JP2013200374A - Image display apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display an image having a wide color reproduction region and a high contrast.SOLUTION: An image display apparatus includes: a first wavelength selective retardation plate which rotates the polarization direction of color light of either first color light or third color light that is separated by an optical path separation element; a second wavelength selective retardation plate which rotates the polarization direction of color light of either second color light or fourth color light that is separated by the optical path separation element; a first polarization separation element which leads the first color light emitted from the first wavelength selective retardation plate to a first reflective type optical modulation element, and which leads the third color light emitted from the first wavelength selective retardation plate to a third reflective type optical modulation element; and a second polarization separation element which leads the second color light emitted from the second wavelength selective retardation plate to a second reflective type optical modulation element, and which leads the fourth color light emitted from the second wavelength selective retardation plate to a fourth reflective type optical modulation element. The first color light to the fourth color light are in the order of the first, the second, the third and the fourth color lights from the short wavelength side.

Description

  The present invention relates to an image display device, and more particularly to an image display device that displays an image using four primary colors.

  For an image display device, the size of the color reproduction region is an important issue in displaying a colorful image. An image display device generally displays an image with three primary colors of blue, green, and red. For this reason, the expansion of the color reproduction region is basically handled by narrowing the wavelength band of each color. However, since the color reproduction area of the three primary colors is always a triangular area, it is impossible to cover the entire visible color of the bell shape when the color purity of the primary color is improved. In order to improve this, a technique is known in which the number of primary colors is increased to four to form a rectangular color reproduction region.

  On the other hand, a reflective liquid crystal panel has features such as a high aperture ratio and high definition compared to a transmissive liquid crystal panel. When a reflective liquid crystal panel is used, it is necessary to separate the optical path in accordance with the polarization state changed by the reflective liquid crystal panel. Therefore, a polarization separation element is generally arranged on the light incident side of the liquid crystal panel. . For this reason, a color separation / synthesis system for an image display device using a reflective liquid crystal panel tends to be large. On the other hand, a configuration is known in which two reflective liquid crystal panels are arranged in one polarization separation element to reduce the size. Patent Document 1 discloses a proposal for realizing a projector of four primary colors using this configuration.

JP-A-2005-241904

  However, in Patent Document 1, two primary color lights incident on a polarization beam splitting element on which two reflective liquid crystal panels are arranged are primary color lights in adjacent wavelength bands. The two primary color lights are converted into linearly polarized light whose polarization directions are orthogonal to each other by the wavelength selective phase difference plate before entering the polarization separation element. However, the wavelength selective phase difference plate is a wavelength band where polarization conversion is not satisfactorily performed at the boundary between a wavelength band for adding a phase (hereinafter referred to as a phase added band) and a wavelength band for not adding a phase (hereinafter referred to as a non-phase added band) There is. For this reason, the wavelength in this band becomes elliptically polarized light and enters the polarization splitting element, leading to a decrease in contrast.

In order to solve the above problems, an image display device according to the present invention provides:
An optical path separation element that separates light emitted from the light source into first color light and third color light, and second color light and fourth color light;
A first wavelength-selective phase plate that rotates the polarization direction of any one of the first color light and the third color light separated by the optical path separation element;
A second wavelength-selective phase difference plate that rotates the polarization direction of one of the second color light and the fourth color light separated by the optical path separation element;
The first color light emitted from the first wavelength selective phase difference plate is guided to a first reflection type light modulation element, and the third color light emitted from the first wavelength selective phase difference plate is designated as a third reflection type. A first polarization separation element that guides to a light modulation element and synthesizes image light modulated by the first and third reflective light modulation elements;
The second color light emitted from the second wavelength selective phase difference plate is guided to a second reflection type light modulation element, and the fourth color light emitted from the second wavelength selective phase difference plate is designated as a fourth reflection type. A second polarization separation element that guides to the light modulation element and synthesizes the image light modulated by the second and fourth reflective light modulation elements;
An optical path synthesis element that synthesizes image light emitted from the first polarization separation element and the second polarization separation element;
The first color light to the fourth color light are first, second, third, and fourth color lights in order from the short wavelength side.

An image display device according to another aspect of the present invention is
An optical path separation element that separates light emitted from the light source into first color light and third color light, and second color light and fourth color light;
A wavelength-selective retardation plate that is disposed between the light source and the optical path separation element, and rotates a polarization direction of the first color light and the second color light, or the third color light and the fourth color light;
The first color light separated by the optical path separation element is guided to a first reflective light modulation element, the third color light separated by the optical path separation element is guided to a third reflective light modulation element, and the first And a first polarization separation element that synthesizes the image light modulated by the third reflective light modulation element,
The second color light separated by the optical path separation element is guided to a second reflective light modulation element, the fourth color light separated by the optical path separation element is guided to a fourth reflective light modulation element, and the second And a second polarization separation element that synthesizes the image light modulated by the fourth reflective light modulation element,
An optical path synthesis element that synthesizes image light emitted from the first polarization separation element and the second polarization separation element;
The first color light to the fourth color light are first, second, third, and fourth color lights in order from the short wavelength side.

