JP2001318325A - Optical switching unit, optical switching device, light guide, manufacturing method for optical switching unit, and video display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical switching unit which can prevent adsorption while maintaining the extraction rate of evanescent light. SOLUTION: The optical switching unit 55 constituted by combining together a light guide 1 having a total reflecting surface 1a capable of totally reflecting and transmitting incident light 2 and a micro optical element 3 having an extraction surface 3a extracting light 2 from the light guide 1 is provided with multiple dome-shaped fine protrusions 70 of about 1 to 20 nm in height on the extraction surface 3a by irradiation with laser. The adsorbing force is made small by a fine gap formed by the fine protrusions 70 to prevent the adsorption, thereby providing the optical switching unit 55 which can be driven at a high speed with high reliability and small electric power, and can sufficiently extract evanescent light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical switching unit using evanescent light, an optical switching device and an optical guide (light guide) constituting the optical switching unit.

[0002]

2. Description of the Related Art As a light valve of a video display device such as a projector, a liquid crystal device using liquid crystal is known as a light valve capable of controlling on / off of light. However, a video display device using this liquid crystal has a poor high-speed response characteristic and operates only at a response speed of at most several milliseconds. For this reason, devices that display high-resolution images that require high-speed response, as well as optical communication, optical computation,
Optical recording devices and optical printers such as hologram memories
It is difficult to realize with a switching device using liquid crystal.

Therefore, there is a demand for a switching device or a video display device capable of operating at a high speed capable of coping with the above-mentioned applications, and a switching device having a microstructure of a micron order or a smaller submicron order. Development is underway.

[0004]

One of the problems is that the extraction surface of the switching portion is brought closer to the total reflection surface of the light guide portion, which the applicant of the present application is applying for, which can transmit light by total reflection. There is an optical switching device that can control the modulation of light at high speed by a small movement of about one wavelength or less of the optical element.

FIG. 1 schematically shows a projector 80 as an example of an image display apparatus using an optical switching device that performs switching by evanescent light. The projector 80 includes a white light source 81, a rotating color filter 82 that separates light from the white light source 81 into three primary colors and enters the light guide plate (light guide) 1 of the optical switching device 55, and modulates light of each color. The optical switching device 55 includes a light switching device 55 that emits the light 85 and a projection lens 86 that projects the emitted light 85. Then, the modulated light 85 for each color is projected on a screen 89, and the colors are temporally mixed to output a multi-tone multi-color image. The projector 80 further includes a control circuit 84 that controls the optical switching device 55 and the rotating color filter 82 to display a color image. The optical switching device 55 includes the light guide 1 and the optical switching device 50 described in detail below. Data φ and the like for displaying a color image are supplied from the control circuit 84 to the optical switching device 50. .

As described above, the projector 8 shown in FIG.
Reference numeral 0 denotes a light input / output unit that includes a light source 81 that supplies light for projection to the light guide 1 that transmits the light while totally reflecting the light, and a lens 85 that projects the light emitted from the light guide 1 and the like. And an optical switching device 50 for modulating the projection light supplied to the light guide 1. The light switching device 50 controls the evanescent light leaking from the light guide 1 to display an image.

FIG. 2 shows an outline of an image display device (evanescent light switching device) 50 for modulating light using an evanescent wave (evanescent light). The optical switching device 50 is a switching device in which a plurality of optical switching elements (optical switching mechanisms) 10 are two-dimensionally arranged. Each of the optical switching elements 10 can transmit the introduced light 2 by being totally reflected by itself. An optical element (switching unit) 3 capable of modulating light by approaching and separating from a light guide plate (light guide) 1 and an actuator 6 for driving the optical element unit 3 are provided.
The semiconductor substrate 20 on which the driving circuit and the digital storage circuit (storage unit) for driving the actuator 6 are formed by the layer of the optical element 3 and the layer of the actuator 6.
And integrated as one video display device.

Referring to FIG. 2, the optical switching device 50 of this embodiment using evanescent light will be described in more detail. Explaining each optical switching element 10 as a base, the optical switching element 10a shown on the left side of FIG. 2 is in an ON state, and the optical switching element 10b shown on the right side is in an OFF state. The optical element 3 includes a surface (contact surface or extraction surface) 3a that is in close contact with the surface (total reflection surface) 1a of the light guide plate 1 that functions as a waveguide, and this surface 3a.
V-shaped prism (micro-prism 4) for extracting evanescent waves leaked when is adhered to total reflection surface 1a
A reflection film 46 for reflecting the light from the bottom surface of the prism 4 in a direction substantially perpendicular to the light guide plate 1; and a support structure 5 for supporting the V-shaped prism 4.

The actuator 6 is of a type for electrostatically driving the optical element 3. For this purpose, an upper electrode (first electrode) 7 which is mechanically connected to the support structure 5 of the optical element 3 and moves together with the optical element 3. And a lower electrode (second electrode) 8 fixed to the semiconductor substrate 20 at a position facing the upper electrode 7.
It has. Further, the upper electrode 7 is connected to the anchor plate 9
Is supported by a support 11 extending upward from the support.

As shown in FIG. 2, the light guide plate 1 is supplied with the illumination light 2 from the light source at an angle at which the illumination light 2 is totally reflected by the total reflection surface 1a. Light is repeatedly totally reflected on the side 1a facing the light switching portion 3 and on the upper surface (emission surface), and the inside of the light guide plate 1 is filled with light rays. Therefore, in this state, the illumination light 2 is macroscopically confined inside the light guide plate 1 and propagates therein without any loss. On the other hand, microscopically, in the vicinity of the surface 1a of the light guide plate 1 which is totally reflected, the illumination light 2 leaks from the light guide plate 1 only for a very short distance of about the wavelength of light, and changes its course. The phenomenon of returning to the inside of the light guide plate 1 again occurs. The light leaked from the surface 1a in this manner is generally called an evanescent wave. This evanescent wave
It can be taken out by bringing another optical member close to the total reflection surface 1a at a distance of about the wavelength of light or less. The optical switching element 10 of the present embodiment is designed to modulate light transmitted through the light guide plate 1 at high speed, that is, to switch (on / off) using this phenomenon.

