JP2003202558A - Picture display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve bright picture display by using a bright illumination optical system having a low f-number and also preventing the lowering of light utilization efficiency in a color separation and synthesizing element. <P>SOLUTION: The display device is equipped with an illumination optical system 2 for illuminating a spatial optical modulation element 1 having a reflection electrode, and a projection lens 3 for forming the image of the element 1. One circular polarizer 4 is disposed corresponding to one element 1. The circular polarizer 4 functions as a polarizer for luminous flux made incident on the element 1 from the optical system 2, and functions as an analyzer for luminous flux reflected by the element 1 and made incident on the lens 3. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device for displaying an image by projecting an image of a spatial light modulator on a screen or the like with a projection lens.

[0002]

2. Description of the Related Art Conventionally, there has been proposed an image display device which has a spatial light modulator and projects an image of the spatial light modulator onto a screen or the like by a projection lens to display an image.
For example, as shown in FIG. 38, an illumination optical system 102 having a light source such as a discharge lamp is provided, and the illumination optical system 102 illuminates a spatial light modulation element 103 using polarized light such as liquid crystal, and this spatial light is emitted. The image of the modulator 103 is projected onto the projection lens 10
The projection type image display device for projecting onto a screen (not shown) by 4 has been put to practical use as a large-sized image display device.

As the spatial light modulator, a reflective spatial light modulator having a reflective electrode is used.
Such a reflection type spatial light modulator is excellent in that the aperture ratio can be increased, and the miniaturization and high definition can be achieved.

In this image display device, a polarization beam splitter (PBS) 105 is generally used as a polarizer and an analyzer. That is, the light flux emitted from the illumination optical system 102 enters the polarization beam splitter 105, which is a polarizer, and only the component in a specific polarization direction is selected and enters the spatial light modulator 103.

Then, the polarization beam splitter 105
A dichroic prism 106 is provided as a color separation / combination element between the spatial light modulator 103 and the spatial light modulator 103. That is, the illumination light that has passed through the polarization beam splitter 105 is
In the dichroic prism 106, R (red),
Color separation is performed into G (green) and B (blue) color components.
Then, each color component has a corresponding spatial light modulator 103,
It is incident on 103, 103, is polarization-modulated, and is reflected.

Each spatial light modulator 103, 103, 103
The reflected light fluxes from are subjected to color combination in the dichroic prism 106 and enter the polarization beam splitter 105. Here, the polarization beam splitter 105 acts as an analyzer and transmits only a specific polarization component, thereby converting the polarization modulation in each of the spatial light modulators 103, 103, 103 into intensity modulation. When the light beam whose intensity is thus modulated enters the projection lens 104, the respective spatial light modulators 103, 103, 103
The image corresponding to the modulation in is projected and displayed on the screen.

[0007]

In the image display device as described above, the polarization beam splitter used as a polarizer and an analyzer has a reflectance of P-polarized light and S-polarized light at the interface of the dielectric multilayer film. The polarization component is selected according to the difference between, and the wavelength dependence and angle dependence of the incident light are large.

Therefore, in this image display device,
It is difficult to use a bright illumination optical system having a low F number, and it is difficult to improve the light utilization efficiency.

Further, in the above-mentioned image display device, the dichroic prism used as the color separation / combination element has a large polarization dependency.

Therefore, since the characteristics of the dichroic surface for the incident light (S-polarized light) and the emitted light (P-polarized light) are different, the light utilization efficiency is lowered.

Therefore, the present invention has been proposed in view of the above-mentioned circumstances, and it is possible to use a bright illumination optical system having a low F number, and to reduce the light utilization efficiency of the color separation / combination element. It is an object of the present invention to provide an image display device that is capable of displaying a bright image that is prevented.

[0012]

In order to solve the above-mentioned problems, an image display apparatus according to the present invention is an illumination optical system including a spatial light modulator having a reflective electrode and a light source for illuminating the spatial light modulator. And a projection lens on which the spatial light modulation element forms an image, and one circular polarization plate is provided corresponding to one spatial light modulation element.