An image display device according to another aspect of the present invention is
The first wavelength that rotates the polarization direction of either the first color light and the second color light or the third color light and the fourth color light among the first color light to the fourth color light included in the light emitted from the light source. A selective retardation plate;
The light that has passed through the first wavelength selective phase difference plate is separated into the first color light, the third color light, the second color light, and the fourth color light, and the second color light and the third color light. An optical path separation element that reflects s-polarized light in a wavelength band between colored lights and transmits p-polarized light in a wavelength band between the second color light and the third color light;
The light separated by the optical path separation element is incident, and the incident light is guided to the first and third reflection type light modulation elements according to the polarization direction of the incident light, and the first and third reflection types are guided. A first polarization separation element that combines image light modulated by the light modulation element;
The light separated by the optical path separation element is incident, and the incident light is guided to the second and fourth reflective light modulation elements according to the polarization direction of the incident light, and the second and fourth reflective types A second polarization separation element that synthesizes image light modulated by the light modulation element;
An optical path combining element that combines image light emitted from the first polarization separation element and the second polarization separation element;
A second wavelength-selective retardation plate that is disposed between the first polarization separation element and the optical path synthesis element and rotates the polarization direction of the first color light;
The second polarization component is disposed between the element and the optical path synthesis element, and has a third wavelength-selective phase plate that rotates the polarization direction of the fourth color light,
The first color light to the fourth color light are first, second, third, and fourth color lights in order from the short wavelength side.

  An image display device in which the projection optical system is integrally provided or detachably mounted also constitutes another aspect of the present invention.

  According to the present invention, it is possible to provide an image display device in which the color reproduction region is widened and the contrast is improved.

  Another effect of the present invention is that an image display device with reduced ghost light can be provided.

1 is a schematic configuration diagram of an image display device according to a first embodiment of the present invention. Spectrum of light source used in Example 1 of the present invention Reflectance characteristics diagram of optical path separation element used in Example 1 of the present invention Phase characteristic diagram of wavelength selective phase difference plate on incident side used in Example 1 of the present invention Phase characteristic diagram of wavelength selective phase difference plate on emission side used in Example 1 of the present invention Phase characteristic diagram of wavelength selective phase difference plate on incident side used in Example 1 of the present invention Phase characteristic diagram of wavelength selective phase difference plate on emission side used in Example 1 of the present invention Reflectance characteristic diagram of optical path combining element used in Example 1 of the present invention Output image spectrum of image display device according to embodiment 1 of the present invention Chromaticity coordinates of an image display device according to Embodiment 1 of the present invention Schematic configuration diagram of an image display apparatus according to Embodiment 2 of the present invention. Phase characteristic diagram of wavelength selective phase difference plate on incident side used in Example 2 of the present invention Reflectance characteristic diagram of optical path separation element used in Example 2 of the present invention Phase characteristic diagram of wavelength selective phase difference plate on emission side used in embodiment 2 of the present invention Phase characteristic diagram of wavelength selective phase difference plate on emission side used in embodiment 2 of the present invention Configuration diagram of image display apparatus according to Embodiment 3 of the present invention Reflectance characteristic diagram of dichroic filter used in Example 3 of the present invention Phase characteristic diagram of wavelength selective phase difference plate on incident side used in Example 3 of the present invention Reflectance characteristic diagram of optical path separation element used in Example 3 of the present invention Phase characteristic diagram of wavelength selective phase difference plate on emission side used in Example 3 of the present invention Phase characteristic diagram of wavelength selective phase difference plate on emission side used in Example 3 of the present invention Configuration diagram of image display apparatus according to Embodiment 4 of the present invention Reflectivity characteristic diagram of dichroic filter used in Example 4 of the present invention

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

Example 1
FIG. 1 is a schematic configuration diagram of an image display apparatus according to a first embodiment of the present invention. In FIG. 1, a light source 1 includes blue light (B light, first color light), cyan light (C light, second color light), yellow light (Y light, third color light), and red light (R light, fourth color light). It is a light source that emits four colored lights. The light source of this embodiment is a high-pressure mercury lamp, but is not limited to this. For example, a single light source that emits white light, such as a metal halide lamp, a white diode, or a white laser, or a plurality of color light sources and color combining means are included. However, a light source device that emits all colors in the same direction may be used. In any case, the light source 1 emits four primary color lights of B light, C light, Y light, and R light in one direction. In FIG. 1, the optical paths of the respective colors are shown as B, C, Y, and R.

  FIG. 2 shows a spectrum of light emitted from the light source 1, where the horizontal axis indicates the wavelength and the vertical axis indicates the light intensity. The light source 1 includes B, C, Y, and R wavelengths, and B, C, Y, and R primary color lights are arranged in order from the short wavelength side.