For example, the optical switching element 10 shown in FIG.
In a, the optical element 3 (microprism 4) is the light guide plate 1
At the first position in contact with the total reflection surface 1a of the optical element 3, the evanescent wave can be extracted by the extraction surface 3a of the optical element 3. Therefore, the light 2 extracted by the microprisms 4 of the optical element 3 is changed in angle by the reflection film 46 and becomes the outgoing light 2a. The emitted light 2a is used as light 85 for projection of the projector 80 shown in FIG. On the other hand, in the optical switching element 10b, the optical element 3 is moved to the second position away from the light guide plate 1 by the electrostatic force acting between the electrodes 7 and 8. Therefore, the evanescent wave is not extracted by the optical element 3, and the light 2 does not exit from the inside of the light guide plate 1.

An optical switching element using an evanescent wave functions as a device that can switch light by itself, but as shown in FIG.
It is configured so that it can be arranged in a three-dimensional direction, or even three-dimensionally. In particular, by arranging them two-dimensionally in a matrix or array, it is possible to provide the optical switching device 55 capable of displaying a planar image similarly to liquid crystal or DMD. And in the optical switching device 50 using evanescent light,
Since the moving distance of the optical element 3, which is a switching unit, is on the order of submicron, it can be used as an optical modulator having a response speed one digit or more faster than that of liquid crystal, and a projector 80 or a direct-view type using this can operate at high speed. Can be provided. Further, the optical switching element 10 using evanescent light can turn on and off the light by almost 100% with a movement on the order of submicrons, and can express an image with a very high contrast. Therefore, it is easy to increase the temporal resolution, and a high-contrast image display device can be provided.

Further, the optical switching device 50
Now, the semiconductor integrated substrate 20 on which the drive circuit and the like are built
It is possible to provide the optical switching device 50 having a configuration in which the actuators 6 and the optical elements 3 arranged in an array are stacked on one chip. That is, the optical switching device 55 can be supplied by assembling the optical guide 1 with the optical switching device 50, which is a micromachine or an integrated device in which microstructures such as the actuator 6 and the optical element 3 are constructed on the semiconductor substrate 20. By incorporating the above, it is possible to provide a projector which can display a high-contrast image with a high operation speed and a high resolution.

The actuator 6 is not limited to the one having a pair of upper and lower electrodes shown in FIG.
In addition, those having an intermediate electrode that moves between them have been considered. Therefore, in the following description, the description will be made based on an actuator of an electrostatic drive type with upper and lower electrodes for simplicity, but the configuration of the actuator is not limited to this.

Thus, the light guide 1 and the optical element 3
The (microprism 4) controls the surface roughness of each optical surface in contact with each other with high precision in order to improve the light use efficiency. For this reason, the total reflection surface 1a of the light guide 1
And the extraction surface 3a of the microprism 4 are easily attracted to each other. When the so-called sticking phenomenon occurs, the electrostatic actuator is driven to the second position as shown by the optical switching element 10b on the right side in FIG. It becomes difficult. Therefore, there arises a problem that a desired operation is not performed even if a voltage is applied, or a switching speed is reduced. Further, it is necessary to increase the driving voltage, and the power consumption may increase.

On the other hand, by reducing the friction coefficient of the optical element or the total reflection surface of the light guide, it is possible to make it difficult for suction to occur. For example, it is considered that diamond-like carbon is formed on the extraction surface.
However, when diamond-like carbon is formed on the extraction surface, the particles may be generated and adhere to the extraction surface. The gap between the light guide and the optical element, that is, the total reflection surface of the light guide and the micro- It is difficult to manage the gap between the optical element and the extraction surface on the order of submicrons. In addition, since the refractive index is significantly higher than that of glass, there is a problem that optical characteristics are changed.

Therefore, in the present invention, an optical switching unit which can prevent the light guide from being attracted to the extraction surface of the optical switching element and can accurately manage the gap between the extraction surface and the total reflection surface, It is an object of the present invention to provide an optical switching device, an optical guide, and a method for manufacturing an optical switching unit. It is another object of the present invention to provide a highly reliable optical switching unit that has high light use efficiency and can be driven at high speed with a low voltage. Furthermore, by adopting the optical switching unit of the present invention, the resolution is high,
It is another object of the present invention to provide a video display device capable of displaying a bright image.

[0018]

Therefore, in the present invention,
Instead of forming a new layer such as diamond-like carbon on the total reflection surface or extraction surface, one of these surfaces has a shape that itself has minute projections to prevent adsorption. Further, the distance between the total reflection surface and the extraction surface can be managed. That is, according to the present invention, a light guide including a total reflection surface capable of transmitting incident light by total reflection, and a first position close to the total reflection surface and a second position separated from the total reflection surface are driven. An extraction surface of the micro-optical device is close to a total reflection surface at a first position, and light can be extracted from a light guide; and a second position has an extraction surface from the total reflection surface. An optical switching unit having a micro-optical element that does not extract light at a distance, wherein at least one of the total reflection surface and the extraction surface is formed with a small convex portion extending at least a part of the light guide or the micro-optical element. It is characterized by having.

