JP3658965B2 - Optical switching element and image display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical switching element (light valve) used for optical communication, optical computation, an optical storage device, an optical printer, an image display device, and the like, and more particularly to an optical switching element and an image display suitable for an image display device. It relates to the device.
[0002]
[Prior art]
Conventional optical switching elements using liquid crystals are known. As shown schematically in FIG. 12, the conventional optical switching element 900 is composed of polarizing plates 901 and 908, glass plates 902 and 903, transparent electrodes 904 and 905, and liquid crystals 906 and 907, with a voltage between the transparent electrodes. Was applied to change the direction of the liquid crystal molecules and rotate the polarization plane to perform optical switching. The conventional image display device uses a liquid crystal panel in which such optical switching elements (liquid crystal cells) are arranged two-dimensionally, and gradation expression controls the direction of liquid crystal molecules by adjusting the applied voltage. Met.
[0003]
[Problems to be solved by the invention]
However, the liquid crystal has poor high-speed response characteristics and operates only at a response speed of about several milliseconds. For this reason, it has been difficult to apply an optical switching element using liquid crystal to optical communication, optical computation, an optical storage device such as a hologram memory, an optical printer, or the like that requires a high-speed response. Moreover, in the optical switching element using a liquid crystal, there also existed a problem that the utilization efficiency of light fell with a polarizing plate.
[0004]
Further, in recent years, image display devices have been required to have higher quality image quality, and there is a demand for an optical switching element that can perform display with more accurate gradation expression than an optical switching element using liquid crystal.
[0005]
SUMMARY OF THE INVENTION An object of the present invention is to provide an optical switching element that is capable of high-speed response with little loss of light. It is another object of the present invention to provide an optical switching element that can provide uniform contrast and display with good image quality.
[0006]
[Means for Solving the Problems]
For this reason, in the present invention, the evanescent light is extracted by bringing the light-transmitting extraction surface of the optical switching unit into contact with the light guide unit capable of totally reflecting and transmitting the light, and about one wavelength of the optical switching unit or Using an optical switching element capable of controlling light on and off at a high speed by a minute movement below that, and further making the optical switching unit a reflection type, a light guide unit, an optical switching unit, and a drive unit for driving the optical switching unit Are arranged in this order from the light irradiation direction so that a hierarchical structure can be formed. In addition, an optical switching element is realized that has a large amount of emitted light, little loss of the emitted light, and is capable of high-speed response. That is, the optical switching element according to the present invention includes a light guide unit including a total reflection surface capable of transmitting light by total reflection, and a first position approaching the extraction distance or less where evanescent light leaks from the total reflection surface. And an optical switching unit that includes a translucent extraction surface that can move to a second position that is more than the extraction distance, and that reflects the extracted light toward the light guide unit, and a drive unit that drives the optical switching unit The light guide unit, the optical switching unit, and the drive unit are stacked in this order with respect to the light emission direction.
[0007]
The optical switching element of the present invention has a function of each part of the light guide unit, the optical switching unit, and the drive unit by stacking the light guide unit, the optical switching unit, and the drive unit thereof. It is possible to make a hierarchical structure in which almost independent layered parts are stacked. Therefore, it is easy to optimize each part. In particular, in the optical switching element of the present invention, light is reflected by the optical switching unit toward the light guide unit, and the drive unit does not transmit light. Therefore, the drive unit can be optimized without taking optical considerations into consideration. For example, by supporting the optical switching unit from the drive unit side, the light guide unit is arranged on the optical switching unit side. Can be a flat panel structure. In addition, if the light guide part is a flat surface and a portion that supports the light switching part is not provided, most of the area of the light guide part can be used as a surface from which light is extracted. Therefore, an optical switching element with a large aperture ratio and a large light amount can be realized. Furthermore, the drive unit can be formed on an IC substrate that controls the drive unit, and an optical switching element integrated with an IC chip for screen control can be realized.
[0008]
Such an optical switching element of the present invention has a single pixel, a plurality of optical switching elements are two-dimensionally arranged, and the light guide unit is connected so that light of white or three primary colors can be transmitted. An image display apparatus can be configured, and an image display apparatus capable of displaying an image with high resolution at high speed can be provided at a low cost by forming a hierarchical structure. Of course, an image display device integrated with an IC chip can be realized.
[0009]
In order to obtain a reflection-type optical switching unit, a microprism that reflects the light extracted by the extraction surface or a light scattering material can be used as the emitting body that emits the extracted light. Can be controlled to approach the vertical direction with respect to the total reflection surface of the light guide.
[0010]
The drive unit is provided with an elastic body capable of pressing the optical switching unit toward the light guide unit at the first position when no driving force is applied, and the optical switching unit is opposed to the elastic force of the elastic body. It is desirable to provide a first driving force generator that can move using electric power at the second position. The first driving force generator that is controlled using electric power is easy to control, but the driving force changes as the voltage or current fluctuates. On the other hand, the driving force using the elastic body is mechanical and stable. Accordingly, it is possible to employ a driving means using a stable elastic body as a driving force for bringing the extraction surface of the optical switching unit closer to the total reflection surface of the light guide unit and turning on the optical switching unit. Furthermore, by adopting driving means that uses electric power that is easy to control as the driving force to turn off the light by opening an appropriate distance, a stable light quantity can be secured and an optical switching element with high control capability is provided. can do.
