JP2007147833A - Optical switching element and image display apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical switching element that materializes fast switching operation, a large light intensity ratio, and a clear projection pattern. <P>SOLUTION: In the optical switching element 1, there are arranged in the order as stated a transmitting-end optical surface 12 with a fixed position, a displacing optical surface 13 displaceable by a displacing means, and an incident-end optical surface 14 with a fixed position. There are also formed an optical path A between the transmitting-end optical surface 12 and the displacing optical surface 13 and an optical path B between the displacing optical surface 13 and the incident-end optical surface 14. By displacing the displacing optical surface 13 with the displacing means, the length of the optical paths A, B is increased/decreased through a reciprocal relation, varying interference of light of the optical paths A, B. Thus, the optical switching element 1 varies the light intensity of the transmitting light from the transmitting-end optical surface 12 against the incident light with which the incident-end optical surface 14 is irradiated, or the light intensity of the reflected light from the incident-end optical surface 14. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical switching element that changes the light intensity of transmitted light or reflected light with respect to incident light by using the interference action of light, and an image display device using the optical switching element.

  In recent years, image display devices such as liquid crystal display devices, plasma display devices, and organic EL (Electroluminescence) display devices are becoming thinner. These thinned image display devices control color development or luminance in units of pixels by individually performing switching operations (ON-OFF operations) of elements constituting the units of pixels. Therefore, a switching element capable of high-speed switching operation is required for moving image reproduction. In addition, since an enormous number of switching elements are used, each optical switching element is desired to have a low operating voltage (for example, 10 V or less) for the purpose of reducing the power consumption of the entire apparatus.

  As a switching element that achieves both high-speed switching operation and low operating voltage, an optical switching element using MEMS (Micro Electro Mechanical Systems) technology is promising. For example, Patent Document 1 discloses a switching element using such micromachine technology and an image display element using the optical switching element. FIG. 14 shows a cross-sectional view of a transmissive optical switching element disclosed in Patent Document 1. In FIG.

  In the optical switching element 91 disclosed in Patent Document 1, a transmission-side optical surface 912 having conductivity is formed on the upper surface of a substrate 911 that is transparent to incident light. The displacement optical surface 913 has conductivity and is formed with a predetermined optical path length from the transmission side optical surface 912. Here, the “light path” means a path through which light passes in the orthogonal direction connecting the optical surfaces arranged in parallel at the shortest (hereinafter the same). The displacement optical surface 913 is displaced by an electrostatic force generated by an electrical signal applied using the transmission optical surface 912 and the displacement optical surface 913 as electrodes, and the length of the optical path between the transmission optical surface 912 and the displacement optical surface 913 is increased. Increase or decrease.

  The length of the optical path between the transmission side optical surface 912 and the displacement optical surface 913 is the sum of the thicknesses of the transmission side stopper transmission surface 9121, the transmission side gap 9123, and the incident side gap 9143 interposed therebetween. Here, the transmission-side stopper transmission surface 9121 is made of a film that is transparent to incident light, has a high refractive index, and has a high dielectric constant, and is integrally formed on the upper surface of the transmission-side optical surface 912 that is fixed in position. The transmission side gap 9123 is set by a transmission side spacer surface 9122 formed integrally with the upper surface of the transmission side stopper transmission surface 9121. The incident side gap 9143 is set by the incident side spacer surface 9142. This optical switching element 91 not only can accurately set the length of the optical path between the transmission side optical surface 912 and the displacement optical surface 913 by the transmission side stopper transmission surface 9121, the transmission side gap 9123, and the incident side gap 9143. By restricting the amount of displacement of the displacement optical surface 913 to the range of the transmission side gap 9123 and the incident side gap 9143, the increase and decrease of the length of the optical path is accurately regulated, and the change of the interference action of light is switched accurately. be able to.

  This transmission type optical switching element 91 limits the amount of displacement by the transmission side stopper transmission surface 9121 so that the displacement optical surface 913 is not displaced beyond the elastic deformation limit due to electrostatic force, thereby improving the reliability. Yes. In addition, the displacement optical surface 913 that is displaced by electrostatic force is extremely narrow so that it does not rebound greatly when returning to the substantially flat original state from the close contact state with the transmission side stopper transmission surface 9121 shown in FIG. Since it can be brought into contact with the incident-side stopper transmitting surface 9141 formed with the incident-side gap 9143 therebetween and returned to the original stable state in a short time, an extremely high-speed switching operation is possible.

  In order to prevent the projection pattern from becoming unclear, as shown in FIG. 14, a light shielding surface 919 that blocks incident light is formed on the upper surface of the incident side stopper transmitting surface 9141, and the light shielding surface 919 is displaced. When the optical surface 913 is displaced, a narrow transmission window 9192 that is smaller than the range in contact with the transmission side stopper transmission surface 9141 is opened, and the range through which incident light is transmitted is limited to the range in which the maximum light intensity ITmax can be obtained. Yes. In other words, the light shielding surface 919 having the transmission window 9192 opened restricts the light intensity distribution of the obtained transmitted light to the width of ITmax indicated by the alternate long and short dash line in the lower part of FIG. 14, and sharpens the outline of the transmitted light.

The optical switching element 91 shown in FIG. 14 utilizes the light interference action by the pair of transmission side optical surface 912 and the displacement optical surface 913, that is, the light interference action seen in the so-called “Fabry-Perot interference filter”. However, the maximum light intensity ITmax in a state where the displacement optical surface 913 of the transmitted light with respect to the incident light intensity I ₀ shown in FIG. 14 is in close contact with the transmission side stopper transmission surface 9121 (hereinafter referred to as the ON state of the optical switching element 91), The ratio of the displacement optical surface 913 in close contact with the incident side stopper transmission surface 9141 (hereinafter referred to as the OFF state of the optical switching element 91) to the minimum light intensity ITmin, that is, the ITmax / ITmin ratio (hereinafter referred to as the light intensity ratio). ) May not be large enough.

  In order to increase the light intensity ratio, Non-Patent Document 1 proposes a double-cavity method in which optical surfaces 923, 925, and 927 are arranged in three stages and the interference action of light is doubled as shown in FIG. . In the optical switching element 92 disclosed in Non-Patent Document 1, a lower spacer surface 922, an intermediate spacer surface 924, and an upper spacer surface 926 are interposed on the upper surface of a substrate 921, and a lower gap 9221, an intermediate gap 9241, and an upper gap 9261, respectively. Separated lower displacement optical surface 923, middle optical surface 925, and upper displacement optical surface 927 are formed. In this optical switching element 92, when a DC voltage V is applied to the middle optical surface 925 from the lower displacement optical surface 923 and the upper displacement optical surface 927, the lower displacement optical surface 923 and the upper displacement optical surface 927 become the middle optical surface 925. The intermediate gap 9241 and the upper gap 9261 are eliminated in close contact with each other, and the lower gap 9221 is conversely enlarged to change the light intensity of the transmitted light due to the light interference action. The light interference action occurs twice in the light path between the lower-stage displacement optical surface 923 and the middle-stage optical surface 925 and the light path between the middle-stage optical surface 925 and the upper-stage displacement optical surface 927, as if two optical switching elements were used. The light intensity ratio can be increased as if they were arranged in series.

  However, in the optical switching element 92 disclosed in Non-Patent Document 1, the lower displacement optical surface 923 and the upper displacement optical surface 927 that are displaced are in a cantilever shape, and the lower displacement optical surface 923 and the upper displacement optical surface 927 are middle optical. When the DC voltage V is stopped after being displaced so that it is in close contact with the surface 925, the lower displacement optical surface 923 and the upper displacement optical surface 927 are displaced to the opposite side beyond the original position, and are correctly restored. There is a risk of causing a vibration phenomenon (rebound phenomenon) that repeats reciprocating motion until the position returns to the position. Since this rebound phenomenon is more likely to occur as the switching operation becomes faster, speeding up of the switching operation is limited.

JP-A-2005-157133 W. Janto et al., "Design and fabrication of double-cavity tunable filter using micromachined structure," Japanese Journal of Applied Physics, vol. 42, no.7B, pp. L828-L830, July 2003.

  The optical switching element of Patent Document 1 (see FIG. 14) cannot obtain a high light intensity ratio, and when used as a switching element of an image display device, only an unclear image with a low contrast ratio may be formed. In order to obtain a clear image with a high contrast ratio, a light intensity ratio of 100: 1 or more, preferably about 1000: 1 is desired for the optical switching element constituting the pixel unit. Further, the optical switching element of Non-Patent Document 1 (see FIG. 15) can obtain a large light intensity ratio, but a high-speed switching operation cannot be expected due to the rebound phenomenon.

  A thin image display device that reproduces a clear moving image requires an optical switching element that can perform a high-speed switching operation and has a large light intensity ratio. Furthermore, an optical switching element that does not blur the projection pattern of transmitted light or reflected light on the display surface is required. Therefore, in optical switching elements using MEMS technology, the amount of displacement of the displacing optical surface is controlled to suppress or prevent the rebound phenomenon to realize high-speed switching operation, and more than two optical surfaces are doubled. A large light intensity ratio is achieved by obtaining the above-described light interference effect, and furthermore, a light projection pattern with a clear outline of transmitted light or reflected light is obtained, that is, a displacing optical surface is in contact with and set in advance. An optical switching element capable of obtaining a light projection pattern of transmitted light or reflected light only within a range where the maximum possible light intensity ratio can be obtained was studied.

  What has been developed as a result of the study is that a transmission-side optical surface that is fixed in position, a displacement optical surface that is displaced by a displacement means, and an incident-side optical surface that is fixed in position are arranged in the order described above. An optical path A between the optical surfaces and an optical path B between the displacement optical surface and the incident-side optical surface are formed. By displacing the displacement optical surface by the displacing means, the optical path A and the optical path B Increasing or decreasing the length in a reciprocal relationship to change the light interference action of the light path A and the light path B so that the transmitted light from the transmission side optical surface or the incident side optical surface with respect to the incident light irradiated on the incident side optical surface It is an optical switching element which changes the light intensity of the reflected light from. The optical switching element of the present invention is a transmission type optical switching element that inputs incident light to the incident side optical surface and outputs transmitted light from the transmission side optical surface, and incident light that is input to the incident side optical surface. And a reflective optical switching element that outputs reflected light from the side optical surface.

  Here, the “incident side optical surface” referred to in the present invention is a fixed optical surface on the side where incident light is input, and the “transmission side optical surface” is symmetrical with the incident side optical surface across the displacement optical surface. It is a fixed optical surface on the side arranged in a positional relationship. In the reflection type optical switching element, since the reflected light is output from the incident side optical surface and the transmitted light is not output from the transmission side optical surface, the incident side optical surface is “reflection side optical surface” and the transmission side optical surface is “blocked”. It can also be called a “side optical surface”. The “optical surface” in the present invention means a semi-transparent surface (including a film) that is not optically totally transmitted or totally reflected, for example, a surface having a size equal to the cross section of the optical path, or crossing the optical path. The portion corresponding to the optical path of the film having a size corresponding to this corresponds to this. Examples of such an optical surface include a single layer film such as a polycrystalline silicon film having conductivity, or a multilayer film including an insulating film such as a silicon nitride film and a conductive thin film such as gold in addition to the single layer film.

  The transmissive optical switching element irradiates the incident side optical surface with incident light, outputs the transmitted light with the maximum light intensity ITmax from the transmission side optical surface, and outputs the transmitted light with the relatively low minimum light intensity ITmin. To be switched (including the minimum light intensity ITmin = 0). From now on, in the transmission type optical switching element, the “state of transmitting the transmitted light with the maximum light intensity ITmax” is called “ON state” in relation to the switching operation and “transmission” in relation to the incident light. The state in which transmitted light with light intensity ITmin is output is referred to as “OFF state” in relation to the switching operation, and “non-transparent” in relation to incident light. In the ON state or transmission, there is no attenuation due to the interference action of light according to the length of the optical path A and the optical path B, and transmitted light depending on the attenuation of each optical surface, substrate, etc. is obtained. On the other hand, in the OFF state or non-transmission, in addition to attenuation of each optical surface and substrate, the transmitted light is attenuated by the interference action of light according to the length of the optical path A and the optical path B.

  The reflection type optical switching element irradiates the incident side optical surface with incident light and outputs the reflected light with the maximum light intensity ITmax from the incident side optical surface and the reflected light with the relatively low minimum light intensity ITmin. The state of output from the side optical surface (including minimum light intensity ITmin = 0) is switched. From now on, in the reflection type optical switching element, the “state that outputs the reflected light with the maximum light intensity ITmax” is called “ON state” in relation to the switching operation, and “reflection” in relation to the incident light, and “minimum” The “state of outputting reflected light with light intensity ITmin” is called “OFF state” in relation to the switching operation, and “non-reflecting” in relation to the incident light. In the ON state or reflection, there is no absorption due to the interference action of light according to the length of the light path A and the light path B, and reflected light depending on the attenuation of each optical surface or substrate orthogonal to the light path is obtained. On the other hand, in the OFF state or non-reflection, in addition to the attenuation of each optical surface, the substrate, etc., the reflected light is absorbed by the interference action of light according to the length of the optical path A and the optical path B.