On the optical surface (total reflection surface or extraction surface) of at least one of the light guide and the micro optical element which comes into contact at the first position, a part of these surfaces is extended to form a minute projection. Thus, the contact area between the total reflection surface and the extraction surface can be reduced, and the attraction force can be reduced. Then, the suction force is weakened by a slight gap between these surfaces, and the separation can be easily performed. For this reason, it is possible to prevent the disadvantages due to the suction, and to increase the switching reliability and the response speed. At the same time, since a new layer is not formed, the gap control is not difficult with it, and by controlling and forming the shape of the minute projection, the total reflection surface or the surface is formed so that the evanescent light can be sufficiently extracted. Can manage the distance from the extraction surface. Therefore, it is possible to provide a highly durable and highly reliable optical switching unit, a device constituting the optical switching unit, and a light guide, which have high light use efficiency, are free from operation failure and deterioration of operation characteristics due to adsorption, and the like.

In an optical switching unit using evanescent light, the evanescent light has a function of:
Decays exponentially rapidly. For this reason, in order to increase the light use efficiency, the height of the minute projection is 1 to 50 n.
m is desirable. Further, it is desirable that the height of the minute projection is in the range of 1 to 30 nm.
Thus, the evanescent wave extraction efficiency can be increased from 50% or more to 90% or more. The height of the minute protrusion is set so that the extraction efficiency of the evanescent wave becomes 95% or more.
A range of 1 to 20 nm is also possible. Therefore, by controlling the minute projections at such a height, the optical switching unit is capable of sufficiently weakening the attraction force and increasing the operation speed, and has a sufficiently high light use efficiency. Can be provided.

The minute projections extending on the flat surface may be formed in a step shape, but are preferably formed in a dome shape. In the case of the dome shape, the light guide and the extraction surface are in point contact, so that a problem due to suction is more likely to occur. In addition, the dome-shaped sub-micron convex portion can be easily formed by irradiating the surface of the total reflection surface or the extraction surface with a laser without providing a new layer. Further, by adjusting the diameter, energy, irradiation time, and the like of the laser beam, the diameter, height, and the like of the dome-shaped minute projection can be easily controlled with high accuracy. Therefore, the size (distance) of the gap generated between the total reflection surface and the extraction surface at the first position where the total reflection surface and the extraction surface are close to each other can be easily managed.

As described above, the optical switching unit of the present invention has a process of forming a minute convex portion extending at least a part of the light guide or the micro optical element on at least one of the total reflection surface and the extraction surface. Such a minute projection can be easily and accurately formed by irradiating either the total reflection surface or the extraction surface with a laser.

In an optical switching unit in which a plurality of micro-optical elements are arranged at a predetermined pitch, it is desirable that the minute projections be formed at a pitch that is approximately twice the pitch of the micro-optical elements. A portion at which the extraction efficiency of the minute convex portion is maximized, that is, a portion where the vertex of the minute convex portion comes into contact with either the total reflection surface or the extracting surface can be arranged in each micro optical element. Thereby, the minute convex portions can be arranged evenly for each micro optical element. Therefore, an evanescent light can be reliably extracted by each micro optical element, and furthermore, an optical switching unit that can easily make the intensity or efficiency of the extracted evanescent light almost equal can be provided.

Further, it is desirable that the minute projections are formed at a pitch substantially equal to or less than the pitch of the micro optical element. Extraction surface in addition to the uniform arrangement described above,
Alternatively, in the total reflection surface that comes into contact with the extraction surface, the degree of freedom in arranging the minute projections increases in units of the extraction surface, so that the variation in the light extracted on the extraction surface can be reduced. That is, the center of the pixel is brightened by placing the apex of the minute convex portion at the center of the extraction surface, or the balance of brightness in the pixel is improved by arranging a plurality of minute convex portions on one extraction surface. Can be. Therefore, it is possible to provide a high quality and highly reliable optical switching unit having high light use efficiency, an effect of preventing adsorption, and excellent color balance.

The optical switching unit of the present invention has a microactuator for driving each micro-optical element, and includes a light guide, a micro-optical element,
The microactuators can be realized in a stacked configuration on the substrate in order from the top. As the microactuator, an electrostatic actuator can be used. In the optical switching unit of the present invention, since the load due to the suction is not or very small, the micro optical element is moved to the first position and the second position, and the microswitch is moved at high speed. Can be turned on and off. Therefore, it is possible to provide an optical switching unit capable of high-speed driving at low voltage, saving energy and having high resolution.

Therefore, in a video display device such as a projector having a light switching unit of the present invention and a means for inputting and outputting light for forming an image to the light guide, the power consumption is small, and the device can be driven at a high frequency. In addition, it is possible to provide a highly reliable image display device having high resolution.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be further described below with reference to the drawings. Hereinafter, an example in which the present invention is applied to a device that switches light using the evanescent wave described above will be described. As shown in FIG. 3 and FIG. 4, the optical switching element 10 of
Light guide plate (light guide) 1 capable of total reflection and transmission of light, and a micro-optical element (hereinafter referred to as an optical element) approaching (first position) and separating (second position) from the light guide plate 1
3, a microactuator (hereinafter referred to as an actuator) 6 for driving the optical element 3, and a semiconductor substrate 2 on which a circuit for controlling the actuator 6 is built.
0.

The optical element 3 is molded from a resin, and the side facing the surface (total reflection surface) 1a of the light guide 1 is a surface (contact surface or extraction surface) 3a in contact with the total reflection surface 1a.
And a V-shaped microprism (prism) 4 for extracting and guiding the evanescent wave leaked out when the surface 3a approaches the total reflection surface 1a, and guiding the guided light to the light guide 1. A reflecting film 46 for reflecting the light in a substantially vertical direction;
And a support structure 5 for supporting the U-shaped prism 4.