  The light emitted from the light source 1 enters the illumination optical system 2 in an arbitrary polarization state instead of a specific polarization state. The illumination optical system 2 has polarization conversion means (not shown), and the light incident on the illumination optical system 2 is aligned in polarization state when passing through the illumination optical system 2. In this embodiment, it is aligned with linearly polarized light in a direction that vibrates perpendicular to the paper surface. In the present embodiment, the linearly polarized light that vibrates perpendicularly to the paper surface is called s-polarized light in accordance with the definition of the polarization separation element described later, and is shown by drawing dots on the path. On the other hand, linearly polarized light that is orthogonal to s-polarized light and vibrates in the paper is called p-polarized light, and this is indicated by drawing a bar line on the path.

  Now, each color light that has been aligned to s-polarized light by the illumination optical system 2 enters the optical path separation element 3. The optical path separation element 3 is a dichroic mirror having a dielectric multilayer film and has reflectance characteristics as shown in FIG. The reflectance characteristic of FIG. 3 depicts the characteristic of s-polarized light, reflects Y light and B light, and transmits R light and C light. That is, the optical paths are separated by transmitting primary color light in at least two wavelength bands that are not adjacent to each other and reflecting primary color light in at least two wavelength bands that are not adjacent to each other.

  The optical path followed by the Y light and B light reflected by the optical path separation element 3 is defined as the first optical path, and the optical path of the R light and C light transmitted through the optical path separation element 3 is defined as the second optical path. Do. In addition, about the element arrange | positioned in a 1st optical path, the subscript of "a" is attached to the number.

  The Y light and B light reflected by the optical path separation element 3 and traveling through the first optical path pass through the incident side polarizing plate 4a, and then enter the wavelength selective phase difference plate 5a (first wavelength selective phase difference plate). ). The incident-side polarizing plate 4a has a property of passing only s-polarized light and absorbing p-polarized light, thereby improving the degree of polarization of light. Absorption-type polarizing plates are common, but there are also wire grid type polarizing plates that reflect a linearly polarized light in the lattice direction by forming a lattice structure with a period shorter than the wavelength on the substrate. It doesn't matter.

  The wavelength-selective retardation plate 5a is an element having a function of giving (giving) a different phase difference depending on the wavelength band, and is created by laminating materials having birefringence characteristics. The phase difference given by the wavelength selective phase difference plate 5a is a half wavelength, and a wavelength band giving a phase difference of a half wavelength is a phase addition band. A band where the phase difference given by the wavelength selective phase difference plate 5a is zero is defined as a non-phase added band.

  The characteristics of the wavelength selective phase difference plate 5a on the incident side are as shown in FIG. The wavelength band of the B light is a phase addition band, and a phase difference corresponding to a half wavelength is given to the B light. On the other hand, the wavelength band of Y light is a non-phase addition band, and no phase difference is given to Y light. In other words, the wavelength selective phase difference plate 5a rotates the polarization direction of the B light. As a result, the polarization direction of B light is changed from s-polarized light to p-polarized light, and Y light passes through s-polarized light.

  Now, there is a boundary band between the phase-added band and the non-phase-added band of the wavelength-selective phase difference plate 5a, where the given phase is smaller than a half wavelength and larger than zero. Then, it becomes elliptically polarized light and exits from the wavelength selective phase difference plate 5a. When this elliptically polarized light is incident on a polarization separation element or a liquid crystal display element arranged at a later stage, a decrease in contrast, unevenness in brightness, unevenness in color, and the like occur, and the image quality is greatly deteriorated. However, it is difficult to make the characteristic of the wavelength selective phase difference plate like a rectangular wave so as to eliminate this boundary band.

  In view of this point, in Example 1, the primary color light incident on the wavelength selective phase difference plate 5a is a primary color light having a combination in which the wavelength bands are not adjacent to each other. The light in the wavelength band (hereinafter referred to as the boundary band) between the two primary color lights is separated by the optical path separation element 3 into an optical path that does not enter the wavelength selective phase difference plate 5a. As a result, light corresponding to the boundary band of the wavelength-selective retardation plate 5a does not exist in the first optical path, so that contrast and brightness unevenness can be significantly improved as compared with the prior art.

  The B light and Y light that have passed through the wavelength selective phase difference plate 5a on the incident side enter the polarization separation element 6a (first polarization separation element). The polarization separation element 6a is a rectangular parallelepiped element in which two triangular prisms are bonded together, and a polarization separation film made of a dielectric multilayer film is deposited on the bonding surface. A polarization separation film made of a dielectric multilayer film has characteristics of reflecting s-polarized light and transmitting p-polarized light. Accordingly, the s-polarized Y light is reflected and the p-polarized B light is transmitted through the polarization separation surface of the polarization separation element 6a, and the reflection type liquid crystal display element 7Y (third reflection type light modulation element) and 7B are respectively transmitted. The light enters the first reflective light modulation element. In order to further improve the contrast, it is effective to arrange a quarter-wave plate between the polarization separation element and the reflective liquid crystal display element.