  The optical switching element of the present invention increases or decreases the length of the optical path A between the transmission side optical surface and the displacement optical surface and the length of the optical path B between the displacement optical surface and the incident side optical surface in a reciprocal relationship. Thus, the transmitted light or the reflected light is switched between the maximum light intensity ITmax and the minimum light intensity ITmin by changing the interference action of the light in the light path A and the light path B. That is, the interference of light in the two light paths A and B is synergized, and the ratio of the maximum light intensity ITmax and the minimum light intensity ITmin, that is, the light intensity ratio is increased. Such an optical switching element of the present invention is similar to a configuration in which an optical switching element having an optical path A and an optical switching element having an optical path B are overlapped in series, but the lengths of the optical path A and the optical path B are different. It is characterized in that the displacement optical surface to be increased / decreased is shared, and the lengths of the optical path A and the optical path B increase / decrease simultaneously due to a reciprocal relationship.

  In the optical switching element of the present invention, the light intensity ratio can be further increased by adopting a configuration in which the optical path A and the optical path B are stacked in multiple stages. For example, the optical switching element in which the optical path A and the optical path B are stacked in two stages includes a position-fixed transmission side optical surface, a lower-stage displacement optical surface that is displaced by a displacement means, and a position-fixed lower-stage intermediate optical surface, An upper intermediate optical surface that is fixed in position, an upper optical surface that is displaced by a displacing means, and an incident-side optical surface that is fixed in position are arranged in the order described, and between the transmission optical surface and the lower displacement optical surface Optical path A, optical path B between the lower displacement optical surface and lower intermediate optical surface, optical path C between the upper intermediate optical surface and upper displacement optical surface, and the upper displacement optical surface And the optical path D between the incident-side optical surfaces, and by displacing one or both of the lower-stage displacement optical surface and the upper-stage displacement optical surface by the displacement means, the length of the optical path A and the optical path B The optical path A and the optical path are increased or decreased in a reciprocal relationship. And the length of the light path C and the light path D is increased or decreased in a reciprocal relationship to change the light interference action of the light path C and the light path D, so that the incident side optical surface The light intensity of the transmitted light from the transmission side optical surface or the reflected light from the incident side optical surface with respect to the incident light to be irradiated is changed. In this optical switching element, the optical path C corresponds to the optical path A (or optical path B), and the optical path D corresponds to the optical path B (or optical path A).

  In addition, the optical switching element in which the optical path A and the optical path B are stacked in two stages also serves as an optical surface interposed between the upper and lower stages, and the position-fixed transmission side optical surface and the lower displacement displaced by the displacing means. An optical surface, a fixed intermediate optical surface fixed in position, an upper displacement optical surface displaced by a displacement means, and an incident-side optical surface fixed in position are arranged in the order described, and the transmission-side optical surface and the lower optical surface An optical path A between the displacement optical surfaces; an optical path B between the lower displacement optical surface and the common intermediate optical surface; an optical path C between the common intermediate optical surface and the upper displacement optical surface; The optical path D is formed between the displacement optical surface and the incident side optical surface, and one or both of the lower displacement optical surface and the upper displacement optical surface are displaced by the displacement means. The length of the path B is increased or decreased in a reciprocal relationship, and the optical path A The light interference action of the light path B is changed, and the length of the light path C and the light path D is increased / decreased in a reciprocal relationship to change the light interference action of the light path C and the light path D. You may make it the structure which changes the light intensity of the transmitted light from the transmission side optical surface with respect to the incident light irradiated to a side optical surface, or the reflected light from an incident side optical surface. In this optical switching element, the optical path C corresponds to the optical path A (or optical path B), and the optical path D corresponds to the optical path B (or optical path A).

  Furthermore, in the optical switching element in which the optical path A and the optical path B are laminated in two stages, either the laminated optical path C or the optical path D is omitted, and the position is fixed by the transmission-side optical surface and the displacement means. A lower displacing optical surface, a common intermediate optical surface whose position is fixed, and an upper displacing optical surface that is displaced by the displacing means are arranged in the order described, and between the transmission side optical surface and the lower displacing optical surface. An optical path A, an optical path B between the lower displacement optical surface and the common intermediate optical surface, and an optical path C between the common intermediate optical surface and the upper displacement optical surface are formed. By displacing one or both of the lower displacing optical surface and the upper displacing optical surface, the length of the optical path A and the optical path B is increased or decreased in a reciprocal relationship, and the light of the optical path A and the optical path B is Change the interference action and increase or decrease the length of the light path C By changing the interference action of the light in the optical path C, the light intensity of the transmitted light from the transmission side optical surface or the reflected light from the upper displacement optical surface with respect to the incident light irradiated on the upper displacement optical surface is changed. May be. In this optical switching element, the optical path C corresponds to the optical path A (or optical path B).

  The displacement optical surface in each optical switching element is not limited as long as it can be displaced to increase or decrease the length of the optical path A or the like. Here, “displacement” of the displacement optical surface refers to a movement in which the entire displacement optical surface moves in parallel and approaches or separates from the incident side optical surface or the transmission side optical surface without deformation of the displacement optical surface. It means that the surface itself is deformed and the deformed part approaches or separates from the incident side optical surface or the transmission side optical surface. It is difficult for a physical displacement means to cause such a movement displacement to be a minute displacement optical surface, and an electromagnetic displacement means is preferable. From this, the displacement optical surface is displaced by an electrostatic force applied to the displacement optical surface by an electric field generated in response to an externally applied electric signal, or an electric field generated in response to an externally applied electric signal. It is preferable that the auxiliary displacement surface is displaced integrally by an electrostatic force applied to the auxiliary displacement surface formed integrally with the optical surface. When the displacement optical surface is displaced by electrostatic force, a reinforcing auxiliary displacement surface may be formed integrally with the displacement optical surface. When the auxiliary displacement surface is displaced by electrostatic force, the displacement optical surface may be displaced by electrostatic force. Each electric signal is applied by using a transmission-side optical surface, a displacement optical surface, and an incident-side optical surface as electrodes, or by separately attaching electrodes to the transmission-side optical surface, the displacement optical surface, or the incident-side optical surface. The auxiliary displacement surface can be an electrode separately provided on the displacement optical surface. Further, a separate electrode may be disposed on the optical path including the transmission side optical surface, the displacement optical surface, and the incident side optical surface, and an electric signal may be applied to the electrode. In any case, if an electrostatic force acts on the displacement optical surface to be deformed, the configuration or position of the electrode can be freely set.

  In addition, the optical switching element of the present invention is provided with a displacement limiting stopper for limiting the displacement amount of the displacement optical surface to the displacement optical surface to limit the displacement amount of the displacement optical surface, thereby speeding up the switching operation. This prevents the rebound phenomenon of the displacement optical surface. For example, in a transmissive optical switching element, the lengths of the optical path A and the optical path B are [(λ / 2) × n + λ / 4] (λ is the wavelength of incident light, n is an integer, and the same applies hereinafter). If it is configured to transmit light when the length of each optical path is increased or decreased by λ / 4 due to the displacement of the displacement optical surface, the required amount of displacement of the displacement optical surface is λ / 4. The present invention limits the actual displacement amount of the displacement optical surface to the necessary displacement amount by the displacement limit stopper while making the displaceable range of the displacement optical surface more than the necessary displacement amount. This means that the displacing optical surface that is being displaced at high speed is forcibly stopped. In addition to speeding up the switching operation of the optical switching element, the displacing optical surface that is stopped by the displacement limiting stopper is used. Suppress or prevent the rebound phenomenon from occurring.

  As described above, the displacement limiting stopper of the present invention may have any configuration as long as the displacement amount of the displacement optical surface can be limited. However, the stopper is arranged in parallel with the displacement optical surface, and the stopper transmissive surface on which the displaced displacement optical surface is in contact is provided. It is preferable to configure as a surface. Like the displacement optical surface, the stopper transmission surface is disposed in parallel with the displacement optical surface so that the optical path is orthogonal to the displacement optical surface at the return position (initial position) or the displacement position (position displaced by λ / 4). The actual displacement is limited by contacting the surface. Thus, the displacement means only needs to displace the displacement optical surface so as to press against the stopper transmission surface, so that the displacement speed of the displacement optical surface can be increased and the switching operation can be speeded up. Further, since the displacement optical surface is in contact with the stopper transmission surface at the position where the displacement amount is limited, the light intensity of the transmitted light or the reflected light in the contacted range can be made uniform.

  A more specific stopper transmission surface is provided on the same side as the displacement direction of the displacement optical surface that is displaced in the direction of reducing the length of the optical path A, and is in contact with the displacement optical surface when the displacement optical surface is displaced. The transmission side stopper is provided on the same side as the displacement optical surface to be displaced in the direction of reducing the length of the optical path B and the displacement optical surface is in contact with the displacement optical surface when the displacement optical surface is restored. An incident side stopper transmission surface can be exemplified. The transmission side stopper transmission surface is a stopper transmission surface provided with respect to the displacement position (position displaced by λ / 4) of the displacement optical surface, and the incident side stopper transmission surface is at the return position (initial position) of the displacement optical surface. It is a stopper transmission surface provided for the surface.

  The transmission side stopper transmission surface and the incidence side stopper transmission surface can be used individually, but it is preferable to use both at the same time. In this case, an electrical signal having a voltage of different polarity is applied to the transmission side optical surface and the displacement optical surface to generate an electrostatic force that attracts the transmission side optical surface and the displacement optical surface, and the displacement optical surface is disposed in the displacement direction. Electrostatic force that causes the transmission side optical surface and the displacement optical surface to repel each other by applying an electric signal having the same polarity voltage to the transmission side optical surface and the displacement optical surface. Is generated and pressed against the transmission surface of the incident side stopper to recover. In this way, when the displacement optical surface is pressed against the transmission side stopper transmission surface or the incident side stopper transmission surface at any time of displacement or return, for example, switching operation from OFF state to ON state due to displacement of the displacement optical surface, The switching operation from the ON state to the OFF state can be speeded up, and the rebound phenomenon when the displacement optical surface is restored can be suppressed or prevented.

  Furthermore, the light switching element of the present invention has a clear light projection by arranging a light-shielding surface having a transmission window below the range where the displaced displacement optical surface is in contact with the stopper transmission surface, in parallel with the displacement optical surface. Realize the pattern. Here, the “light-shielding surface” means a surface that totally reflects or absorbs incident light and does not transmit incident light. In the optical switching element of the present invention, the transmitted light or reflected light as designed is obtained in the range where the displacing optical surface to contact the stopper transmitting surface, but the designed transmitted light or reflected light is not necessarily outside the range. There is no guarantee obtained. The light-shielding surface limits the range in which transmitted light or reflected light is obtained to the range of the transmission window below the range where the displaced displacement optical surface is in contact with the stopper transmission surface, so that the transmitted light or reflected light as designed can be obtained. Thus, the outline of the transmitted light or reflected light is sharpened.

  Specific light-shielding surfaces include a transmission-side light-shielding surface attached to the upper or lower surface of the transmission-side optical surface, a displacement-side light-shielding surface attached to the upper or lower surface of the displacement optical surface, and an upper surface or lower surface of the incident-side optical surface. Examples thereof include an incident-side light-shielding surface, a stopper-side light-shielding surface attached to the upper or lower surface of the stopper transmission surface, and a substrate-side light-shielding surface attached to the upper or lower surface of the substrate on which the optical switching element is formed. Each light shielding surface is a transmission side optical surface, a displacement optical surface, an incident side optical surface, a stopper transmission surface or an upper surface or a lower surface of the substrate, and the transmission side optical surface, the displacement optical surface, the incident side optical surface, the stopper transmission surface or the substrate. It is preferable to form it integrally. Here, since it is difficult to integrally form the displacement-side light shielding surface on the displacing displacement optical surface, for example, the light shielding surface attached to the displacing displacement optical surface is disposed close to the displacing displacement optical surface. Including the case of

  By using the optical switching element of the present invention, an image display device having high contrast, high responsiveness, high resolution and low power consumption can be configured. That is, the image display device of the present invention has a one-dimensional array or a two-dimensional array of pixel units composed of optical switching elements that change the light intensity of transmitted light or reflected light with respect to incident light from a light source. In the image display device that displays an image on the display surface by turning on or off, the optical switching element includes a transmission-side optical surface whose position is fixed, a displacement optical surface that is displaced by a displacement unit, and a light-incident-side optical surface that is fixed in position. The optical path A between the transmission optical surface and the displacement optical surface and the optical path B between the displacement optical surface and the incident optical surface are formed in order, and the displacement optical surface is displaced by the displacement means. Thus, the length of the light path A and the light path B is increased or decreased in a reciprocal relationship to change the light interference action of the light path A and the light path B, thereby transmitting the incident light irradiated on the incident side optical surface. From the side optical surface A configuration for changing the light intensity of the reflected light from the over light or incident-side optical surface.