Further, in this image display device, the circularly polarizing plate functions as a polarizer for a light flux entering the spatial light modulation element from the illumination optical system, and is reflected by the spatial light modulation element to be projected onto the projection lens. It is characterized in that it functions as an analyzer for the light flux incident on.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the image display apparatus according to the present invention illuminates the reflective liquid crystal modulator 1 which is a spatial light modulator (light valve) having a reflective electrode, and the liquid crystal modulator 1. The projection type image display device includes an illumination optical system 2 and a projection lens 3 that forms an image of the liquid crystal modulator 1. The illumination optical system 2 has a light source such as a discharge lamp (not shown), and is configured to irradiate the liquid crystal modulation element 1 with the light flux emitted by this light source by a plurality of optical elements.

In this image display device, a circularly polarizing plate 4 is provided corresponding to the liquid crystal modulator 1. This circularly polarizing plate 4 is arranged corresponding to one liquid crystal modulation element 1 and fulfills the function of a polarizer with respect to the light flux incident on the liquid crystal modulation element 1 from the illumination light source 2. ,
The light flux reflected by the liquid crystal modulator 1 and incident on the projection lens 3 functions as an analyzer.

The projection lens 3 forms an image of the liquid crystal modulator 1
An image is projected and projected on a screen (not shown).

[Method of Modulating Liquid Crystal Using Circular Polarizing Plate] In this image display device, the incident luminous flux is modulated by one circular polarizing plate 4 and the liquid crystal modulation element 1.

For example, assuming that the light transmitted through the circularly polarizing plate 4 is left-handed circularly polarized light (LCP), the phase of the light beam reflected by the reflecting surface electrode without changing the phase in the liquid crystal layer of the liquid crystal modulator 1. 180 ° change, clockwise circularly polarized light (RC
P), it does not pass through the circularly polarizing plate 4.

That is, by causing a phase change of 0 ° to 90 ° in the liquid crystal layer of the liquid crystal modulation element 1, the light flux transmitted through the circularly polarizing plate 4 through the liquid crystal modulation element 1 has a black level to a white level. It is possible to perform modulation up to. Then, in the liquid crystal modulator 1, it is possible to display an image on the screen by causing a predetermined phase change for each pixel.

[Circular Polarizing Plate] The circular polarizing plate 4 can be composed of a linear polarizing plate and a ¼λ (wavelength) plate. As the linear polarizing plate, an absorption type linear polarizing plate that absorbs linearly polarized light in one predetermined direction and transmits polarized light in the other direction,
Further, it may be any of a reflection type linear polarization plate that reflects linearly polarized light in one predetermined direction and transmits polarized light in the other direction.

As the circularly polarizing plate 4, it is also possible to use a reflective circularly polarizing plate made of a cholesteric liquid crystal polymer.

[Structure of Optical System] In this image display device, as shown in FIGS. 2 and 3, by using a so-called decentered optical system, a more compact optical system can be obtained. That is, the field lens 5 in the illumination optical system 2 also has the function of the field lens of the projection lens 3. This field lens 5
The reflective surface of the liquid crystal modulator (spatial light modulator) 1 is arranged for the purpose of forming a telecentric optical system.
The optical axis of the field lens 5 is appropriately shifted with respect to the optical axis of the projection lens 3, or the reflective surface of the liquid crystal modulation element 1 is changed with the optical axis of the field lens 5 and the optical axis of the projection lens 3 being matched. By obliquely tilting the projection lens 3 with respect to the optical axis, oblique illumination of the liquid crystal modulator 1 can be realized.

There are two possible configurations depending on the positional relationship between the field lens 5 and the circularly polarizing plate 4. That is,
The circularly polarizing plate 4 is arranged between the field lens 5 and the liquid crystal modulator 1, and the circularly polarizing plate 4 is arranged between the field lens 5 and the projection lens 3.

[Contrast lowering factor] 1 for the circularly polarizing plate 4
In an image display device having a single-use configuration, there are several factors that reduce the contrast of a display image.

That is, when the illumination light flux from the illumination optical system 2 is reflected by the interface before passing through the circularly polarizing plate 4 and directly enters the projection lens 3, the contrast of the display image is lowered.

Regarding reflection at each interface between the circularly polarizing plate 4 and the reflection surface of the liquid crystal modulation element 1, if there is a difference in reflectance between the P-polarized light and the S-polarized light, the reflection surface of the liquid crystal modulation element 1 is different. Reflected light deviates from circularly polarized light. When such a shift occurs, the contrast of the display image is reduced.