Since the structure of the actuator 6 of this embodiment is the same as that described above with reference to FIG. 2, a detailed description of the structure and its operation will be omitted below. In the optical switching device 50 of this example, a plurality of optical switching elements 10 each including the optical element 3 and the actuator 6 for driving the optical element 3 are prepared, and these optical switching elements 10 are mounted on the semiconductor substrate 20. An image device (optical switching device) 50 that is arranged in an array and controls each optical switching element by a CMOS circuit of the semiconductor substrate 20 is provided. Then, the light switching unit 55 can be configured by stacking the light guide 1 and the light switching device 50, and can be used as a light valve of the video display device 80 in the same manner as described above.

The extraction surface 3a of the optical element 3 of this embodiment is substantially flat in the order of microns, but the resin constituting the microprism 4 is extended in the order of submicrons.
That is, a plurality of dome-shaped minute convex portions 70 formed of the same material as the prism 4 are provided. FIG. 5 schematically shows an enlarged view of the minute projection 70 provided on the extraction surface 3a. As will be described below, such a minute projection 70 does not overlap a new layer (film) on the microprism 4, but instead forms a surface (extraction surface) 3 of the microprism 4.
It can be formed by irradiating a with a CO ₂ laser.
That is, the surface 3a is partially thermally expanded by irradiating a laser beam of appropriate energy for an appropriate time,
It can be dome-shaped. Further, the shape can be freely and accurately formed by controlling the spot diameter, output and irradiation time of the laser beam. In this example,
Although the minute projections 70 are formed on the extraction surface 3a so that the height h is 20 nm and the diameter d is about 10 μm, it is easy to control the height and diameter.

FIG. 3 shows a state at the first position when the extraction surface 3a provided with the minute projections 70 is in contact with the total reflection surface 1a. The extraction surface 3a contacts the total reflection surface 1a of the light guide 1 at the tip 70a of the minute projection 70. In the optical switching unit 55 of this example, a dome-shaped minute convex portion 70 is provided, and the light guide 1 (total reflection surface 1) is provided.
a) and the extraction surface 3a contact at a point. Therefore, the contact area is reduced, and the effect of adsorption can be reduced when the entire surface is in contact. That is, since the minute convex portion 70 is processed on the extraction surface 3a, the entire surface does not completely reach the total reflection surface 1a of the light guide 1 in the ON state, but the vertex 70a or the vicinity thereof partially covers the light guide 1a. And a small gap s is formed between the total reflection surface 1a and the extraction surface 3a in other portions. In this example,
Since the height h of the dome-shaped minute projection 70 is adjusted to 20 nm, a slight gap s of about 20 nm at the maximum is left. Therefore, the total reflection surface 1a and the extraction surface 3a do not come into close contact with each other, and a strong suction force is not generated.

Further, as shown in FIG. 4, when the optical element 3 is peeled off from the total reflection surface 1a (second position), the gap s
Since the air enters from above, the optical element 3 can be easily separated from the total reflection surface 1a with a small driving force. Therefore, the driving force for turning off (the second position) as shown in FIG. 4 can be reduced. Therefore, it is possible to reduce the driving voltage when turning on and off the optical switching element 10, and to perform high-speed driving at a low voltage. Furthermore, there is no fear of sticking or the like. For this reason,
Energy saving, high operating frequency, and highly reliable optical switching element 10 (optical switching device 5
0) and the optical switching unit 55 can be provided.

On the other hand, since the minute projections formed on the extraction surface 3a are formed by laser processing the prism 4, it is made of the same material (resin material) as the prism 4 and has almost the same refractive index. . Therefore, no optical disadvantage occurs from the material. Further, the dome-shaped minute convex portion 70
Is kept within a range where the evanescent light extraction efficiency hardly decreases in the ON state. That is, the gap s generated in the ON state by the minute projection 70 is in a range where the extraction efficiency of the evanescent light does not greatly change, and the light use efficiency hardly decreases. As a result, the evanescent wave can be efficiently extracted by the surface 3a of the optical element portion 3 including the minute convex portion 70 in the ON state, and the emitted light 2a in the direction perpendicular to the light guide plate 1 can be obtained by the microprism 4. This makes it possible to express an image or the like by switching the light 2.

FIG. 6 shows the result of calculating the extraction rate of evanescent light. The incident angle of the incident light 2 is 50 degrees, the refractive index of the light guide 1 is 1.5, and the incident light 2 is 350 n
The relationship between the extraction surface 3a and the total reflection surface 1a, that is, the interval or gap s, and the rate extracted at that time when m (solid line), 500 nm (dashed-dotted line), and 700 nm (dashed line) are used is shown. As can be seen from this figure, the extraction rate of the evanescent wave attenuates exponentially with the distance between the total reflection surface 1a of the light guide 1 and the extraction surface 3a of the optical switching element 10. However, when the interval s is about 20 nm, the evanescent wave extraction efficiency is 95% or more.
Therefore, in the optical switching element 10 or the optical switching unit 55 of this example, as described above,
It is possible to provide an optical switching unit which can be driven at high speed with energy saving and has high reliability, while hardly reducing the light use efficiency, even though it is a highly reliable optical switching unit 55.

By lowering the attraction force between the extraction surface 3a and the total reflection surface 1a, reducing the driving energy and increasing the operating frequency,
To further increase the reliability, it is desirable that the gap s be large. That is, it is desirable that the height h of the dome-shaped fine convex portion 70 is higher. However, when the gap s increases, the extraction rate of evanescent light decreases as shown in FIG.
Light utilization efficiency decreases. Considering such a relationship, in terms of improving operating frequency and reliability,
The height h of the minute protrusion 70 is preferably about 1 to 30 nm. Even when the height h of the minute protrusion 70 is 30 nm, that is, even when the maximum of the gap s is 30 nm, the use efficiency of evanescent light is the lowest. The light extraction efficiency of about 90% can be maintained in the portion where the light is extracted. The extraction efficiency increases as approaching the apex 70a of the dome-shaped minute projection 70.
Therefore, even if the extraction efficiency of evanescent light in the peripheral portion of the minute convex portion 70 becomes about 90%, the extraction efficiency of evanescent light is high in the central portion, and almost all of the switching element or the pixel 10 uses light. Efficiency does not decrease.

