JP2004191878A - Prism system, projection display device using the same, rear projector, and multi-vision system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the transmission characteristics of light on an air interface in a total reflection prism system in which a plurality of prisms are combined via air layer. <P>SOLUTION: The prism system is provided with a light bulb 31, a first prism 32 and a second prism 33. The first prism 32 and the second prism 33 are coupled together on both sides of the air layer 35. A light beam 36 made incident from a third surface 38 of the first prism 32 is all reflected on a second surface 37 of the first prism 32 as an interface with the air layer 35 and made incident on the light bulb 31. An image forming light beam 40 reflected on the light bulb 31 passes the air layer 35 and is emitted from a second surface 41 of the second prism 33. A periodic structure with pitch smaller than wavelength of the incident light is formed at least one of the second surface 37 of the first prism 32 and a first surface 39 of the second prism 33 forming the air layer 35. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a prism device, a projection display device using the same, a rear projector, and a multi-vision system.
[0002]
[Prior art]
2. Description of the Related Art In order to obtain a large screen image, a method of forming an optical image according to an image signal on a light valve, irradiating the optical image with light, and enlarging and projecting the image on a screen by a projection lens has been well known. If a reflective spatial light modulator that forms an image by controlling the traveling direction of light according to a video signal is used as a light valve, a high-brightness projected image with high light use efficiency can be displayed.
[0003]
FIG. 11 shows a conventional configuration example of an optical system of a projection display device using a reflection type light valve. The light source 1 is constituted by the lamp 1a and the concave mirror 1b. The concave mirror 1b is an elliptical mirror, and is formed by depositing an optical multilayer film that transmits infrared light and reflects visible light on the inner surface of a glass substrate. The lamp 1a is arranged such that the center of the light emitter is located at the first focal point f1 of the concave mirror 1b. The light emitted from the lamp 1a is reflected by the concave mirror 1b, forms an illuminant image at the second focal point f2 of the concave mirror 1b, passes through the second focal point f2, and then enters the relay lens 2. The light emitted from the relay lens 2 is reflected by the total reflection mirror 3 and enters the total reflection prism 6 via the field lens 4. The total reflection prism 6 has two single prisms arranged via an air layer 8. Light incident on the total reflection prism 6 is totally reflected by the interface of the air layer 8 and enters the light valve 5. The light valve 5 forms an optical image by controlling the traveling direction of light for each pixel according to a video signal and changing the reflection angle. The reflected light from the light valve 5 passes through the prism 6 and then enters the projection lens 7, and the optical image on the light valve 5 is enlarged and projected on a screen (not shown) by the projection lens 7. Here, the configuration and operation of the total reflection prism 6 will be described below with reference to FIG. 12 (for example, see Patent Document 1).
[0004]
The total reflection prism 6 includes a first prism 12 and a second prism 13. The light valve 5 is arranged near the first surface 14 of the first prism 12, and the second surface 15 of the first prism 12 forms the air surface 8 with the first surface 17 of the second prism 13. The second surface 18 of the second prism 13 is parallel to the first surface 14 of the first prism 12, and the third surface 19 of the second prism 13 is perpendicular to the second surface 18. Light 21 incident from the third surface 16 of the first prism 12 is totally reflected by the second surface 15 of the first prism 12 and enters the light valve 5 from an oblique direction. Light 22 reflected as a projected image travels perpendicular to light valve 5. The lights 23 and 24 reflected as unnecessary light travel at an angle different from that of the light 22, but the light 24 is reflected by the third surface 19 of the second prism 13 and travels to the projection lens side, and The light 23 exits directly from the second surface 18 of the second prism 13 without being reflected by the third surface 19 of the second prism 13.
[0005]
[Patent Document 1]
JP 2000-010045 A
[0006]
[Problems to be solved by the invention]
However, when the total reflection prism 6 having the above-described conventional configuration and shown in FIG. 12 is used, the total reflection surface (the second surface of the first prism 12) 15 of the total reflection prism 6 is connected to the optical axis (and light) of the projection lens 7. (The normal line of the valve 5). Generally, the reflection at the optical interface increases as the incident angle increases. In the optical system shown in FIG. 11, since the principal ray of the light 22 reflected as the image forming light by the light valve 5 passes through the optical interfaces 15 and 17 at a relatively large incident angle, the reflection on this surface is large. Antireflection treatment at these optical interfaces is required.
[0007]
FIG. 13 shows characteristics of a general five-layer antireflection film. The vertical axis indicates the reflectance, and the horizontal axis indicates the wavelength of the light. Condition A is a case where the incident angle is 0 degree, and condition B is a case where the incident angle is 56.5 degrees. As the incident angle increases, the antireflection band becomes narrower, and the reflectivity increases. Therefore, the transmittance of the projection optical system decreases.
[0008]
Therefore, in the conventional total reflection prism 6, the transmittance of the entire optical system is reduced due to the decrease in transmittance at the interface sandwiching the air layer and the narrowing of the transmission band. However, there is a problem that the image quality is significantly degraded, for example, the contrast is reduced due to the generation of unnecessary reflected light, and the color purity is reduced due to the narrower transmission band and the generation of unnecessary reflected light.
[0009]
The present invention has been made in consideration of the above-described conventional problems, and has improved a transmission characteristic, and as a result, a prism device capable of realizing a high-quality image with good contrast, and a projection device using the prism device. It is an object to provide a display device, a rear projector, and a multi-vision system.
[0010]
[Means for Solving the Problems]
To achieve the above object, a first prism device of the present invention includes a light valve, and a first prism and a second prism provided in this order from the light valve side, wherein the first prism and the second prism are air. A first surface proximate to the light valve; a second surface forming the air layer between the second prism; and a third surface on which light is incident. And the second prism has a first surface that forms the air layer between the first prism and the first prism, the reflected light from the light valve being emitted, and the first prism having the first surface. A second surface substantially parallel to a surface, and a third surface, wherein at least one of the second surface of the first prism and the first surface of the second prism is smaller than a wavelength of incident light. It has a periodic structure of pitch.
[0011]
A second prism device according to the present invention includes a light valve, a first prism, a second prism, and a bonded transparent plate, and the first prism, the bonded transparent plate, in order from the light valve side. The second prism is disposed, and the bonded transparent plate is formed by joining a first transparent substrate and a second transparent substrate having substantially the same refractive index as the first and second prisms with an air layer interposed therebetween. The first prism and the first transparent substrate, the second prism and the second transparent substrate are respectively bonded by a transparent adhesive, and the first prism is a second substrate that is close to the light valve. One surface, a second surface joined to the first transparent substrate, and a third surface on which light is incident, wherein the second prism is a first surface joined to the second transparent substrate. And the reaction from the light valve A surface from which light is emitted and which has a second surface substantially parallel to the first surface of the first prism and a third surface, and which is in contact with the air layer of the first transparent substrate and the second transparent substrate. Has a periodic structure with a pitch smaller than the wavelength of the incident light.
[0012]
A third prism device of the present invention includes a light valve, and a first prism, a second prism, and a third prism provided in this order from the light valve side, wherein the first prism, the second prism, and The second prism and the third prism are coupled to each other with an air layer interposed therebetween, and the first prism forms the air layer between a first surface adjacent to the light valve and the second prism. A second surface, and a third surface on which the reflected light from the light valve is incident, wherein the second prism forms the air layer between the first prism and the first surface; A second surface forming the air layer between the third prism and a third surface on which light is incident, wherein the third prism forms the air layer between the third prism and the second prism; First surface and reflection from the light valve Has a second surface substantially parallel to the first surface of the first prism, and a third surface, wherein the second surface of the first prism and the first surface of the second prism And at least one of the second surface of the second prism and the first surface of the third prism has a periodic structure with a pitch smaller than the wavelength of incident light.
[0013]
A fourth prism device of the present invention includes a light valve, a first prism, a second prism, a third prism, a first bonded transparent plate, and a second bonded transparent plate, The first prism, the first bonded transparent plate, the second prism, the second bonded transparent plate, and the third prism are arranged in this order from the side, and the first and second bonded transparent plates are arranged. A first transparent substrate and a second transparent substrate, each having a refractive index substantially equal to that of the first to third prisms, are coupled with an air layer interposed therebetween, and each of the transparent substrates is adjacent to the transparent substrate. The prism is bonded with a transparent adhesive, and the first prism is bonded to a first surface adjacent to the light valve and a first transparent substrate of the first bonded transparent plate. Surface and the light valve A second surface of the first bonded transparent plate, which is joined to the second transparent substrate, and a second surface of the second bonded transparent plate, A second surface joined to the first transparent substrate, and a third surface on which light is incident. The third prism is joined to the second transparent substrate of the second bonded transparent plate. A first surface, a second surface substantially parallel to the first surface of the first prism from which reflected light from the light valve is emitted, and a third surface, wherein the first bonding is performed. At least one of the first and second transparent substrates of the transparent plate and the surface of the second bonded transparent plate in contact with the air layer of the first and second transparent substrates is smaller than the wavelength of the incident light. It has a periodic structure of pitch.