Further, the contrast of the displayed image is also lowered depending on the incident angle characteristic of the circularly polarizing plate 4 and the incident angle characteristic of the liquid crystal modulator 1.

When a reflective circularly polarizing plate is used, unnecessary light during black level display is not absorbed by this circularly polarizing plate. In this case, the polarized light component in one predetermined direction of the light flux reaching the reflective circularly polarizing plate from the illumination optical system 2 passes through this reflective circularly polarizing plate, and the polarized component in the other direction is reflected. . When the light flux reflected by the circularly polarizing plate enters the entrance pupil of the projection lens 3 in this way, it reduces the contrast of the display image.

Further, the light flux which is not modulated by the liquid crystal layer of the liquid crystal modulation element 1 and is incident on the reflective circularly polarizing plate, and which is reflected again toward the liquid crystal modulation element 1 by this reflective circularly polarizing plate is further reflected by this liquid crystal. When reflected by the reflective surface of the modulator 1, it becomes circularly polarized light that passes through the reflective polarizing plate. Therefore, such a light flux is incident on the projection lens 3 and reduces the contrast of the display image.

[Contrast Improvement Method] In order to improve the contrast of the displayed image, the generation of the reflected light flux in each optical component as described above is suppressed, or the reflected light flux in each optical component is incident on the entrance pupil of the projection lens. It is necessary to prevent it from entering.

First, the most problematic reflection at the interface between optical components is the reflection at the interface between air and the optical component. The arrangement of the optical system can prevent such reflected light flux from entering the entrance pupil of the projection lens.

That is, as shown in FIGS. 4 and 5, when the circularly polarizing plate 4 is disposed between the field lens 5 and the liquid crystal modulator 1, the optical path from the field lens 5 to the circularly polarizing plate 4 is changed. Optical coupling of each part to eliminate the interface with air.
Good to do.

Further, in order to reduce the surface reflection of the field lens 5, it is not enough to add the antireflection film. It is preferable that the field lens 5 is a plano-convex lens, and the plane side is directed to the liquid crystal modulation element 1 side for optical coupling with other components.

Whether or not the surface-reflected light (the surface-reflected light ray group R) on the convex surface of the field lens 5 lowers the contrast of the display image is determined by the surface-reflected light at the entrance pupil of the projection lens 3. It can be evaluated by whether or not it enters (whether or not it overlaps the projection ray group P). The reflection direction of the surface-reflected light on the field lens 5 changes depending on the shift direction and the shift amount of the field lens 5 and the position of the liquid crystal modulation element 1. It is possible to prevent the surface reflected light from entering the entrance pupil of the projection lens 3.

Further, as shown in FIGS. 6 and 7, when the circularly polarizing plate 4 is arranged between the field lens 5 and the projection lens 3, it is arranged between the projection lens 3 and the circularly polarizing plate 4. By filling the existing space with the optical component 6 made of a material having a refractive index close to that of other optical components, it is possible to prevent the surface-reflected light from the circularly polarizing plate 4 from entering the projection lens 3.

Next, there is no difference in reflectance between P-polarized light and S-polarized light at each interface in the liquid crystal modulator 1, and the phase change is 18
If it is 0 °, the reflected light from the liquid crystal modulation element 1 becomes a completely circularly polarized light and is blocked by the circularly polarizing plate 4, so that it does not enter the projection lens 3. However, in reality, the reflection at each interface shows different reflectances for P-polarized light and S-polarized light depending on the incident angle, and shows a phase change depending on the thickness of each layer.

A general liquid crystal modulation element 1 has a structure in which a transparent substrate, a transparent electrode, an alignment film, a liquid crystal layer, an alignment film and a reflective electrode are sequentially laminated. Here, when the liquid crystal layer does not modulate the incident light flux (black level), if the absorption of each layer is ignored, the final P as the liquid crystal modulation element 1 is obtained.
The reflectance of polarized light and S-polarized light is 100%,
Only the phase change matters. In order that the phase change of P-polarized light and S-polarized light does not pose a problem, the thickness of the transparent electrode and the alignment film should be such that the difference in reflectance between P-polarized light and S-polarized light at each interface and the difference in optical path length due to layer thickness can be ignored. The thickness is made sufficiently thin, or an antireflection condition or a reflection increasing condition is set.