  The optical switching element can increase the light intensity ratio of the transmitted light or the reflected light with respect to the incident light by utilizing the interference action of the light that is greatly changed by simultaneously increasing or decreasing the length of the optical path A and the length of the optical path B. Since the light intensity ratio is directly reflected in the contrast ratio on the display surface, the image display device of the present invention can increase the contrast ratio on the display surface. The optical switching element can speed up the switching operation by attaching a displacement limiting stopper for limiting the amount of displacement of the displacement optical surface to the displacement optical surface. As a result, the image display device of the present invention can increase the response speed of each pixel unit, and can display a moving image with high response in a responsive manner. The displacement limiting stopper is preferably a stopper transmission surface that is arranged in parallel with the displacement optical surface and is in contact with the displaced displacement optical surface.

  The optical switching element includes a light shielding surface having a transmission window that is equal to or smaller than a range in which the displaced optical surface is in contact with the stopper transmission surface, and is arranged in parallel with the optical displacement surface, so that the contour of transmitted light or reflected light is obtained. Can be clarified. Thereby, the image display apparatus can clarify each pixel unit, and can raise the resolution of the image displayed on a display surface. Furthermore, the optical switching element displaces the displacement optical surface using an electrostatic force applied to the displacement optical surface by an electric field generated according to an electric signal applied from the outside, or responds to an electric signal applied from the outside. Electric power used to drive the displacement means by displacing the displacement optical surface integrally with the auxiliary displacement surface using the electrostatic force applied to the auxiliary displacement surface formed integrally with the displacement optical surface by the electric field generated by Can be suppressed. As a result, the power consumption required for the pixel unit and thus the entire display surface is suppressed, and low power consumption can be realized as an image display device.

  Here, the optical switching element of the present invention can continuously adjust the light intensity of the transmitted light or the reflected light according to the increase / decrease amount of the length of the optical path A and the optical path B. From this, for example, it is conceivable to adjust the color development and the light intensity of each pixel composed of the optical switching element by continuously increasing / decreasing the displacement amount of the displacing optical surface without using the displacement limiting stopper. However, it is difficult to adjust the light intensity by increasing or decreasing the displacement amount of the displacement optical surface, and it is not possible to benefit from a high-speed switching operation using the displacement limit stopper. Therefore, for example, by providing a displacement limit stopper, the amount of displacement of the displacement optical surface is regulated to be constant, and the time during which each optical switching element transmits or reflects incident light, that is, the ON state time is increased or decreased. It was decided to adjust the color development and light intensity for each pixel.

First, the image display device of the present invention uses the electrostatic force applied to the displacement optical surface by an electric field generated according to an externally applied electric signal as a displacement means of the displacement optical surface of the optical switching element, and unit lighting in units of pixels. Adjusting the color development and light intensity of this pixel unit by increasing or decreasing the number of times of application of the electrical signal applied in the unit application time divided in time so that the total of the unit application time does not exceed the unit lighting time; did. In this case, the color development for each pixel is determined by the number of times of applying the electric signal to each optical switching element, and the light intensity for each pixel is proportional to the number of times of applying the electric signal to each light switching element. Here, the “unit lighting time” is a lighting time for each scanning line when the display surface lights a plurality of scanning lines in the scanning order to display an image. For example, if the display surface that displays an image at 30 fps consists of 525 scanning lines per frame (current analog TV broadcasts, etc.), the unit lighting time is (1/30) /525≒6.35×10 ^-5 seconds It becomes. Since the unit application time is a time obtained by dividing the unit lighting time, for example, when the unit lighting time (6.35 × 10 ⁻⁵ seconds) is divided into 100, the unit application time is 6.35 × 10 ⁻⁷ seconds, and the number of application times Theoretically, the light intensity can be adjusted in 100 gradations by increasing or decreasing from 0 to 100 times.

Further, the image display device of the present invention uses the electrostatic force applied to the displacement optical surface by the electric field generated according to the electric signal applied from the outside as the displacement means of the displacement optical surface of the optical switching element, and unit lighting in units of pixels. It is also possible to adjust the color development and light intensity of the pixel unit by applying an electrical signal with a continuous application time of less than or equal to the time and increasing or decreasing the continuous application time of the electrical signal within a range not exceeding the unit lighting time. . In this case, the color development of each pixel is determined by the continuous application time of the electrical signal to each optical switching element, and the light intensity of each pixel is proportional to the continuous application time of the electrical signal to each optical switching element. In the above example, the continuous application time can be increased or decreased in 100 steps within a range of 0 to unit lighting time = 0 to 6.35 × 10 ⁻⁵ seconds, and the light intensity can theoretically be adjusted in 100 gradations.

  Since the optical switching element only outputs transmitted light or reflected light with respect to incident light having a specific wavelength, the following configuration is required to obtain a color image on the display surface. That is, the pixel unit is one each of a red switching element, a green switching element, and a blue switching element in which different lengths of light paths A and B are set corresponding to red light, green light, and blue light. A total of three units are configured as one set, and three wavelengths of visible light corresponding to red light, green light, and blue light are input as incident light from the light source to the pixel unit, and from each optical switching element that configures the pixel unit An image is displayed on the display surface by transmitted light or reflected light, and each pixel unit is displayed on the display surface by individually changing the light intensity of the transmitted light or reflected light of each light switching element constituting each pixel unit. To display in color. In this case, the light source is preferably a visible light emitting diode or a laser diode (hereinafter referred to as a visible light diode) in consideration of thinning and low power consumption of the image display device.

  The number of visible light diodes as the light source is not limited, but it is difficult to input incident light with sufficient light intensity to all the optical switching elements of all the pixels with a single or a relatively small number of visible light diodes. . However, for example, the display surface is configured to display an image by lighting a plurality of scanning lines in the scanning order, the pixel units arranged along the scanning lines are set as scanning units, and only the scanning units that are lit in the scanning order are incident light from the light source. If the incident light is not input from the light source to the remaining scanning units that are not in the scanning order, it is only necessary to input the incident light to the pixel units constituting the scanning unit to be lit. The number can be reduced. Further, a visible light diode equal to the number of scanning lines may be assigned for each scanning unit, and each visible light diode may be turned on or off in the scanning order. In this case, since there is only one visible light diode corresponding to the scanning order, power consumption as the image display device can be reduced.

  As another configuration for realizing color display, the pixel unit is configured as a set of at least three switching elements for ultraviolet light in which the lengths of the optical path A and the optical path B corresponding to the ultraviolet light are set, and from the light source A single-wavelength ultraviolet light is input to the pixel unit as incident light, and receives a transmitted light or a reflected light from each optical switching element constituting the pixel unit to emit light. An image is displayed on a display surface provided with a fluorescent screen corresponding to each light switching element of each pixel unit, and the light intensity of transmitted light or reflected light of each light switching element constituting each pixel unit is individually changed. By doing so, a color display may be performed on the display surface in units of pixels. In this case, another switching element for ultraviolet light is added to each pixel to make a total of four groups, and a red fluorescent screen, a green fluorescent screen or a blue fluorescent screen is added to the display screen and a white fluorescent screen is added. May be configured.

  When the ultraviolet light switching element is used, an ultraviolet light emitting diode or laser diode may be used as the light source (hereinafter represented by an ultraviolet light diode). In the case where this ultraviolet light diode is used as a light source, as in the above-described use form of the visible light diode, the display surface displays a picture by lighting a plurality of scanning lines in the order of scanning, and pixel units arranged along the scanning lines. Is configured so that incident light is input from the light source only to the scanning units that are lit according to the scanning order, and incident light from the light source is not input to the remaining scanning units that are not in the scanning order. Further, by assigning an ultraviolet light diode equal to the number of scanning lines for each scanning unit and switching on / off of each ultraviolet light diode in the scanning order, only one ultraviolet light diode that is turned on corresponds to the scanning order. By doing so, the power consumption as an image display apparatus can also be reduced.

  The optical switching element of the present invention simultaneously increases or decreases the optical path A and the optical path B in a reciprocal relationship by the displacement optical surface, and operates as if two optical switching elements are arranged in series. The important point is that the optical path A and the optical path B increase / decrease synchronously and interlock with the switching operation. Thereby, the interference action of the light of each of the light path A and the light path B can be made synergistic, and the light intensity ratio of the transmitted light or the reflected light to the incident light can be increased. Thus, the image display apparatus using the optical switching element of the present invention can display an image with clear contrast.

  Further, the optical switching element of the present invention has an effect of speeding up the switching operation of the optical switching element by limiting the amount of displacement of the displacement optical surface by the displacement limiting stopper. In particular, if the stopper transmitting surface that contacts the displacing optical surface is a displacement limiting stopper, the displacement of the displacing optical surface can be controlled in both the displacement direction and the return direction, and the switching operation can be further speeded up. . Thus, the image display device using the optical switching element of the present invention has an excellent response speed and enables the display of a moving image with intense movement.

  Furthermore, the optical switching element of the present invention can sharpen the outline of transmitted light or reflected light by the light shielding surface having the transmission window. Here, since this light shielding surface can be used in combination with the stopper transmission surface, the image display device of the present invention can obtain a light projection pattern with a clear outline. And since the optical switching element of this invention can utilize the electrostatic force by the electric field which an electric signal generate | occur | produces as a displacement means of a displacement optical surface, the electric power used is suppressed. Thus, the image display device of the present invention can obtain a high-resolution image with low power consumption.

  As described above, the image display device of the present invention can provide the effects of high contrast, high response, high resolution, and low power consumption based on the effects of the optical switching element of the present invention. In addition to this, it is possible to easily and finely adjust the color development and the light intensity of the pixel unit by adjusting the number of times or the application time of the electric signal applied to the optical switching element constituting the pixel unit. This is an effect peculiar to the image display apparatus of the present invention using the high-speed switching operation of the optical switching element of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1a and 1b are sectional views showing a transmissive optical switching element 1 according to the present invention. The optical switching element 1 of this example has the basic configuration of the present invention, and includes an optical path A between the transmission side optical surface 12 and the displacement optical surface 13 and an optical path B between the displacement optical surface 13 and the incident side optical surface 14. And have. The transmission side optical surface 12 is made of a polycrystalline silicon film, a gold film, an ITO film, etc., which is conductive and a semi-transmission film, and is formed on the upper surface of the substrate 11 made of quartz glass transparent to incident light. ing. The displacement optical surface 13 is made of a conductive polycrystalline silicon film, a gold film, an ITO film, or the like, and is formed with a distance of the optical path A from the transmission side optical surface 12. The incident-side optical surface 14 is made of a conductive polycrystalline silicon film, a gold film, an ITO film, or the like, and is formed with a distance of the optical path B from the displacement optical surface 13.

  The displacement optical surface 13 is directed toward the transmission side optical surface 12 or the incident side optical surface 14 by an electrostatic force generated by an electric signal applied using the transmission side optical surface 12, the displacement optical surface 13, and the incident side optical surface 14 as electrodes. The length of the optical path A between the transmission side optical surface 12 and the displacement optical surface 13 and the length of the optical path B between the displacement optical surface 13 and the incident side optical surface 14 are simultaneously increased or decreased due to a reciprocal relationship. Specifically, if the length of the optical path A between the transmission side optical surface 12 and the displacement optical surface 13 increases, the length of the optical path B between the displacement optical surface 13 and the incident side optical surface 14 decreases, Conversely, if the length of the optical path A between the transmission side optical surface 12 and the displacement optical surface 13 decreases, the length of the optical path B between the displacement optical surface 13 and the incident side optical surface 14 increases.

  The length of the optical path A between the transmission side optical surface 12 and the displacement optical surface 13 is the thickness of the transmission side stopper transmission surface 121 and the transmission side gap 123 if the thickness of the transmission side optical surface 12 and the displacement optical surface 13 is ignored. Is the sum of The transmission-side stopper transmission surface 121 is made of a silicon nitride film or the like that is transparent to incident light, has a high refractive index, and has a high dielectric constant, and is integrally formed on the upper surface of the transmission-side optical surface 12 that is fixed in position. The film thickness can be set accurately. The transmission side gap 123 can be accurately set by the transmission side spacer surface 122 made of a phosphor glass film or the like integrally formed on the upper surface of the transmission side stopper transmission surface 121. The transmission side gap 123 is formed by selectively etching the transmission side spacer surface 122.

  If the thickness of the displacement optical surface 13 and the incident side optical surface 14 is ignored, the length of the optical path B of the displacement optical surface 13 and the incident side optical surface 14 is equal to the thickness of the incident side stopper transmission surface 141 and the incident side gap 143. Total. Here, the incident-side stopper transmitting surface 141 is formed of a silicon nitride film or the like that is transparent to incident light, has a high refractive index, and has a high dielectric constant, and is continuously deposited on the upper surface of the incident-side spacer surface 142. The thickness can be set accurately. Further, the incident-side gap 143 can be accurately set by the incident-side spacer surface 142 made of a phosphor glass film or the like integrally formed on the upper surface of the displacement optical surface 13. From this, the thickness of the incident side gap 143 is equal to the thickness of the incident side spacer surface 142. The incident side gap 143 is formed by selectively etching the incident side spacer surface 142.