[0014]
Next, a projection display device of the present invention includes any one of the first to fourth prism devices of the present invention, a light source, and a projection lens, and light from the light source is incident on the prism device. After being modulated by the light valve, the light exits the prism device and is projected by the projection lens.
[0015]
Further, the rear projector of the present invention includes the projection display device of the present invention, a mirror that bends light projected from the projection display device, and a transmission type that transmits and scatters the projected light to display an image. At least a screen.
[0016]
Further, the multi-vision system of the present invention includes a plurality of the projection display devices of the invention, a plurality of transmissive screens corresponding one-to-one with the projection display devices, and a plurality of the projection display devices. And video signal supply means for supplying
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
The first to fourth prism devices of the present invention have a periodic structure with a pitch smaller than the wavelength of incident light on at least one of the two opposing surfaces forming an air layer between adjacent prisms. Here, when the wavelength of the incident light has a width, the pitch of the periodic structure needs to be smaller than the lower limit wavelength value of the wavelength band of the incident light. In addition, the pitch of the periodic structure means a pitch in the densest arrangement direction when the periodic structure is configured by a two-dimensional array of many fine structures.
[0018]
Thus, the first light incident at an incident angle equal to or greater than the critical angle is incident at an incident angle relatively smaller than the first light while maintaining the total reflection characteristic at the interface with the air layer. With respect to the second light (image forming light), the reflection at the interface can be suppressed over almost the entire wavelength band of the incident light. As a result, it is possible to provide a prism device with improved transmission characteristics of the second light. Therefore, by configuring an image display device using such a prism device, it is possible to realize bright, high-contrast image display with good contrast.
[0019]
In the first and second prism devices of the present invention, the incident angle of the illumination light when incident on the light valve from the air is θ0, and the incident light is incident on the prism at the incident angle θ0 from the air. The refraction angle in the prism is θ1, the critical angle in the prism is θ2, the angle between the second surface and the third surface of the first prism is θ3, and the first surface of the second prism is Assuming that the angle formed by the second surface is θ4 and the refractive index of the prism is n, it is preferable that the following formulas (1) to (4) are satisfied.
[0020]
n · sin θ1 = sin θ0 (1)
sin θ2 = 1 / n (2)
θ3 = θ1 / 2 + θ2 (3)
θ4 = θ2−θ1 / 2 (4)
Thus, the image forming light can be efficiently emitted from the second surface of the second prism.
[0021]
In the third and fourth prism devices of the present invention, the incident angle of the illumination light when entering the light valve from the air is θ0, and when the light beam enters the prism from the air at the incident angle θ0. The refraction angle in the prism is θ1, the critical angle in the prism is θ2, the angle between the second surface and the third surface of the second prism is θ3, and the first surface of the third prism is The angle formed by the second surface is θ4, the angle of light emitted from the light valve in air is θ5, the angle formed between the first surface of the first prism and the second surface is θ6, Assuming that the refractive index of the prism is n, it is preferable that the following expressions (5) to (9) are satisfied.
[0022]
n · sin θ1 = sin θ0 (5)
sin θ2 = 1 / n (6)
θ3 = θ1 / 2 + θ2 (7)
θ4 = θ2−θ1 / 2 (8)
θ6 ≧ θ2−θ5 (9)
Thus, the image forming light can be efficiently emitted from the second surface of the third prism. Further, it is possible to prevent unnecessary light from being totally reflected and entering the second and third prisms.
[0023]
In the third and fourth prism devices of the present invention, it is preferable that a light absorbing means is provided on the third surface of the first prism. Thereby, the unnecessary light can be absorbed by the light absorbing means.
[0024]
Alternatively, in the third and fourth prism devices of the present invention, it is preferable that the third surface of the first prism is a polished surface or a mirror surface. Thereby, unnecessary light can be emitted from the third surface of the first prism to the outside of the prism device.
[0025]
In the first to fourth prism devices of the present invention, the light valve is a reflection type, and is a spatial light modulation element that forms an image by controlling a traveling direction of light for each pixel according to a video signal. Is preferred. Accordingly, only the image forming light can be guided in a predetermined direction, and application to the image forming apparatus is facilitated.
[0026]
In the first to fourth prism devices of the present invention, a thin film made of a metal or a dielectric is formed outside two optically effective areas opposed to the air layer, and the thin film has a thickness of the air layer. It is preferable to regulate the height. This makes it possible to easily and accurately control the thickness of the air layer and the parallelism between the two opposing surfaces forming the air layer, thereby providing a prism device with highly stable optical characteristics.
[0027]
In the first to fourth prism devices of the present invention, it is preferable that the thin film is made of magnesium fluoride, silicon dioxide, or titanium dioxide. These materials are versatile and have the same properties as glass as a substrate on which they are formed, and are therefore advantageous in terms of temperature expansion, durability, and the like.
[0028]
In the first to fourth prism devices of the present invention, it is preferable that the periodic structure has a pitch equal to or less than half the wavelength of the incident light. Thereby, the dependence of the transmission / reflection characteristics at the interface with the air layer on the incident angle and the wavelength can be further reduced, and the light transmission characteristics are improved.
[0029]
In the first to fourth prism devices of the present invention, it is preferable that the periodic structure has a height of at least one time, more preferably at least three times the pitch. Thereby, the light transmission characteristics are further improved.
[0030]
In the first to fourth prism devices of the present invention, it is preferable that one unit constituting the periodic structure is a cone. As a result, the refractive index continuously changes at the air interface, so that a uniform transmission characteristic can be obtained even for a light beam having a spread.
[0031]
In the first to fourth prism devices of the present invention, it is preferable that a bottom surface of one unit constituting the periodic structure is a substantially regular hexagon. Accordingly, the periodic structure can be arranged at a high filling rate, so that the light transmission characteristics are further improved.
[0032]
In the first to fourth prism devices of the present invention, the lower limit of the wavelength band of the incident light is preferably 400 nm, more preferably 430 nm, and particularly preferably 450 nm. Thereby, good transmission characteristics can be obtained over almost the entire visible light band.
[0033]
Next, a projection display device of the present invention includes any one of the first to fourth prism devices of the present invention, a light source, and a projection lens, and light from the light source is incident on the prism device. After being modulated by the light valve, the light exits the prism device and is projected by the projection lens. As a result, it is possible to realize high-quality image display that is bright and has good contrast.
[0034]
The above-mentioned projection type display device of the present invention further comprises a time-division color separation unit in which the light from the light source is incident, and the light is time-limited to three colors of blue, green, and red and emitted, and the light valve is It is preferable to form an optical image according to the color of incident light. As a result, a high-quality color image can be displayed.
[0035]
Further, the rear projector according to the present invention includes the projection display device according to the present invention, a mirror that bends light projected from the projection display device, and a transmission type device that transmits and scatters the projected light to display an image. At least a screen. As a result, it is possible to realize high-quality image display that is bright and has good contrast.
[0036]
Further, the multi-vision system of the present invention includes a plurality of the projection display devices of the invention, a plurality of transmissive screens corresponding one-to-one with the projection display devices, and a plurality of video signals to the projection display devices. And video signal supply means for supplying As a result, it is possible to realize a high-quality image display that is bright, has good contrast, and has a large screen.
[0037]
In the above-described multi-vision system of the present invention, the video signal supply unit divides a video signal of one image, and supplies the divided different video signals to a plurality of the projection display devices, respectively. The single image may be displayed on the entire transmission screen. As a result, one large screen can be formed by a plurality of transmissive screens, and high-quality image display that is bright, has good contrast, and has excellent display quality uniformity over the entire screen can be realized.
[0038]
Hereinafter, embodiments of the present invention will be described with reference to FIGS.
[0039]
(Embodiment 1)
FIG. 1 shows the configuration of a prism device according to Embodiment 1 of the present invention. The configuration and operation of this embodiment will be described with reference to FIG.
[0040]
In the figure, reference numeral 31 denotes a spatial light modulator as a light valve, and reference numeral 44 denotes a total reflection prism.
[0041]
The spatial light modulator 31 is, for example, a digital mirror device in which a large number of pixels are arrayed and formed on an optical image plane, and each pixel is provided with a reflection mirror capable of independently changing the tilt angle according to a video signal. Of the illumination light 36 incident on the spatial light modulator 31, the light incident on the pixel on which an image is formed is reflected along an optical axis 43 parallel to the normal direction of the optical image plane of the spatial light modulator 31 to form an image. Light that has entered a pixel that does not contribute is reflected as unnecessary light 45 in a direction different from the optical axis 43.
[0042]
The total reflection prism 44 is composed of two triangular prisms of a first prism 32 and a second prism 33 in order from the spatial light modulation element 31 side. A thin air layer 35 is formed between the prisms 32 and 33. Each of the prisms 32 and 33 is made of optical glass and has a refractive index of 1.516.
[0043]
The first prism 32 forms an air layer 35 between the first surface 34 close to the spatial light modulator 31 and the second prism 33, and totally reflects the illumination light 36 to the spatial light modulator 31. It has a second surface 37 for incidence at a refraction angle θ1 in the prism, and a third surface 38 on which illumination light 36 enters from the outside.
