JP2012078640A - Color synthesis unit and projection type display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color synthesis unit and a projection type display device using the color synthesis unit which stably synthesize three kinds of light having different wavelengths with high light use efficiency.SOLUTION: A color synthesis unit includes a wavelength selection type modulation element 20 having a first wavelength plate 22, a dichroic mirror 23, and a second wavelength plate 24 in this order, and a polarization beam splitter 30. The wavelength selection type modulation element 20 reflects blue light 35B to change the polarization state and allows green light 35G to pass therethrough, and the polarization beam splitter 30 allows the blue light 35B to pass therethrough and reflects blue light 36B, and reflects the green light 35G, and furthermore allows red light 35R to pass therethrough, thereby emitting light of each color incident from different directions in the same direction.

Description

  The present invention relates to a color composition unit that synthesizes three types of light having different wavelengths, and a projection display device using the color composition unit.

  In a projection display device that displays a projected image on a screen, such as a data projector or a rear projection television receiver, red light and green light traveling in different optical paths as light in three different wavelength bands In addition, color synthesizing means for synthesizing blue light into the same optical path is used.

  As this color synthesizing means, for example, it is reported that a cube-shaped synthesizing prism having two reflecting surfaces with wavelength selectivity is used to provide an optical action to match the emission directions of light of each color incident from three directions. (Patent Document 1).

  FIG. 11 is a schematic diagram showing the combining prism 200 and its optical action. The combining prism 200 is configured such that the reflecting surface 201 and the reflecting surface 202 intersect at a right angle. Here, the red light 205R is incident on the combining prism 200 in the Z direction, the green light 205G is incident on the X direction, and the blue light 205B is incident on the −Z direction. Here, the reflecting surface 201 reflects the red light 205R and transmits the green light 205G and the blue light 205B. The reflecting surface 202 reflects the blue light 205B and transmits the red light 205R and the green light 205G. Accordingly, the red light 205R, the green light 205G, and the blue light 205B are combined and emitted so as to travel in the X direction.

  As another color synthesizing means, a wavelength synthesizing prism is constituted by using three triangular prisms, and a dielectric multilayer film having a reflection characteristic is formed on two triangular prisms among them. It has been reported that an optical action that matches the emission directions of light of each color incident from three directions is given (Patent Document 2).

  FIG. 12 is a schematic diagram showing the wavelength synthesizing prism 210 and its optical action. The wavelength synthesizing prism 210 is composed of triangular prisms 211, 212, and 213. The triangular prism 211 is formed with a dielectric multilayer film 211a, and the triangular prism 212 is formed with a dielectric multilayer film 212a. Here, the dielectric multilayer film 211a reflects the blue light 215B and transmits the red light 215R and the green light 215G. The dielectric multilayer film 212a reflects the red light 215R and transmits the green light 215G. Thus, the red light 215R, the green light 215G, and the blue light 215B are combined and emitted so as to travel in the X direction.

Japanese Patent Laid-Open No. 10-269802 JP 2004-70018 A

  However, in the composite prism 200 of Patent Document 1, if there is a variation such as a displacement of the joining position due to joining of the prisms provided with the optical multilayer films constituting the reflecting surfaces 201 and 202, light is transmitted to the optical multilayer film. It has been difficult to obtain stable characteristics because it is incident once or a region where no incidence is made. In addition, since the joint portions of the prisms are all processed at a right angle, there is a problem that stable optical characteristics cannot be obtained even when slight mechanical damage occurs particularly in this portion.

  In the wavelength combining prism 210 of Patent Document 2, among the three triangular prisms, the triangular prisms 211 and 212 reflect the light depending on the incident angle of light other than the surfaces of the optical multilayer films 211a and 212a. Has a surface. For this reason, there has been a problem that, when processing variations of at least the triangular prisms 211 and 212 and deviation of the adjustment of the optical axis occur, deviation of the incident angle occurs and stable optical characteristics cannot be obtained.

  The present invention has been made to solve such a problem of the prior art, and realizes a color synthesis unit that synthesizes light of three different wavelength bands with a configuration capable of obtaining stable optical characteristics. An object of the present invention is to provide a projection display device with high reliability by using a synthesis unit.

The present invention has been made in view of the above points, and the light in the first wavelength band λ ₁ , the light in the second wavelength band λ ₂ , and the light in the third wavelength band λ ₃ are different from each other. A color combining unit that is incident from different directions and emits in the same direction. The color combining unit includes a wavelength selective modulation element and a polarization beam splitter, and the wavelength selective modulation element includes: 1 wave plate, a dichroic mirror, and a second wave plate are provided in this order, and the first wave plate and the second wave plate are adapted to transmit light in the _first wavelength band λ ₁ . The dichroic mirror reflects the light in the _first wavelength band λ ₁ and transmits the light in the _second wavelength band λ _2. polarization beam splitter, one of the first wavelength band lambda ₁ light, the While reflecting the linearly polarized light of transmitted light of a second linear polarization orthogonal to the light of the first linear polarization, and at least said one of said second wavelength band lambda ₂ light first And the light of the third wavelength band λ ₃ is transmitted, or at least the light of the second linear polarization is transmitted among the light of the _second wavelength band λ _2. In addition, a color synthesizing unit that reflects the light in the third wavelength band λ ₃ is provided.

The light of the first wavelength band λ ₁ is incident on the polarization beam splitter and the wavelength selective modulation element in this order, and the light of the _second wavelength band λ ₂ is the wavelength selective modulation element, The color combining unit is provided in the order of the polarization beam splitter, and the light of the _third wavelength band λ ₃ is incident only on the polarization beam splitter.