  As described above, the optical switching element 1 of the present invention includes the transmission side stopper transmission surface 121, the transmission side gap 123 (or transmission side spacer surface 122), the incident side gap 143 (or incident side spacer surface 142), and the incident side stopper transmission. Depending on the thickness of the surface 141, not only can the length of the optical path A between the transmission side optical surface 12 and the displacement optical surface 13 and the length of the optical path B between the displacement optical surface 13 and the incident side optical surface 14 be set accurately, but also the displacement By restricting the amount of displacement of the optical surface 13 to the range of the transmission side gap 123 and the incident side gap 143, the increase and decrease of the length of the light path A and the light path B is accurately regulated, and the change of the light interference action is changed. Can be switched accurately.

  In this example, in order to make the projection pattern clear, a high-melting point metal film (W film or the like) that blocks incident light on the upper surface of the incident-side optical surface 14 via a protective surface 191 such as a silicon oxide film or a silicon nitride film. A light shielding surface 19 made of a Mo film or the like is formed. When the displacement optical surface 13 is displaced, the light shielding surface 19 opens a narrow transmission window 192 that is equal to or smaller than the range in contact with the transmission side stopper transmission surface 121, and the maximum light intensity ITmax or the minimum light intensity ITmin is obtained. The projection pattern is limited within the range. Such a light shielding surface 19 may be provided on the light path A or the light path B, and the arrangement position is not limited to the upper surface of the protective surface 191. That is, the light shielding surface 19 is, for example, the lower surface of the protective surface 191, the upper surface or the lower surface of the incident side optical surface 14, the upper surface or the lower surface of the transmission side optical surface 12, the upper surface or the lower surface of the transmission side stopper transmission surface 121, In addition to the upper surface or the lower surface, it may be provided on either the upper surface or the lower surface of the substrate 11. In addition to the refractory metal film, the light shielding surface 19 can be formed of a metal film such as Al, Au, or Cr, or a semiconductor film such as a polycrystalline silicon film.

  As shown in FIG. 1B, the optical switching element 1 of this example gives a positive (+) electric signal to the transmission side optical surface 12 having conductivity, and a negative (−) to the displacement optical surface 13 and the incident side optical surface 14. ) To generate an electrostatic force that attracts the displacing optical surface 13 to the transmission side optical surface 12 and an electrostatic force that repels the displacing optical surface 13 to the incident side optical surface 14. It is displaced toward the transmission side optical surface 12. If the displacement optical surface 13 is brought into close contact with the transmission side stopper transmission surface 121, the length of the optical path A between the transmission side optical surface 12 and the displacement optical surface 13 is shortened, and conversely the displacement optical surface 13 and the incident side. By increasing the length of the optical path B between the optical surfaces 14, the interference action of the light can be changed, and the transmitted light having the maximum light intensity ITmax can be obtained. Here, in the present invention, since the transmission side optical surface 12, the displacement optical surface 13, and the incident side optical surface 14 have a parallel plate structure, a large electrostatic force can be generated by applying a low voltage electric signal. That is, the optical switching element 1 of this example can be switched at a low voltage and has low power consumption.

  In the optical switching element 1 of this example, the displacement amount is limited by the transmission side stopper transmission surface 121 so that the displacement optical surface 13 is not displaced beyond the elastic deformation limit due to electrostatic force, thereby improving the reliability. Yes. Further, the displacement optical surface 13 that is displaced by electrostatic force is narrow on the incident side so that it does not rebound greatly when returning from the state of close contact with the transmission side stopper transmission surface 121 (see FIG. 1b) to the almost flat original state. The original stable state can be achieved in a short time by bringing the surface into contact with the entrance-side stopper transmitting surface 141 formed across the gap 143 (see FIG. 1a) and forcibly stopping the displacement of the displacement optical surface 13. Can be restored.

  Here, in order to return the displacement optical surface 13 in a shorter time, conversely to the above, a positive (+) electrical signal is applied to the transmission side optical surface 12 and the displacement optical surface 13 having conductivity. A negative (-) electrical signal is applied to the surface 14 to generate an electrostatic force that repels the displacement optical surface 13 on the transmission side optical surface 12 and an electrostatic force that attracts the displacement optical surface 13 to the incident side optical surface 14 By doing so, the displacement optical surface 13 may be forcibly displaced until it is brought into close contact with the incident side stopper transmission surface 141. In this case, the displacement optical surface 13 is forcibly brought into close contact with the entrance-side stopper transmission surface 141, and naturally stabilizes without causing a rebound phenomenon, so that an extremely high speed switching operation is possible.

  2a and 2b are sectional views showing other examples of the transmission type optical switching element 2 according to the present invention. The optical switching element 2 of this example has a transmission side optical surface 22 on the substrate 21, a transmission side stopper transmission surface 221 on the transmission side optical surface 22, and a transmission side spacer surface 222 on the transmission side stopper transmission surface 221. A lower auxiliary displacement surface 231 and a displacement optical surface 23 are integrally formed on the transmission side spacer surface 222. The transmission side gap 223 is formed by the transmission side spacer surface 222. Then, the incident side spacer surface 242 is formed on the displacement optical surface 23, the incident side stopper transmitting surface 241 is formed on the incident side spacer surface 242, and the incident side optical surface 24 is formed on the upper surface of the incident side stopper transmitting surface 241. ing. The incident side gap 243 is formed by the incident side spacer surface 242. In addition, the light shielding surface 29 having the transmission window 292 opened through the protective surface 291 is formed on the upper surface of the incident side stopper transmission surface 241 as in the basic configuration (see FIG. 1).

  The difference from the basic configuration (see FIG. 1) is that the displacement optical surface 23 is not an electrode, and is conductive, and the lower auxiliary displacement surface 231 made of a transparent conductive film such as a transparent ITO film is replaced with the displacement optical surface 23. It is integrally formed on the lower surface side, and this lower auxiliary displacement surface 231 is used as an electrode. The displacement optical surface 23 of this example has a positive (+) electrical signal on the transmission side optical surface 22 and a negative (−) electrical signal on the lower auxiliary displacement surface 231 and the incident side optical surface 24, as seen in FIG. 2b. By applying a signal, an electrostatic force that attracts the lower auxiliary displacement surface 231 to the transmission side optical surface 22 and an electrostatic force that repels the lower auxiliary displacement surface 231 on the incident side optical surface 24 are generated. The integrated displacement optical surface 23 is displaced toward the transmission side optical surface 22 to change the light interference action of the light path A and the light path B.

  To return the displacement optical surface 23, as seen in FIG. 2a, a positive (+) electrical signal is applied to the transmission side optical surface 22 and the lower auxiliary displacement surface 231, and a negative (-) electrical signal is applied to the incident side optical surface 24. By applying an electrical signal, an electrostatic force that repels the lower auxiliary displacement surface 231 on the transmission side optical surface 22 and an electrostatic force that attracts the lower auxiliary displacement surface 231 on the incident side optical surface 24 are generated, and the incident side stopper transmission surface The displacement optical surface 23 is forcibly displaced together with the lower auxiliary displacement surface 231 until it is brought into close contact with 241. When the displacement optical surface 23 is an electrode and a silicon nitride film or the like is used for the lower auxiliary displacement surface 231, the length of the optical path A between the transmission side optical surface 22 and the displacement optical surface 23 is the same as the basic configuration. Accordingly, the thickness of the transmission side stopper transmission surface 221 is reduced by an amount corresponding to the thickness of the lower layer auxiliary displacement surface 231.

  3a and 3b are sectional views showing another example of the transmission type optical switching element 3 according to the present invention. The optical switching element 3 of this example has a transmission side optical surface 32 on the substrate 31, a transmission side stopper transmission surface 321 on the transmission side optical surface 32, a transmission side spacer surface 322 on the transmission side stopper transmission surface 321, A lower auxiliary displacement surface 331, a displacement optical surface 33, and an upper auxiliary displacement surface 332 are integrally formed on the transmission side spacer surface 322. The transmission side gap 323 is formed by the transmission side spacer surface 322. Then, the incident side spacer surface 342 is formed on the upper auxiliary displacement surface 332, the incident side stopper transmitting surface 341 is formed on the incident side spacer surface 342, and the incident side optical surface 34 is formed on the upper surface of the incident side stopper transmitting surface 341. is doing. The incident side gap 343 is formed by the incident side spacer surface 342. In addition, the light shielding surface 39 having the transmission window 392 opened through the protective surface 391 is formed on the upper surface of the incident side stopper transmission surface 341, which is the same as the basic configuration (see FIG. 1).

  The difference from the basic configuration (see FIG. 1) is that the displacement optical surface 33 is not used as an electrode, and is conductive and has a lower auxiliary displacement surface 331 and an upper auxiliary displacement surface 332 made of a transparent conductive film such as a transparent ITO film. Are integrally formed on the lower surface side and the upper surface side of the displacement optical surface 33, respectively, and the lower layer auxiliary displacement surface 331 and the upper layer auxiliary displacement surface 332 are used as electrodes. 3B, the displacement optical surface 33 of this example applies a positive (+) electric signal to the transmission side optical surface 32, and applies to the lower layer auxiliary displacement surface 331, the upper layer auxiliary displacement surface 332, and the incident side optical surface 34. By applying a negative (−) electric signal, an electrostatic force that attracts the lower auxiliary displacement surface 331 to the transmission side optical surface 32 and an electrostatic force that repels the upper auxiliary displacement surface 332 on the incident side optical surface 34 are generated. The displacement optical surface 33 integral with the lower auxiliary displacement surface 331 and the upper auxiliary displacement surface 332 is displaced toward the transmission side optical surface 32 to change the light interference action of the light path A and the light path B.

  To return the displacement optical surface 33, as shown in FIG. 3 a, positive (+) electrical signals are applied to the transmission side optical surface 32, the lower layer auxiliary displacement surface 331 and the upper layer auxiliary displacement surface 332, and the incident side optical surface 34. A negative (−) electrical signal is applied to the transmission side optical surface 32 to generate an electrostatic force that repels the lower auxiliary displacement surface 331 on the transmission side optical surface 32 and an electrostatic force that attracts the upper auxiliary displacement surface 332 to the incident side optical surface 34. Then, the displacement optical surface 33 integrated with the lower auxiliary displacement surface 331 and the upper auxiliary displacement surface 332 is forcibly displaced until it is brought into close contact with the incident side stopper transmission surface 341. Further, when the displacement optical surface 33 is used as an electrode and a silicon nitride film or the like is used for the lower auxiliary displacement surface 331 and the upper auxiliary displacement surface 332, the length of the optical path A between the transmission side optical surface 32 and the displacement optical surface 33 is set. In order to make the same as the basic configuration, the thickness of the transmission side stopper transmission surface 321 is reduced by an amount corresponding to the thickness of the lower auxiliary displacement surface 331, and the length of the optical path B between the displacement optical surface 33 and the incident side optical surface 34 is reduced. In order to make the same as the basic configuration, the thickness of the incident side stopper transmitting surface 341 is reduced by an amount corresponding to the thickness of the upper auxiliary displacement surface 332. Whether or not the auxiliary displacement surface is used may be selectively determined depending on the material of the displacement optical surface.

  4a and 4b are sectional views showing other examples of the transmission type optical switching element according to the present invention. The optical switching element 4 of the present example is a configuration in which the basic configuration (see FIG. 1) is structurally integrated while simply being stacked vertically and mirror-symmetrically. The lower stage includes a lower transmission side optical surface 42 on the substrate 41, a lower transmission side stopper transmission surface 421 on the transmission side optical surface 42, and a lower transmission side spacer surface 422 on the transmission side stopper transmission surface 421. The lower displacement optical surface 43 is formed on the transmission side spacer surface 422. The lower transmission side gap 423 is formed by the transmission side spacer surface 422. Then, a lower incident side spacer surface 442 is formed on the displacement optical surface 43, and a lower incident side stopper transmitting surface 441 is formed on the incident side spacer surface 442, and a lower step is formed on the upper surface of the incident side stopper transmitting surface 441. An incident side optical surface 44 is formed. The lower incident side gap 443 is formed by the incident side spacer surface 442.

  The upper stage is configured on an intermediate surface 45 formed on the lower incident side optical surface 44. The upper stage includes an upper transmission side optical surface 46 on the intermediate surface 45, an upper transmission side stopper transmission surface 461 on the transmission side optical surface 46, and an upper transmission side on the transmission side stopper transmission surface 461. A spacer surface 462 and an upper displacement optical surface 47 are formed on the transmission side spacer surface 462. The upper transmission side gap 463 is formed by the transmission side spacer surface 462. Then, an upper incident side spacer surface 482 is formed on the displacement optical surface 47, an upper incident side stopper transmitting surface 481 is formed on the incident side spacer surface 482, and an upper step is formed on the upper surface of the incident side stopper transmitting surface 481. An incident side optical surface 48 is formed. The upper incident side gap 483 is formed by the incident side spacer surface 482. In addition, the light shielding surface 49 having the transmission window 492 opened is formed on the upper surface of the incident side stopper transmission surface 481 through the protective surface 491, which is the same as the basic configuration (see FIG. 1).