[0044]
The second prism 33 has a first surface 39 forming an air layer 35 between the first prism 32 and a second surface 39 from which the image forming light 40 reflected by the spatial light modulation element 31 and passing through the air layer 35 is emitted. It has a surface 41 and a third surface 42.
[0045]
The first prism 32 is configured so that the incident light 36 is obliquely incident on the spatial light modulator 31 and that the principal ray of the reflected light 40 used as a projection image is parallel to the optical axis 43 perpendicular to the spatial light modulator 31. Have been.
[0046]
Since the total reflection prism 44 as a whole is a plane parallel in the direction of the projection optical axis 43, the first surface 34 of the first prism 32 and the second surface 41 of the second prism 33 are optical images of the spatial light modulator 31 respectively. Parallel to the plane.
[0047]
The third surface 42 of the second prism 33 is substantially parallel to the principal ray direction of the unnecessary light 45 from the spatial light modulator 31 so that the unnecessary light 45 from the spatial light modulator 31 is not absorbed or reflected.
[0048]
Here, the effective area of the second surface 37 of the first prism 32 and the first surface 39 of the second prism 33 has a period smaller than the wavelength of the light beam emitted from the spatial light modulator 31 and incident on these surfaces. A group of minute projections (periodic structure) is formed. Specifically, as shown in FIG. 2, a fine projection group having a pitch p1 and a height h1 is formed.
[0049]
Each projection is a cone having a pitch p1 of 250 nm or less and a height h1 of 750 nm. These cones are formed by repeatedly exposing and developing the resist layer on the resist applied on the base material using an electron beam exposure method. Thereby, a group of minute cones having a periodic structure as shown in FIG. 2 can be formed on the surfaces 37 and 39.
[0050]
By forming such a periodic structure including a microstructure having a pitch p1 equal to or smaller than the wavelength used, the apparent refractive index of incident light can be changed continuously, and the incident angle dependence and the wavelength dependence can be improved. It is possible to form an anti-reflection function surface having low property, and the reflectance is reduced. However, when light is incident from a medium with a high refractive index to a medium with a low refractive index, the surface having such a minute periodic structure is totally anti-reflective when the incident angle is larger than the critical angle. Is the same as in the case where is not applied.
[0051]
The illumination light 36 incident on the first prism 32 is totally reflected by the second surface 37 of the first prism 32 and is incident on the light valve 31. The light passes through the second surface 37 and the first surface 39 of the second prism 33 and exits the total reflection prism 44. At this time, due to such a periodic structure, the image forming light 40 is not reduced by reflection at the surfaces 37 and 39 which are interfaces with the air layer 35 in almost all wavelength bands. Thereby, a bright image with good color reproducibility can be obtained.
[0052]
The periodic fine structure may have a pitch p1 equal to or less than the wavelength of the incident light (hereinafter, “used wavelength”). It is more preferable that the pitch p1 is equal to or less than 使用 of the used wavelength, since the incident angle dependency and the wavelength dependency at the interface can be further reduced and the light transmission characteristics are improved. Further, the height h1 of the microstructure is preferably at least the pitch p1, more preferably at least three times the pitch p1. The higher the height h1 is, the more the light transmission characteristics are improved.
[0053]
The shape of the microstructure, which is one unit constituting the periodic structure, is not limited to a conical shape as shown in FIG. 2, but may be a cylindrical shape as shown in FIG. The shape may be a simple pyramid. Alternatively, it may be a shape similar to a pyramid in which the cross-sectional shape in the height direction passing through the central axis is substantially sinusoidal. However, if the microstructure is a cone or a shape similar to the cone, it is more desirable because the refractive index changes continuously at the air interface.
[0054]
It is preferable that the distance between adjacent microstructures is small. This is because the plane portion between the adjacent microstructures has the same reflection characteristics as in the related art. In addition, the bottom shape of the microstructure may be any of a circle, an ellipse, a quadrangle, a hexagon, a polygon such as a triangle, and the like. Since the maximum value is obtained, the effect of suppressing reflection of incident light is further improved.
[0055]
Either structure has the same effect on transmitted light as the refractive index changes very gently on the surface where the periodic structure is formed, so that reflection is reduced. Such a periodic microstructure serves as an antireflection means having a wider band than an ordinary antireflection film and having a small incident angle dependence.
[0056]
The spacing (the thickness of the air layer 35) between the second surface 37 of the first prism 32 and the first surface 39 of the second prism 33 is regulated by spacers 45 and 46 and fixed. The spacers 45 and 46 are thin films made of metal or dielectric formed by vapor deposition. The spacers 45 and 46 do not need to be provided outside the optically effective area of the second surface 37 of the first prism 32 and the first surface 39 of the second prism 33, and may be formed at four corners. In the present embodiment, the spacers 45 and 46 are made of a dielectric film formed by a vapor deposition method, and the distance between the second surface 37 of the first prism 32 and the first surface 39 of the second prism 33 is about 5 μm. It is.
[0057]
When the spacers 45 and 46 are formed, the optically effective area is shielded so that a metal or a dielectric does not adhere to the area where the periodic structure is formed. The spacers 45 and 46 formed at the four corners are thin films having a uniform thickness. Usually, in the deposition of an optical thin film, the thickness accuracy is on the order of several nm, and the error is extremely small. As a result, an air layer 35 with extremely high parallelism can be formed.
[0058]
As a material for forming the spacer layers 45 and 46, a material having stable characteristics and inexpensiveness is preferable. In particular, silicon dioxide, titanium dioxide, and magnesium fluoride are often used when depositing an antireflection film. It is advantageous in terms of temperature expansion, durability and the like because it has properties and is equivalent to the glass as the substrate.
[0059]
Here, assuming that the refractive index of the first prism 32 and the second prism 33 is n, the incident angle of the illumination light 36 to the spatial light modulator 31 in the air is θ0, and the refraction angle in the prism is θ1, Equation (1) holds.
[0060]
(Equation 10)
n · sin θ1 = sin θ0 (1)
[0061]
The critical angle θ2 at which the illumination light traveling in the first prism 32 is totally reflected at the interface with the air (the second surface 37 of the first prism 32) can be expressed by the following equation (2). I can do it.
[0062]
[Equation 11]
sin θ2 = 1 / n (2)
[0063]
The angle θ3 formed between the second surface 37 and the third surface 38 of the first prism 32 is such that the illumination light 36 is totally reflected by the second surface 37 and is directed toward the spatial light modulation element 31 at a refraction angle θ1 in the prism. In order to proceed, it is necessary to satisfy the following conditional expression (3).
[0064]
(Equation 12)
θ3 = θ1 / 2 + θ2 (3)
[0065]
Further, the angle θ4 between the first surface 39 and the second surface 41 of the second prism 33 is determined by setting the second surface 41 from which the image forming light 40 is emitted to the optical image surface of the spatial light modulator 31 and the first prism 32. In order to be parallel to the first surface 34, it is necessary to satisfy the following conditional expression (4).
[0066]
(Equation 13)
θ4 = θ2−θ1 / 2 (4)
[0067]
An antireflection film made of a dielectric multilayer film is formed on the first surface 34 and the third surface 38 of the first prism 32 and on the second surface 41 of the second prism 33. The antireflection film is composed of three layers or five or more layers so that reflection can be reduced over the entire visible light band of 400 to 700 nm. Titanium dioxide, magnesium fluoride, silicon dioxide, aluminum oxide, zirconium oxide, or the like is used as the material of the multilayer film. The vapor deposition is usually performed so as to form a thickness of about 1 nm per second. The incident angles of the light rays incident on the surfaces 34, 38 and 41 are small, and a normal antireflection film is sufficiently effective. Depending on the cost, an antireflection structure using the above-mentioned periodic structure smaller than the wavelength of the incident light may be used.
[0068]
According to the present embodiment, a compact total reflection prism 44 with improved transmission characteristics of image forming light can be realized.
[0069]
(Embodiment 2)
FIG. 4 shows a configuration of a prism device according to Embodiment 2 of the present invention. The configuration and operation of this embodiment will be described with reference to FIG.
[0070]
In the figure, reference numeral 51 denotes a spatial light modulator as a light valve, and 66 denotes a total reflection prism.
[0071]
The spatial light modulation element 51 is, for example, a digital mirror device in which a large number of pixels are arrayed and formed on an optical image plane, and each pixel is provided with a reflection mirror capable of independently changing an inclination angle according to a video signal. Of the illumination light 61 incident on the spatial light modulation element 51, light incident on a pixel on which an image is formed is reflected along an optical axis 70 parallel to the normal direction of the optical image plane of the spatial light modulation element 51 to form an image. The light incident on the pixels that do not contribute is reflected as unnecessary light 69 in a direction different from the optical axis 70.
[0072]
The total reflection prism 66 includes a first prism 52, a bonded transparent plate 67, and a second prism 53 in this order from the spatial light modulation element 51 side. The prisms 52 and 53 and the bonded transparent plate 67 are all made of optical glass, and have a refractive index of 1.516.