The light in the _first wavelength band λ ₁ , the light in the second wavelength band λ ₂ , and the light in the third wavelength band λ ₃ that are emitted in the same direction are all of the first linearly polarized light. There is provided the above-described color synthesis unit which is light or both are light of the second linearly polarized light.

  In addition, the first wave plate and the second wave plate are made of the same birefringent material and have the same thickness, and the slow axis direction of the first wave plate and the second wave plate Provided is the above-described color synthesis unit arranged so that the slow axis direction of the wave plate is substantially orthogonal.

The light in the first wavelength band λ ₁ is blue light, the light in the second wavelength band λ ₂ is green light, and the light in the third wavelength band λ ₃ is red light. Provides a color composition unit.

  A light source that emits at least blue light, green light, and red light; a plurality of light valves that modulate the blue light, the green light, and the red light according to an image to be displayed; and a projection lens unit that projects the image. And a projection type display device comprising the color composition unit in an optical path between the plurality of light valves and the projection lens unit.

  Furthermore, a light source that emits at least blue light, green light, and red light, a reflective liquid crystal element that modulates the blue light, the green light, and the red light according to an image to be displayed, and a projection lens unit that projects an image And a color combining unit described above in the optical path between the light source and the reflective liquid crystal element.

  The present invention can realize an effect that a stable optical characteristic can be obtained by a configuration of a color synthesis unit that synthesizes and emits three types of light incident with different traveling directions and wavelengths. In addition, the projection display device of the present invention using the color synthesis unit can also realize an effect of obtaining stable image display characteristics.

Cross-sectional schematic diagram of color composition unit (first embodiment) (A) Optical characteristics for red light and green light in the color synthesis unit (b) Optical characteristics for blue light in the color synthesis unit Cross-sectional schematic diagram of color composition unit (second embodiment) (A) Optical characteristics for red light and green light in the color synthesis unit (b) Optical characteristics for blue light in the color synthesis unit Configuration example 1 of a projection display device Configuration example 2 of a projection display device Configuration example 3 of a projection display device Configuration example 4 of a projection display device Optical characteristics of dichroic mirrors Optical properties of polarizing beam splitters. Conventional synthetic prism Conventional wavelength synthesis prism

(First Embodiment of Color Composition Unit)
FIG. 1 is a schematic diagram illustrating a configuration of a color synthesis unit 10 according to the present embodiment, and includes a wavelength selective modulation element 20 and a polarization beam splitter 30. In FIG. 1, the color synthesis unit 10 shows the wavelength selective modulation element 20 and the polarization beam splitter 30 separately, but they may be configured integrally. In the wavelength selective modulation element 20, the first wave plate 22, the dichroic mirror 23, the second wave plate 24, and the transparent substrate 21b are arranged in this order on the transparent substrate 21a and in parallel with the surface of the transparent substrate 21a. Has been. The transparent substrate 21a may be expressed as a first transparent substrate, and the transparent substrate 21b may be expressed as a second transparent substrate. Further, the wavelength selective modulation element 20 may not include one or both of the transparent substrate 21a and the transparent substrate 21b. Further, a transparent material such as a transparent substrate or an adhesive (not shown) may be provided between the first wave plate 22 and the dichroic mirror 23 and between the dichroic mirror 23 and the second wave plate 24.

As long as the transparent substrates 21a and 21b are transparent to incident light, various materials such as a resin plate and a resin film can be used. However, when an optically isotropic material such as glass or quartz glass is used, This is preferable because the transmitted light is not affected by birefringence. Further, for example, if the transparent substrates 21a and 21b are provided with an antireflection film made of a multilayer film at the interface with air, light reflection loss due to Fresnel reflection can be reduced. The first wave plate 22 and the second wave plate 24 are made of a birefringent material and have a modulation function for changing the polarization state of incident light. The first wave plate 22 and the second wave plate 24 are made of, for example, a birefringent material having an optical axis parallel to a surface perpendicular to the direction in which light is incident, and the optical axis is aligned in the thickness direction. In addition, a plurality of layers may be stacked so that the optical axes intersect. In addition, one or a plurality of wave plates whose optical axis directions are spiraled about the thickness direction may be configured. Examples of the material of the first wave plate 22 and the second wave plate include an inorganic material such as quartz and LiNbO ₃ and an organic material such as resin, liquid crystal, and polymer liquid crystal. In addition, it is preferable that the 1st wave plate 22 and the 2nd wave plate 24 are the combination used as the optical characteristic which cancels the function which modulates the incident light so that it may mention later.

The dichroic mirror 23 is formed with an optical multilayer film in parallel with the surface of the first wave plate 22 and transmits light of one of two incident light having different wavelengths. And has a wavelength selective reflection function of reflecting light of the other wavelength. In particular, the case where incident light is incident from a direction substantially perpendicular to the surface of the dichroic mirror 23 is considered here. The dichroic mirror 23 in the color synthesis unit 10 according to the present embodiment reflects light in the 450 nm wavelength band that is blue light and transmits light in the 510 nm wavelength band that is green light. The 450 nm wavelength band is a wavelength range of 420 to 470 nm or a wavelength range of 435 to 465 nm, and the 510 nm wavelength band is a wavelength range of 480 to 560 nm or a wavelength range of 495 to 525 nm. As the material of the optical multilayer film, inorganic materials and organic materials such as SiO ₂ , SiON, ZrO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , TiO ₂ , Al ₂ O ₃ , and MgF ₂ can be used.