  As described above, the optical switching element 4 of the present example configured with the upper and lower stages in a mirror-symmetrical relationship includes the optical path A between the lower transmission side optical surface 42 and the lower displacement optical surface 43, and the lower displacement optical surface 43. And the optical path B between the upper transmission optical surface 46 and the upper displacement optical surface 47, the upper displacement optical surface 47, and the upper incident optical surface. A light path D between the surfaces 48, and by simultaneously changing the lengths of the light path A, the light path B, the light path C, and the light path D, synergistic interference of each light, A large light intensity ratio is realized.

  The upper and lower displacement optical surfaces 43 and 47 may be integrally controlled by applying electric signals having the same polarity. For example, as seen in FIG. 4b, positive (+) electrical signals are applied to the lower transmission side optical surface 42 and the upper incident side optical surface 48, the lower displacement optical surface 43, the lower incident side optical surface 44, and the upper step. An electrostatic force that applies a negative (−) electric signal to the transmission optical surface 46 and the upper displacement optical surface 47 of the upper surface to attract the lower displacement optical surface 43 to the lower transmission optical surface 42, and the lower incident side. An electrostatic force that repels the displacement optical surface 43 on the optical surface 44, an electrostatic force that repels the upper displacement optical surface 47 on the upper transmission side optical surface 46, and the displacement optical surface on the upper incident side optical surface 48 The lower displacement optical surface 43 is directed toward the lower transmission optical surface 42, and the upper displacement optical surface 47 is simultaneously displaced toward the upper incident optical surface 48 to generate light. The light interference action of the path A, the light path B, the light path C, and the light path D is changed.

  To return the displacement optical surface 43 and the displacement optical surface 47, as shown in FIG. 4a, the lower transmission optical surface 42, the lower displacement optical surface 43, the upper displacement optical surface 47, and the upper incident optical surface. A positive (+) electrical signal is applied to the surface 48, a negative (−) electrical signal is applied to the lower incident side transmission surface 44 and the upper transmission side optical surface 46, and the lower transmission side optical surface 42 is applied to the lower transmission side optical surface 42. An electrostatic force that repels the displacement optical surface 43, an electrostatic force that attracts the displacement optical surface 43 to the lower incident side optical surface 44, an electrostatic force that attracts the upper displacement optical surface 47 to the upper transmission side optical surface 46, Then, by generating an electrostatic force that repels the displacement optical surface 47 on the upper incident side optical surface 48, the lower displacement optical surface 43 is forcibly displaced until it is in close contact with the lower incident side stopper transmitting surface 441, At the same time, the upper displacement optical surface 47 is forcibly brought into close contact with the upper transmission side stopper transmission surface 461. To displace.

  5a and 5b are sectional views showing another example of the transmission type optical switching element 5 according to the present invention. The optical switching element 5 of this example has a structure in which the lower incident side optical surface 54 is also used as the upper transmission side optical surface when the basic configuration (see FIG. 1) is laminated in the upper and lower stages with mirror symmetry. It is the structure integrated with. The lower stage includes a lower transmission side optical surface 52 on the substrate 51, a lower transmission side stopper transmission surface 521 on the transmission side optical surface 52, and a lower transmission side spacer surface 522 on the transmission side stopper transmission surface 521. A lower displacement optical surface 53 is formed on the transmission side spacer surface 522. The lower transmission side gap 523 is formed by the transmission side spacer surface 522. Then, a lower incident side spacer surface 542 is formed on the displacement optical surface 53, and a lower incident side stopper transmitting surface 541 is formed on the incident side spacer surface 542, and a lower step is formed on the upper surface of the incident side stopper transmitting surface 541. An incident-side optical surface 54 is formed. The lower incident side gap 543 is formed by the incident side spacer surface 542.

  The upper stage includes an upper transmission side stopper transmission surface 561 on the lower incident side optical surface 54, an upper transmission side spacer surface 562 on the transmission side stopper transmission surface 561, and an upper stage on the transmission side spacer surface 562. The displacement optical surface 57 is formed. The upper transmission side gap 563 is formed by the transmission side spacer surface 562. Then, an upper incident side spacer surface 582 is formed on the displacement optical surface 57, an upper incident side stopper transmitting surface 581 is formed on the incident side spacer surface 582, and an upper step is formed on the upper surface of the incident side stopper transmitting surface 581. An incident side optical surface 58 is formed. The upper incident side gap 583 is formed by the incident side spacer surface 582. In addition, the light shielding surface 59 having the transmission window 592 opened is formed on the upper surface of the incident side stopper transmission surface 581 through the protective surface 591 as in the basic configuration (see FIG. 1).

  As described above, the optical switching element 5 of the present example configured in a mirror-symmetrical relationship while sharing the lower incident side optical surface 54 in the upper and lower stages is provided between the lower transmission side optical surface 52 and the lower displacement optical surface 53. And an optical path C between the lower transmission optical surface 52 and the upper displacement optical surface 57, and an optical path C between the lower transmission optical surface 53 and the upper displacement optical surface 57. And an optical path D between the upper displacement optical surface 57 and the upper incident-side optical surface 58, and the lengths of the optical path A, the optical path B, the optical path C, and the optical path D are changed simultaneously. By synthesizing the interference action of each light, a large light intensity ratio is realized.

  The upper and lower displacement optical surfaces 53 and 57 may be controlled integrally by applying electric signals of the same polarity. For example, as seen in FIG. 5b, a positive (+) electrical signal is applied to the lower transmission side optical surface 52 and the upper incident side optical surface 58, the lower displacement optical surface 53, the lower incident side optical surface 54, and the upper step. An electrostatic force that applies a negative (−) electrical signal to the first displacement optical surface 57 to attract the lower displacement optical surface 53 to the lower transmission optical surface 52, and the displacement optical surface to the lower incident optical surface 54. An electrostatic force that repels 53, an electrostatic force that repels the upper displacement optical surface 57 on the lower incident side optical surface 54, and an electrostatic force that attracts the displacement optical surface 57 to the upper incident side optical surface 58 are generated. The lower displacement optical surface 53 is directed toward the lower transmission optical surface 52, and the upper displacement optical surface 57 is simultaneously displaced toward the upper incident optical surface 58, so that the optical path A, the optical path B, the light The light interference action of the path C and the optical path D is changed.

  To return the displacement optical surface 53 and the displacement optical surface 57, as shown in FIG. 5a, the lower transmission optical surface 52, the lower displacement optical surface 53, the upper displacement optical surface 57, and the upper incident optical surface. Static electricity that applies a positive (+) electrical signal to the surface 58 and a negative (−) electrical signal to the lower incident side optical surface 54 to repel the lower displacement optical surface 53 to the lower transmission side optical surface 52 Force, electrostatic force attracting the displacement optical surface 53 to the lower incident side optical surface 54, electrostatic force attracting the upper displacement optical surface 57 to the lower incident side optical surface 54, and upper incident side optical surface 58 Generating an electrostatic force that repels the displacement optical surface 57 and forcibly displacing the lower displacement optical surface 53 until it is brought into close contact with the lower incident side stopper transmission surface 541, and at the same time, the upper transmission side stopper transmission surface. The upper displacement optical surface 57 is forcibly displaced until it is brought into close contact with 561.

  6a and 6b are sectional views showing other examples of the transmission type optical switching element 6 according to the present invention. In the optical switching element 6 of this example, when the basic configuration (see FIG. 1) is stacked in the upper and lower stages in a mirror-symmetrical relationship, the lower incident side optical surface 64 is also used as the upper transmission side optical surface. It is a structure that is structurally integrated while omitting the incident side optical surface. The lower stage includes a lower transmission side optical surface 62 on the substrate 61, a lower transmission side stopper transmission surface 621 on the transmission side optical surface 62, and a lower transmission side spacer surface 622 on the transmission side stopper transmission surface 621. The lower displacement optical surface 63 is formed on the transmission side spacer surface 622. The lower transmission side gap 623 is formed by the transmission side spacer surface 622. Then, a lower incident side spacer surface 642 is formed on the displacement optical surface 63, and a lower incident side stopper transmitting surface 641 is formed on the incident side spacer surface 642, and a lower step on the upper surface of the incident side stopper transmitting surface 641. An incident side optical surface 64 is formed. The lower incident side gap 643 is formed by the incident side spacer surface 642.

  The upper stage includes an upper transmission side stopper transmission surface 661 on the lower incident side optical surface 64, an upper transmission side spacer surface 662 on the transmission side stopper transmission surface 661, and an upper stage on the transmission side spacer surface 662. The displacement optical surface 67 is formed. The upper transmission side gap 663 is formed by the transmission side spacer surface 662. Then, an upper incident side spacer surface 682 is formed on the displacement optical surface 67, and a protective surface 691 that also serves as an upper incident side stopper transmission surface is formed on the incident side spacer surface 682, and the protective surface 691 is interposed therebetween. In addition, a light shielding surface 69 having a transmission window 692 opened is formed. The upper incident side gap 683 is formed by the incident side spacer surface 682.

  In this way, the optical switching element 6 of the present example, which is configured in a mirror-symmetrical relationship with the lower-stage incident-side optical surface 64 shared by the upper and lower stages and omitting the upper-stage incident-side optical surface, has the lower-stage transmission-side optical In addition to the optical path A between the surface 62 and the lower displacement optical surface 63 and the optical path B between the lower displacement optical surface 63 and the lower incident optical surface 64, the lower incident optical surface 64 and the upper displacement An optical path C between the optical surfaces 67 is provided, and by changing the lengths of the optical path A, the optical path B, and the optical path C at the same time, the interference action of each light is synergized, and a large light intensity ratio To realize. Since this optical switching element 6 does not have the optical path D, the light intensity ratio is slightly lower than that of the optical switching element 5 shown in FIG. 5, for example. Since the incident side optical surface is omitted, the transmittance is high.

  The upper and lower displacing optical surfaces 63 and the displacing optical surface 67 may be controlled integrally by applying electric signals of the same polarity. For example, as can be seen in FIG. 6b, a positive (+) electrical signal is applied to the lower transmission optical surface 62 and negative (to the lower displacement optical surface 63, the lower incident optical surface 64, and the upper displacement optical surface 67. An electrostatic signal that applies the electrical signal of −) to attract the lower displacement optical surface 63 to the lower transmission side optical surface 62, and an electrostatic force that repels the displacement optical surface 63 to the lower incidence side optical surface 64; An electrostatic force that repels the upper displacement optical surface 67 is generated on the lower incident side optical surface 64, and the lower displacement optical surface 63 is directed to the lower transmission optical surface 62, and at the same time, the upper displacement optical surface 67 is protected. Displacement toward the surface 691 changes the light interference action of the light path A, light path B, and light path C.

  To return the displacement optical surface 63 and the displacement optical surface 67, as shown in FIG. 6a, the lower transmission optical surface 62, the lower displacement optical surface 63, and the upper displacement optical surface 67 are positive (+). An electrostatic force that applies a negative (−) electrical signal to the lower incident side optical surface 64 to repel the lower displacement optical surface 63 on the lower transmission side optical surface 62, and the lower incident side optical surface Until an electrostatic force that attracts the displacement optical surface 63 to the surface 64 and an electrostatic force that attracts the upper displacement optical surface 67 to the lower incident side optical surface 64 are generated and brought into close contact with the lower incident side stopper transmitting surface 641 The lower displacement optical surface 63 is forcibly displaced, and at the same time, the upper displacement optical surface 67 is forcibly displaced until it is brought into close contact with the upper transmission side stopper transmission surface 661.

Next, the operation principle of the transmission type optical switching element according to the present invention will be described with reference to FIGS. 1 and 2 showing the basic configuration. In the present invention, the length of the optical path A between the transmission side optical surface 12 and the displacement optical surface 13 and the length of the optical path B between the displacement optical surface 13 and the incident side optical surface 14 are changed, respectively. The interference effect of light seen in the “Fabry-Perot interference filter” is changed. Here, when the optical switching element 1 of the present invention is considered as the Fabry-Perot interference filter, if the incident light is incident orthogonally to the incident side optical surface 14, the transmittance of the transmitted light is approximately
IT / I ₀ = [1-K / (1-R)] ² {1+ [4R / (1-R) ² ] sin ² (2πh / λ)} ⁻¹
Given in.

Here, I ₀ : incident light intensity, IT: transmitted light intensity, K: absorption coefficient, R: reflection coefficient, T: transmission coefficient, h: effective optical path length of two optical surfaces (h = nt) , N is the effective refractive index between the two optical surfaces, t is the distance between the two optical surfaces), λ: the wavelength of the incident light, and K + R + T = 1. The [1-K / (1-R)] ² term on the right side of the above equation indicates the attenuation rate with respect to the incident light intensity. If the maximum light intensity of the transmitted light is ITmax and the incident light intensity is I ₀ , (ITmax / I ₀ ). Also, the {1+ [4R / (1-R) ² ] sin ² (2πh / λ)} ⁻¹ term on the right side of the above expression represents the ratio IT / ITmax of the light intensity of transmitted light to ITmax.