[0073]
The laminated transparent plate 67 is formed by joining two first and second transparent substrates 55 and 56 with spacers 57 and 58 interposed therebetween, and the spacers 57 and 58 reduce the surface interval between the transparent substrates 55 and 56. A regulated thin air layer 59 is formed.
[0074]
The first prism 52 has a first surface 54 close to the spatial light modulator 51, a second surface 60 bonded to a first transparent substrate 55 forming a bonded transparent plate 67, and illumination light 61 incident from the outside. And a third surface 62. The first prism 52 and the first transparent substrate 55 are joined by a transparent adhesive.
[0075]
The second prism 53 emits image forming light 65 reflected by the spatial light modulator 51 and passing through the air layer 59, and a first surface 68 joined to the second transparent substrate 56 forming the bonded transparent plate 67. A second surface 63 and a third surface 64. The second prism 53 and the second transparent substrate 56 are joined by a transparent adhesive.
[0076]
The first prism 52 and the first transparent substrate 55 make the incident light 61 obliquely enter the spatial light modulator 51, and the principal ray of the reflected light 65 used as a projection image is parallel to the optical axis 70 perpendicular to the spatial modulator 51. It is configured to be.
[0077]
Since the total reflection prism 66 as a whole is a plane parallel to the projection optical axis 70, the first surface 54 of the first prism 52 and the second surface 63 of the second prism 53 are optical images of the spatial light modulator 51, respectively. Parallel to the plane.
[0078]
The third surface 64 of the second prism 53 is substantially parallel to the principal ray direction of the unnecessary light 69 from the spatial light modulator 51 so that the unnecessary light 69 from the spatial light modulator 51 is not absorbed or reflected.
[0079]
In the effective area on the surface of the first and second transparent substrates 55 and 56 on the interface side with the air layer 59, the period has a period smaller than the wavelength of light emitted from the spatial light modulator 51 and incident on these surfaces. A fine projection group (periodic structure) similar to that described in the first embodiment is formed. Specifically, as shown in FIG. 2, a fine projection group having a pitch p1 and a height h1 is formed.
[0080]
Each projection is a cone having a pitch p1 of 250 nm or less and a height h1 of 300 nm. As in the first embodiment, the projections are formed on the resist applied on the base material by an electron beam exposure method or the like.
[0081]
By forming such a periodic structure including a microstructure having a pitch p1 equal to or smaller than the wavelength used, the apparent refractive index of incident light can be changed continuously, and the incident angle dependence and the wavelength dependence can be improved. It is possible to form an anti-reflection function surface having low property, and the reflectance is reduced. However, when light is incident from a medium with a high refractive index to a medium with a low refractive index, the surface having such a minute periodic structure is totally anti-reflective when the incident angle is larger than the critical angle. Is the same as in the case where is not applied.
[0082]
The illumination light 61 incident on the first prism 52 is totally reflected at the interface between the first transparent substrate 55 and the air layer 59 and is incident on the light valve 51, and the image forming light 65 reflected there is applied to the first transparent substrate 55. The light passes through 55 and the second transparent substrate 56 and exits from the total reflection prism 66. At this time, the image forming light 65 is not reduced by the reflection at the interface with the air layer 59 in almost the entire wavelength band due to such a periodic structure. Thereby, a bright image with good color reproducibility can be obtained.
[0083]
The periodic fine structure may have a pitch p1 equal to or less than the wavelength of the incident light (hereinafter, “used wavelength”). It is more preferable that the pitch p1 is equal to or less than 使用 of the used wavelength, since the incident angle dependency and the wavelength dependency at the interface can be further reduced and the light transmission characteristics are improved. Further, the height h1 of the microstructure is preferably at least the pitch p1, more preferably at least three times the pitch p1. The higher the height h1 is, the more the light transmission characteristics are improved.
[0084]
The shape of the microstructure, which is one unit constituting the periodic structure, is not limited to a conical shape as shown in FIG. 2, but may be a cylindrical shape as shown in FIG. The shape may be a simple pyramid. Alternatively, it may be a shape similar to a pyramid in which the cross-sectional shape in the height direction passing through the central axis is substantially sinusoidal. However, if the microstructure is a cone or a shape similar to the cone, it is more desirable because the refractive index changes continuously at the air interface.
[0085]
It is preferable that the distance between adjacent microstructures is small. This is because the plane portion between the adjacent microstructures has the same reflection characteristics as in the related art. In addition, the bottom shape of the microstructure may be any of a circle, an ellipse, a quadrangle, a hexagon, a polygon such as a triangle, and the like. Since the maximum value is obtained, the effect of suppressing reflection of incident light is further improved.
[0086]
Either structure has the same effect on transmitted light as the refractive index changes very gently on the surface where the periodic structure is formed, so that reflection is reduced. Such a periodic microstructure serves as an antireflection means having a wider band than an ordinary antireflection film and having a small incident angle dependence.
[0087]
The spacers 57, 58 for forming the thin air layer 59 of the bonded transparent plate 67 are thin films made of metal or dielectric formed by vapor deposition. The spacers 57 and 58 need not be provided on the entire surface of the two transparent substrates 55 and 56 on the air layer 59 side outside the optically effective area, and may be formed at four corners. In the present embodiment, the spacers 57 and 58 are made of a dielectric film formed by a vapor deposition method, and the spacing between the transparent substrates 55 and 56 is about 5 μm.
[0088]
As in the first embodiment, it is preferable that the spacers 57 and 58 be formed in a state where the optically effective area is shielded, and a highly accurate spacer can be realized by the vapor deposition method.
[0089]
Each angle condition in the total reflection prism 66 preferably satisfies Expressions (1) to (4), as in the first embodiment.
[0090]
On the first surface 54 and the third surface 62 of the first prism 52 and on the second surface 63 of the second prism 53, an antireflection film made of a dielectric multilayer film is formed. The antireflection film is composed of three layers or five or more layers so that reflection can be reduced over the entire visible light band of 400 to 700 nm. Titanium dioxide, magnesium fluoride, silicon dioxide, aluminum oxide, zirconium oxide, or the like is used as the material of the multilayer film. The vapor deposition is usually performed so as to form a thickness of about 1 nm per second. The incident angles of the light beams incident on the surfaces 54, 62, 63 are small, and a normal antireflection film is sufficiently effective. Depending on the cost, an antireflection structure using the above-mentioned periodic structure smaller than the wavelength of the incident light may be used.
[0091]
According to the present embodiment, as in the first embodiment, a compact total reflection prism 66 with improved transmission characteristics of image forming light can be realized. Further, since the periodic structure is not formed directly on the first and second prisms but on the transparent substrates 55 and 56, a thin air layer having a high antireflection effect can be formed easily and at low cost.
[0092]
(Embodiment 3)
FIG. 5 shows the configuration of a prism device according to Embodiment 3 of the present invention. The configuration and operation of this embodiment will be described with reference to FIG.
[0093]
In the figure, reference numeral 81 denotes a spatial light modulator as a light valve, and 101 denotes a total reflection prism.
[0094]
The spatial light modulator 81 is, for example, a digital mirror device in which a large number of pixels are arrayed and formed on an optical image plane, and each pixel is provided with a reflection mirror capable of independently changing an inclination angle according to a video signal. Of the illumination light 96 incident on the spatial light modulator 81, the light incident on the image forming pixel is reflected along an optical axis parallel to the normal direction of the optical image plane of the spatial light modulator 81 (image forming light 97). Light incident on pixels that do not contribute to image formation is reflected as unnecessary light 98 in a direction different from that of image formation light 97.
[0095]
The total reflection prism 101 includes three triangular prisms of a first prism 82, a second prism 83, and a third prism 84 in this order from the spatial light modulation element 81 side. Thin air layers 94 and 95 are formed between the prisms 82 and 83 and between the prisms 83 and 84, respectively. The material of each of the prisms 82, 83, 84 is optical glass, and the refractive index is 1.516.
[0096]
The first prism 82 forms an air layer 94 between the first surface 85 near the spatial light modulator 31 and the second prism 83, and transmits the image forming light 97 reflected by the spatial light modulator 81. A second surface 86 that totally reflects unnecessary light 98 that is transmitted and reflected at an angle θ5 with respect to the principal ray of the image forming light 97, and a third surface 87 on which the unnecessary light 98 reflected by the second surface 86 is incident And
[0097]
The second prism 83 forms an air layer 95 between a first surface 88 forming an air layer 94 between the first prism 82 and the third prism 84, transmits image forming light 97, and illuminates. It has a second surface 89 for totally reflecting the light 96 and entering the spatial light modulator 81 at a refraction angle θ1 in the prism, and a third surface 90 on which the illumination light 96 is incident from the outside.
[0098]
The third prism 84 has a first surface 91 that forms an air layer 95 between itself and the second prism 83, a second surface 92 from which image forming light 97 reflected from the spatial light modulator 81 is emitted, and a second surface 92. It has a third surface 93 perpendicular to the surface 92.