Next, the polarization beam splitter 30 will be described. In the polarizing beam splitter 30, two triangular prisms are joined so as to sandwich the optical multilayer film 31, and in particular, the surface of the optical multilayer film 31 forms an angle of about 45 ° with respect to the plane of the transparent substrate 21a. Placed in. Further, as the material of the optical multilayer film 31, an inorganic material or an organic material such as SiO ₂ , SiON, ZrO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , TiO ₂ , Al ₂ O ₃ , or MgF ₂ may be used. it can. Further, as will be described later, the polarization beam splitter 30 has a function in which the transmittance / reflectance differs depending on the polarization state and the transmittance / reflectance varies depending on the wavelength of incident light.

  Next, the optical action of the color synthesis unit 10 will be described. The color synthesis unit 10 according to the present embodiment uses light of a 450 nm wavelength band that becomes blue light, light of a 510 nm wavelength band that becomes green light, and light of a 630 nm wavelength band that becomes red light. The 630 nm wavelength band is a wavelength range of 610 to 670 nm or a wavelength range of 615 to 645 nm. 2 (a) and 2 (b) are schematic diagrams showing the optical action when blue light, green light, and red light are incident on the color synthesis unit 10, and FIG. 2 (a) shows the blue light 35B. 36B is a schematic diagram showing the optical action of green light 35G and red light 35R. Here, the blue light 35B is incident from the polarization beam splitter 30 toward the wavelength selective modulation element 20 in the + Z direction, and the green light 35G is incident from the wavelength selection modulation element 20 toward the polarization beam splitter 30 in the −Z direction. Incident at. The red light 35R is incident on the polarization beam splitter 30 in the + X direction.

Further, the light of the first wavelength band λ ₁ , the light of the second wavelength band λ ₂ , and the light of the third wavelength band λ ₃ may be arbitrarily represented as a combination of the light of these three wavelength bands. . For example, the first wavelength band is λ ₁ light reflected by the wavelength selective modulation element 20, and the second wavelength band λ ₂ light is light transmitted through the wavelength selective modulation element 20. . The light having the wavelength λ ₃ in the third wavelength band is assumed to be light that does not enter the wavelength selective modulation element 20, that is, light that enters only the polarization beam splitter 30. At this time, the light in the first wavelength band λ _{1 corresponds to} the blue light 35B and 36B, the light in the second wavelength band λ _{2 corresponds to} the green light 35G, and the light in the third wavelength band λ ₃ corresponds to the red light 35R. To do.

  Next, the optical action of the color synthesizing unit 10 for each color light will be described. First, the blue light 35B is incident in the + Z direction from the polarization beam splitter 30 toward the wavelength selective modulation element 20 as described above. At this time, the blue light 35B is incident as linearly polarized light in the X direction. That is, the blue light 35B is linearly polarized light that oscillates within the light incident surface, and can be considered as P-polarized light. Here, the polarization beam splitter 30 has a characteristic of transmitting P-polarized light and reflecting S-polarized light in a specific wavelength band, and here, for the light of at least 450 nm wavelength band in this way. Although it acts, it may act similarly with respect to light in the 510 nm wavelength band. The S-polarized light is linearly polarized light that vibrates perpendicularly to the light incident surface, and is orthogonal to the P-polarized light. The combination of linearly polarized light that is orthogonal to each other, such as S-polarized light and P-polarized light, can also be defined as first linearly polarized light and second linearly polarized light. When the first linearly polarized light is S-polarized light, the second linearly polarized light is P-polarized light, and when the first linearly polarized light is P-polarized light, the second linearly polarized light is Can be considered as S-polarized light.

The P-polarized blue light 35 </ b> B that has passed through the polarization beam splitter 30 first enters the first wavelength plate 22 of the wavelength selective modulation element 20. Here, the 1st wavelength plate 22 has a function as a quarter wavelength plate with respect to the blue light 35B, for example. That is, the first wave plate 22 is made of a birefringent material, and in the XY plane, for example, the direction of the slow axis of the first wave plate 22 is aligned in a direction that forms 45 ° with respect to the X direction. It shall be. At this time, the thickness d of the first wave plate 22 is substantially equal to (4m−3) λ / (4 × Δn) or (4m−1) λ / (4 × Δn), where m is a natural number. It is good to set and to function as a quarter wavelength plate. Incidentally, [Delta] n is the refractive index anisotropy of the birefringent material forming the first wave plate 22, i.e., corresponding to the difference between the extraordinary refractive index n _e and ordinary refractive index n _o,.

  The blue light 35 </ b> B that has passed through the first wave plate 22 is incident on the dichroic mirror 23 as, for example, clockwise circularly polarized light. Since the dichroic mirror 23 reflects blue light and transmits green light as described above, the blue light 35B is reflected and is incident on the first wave plate 22 again. At this time, the light reflected by the dichroic mirror 23 becomes counterclockwise circularly polarized light, and the first wave plate 22 becomes linearly polarized light in the Y direction, that is, S-polarized light, and enters the polarization beam splitter 30. Incident. The blue light 36B that has become S-polarized light is reflected by the optical multilayer film 31 and travels in the X direction.

  Next, the green light 35G will be described. As shown in FIG. 2B, the green light 35G is incident in the −Z direction from the wavelength selective modulation element 20 toward the polarization beam splitter 30 as linearly polarized light in the Y direction, that is, S-polarized light. . The second wave plate 24 has a characteristic that cancels the modulation function of the first wave plate 22. That is, when light is incident on the first wave plate 22 and the second wave plate 24 in this order, the polarization state of the light transmitted through the second wave plate 24 is that of the light incident on the first wave plate 22. What is necessary is just to be comprised so that it may become substantially the same as a polarization state. For example, in this case, the second wave plate 24 is made of the same birefringent material as the first wave plate 22 and has the same thickness d, and the direction of the slow axis of the first wave plate 22 is It is assumed that the direction of the slow axis of the second wave plate 24 is aligned in a direction forming −45 ° with respect to the X direction. That is, the second wave plate 24 is the same as the first wave plate 22 with respect to the position of the first wave plate 22 along the plane (XY plane) perpendicular to the optical axis. This can be realized by matching the rotated position.