Therefore, the product (nd: optical film thickness) of each film thickness (d) and the refractive index (n) in the liquid crystal modulator 1 is
It is good to make it an integral multiple of 1 / 4λ. To be thin enough,
The optical thickness of the thin film such as the transparent electrode and the alignment film is about 1 / 8λ or less. It is desirable to add an antireflection film also to the interface between the transparent substrate and air. Or
It is desirable to optically couple between the circularly polarizing plate 4 and the liquid crystal modulation element 1.

In addition, the metallic material used for the actual reflecting electrode has some absorption, and in that case, there is a difference in the P-polarized light reflectance and the S-polarized light reflectance. In that case, it is possible to correct the difference between the P-polarized light and S-polarized light reflectance in the reflective electrode under the phase condition by appropriately adjusting the film thicknesses of the alignment film and the transparent electrode.
Further, by disposing the reflection increasing film on the metal reflection electrode, it is possible to reduce the difference in reflectance. The reflection-increasing film can be composed of a dielectric multilayer film.

In the circularly polarizing plate 4 which is a combination of the linearly polarizing plate and the retardation plate, the three-dimensional refractive index control of the retardation plate is performed so that the circularly polarizing plate 4 functions as a circularly polarizing plate at a wide incident angle. It should be set to.

Further, in the circularly polarizing plate 4 made of a cholesteric liquid crystal (CLC) polymer, a wavelength longer than the design wavelength is compensated so as to compensate for so-called blue shift in which the selective reflection wavelength range shifts to the blue side when obliquely incident. By adjusting the pitch so as to cause selective reflection even in the region and laminating a retardation plate that compensates for the birefringence generated in the cholesteric liquid crystal, it is possible to function as a circularly polarizing plate even at a wide incident angle. To do.

Further, in the liquid crystal modulation element 1, by combining the retardation plates so as to compensate the retardation of the liquid crystal layer, the angle dependence at the black level can be compensated.

When a reflection type polarization plate is used as the circular polarization plate 4, as shown in FIGS. 8 and 9, unnecessary light in this reflection type polarization plate is changed to a liquid crystal modulation element. The unnecessary light can be prevented from entering the entrance pupil of the projection lens 3 by inclining the reflecting surface of No. 1 by an appropriate angle.

For example, as shown in FIG. 8, when the circularly polarizing plate 4 is disposed between the field lens 5 and the liquid crystal modulation element 1, the F number of the illumination optical system 3 is 2.
4 (the incident angle of the illumination light beam is ± 12 °), it is preferable to incline the circularly polarizing plate 4 by 12 ° or more in terms of air.

That is, of the illumination light from the illumination optical system 2, the luminous flux reflected on the surface of the circularly polarizing plate 4 which is a reflective polarizing plate, is reflected by the circularly polarizing plate 4 with respect to the reflecting surface of the liquid crystal modulator 1. Since it is tilted, the light does not enter the entrance pupil of the projection lens 3. A light beam which is not modulated by the liquid crystal layer of the circularly polarizing plate 4 is reflected by the circularly polarizing plate 4 which is a reflective polarizing plate, is reflected again by the liquid crystal modulation element 1, and becomes circularly polarized light which passes through the circularly polarizing plate 4. . At this time, since the circularly polarizing plate 4 is tilted by 12 °, when the reflected light from the circularly polarizing plate 4 enters the liquid crystal modulator 1 again,
The incident angle is changed by 24 °. Therefore, the light flux reflected again by the liquid crystal modulator 1 is off the angle of incidence on the entrance pupil of the projection lens 3 and does not lower the contrast of the displayed image.

Further, as shown in FIG. 9, even when the circular polarizing plate 4 is disposed between the field lens 5 and the projection lens 3, the circular polarizing plate 4 which is a reflection type polarizing plate is subjected to liquid crystal modulation. By inclining the reflecting surface of the element 1 by an appropriate angle, it is possible to prevent unnecessary light from entering the entrance pupil of the projection lens 3. In this case, since the field lens 5 is interposed between the circularly polarizing plate 4 and the liquid crystal modulation element 1, the inclination angle of the circularly polarizing plate 4 is not necessarily larger than the incident angle of the illumination light. The effect is achieved.