[0099]
The second prism 83 is configured so that the incident light 96 is obliquely incident on the spatial light modulator 81 and that the principal ray of the reflected light 97 used as a projection image is parallel to an optical axis perpendicular to the spatial light modulator 81. ing.
[0100]
Further, the first prism 82 has a function of totally reflecting the unnecessary light 98 from the spatial light modulator 81 on the second surface 86 thereof, and preventing the unnecessary light 98 from traveling to the projection lens and the screen side.
[0101]
Since the total reflection prism 101 as a whole is a plane parallel to the direction of the projection optical axis, the first surface 85 of the first prism 82 and the second surface 92 of the third prism 84 correspond to the optical image surface of the spatial light modulator 81, respectively. Parallel.
[0102]
The effective surfaces of the second surface 86 of the first prism, the first surface 88 of the second prism 83, the second surface 89 of the second prism 83, and the first surface 91 of the third prism 84, which form the thin air layers 94 and 95, respectively. In the region, a group of minute projections (periodic structure) similar to that described in the first embodiment and having a period smaller than the wavelength of the light beam incident on these surfaces is formed.
[0103]
By forming such a periodic structure including a microstructure having a pitch p1 equal to or smaller than the wavelength used, the apparent refractive index of incident light can be changed continuously, and the incident angle dependence and the wavelength dependence can be improved. It is possible to form an anti-reflection function surface having low property, and the reflectance is reduced. However, when light is incident from a medium with a high refractive index to a medium with a low refractive index, the surface having such a minute periodic structure is totally anti-reflective when the incident angle is larger than the critical angle. Is the same as in the case where is not applied.
[0104]
The illumination light 96 incident on the second prism 83 is totally reflected by the second surface 89 of the second prism 83, and then passes through the first surface 88 of the second prism 83 and the second surface 86 of the first prism 82 to be illuminated. The image forming light 97 that is incident on the bulb 81 and reflected here is subjected to the second surface 86 of the first prism 82, the first surface 88 of the second prism 83, the second surface 89 of the second prism 83, and the third prism. The light passes through the first surface 91 at a large incident angle and exits the total reflection prism 101. At this time, due to such a periodic structure, the image forming light 97 is not reduced by reflection at the interface with the air layers 94 and 95 in almost the entire wavelength band. Thereby, a bright image with good color reproducibility can be obtained.
[0105]
The periodic fine structure may have a pitch p1 equal to or less than the wavelength of the incident light (hereinafter, “used wavelength”). It is more preferable that the pitch p1 is equal to or less than 使用 of the used wavelength, since the incident angle dependency and the wavelength dependency at the interface can be further reduced and the light transmission characteristics are improved. Further, the height h1 of the microstructure is preferably at least the pitch p1, more preferably at least three times the pitch p1. The higher the height h1 is, the more the light transmission characteristics are improved.
[0106]
The shape of the microstructure, which is one unit constituting the periodic structure, is not limited to a conical shape as shown in FIG. 2, but may be a cylindrical shape as shown in FIG. The shape may be a simple pyramid. Alternatively, it may be a shape similar to a pyramid in which the cross-sectional shape in the height direction passing through the central axis is substantially sinusoidal. However, if the microstructure is a cone or a shape similar to the cone, it is more desirable because the refractive index changes continuously at the air interface.
[0107]
It is preferable that the distance between adjacent microstructures is small. This is because the plane portion between the adjacent microstructures has the same reflection characteristics as in the related art. In addition, the bottom shape of the microstructure may be any of a circle, an ellipse, a quadrangle, a hexagon, a polygon such as a triangle, and the like. Since the maximum value is obtained, the effect of suppressing reflection of incident light is further improved.
[0108]
Either structure has the same effect on transmitted light as the refractive index changes very gently on the surface where the periodic structure is formed, so that reflection is reduced. Such a periodic microstructure serves as an antireflection means having a wider band than an ordinary antireflection film and having a small incident angle dependence.
[0109]
The second surface 86 of the first prism 82 and the first surface 88 of the second prism 83 are separated by spacers 102 and 103, and the second surface 89 of the second prism 83 and the first surface of the third prism 84 are separated. The space 91 (the thickness of the air layers 94 and 95) is fixed to the surface 91 by spacers 104 and 105, respectively. The spacers 102 and 103 and the spacers 104 and 105 are thin films made of metal or dielectric formed by vapor deposition. In the present embodiment, the spacing between the surfaces forming the air layers 94 and 95 is about 5 μm.
[0110]
The spacers 102, 103, 104, and 105 form a second surface 86 of the first prism 82, a first surface 88 of the second prism 83, a second surface 89 of the second prism 83, and a first surface 91 of the third prism 84, respectively. Need not be provided on the entire area outside the optically effective area, and may be formed at four corners.
[0111]
When the spacers 102, 103, 104, and 105 are formed, the optically effective area is shielded so that a metal or dielectric does not adhere to the area where the periodic structure is formed. The spacers 102, 103, 104, and 105 formed at the four corners are thin films having a uniform thickness. Normally, in the deposition of an optical thin film, the thickness accuracy is on the order of several nm, the error is extremely small, and as a result, the air layers 94 and 95 having extremely high parallelism can be formed.
[0112]
Here, the refractive index of the first prism 82, the second prism 83, and the third prism 84 is n, the incident angle of the illumination light 96 to the spatial light modulator 81 in air is θ0, and the refractive angle of the prism is θ1. Then, the following equation (5) holds.
[0113]
[Equation 14]
n · sin θ1 = sin θ0 (5)
[0114]
The critical angle θ2 at which the illumination light 96 traveling in the second prism 83 is totally reflected at the interface with the air (the second surface 89 of the second prism 83) can be expressed by the following equation (6). I can do it.
[0115]
(Equation 15)
sin θ2 = 1 / n (6)
[0116]
The angle θ3 between the second surface 89 and the third surface 90 of the second prism 83 is such that the illumination light 96 is totally reflected by the second surface 89 and is directed toward the spatial light modulator 81 at the refraction angle θ1 in the prism. In order to proceed, it is necessary to satisfy the following conditional expression (7).
[0117]
(Equation 16)
θ3 = θ1 / 2 + θ2 (7)
[0118]
Further, the angle θ4 formed between the first surface 91 and the second surface 92 of the third prism 84 is such that the second surface 92 from which the image forming light 97 is emitted is the optical image surface of the spatial light modulator 81 and the first prism 82. In order to be parallel to the first surface 85, it is necessary to satisfy the following conditional expression (8).
[0119]
[Equation 17]
θ4 = θ2−θ1 / 2 (8)
[0120]
In order for the unnecessary light 98 reflected at the refraction angle θ5 in the prism to be totally reflected by the second surface 86 of the first prism 82, the first surface 85 and the second surface 86 of the first prism 82 form. The angle θ6 needs to satisfy the following conditional expression (9).
[0121]
(Equation 18)
θ6 ≧ θ2−θ5 (9)
[0122]
If Expression (9) is satisfied, the unnecessary light 98 is totally reflected by the second surface 86 and enters the third surface 87. The third surface 87 is a polished surface, and a black paint is applied to the interface with air as light absorbing means. Therefore, most of the unnecessary light 98 is absorbed here.
[0123]
When light absorbing paint is applied to the outer surface of the prism, the reflectance is low when the angle of incidence on the boundary is small, but the reflectance is high when the angle of incidence is large and the light is incident almost parallel to the boundary. Is considerably higher. In the case of the total reflection prism 101 shown in FIG. 5, the reflectance is low because the unnecessary light 98 emitted from the spatial light modulation element 81 is incident on the third surface 87 of the first prism 82 at a small incident angle. Therefore, most of the unnecessary light 98 is absorbed by the black paint and does not reach the screen.
[0124]
According to the present embodiment, it is possible to realize a total reflection prism in which the transmission characteristics of the image forming light are improved and the unnecessary light 98 does not travel toward the screen at all.
[0125]
(Embodiment 4)
FIG. 6 shows the configuration of a prism device according to Embodiment 4 of the present invention, and the configuration and operation of this embodiment will be described with reference to FIG.
[0126]
In the figure, 111 is a spatial light modulator as a light valve, and 140 is a total reflection prism.
[0127]
The spatial light modulator 111 is, for example, a digital mirror device in which a large number of pixels are arrayed and formed on an optical image plane, and each pixel is provided with a reflection mirror capable of independently changing an inclination angle according to a video signal. Of the illumination light 132 incident on the spatial light modulation element 111, light incident on a pixel on which an image is formed is reflected along an optical axis parallel to a normal direction of an optical image plane of the spatial light modulation element 111 (image forming light 133). ), The light incident on the pixels that do not contribute to the image formation is reflected as unnecessary light 135 in a direction different from the image forming light 133.
[0128]
The total reflection prism 131 includes a first prism 112, a first bonded transparent plate 127, a second prism 113, a second bonded transparent plate 131, and a third prism 114 arranged in this order from the spatial light modulator 111 side. . The materials of the prisms 112, 113, 114 and the bonded transparent plates 127, 131 are all optical glass, and the refractive index is 1.516.
