patterned and baked, and therefore, the upper electrode film 34 can be used even if it is a material that is vulnerable to high temperatures. That is, as the upper electrode film 34, a material having relatively low rigidity such as aluminum (Al) can be used. Therefore, by providing the upper electrode film 34 on the entire surface of the mirror element, for example, a lower electrode made of platinum is used. The rigidity of the mirror element can be reduced and the change in curvature can be increased as compared with the case where the film 32 is provided on the entire surface.
[0071]
Furthermore, in this embodiment, since the end surface of the lower electrode film 32 is covered with the piezoelectric layer 33, even if the upper electrode film 34 is provided on the entire surface of the mirror element, a short circuit may occur between the lower electrode film 32 and the lower electrode film 32. Absent.
[0072]
(Embodiment 3)
FIG. 8 is a top view illustrating a main part of the light modulation device according to the third embodiment.
[0073]
As shown in FIG. 8, the present embodiment is the same as the first embodiment except that the surface of the mirror element 20B is substantially elliptical.
[0074]
That is, the mirror element 20B has a substantially elliptical shape, and the piezoelectric element 30 is provided only on the outer edge portion thereof. In this embodiment, the mirror element 20B is supported on the mirror substrate 11 by the support portions 20a and 20b at the outer edge portion of the portion having the shortest length in the surface direction.
[0075]
Here, when the mirror element 20B has a surface shape with a different length in the surface direction such as an elliptical shape as in the present embodiment, the length a between the support portions is substantially orthogonal to the direction between the support portions. It is preferable to provide the support portion at a position that is shorter than the length b in the direction of the movement.
[0076]
With such a configuration, the deformation amount of the mirror element 20 by driving the piezoelectric element 30 can be further improved. Of course, the same effects as those of the first embodiment can also be obtained.
[0077]
(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.
[0078]
For example, in the above-described embodiment, the piezoelectric element 30 is formed only on the outer edge portion of the mirror element. However, the present invention is not limited to this, and may of course be provided on the entire surface of the mirror element 20.
[0079]
Further, for example, in Embodiment 1 described above, the region other than the piezoelectric body active portion 30a of the mirror element 20 is configured by the elastic plate 31 and the lower electrode film 32, but is not limited thereto, for example, the elastic plate 31 may be removed and only the lower electrode film 32 may be used. In any case, the amount of deformation can be further increased by reducing the thickness of the region other than the piezoelectric active portion 30a of the mirror element 20 as much as possible.
[0080]
Further, for example, in the above-described embodiment, the recesses 12 are provided in the regions corresponding to the mirror elements of the mirror elements, and the mirror elements 20 are formed in the regions facing the recesses 12 using the sacrificial layer 60. Although the mirror element 20 is supported at two points, the present invention is not limited to this. For example, after forming each mirror element 20 on the mirror substrate 11, the mirror substrate 11 is etched from the opposite side of the mirror element 20 by etching or the like. It may be removed and each mirror element 20 may be supported at two points.
[0081]
The light modulation device of the present invention having each configuration described above is used as a part of a display device, for example.
[0082]
9 and 10 show an example of a display device using the light modulation device of the present invention. 9 and 10 are schematic cross-sectional views of the optical system constituting the display device, and the lens, the light modulation device, and the like are greatly simplified.
[0083]
The display device shown in FIG. 9 includes a metal halide lamp 210 that is a light source, 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.
[0084]
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.
[0085]
Of the mirror elements 20 constituting the light modulation device 10, the mirror element 20 that is driven and deformed via the drive element 50 functions as a concave mirror, and light incident on the deformed mirror element 20 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 20 is reflected and imaged on the screen 240 which is an image plane by the projection lens 230.
[0086]
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.
[0087]
As the screen 240, a reflective screen or a transmissive screen can be used.
[0088]
In the optical system shown in FIG. 9, only about half of the light emitted from the light source 210 illuminates the light modulation device 10 with 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.
[0089]
In the display device shown in FIG. 10, by using three polarization beam splitters 221, 222, and 224 instead of the half mirror 220, the energy radiated from the light source is guided to the screen 240 in principle without loss. .
[0090]
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.
[0091]
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.
[0092]
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.
[0093]
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.
[0094]
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.
[0095]
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.
[0096]
【The invention's effect】
As described above, in the present invention, the mirror element is supported on the substrate by the two support portions of the outer edge portion facing each other along the in-plane direction with the center thereof interposed therebetween, so that the other part of the outer edge portion. Is a free end, and the amount of deformation by driving the piezoelectric element can be improved. Also, by providing the piezoelectric element only at the outer edge of the mirror element, the deformation direction of the piezoelectric active part of the mirror element is opposite to the deformation direction of the other part, so that a larger curvature change occurs. As a result, the light collecting performance can be improved. Furthermore, since the piezoelectric element of each mirror element only needs to be relatively small, there is an effect that power consumption can be suppressed.
[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 main parts 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 showing a deformed state of the light modulation device according to the first embodiment of the invention.
FIG. 6 is a schematic cross-sectional view of an optical system of the light modulation device according to the first embodiment of the invention.
FIGS. 7A and 7B are a top view and a cross-sectional view of main parts of a light modulation device according to a second embodiment of the invention. FIGS.
FIG. 8 is a top view showing a main part of an optical modulation device according to a third embodiment of the present invention.
FIG. 9 is a schematic cross-sectional view of an optical system constituting a display device using the light modulation device according to the present invention.
FIG. 10 is a schematic sectional view of an optical system constituting a display device using the light modulation device according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Light modulation device 11 Mirror board | substrate 12 Recessed part 20,20A, 20B Mirror element 20a, 20b Support part 30 Piezoelectric element 30a Piezoelectric active part 31 Elastic plate 32 Lower electrode film 33 Piezoelectric layer 34 Upper electrode film

Claims (3)

A mirror element having a piezoelectric element composed of a piezoelectric layer and a pair of lower and upper electrodes sandwiching the piezoelectric element and having a mirror film structure for reflecting light, and a drive element provided corresponding to the mirror element Having a light modulation device,
The mirror element is supported on the substrate by two support portions of outer edge portions facing each other in the in-plane direction across the center of the mirror element, and the piezoelectric element constituting the mirror element is the mirror element It is provided only in the outer edge part of the light modulation device characterized by the above-mentioned.   The light modulation device according to claim 1, wherein a length between the support portions of the mirror element is shorter than a length in a direction substantially perpendicular to a direction between the support portions.   The light modulation device according to claim 1, a light source, light from the light source is incident on the light modulation device, and the piezoelectric element of the light modulation device is driven or not driven And an optical system that emits only one of the reflected light.

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