  When reflecting the incident light, the reflective liquid crystal display elements 7Y and 7B modulate the incident light according to the image signal. For light that becomes image light traveling on the screen, the polarization direction of linearly polarized light is rotated by 90 degrees. That is, the Y image light is modulated to p-polarized light and the B image light is modulated to s-polarized light. For this reason, the Y light incident on the polarization separation element 6a again passes through the polarization separation element 6a, and the B light is reflected. As a result, the light of the two colors once separated by the polarization separation element 6a is again combined with the optical path and emitted from the polarization separation element 6a.

  The Y light and B light emitted from the polarization separation element 6a enter the wavelength selective phase difference plate 8a on the emission side. The phase characteristics of the wavelength-selective phase difference plate 8a on the emission side are as shown in FIG. 5, the wavelength band of Y light is a phase addition band, and the phase difference corresponding to a half wavelength with respect to Y light. give. On the other hand, the wavelength band of B light is a non-phase addition band, and no phase difference is given to B light. As a result, the Y light is converted from p-polarized light to s-polarized light, and the B light passes through the s-polarized light and enters the output-side polarizing plate 9a.

  The exit-side polarizing plate 9a is arranged so that the absorption axis is in the plane of the paper, absorbs p-polarized light, and transmits s-polarized light. Thereby, unnecessary leakage light can be absorbed and contrast can be further improved. The s-polarized Y-color light and B-color light transmitted through the emission-side polarizing plate 9 a is incident on the optical path combining element 10.

  Subsequently, the optical paths of the R light and the C light transmitted through the optical path separation element 3, that is, the second optical path will be described. Regarding the elements arranged in the second optical path, the same number as that of the first optical path is used for elements having the same name, but the numbers are distinguished by adding a subscript “b”.

  The s-polarized R light and C light are incident on the incident-side wavelength-selective phase difference plate 5b (second wavelength-selective phase difference plate) after the degree of polarization is increased by the incident-side polarizing plate 4b. The phase characteristics of the wavelength-selective phase difference plate 5b on the incident side are as shown in FIG. 6, the wavelength band of the C light is a phase addition band, and the phase difference of a half wavelength with respect to the C light. give. On the other hand, the wavelength band of the R light is a non-phase added band, and no phase difference is given to the R light. In other words, the wavelength selective phase difference plate 5b rotates the polarization direction of the C light. As a result, the C light is converted from s-polarized light to p-polarized light, and the R light passes through the wavelength-selective retardation plate 5b as it is s-polarized light and enters the polarization separation element 6b (second polarization separation element).

  As shown in FIG. 6, in the wavelength selective phase difference plate 5b arranged in the second optical path, the boundary band between the phase addition band and the non-phase addition band is assigned to the wavelength band of Y light. Since the Y light is separated into the first optical path by the optical path separation element 3, the image quality such as a decrease in contrast and unevenness caused by the incidence of the light in the boundary band also in the second optical path, as in the description of the first optical path. Deterioration can be suppressed.

  The polarization separation element 6b reflects s-polarized R light and transmits p-polarized C light, and reflects the respective liquid crystal display elements 7R (fourth reflective light modulation element) and 7C (second reflective type). The light is incident on the light modulation element. The reflective liquid crystal display elements 7R and 7C apply modulation according to the image signal to the incident light. As a result, the R image light is modulated into p-polarized light, and the C image light is modulated into s-polarized light, and is incident on the polarization separation element 6b again. The optical path of the image light of R light and the image light of C light is combined by the polarization separation element 6b, and is incident on the wavelength selective phase plate 8b on the emission side.

  The wavelength selective phase difference plate 8b has the phase characteristics as shown in FIG. 7, the wavelength band of the R light is a phase addition band, and the phase difference of a half wavelength with respect to the R light. give. On the other hand, the C light wavelength band is a non-phase addition band, and no phase difference is given to the C light. As a result, the R light is converted from p-polarized light to s-polarized light, and the C light passes through the s-polarized light. The degree of polarization is increased by the exit-side polarizing plate 9b and is incident on the optical path combining element 10.

  The optical path combining element 10 is an element on which a dichroic film is deposited, and has a reflection characteristic as shown in FIG. As a result, the Y light and B light in the first optical path are transmitted by the optical path combining element 10, the R light and C light in the second optical path are reflected, the optical paths are combined, and enter the projection lens 11 (projection optical system).

  The projection lens 11 images the image light modulated by the reflective liquid crystal display element on a screen (projected surface) and displays an image using the four primary colors.