[0011]
The elastic body is desirably set so that a bent state remains when the optical switching unit is in the first position. By leaving the bent state, in the on state, the extraction surface is pressed against the total reflection surface of the light guide by the elastic body, so the extraction surface is in close contact with the total reflection surface, and when it is on, It is possible to provide an optical switching element that is bright and has high on / off contrast. Also, by giving the elastic body bending, it is possible to absorb changes such as the distance between the light guide section and the optical switching section or the distance between the optical switching section and the drive section due to vibration, temperature change or other changes over time. It becomes.
[0012]
Further, as the drive unit, a second drive generation unit that can move or hold the optical switching unit to the second position using electric power can be provided. By providing the first drive generation unit and the second drive generation unit in addition to the elastic body, the optical switching unit can be stably held at the first and second positions. A highly functional optical switching element can be provided.
[0013]
By providing a driving electrode in the driving force generating unit, the optical switching unit can be moved by electrostatic force, and the driving force generating unit can obtain a sufficient driving force with high reliability with a simple configuration.
[0014]
Furthermore, a first drive electrode that moves together with the optical switching unit and a second drive electrode installed on the substrate are provided, and a first space in which the distance between the first and second drive electrodes is further reduced. And a spacer that forms a second space in which the distance between the substrate and the optical switching unit is increased so that the spring member can be accommodated, such as a T-shaped or inverted trapezoidal section when the drive unit is viewed from below It is desirable to provide a spacer. In the driving unit, by applying a voltage to the driving electrode in the narrow first space, the optical switching unit can be turned on and off via the spacer, so that the driving voltage can be lowered and high-speed operation can be achieved. It becomes possible. On the other hand, since the spring member, which is an elastic body, can be accommodated in the wide second space, the effective length can be increased, and the force for pressing the optical switching unit can be adjusted. Therefore, even if the driving force by the driving electrode is small, it can be adjusted so as to obtain an elastic force capable of reliably performing the on / off operation. Also, by adopting a T-shaped or inverted trapezoidal spacer, the effective length of the spring member can be secured without dividing the area of the optical switching portion, so that the aperture ratio through which light is emitted is high and the image display device is configured. Thus, it is possible to provide a seamless optical switching element in which adjacent optical switching elements are almost connected to each other.
[0015]
As a spring member that exhibits a function as an elastic body of the drive unit, an arbitrary shape such as a coil spring can be used. However, the spring member employs a plate-like spring in which one end is supported by the support portion in the vicinity of the boundary of the optical switching unit (element) and the other end is connected to the optical switching unit. Positioning can be performed. At this time, by adopting a plate-like spring in which a slit or a hole is formed in the vicinity of the boundary, the spring member can prevent the influence on the adjacent optical switching unit, and the elastic coefficient of the spring member can be changed to the optical switching unit. Can be set to an appropriate value for driving. For example, such a plate-like spring is a narrow spring member having one end connected to a support provided near the boundary and extending radially from the optical switching unit. With respect to such a spring member, the electrode area can be increased by making the first driving electrode radially extend from the optical switching portion, so that a high driving force can be obtained at a low voltage, and the driving voltage can be reduced. Can be lowered. Further, since the spring member is a plate-like spring having a spiral portion extending along the boundary, the effective length of the spring can be increased without increasing the area, so that the optical switching unit is driven. The voltage can be lowered and the power consumption can be reduced. Furthermore, a double helix structure can also be used. In addition, it is possible to obtain the same effect as increasing the effective length of the spring by reducing the elastic coefficient by making the bent portion of the spring (intermediate portion of both fulcrums) thinner than the other portions. Such support portions of the leaf springs are regularly arranged in the vicinity of the boundary, and can be configured to be shared with adjacent switching elements when an image display device is configured using a plurality of optical switching elements. The support portion may be a projection that extends long along the boundary between the optical switching elements, but the space occupied by the support portion is reduced by adopting struts that exist intermittently along the boundary. And that space can be used as an electrode or other space. In addition, the support columns can be randomly arranged, but by arranging them according to a predetermined rule, it is possible to provide an optical switching element and an image display device that can be easily assembled by symmetry and have stable performance.
[0016]
As the spring member, a conductive thin film member such as a boron-doped silicon thin film can be employed, and a structure that also serves as a driving electrode can be employed. Therefore, the region facing the second driving electrode on the substrate side can function as the first driving electrode, and the other portion can function as the spring member.
[0017]
On the other hand, an auxiliary support portion is provided between the light guide portion and the spring member, and further, a plate-like spring that can substantially seal the optical switching portion side without providing the above-mentioned slit or hole in the spring member. Thus, the optical switching unit side can be set to a negative pressure from the driving unit side. Accordingly, the spring member is pressed against the auxiliary support portion by the external air pressure, and the gap with the optical switching portion can be kept uniform. In addition, the optical switching unit is in close contact with the light guide unit when turned on due to the pressure difference. Therefore, a stable operation is performed and an optical switching element with high contrast can be provided.