[0129]
The first bonded transparent plate 127 is formed by bonding two first and second transparent substrates 124 and 125 with spacers 136 and 137 therebetween, and the spacers 136 and 137 provide a surface between the transparent substrates 124 and 125. The gap is regulated to form a thin air layer 126. Similarly, the second bonded transparent plate 131 is formed by joining two first and second transparent substrates 128 and 129 with spacers 138 and 139 interposed therebetween, and the transparent substrates 128 and 129 are formed by the spacers 138 and 139. The thin air layer 130 is formed with the interplanar spacing restricted.
[0130]
The first prism 112 is joined to the first surface 115 close to the spatial light modulator 111 and the first transparent substrate 124 forming the first bonded transparent plate 127, and forms an image reflected by the spatial light modulator 111. It has a second surface 116 that transmits the light 133 and a third surface 117 on which unnecessary light 123 from the spatial light modulator 111 enters.
[0131]
The second prism 113 is bonded to a first surface 118 that is bonded to a second transparent substrate 125 that forms the first bonded transparent plate 127, and is bonded to a first transparent substrate 128 that forms the second bonded transparent plate 131. , A second surface 119 through which the image forming light 97 is transmitted, and a third surface 120 on which the illumination light 132 is incident from the outside.
[0132]
The third prism 114 has a first surface 121 bonded to a second transparent substrate 129 forming a second bonded transparent plate 131 and a second surface from which the image forming light 133 reflected from the spatial light modulator 111 is emitted. It has a surface 122 and a third surface 123 perpendicular to the second surface 122.
[0133]
The second prism 113 and the first transparent substrate 128 of the second bonded transparent plate 131 allow the incident light 132 to be obliquely incident on the spatial light modulator 111, and the principal ray of the reflected light 133 used as a projected image is changed by the spatial light modulator. It is configured to be parallel to an optical axis perpendicular to 111.
[0134]
Further, the first prism 112 and the first transparent substrate 124 of the first bonded transparent plate 127 have a function of totally reflecting the unnecessary light 135 from the spatial light modulator 111 and preventing the unnecessary light 135 from traveling to the projection lens and the screen side.
[0135]
Since the total reflection prism 140 as a whole is a plane parallel in the projection optical axis direction, the first surface 115 of the first prism 112 and the second surface 112 of the third prism 114 are respectively located on the optical image surface of the spatial light modulator 111. Parallel.
[0136]
The surface of the first bonded transparent plate 127 forming the thin air layers 126 and 130 on the interface side of the first transparent substrate 124 and the second transparent substrate 125 with the air layer 126, and the first bonded transparent plate 131 of the second bonded transparent plate 131 Each effective area on the surface of the transparent substrate 128 and the second transparent substrate 129 on the interface side with the air layer 130 has a period smaller than the wavelength of light rays incident on these surfaces, as described in the first embodiment. A similar minute projection group (periodic structure) is formed.
[0137]
By forming such a periodic structure including a microstructure having a pitch p1 equal to or smaller than the wavelength used, the apparent refractive index of incident light can be changed continuously, and the incident angle dependence and the wavelength dependence can be improved. It is possible to form an anti-reflection function surface having low property, and the reflectance is reduced. However, when light is incident from a medium with a high refractive index to a medium with a low refractive index, the surface having such a minute periodic structure is totally anti-reflective when the incident angle is larger than the critical angle. Is the same as in the case where is not applied.
[0138]
After the illumination light 132 incident on the second prism 113 is totally reflected at the air interface of the first transparent substrate 128 of the second bonded transparent plate 131, the second transparent substrate 125 and the first transparent substrate 127 of the first bonded transparent plate 127 are reflected. After passing through the transparent substrate 124 and being incident on the light valve 111, the image forming light 133 reflected there is applied to the first transparent substrate 124 and the second transparent substrate 125 of the first bonded transparent plate 127, and the second bonded transparent plate 127. The light passes through the first transparent substrate 128 and the second transparent substrate 129 of the plate 131 in order at a large incident angle and exits the total reflection prism 140. At this time, due to such a periodic structure, the image forming light 133 is not reduced by reflection at the interface with the air layers 126 and 130 in almost all wavelength bands. Thereby, a bright image with good color reproducibility can be obtained.
[0139]
The periodic fine structure may have a pitch p1 equal to or less than the wavelength of the incident light (hereinafter, “used wavelength”). It is more preferable that the pitch p1 is equal to or less than 使用 of the used wavelength, since the incident angle dependency and the wavelength dependency at the interface can be further reduced and the light transmission characteristics are improved. Further, the height h1 of the microstructure is preferably at least the pitch p1, more preferably at least three times the pitch p1. The higher the height h1 is, the more the light transmission characteristics are improved.
[0140]
The shape of the microstructure, which is one unit constituting the periodic structure, is not limited to a conical shape as shown in FIG. 2, but may be a cylindrical shape as shown in FIG. The shape may be a simple pyramid. Alternatively, it may be a shape similar to a pyramid in which the cross-sectional shape in the height direction passing through the central axis is substantially sinusoidal. However, if the microstructure is a cone or a shape similar to the cone, it is more desirable because the refractive index changes continuously at the air interface.
[0141]
It is preferable that the distance between adjacent microstructures is small. This is because the plane portion between the adjacent microstructures has the same reflection characteristics as in the related art. In addition, the bottom shape of the microstructure may be any of a circle, an ellipse, a quadrangle, a hexagon, a polygon such as a triangle, and the like. Since the maximum value is obtained, the effect of suppressing reflection of incident light is further improved.
[0142]
Either structure has the same effect on transmitted light as the refractive index changes very gently on the surface where the periodic structure is formed, so that reflection is reduced. Such a periodic microstructure serves as an antireflection means having a wider band than an ordinary antireflection film and having a small incident angle dependence.
[0143]
The first and second transparent substrates 124 and 125 forming the first bonded transparent plate 127 are formed by spacers 136 and 137, and the first and second transparent substrates 128 and 129 forming the second bonded transparent plate 131 are formed by the spacers 136 and 137. Spaces (thicknesses of the air layers 126 and 130) are regulated and fixed by the spacers 138 and 139, respectively. The spacers 136 and 137 and the spacers 138 and 139 are thin films made of metal or dielectric formed by vapor deposition. In the present embodiment, the spacing between the surfaces forming the air layers 126 and 130 is about 5 μm.
[0144]
The spacers 136, 137, 138, and 139 form first and second transparent substrates 124 and 125 forming the first bonded transparent plate 127 and first and second transparent substrates 128 forming the second bonded transparent plate 131, respectively. , 129 need not be provided on the entire surface outside the optically effective area on the air layer side, but may be formed at four corners.
[0145]
When the spacers 136, 137, 138, and 139 are formed, the optically effective area is shielded so that a metal or a dielectric does not adhere to the area where the periodic structure is formed. The spacers 136, 137, 138, and 139 formed at the four corners are thin films having a uniform thickness. Normally, in the deposition of an optical thin film, the thickness accuracy is on the order of several nm, the error is extremely small, and as a result, the air layers 126 and 130 with extremely high parallelism can be formed.
[0146]
Each angle condition in the total reflection prism 140 preferably satisfies Expressions (5) to (9), as in the third embodiment.
[0147]
The third surface 117 of the first prism 112 is a polished smooth surface or a mirror surface. Therefore, the unnecessary light 135 totally reflected at the air interface of the first transparent substrate 124 of the first bonded transparent plate 127 and incident on the third surface 117 of the first prism 112 passes therethrough and goes out of the total reflection prism 140. Emit. Therefore, the unnecessary light 135 does not reach the screen.
[0148]
According to the present embodiment, it is possible to realize a total reflection prism in which the transmission characteristics of the image forming light are improved and the unnecessary light 135 does not travel toward the screen at all. In addition, since the periodic structure is not formed directly on the first to third prisms but is formed on a transparent substrate, a thin air layer having a high antireflection effect can be easily and inexpensively formed.
[0149]
(Embodiment 5)
Next, a projection type display device according to a fifth embodiment using the prism device of the present invention is shown in FIG.
[0150]
As shown in FIG. 7, the projection display device according to the fifth embodiment includes at least a projection lens 161, a prism device 162, and a light source 163.
[0151]
The light source 163 includes a lamp 165 and a concave mirror 166. The light from the lamp 165 disposed at the first focal point f1 of the concave mirror 166 is reflected by the concave mirror 166 and is efficiently condensed on the second focal point f2, and then passes through the condenser lens 167, the reflection mirror 168, and the field lens 169. After that, the light enters the prism device 162.
[0152]
The prism device 162 is the prism device described in the first embodiment and configured by the total reflection prism 44 and the spatial light modulation element 31. Light incident on the prism device 162 is reflected by the total reflection surface of the total reflection prism 44 and illuminates the spatial light modulator 31. In the present embodiment, a DMD is used as the spatial modulation element 31. The spatial light modulator 31 is driven by a video signal to form an optical image. The optical image on the spatial modulation element 31 is illuminated by light emitted from the light source 163, and the direction of reflected light is controlled for each pixel. The image forming light 40 enters the projection lens 161, and an optical image is enlarged and projected on a screen (not shown).