FIG. 9 shows the spectrum of an image projected on the screen by the image display apparatus of this embodiment. The four primary colors of this embodiment are in the following wavelength bands.
B color: 420 to 490 nm
C color: 490-530 nm
Y color: 530-590 nm
R color: 590-680 nm

  The chromaticity coordinates of an image using these four primary colors are shown in FIG. Compared to the conventional color reproduction area of the image using the three primary colors (the area indicated by the broken line in FIG. 10), a significantly wide color reproduction area can be secured. In particular, the addition of cyan increases the y coordinate and greatly improves the color reproducibility of the chromaticity region where the x coordinate is small. Thereby, for example, the beautiful sea and sky of emerald green can be displayed as a colorful image.

Of course, the wavelength band of this embodiment is only an example. The four primary colors B, C, Y and R are at least B: 450 to 470 nm
C color: 500 to 520 nm
Y color: 540 to 560 nm
R color: 610 to 630 nm
It is sufficient that the wavelength band is included. When the wavelength band of each color is narrowed, the brightness is lowered, but the color reproduction region can be further expanded. For example, when it is used in a dark theater where there is almost no external light, when the brightness is not so high, it is possible to display a more beautiful image by securing the above-mentioned minimum wavelength band. .

  The advantages of selecting B, C, Y, and R in selecting the four primary colors will be described. The cyan color in the vicinity of 500 nm does not have a strong spectrum as a light source, but is suitable for enlarging color coordinates because the color tone is significantly different from other B, Y, and R colors.

(Example 2)
A second embodiment of the present invention will be described with reference to the schematic configuration diagram of the image display apparatus of FIG. The difference from the first embodiment is that the incident-side polarizing plate 114 and the incident-side wavelength-selective phase difference plate 115 are arranged closer to the light source than the optical path separation element 113.

  Natural light including the four primary colors B, C, Y, and R emitted from the light source 1 passes through the illumination optical system 2 and is polarized to p-polarized light.

  FIG. 12 shows the characteristics of the wavelength selective phase difference plate 115. The wavelength-selective phase difference plate 115 has the wavelength band of Y light and R light as a phase-added band, and gives a phase corresponding to a half wavelength to the Y light and R light. In other words, the wavelength selective retardation plate 115 rotates the polarization directions of the Y light and the R light. On the other hand, the wavelength bands of the B light and the C light are non-phase-added bands and do not give a phase to the B light and the C light. In other words, the wavelength selective phase difference plate 115 does not rotate the polarization directions of the B light and the C light. As a result, the R light and Y light that have passed through the wavelength selective phase difference plate 115 are converted from p-polarized light to s-polarized light, and the B light and C light pass through the p-polarized light and enter the optical path separation element 113.

  The optical path separation element 113 is a dichroic mirror made of a dielectric multilayer film. The reflectance characteristic is shown in FIG. In FIG. 13, the solid line indicates the characteristic of s-polarized light, and the dotted line indicates the characteristic of p-polarized light. As shown in FIG. 13, the reflection bandwidth is wider for s-polarized light than for p-polarized light. This is a characteristic of a general dielectric multilayer film. When used at oblique incidence, the effective refractive index of the film material is large for s-polarized light and small for p-polarized light, so the reflection bandwidth is s-polarized rather than p-polarized. Is wider.

  In the wavelength band indicated by A in FIG. 13, the optical path separation element 113 reflects s-polarized light and transmits p-polarized light. That is, in the band A, the optical path separation element 113 has a function of a polarization separation element.

  In this embodiment, this point is utilized. As described in Example 1, the wavelength selective phase difference plate has a boundary band, and the wavelength of the boundary band becomes elliptically polarized light, leading to a decrease in contrast. In Example 1, the contrast is improved by applying the light in the boundary band to the wavelength band of another optical path. In the present embodiment, since the boundary band is at the boundary between adjacent primary color lights such as the C light and the Y light, the same method as in the first embodiment cannot be used. Although it is possible to make the boundary band narrower to some extent by increasing the number of laminated wavelength selective phase difference plates, it is difficult to make the boundary band zero as described above.

  Therefore, in this embodiment, the generation of light that lowers the contrast is suppressed by using the difference in reflection bandwidth between the p-polarized light and the s-polarized light of the dichroic mirror. In the following description, λ1, which is one wavelength in the boundary band, is used as a representative example.

  It is assumed that λ1 is a wavelength at which a phase difference of a quarter wavelength is given in the boundary band of the wavelength selective phase difference plate 115 on the incident side. λ1 passes through the wavelength selective phase difference plate 115 on the incident side, and then becomes circularly polarized light and enters the optical path separation element 113. In FIG. 13, λ1 exists in the wavelength band A. That is, the light having the wavelength of λ 1 that is circularly polarized light is separated into s-polarized light and p-polarized light by the optical path separation element 113. That is, s-polarized light λ1 is reflected by the optical path separation element 113 and acts as Y light. On the other hand, p-polarized light λ1 is transmitted through the optical path separation element 113 and used as C light. That is, although the wavelength is the same λ1, half is used as Y light and the other half is used as C light.