  The green light 35G incident on the second wave plate 24 becomes light in a polarization state modulated with respect to linearly polarized light in the Y direction, that is, S-polarized light. In particular, since the first wave plate 22 functions as a quarter wave plate with respect to the light of the 450 nm wavelength band that is blue light, the second wave plate 24 is also 1 for the light of the same 450 nm wavelength band. It is good to function as a / 4 wavelength plate. The first wave plate 22 and the second wave plate 24 may not function as a quarter wave plate with respect to the green light 35G, and the green light 35G transmitted through the second wave plate 24 is It may be elliptically polarized light. Then, the green light 35G passes through the dichroic mirror 23 and enters the first wave plate 22.

  As described above, the first wave plate 22 is in a relation to return the polarization state of the light modulated by the second wave plate 24 to the polarization state of the light before entering the second wave plate 24. The green light 35G that passes through the wavelength selective modulation element 20 again enters the polarization beam splitter 30 as S-polarized light. Then, the green light 35G that has become S-polarized light is reflected by the optical multilayer film 31 and travels in the X direction. The polarization beam splitter 30 may reflect the green light 35G with a high reflectance regardless of the polarization state. That is, even when the green light includes a P-polarized light component, it may be reflected in the same manner as the S-polarized light component.

  Next, the red light 35R will be described. As shown in FIG. 2B, the red light 35R enters the polarization beam splitter 30 in the X direction as Y-direction linearly polarized light, that is, S-polarized light. The polarization beam splitter 30 has a characteristic of transmitting P-polarized light and reflecting S-polarized light with respect to light of at least 450 nm wavelength band. It shall have the property of transmitting. Therefore, the red light 35 </ b> R exhibits a high transmittance regardless of the polarization state, and is emitted from the polarization beam splitter 30 in the X direction as it is. The polarization beam splitter 30 may transmit S-polarized light and reflect P-polarized light with respect to the red light 35R.

In this way, the light having the same wavelength is incident on the light having the first wavelength λ ₁ , the light having the second wavelength λ ₂ , and the light having the third wavelength λ ₃ , which have different wavelengths. It can be synthesized to travel in the direction. The wavelength selective modulation element 20 is formed by forming a first wave plate 22, a dichroic mirror 23, and a second wave plate 23 in parallel with the transparent substrates 21a and 21b. In this configuration, an optical multilayer film is formed only on the boundary surface between two triangular prisms. In this manner, incident light can be synthesized without a complicated configuration, and stable optical characteristics can be obtained. In addition, as shown in FIGS. 2A and 2B, the polarization state of light in each incident wavelength band is set as specific linearly polarized light, or the wavelength and polarization state of incident light. By adjusting the transmission and reflection characteristics of the polarization beam splitter 30 with respect to the light, the polarization state of the light in each wavelength band emitted from the color synthesis unit can be matched.

(Second Embodiment of Color Composition Unit)
FIG. 3 is a schematic diagram showing a configuration of the color synthesis unit 40 according to the present embodiment, and includes a wavelength selective modulation element 20 and a polarization beam splitter 50. In FIG. 3, the color synthesizing unit 40 shows the wavelength selective modulation element 20 and the polarization beam splitter 50 separately, but they may be configured integrally. The wavelength selective modulation element 20 has the same configuration as that of the first embodiment, and avoids repeated description. The polarizing beam splitter 50 is joined so that two triangular prisms sandwich the optical multilayer film 51, and in particular, the surface of the optical multilayer film 51 forms an angle of about 45 ° with respect to the plane of the transparent substrate 21a. Placed in. Further, as the material of the optical multilayer film 51, an inorganic material or an organic material such as SiO ₂ , SiON, ZrO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , TiO ₂ , Al ₂ O ₃ , or MgF ₂ may be used. it can. Further, as will be described later, the polarization beam splitter 50 has a function in which the transmittance / reflectance differs depending on the polarization state and the transmittance / reflectance varies depending on the wavelength of incident light.

  Next, the optical action of the color synthesis unit 40 will be described. The color synthesis unit 40 according to the present embodiment uses light of a 450 nm wavelength band that becomes blue light, light of a 510 nm wavelength band that becomes green light, and light of a 630 nm wavelength band that becomes red light. 4 (a) and 4 (b) are schematic diagrams showing optical actions when blue light, green light, and red light are incident on the color synthesis unit 40, and FIG. 4 (a) shows the blue light 55B. FIG. 4B is a schematic diagram showing the optical action of green light 55G and red light 55R. Here, the blue light 55B is incident in the −X direction toward the polarization beam splitter 50, and the green light 55G is incident in the −Z direction from the wavelength selective modulation element 20 toward the polarization beam splitter 50. The red light 55R is incident on the polarization beam splitter 50 in the + X direction.

Further, as a combination of light of these three wavelength bands, as in the first embodiment, light of the first wavelength band λ ₁ , light of the second wavelength band λ ₂ , and third wavelength band λ ₃ Let's consider the case of expressing as light. At this time, the light in the first wavelength band λ _{1 corresponds to} the blue light 55B and 56B, the light in the second wavelength band λ _{2 corresponds to} the green light 55G, and the light in the third wavelength band λ ₃ corresponds to the red light 55R. To do.