[0153]
In addition, the prism device 162 is not limited to the one described in the first embodiment, and may be any of the prism devices described in the second to fourth embodiments.
[0154]
According to the projection display apparatus of the fifth embodiment, by using the above-described prism apparatus of the present invention, the transmission characteristics of image forming light are good, and unnecessary light does not enter the projection lens. High-quality image display with good contrast can be performed.
[0155]
(Embodiment 6)
Next, a projection display according to a sixth embodiment using the prism device of the present invention is shown in FIG.
[0156]
As shown in FIG. 8A, the projection display device according to the sixth embodiment includes at least a projection lens 161, a prism device 172, and a light source 173, as in the fifth embodiment. However, the projection display device according to the sixth embodiment differs from the projection display device according to the fifth embodiment in that the light from the light source 173 is temporally limited to three colors of blue, green, and red. A time-division color separation unit 190 for transmitting the light through the light source, and an illumination optical system 178 for uniformly illuminating the effective display area of the spatial light modulator 111. The lamp 175 of the light source 173 emits white light. The same components as those in FIG. 7 showing the fifth embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0157]
The light source 173 includes a lamp 175 and a concave mirror 176. White light from the lamp 175 arranged at the first focal point f1 of the concave mirror 176 is reflected by the concave mirror 176 and is efficiently collected on the second focal point f2.
[0158]
A color wheel is disposed near the second focal point f2 as the time-division color separation unit 190. As shown in FIG. 8B, the color wheel 190 has three fan-shaped color filters having the same central angle, and each color filter has a red (R), green (G), and blue (B) color filter, respectively. Transmits colored light. A disc-shaped color wheel 190 provided with three color filters is rotated at high speed about a central axis 191 by a motor (not shown) such as a motor.
[0159]
As a result, the white light from the light source 173 is color-separated into three colors of blue, green, and red by the time-division color separation means 190 at regular time intervals, passes therethrough, and enters the illumination optical system 178.
[0160]
The illumination optical system 178 is for efficiently equalizing the light beam from the light source 173, and the condenser lens 179, the first lens array 180, the second lens array 181, and the relay lens 182 They are arranged in order.
[0161]
Light that has passed through the color wheel 190 is converted by the condenser lens 179 into substantially parallel light. The converted substantially parallel light enters the first lens array 180. The first lens array 180 is composed of a plurality of lens elements having positive power arranged on a plane, and each of the plurality of lens elements having positive power has substantially the same shape as the effective display area of the spatial light modulator 111. It has a similar opening.
[0162]
The second lens array 181 is also formed of a plurality of positive power lens elements arranged on a plane similarly to the first lens array 180. Therefore, the substantially parallel light incident on the first lens array 180 is divided by the plurality of lens elements constituting the first lens array 180 to form the second lens array 181 corresponding to the lens elements one-to-one. An illuminant image is formed on each of the lens elements.
[0163]
A plurality of light beams emitted from each lens element constituting the second lens array 181 pass through the relay lens 182, are reflected by the reflection mirror 168, pass through the field lens 169, and enter the prism device 172.
[0164]
The prism device 172 is the prism device described in the fourth embodiment and includes the total reflection prism 140 and the spatial light modulator 111. Light incident on the prism device 172 is reflected by the total reflection surface of the total reflection prism 140 and illuminates the spatial light modulator 111. At this time, a plurality of light beams emitted from each lens element of the second lens array 181 are superimposed on the effective display area of the spatial light modulator 111. Thus, the effective display area of the spatial light modulator 111 is uniformly illuminated.
[0165]
In the present embodiment, a DMD is used as spatial modulation element 111. The spatial light modulator 111 is driven by a video signal corresponding to the color of incident light to form an optical image. The optical image on the spatial modulation element 111 is illuminated by light emitted from the light source 173, and the direction of reflected light is controlled for each pixel. The image forming light 133 enters the projection lens 161, and an optical image is enlarged and projected on a screen (not shown).
[0166]
The spatial modulation element 111 is illuminated with each of the red, green and blue color lights generated by the time-division color separation means 190 and switched at high speed in time, and the video signal for driving the spatial modulation element 111 is switched in accordance with the switching timing of the incoming color light. Thereby, a full-color enlarged projection image can be formed on the screen.
[0167]
According to the projection display device of the sixth embodiment, by using the above-described prism device of the present invention, the image forming light has good transmission characteristics, and unnecessary light does not enter the projection lens. A high-quality color image with good contrast can be displayed.
[0168]
The prism device 172 is not limited to the one described in the fourth embodiment, and may be any of the prism devices described in the first to third embodiments.
[0169]
Further, in the sixth embodiment, the white light source 173 and the time-division color separation unit 190 are used to illuminate the spatial light modulator 111 with color light that switches to blue, green, and red at regular time intervals, thereby expanding the full color. Although projection is realized, the present invention is not limited to this. For example, a full-color image can also be formed by using three light sources that emit a single color of blue, green, and red as the light sources and sequentially illuminating the spatial light modulator 111 with the light emission time of each light source being switched at regular intervals. Examples of such a light source include a light source using a high-brightness LED and a laser.
[0170]
(Embodiment 7)
Next, a rear projector according to Embodiment 7 of the present invention will be described with reference to the drawings. FIG. 9 is a configuration diagram of a rear projector according to the seventh embodiment of the present invention.
[0171]
As shown in FIG. 9, the rear projector according to the seventh embodiment includes a projection display device 201, a mirror 202 that bends light projected from a projection lens included in the projection display device 201, and a projected light. And a screen 203 for displaying an image by transmitting and scattering light. Reference numeral 204 denotes a housing for housing components. The projection display device 201 is the same as that described in Embodiment 5 or 6.
[0172]
The image light projected from the projection display device 201 is reflected by the mirror 202 and forms an image on the transmission screen 203.
[0173]
In the seventh embodiment, since the enlarged image reflected by the mirror 202 is projected on the transmissive screen 203, the depth and height of the set can be reduced, and a compact set can be realized.
[0174]
In addition, since the projection display device described in Embodiment 5 or 6 is used as the projection display device 201, it is brighter, has better contrast, and has higher image quality than a projection display device using a conventional prism device. Can be obtained.
[0175]
(Embodiment 8)
Next, a multi-vision system according to a twelfth embodiment of the present invention will be described with reference to the drawings. FIG. 10 is a configuration diagram of the multi-vision system according to the eighth embodiment of the present invention.
[0176]
As shown in FIG. 10, the multi-vision system according to the eighth embodiment includes a plurality of projection display devices 211 and a plurality of transmission screens provided in one-to-one correspondence with each projection display device 211. 212 and video signal supply means 214 for supplying a video signal to each projection display device 211. Reference numeral 213 denotes a housing for housing the plurality of projection display devices 211 and the plurality of transmission screens 212. The projection display device 212 is similar to that shown in the fifth or sixth embodiment.
[0177]
The video signal supply unit 214 has a function of dividing a video signal for displaying one image and supplying different divided video signals to each projection display device 211. This function is achieved by a video division circuit provided in the video signal supply unit 214. Therefore, in the multivision system according to the eighth embodiment, the video signal of one image is divided by the video division circuit and sent to the plurality of projection display devices 211, and the image projected from each projection display device 211 is transmitted. Is imaged on the transmission screen 212 to form a single image as a whole.
[0178]
As described above, according to the multi-vision system according to the eighth embodiment, it is possible to realize high-quality image display that is bright, has good contrast, and has a large screen.
[0179]
Further, in the multi-vision system according to the seventh embodiment, the video signal supply unit 214 can supply video signals of mutually different and different images to the respective projection display devices 211. In this case, different images can be displayed on the respective transmissive screens 212, and various information can be displayed at the same time.
[0180]
In the multivision system according to the eighth embodiment, a sensor for detecting light output and color reproducibility at the start of lighting of each transmissive screen 212 may be attached to the housing 213. Thereby, the video signal supply unit 214 can process the luminance and chromaticity of the signal distributed to each projection display device 211 according to the light output and the color reproducibility at the start of lighting of each transmission screen 212. it can. Thus, even on a large screen including a plurality of transmissive screens 212, it is possible to obtain a display that is bright, has good contrast, and has excellent uniformity of display quality over the entire screen.
[0181]
In the first to fourth embodiments, the periodic structure is formed on both of the two opposing surfaces forming the air layer, but the present invention is not limited to this. Even if only one of them is used, the above-described effect of improving the transmission characteristics can be obtained although the effect is inferior.
[0182]
In the first to fourth embodiments, the DMD is used as the light valve, but the present invention is not limited to this. Any light valve having an element capable of independently controlling the traveling direction of light between the ON state and the OFF state in each pixel can be used.
[0183]
In the first to fourth embodiments, the thin film formed by vapor deposition is used as the spacer for regulating the thickness of the air layer, but the present invention is not limited to this. For example, the thickness of the air layer may be regulated by interposing minute spherical beads between two opposing surfaces.