[0018]
In addition, the space having the drive unit and the optical switching unit, that is, the space inside the optical switching element is sealed, and the internal pressure is lowered, or a gas such as an inert gas is replaced with air. If the pressure of the gas is lowered, the flow resistance of the gas during the switching operation can be lowered, so that friction such as a damper effect due to the gas does not occur, the driving voltage is lowered, the driving speed is increased, and the on / off switching is performed at high speed. it can. Therefore, it is possible to provide an optical switching element capable of high-speed response.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
[First Embodiment]
FIG. 1 shows a schematic configuration of an image display device 2 using a plurality of optical switching elements 1 of the present invention. The switching element 1 of this example includes a light guide 20 that serves as a light guide having high light transmittance, such as glass or transparent plastic. The light guide 20 is formed with a total reflection surface 22 having an appropriate angle with respect to the incident angle of the incident light 10 so that the incident light 10 is transmitted by total reflection.
[0020]
The switching element 1 of this example includes a layer of an optical switching unit 30 that extracts light from the light guide unit 20 and reflects it upward below the light guide unit 20 (total reflection surface 22 side). The layer of the drive unit 40 that moves the drive unit 30 and the layer of the silicon substrate 70 on which the drive IC that controls the drive unit 40 is configured are sequentially stacked, and each functional part has a hierarchical structure.
[0021]
The optical switching unit 30 includes a microprism 34 that has a flat extraction surface 32 on the side of the total reflection surface 22 of the light guide unit that can be substantially in close contact with the total reflection surface 22 as an emitter. The microprism 34 of this example is a triangular prism having the extraction surface 32 as a bottom surface, and reflects light extracted from the total reflection surface 22 in a direction substantially perpendicular to the total reflection surface 22 to guide the light guide 20. The light can be emitted from the projection surface 21 opposite to the total reflection surface 22.
[0022]
In order to drive the optical switching unit 30, the driving unit 40 provided in the lower layer of the optical switching unit 30 includes a spacer 42 having a substantially T-shaped cross section for supporting the microprism 34, and the spacer 42. A plate-like spring member 50 that is an elastic body capable of pressing the light extraction unit 32 toward the light guide unit 20 at a first position where the extraction surface 32 of the light switching unit 30 is in contact with the total reflection surface 22 of the light guide unit 20; Is used to move the extraction surface 32 to a second position away from the total reflection surface 22 (first power generation unit). Therefore, in the optical switching element 1 of the present example, when power is not supplied to the drive unit 20, the extraction surface 32 approaches the first reflection surface 22 by the spring member 50 (first position), and the light guide unit 20 Light is extracted and emitted from the projection surface 21 (ON state). On the other hand, when electric power is supplied to the drive unit 20, the electrodes 60 and 62 are separated (second position), so that light is not extracted and emitted from the light guide unit 20 (off state).
[0023]
Further, in the image display device 2 of this example, the optical switching element 1 having such a configuration is two-dimensionally arranged in a direction perpendicular to the paper surface as in the horizontal direction of FIG. Can display an image as one pixel.
[0024]
The image display device 2 is formed on the surface of a silicon substrate 70 on which a circuit for controlling the drive unit 40 is configured, and the image display device 2 integrated with the image driving IC 70 is realized. .
[0025]
FIG. 2 shows the optical switching element 1 in an enlarged manner with the optical switching unit 30 as the center. The left optical switching element 1a shown in the figure shows an on state, and the right optical switching element 1b shows an off state. The optical switching element 1 of this example is an element that captures an evanescent wave leaking from the total reflection surface 22 of the light guide 20 by the extraction surface 32 and can use it for image formation and the like.
[0026]
FIG. 3 shows some examples of evanescent wave transmittance. When the transparent body is brought close to the totally reflected surface, the evanescent wave leaks out to the transparent body side, and light is transmitted. The transmittance of the evanescent wave varies depending on the refractive index of the medium, the incident angle, and the like. As shown in FIG. 3, the transmittance (%) of the evanescent wave when the incident angle is 50 ° with respect to light having a wavelength λ of 500 nm. Is a transmission curve 14 measured with respect to the distance (μm) between the total reflection surface 22 and the extraction surface (transparent body) 32. Similarly, a characteristic curve 15 at an incident angle of 60 °, a characteristic curve 16 at an incident angle of 70 °, and a characteristic curve 17 at an incident angle of 80 ° are also shown. These characteristic curves show almost the same tendency. When the extraction surface 32 approaches 0.1 to 0.05 μm or less from the total reflection surface 22 (first position), the transmittance becomes about 50%. . On the other hand, when the extraction surface 32 is separated from the total reflection surface 22 by 0.2 μm or more (second position), the transmittance becomes 10% or less. Further, when the distance of the extraction surface 32 exceeds 0.3 μm, the transmittance is It becomes almost 0%. Therefore, in the ON state indicated by the optical switching element 1a in FIG. 2 and the OFF state indicated by the optical switching element 1b, it is only necessary to move the optical switching unit 32 by about 0.2 to 0.3 μm. For this reason, by using the optical switching element 1 of this example, pixels can be controlled at high speed, and an image with high contrast can be obtained. Further, since the moving distance of the optical switching unit 32 can be shortened, the distance between the drive electrodes 60 and 62 is also shortened. Therefore, the drive voltage for generating an electrostatic force by these electrodes may be small, and the image display apparatus 2 with low power consumption can be provided.