  Next, the optical action of the color synthesizing unit 40 for each color light will be described. First, the blue light 55B is incident in the + Z direction from the polarization beam splitter 50 toward the wavelength selective modulation element 20 as described above. At this time, the blue light 55B is incident as linearly polarized light in the Y direction. That is, the blue light 55B is linearly polarized light that vibrates in a direction orthogonal to the light incident surface, and can be considered as S-polarized light. Here, the polarization beam splitter 50 has a characteristic of transmitting P-polarized light and reflecting S-polarized light in a specific wavelength band, and here, for the light of at least 450 nm wavelength band in this way. Although it acts, it may act similarly with respect to light in the 510 nm wavelength band.

  The S-polarized blue light 55 </ b> B incident on the polarization beam splitter 50 is reflected by the optical multilayer film 51 and enters the first wavelength plate 22 of the wavelength selective modulation element 20. Here, the first wave plate 22 has a function as a quarter wave plate for the blue light 55B, for example, as in the first embodiment. The blue light 55 </ b> B that has passed through the first wave plate 22 is incident on the dichroic mirror 23 as, for example, clockwise circularly polarized light. Since the dichroic mirror 23 reflects blue light and transmits green light, the blue light 55B is reflected and is incident on the first wave plate 22 again. At this time, the light reflected by the dichroic mirror 23 becomes counterclockwise circularly polarized light and becomes linearly polarized light in the X direction by the first wave plate 22, that is, P-polarized light, and enters the polarization beam splitter 50. Incident. Then, the blue light 56 </ b> B that has become P-polarized light passes through the optical multilayer film 51 and travels in the −Z direction.

  Next, the green light 55G will be described. As shown in FIG. 4B, the green light 55G is incident in the −Z direction from the wavelength selective modulation element 20 toward the polarization beam splitter 50 as X-direction linearly polarized light, that is, P-polarized light. . Further, the second wave plate 24 has the same configuration as that of the first embodiment, and the second wave plate 24 has a characteristic that cancels out the modulation function of the first wave plate 22. When the green light 55G incident in the order of the second wave plate 24, the dichroic mirror 23, and the first wave plate 22 passes through the first wave plate 22, it is the same as the green light 55G incident on the second wave plate 24. The light enters the polarization beam splitter 50 with the polarization state, that is, linearly polarized light in the X direction. The P-polarized green light 35G passes through the optical multilayer film 51 and travels in the −Z direction.

  Next, the red light 55R will be described. As shown in FIG. 4B, the red light 55R enters the polarization beam splitter 50 in the X direction as linearly polarized light in the Z direction, that is, P-polarized light. The polarization beam splitter 50 has characteristics of transmitting P-polarized light and reflecting S-polarized light with respect to light of at least 450 nm wavelength band, but does not affect the light of 630 nm wavelength band regardless of the polarization state. It shall have the property of reflecting. Therefore, the red light 55R exhibits a high reflectance regardless of the polarization state, is reflected by the optical multilayer film 51 of the polarization beam splitter 50, and is emitted in the −Z direction. The polarizing beam splitter 50 may transmit S-polarized light and reflect P-polarized light with respect to the red light 55R.

In this way, the light having the same wavelength is incident on the light having the first wavelength λ ₁ , the light having the second wavelength λ ₂ , and the light having the third wavelength λ ₃ , which have different wavelengths. It can be synthesized to travel in the direction. Also, as shown in FIGS. 4A and 4B, the polarization state of light in each incident wavelength band is set as specific linearly polarized light, or the wavelength and polarization state of incident light. By adjusting the transmission and reflection characteristics of the polarization beam splitter 50, the polarization state of the light in each wavelength band emitted from the color synthesis unit can be matched.

(First Embodiment of Projection Display Device)
Next, a projection display device using the color synthesis unit according to the present invention will be described. FIG. 5 is a schematic diagram showing the projection display device 100 according to the present embodiment using the color synthesis unit 10. The projection display apparatus 100 includes a light source 101 that emits white light, and the light emitted from the light source 101 enters the polarization conversion element 102 and is converted into light having a specific polarization direction, for example, linearly polarized light. 103 is incident. Note that the white light emitted from the light source 101 includes blue light, green light, and red light. The dichroic prism 103 has characteristics of transmitting blue light and reflecting green light and red light. The blue light is reflected by the reflection mirror 105 and travels toward the light valve 108B, and the green light and red light are dichroic. Proceed in the direction of the prism 104. The dichroic prism 104 has a characteristic of transmitting green light and reflecting red light. The green light is reflected by the reflection mirrors 106 and 107 and travels toward the light valve 108G, and the red light travels toward the light valve 108R. Proceed to. The dichroic prism 103 and the dichroic prism 104 are also collectively referred to as a color separation unit.

  Each of the light valves 108B, 108G, and 108R includes a transmissive liquid crystal panel that generates blue, green, and red images. Then, the image data of each color that has passed through the light valves 108B, 108G, and 108R passes through the polarizers 109B, 109G, and 109R, becomes light of specific linearly polarized light, and enters the color synthesis unit 10. Here, the polarizer 109B transmits only P-polarized light and reflects or absorbs S-polarized light, and the polarizers 109G and 109R transmit only S-polarized light and reflects P-polarized light. Absorb. The light of each color incident on the color synthesis unit 10 is synthesized to generate an image, enters the projection lens unit 110, and is projected on the screen 111.