  In general, the maximum light intensity ITmax of transmitted light is the light intensity when the effective light path length h is m (λ / 2), and the minimum light intensity ITmin of transmitted light is the effective light path length. It represents the light intensity when h is n (λ / 2) + λ / 4. Here, m and n are integers. For example, if the effective optical path length h changes from λ to (5/4) λ by λ / 4, IT / ITmax decreases monotonically from 1.0 and the interval h is (5/4) λ. Sometimes the minimum value. Since the change in the light intensity of the transmitted light depends on R, it can be seen that R can be increased in order to clearly switch between the ON state and the OFF state. On the other hand, when it is desired to change the light intensity of the transmitted light continuously (analog) by the electrical signals applied to both optical surfaces, that is, to obtain a gradual change in IT / ITmax, R is decreased. do it.

In the optical path A between the transmission side optical surface 12 and the displacement optical surface 13, the minimum light intensity ITmin of the transmitted light is the effective length of the optical path A h = n ₁ t ₁ + n ₀ g = (5/4) Obtained in the case of λ (FIG. 1a). Here, n ₁ and t ₁ are the refractive index and film thickness of the transmission side stopper transmission surface 121, and n ₀ and g are the refractive indexes of the transmission side gap 123 and the incident side gap 143 (in the case of air, n ₀ = 1.0). ) And intervals. On the other hand, the maximum light intensity ITmax of the transmitted light is obtained when the effective length of the optical path A is h = n ₁ t ₁ = λ (in the case of FIG. 1b).

Similarly, in the optical path B between the displacement optical surface 13 and the incident-side optical surface 14, the effective optical path B has a length h = n ₂ t ₂ = (5/4) λ (in the case of FIG. 1a). In addition, the minimum light intensity ITmin of the transmitted light is obtained. Here, n ₂ and t ₂ are the refractive index and film thickness of the incident side stopper transmitting surface 141. On the other hand, the maximum light intensity ITmax of the transmitted light is obtained when the length of the effective optical path B is h = n ₂ t ₂ + n ₀ g = 3λ / 2 (in the case of FIG. 1b). Here, n ₀ and g are the refractive index (in the case of air, n ₀ = 1.0) and interval of the transmission side gap 123 and the incident side gap 143. From this, it can be seen that the transmission side gap 123 and the incident side gap 143 may be set precisely so as to satisfy g = λ / 4 (when n ₀ = 1.0).

In the optical switching element 2 seen in FIG. In this optical switching element 2, unlike the basic configuration (see FIG. 1), the displacement optical surface 23 and the lower layer auxiliary displacement surface 231 are integrally displaced. Therefore, the minimum light intensity ITmin of the transmitted light is obtained when the effective optical path A length h = n ₃ t ₃ + n ₄ t ₄ + n ₀ g = (5/4) λ (in the case of FIG. 2a). It is done. Here, n ₃ and t ₃ are the refractive index and film thickness of the transmission side stopper transmission surface 221, n ₄ and t ₄ are the refractive index and film thickness of the lower auxiliary displacement surface 231, and n ₀ and g are transmission side. The refractive index of the gap 223 and the incident side gap 243 (in the case of air, n ₀ = 1.0) and the interval.

On the other hand, the maximum light intensity ITmax of the transmitted light is obtained when the length of the effective optical path A is h = n ₃ t ₃ + n ₄ t ₄ = λ (in the case of FIG. 2b). From this, it can be seen that the transmission-side gap 223 and the incident-side gap 243 need only be set precisely so as to satisfy g = λ / 4 (when n ₀ = 1.0). Since the optical path B is the same as described above, the description is omitted. Here, if the transmission side stopper transmission surface 121 of the basic configuration (see FIG. 1), the transmission side stopper transmission surface 221 and the lower layer auxiliary displacement surface 231 shown in FIG. 2 are formed of the same material, t ₁ = t ₃ + a t _4.

In the optical switching element 3 seen in FIG. The optical path A is the same as described above with reference to FIG. On the other hand, the optical path B is different from that described above with reference to FIG. 1 because the upper auxiliary displacement surface 332 is further formed. In the optical path B in the optical switching element 3, the minimum light intensity ITmin of the transmitted light is an effective optical path B length h = n ₅ t ₅ + n ₆ t ₆ = (5/4) λ (FIG. 3a). In the case of). Here, n ₅ and t ₅ are the refractive index and film thickness of the incident side stopper transmitting surface 341, and n ₆ and t ₆ are the refractive index and film thickness of the upper auxiliary displacement surface 332.

On the other hand, the maximum light intensity ITmax of the transmitted light is obtained when the length of the effective light path B is h = n ₅ t ₅ + n ₆ t ₆ + n ₀ g = 3λ / 2 (in the case of FIG. 3b). It is done. From this, it can be seen that the transmission side gap 323 and the incident side gap 343 need only be set precisely so as to satisfy g = λ / 4 (when n ₀ = 1.0). Here, if the transmission side stopper transmission surface 121 of the basic configuration (see FIG. 1), the incident side stopper transmission surface 341 and the upper auxiliary displacement surface 332 shown in FIG. 3 are formed of the same material, t ₂ = t ₅ + the t _6.

In the optical switching element 1 shown in FIG. 1, the length h of the optical path A is h = n ₁ t ₁ + n ₀ g≈ (5/4) λ≈for the wavelength λ = 1.3 to 1.5 μm of the incident light. 1.6 μm. When both the transmission side gap 123 and the incident side gap 143 are filled with air (n ₀ = 1.0), g = λ / 4 and n ₁ t ₁ = λ. Further, since the transmission side stopper transmission surface 121 made of a silicon nitride film has n ₁ = 2.0, t ₁ = λ / 2.0≈0.7 μm. In the optical switching element 1 of the present invention, the transmission side spacer surface 122 is formed of a phosphor glass film or the like, so that the film thickness of the transmission side spacer surface 122 is λ / 4≈0.4 μm. it can. This high processing accuracy is the same in other examples (see FIGS. 2 to 6).

  In the optical switching element of the present invention, other films can be formed as long as the change of the interference action of light is not hindered. For example, an antireflection film that prevents reflection of incident light or a protective surface that prevents foreign matter from entering from the outside may be formed on the surface of the optical switching element. In this case, a light-shielding surface having a transmissive window opened may be formed on the upper surface or the lower surface of the antireflection film or the protective surface. Moreover, although the case where incident light is input from the incident side optical surface side is illustrated in the above description, since there is no directionality other than the optical path A, for example, even if incident light is irradiated onto the transmission side optical surface, A similar switching operation can be realized. Further, although the above description has been for the transmission type optical switching element, the same switching operation as described above can be realized for the reflection type optical switching element according to the present invention.

  As can be seen from the above description, the optical switching element of the present invention can accurately set the transmission side gap and the incident side gap that determine the interference action of light that switches between transmission and non-transmission. From the outside light to the ultraviolet light, particularly short wavelength light can be used as incident light. Therefore, switching between transmission and non-transmission in the transmissive optical switching element 1 having the basic configuration (see FIG. 1) is described using g-line (λ = 436 nm), which is also used in photolithography, as incident light. To do.

What is the configuration of the optical switching element 1 that uses g-line (λ = 436 nm) as incident light? It is as follows. The substrate 11 is made of a quartz glass plate having a thickness of about 0.5 mm, and a transmission side optical surface 12 is formed on the surface of the substrate 11 with a conductive 20 nm thick polycrystalline silicon film. Next, a silicon nitride film of t ₁ = 213 nm (refractive index n ₁ = 2.05 at λ≈0.4 μm) is formed on the upper surface of the transmission side optical surface 12 so as to satisfy the requirement of n ₁ t ₁ = λ. The transmission side stopper is formed as a transmission surface 121. On the upper surface of the transmission side stopper transmission surface 121, a transmission side spacer surface 122 is formed of a phosphor glass film. The thickness of the transmission side spacer surface 122 corresponds to the transmission side gap 123.

The displacement optical surface 13 is made of a conductive polycrystalline silicon film having a thickness of 20 nm, and is formed on the upper surface of the transmission side spacer surface 122. Then, an incident side spacer surface 142 made of a phosphor glass film is formed on the upper surface of the displacement optical surface 13, and an incident side stopper transmitting surface 141 made of a silicon nitride film is formed on the upper surface of the incident side spacer surface 142. Here, the thickness of the incident side stopper transmitting surface 141 is set to 265 nm so as to satisfy n ₂ t ₂ = (5/4) λ. The incident side optical surface 14 is formed on the upper surface of the incident side stopper transmitting surface 141 by a 20 nm thick polycrystalline silicon film having conductivity. The transmission side gap 123 and the incident side gap 143 are formed by selectively etching the transmission side spacer surface 122 and the incident side spacer surface 142, respectively. In this case, the transmission side gap 123 and the incident side gap 143 are set so that the sum thereof is λ / 4 = 109 nm.

The optical switching element 1 thus manufactured has an absorption coefficient K of 0.25 (= optical path A between the transmission side optical surface 12 and the displacement optical surface 13 each made of a 20 nm thick polycrystalline silicon film when the incident light is λ = 436 nm. The total absorption coefficient of the transmission side optical surface 12 and the displacement optical surface 13), and similarly, the reflection coefficient of the optical path A is R = 0.4. From the absorption coefficient K and the reflection coefficient R, in the optical path A, the maximum light intensity ITmax = 0.34I ₀ and the minimum light intensity ITmin = 0.06I ₀ , and the transmitted light attenuates to about 1/3 with respect to the incident light. The light intensity ratio ITmax / ITmin≈5. From this point, in the entire optical switching element 1 of the present invention having the optical path A and the optical path B in series, the transmitted light attenuates to about 1/9 with respect to the transmitted light, but the light intensity ratio ITmax / ITmin is about 25 times. It becomes. Therefore, the configuration of this example can be used as a transmission type optical switching element for ultraviolet light (g-line (λ = 436 nm)).

  Next, an image display device using the optical switching element of the present invention will be described. The image display device 7 (see FIG. 7 or FIG. 10) of the present invention is an optical switching device in which, for example, the optical switching element 1 having the above-described basic configuration (see FIG. 1) is optimized for red light (R) that is, for example, three primary colors. The element is configured as an R switching element 721, an optical switching element optimized for green light (G) as a G switching element 722, and an optical switching element optimized for blue light (B) as a B switching element 723 ( An optical switching element optimized for ultraviolet light (U) is configured as a U switching element 724 (see FIG. 9 below).

First, the image display device 7 using three primary colors will be described. In the following description, the configuration inside the optical switching element is based on the description and reference numerals of FIG. Taking the configuration of the optical switching element optimized for the g-line (λ = 436 nm) described above as an example, the refractive index of the silicon nitride film is 2.03 for red light (R, λ = 700 nm), and green light (G, λ = 540 nm) is 2.03, and blue light (B, λ = 460 nm) is 2.04. From this, the film thickness t ₁ of the transmission side stopper transmission surface 121 is set to 345 nm for the R switching element 721, 266 nm for the G switching element 722, and 230 nm for the B switching element 723. Similarly, the thickness t ₂ of the incidence-side stopper transmission surface 141, 431 nm in R switching elements 721, 333 nm in G switching element 722 is set at B switching elements 723 to 282 nm. Since the transmission side gap 123 and the incident side gap 143 of each of the optical switching elements 721, 722, 723 are λ / 4, they are set to 175 nm for the R switching element 721, 135 nm for the G switching element 722, and 115 nm for the B switching element 723.

Here, when the transmission side optical surface 12, the displacement optical surface 13 and the incident side optical surface 14 are all made of a 20 nm thick polycrystalline silicon film having conductivity, red light (R), green light (G) And the respective absorption coefficients K for blue light (B) are 0.01, 0.02 and 0.16, and the reflection coefficients R are 0.34, 0.36 and 0.38. Therefore, each attenuation rate (ITmax / I ₀ ) is 0.98 for the optical path A and the optical path B of the R switching element 721, 0.97 for the optical path A and the optical path B of the G switching element 722, and 0.97 for the B switching element 723, respectively. It becomes 0.55 in each of the optical path A and the optical path B. Each light intensity ratio (ITmax / ITmin) is 4.1 for the optical path A and optical path B of the R switching element 721, 4.5 for each of the optical path A and optical path B of the G switching element 722, and light of the B switching element 723. It becomes 5.0 in each of the path A and the optical path B. Accordingly, the attenuation rate as the R switching element 721 is 0.96, the light intensity ratio is 17, the attenuation rate as the G switching element 722 is 0.94, the light intensity ratio is 20, and the attenuation rate as the B switching element 723 is 0.30, the light intensity. The ratio is 25.

  As can be seen, as the wavelength λ of the incident light becomes longer, the reflection coefficient R of the polycrystalline silicon becomes lower, so the light intensity ratio becomes lower. Although the difference in the light intensity ratio means a difference in switching operation, it is desirable that the light intensity ratios be the same as much as possible as the optical switching elements used in the same image display device. Therefore, the transmission side optical surface 12, the displacement optical surface 13, and the incident side optical surface 14 are a Mo film having a substantially constant reflectance R = 0.55 with respect to a wavelength λ of 300 to 1000 nm (1.0 μm), or R = 0.60. While using the W film, the film thickness may be set so that the absorption coefficient K = 0.20. In this case, attenuation rate = 0.30 and light intensity ratio = 144 can be expected for the optical switching element using Mo film, and attenuation ratio = 0.25 and light intensity ratio = 256 can be expected for the optical switching element using W film. Thus, in the R switching element 721, the G switching element 722, and the B switching element 723, the transmission characteristics can be improved by configuring the optical surface with a Mo film or a W film instead of the polycrystalline silicon film. The same applies to the reflective R switching element 721, G switching element 722, and B switching element 723, although the description is omitted.