Further, in order to achieve a higher speed and lower power by improving the adsorption preventing effect, the height h of the minute projection 70, that is, the gap s, can be set to about 1 to 50 nm. Even when the gap s is 50 nm, that is, at the point where the light use efficiency is most reduced, the evanescent light extraction efficiency of about 75% can be maintained. Therefore, as described above, the light use efficiency increases toward the center of the minute projection 70. Therefore, according to the present invention, the power consumption can be reduced, the operation speed can be increased, and the reliability can be increased while maintaining high light use efficiency of the switching element or the switching unit 55 as a whole.

Referring to FIGS. 7 to 11, the layout of the minute projection 70 will be discussed. First, FIG.
A state is shown in which a plurality of optical switching elements 10 each constituting a pixel are arranged in an array. Micro prisms 4 each having a square shape of 20 μm and serving as pixels when displaying an image are arranged in a grid pattern at a pitch L.

FIGS. 8 to 11 schematically show the pixels or the extraction surface 3a of the prism 4 as viewed from above, and show some examples of the layout of the minute projections 70. FIG. FIG. 8 shows an example in which minute projections 70 having a diameter d of 10 μm or less are arranged at a pitch M which is １ ／ of the pixel pitch L or less. In this example, specifically, the minute projection 70 having a diameter d of 8 μm is １ ／
They are arranged at a pitch M of L. Therefore, four micro convex portions 70 can be arranged in one micro prism 10 so as not to be evenly overlapped. It is desirable that the portions where these minute projections 70 are formed do not overlap with each other, thereby preventing the extraction surface 3a from having a complicatedly curved surface. Therefore, even in the optical element 3 having the fine projections 70 formed on the surface, unnecessary light scattering and interference can be prevented.

In the optical switching device 50 of this embodiment,
A plurality of minute projections 70 are regularly arranged in one pixel or prism 4. As described above, in the dome-shaped micro convex portion 70, the extraction rate of the evanescent light becomes higher and brighter toward the center 70a, and the gap s becomes larger as the distance from the center 70a increases, so that the extraction rate of the evanescent light becomes lower and darker. In this example, although one pixel or the prism 4 is very microscopic, there are regularly a plurality of bright portions and dark portions, and uniform intensity can be obtained as a whole. The same applies to other adjacent pixels or prisms 4. Therefore, it is possible to provide the optical switching device 50 and the unit 55 that have a small variation in light intensity and can display a higher quality image not only in the pixel or the prism 4 but also in the entire device 50.

FIG. 9 shows a minute projection 7 having a diameter d of φ18 μm.
0 are arranged at the same pitch M as the pitch L of the pixels or the prisms 4.
It is arranged so that 0a coincides with the center 4a of the pixel or prism 4. Therefore, in the optical switching device 50 of this example, the center 4a of the pixel or prism 4
However, a pixel display which is brightest and slightly darker in the surroundings can be obtained. However, also in this example, since the brightest part always exists at the center of the pixel and the symmetry is high, a high-quality image can be displayed.

FIG. 10 shows an example in which the minute protrusions 70 are arranged at the same diameter d and pitch M as in FIG.
Are arranged so that the center 70a is not the center 4a of the pixel or prism 4, but coincides with the four corners 4b. Therefore, in the optical switching device 50 of this example, the four corners 4b of the pixel or prism 4 are the brightest and the center 4a.
It gets darker as you go. However, even in the arrangement of this example, the four corners of the pixel are always bright and have high symmetry. Therefore, a high-quality image can be displayed.

FIG. 11 also shows an example in which the minute protrusions 70 are arranged at the same diameter d and pitch M as in FIG.
Are arranged so as to coincide with the center 4a of the pixel or the center of the prism 4 from the center 4a of the side of the prism. Therefore, in the optical switching device 50 of the present example, the side 4c of the pixel or the prism 4 is brightest and becomes darker toward the center 4a. However, even in the arrangement of this example, the sides of the pixels are always bright and the symmetry is high. Therefore, a high-quality image can be displayed.

FIG. 12 shows an example in which minute projections 70 having a diameter d of φ38 μm are arranged at a pitch M of 2 L. In this example,
The pitch M of the minute projections 70 is twice as large as the pixel pitch L, and one microprojection 70 is provided for four pixels or prisms 4. Also in this example, the center 70a of the minute projection 70 can be arranged at the center of four pixels or the prism 4, for example. With this arrangement, one corner of the pixel or the prism 4 alone is bright, and the brightness decreases as it goes diagonally. Therefore, in this arrangement, there is always a bright portion for each pixel or prism, and the light intensity of the pixels is almost the same, but the symmetry is reduced within the pixel and the image quality is slightly inferior to each of the above arrangements .

On the other hand, it is also possible to form a minute projection 70 having a larger diameter d. FIG. 12 shows the diameter d.
Is shown by a dash-dot line in FIG. In this example, a pixel or prism 4 including the center 69a of the minute convex portion 69 and a pixel or prism 4 not including the center 69a are generated. As described above, since the center 69a is the brightest, in the arrangement of this example, in addition to the occurrence of the intensity distribution in the pixel,
An intensity distribution also occurs between pixels. Therefore, the image quality is further degraded.

As can be seen from the above, in order to maintain the balance of light intensity or light utilization between pixels, the pitch M of the minute projections 70 is twice or less than the pitch L of the pixels or the prism 4. desirable. Further, in consideration of maintaining the balance of the light intensity or the light use efficiency in the pixel, the pitch M of the minute projection 70 is desirably equal to or less than the pitch L of the pixel or the prism 4. Further, the minute convex portions 70 may be arranged in a grid pattern, that is, not limited to a linear arrangement, but may be arranged randomly as long as they do not overlap with each other. However, in the case of a random arrangement, it is necessary to consider that the intensity distribution does not increase between pixels. Further, by providing the minute convex portions 70, it is possible to prevent adsorption and provide an optical switching device 50 and a unit having high reliability and high response speed.