  Further, although the projection display device 100 has been described as using the white light as the light source 101, a projector in which a lamp, a semiconductor laser, or the like emitting blue light, green light, or red light is integrated may be used. Furthermore, instead of using the dichroic prisms 103 and 104 and the reflection mirrors 105, 106, and 107, the light sources of the respective colors may be directly incident on the light valves for the respective colors. Also in this case, the light sources of these colors are collectively defined as light sources. Moreover, you may provide a lens in the optical path of the light of each color in the optical path of white light.

  Next, a projection display apparatus having another configuration will be described. FIG. 6 is a schematic diagram showing the projection display device 130 according to the present embodiment using the color synthesis unit 40. In addition, among the optical components constituting the projection display device 130, the same components as those of the projection display device 100 are denoted by the same reference numerals to avoid redundant description. First, light emitted from the light source 101 enters the polarization conversion element 102, is converted into light having a specific polarization direction, for example, linearly polarized light, and enters the dichroic prism 133. The dichroic prism 133 has characteristics of transmitting red light and reflecting green light and blue light. The red light is reflected by the reflection mirror 105 and travels in the direction of the light valve 138R, and the green light and blue light are dichroic. Proceed in the direction of the prism 134. The dichroic prism 134 has a characteristic of reflecting green light and transmitting blue light, green light travels in the direction of the light valve 138G, blue light is reflected by the reflection mirrors 106 and 107, and the direction of the light valve 138B. Proceed to

  The light valves 138B, 138G, and 138R are each composed of a transmissive liquid crystal panel that generates blue, green, and red images. Then, the image data of each color transmitted through the light valves 138B, 138G, and 138R is transmitted through the polarizers 139B, 139G, and 139R, and is incident on the color synthesis unit 40 as light of specific linearly polarized light. Here, the polarizers 139R and 139G transmit only P-polarized light and reflect or absorb S-polarized light, and the polarizer 109B transmits only S-polarized light and reflect or absorb P-polarized light. To do. The light of each color incident on the color synthesis unit 40 is synthesized to generate an image, enters the projection lens unit 110, and is projected on the screen 111. The projection display device 130 may also use a light source other than white light as the light source 101, and may be configured without the dichroic prisms 133 and 134 and the reflection mirrors 105, 106, and 107. Moreover, you may provide a lens in the optical path of the light of each color in the optical path of white light.

(Second Embodiment of Projection Display Device)
Although the projection display devices 100 and 130 have been described with respect to the configuration including the light valve for each color, the projection display device according to the present embodiment includes a reflective liquid crystal element (LCOS: Liquid Crystal on Silicon). Unlike a transmissive liquid crystal element such as a light valve, a reflective liquid crystal element can form a structure such as a transistor for driving liquid crystal on the light reflecting side, thereby increasing the pixel density. be able to. As a result, a high resolution, a high aperture ratio, and a high contrast ratio can be obtained.

  FIG. 7 is a schematic diagram showing a projection display device 150 according to the present embodiment using the color synthesis unit 10. The projection display device 150 includes a blue light source 151B such as a semiconductor laser, a green light source 151G, and a red light source 151R, and enters the color synthesis unit 10 via lenses 152B, 152G, and 152R, respectively. Also in this case, the blue light source 151B, the green light source 151G, and the red light source 151R are collectively defined as light sources. Further, a polarizer may be used in the optical path from the blue light source 151B, the green light source 151G, and the red light source 151R to the color synthesis unit 10.

  Then, all the lights synthesized and emitted by the color synthesis unit 10 are converted to S-polarized light and travel to the polarization beam splitter 153. The polarization beam splitter 153 has a characteristic of reflecting S-polarized light and transmitting P-polarized light, and the S-polarized light is reflected by the polarization beam splitter 153 and travels to the reflective liquid crystal element 154. The light reflected by the reflective liquid crystal element 154 is reflected after the polarization state is changed so as to correspond to each pixel in accordance with the image to be projected. At this time, the reflected light is a mixture of S-polarized light and P-polarized light. However, when the light is incident on the polarization beam splitter 153, the S-polarized light is reflected in a different direction from the screen 156. , P-polarized light passes straight through, enters the projection lens unit 155, and an image is projected onto the screen 156.

  Next, a projection display apparatus having another configuration will be described. FIG. 8 is a schematic diagram showing a projection display device 170 according to the present embodiment using the color synthesis unit 40. In addition, among the optical components constituting the projection display device 170, the same components as those of the projection display device 150 are denoted by the same reference numerals to avoid duplicate description. The projection type display device 170 has a blue light source 171B such as a semiconductor laser, a green light source 171G, and a red light source 171R, and enters the color synthesis unit 40 through lenses 172B, 172G, and 172R, respectively. Also in this case, the blue light source 171B, the green light source 171G, and the red light source 171R are collectively defined as light sources. Further, a polarizer may be used in the optical path from the blue light source 171B, the green light source 171G, and the red light source 171R to the color synthesis unit 40.

  Then, all of the lights synthesized and emitted by the color synthesis unit 40 become P-polarized light and travel to the polarization beam splitter 173. The polarization beam splitter 173 has a characteristic of transmitting P-polarized light and reflecting S-polarized light, and the P-polarized light passes through the polarization beam splitter 173 and proceeds to the reflective liquid crystal element 174. The light reflected by the reflective liquid crystal element 174 is reflected after the polarization state is converted so as to correspond to each pixel in accordance with the image to be projected. At this time, the reflected light is a mixture of S-polarized light and P-polarized light, but when entering the polarization beam splitter 173, the P-polarized light travels in a different direction from the screen 156, whereas S-polarized light is reflected, enters the projection lens unit 155, and an image is projected onto the screen 156.