  7a to 7c are a configuration diagram (FIG. 7a) of an image display device 7 in which an R switching element 721, a G switching element 722, and a B switching element 723 are two-dimensionally arranged on the same glass substrate 71; It is explanatory drawing (FIG. 7b and FIG. 7c) showing the control system of the electric signal applied to the optical switching elements 721,722,723. In the image display device 7 of this example, a pixel unit 72 including the above-described R switching element 721, G switching element 722, and B switching element 723 is two-dimensionally arranged on the same glass substrate 71, and the display surface is displayed. 73 is composed. Then, a signal line for individually applying an electric signal is connected to each of the optical switching elements 721, 722, 723 so that the light intensity of the transmitted light (or reflected light) of each of the optical switching elements 721, 722, 723 can be increased or decreased. Incident light from an integrated light source 741 made of a fluorescent tube or the like is dispersed and input to the entire pixel units 72 arranged two-dimensionally by an incident light input unit 75. As the integrated light source 741, in addition to a visible light diode described later, various conventionally known light sources can be used.

  The color development and light intensity of the pixel unit 72 does not adjust the light intensity of the incident light input from the integrated light source 741, but increases or decreases the time of each ON state of the light switching elements 721, 722, and 723 constituting each pixel unit 72. Therefore, it can be adjusted easily. For example, as shown in FIG. 7b, by increasing / decreasing the number of times of applying an electric signal having a pulse width obtained by equally dividing the unit lighting time of the pixel unit 72 within a range in which the sum of the unit application times does not exceed the unit lighting time. The color development and light intensity of the pixel unit 72 can be controlled by the intensity obtained by integrating the electric signal with the unit lighting time. Further, as shown in FIG. 7c, by increasing or decreasing the continuous application time of the electric signal applied in a continuous application time equal to or less than the unit lighting time of the pixel unit 72 within a range not exceeding the unit lighting time, The color development and light intensity of 72 can be controlled by the intensity obtained by integrating the electric signal with the unit lighting time. In any case, since the number of times of applying an electric signal or the continuous application time can be easily controlled, the color development and light intensity of the pixel unit 72 can be precisely controlled.

  Specifically: For example, when a color image is scanned at 30 frames / second, an image conversion of about 30 ms / frame is required. If the pixel units 72 are two-dimensionally arranged at 1000 × 1000, the readout time for each scan is 33 ms / 1000 = 33 μs. Here, according to the example shown in FIG. 7b, if the gradation of each pixel unit 72 is set to 1000 levels, the electrical signal may have 1000 times of application during the unit lighting time. If the pulse width and pulse interval of each electrical signal are equal, the pulse width of one electrical signal is 33 μs / 2000 = 16 nsec.

  In order to keep the pulse width of the electrical signal with high accuracy, it is only necessary to use each of the optical switching elements 721, 722, 723 having a switching operation of about 2 nsec or less if the rise time and the fall time are about 1/10 of the pulse width. Become. In the example shown in FIG. 7c, if the gradation is 1000 steps, the continuous application time is increased or decreased at a pitch of 33 μs / 1000 = 33 nsec or less. In this case, since each electric signal is applied without an interval, each of the optical switching elements 721, 722, and 723 capable of switching operation of 3.3 nsec or less is used by setting the pulse rise time and fall time to 1/10 or less of 33 nsec. It will be good.

  When the lighting of the pixel unit 72 is controlled, it is understood that the optical switching elements 721, 722, and 723 constituting the pixel unit 72 are required to perform a very high speed switching operation, that is, a switching operation of several nsec or less. In this respect, the optical switching element of the present invention realizes an extremely high-speed switching operation, and can sufficiently meet the above specific requirements. Furthermore, since a high-definition image is displayed, the unit lighting time per pixel is shortened, and the switching operation required when the gradation is increased is faster, but the optical switching element of the present invention has such a requirement. Can also respond. As described above, the present invention realizes an optical switching element having a large light intensity ratio and a high-speed switching operation, thereby enabling high contrast and high definition of an image display apparatus using the optical switching element.

  FIG. 8 is a configuration diagram showing an image display device in which a pixel unit is configured by three types of R switching elements 721, G switching elements 722, and B switching elements 723 corresponding to the three primary colors. The image display device 7 of this example receives three types of incident light (red light, green light, and blue light) each having three single colors from a visible light diode that is a light source (not shown), and each optical switching element. Input to 721,722,723. Each of the optical switching elements 721, 722, 723 constituting each pixel unit 72 may be plural. Since the pixel units 32 are two-dimensionally arranged on the glass substrate 71, the light switching elements 721, 722, and 723 constituting each pixel unit 72 are individually controlled to control the display surface 73 (transmitted light of the light switching elements 721, 722, and 723). The image can be displayed on the surface where the light is projected.

  FIG. 9 is a configuration diagram showing the image display device 7 in which the pixel unit 72 is configured by four identical U switching elements 724 corresponding to the three primary colors and white. The image display device 7 uses, as incident light, single-wavelength ultraviolet light having a light source (not shown) as an ultraviolet light diode made of a GaN semiconductor or the like. The three primary colors and the white color in the pixel unit 72 are a red phosphor screen 731, a green phosphor screen 732, a blue phosphor screen 733, or a white phosphor screen 734 that emits light received from the U-switching element 724 (R, G, B and W). From this, the display surface 73 of this example is composed of the phosphor screens 731,732,733,734. One U switching element 724 of each pixel unit 72 is assigned to each phosphor screen 731,732,733,734.

  In this example, a white fluorescent screen 734 is combined with a red fluorescent screen 731, a green fluorescent screen 732, and a blue fluorescent screen 733 corresponding to the three primary colors of light in order to realize a beautiful color image with good color development. However, when a simple color image is sufficient, only the red phosphor screen 731, the green phosphor screen 732, and the blue phosphor screen 733 may be used. A plurality of U switching elements 724 constituting each pixel unit 72 may be provided for each phosphor screen 731,732,733,734. Accordingly, the U switching element 724 of each pixel unit 72 receives the same ultraviolet light, and individually switches the U switching element 724 corresponding to each phosphor screen 731, 732, 733, 734 to transmissive or non-transmissive so that Realizes light emission of three primary colors.

  FIG. 10 is a configuration diagram corresponding to FIG. 7a of the image display device 7 in which individual light sources 742 are sequentially switched on and off in accordance with image scanning. The image display device 7 according to the present invention has an R switching element 721, a G switching element 722, and a B switching element 723 on the upper surface of the same glass substrate 71 as seen in the above-described examples (FIGS. 7a, 8 and 9). The pixel units 72 are arranged in a two-dimensional array, and incident light is input from the light source 742 to the all-optical switching elements 721, 722, and 723. Since it is difficult for the actual image display device 7 to directly input incident light uniformly from the individual light sources 742 to the all-optical switching elements 721, 722, 723, as shown in FIG. Incident light is guided from each light source 742 to all-optical switching elements 721, 722, 723 via 75. As the light source 742, the visible light diode described above can be used.

  In this example, screen scanning is used as the essence of the image display device 7 for displaying a moving image, and a plurality of light sources 742 are switched on and off in synchronization with the scanning signal. As a result, only the light source 742 corresponding to the optical switching elements 721, 722, and 723 whose transmission or non-transmission is switched in accordance with the screen scan needs to be turned on, and many light sources 742 are turned off as a result. Power saving can be achieved.

  Hereinafter, with respect to the optical switching element of the present invention, a prototype was manufactured in which the displacement optical surface was displaced, and the improvement in the light intensity ratio was confirmed. The reason for fixing the displacement optical surface is to simplify the configuration of the prototype. 11a is a cross-sectional view corresponding to FIG. 1a showing a prototype (Comparative Example 1) corresponding to the OFF state of the optical path A (or optical path B), and FIG. 11b corresponds to the ON state of the optical path A (or optical path B). FIG. 11 c is a cross-sectional view corresponding to FIG. 1 b showing a prototype (Comparative Example 2), and FIG. 11 c is a trial of a basic configuration corresponding to the OFF state of each of the optical path A and the optical path B by superimposing two Comparative Examples 1 vertically FIG. 11d is a cross-sectional view corresponding to FIG. 1a representing the work (Example 1), and FIG. 11d is a test of a basic configuration corresponding to the ON state of each of the optical path A and the optical path B by superposing two comparative examples 2 vertically. FIG. 2 is a cross-sectional view corresponding to FIG.

  In Comparative Example 1, Comparative Example 2, Example 1 and Example 2, the length of the optical path A or the optical path B is changed while using the same material. For example, when g-line (λ = 436 nm), which is ultraviolet light, is used as the incident light, as shown in FIG. 11a, in Comparative Example 1, the transmission side optical is formed on the upper surface of a substrate 81 made of a quartz wafer having a thickness of 0.5 mm. A polycrystalline silicon film having a thickness of 21 nm is formed as the surface 82 by the CVD (chemical vapor deposition) method, and the upper surface of the transmission-side optical surface 82 is 263 nm (refractive as the gap forming surface 83 corresponding to the optical path A in the OFF state. A silicon nitride film having a thickness of 2.05 (corresponding to 5λ / 4 with a rate of 2.05) is formed by the CVD method, and a 21 nm polycrystalline silicon film is formed on the upper surface of the gap forming surface 83 as the displacement optical surface 85 by the CVD method. ing. Since the displacement optical surface 85 of Example 1 does not move, Comparative Example 2 corresponds to 207 nm corresponding to the optical path A in the ON state as the gap formation surface 84 (corresponding to λ with a refractive index of 2.05) as seen in FIG. ) Thick silicon nitride film is formed by the CVD method. As shown in FIG. 11c, Example 1 has a configuration in which the two comparative examples 1 are vertically symmetrical, and the displacement optical surfaces 85 and 85 are in contact with each other. As can be seen from the above, the displacement optical surfaces 85 and 85 are in contact with each other so that the two comparative examples 2 are vertically symmetrical.

  FIG. 12 is a graph showing the measurement results of transmittance at wavelengths of 250 nm to 2000 nm for Comparative Example 1, Comparative Example 2, Example 1 and Example 2. The transmittance is obtained by subtracting the transmittance of the substrate 81, which is a quartz wafer. In Comparative Example 1, Comparative Example 2, Example 1 and Example 2 in FIG. 12, the periodicity of the transmittance is caused by the interference action of light. Here, in Example 1 and Example 2, a minute short period waveform overlaps with a long period waveform observed in a long wavelength region. When the comparative example 2 is overlaid, it is considered to be noise due to the interference action of light generated due to the air layer formed between the contacting optical surfaces 85 and 85. Is negligible in the short wavelength region. In addition, for example, Comparative Example 1 was manufactured assuming an OFF state, and Comparative Example 2 was assumed to be an ON state. However, since they have mutually opposite transmittance characteristics, in the following, according to the relative magnitude of the transmittance, one is turned on and the other Was decided to calculate the light intensity ratio.

  FIG. 13a is a graph showing the transmittance and light intensity ratio of Comparative Example 2 and Example 2 in which the wavelength range is 350 nm to 500 nm, and FIG. 13b is the maximum value in the wavelength range of 400 nm to 550 nm. It is a graph showing the transmittance | permeability and light intensity ratio of the comparative example 1 and Example 1 which show. Here, for example, the respective light intensity ratios of Comparative Example 2 and Example 2 in FIG. 13a are considered as Comparative Example 1 or Example 2, assuming that Comparative Example 2 or Example 2 is in the ON state and Comparative Example 1 or Example 1 is in the OFF state. It is calculated from the ratio of the transmittance of Comparative Example 2 or Example 2 to the transmittance of Example 1. The light intensity ratios of Comparative Example 1 and Example 1 in FIG. 13b are the same as those of Comparative Example 2 or Example 2, assuming that Comparative Example 1 or Example 1 is in the ON state and Comparative Example 2 or Example 2 is in the OFF state. It is calculated from the ratio of the transmittance of Comparative Example 1 or Example 1 to the transmittance.

  From FIG. 13a, although Comparative Example 2 shows a maximum transmittance of about 19% at a wavelength = about 410 nm, the light intensity ratio remains at about 9, and Example 2 also has a maximum transmittance of about 9% at a wavelength = about 410 nm. Although decreased, the light intensity ratio improved to about 32. From FIG. 13b, although Comparative Example 1 shows a maximum transmittance of about 50% at a wavelength = 480 nm, the light intensity ratio is only about 8, and Example 1 has a maximum transmittance of about 26% at a wavelength = about 480 nm. Although decreased, the light intensity ratio increased to about 19. From this, it can be seen that the optical switching element of the present invention provided with the optical path A and the optical path B in series greatly improves the light intensity ratio required for each pixel of the image display device, although the transmittance is reduced. Thus, the effectiveness of the present invention can be proved.