  Compared with the first embodiment, although the color purity of a single color is slightly reduced, the number of wavelength-selective retardation plates that are equivalent in brightness and relatively expensive can be reduced.

  Now, let the Y-light and B-light optical paths reflected by the optical path separation element 113 be the first optical path, and the transmitted R-light and C-light optical paths be the second optical path. Polarization separation elements 116a and 116b are disposed in the first optical path and the second optical path, respectively. In the present embodiment, plate-shaped wire grid reflection type polarizing elements are used as these polarization separating elements. By using this wire grid reflection type polarizing element, since the polarization disturbance caused by the prism glass can be reduced, the contrast can be further improved. The wire grid reflection type polarization element can arbitrarily select the polarization direction to be reflected by rotating the reflection axis. In this embodiment, however, the s-polarized light is reflected in the same manner as the polarization separation element of the dielectric multilayer film. Set to transmit p-polarized light.

  In this embodiment, since the polarization of the B light and the C light has already been rotated by the wavelength selective phase difference plate 115 before entering the optical path separation element 113, the Y light is s-polarized light and B light in the first optical path. The light is p-polarized light, the R light is s-polarized light, and the C light is p-polarized light in the second optical path.

  Therefore, in the first optical path, the polarization separation element 116a reflects Y light and transmits B light, and guides it to the reflective liquid crystal display elements 7Y and 7B. Since the polarization of the light that becomes the image light is rotated at the time of reflection, the image light of the Y light is transmitted by the polarization separation element 116a, the image light of the B light is reflected, and the wavelength selective phase difference plate on the emission side is reflected. Head for 118a.

  The characteristics of the wavelength-selective retardation plate 118a on the emission side are as shown in FIG. 14, and the B light has a phase addition band and the Y light has a non-phase addition band. In other words, the wavelength selective retardation plate 118a rotates the polarization direction of the B light. Since the boundary band is in the wavelength band of the C light, the light with the wavelength λ1 belongs to the non-phase added band as with the Y light. Therefore, the B-light is converted into p-polarized light by the wavelength-selective retardation plate 118a, and the Y-light including λ1 is emitted as p-polarized light. The B light and Y light emitted from the wavelength selective phase difference plate 118a pass through the emission-side polarizing plate 119a toward the optical path synthesis element 110.

  In the second optical path, the R light is reflected by the polarization separation element 116b, the C light is transmitted, and enters the reflective liquid crystal display elements 7R and 7C. Since the polarization of the light that becomes the image light is rotated by the reflective liquid crystal display elements 7R and 7C, the image light of the R light is transmitted through the polarization separation element 116b, and the image light of the C light is reflected and exits. Toward the wavelength selective phase difference plate 118b.

  FIG. 15 shows characteristics of the wavelength selective phase difference plate 118b on the emission side. R light is a phase addition band, and C light is a non-phase addition band. In other words, the wavelength selective phase difference plate 118b (third wavelength selective phase difference plate) rotates the polarization direction of the R light. Since the boundary band is in the wavelength band of Y light, λ1 belongs to the non-phase-added band like C light. Accordingly, the R light is converted into s-polarized light, and the C light including λ1 passes through the output-side polarizing plate 119b while being s-polarized, and travels toward the optical path combining element 110.

  In this embodiment, the optical path synthesis element 110 is a wire grid reflection type polarization element. Since the Y light and B light in the first optical path are p-polarized light, they pass through the optical path combining element 110, and the R light and C light in the second optical path are s-polarized light, so they are reflected by the optical path combining element 110 and are combined. . The synthesized image light of the four primary colors is projected on the screen by the projection lens 11.

  In this example, an optical path separation element using a dichroic film was used on the light emitting side of the wavelength selective phase difference plate. As a result, even if primary wavelength light having wavelength bands adjacent to each other is incident on the wavelength selective phase difference plate, the light in the boundary band is lost in the middle. Or reach the screen without ghost light. Therefore, a bright image can be displayed.

(Example 3)
A third embodiment of the present invention will be described with reference to the schematic configuration diagram of the image display apparatus in FIG. The difference from the second embodiment is that a dichroic filter that reflects light in the boundary band is disposed between the wavelength selective phase difference plate 115 and the light source 1.

  Each color light emitted from the light source 1 passes through the illumination optical system 2 and is aligned with p-polarized light. The characteristics of the dichroic filter 12 are shown in FIG. The dichroic filter 12 has a characteristic of reflecting light in the boundary band between Y light and C light.

  On the light exit side of the dichroic filter 12, a wavelength selective phase difference plate 115 on the incident side is disposed. The characteristics of the wavelength selective phase difference plate 115 are shown in FIG. The boundary band between the phase addition band and the non-phase addition band of the wavelength selective phase difference plate 115 and the reflection band of the dichroic filter 12 are matched. That is, light in a wavelength band that becomes elliptically polarized light when passing through the wavelength selective phase difference plate 115 is previously removed by the dichroic filter 12.