  The projection display devices 150 and 170 according to the present embodiment generate images using the polarization beam splitters 153 and 173 and the reflective liquid crystal elements 154 and 174, in particular. Therefore, if the polarization state of the light of each color emitted from the color synthesis units 10 and 40 is linearly polarized light in the same direction, or in the optical path between the color synthesis unit 10 and the polarization beam splitter 153 or the color synthesis unit 40 It is not necessary to arrange a polarization conversion element for aligning the polarization state of light of each color in the optical path between the polarization beam splitter 173, and the apparatus can be downsized.

  In this embodiment, a specific design example of the color synthesis unit 10 will be described with reference to FIG. 1. First, the wavelength selective modulation element 20 will be described. Using a white glass substrate as the transparent substrates 21a and 21b, these are washed and dried, and an antireflection film is formed on one surface using a vacuum deposition method. Next, an alignment film is formed by rubbing a polyimide film formed by applying polyimide on the surface of the white plate glass opposite to the surface on which the antireflection film is formed. Then, a liquid crystal monomer having birefringence is uniformly coated on the alignment film and irradiated with UV light, whereby the thickness 3 of the polymer liquid crystal in which the major axis direction of the liquid crystal molecules is uniform and aligned in the thickness direction. A first wave plate 22 and a second wave plate 24 of .75 μm are formed. At this time, the phase difference generated in the first wave plate 22 and the second wave plate 24 is 90 ° (= π / 2) with respect to light having a wavelength of 450 nm and 78 ° with respect to light having a wavelength of 510 nm. It is. The major axis direction of the liquid crystal molecules corresponds to the slow axis direction.

Next, using a white glass substrate as a transparent substrate (not shown), these are washed and dried, and Ta ₂ O ₅ layers and SiO ₂ layers are alternately laminated on the white plate glass substrate surface to form an optical multilayer film. The optical multilayer film is formed and sandwiched by another white glass substrate (not shown). Specifically, the optical multilayer film has a structure shown in Table 1, and this optical multilayer film corresponds to the dichroic mirror 23. Table 1 shows the refractive indexes of Ta ₂ O ₅ and SiO ₂ with respect to light of 510 nm and the film thickness of each layer.

  FIG. 9 shows the wavelength dependence of the transmittance and the reflectance when light is incident from the normal direction of the surface of the dichroic mirror 23 in the dichroic mirror 23 based on Table 1. In addition, the configuration shown in Table 1 is not dependent on the polarization of incident light, and the same utilization efficiency characteristics can be obtained regardless of the polarization state. Here, in FIG. 9, the reflectance is shown by a solid line and the transmittance is shown by a broken line. However, from the configuration of the optical multilayer film based on Table 1, when the wavelength range of 435 to 465 nm is a 450 nm wavelength band, The reflectance of light in the wavelength range from 495 to 525 nm is approximately 510%, whereas the reflectance in the 510 nm wavelength band is approximately 0%, that is, the light in the 510 nm wavelength band. The transmittance of is approximately 100%. Therefore, in the optical multilayer film based on Table 1, when blue light and green light are incident along the normal direction of the optical multilayer film surface, the blue light is selectively totally reflected, whereas the green light is almost totally reflected. Transmits completely.

  Thereafter, a first wave plate 22 made of polymer liquid crystal formed on the first transparent substrate 21a, and a second wave plate 24 made of polymer liquid crystal formed on the second transparent substrate 21b, Thus, the wavelength-selective modulation element 20 is obtained by bonding with a transparent adhesive from both sides so as to sandwich the dichroic mirror 23. At this time, the antireflection film formed on the transparent substrates 21a and 21b is the outermost surface, and the slow axis of the first wave plate 22 and the slow axis of the second wave plate 24 are overlapped so as to be orthogonal to each other. Match.

Next, the polarization beam splitter 30 will be described. White plate glass is washed and dried as a transparent substrate, Ta ₂ O ₅ layers and SiO ₂ layers are alternately laminated on the surface of the white plate glass substrate to form an optical multilayer film. The multilayer film is sandwiched. Specifically, the optical multilayer film 31 has the structure shown in Table 2, and Table 2 shows the refractive indexes of Ta ₂ O ₅ and SiO ₂ with respect to light of 510 nm and the film thickness of each layer.

  Then, the two white glass substrates are processed so that the surfaces of the substrates form an angle of 45 ° with respect to the surface of the optical multilayer film 31 to obtain the polarization beam splitter 30. FIG. 10 shows the wavelength of transmittance and reflectance when light is incident from a direction forming an angle of 45 ° with respect to the surface of the optical multilayer film 31 in the polarizing beam splitter 30 having the optical multilayer film 31 based on Table 2. It shows dependency. Here, in FIG. 10, the characteristics in the vicinity of blue light are indicated by a thin solid line, the characteristics in the vicinity of green light are indicated by a broken line, and the characteristics in the vicinity of red light are indicated by a thick solid line. The horizontal axis indicates the utilization efficiency, which represents the product of the transmittance of P-polarized light and the reflectance of S-polarized light for the vicinity of blue light. Here, since the utilization efficiency in blue light is approximately 100%, it indicates that the transmittance of P-polarized light and the reflectance of S-polarized light in blue light are approximately 100%.

  Further, in FIG. 10, the reflectance of S-polarized light is shown as the utilization efficiency for the vicinity of green light, and the transmittance of S-polarized light is shown as the utilization efficiency for the vicinity of red light. is there. Accordingly, the reflectance of the S-polarized light in the 510 nm wavelength band is approximately 100%, and the S-polarized light in the 630 nm wavelength band when the wavelength range of 615 to 645 nm is the 630 nm wavelength band. The transmittance of is approximately 100%. Therefore, in the optical multilayer film 31 based on Table 2, when light of a predetermined polarization state is incident from a direction that forms an angle of 45 ° with respect to the surface of the optical multilayer film 31, it is selectively selected according to the polarization state and wavelength. Transmit or reflect.