It is sectional drawing which shows the transmission type optical switching element based on this invention whose transmitted light is the minimum light intensity. It is sectional drawing of the transmission type optical switching element based on this invention whose transmitted light is the maximum light intensity. It is sectional drawing which shows another example of the transmission type optical switching element based on this invention whose transmitted light is the minimum light intensity. It is sectional drawing which shows another example of the transmissive | pervious optical switching element based on this invention whose transmitted light is the maximum light intensity. It is sectional drawing which shows another example of the transmission type optical switching element based on this invention whose transmitted light is the minimum light intensity. It is sectional drawing which shows another example of the transmissive | pervious optical switching element based on this invention whose transmitted light is the maximum light intensity. It is sectional drawing which shows another example of the transmission type optical switching element based on this invention whose transmitted light is the minimum light intensity. It is sectional drawing which shows another example of the transmissive | pervious optical switching element based on this invention whose transmitted light is the maximum light intensity. It is sectional drawing which shows another example of the transmission type optical switching element based on this invention whose transmitted light is the minimum light intensity. It is sectional drawing which shows another example of the transmissive | pervious optical switching element based on this invention whose transmitted light is the maximum light intensity. It is sectional drawing which shows another example of the transmission type optical switching element based on this invention whose transmitted light is the minimum light intensity. It is sectional drawing which shows another example of the transmissive | pervious optical switching element based on this invention whose transmitted light is the maximum light intensity. It is a block diagram of the image display apparatus comprised by three-dimensionally arranging three types of optical switching elements on the same glass substrate. It is explanatory drawing showing the control system of the electric signal applied to each optical switching element. It is explanatory drawing showing the control system of the electric signal applied to each optical switching element. It is a block diagram showing the image display apparatus which comprised the pixel unit from three types of optical switching elements corresponding to three primary colors. It is a block diagram showing the image display apparatus which comprised the pixel unit from four same optical switching elements corresponding to three primary colors and white. It is a block diagram of the image display apparatus which switches an individual light source sequentially on and off according to the scanning of an image. It is sectional drawing equivalent to FIG. 1 a showing the prototype (comparative example 1) equivalent to the OFF state of the optical path A (or optical path B). It is sectional drawing equivalent to FIG. 1 b showing the prototype (comparative example 2) equivalent to the ON state of the optical path A (or optical path B). FIG. 1B is a cross-sectional view corresponding to FIG. It is sectional drawing equivalent to FIG. 1 b showing the prototype (Example 2) of the basic composition equivalent to the ON state of each of the optical path A and the optical path B. It is a graph of the measurement result of the transmittance | permeability in the wavelength of 250 nm-2000 nm of each of Comparative Example 1, Comparative Example 2, Example 1 and Example 2. It is a graph showing the transmittance | permeability and light intensity ratio of the comparative example 2 and Example 2 which show a maximum value in the wavelength range of 350 nm-500 nm. It is a graph showing the transmittance | permeability and light intensity ratio of the comparative example 1 and Example 1 which show a maximum value in the wavelength range of 400 nm-550 nm. It is sectional drawing of the conventional transmissive | pervious optical switching element whose transmitted light is the maximum light intensity ITmax. It is sectional drawing of the conventional transmissive | pervious optical switching element which arrange | positioned three optical surfaces and made light interfere twice.

Explanation of symbols

1 Optical switching element
11 Board
12 Transmission side optical surface
121 Transmission side stopper Transmission surface
122 Transmission side spacer surface
123 Transmission side gap
13 Displacement optical surface
14 Incident side optical surface
141 Entrance stopper transmission surface
142 Incident side spacer surface
143 Incident side gap
19 Shading surface
191 Protective surface
192 Transmission window 2 Optical switching element 3 Optical switching element 4 Optical switching element 5 Optical switching element 6 Optical switching element 7 Image display device
721 R switching element
722 G switching element
723 B switching element
724 U switching element
91 Conventional optical switching devices
92 Conventional optical switching element A Optical path B Optical path C Optical path D Optical path

Claims (23)

A transmission-side optical surface that is fixed in position, a displacement optical surface that is displaced by a displacement means, and an incident-side optical surface that is fixed in position are arranged in the order described, and an optical path A between the transmission-side optical surface and the displacement optical surface The optical path B is formed between the displacement optical surface and the incident side optical surface, and the length of the optical path A and the optical path B is increased or decreased in a reciprocal relationship by displacing the displacement optical surface by the displacement means. By changing the interference action of the light in the optical path A and the optical path B, the light intensity of the transmitted light from the transmission side optical surface or the reflected light from the incident side optical surface with respect to the incident light irradiated on the incident side optical surface is changed. An optical switching element that is changed. Position-fixed transmission side optical surface, lower-stage displacement optical surface displaced by the displacement means, position-fixed lower-stage intermediate optical surface, position-fixed upper-stage intermediate optical surface, and upper-stage displacement optics displaced by the displacement means And a fixed incident-side optical surface arranged in the order described above, between the transmission-side optical surface and the lower-stage displacement optical surface, and between the lower-stage displacement optical surface and the lower-stage intermediate optical surface , An optical path C between the upper intermediate optical surface and the upper displacement optical surface, and an optical path D between the upper displacement optical surface and the incident-side optical surface. By displacing one or both of the lower displacing optical surface and the upper displacing optical surface, the length of the optical path A and the optical path B is increased or decreased in a reciprocal relationship, and the light of the optical path A and the optical path B is The interference action is changed, and the length of the optical path C and the optical path D Accordingly, the interference action of the light in the light path C and the light path D is changed to increase or decrease the light, and the transmitted light from the transmission side optical surface or the reflected light from the incident side optical surface with respect to the incident light irradiated on the incident side optical surface An optical switching element obtained by changing the light intensity. Position-fixed transmission-side optical surface, lower-stage displacement optical surface displaced by the displacement means, position-fixed common intermediate optical surface, upper-stage displacement optical surface displaced by the displacement means, and position-fixed incident-side optical surface Are arranged in the order described, the optical path A between the transmission side optical surface and the lower displacement optical surface, the optical path B between the lower displacement optical surface and the common intermediate optical surface, and the common intermediate An optical path C between the optical surface and the upper displacement optical surface and an optical path D between the upper displacement optical surface and the incident side optical surface are formed, and the lower displacement optical surface and the upper displacement are formed by the displacement means. By displacing one or both of the optical surfaces, the length of the light path A and the light path B is increased or decreased in a reciprocal relationship to change the light interference action of the light path A and the light path B, and the light path C And the length of the optical path D is increased or decreased in a reciprocal relationship, and the optical path C and An optical switching element that changes the light intensity of the transmitted light from the transmission side optical surface or the reflected light from the incident side optical surface with respect to the incident light irradiated on the incident side optical surface by changing the interference action of the light of the path D . A position-fixed transmission-side optical surface, a lower-stage displacement optical surface displaced by the displacement means, a position-fixed common intermediate optical surface, and an upper-stage displacement optical surface displaced by the displacement means, arranged in the order described above, The optical path A between the transmission side optical surface and the lower displacement optical surface, the optical path B between the lower displacement optical surface and the common intermediate optical surface, and the common intermediate optical surface and the upper displacement optical surface. And the length of the optical path A and the optical path B are increased or decreased in a reciprocal relationship by displacing one or both of the lower optical displacement surface and the upper optical displacement surface by the displacement means. To change the light interference action of the light path A and the light path B, and increase or decrease the length of the light path C to change the light interference action of the light path C, so that the upper displacement optical surface The transmitted light from the optical surface on the transmission side or the upper stage Optical switching element comprising varying the light intensity of the reflected light from the optical surface. 5. The optical switching element according to claim 1, wherein the displacement optical surface is displaced by an electrostatic force applied to the displacement optical surface by an electric field generated according to an electric signal applied from outside. The displacement optical surface is displaced integrally with the auxiliary displacement surface by an electrostatic force applied to an auxiliary displacement surface formed integrally with the displacement optical surface by an electric field generated according to an electric signal applied from the outside. 4. The optical switching element according to any one of 4 above. The optical switching element according to claim 1, wherein a displacement limiting stopper for limiting a displacement amount of the displacement optical surface is attached to the displacement optical surface. 8. The optical switching element according to claim 7, wherein the displacement limiting stopper is a stopper transmission surface on which the displaced displacement optical surface comes into contact. 8. The optical switching element according to claim 7, wherein a light-shielding surface having a transmission window that is equal to or smaller than a range in which the displaced displacement optical surface is in contact with the stopper transmission surface is disposed in parallel with the displacement optical surface. Pixel units consisting of optical switching elements that change the light intensity of transmitted light or reflected light with respect to incident light from a light source are arranged one-dimensionally or two-dimensionally, and an image is displayed on the display surface by turning on or off each pixel unit. In the image display device, the optical switching element includes a transmission-side optical surface having a fixed position, a displacement optical surface that is displaced by a displacement means, and a light-incident-side optical surface that is fixed in position, in the order described, and the transmission-side optical surface. And an optical path A between the displacement optical surface and an optical path B between the displacement optical surface and the incident-side optical surface. By displacing the displacement optical surface by the displacement means, the optical path A and the optical path The length of B is increased / decreased in a reciprocal relationship to change the light interference action of the light path A and the light path B, and the transmitted light from the transmission side optical surface or the incident side with respect to the incident light irradiated on the incident side optical surface Reflected light from optical surface An image display device using the optical switching element, characterized in that to vary the light intensity. 11. The image display device using an optical switching element according to claim 10, wherein the optical switching element is provided with a displacement limiting stopper for limiting a displacement amount of the displacement optical surface with respect to the displacement optical surface. 12. The image display device using an optical switching element according to claim 11, wherein the displacement limiting stopper is a stopper transmission surface on which the displaced optical displacement surface comes into contact. 8. The optical switching element according to claim 7, wherein the optical switching element is provided with a light-shielding surface having a transmission window that is less than or equal to a range where the displaced displacement optical surface is in contact with the stopper transmission surface parallel to the displacement optical surface. Image display device. 11. The image display using an optical switching element according to claim 10, wherein the optical switching element displaces the displacing optical surface by using an electrostatic force applied to the displacing optical surface by an electric field generated according to an electric signal applied from the outside as a displacing means. apparatus. The optical switching element integrates the displacement optical surface with the auxiliary displacement surface using an electrostatic force applied to an auxiliary displacement surface formed integrally with the displacement optical surface by an electric field generated in response to an externally applied electric signal. 11. An image display device using the optical switching element according to claim 10. The optical switching element is configured to apply an electric signal with a unit application time obtained by dividing a unit lighting time in pixel units, and increase or decrease the number of times the electric signal is applied within a range in which the total of the unit application time does not exceed the unit lighting time. 16. The image display device using the optical switching element according to claim 14, wherein the color development and the light intensity of the pixel unit are adjusted by: The optical switching element is configured to apply an electric signal with a continuous application time equal to or less than a unit lighting time of a pixel unit, and by increasing or decreasing the continuous application time of the electric signal within a range not exceeding the unit lighting time, 16. An image display device using the optical switching element according to claim 14, wherein color development and light intensity are adjusted. The pixel unit is a total of 3 each of a red switching element, a green switching element, and a blue switching element in which different lengths of light paths A and B are set corresponding to red light, green light, and blue light. A group is configured as a set, and visible light of three wavelengths corresponding to red light, green light, and blue light is input as incident light from the light source to the pixel unit, and transmitted from each optical switching element constituting the pixel unit. An image is displayed on the display surface by light or reflected light, and the color of each pixel on the display surface is changed by individually changing the light intensity of transmitted light or reflected light of each light switching element constituting each pixel unit. 11. An image display device using the optical switching element according to claim 10, which is displayed. 19. The image display device using an optical switching element according to claim 18, wherein the light source is a visible light emitting diode or a laser diode. The display surface displays an image by lighting a plurality of scanning lines in the scanning order. The unit of pixels arranged along the scanning lines is a scanning unit, and incident light is input from the light source only to the scanning units that are lit according to the scanning order. 20. The image display device using an optical switching element according to claim 18, wherein incident light is not input from the light source to the remaining scanning units not in the scanning order. The pixel unit is composed of at least three switching elements for ultraviolet light in which the length of the incident side spacer surface is set corresponding to the ultraviolet light, and the pixel unit uses the single wavelength ultraviolet light from the light source as incident light. The red fluorescent screen, the green fluorescent screen, or the blue fluorescent screen that emits light by receiving transmitted light or reflected light from each optical switching element constituting the pixel unit is used as each optical switching element in the pixel unit. The image is displayed on the corresponding display surface, and the color of each pixel on the display surface is changed by individually changing the light intensity of transmitted light or reflected light of each optical switching element constituting each pixel unit. 11. An image display device using the optical switching element according to claim 10, which is displayed. 22. The image display device using an optical switching element according to claim 21, wherein the light source is an ultraviolet light emitting diode or a laser diode. The display surface displays an image by lighting a plurality of scanning lines in the scanning order. The unit of pixels arranged along the scanning lines is a scanning unit, and incident light is input from the light source only to the scanning units that are lit according to the scanning order. 23. The image display device using an optical switching element according to claim 21, wherein incident light is not input from the light source to the remaining scanning units not in the scanning order.