  The Y light and B light that have passed through the dichroic filter 12 are reflected by the optical path separation element 113. The R light and the C light are transmitted through the optical path separation element 113. The characteristics of the optical path separation element 113 are shown in FIG. The optical paths of Y light and B light reflected by the optical path separation element 113 are defined as the first optical path, and the optical paths of the transmitted R light and C light are defined as the second optical path.

  Polarization separation elements 116a and 116b are disposed in the first optical path and the second optical path, respectively. In the present embodiment, wire grid reflection type polarization elements are used as these polarization separation elements as in the second embodiment.

  Since the polarization of the B light and the C light has already been rotated by the wavelength-selective phase difference plate 115 arranged on the light incident side of the optical path separation element 113, the Y light is s-polarized and the B light is In p-polarized light, R light is s-polarized light and C light is p-polarized light in the second optical path.

  Accordingly, the Y light is reflected by the polarization separation element 116a in the first optical path, and the B light is transmitted and enters the reflective liquid crystal display elements 7Y and 7B. The image light modulated by the reflective liquid crystal display elements 7Y and 7B is synthesized by the polarization separation element 116a and travels to the optical path synthesis element 160.

  In the second optical path, the R light is reflected by the polarization separation element 116b, and the C light is transmitted through the polarization separation element 116b and is incident on the reflective liquid crystal display elements 7R and 7C. The image light modulated by the reflective liquid crystal display elements 7R and 7B is combined by the polarization separation element 116b and travels to the optical path combining element 160.

  The optical path combining element 160 is a dichroic mirror having the characteristics shown in FIG. 20, and combines the optical paths of the four primary colors.

  The wavelength selective phase difference plate 168 on the emission side has the characteristics shown in FIG. The boundary band is the same as that of the wavelength selective phase difference plate 115 on the incident side, and the light in that band has already been removed by the dichroic filter 12. Finally, all the color lights are aligned with the s-polarized light, and are projected by the projection lens 11 in a state where the polarization degree is increased by the output side polarizing plate 169.

  In this embodiment, light in the boundary band of the wavelength-selective phase difference plate is removed in advance, so that some light loss occurs. However, the configuration can be simplified, and the number of parts can be reduced and the size can be reduced. Is possible.

  In this embodiment, the dichroic filter 12 is used, but an element that absorbs light in the boundary band may be used.

Example 4
This embodiment is illustrated in FIG. The basic configuration of the present embodiment is the same as that of the first embodiment, but differs in that light is incident on the optical path separation element 31 from two directions substantially orthogonal to each other. In this embodiment, the B light and the C light are incident on the optical path separating element 31 from the upper side of the paper, and the Y light and the R light are incident on the left side of the paper. This is an example in which a light source such as a light emitting diode that is not white but has a finite spectrum in a certain wavelength band is used. That is, the light source 1A (first light source) that emits the B band and the C band is used on the upper side of the paper, and the light source 1B (second light source) that emits the Y band and the R band is used on the left side of the paper. As such a light source, in addition to the light emitting diode, a phosphor that emits light when excited by laser light can be used. Light emitted from these light sources enters the optical path separation element 31 in the S-polarized state.

  The characteristics of the optical path separation element 31 are shown in FIG. The optical path separation element 31 is a dichroic mirror that transmits C light and Y light and reflects R light and B light. As a result, the B light and the Y light are directed to the polarization separation element 6a in the right direction of the paper, and the C light and the R light are directed to the polarization separation element 6b in the downward direction of the paper. Since the subsequent description is the same as that of the first embodiment, a description thereof will be omitted. With this configuration, the characteristics of the optical path separation element 31 can be simplified, and the entire apparatus can be reduced in size by a light source such as a light emitting diode.

  In the fourth embodiment, the light source 1A that emits light in a wavelength band including the B band and the C band is used. However, the present invention is not limited to this, and the light source that emits the B band and the light source that emits the C band are used. The form arrange | positioned in a position may be sufficient. The same applies to the light source 1B.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist. For example, it can be applied to a configuration using five or more primary colors. Moreover, it is also possible to apply to a wavelength band including ultraviolet light and infrared light other than visible light.