[0027]
Based on FIG. 2, the structure of the optical switching element 1 of this example is demonstrated in more detail. In the optical switching element 1 of this example, as shown in the optical switching element 1 a, the spacer 42 is pushed up by the spring member 50 provided in the driving unit 40, and the extraction surface 32 of the optical switching unit 30 is in relation to the total reflection surface 22. The evanescent wave can be captured by being in close contact with each other as described above. The captured evanescent wave 10 is reflected by the reflecting surface 34a of the prism 34, which is an emitting body, and is emitted from the light guide 20 to the outside. On the other hand, as shown in the optical switching element 1b, the prism 34 moves downward against the spring 50 due to the electrostatic force of the electrodes 60 and 62, and the interval as described above is opened between the extraction surface 32 and the total reflection surface 22. Then, the evanescent wave cannot be captured by the prism 34.
[0028]
The spacer 42 of this example that supports the prism 34 has a substantially T-shaped cross section, and the center is a first space 45 in which the gap between the surface 71 of the substrate 70 and the lower surface 42a of the spacer 42 is narrowed. Both sides are second spaces 46 in which a gap between the surface 71 of the substrate and the lower surface 42b of the spacer 42 is widened. Electrodes 62 and 60 are provided on the lower surface 42a of the spacer 42 and the surface 71 of the substrate so as to sandwich the first space 45 having a narrow gap. On the other hand, a spring member 50 is provided in the second space 46 having a large interval, and the spring member 50 connects the support column 44 provided at the boundary of the switching element 1 and the spacer 42, so that the optical switching unit 30. The position of the microprism 34 is determined. Further, as shown in the optical switching elements 1a and 1b, the plate-like spring member 50 can be deformed in the second space 46 formed by the T-shaped spacer 42, and the distance between the electrodes 60 and 62 ( The installation space for the spring member 50 can be secured without opening the first space. Therefore, since the drive voltage supplied to the electrodes 60 and 62 may be low, power consumption can be suppressed as described above.
[0029]
Further, by adopting the T-shaped spacer 42, the space 46 located in the layer of the drive unit 40 below the prism 34 can be used as the installation space for the spring member 50. Thus, by processing the spring member 50 that is a member of the drive unit 40 in the layer of the drive unit 40, the spring member 50 is interposed between the adjacent optical switching elements 1a and 1b in the layer of the optical switching unit 30. No space is required to install Therefore, the area of the prism 34 can be increased, the area ratio (aperture ratio) from which light can be extracted from the light guide unit 20 can be increased, and a bright optical switching element with a large amount of emitted light can be provided.
[0030]
Furthermore, in the optical switching element 1 of this example, the support 44 is provided in the layer of the drive unit 40 so that the drive unit 40 can support the optical switching unit 30, and the light guide unit 20 supports the prism 34. There is no need to form by etching or the like. Therefore, the total reflection surface 22 of the light guide 20 is a flat surface with respect to the plurality of optical switching elements 1, and a simple member can be adopted as the light guide 20. Since a space for installing the spring member 50 can also be provided in the drive unit 40, the optical switching unit 30 can be arranged with almost no gap between the optical switching elements 1a and 1b. Therefore, by using the optical switching element of this example, it is possible to provide an image display device 2 that can form a seamless or nearly seamless image in which the pixels are hardly opened, the boundary between the pixels is not known.
[0031]
Further, in the optical switching element 1 of the present example, as shown in the optical switching element 1a, the extraction surface 32 of the microprism 34 is moved by the force of the spring member 50 without using the electrostatic force in the ON state. The light is pressed against the reflecting surface 22. In the ON state, the spring member 50 is further given a slight displacement 51 so that the prism 34 can be pressed against the total reflection surface 22. The electrostatic force controlled using electric power is easy to control, but when the supply voltage varies, the force pressing the extraction surface 32 against the total reflection surface 22 changes. As shown in FIG. 3, when the voltage drops and the pressure is insufficient, and the gap between the extraction surface 32 and the total reflection surface 22 is about 0.1 to 0.15 μm, the transmission amount is about 20% or less, On-off contrast is reduced. On the other hand, the force obtained by the spring member 50 is mechanical and stable regardless of voltage fluctuation. Therefore, in the switching element 1 of this example, the stable force of the spring member 50 is used as the driving force for turning on, while the electrostatic force that is easy to control is used as the driving force for turning off. In addition to ensuring the amount of light, an optical switching element with high control capability can be provided.