The manner in which the optical switching device 50 (optical switching element 10) provided with such a minute projection 70 will be described. As shown in FIG. 13, the optical switching device 50 of this example includes a lower electrode 8, an electrode layer serving as a spring and an upper electrode, using a sacrificial layer 31 on an upper surface 21 of a substrate 20 on which a CMOS is formed. 7 and the structure as the actuator 6 such as the post 11 are formed. Then, the micro optical element 3 is formed on the actuator 6 by mold transfer. In the step of manufacturing the optical element 3 by mold transfer, an ultraviolet-curable resin material is sandwiched between two substrates (one substrate is a mold for transferring the shape) and pressure is applied from both sides, or It is manufactured by a 2P (Photo-polymerization) method of curing by light or heat. First, a resin layer serving as a V-shaped support 5 is formed by a 2P method using a V-shaped transfer mold.
6 is formed by sputtering or the like, and then the resin layer to be the microprism 4 is formed using a flat transfer mold.
It is formed by the P method.

Next, as shown in FIG. 14, the surface 3a of the microprism 4 is irradiated with a CO ₂ laser,
Is partially expanded by thermal expansion of the resin layer constituting
To form At this time, the laser beam 3 irradiating the surface 3a
By controlling the spot diameter, energy, and irradiation time of No. 9, it is possible to form the minute projection 70 having a desired diameter and height.

Then, as shown in FIG. 15, the optical element 3 is separated into individual pixels or units constituting the microprisms 4 by plasma etching or the like so as to become the optical switching device 50 used as the optical switching unit 55. . After the element separation, the minute projections 70 may be formed by laser irradiation. However, there is a possibility that the optical element 3 expands in the direction of the element gap 47 due to the laser irradiation. Cause. Therefore, it is desirable to process the extraction surface 3a before element separation as in this example.

Through the above steps, the actuator 6 and the optical element 3 are vertically stacked on the semiconductor substrate 20, and the optical switching device 50 having the minute projection 70 provided on the surface of the optical element 3 is manufactured. By combining such an optical switching device 50 and the optical guide 1, the optical switching unit 55 described with reference to FIGS. 1 and 2 can be provided.

As shown in FIGS. 16 and 17,
It is also possible to provide the minute convex portion 71 on the surface of the total reflection surface 1a of the light guide 1 instead of the side of the optical switching element 10. Similarly, in this case, similarly to the above, the total reflection surface 1a of the light guide 1 is dome-shaped by irradiating a laser beam, and has a height of about 1 to 50 nm, preferably 1 to 30 nm.
A small convex portion 71 having a height h of about m, more preferably about 1 to 20 nm can be provided, and the gap s between the total reflection surface 1a and the extraction surface 3a can be managed in the same manner as described above. Therefore, also in the optical switching unit 55 of the present example, the contact area between the total reflection surface 1a and the extraction surface 3a can be reduced, while the light extraction efficiency can be almost maintained. Further, by forming the minute projections 71 by laser irradiation, it becomes possible to extend the minute projections 71 of a highly accurate shape using the same material on the total reflection surface 1a, and the optical performance is also very good. The optical switching unit 55 can be provided with high yield. Therefore, it is possible to provide the optical switching device 55 having a high response speed while maintaining the utilization efficiency of the evanescent light, preventing the adsorption, and preventing the switching operation failure. Also, a small convex portion 7 is provided on the light guide 1 side.
1 and the layout are shown in FIG.
The same thing as described with reference to FIG. 12 can be said.

As described above, in the optical switching unit 55 of the present invention and the above-described manufacturing method, the height h of the minute projection 70 is controlled by controlling the intensity and time of the laser when the minute projection 70 is formed. It is possible to precisely control, and a part of the prism 4 forming the extraction surface 3a or a part of the light guide 1 forming the total reflection surface 1a is thermally expanded, and the minute projection 70 made of the same material as these is used. Alternatively, 71 can be extended very accurately. Therefore, the contact area between the total reflection surface 1a and the extraction surface 3a can be reduced, the adsorption can be prevented and the separation can be easily performed, and the optical switching device 50 that can maintain the light use efficiency sufficiently high can be manufactured and manufactured with high yield. Can be provided. For this reason, according to the present invention, it is possible to prevent a reduction in speed or an increase in driving voltage due to adsorption without lowering the light use efficiency, and to prevent an operation failure due to sticking or the like. Therefore, it is possible to manufacture the optical switching device 50 having a high operation speed, a small driving power, and a high reliability at a high yield and at a low cost. The unit 55 can be supplied at low cost. Further, by employing the light switching unit 55 as a light valve, a highly reliable video display device that can display a bright image with a high operating frequency, high resolution, and low cost can be provided.

Further, since a part of the surface on which the microprism 4 or the light guide 1 is formed is thermally expanded by laser, unlike the case where a layer (film) is newly formed by diamond-like carbon or the like, the surface is Thus, there is no possibility that particles and the like will be generated, and it is possible to avoid troubles caused by forming a new film and a decrease in yield. Further, by using the same material, the manufacturing method can be simplified, and the gap between the light guide 1 and the microprism 4 can be easily managed on the order of submicrons. Further, since the minute projections are formed on the respective surfaces and are made of the same material, the refractive index does not change and the electrical optical characteristics do not change. Therefore, the optical switching device 50 and the optical switching unit 55 having good optical matching, high reliability, and high quality can be easily provided.