[0184]
【The invention's effect】
As is apparent from the above description, according to the prism device of the present invention, the total reflection characteristic at the interface with the air layer is maintained for the first light incident at an incident angle equal to or greater than the critical angle. However, for the second light (image forming light) incident at a relatively smaller incident angle than the first light, the reflection at the interface can be suppressed over almost the entire wavelength band of the incident light. it can. As a result, it is possible to provide a prism device with improved transmission characteristics of the second light. Therefore, by configuring an image display device using such a prism device, it is possible to realize bright, high-contrast image display with good contrast.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a configuration of a prism device according to Embodiment 1 of the present invention.
FIG. 2 is a perspective view schematically showing an example of a periodic structure provided in the prism device shown in FIG.
3A is a perspective view schematically showing another periodic structure provided in the prism device shown in FIG. 1. FIG. 3B is a further periodic structure provided in the prism device shown in FIG. Perspective view showing the outline of
FIG. 4 is a schematic diagram showing a configuration of a prism device according to a second embodiment of the present invention.
FIG. 5 is a schematic diagram showing a configuration of a prism device according to Embodiment 3 of the present invention.
FIG. 6 is a schematic diagram showing a configuration of a prism device according to a fourth embodiment of the present invention.
FIG. 7 is a schematic configuration diagram of a projection display apparatus according to Embodiment 5 of the present invention.
FIG. 8A is a schematic configuration diagram of a projection display apparatus according to Embodiment 6 of the present invention.
FIG. 8B is a front view showing a schematic configuration of a time-division color separation unit included in a projection display according to Embodiment 6 of the present invention.
FIG. 9 is a schematic configuration diagram of a rear projector according to a seventh embodiment of the present invention.
FIG. 10 is a schematic configuration diagram of a multi-vision system according to an eighth embodiment of the present invention.
FIG. 11 is a schematic configuration diagram of an example of a conventional projection display device.
FIG. 12 is a schematic configuration diagram showing an example of a conventional prism device.
FIG. 13 is a diagram showing the reflection characteristics of a general five-layer antireflection film.
[Explanation of symbols]
31 Light Bulb
32 1st prism
33 2nd prism
35 air layer
36 Illumination light
44 Total reflection prism

Claims (22)

A light valve, and a first prism and a second prism provided in order from the light valve side;
The first prism and the second prism are coupled with an air layer interposed therebetween,
The first prism has a first surface close to the light valve, a second surface forming the air layer between the second prism, and a third surface on which light is incident.
The second prism has a first surface on which the air layer is formed between the first prism and the first prism, and the reflected light from the light valve is emitted, and is substantially parallel to the first surface of the first prism. It has a second surface and a third surface,
A prism device, wherein at least one of the second surface of the first prism and the first surface of the second prism has a periodic structure with a pitch smaller than the wavelength of incident light. A light valve, a first prism, a second prism, and a laminated transparent plate;
In order from the light valve side, the first prism, the bonded transparent plate, and the second prism are arranged,
The bonded transparent plate is formed by bonding a first transparent substrate and a second transparent substrate having substantially the same refractive index as the first and second prisms with an air layer interposed therebetween.
The first prism and the first transparent substrate, the second prism and the second transparent substrate are respectively bonded with a transparent adhesive,
The first prism has a first surface close to the light valve, a second surface bonded to the first transparent substrate, and a third surface on which light is incident,
The second prism has a first surface bonded to the second transparent substrate, and a second surface that emits reflected light from the light valve and is substantially parallel to the first surface of the first prism. , A third surface,
A prism device, wherein at least one of the first transparent substrate and the second transparent substrate in contact with the air layer has a periodic structure with a pitch smaller than the wavelength of incident light. The incident angle of the illumination light when incident on the light valve from the air is θ0, the refraction angle in the prism when the light beam is incident on the prism at the incident angle θ0 from the air is θ1, The critical angle is θ2, the angle between the second surface and the third surface of the first prism is θ3, the angle between the first surface and the second surface of the second prism is θ4, the angle of the prism is The prism device according to claim 1, wherein the following condition is satisfied, where n is a refractive index.

A light valve, and a first prism, a second prism, and a third prism provided in order from the light valve side;
The first prism and the second prism, and the second prism and the third prism are respectively coupled via an air layer,
The first prism has a first surface adjacent to the light valve, a second surface forming the air layer between the second prism, and a third surface on which light reflected from the light valve is incident. Has,
The second prism has a first surface forming the air layer between the first prism and the second prism, a second surface forming the air layer between the third prism, and a third surface on which light is incident. Surface and
The third prism has a first surface forming the air layer between the second prism and the first prism, and the reflected light from the light valve is emitted, and is substantially parallel to the first surface of the first prism. It has a second surface and a third surface,
Incident light is incident on at least one of the second surface of the first prism, the first surface of the second prism, the second surface of the second prism, and the first surface of the third prism. A periodic structure having a pitch smaller than the wavelength of the prism device. A light valve, a first prism, a second prism, a third prism, a first bonded transparent plate, and a second bonded transparent plate;
In order from the light valve side, the first prism, the first bonded transparent plate, the second prism, the second bonded transparent plate, and the third prism are arranged,
The first and second bonded transparent plates are each formed by combining a first transparent substrate and a second transparent substrate having substantially the same refractive index as the first to third prisms with an air layer interposed therebetween,
Each of the transparent substrates and the prism adjacent thereto are bonded with a transparent adhesive,
The first prism has a first surface proximate to the light valve, a second surface of the first bonded transparent plate joined to the first transparent substrate, and reflected light from the light valve incident thereon. A third surface,
The second prism is a first surface of the first bonded transparent plate bonded to the second transparent substrate, and a second surface of the second bonded transparent plate bonded to the first transparent substrate. And a third surface on which light is incident,
The third prism includes a first surface of the second bonded transparent plate joined to the second transparent substrate, a light beam emitted from the light valve, and a first surface of the first prism. A second surface substantially parallel to and a third surface,
The light is incident on at least one of the first and second transparent substrates of the first bonded transparent plate and the surface of the first and second transparent substrates of the second bonded transparent plate which is in contact with the air layer. A prism device having a periodic structure with a pitch smaller than the wavelength of light. The incident angle of the illumination light when incident on the light valve from the air is θ0, the refraction angle in the prism when the light beam is incident on the prism at the incident angle θ0 from the air is θ1, The critical angle is θ2, the angle between the second surface and the third surface of the second prism is θ3, the angle between the first surface and the second surface of the third prism is θ4, The following condition is satisfied, assuming that the emission angle of the light beam emitted from the air in the air is θ5, the angle between the first surface and the second surface of the first prism is θ6, and the refractive index of the prism is n. The prism device according to claim 4 or 5, wherein:

The prism device according to claim 4, further comprising a light absorbing unit on the third surface of the first prism. The prism device according to claim 4, wherein the third surface of the first prism is a polished surface or a mirror surface. The prism device according to 1, 2, 4, or 5, wherein the light valve is a reflection type, and is a spatial light modulation element that forms an image by controlling a traveling direction of light for each pixel according to a video signal. 6. A thin film made of a metal or a dielectric is formed outside two opposing optically effective areas in contact with the air layer, and the thin film regulates the thickness of the air layer. The prism device according to item 1. The prism device according to claim 10, wherein the thin film is made of magnesium fluoride, silicon dioxide, or titanium dioxide. The prism device according to claim 1, 2, 4, or 5, wherein the periodic structure has a pitch equal to or less than half the wavelength of the incident light. The prism device according to claim 1, 2, 4, or 5, wherein the periodic structure has a height that is at least one time the pitch thereof. The prism device according to claim 1, wherein the periodic structure has a height that is at least three times the pitch. The prism device according to claim 1, wherein one unit constituting the periodic structure is a cone. The prism device according to claim 1, 2, 4, or 5, wherein a bottom shape of one unit constituting the periodic structure is a substantially regular hexagon. The prism device according to claim 1, 2, 4, or 5, wherein a lower limit value of a wavelength band of the incident light is 400 nm. A prism device according to any one of claims 1 to 17, a light source, and a projection lens.
A projection display device in which light from the light source enters the prism device, is modulated by the light valve, exits the prism device, and is projected by the projection lens. Further provided is a time-division color separation unit in which light from the light source enters, and is time-limited to three colors of blue, green, and red and emitted.
19. The projection display device according to claim 18, wherein the light valve forms an optical image according to a color of incident light. 20. At least a projection type display device according to claim 18 or 19, a mirror for bending light projected from the projection type display device, and a transmission type screen for displaying an image by transmitting and scattering the projected light. Rear projector. 20. A plurality of projection display devices according to claim 18 or 19, a plurality of transmissive screens corresponding one-to-one with the projection display devices, and a video signal supply for supplying video signals to the plurality of projection display devices. And a multi-vision system comprising: The video signal supply unit divides a video signal of one image, and supplies each of the divided different video signals to the plurality of projection display devices. 22. The multi-vision system according to claim 21 for displaying.

Images