[0032]
Furthermore, by providing the spring member 50 in the ON state with the displacement (deflection) 51, the extraction surface 32 can be pressed against the total reflection surface 22 with an appropriate force. Therefore, even if the distance between the light guide unit and the optical switching unit or the interval between the optical switching unit and the drive unit due to vibration, temperature change or other changes over time is changed, it is absorbed and the on / off contrast is reduced. Can be prevented. Further, in the switching element 1 of this example, since the wide space 46 is secured as the installation space of the spring member 50 by the T-shaped spacer 42 as described above, the spring member 50 can be displaced inside. Is possible. The degree of the bending 51 is preferably smaller than the off-state interval, that is, about 0.1 to 0.2 μm.
[0033]
Furthermore, the spring member 50 of this example is formed of a boron-doped silicon thin film 49 and is conductive. Accordingly, the thin film 49 can function as the spring member 50 in the wide space 46 region, and the thin film 49 can be fixed to the spacer 42 and function as the electrode 62 in the narrow space 45 region.
[0034]
It is important that the spring member 50 provided in the drive unit 40 has an appropriate elastic coefficient. If the elastic modulus is too high, a very strong force is required to move even at short intervals, and a large electrostatic force is required, so that the drive voltage becomes high. On the other hand, if the elastic coefficient is too low, the force for pressing the extraction surface 32 of the prism 34 against the total reflection surface 22 cannot be obtained. The size of the optical switching element 1 that is used in the image display device 2 and constitutes a pixel is from several tens of microns to several hundreds of microns. In such a micromachine, the effective length of the spring member 50 is increased to be elastic. It is important to keep the coefficient low. For this reason, in the optical switching element 1 of this example, the spring member 50 is arranged in the wide space 46 secured by using the T-shaped spacer 42 to increase the effective length and further reduce the spring member 50. The effective length is increased.
[0035]
FIG. 4 shows a state where the arrangement of the drive unit 40 of the optical switching element 1 of this example is viewed from the bottom surface (the substrate 70 side). The silicon thin film 49 forms a spring member 50 (shown by a vertical line for the sake of clarity) that extends radially from the four pillars 44 toward the bottom surface 42a of the spacer 42, A hole 52 is formed by largely cutting the periphery of the support pillar 44 that is the boundary of the. Further, the silicon thin film 49 remaining on the bottom surface 42a forms a substantially rectangular electrode 62 (shown by hatching for the sake of clarity). Thus, by forming the narrow plate-like spring member 50, the effective length can be increased and the drive voltage can be lowered. Further, in the image display device, since the connection portion between the adjacent optical switching elements becomes thin, it is possible to prevent the on / off state from affecting each other between the pixels constituted by the optical switching elements.
[0036]
FIG. 5 shows an example of a spring member 50 different from the above in this example. In this example, slits 53 are formed radially in the silicon thin film 49 so as to extend in the direction from the spacers 42 to the pillars 44 to form the elongated spring members 50, and the electrodes 62 attached to the bottom surface 42 a of the spacers 42 are radial. The electrode 62a is further widened to ensure a large electrode area. In this manner, by increasing the area of the electrode 62, it is possible to reduce the drive voltage applied to drive the optical switching unit 30.
[0037]
FIG. 6 shows an example of a spring member 50 further different from the above. FIG. 6A and FIG. 6B show a state in which four optical switching elements 1 among a plurality of optical switching elements 1 arranged two-dimensionally to constitute an image display device are arranged. A state seen from the side of the silicon substrate 70 is shown. In this example, a slit 53 is formed in the silicon thin film 49 in a direction along the boundary of each optical switching element 1, and a spring extending spirally around the spacer 42, that is, along the boundary of the optical switching element 1. The member 50 is configured. Thus, by extending the spring member 50 in the direction along the boundary, the effective length of the spring member 50 can be further increased. On the other hand, the bottom surface 42a of the spacer 42 is widened to increase the area of the electrode 62. Can be secured. Therefore, the driving voltage can be greatly reduced by these effects. FIG. 6B is an example in which the slit 53 is further lengthened so that a longer length can be secured until the spring member 50 reaches two sides along the boundary of the switching element 1. The effective length can be further increased, and the drive voltage can be lowered. Of course, the slit 53 can be further elongated to form the spring member 50 having a long effective length along the boundary.
[0038]
FIG. 7 shows still another example of the spring member. In this example, compared with the portion where the spring member 50 is in contact with the spacer 42 or the portion where the spring member 50 is connected to the support column 44, the thickness of the central portion 55 is reduced to reduce the elastic coefficient so that the drive voltage can be reduced. Yes. As described above, the elastic coefficient of the spring member 50 can be lowered by combining some examples shown above or a combination thereof. Therefore, the electrostatic force is applied to the electrodes 60 and 62 in order to move the optical switching unit 30. The drive voltage generated can be reduced. Therefore, it is possible to provide the optical switching element 1 that can be operated with low electricity consumption, and it is possible to suppress the entire power of the image display device 2.