DESCRIPTION OF SYMBOLS 1 Light source 3 Optical path separation element 5a, 5b Wavelength selective phase difference plate 6a, 6b Polarization separation element 7Y, 7B, 7R, 7C Reflective liquid crystal panel 10 Optical path composition element 11 Projection lens

Claims (11)

An optical path separation element that separates light emitted from the light source into first color light and third color light, and second color light and fourth color light;
A first wavelength-selective phase plate that rotates the polarization direction of any one of the first color light and the third color light separated by the optical path separation element;
A second wavelength-selective phase difference plate that rotates the polarization direction of one of the second color light and the fourth color light separated by the optical path separation element;
The first color light emitted from the first wavelength selective phase difference plate is guided to a first reflection type light modulation element, and the third color light emitted from the first wavelength selective phase difference plate is designated as a third reflection type. A first polarization separation element that guides to a light modulation element and synthesizes image light modulated by the first and third reflective light modulation elements;
The second color light emitted from the second wavelength selective phase difference plate is guided to a second reflection type light modulation element, and the fourth color light emitted from the second wavelength selective phase difference plate is designated as a fourth reflection type. A second polarization separation element that guides to the light modulation element and synthesizes the image light modulated by the second and fourth reflective light modulation elements;
An optical path synthesis element that synthesizes image light emitted from the first polarization separation element and the second polarization separation element;
The image display device according to claim 1, wherein the first color light to the fourth color light are first, second, third, and fourth color lights in order from the short wavelength side. An optical path separation element that separates light emitted from the light source into first color light and third color light, and second color light and fourth color light;
A wavelength-selective retardation plate that is disposed between the light source and the optical path separation element, and rotates a polarization direction of the first color light and the second color light, or the third color light and the fourth color light;
The first color light separated by the optical path separation element is guided to a first reflective light modulation element, the third color light separated by the optical path separation element is guided to a third reflective light modulation element, and the first And a first polarization separation element that synthesizes the image light modulated by the third reflective light modulation element,
The second color light separated by the optical path separation element is guided to a second reflective light modulation element, the fourth color light separated by the optical path separation element is guided to a fourth reflective light modulation element, and the second And a second polarization separation element that synthesizes the image light modulated by the fourth reflective light modulation element,
An optical path synthesis element that synthesizes image light emitted from the first polarization separation element and the second polarization separation element;
The image display device according to claim 1, wherein the first color light to the fourth color light are first, second, third, and fourth color lights in order from the short wavelength side.   3. The device according to claim 2, further comprising an element that is disposed between the wavelength-selective retardation plate and the light source and absorbs or reflects light in a wavelength band between the second color light and the third color light. The image display device described. The first wavelength that rotates the polarization direction of either the first color light and the second color light or the third color light and the fourth color light among the first color light to the fourth color light included in the light emitted from the light source. A selective retardation plate;
The light that has passed through the first wavelength selective phase difference plate is separated into the first color light, the third color light, the second color light, and the fourth color light, and the second color light and the third color light. An optical path separation element that reflects s-polarized light in a wavelength band between colored lights and transmits p-polarized light in a wavelength band between the second color light and the third color light;
The light separated by the optical path separation element is incident, and the incident light is guided to the first and third reflection type light modulation elements according to the polarization direction of the incident light, and the first and third reflection types are guided. A first polarization separation element that combines image light modulated by the light modulation element;
The light separated by the optical path separation element is incident, and the incident light is guided to the second and fourth reflective light modulation elements according to the polarization direction of the incident light, and the second and fourth reflective types A second polarization separation element that synthesizes image light modulated by the light modulation element;
An optical path combining element that combines image light emitted from the first polarization separation element and the second polarization separation element;
A second wavelength-selective retardation plate that is disposed between the first polarization separation element and the optical path synthesis element and rotates the polarization direction of the first color light;
The second polarization component is disposed between the element and the optical path synthesis element, and has a third wavelength-selective phase plate that rotates the polarization direction of the fourth color light,
The image display device according to claim 1, wherein the first color light to the fourth color light are first, second, third, and fourth color lights in order from the short wavelength side. A first reflective light modulation element for modulating the first color light;
A second reflective light modulation element for modulating the second color light;
A third reflective light modulation element for modulating the third color light;
A fourth reflective light modulation element for modulating the fourth color light;
5. The image display device according to claim 1, comprising:   6. The image according to claim 1, wherein the first color light is blue, the second color light is cyan, the third color light is yellow, and the fourth color light is red light. Display device. The first color light includes a wavelength band of 450 to 470 nm,
The second color light includes a wavelength band of 500 to 520 nm,
The third color light includes a wavelength band of 540 to 560 nm,
The image display device according to claim 1, wherein the fourth color light is color light including a wavelength band of 610 to 630 nm.   The image display apparatus according to claim 1, further comprising a projection optical system that projects light combined by the optical path combining element onto a projection surface. A first light source that emits the first and second color lights;
A second light source for emitting the third and fourth color lights;
The light emitted from the first light source and the second light source is incident on the optical path separation element from different directions,
9. The image display device according to claim 1, wherein the optical path separation element reflects the second and third color lights and transmits the first and fourth color lights. 10. A first light source that emits the first and second color lights;
A second light source for emitting the third and fourth color lights;
The light emitted from the first light source and the second light source is incident on the optical path separation element from different directions,
9. The image display device according to claim 1, wherein the optical path separation element transmits the second and third color lights and reflects the first and fourth color lights. 10.   11. The image display device according to claim 9, wherein the first and second light sources are phosphors excited by light emitting diodes or lasers.

Images