Here, the angle at which the circularly polarizing plate 4 should be tilted is the F number of the illumination optical system 2, the shift amount of the optical axis of the field lens 5, the tilting angle of the liquid crystal modulator 1, and the circularly polarizing plate 4.
And the reflective surface of the liquid crystal modulator 1 are determined.

In the configuration in which the circularly polarizing plate 4 shown in FIGS. 8 and 9 is tilted, the circularly polarizing plate 4 is sandwiched between a pair of wedge-shaped optical elements 7, and the circularly polarizing plate 4 is an optical medium. By tilting the circular polarizing plate 4 inside, tilting the circularly polarizing plate 4 can prevent the characteristics of the projection lens 3 from being affected.

Example 1 As a more specific example of the image display device according to the present invention, as shown in FIG.
Using the liquid crystal modulator 1 which is a single-plate spatial light modulator,
Existing structures such as a structure in which RGB (red, green, blue) color filters are formed on the substrate of the liquid crystal modulator 1 for colorization, a structure using a microlens array and a color separation filter, a structure combined with a field sequential color display device, etc. It can be configured by combining with the technology of.

In this image display device, the illumination optical system 2
Includes a light source 10 including a parabolic mirror 8 and a discharge lamp 9, a pair of fly-eye integrators 13 and a condenser lens 14 which are sequentially arranged on the optical axis. A phase difference plate array 11 is arranged between the light source 10 and the fly eye integrator 13. A reflective polarizing plate 12 is arranged between the fly-eye integrator 13 and the condenser lens 14. The phase difference plate array 11 and the reflective polarizing plate 12 cause the return light from the reflective polarizing plate 12 to be S-polarized with respect to the incident surface of the parabolic mirror 8. That is, the illumination optical system 2 has a polarization conversion function.

In this image display device, the field lens 5 is shifted with respect to the optical axis of the projection lens 3. The field lens 5 is optically coupled to the circular polarization plate 4 including an absorption type linear polarization plate and a 1 / 4λ plate. The purpose of the optical coupling here is to reduce reflection at the interface as much as possible. Therefore, the field lens 5 is made of a material having a refractive index close to that of the protective layer of the circularly polarizing plate 4, and these are adhered by an adhesive material having a refractive index close to each other. An antireflection film is added to the air interface of the 1/4 λ plate of the circularly polarizing plate 4 on the liquid crystal modulation element 1 side. Also,
If reflection at the interface between the absorption type polarizing plate and the ¼λ plate poses a problem, an antireflection film is added to this interface as well.
Stick with adhesive material. Fixing with an adhesive material is more effective than fixing with an adhesive in preventing the deterioration of characteristics of the absorption type polarizing plate and 1 / 4λ due to the difference in expansion coefficient with temperature rise.

1 / 4λ has a two-layer structure of a 1 / 2λ plate and a 1 / 4λ plate for widening the band, and has a linear polarizing plate of -1 / 2λ.
The plate and the -1/4? Plate are laminated in this order. The slow axis azimuth is 15 ° with respect to the polarizing plate transmission axis,
It was set to 75 °. Also, in order to improve the angle dependence, 3
The dimensional refractive index was adjusted so that the Nz coefficient was 0.5. The Nz coefficient is expressed as follows.

Nz = (nx-nz) / (nx-ny) (∵nx: slow layer axial refractive index, ny: advanced layer axial refractive index, nz:
Refractive Index in Thickness Direction) The liquid crystal layer of the liquid crystal modulation element 1 is in the VA mode (vertical alignment mode). Here, in the case of linearly polarized light input, it is necessary to pretilt the substrate orientation in order to regulate the liquid crystal director in the direction of 45 ° with the input polarization axis, but in the case of circularly polarized light input, the liquid crystal orientation direction is regulated. No need.

For example, in a microdisplay having a pixel pitch of 10 μm and a distance between pixels of about 0.6 μm, the electric field between the pixels has an electric potential of 0.
Due to the influence of the electric field formed by the potential of the light-shielding layer through the insulating layer of about 1 μm, the tilt direction is defined by the electric field, unlike the electric field near the center of the pixel. Therefore, a process for defining the orientation, that is, so-called rubbing or oblique vapor deposition of an inorganic orientation material is not necessary.