[0039]
The optical switching element 1 of this example employs a structure in which the light guide unit 20, the optical switching unit 30, and the driving unit 40 are sequentially stacked, and the reflection type optical switching unit 30 is used, so that the emission direction is stacked. It is possible to provide an optical switching element having a configuration in which the light extracted from the driving unit 40 does not pass. Therefore, since the drive unit 40 can be designed without considering optical characteristics, the configuration for supporting and driving the optical switching unit 30 can be optimized to be realized by the drive unit 40 as described above. The configurations of the optical switching unit 30 and the light guide unit 20 can be greatly simplified. In addition, the light guide 20, the optical switching unit 30, and the drive unit 40 can be independently designed with a layer structure, and the light guide 20 can use a flat plate member with a flat total reflection surface 22. Further, the light switching unit 30 can use an emitting body 34 such as a prism having a wide extraction surface 32. Further, the drive unit 40 can employ a highly reliable mechanism that can stably perform the on / off operation at high speed. Therefore, according to the present invention, an optical switching element with a large amount of light and a small loss of light can be provided, and an optical switching element with high on-off contrast and good image quality can be provided.
[0040]
Furthermore, in the optical switching element 1 of this example, the drive unit 40 is manufactured on a silicon IC substrate on which a drive circuit or the like is configured, using a semiconductor manufacturing technique or micromachine manufacturing technique suitable for fine processing such as etching. It is easy to integrate a plurality of optical switching elements 1 at a high density. Therefore, by using the optical switching element of the present invention, it is possible to provide a thin and high-resolution image display device 2.
[0041]
FIG. 8 shows a projection device 6 using the image display device 2 according to the present invention. In the projection device 6 of this example, the IC chip 5 on which the optical switching unit 30 and the drive unit 40 are mounted together with the drive circuit is attached to the total reflection surface 22 of the light guide unit 2. The light guide unit 20 of the image display device 2 is provided with an incident surface 81 on one side, and three primary colors of light such as red, green, blue (RGB) or cyan, magenta, and yellow from the light source toward the surface. Is incident in a time division manner. The light source 80 of this example includes a white metal halide lamp 80a and a three-color division filter 80b that is rotated by a motor. Light beams that have been color-divided by the three-color division filter 80b are converted into parallel beams through a collimator lens 80c. Then, the light enters the light guide unit 20 from the incident surface 81. Then, the incident light 10 that has reached the total reflection surface 22 is reflected by the individual optical switching elements configured using the IC chip 5 and is emitted as the emitted light 12 that passes through the light guide 20, and is then projected onto the projection lens. A desired image is formed by projecting on a screen or the like through 85. On the other hand, the incident light 10 that has not been converted into outgoing light by the optical switching element reaches the reflecting surface 82 opposite to the incident surface 81 of the light guide unit 20 by total reflection, is reflected by this surface, and is again guided to the light guide unit. 20 is transmitted and reaches the optical switching element.
[0042]
As described above, the image display device 2 of the present example can project a color image by operating the optical switching element constituted by the IC chip 5 in time division and in synchronization with the incident light. Of course, it is also possible to project a color image using an optical switching element that employs white light as the incident light 10 and uses a wavelength selective light extraction unit.
[0043]
[Second Embodiment]
FIG. 9 shows an example of an optical switching element different from the above. The optical switching element 1 of this example also has a hierarchical structure in which the light guide unit 20, the reflection type optical switching unit 30, and the drive unit 40 are stacked in this order with respect to the direction of the emitted light 12. Portions common to the examples are denoted by the same reference numerals and description thereof is omitted. In the optical switching element 1 of this example, as the driving unit 40 of the optical switching unit 30, in addition to the set of driving electrodes 60 and 62 (first driving unit), the optical switching unit 30 is newly set upward, that is, in the on state. A set of drive electrodes 64 and 66 to be pulled up (second drive unit) is provided. In this example, a substantially U-shaped notch 38 is formed in a symmetrical position on the side surface of the buffer member 35 that supports the prism 34 from the spacer 42, and an auxiliary column 47 extending from the column 44 is provided in the space 38. The second drive unit is formed by inserting and fixing new electrodes 64 and 66 to the space 48 and the auxiliary column 47, respectively. In the optical switching element 1 of the present example, in addition to the first set of electrodes 60 and 62 that control the off state using electric power, the on state of the electrodes 64 and 66 that can also control the on state using electric power (electrostatic force). A second set is provided. For this reason, since both on / off states can be controlled using electric power in addition to the driving force of the spring member 50, more stable driving control is possible, and the optical switching element 1 with higher reliability is provided. can do.