  The wavelength selective modulation element 20 and the polarization beam splitter 30 manufactured in the present embodiment are unitized as a color synthesis unit 30, and blue light 35B and green are displayed in the directions shown in FIGS. 2 (a) and 2 (b). The light 35G and the red light 35R are incident as light in the respective polarization directions. Then, the blue light 35B incident as P-polarized light is transmitted through the polarization beam splitter 30 with a transmittance of approximately 100%, and reflected with a reflectance of approximately 100% by the dichroic mirror 23 of the wavelength selective modulation element 20. Is done. Then, the blue light 36B that has become S-polarized light is reflected by the polarization beam splitter 30 with a reflectance of almost 100%.

  Further, the green light 35G incident as S-polarized light is transmitted through the dichroic mirror 23 of the wavelength selective modulation element 20 with a transmittance of almost 100%, and is transmitted through the wavelength selective modulation element 20 as S-polarized light. . The green light 35G is reflected by the polarization beam splitter 30 with a reflectance of almost 100%. Further, the red light 35R incident as S-polarized light is transmitted through the polarization beam splitter 30 with a transmittance of almost 100%. Thus, the light of each color emitted from the color combining unit 10 (polarization beam splitter 30) is combined as linearly polarized light with high light utilization efficiency and the same polarization state.

  As described above, the present invention can provide a color synthesizing unit and a projection display device that synthesizes and emits three types of incident light with different traveling directions and wavelengths with stable optical characteristics.

10, 40 color synthesis unit 20 wavelength selective modulation element 21a first transparent substrate 21b second transparent substrate 22 first wave plate 23 dichroic mirror 24 second wave plate 30, 50, 153, 173 polarization beam splitter 31 , 51 Optical multilayer film 35R, 55R, 205R, 215R Red light 35G, 55G, 205G, 215G Green light 35B, 36B, 55B, 56B, 205B, 215B Blue light 100, 130, 150 Projection display device 101 Light source 102 Polarization conversion Element 103, 104, 133, 134 Dichroic prism 105, 106, 107 Reflection mirror 108R, 108G, 108B, 138R, 138G, 138B Light valve 109R, 109G, 109B, 139R, 139G, 139B Polarizer 110, 155 Projection lens unit 111, 156 Screen 151R, 171R Red light source 151G, 171G Green light source 151B, 171B Blue light source 152R, 152G, 152B, 172R, 172G, 172B Lens 154, 174 Reflective liquid crystal element 200 Composite prism 201, 202 Reflecting surface 211 212, 213 Triangular prism 211a, 212a Dielectric multilayer film

Claims (7)

A color synthesis unit in which light in the _first wavelength band λ ₁ , light in the second wavelength band λ ₂ , and light in the third wavelength band λ ₃ are incident from different directions and emitted in the same direction. There,
The color synthesis unit includes a wavelength selective modulation element and a polarization beam splitter,
The wavelength selective modulation element includes a first wave plate, a dichroic mirror, and a second wave plate in this order,
The first wave plate and the second wave plate have a characteristic of functioning as a quarter wave plate for light in the first wavelength band λ ₁ ,
The dichroic mirror reflects the light in the first wavelength band λ ₁ and transmits the light in the _second wavelength band λ ₂ ;
The polarization beam splitter reflects the first linearly polarized light out of the light in the _first wavelength band λ1, and the second linearly polarized light orthogonal to the first linearly polarized light. Transparent and
Of the light in the _second wavelength band λ ₂ , the light reflects at least the first linearly polarized light and transmits the light in the _third wavelength band λ ₃ , or the second wavelength band λ _2. A color synthesizing unit that transmits at least the second linearly polarized light and reflects the light in the _third wavelength band λ3. The light in the first wavelength band λ ₁ is incident on the polarization beam splitter and the wavelength selective modulation element in this order,
The light in the second wavelength band λ ₂ is incident on the wavelength selective modulation element and the polarization beam splitter in this order,
The color synthesis unit according to claim 1, wherein the light of the third wavelength band λ ₃ is incident only on the polarization beam splitter. The light in the first wavelength band λ ₁ , the light in the second wavelength band λ ₂ , and the light in the third wavelength band λ ₃ that are emitted in the same direction are all light of the first linearly polarized light. 3. The color synthesis unit according to claim 1, wherein each of the color synthesis units is the light of the second linearly polarized light.   The first wave plate and the second wave plate are made of the same birefringent material and have the same thickness, and the slow axis direction of the first wave plate and the second wave plate The color synthesizing unit according to claim 1, wherein the slow axis direction is arranged so as to be substantially orthogonal to each other. The light in the first wavelength band λ ₁ is blue light, the light in the second wavelength band λ ₂ is green light, and the light in the third wavelength band λ ₃ is red light. The color synthesis unit according to any one of -4. A light source that emits at least blue light, green light, and red light; a plurality of light valves that modulate the blue light, the green light, and the red light according to a displayed image; and a projection lens unit that projects an image;
A projection display device comprising the color synthesis unit according to claim 1 in an optical path between the plurality of light valves and the projection lens unit. A light source that emits at least blue light, green light, and red light; a reflective liquid crystal element that modulates the blue light, the green light, and the red light according to a displayed image; and a projection lens unit that projects an image;
A projection display device comprising the color synthesis unit according to any one of claims 1 to 5 in an optical path between the light source and the reflective liquid crystal element.

Images