In the above description, a dome-shaped one formed by using a laser beam is described as an example of the minute projection 70. However, a dome-shaped or other shape, such as a photolithography, is used. It is also possible to form a step-shaped minute projection, and it is possible to reduce the contact area while accurately managing the gap between the total reflection surface and the extraction surface. However, as the shape of the minute convex portion, a circular shape such as a dome shape or a hemispherical shape, which is a shape that makes more contact at a point, is excellent, and a conical shape or a truncated cone is also excellent. Of these shapes, it is possible to control these shapes by heat treatment after photolithography.However, considering the ease of manufacturing and the heat resistance of the resin, the method of irradiating with a laser is the simplest method. It is easy to control the shape of the minute projections to be formed. Since a shape close to point contact, such as a dome shape, can be obtained, it can be said that manufacturing a minute projection by a laser is the most suitable shape of the minute projection and a method for manufacturing the same.

Further, the above optical switching device 5
At 0, the actuator is an electrostatic type, but other actuators such as a piezo type may of course be used. Although the image display device 80 is shown as an example using the optical switching device 50 and the optical switching unit 55 of the present invention, the optical switching unit 55 of the present invention is not limited thereto.
It can be applied to various kinds of devices such as an optical printer.

[0055]

As described above, in the optical switching unit of the present invention, instead of forming a new layer such as diamond-like carbon on the total reflection surface or the extraction surface, these surfaces themselves are formed. By adopting a shape provided with a minute convex portion, adsorption is prevented, and the distance between the total reflection surface and the extraction surface can be managed with high accuracy. Therefore, under the condition that the light use efficiency is maintained, it is possible to solve problems such as operation failure due to the adsorption of the micro optical element and increase in power with a good yield, and it is possible to drive at high speed, save energy, further improve durability and A highly reliable optical switching unit can be provided at low cost. Further, by employing this optical switching unit, it is possible to provide a video display device having a high resolution and capable of displaying a bright image.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a projector using an image display device using evanescent light.

FIG. 2 is a diagram showing an outline of an optical switching unit using evanescent light.

FIG. 3 is a cross-sectional view illustrating an entire configuration of the optical switching unit according to the embodiment of the present invention, and is a diagram illustrating an ON state.

FIG. 4 is a sectional view showing an off state of the optical switching device shown in FIG. 3;

FIG. 5 is an enlarged view schematically showing a minute projection extending from an extraction surface according to the present invention.

FIG. 6 is a graph showing a relationship between a distance of an extraction surface and an extraction rate of an evanescent wave.

FIG. 7 is an explanatory diagram showing an arrangement of pixels or microprisms.

FIG. 8 is a diagram showing a layout of minute projections extended on an extraction surface of a pixel or a microprism shown in FIG. 7;

FIG. 9 is a diagram showing an example different from the layout shown in FIG. 8;

FIG. 10 is a diagram showing an example further different from the layout shown in FIG. 8;

FIG. 11 is a diagram showing an example further different from the layout shown in FIG. 8;

FIG. 12 is a view showing a layout of different minute projections.

13 is a diagram illustrating a manufacturing process of the optical switching element illustrated in FIG. 3, illustrating a state in which an actuator is formed on a semiconductor substrate, and further, the optical element is molded with a resin.

FIG. 14 is a view illustrating a manufacturing process of the optical switching element illustrated in FIG. 3 and illustrating a state in which minute projections are formed on the surface of the optical element by laser irradiation.

FIG. 15 is a diagram illustrating a manufacturing process of the optical switching element illustrated in FIG. 3, illustrating a state in which a resin layer is separated and a sacrificial layer is removed.

FIG. 16 is a view showing a different example of the present invention, and is a view schematically showing an optical switching unit in which a minute convex portion is provided on a light guide side, and is a view showing an ON state.

FIG. 17 is a diagram illustrating an off state of the optical switching unit illustrated in FIG. 16;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light guide 1a Total reflection surface 2 Incident light 3 Optical element 3a Extraction surface 4 Micro prism 5 V-type support structure 6 Actuator part 7 Upper electrode and spring structure 8 Lower electrode 9 Anchor 10 Optical switching element 11 Post (post) 20 Semiconductor Substrate 46 Reflective film 70, 71 Minute projection 70a, 71a Center of minute projection

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 9/14 H04N 9/14 F term (Reference) 2H041 AA16 AB27 AB40 AC06 AZ01 AZ08 5C058 AA18 AB04 BA25 BA35 EA02 EA13 EA27 EA42 EA51 5C060 BA03 BA09 BB01 BC01 GA01 HC01 HC09 HC12 HC17 HC20 HD05 JB06 5C064 EA05

Claims (37)