[0044]
[Third Embodiment]
FIG. 10 shows different examples of the optical switching element according to the present invention. In the optical switching element 1, the light guide unit 20, the optical switching unit 30, and the driving unit 40 are laminated on the base of the IC unit 70 in this order, and the same reference numerals are given to the parts common to the above-described embodiment. Therefore, the description is omitted. In the optical switching element 1 of this example, the thin film 49 that is installed so as to serve as the spring member 50 and the electrode 62 and connect the support column 44 and the spacer 42 is supported by the auxiliary column 48 with respect to the light guide unit 20. The distance between the extraction surface 32 and the total reflection surface 22 is kept substantially uniform between the optical switching elements 1. Further, no hole or slit is formed in the thin film 49, and the layer of the optical switching unit 30 can be sealed with the thin film 49 and the light guide unit 20. And the pressure of the optical switching part 30 is adjusted so that it may become a negative pressure with respect to external air. As a result, the thin film 49 is brought into close contact with the auxiliary column 48, and when the image display device 2 is configured by two-dimensionally arranging the plurality of optical switching elements 1, the distance between the thin film 49 and the total reflection surface 22, that is, the thin film 49 is attached. The gap between the extraction surface 32 of the optical switching unit 30 and the total reflection surface 22 of the light guide unit 20 can be kept substantially uniform. Therefore, a stable switching operation is performed in all the pixels of the image display device 2 configured by the plurality of optical switching elements 1, and a high contrast can be obtained in all the pixels. The auxiliary pillars 48 need not be provided in the switching elements constituting all the pixels, and may of course be arranged at appropriate intervals or randomly.
[0045]
Further, since the pressure is adjusted so that the optical switching unit 30 side has a negative pressure, the extraction surface 32 of the optical switching unit 30 is pressed against the total reflection surface 22 by the external air pressure. Therefore, in the optical switching element 1 of the present example, the extraction surface 32 can be brought into close contact with the total reflection surface 22 using the atmospheric pressure in addition to the force of the spring member 50, and high contrast can be obtained.
[0046]
Further, in the optical switching element 1 of this example, a spacer 42 positioned between the spring member 50 and the prism 34 has an inverted trapezoidal shape instead of the T shape. Thus, even if the inverted trapezoidal spacer 42 is used, it is possible to secure a wide space 46 in which the spring member 50 is disposed and a narrow space 45 in which the electrodes 60 and 62 are disposed.
[0047]
Furthermore, in addition to the optical switching unit 30, the driving unit 40 can be sealed, and the entire region surrounded by the light guide unit 20 and the silicon substrate 70 can be sealed to be a negative pressure. By reducing the pressure in this region, the gas flow resistance disappears when the prism 34, the spring member 50, etc. constituting the optical switching unit 30 and the drive unit 40 move for switching operation, and the resistance due to the damper effect or the like is greatly increased. To drop. Accordingly, it is possible to increase the driving speed during the on / off operation, and the driving force can be reduced. Therefore, it is possible to provide a switching element and an image display device that can operate at high speed and have low power consumption. Moreover, by replacing the sealed space with a gas that does not contain moisture, and by applying a negative pressure from the outside, in addition to the above effects, moisture that causes adsorption and the like can be removed, and an inert gas can be used. If present, alteration such as oxidation can be prevented.
[0048]
[Fourth Embodiment]
FIG. 11 shows another example of the optical switching element of the present invention. Also in the optical switching element 1 of this example, the light guide unit 20, the optical switching unit 30, and the drive unit 40 are laminated in this order on the substrate 70 of the IC unit, and the same parts are common to the above-described embodiment. The reference numerals are attached and the description is omitted. In the optical switching element 1 of this example, the optical switching unit 30 employs a reflection type emitting body 36 including a plurality of reflectors. Therefore, the evanescent light captured by the extraction surface 32 in the ON state is scattered at an appropriate angle by the light emitter 36 toward the light guide unit 20, and an image that can be viewed with a wide viewing angle can be formed.
[0049]
Further, in the optical switching element 1 of the present example, the electrostrictive force generated by the piezo element 69 is used as a drive unit for driving the switching unit 30 instead of the electrostatic force. The piezo element 69 of this example is a bimorph type in which two layers having different polarization directions are laminated. When power is applied, the piezo element 69 extends from a curved state to a linear state and pulls the spring member 50, thereby turning off the optical switching element 1. It is like that. On the other hand, when power is not applied, a curved elastic force is obtained, and the optical switching unit 30 is pressed toward the light guide unit 20 with an appropriate force together with the elastic force of the spring member 50, thereby realizing a high-contrast optical switching element. It can be done.
[0050]
In the optical switching element 1 according to the present invention, since the light guide unit 20, the optical switching unit 30, and the drive unit 40 have a hierarchical structure, the optical switching unit 30 according to each embodiment described above or The optical switching element 1 suitable for the application can be configured by freely combining the drive units 40. The optical switching element of the present invention is not limited to an image display device, and its application range such as a line light valve of an optical printer, an optical spatial modulator for a three-dimensional hologram memory, etc. is very wide, The optical switching element of the present invention is particularly suitable for fields and application devices in which the optical switching element using liquid crystal is of course used, as well as the field where the operation speed and light intensity are insufficient with the optical switching element using liquid crystal. Yes. Furthermore, since the optical switching element of the present invention can be finely processed, it can be made smaller and thinner than conventional liquid crystal optical switching elements, and can be highly integrated.
[0051]
【The invention's effect】
As described above, the optical switching element of the present invention captures the evanescent light leaking from the total reflection surface by contacting the extraction surface with the light guide portion provided with the total reflection surface capable of totally reflecting and transmitting the light. An image can be formed. By laminating a light guide unit, a reflective light switching unit, and a drive unit in this order with respect to the emission direction, the extracted light is directed toward the light guide unit by the light switching unit. It is possible to provide a bright optical switching element that reflects substantially vertically and has no loss of light in the driving unit. Further, by adopting such a laminated structure, it is possible to optimize the layers of the light guide unit, the optical switching unit, and the drive unit, and to freely create layers having different functions or structures. Combinations are also possible. In particular, the optical switching unit is positioned by the drive unit, and the installation space for the spring member, which is an elastic body, is provided to make the light guide unit a flat member and increase the area of the extraction surface of the optical switching unit. be able to. Therefore, it is possible to provide a bright and high-contrast optical switching element having a large aperture ratio, and by using the optical switching element of the present invention, it is possible to provide an image display device capable of obtaining an image with good image quality.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a schematic configuration of an optical switching element according to a first embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view showing the configuration of the optical switching element shown in FIG.
FIG. 3 is a graph showing the evanescent wave transmittance with respect to the distance between the total reflection surface and the extraction surface;
4 is a diagram illustrating a state in which the configuration of a spring member of the optical switching element illustrated in FIG. 1 is viewed from the direction of a substrate.
FIG. 5 is a view showing an example different from the spring member shown in FIG. 4;
FIG. 6 is a view showing an example further different from the spring member shown in FIG. 4;
7 is a view showing an example further different from the spring member shown in FIG. 4;
8 is a diagram showing an example of a projection apparatus using the image display apparatus shown in FIG.
FIG. 9 is a diagram showing a schematic configuration of an optical switching element according to a second embodiment of the present invention.
FIG. 10 is a diagram showing a schematic configuration of an optical switching element according to a third embodiment of the present invention.
FIG. 11 is a diagram showing a schematic configuration of an optical switching element according to a fourth embodiment of the present invention.
FIG. 12 is a diagram showing an optical switching element using a conventional liquid crystal.
[Explanation of symbols]
1. Optical switching element
2. Image display device
6. Projection device
10. Incident light
12. ・ Outgoing light
20. ・ Light guide
22. Total reflection surface
30..Optical switching part
32 .. Extraction surface
34 .. Emitter (prism)
36 .. Emitter (scatterer)
40 ... Driver
42. ・ Spacer
44 ...
45 .. Narrow space for drive electrodes (first space)
46 .. Wide space for spring member (second space)
47, 48 ... Auxiliary pillar
49 .. Silicon thin film
50 .. Spring member
51 .. Deflection of spring member
52 ... Hole
53..Slit
60, 62 .. Driving electrode (first set)
64, 66 .. Driving electrode (second set)
69 .. Piezo element
70 ・ ・ IC part
80 ... Light source
80a ・ ・ Metal Highland Lamp
80b ... 3 color division filter
81 .. Incident surface
82 ... Reflective surface
85 .. Photography lens
90 ... Atmospheric pressure
908 .. Polarizing plate
903..Glass plate
904, 905 ... Transparent electrode
906, 907 ... Liquid crystal

Claims (9)

A light guide unit having a total reflection surface capable of transmitting the light with total reflection;
A translucent extraction surface that is movable to a first position that is less than or equal to an extraction distance at which evanescent light leaks with respect to the total reflection surface, and a second position that is more than or equal to the extraction distance; An optical switching unit that reflects in the direction of the light guide;
A drive unit for driving the optical switching unit,
The light guide unit, the optical switching unit, and the drive unit are stacked in this order with respect to the light emission direction,
The driving unit includes an elastic body capable of pressing the optical switching unit toward the light guide unit at the first position when no driving force is applied, and the light against the elastic force of the elastic body. A first driving force generator capable of moving the switching unit to the second position using electric power,
The optical switching element, wherein the driving force generation unit includes a driving electrode for moving the optical switching unit with electrostatic force.   2. The optical switching element according to claim 1, wherein the light guide unit, the optical switching unit, and the drive unit have a hierarchical structure.   2. The optical switching element according to claim 1, wherein the light guide unit is a panel-like member having a flat surface on the optical switching unit side.   2. The optical switching element according to claim 1, wherein the driving unit is disposed on an IC substrate.   2. The optical switching element according to claim 1, wherein the optical switching unit includes a microprism or a light scattering emitting body that reflects light extracted by the extraction surface.   2. The optical switching element according to claim 1, wherein the elastic body is a spring member that is set so that a bent state remains when the optical switching unit is in the first position.   2. The optical switching element according to claim 1, further comprising a second drive generation unit capable of moving or holding the optical switching unit to the first position using electric power. 7. The driving force generator according to claim 6, wherein the driving force generator includes a first driving electrode that moves together with the optical switching unit to move the optical switching unit with electrostatic force, and a second driving electrode installed on the substrate. In addition,
The drive unit includes a first space in which a distance between the first and second drive electrodes is reduced, and a second space in which a distance between the substrate and the optical switching unit is increased so that the spring member can be accommodated. An optical switching element comprising a spacer for forming   It has two or more optical switching elements of Claim 1, these optical switching elements are arrange | positioned two-dimensionally, and the said light guide part is connected so that the light of white or three primary colors can be transmitted. A characteristic image display device.

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