[Claims] 1. A light guide having a total reflection surface capable of transmitting incident light by total reflection, and is driven to a first position close to the total reflection surface and a second position away from the total reflection surface. A micro-optical element, wherein at the first position, an extraction surface of the micro-optical element is close to the total reflection surface and light can be extracted from the light guide, and at the second position, the total reflection surface A micro-optical element, wherein the extraction surface is separated from and does not extract light, and wherein at least one of the total reflection surface and the extraction surface has at least a part of the light guide or the micro-optical element. An optical switching unit, wherein an extended minute projection is formed. 2. The optical switching unit according to claim 1, wherein the minute projection has a dome shape. 3. The optical switching unit according to claim 1, wherein the height of the minute projection is in a range of 1 to 50 nm. 4. The optical switching unit according to claim 1, wherein the height of the minute projection is in a range of 1 to 30 nm. 5. The optical switching unit according to claim 1, wherein the height of the minute projection is in a range of 1 to 20 nm. 6. The optical switching unit according to claim 1, wherein the minute projection is formed by laser irradiation. 7. The light according to claim 1, wherein the plurality of micro-optical elements are arranged at a predetermined pitch, and the minute projections are formed at a pitch that is within approximately twice the pitch of the micro-optical elements. Switching unit. 8. The micro-optical element according to claim 1, wherein the plurality of micro-optical elements are arranged at a predetermined pitch, and the minute convex portions are formed at a pitch substantially equal to or less than the pitch of the micro-optical elements. Optical switching unit. 9. The micro-actuator according to claim 1, further comprising a micro-actuator for driving the micro-optical element,
An optical switching unit, wherein the micro-optical element and the micro-actuator are stacked on a substrate. 10. The optical switching unit according to claim 9, wherein the microactuator is an electrostatic actuator. 11. An image display device comprising: the optical switching unit according to claim 1; and means for inputting and outputting light for forming an image to and from the light guide. 12. A micro-optical element driven to a first position close to a total reflection surface of a light guide capable of transmitting incident light by total reflection and a second position away from the total reflection surface, In the first position, the extraction surface of the micro-optical element is close to the total reflection surface, and light can be extracted from the light guide. In the second position, the extraction surface is separated from the total reflection surface. An optical switching device having a micro optical element that does not extract light, wherein a micro convex portion extending at least a part of the micro optical element is formed on the extraction surface. 13. The optical switching device according to claim 12, wherein the minute projection has a dome shape. 14. The optical switching device according to claim 12, wherein the height of the minute projection is in a range of 1 to 50 nm. 15. The optical switching device according to claim 12, wherein the height of the minute projection is in a range of 1 to 30 nm. 16. The optical switching device according to claim 12, wherein the height of the minute projection is in a range of 1 to 20 nm. 17. The optical switching device according to claim 12, wherein the minute projections are formed by laser irradiation. 18. The light according to claim 12, wherein a plurality of said micro-optical elements are arranged at a predetermined pitch, and said micro-projections are formed at a pitch that is within approximately twice the pitch of said micro-optical elements. Switching device. 19. The micro-optical element according to claim 12, wherein the plurality of micro-optical elements are arranged at a predetermined pitch, and the minute convex portions are formed at a pitch substantially equal to or less than the pitch of the micro-optical elements. Optical switching device. 20. The optical switching device according to claim 12, further comprising a micro-actuator for driving the micro-optical element, wherein the micro-optical element and the micro-actuator are stacked on a substrate. 21. The optical switching device according to claim 20, wherein the microactuator is an electrostatic actuator. 22. A micro-optical element having a total reflection surface capable of transmitting incident light by total reflection and having an extraction surface, wherein a micro-optical element having a extraction surface has a first position close to the total reflection surface and a first position separated from the total reflection surface. 2, the extraction surface of the micro-optical element is close to the total reflection surface at the first position, and light can be extracted from the light guide, and the total reflection surface can be extracted at the second position. A light guide from which light is not extracted because the extraction surface is separated from the light guide, wherein a minute convex portion extending at least a part of the light guide is formed on the total reflection surface. 23. The light guide according to claim 22, wherein the minute convex portion has a dome shape. 24. The light guide according to claim 22, wherein the height of the minute projection is in a range of 1 to 50 nm. 25. The light guide according to claim 22, wherein the height of the minute projections is in a range of 1 to 30 nm. 26. The light guide according to claim 22, wherein the height of the minute projection is in a range of 1 to 20 nm. 27. The light guide according to claim 22, wherein the minute projections are formed by laser irradiation. 28. The light guide according to claim 22, wherein a plurality of the micro optical elements are arranged at a predetermined pitch, and the minute projections are formed at a pitch of about twice or less the pitch of the micro optical elements. 29. A light guide according to claim 22, wherein a plurality of said micro optical elements are arranged at a predetermined pitch, and said minute projections are formed at a pitch substantially equal to or less than a pitch of said micro optical elements. . 30. A light guide having a total reflection surface capable of transmitting incident light by total reflection, and is driven to a first position close to the total reflection surface and a second position away from the total reflection surface. A micro-optical element, wherein at the first position, the extraction surface of the micro-optical element is close to the total reflection surface;
A method of manufacturing a light switching unit, comprising: a micro-optical element capable of extracting light from the light guide, wherein the extraction surface is separated from the total reflection surface and does not extract light at the second position. A method for manufacturing an optical switching unit, comprising a step of forming, on at least one of a reflection surface and the extraction surface, a minute convex portion extending at least a part of the light guide or the micro optical element. 31. The manufacturing of an optical switching unit according to claim 30, wherein the step of forming the minute projections includes a step of irradiating either the total reflection surface or the extraction surface with a laser to form the minute projections. Method. 32. The method of manufacturing an optical switching unit according to claim 30, wherein in the step of forming the minute projection, the dome-shaped minute projection is formed. 33. The method of manufacturing an optical switching unit according to claim 30, wherein, in the step of forming the minute projection, the minute projection having a height in a range of 1 to 50 nm is formed. 34. The method for manufacturing an optical switching unit according to claim 30, wherein, in the step of forming the minute projections, the minute projections having a height in a range of 1 to 30 nm are formed. 35. The method for manufacturing an optical switching unit according to claim 30, wherein, in the step of forming the minute projection, the minute projection having a height in a range of 1 to 20 nm is formed. 36. The micro optical element according to claim 30, wherein a plurality of the micro optical elements are arranged at a predetermined pitch, and in the step of forming the micro convex section, the micro convex section is formed at a pitch of about 2 of the micro optical element pitch. A method for manufacturing an optical switching unit, wherein the optical switching unit is formed at a pitch within double. 37. The micro optical element according to claim 30, wherein a plurality of the micro optical elements are arranged at a predetermined pitch, and in the step of forming the micro convex section, the micro convex section is substantially equal to a pitch of the micro optical element. Alternatively, a method for manufacturing an optical switching unit, wherein the optical switching unit is formed at a pitch smaller than that.