This liquid crystal layer has a thickness of 1.4 μm, Δn of 0.15, no of 1.48, ne of 1.63, and is made of a liquid crystal material having a negative dielectric anisotropy. I was there. Transparent electrode material (refractive index 1.82), alignment film material (refractive index 1.82).
The thicknesses of 6) were both set to 10 nm. For a wavelength of 530 nm, the optical path lengths are 0.034λ and 0.03λ, respectively.
Therefore, the film thickness is sufficiently thin. The reflective electrode material is Al (aluminum), and a reflection increasing film made of a dielectric multilayer film is formed on the surface thereof. Al electrode, SiO
_A total of four layers of ₂ , ₂ , TiO ₂ , SiO ₂ , and TiO ₂ are set to have a thickness of 1 / 4λ. On the transparent substrate,
A glass substrate having a refractive index of 1.52 is used.

In order to compensate the phase difference with respect to the obliquely incident light rays on the liquid crystal layer, the glass substrate of the liquid crystal modulation element 1 is provided with a retardation plate having a negative phase difference and a refractive index close to that of the glass substrate. It is pasted with the adhesive material.
The negative retardation means that the refractive index in the thickness direction is smaller than that in the surface direction, and Δnd is matched with Δnd of the liquid crystal layer. Further, an antireflection film is added to the air interface.

The polarization axis of the light emitted from the liquid crystal modulator 1 is
It is aligned with the transmission axis of the absorptive polarizing plate of the circular polarizing plate 4.
This reflective polarizing plate also functions as a pre-polarizing plate, and reduces the amount of light absorbed as unnecessary light in the absorptive polarizing plate. As a result, in addition to the effect of improving efficiency, it is possible to reduce the temperature rise of the absorption type polarizing plate and improve the reliability.

In this image display device, the modulated light flux from the liquid crystal modulation element 1 enters the projection lens 3 and is imaged on a screen (not shown) to display an image.

[Embodiment 2] Next, as shown in FIGS. 11 and 12, the image display device according to the present invention has RGB (red,
Green, blue) Three spatial light modulators 1R corresponding to the three primary colors,
A cross type dichroic prism 16 for color separation / synthesis of 1G and 1B and RGB may be used.

The cross type dichroic prism 16 is
Also serves as a color separation / synthesis element. The polarization axis in the illumination optical system 2 is set to be S-polarized with respect to the dichroic incident surface of the cross type dichroic prism 16. The cross-type dichroic prism 16 separates the incident light flux (illumination light flux) from the illumination optical system 2 into red, green, and blue, and combines the modulated light fluxes returned from the liquid crystal modulators 1R, 1G, 1B corresponding to the respective colors. To do.

On the side surface of the cross type dichroic prism 16 facing the liquid crystal modulators 1R, 1G, 1B, there are optical couplings of circular polarization plates 4, 4, 4 composed of an absorption type linear polarization plate and a wide band ¼λ plate. I am doing it.

Further, the cross type dichroic prism 1
A field lens 5 is optically coupled to a side surface of the lens 6 which faces the illumination optical system 2. Other configurations are the same as those in the above-described first embodiment.

The transmission axis of the absorptive linear polarizing plate forming each circularly polarizing plate 4 is set so as to be S-polarized with respect to the dichroic surface. This is because dichroic mirrors generally have excellent reflection characteristics for S-polarized light. Further, in the one-polarizer configuration, the emitted light is also S-polarized light, and therefore the light utilization efficiency in color separation / combination is not significantly reduced.

The white balance can be adjusted by rotating the transmission axis of the polarization element by an appropriate amount with respect to the polarization axis after passing through the dichroic prism.

[Embodiment 3] Next, as shown in FIG. 13, an image display apparatus according to the present invention is constructed by replacing the absorption type linear polarization plate with a reflection type polarization plate in the structure of the above-mentioned Embodiment 2. You may. Circular polarizing plate 4 having a reflective polarizing plate
Is sandwiched between a pair of wedge-shaped optical components 7 made of a material having the same refractive index as that of the cross-type dichroic prism 16, and an angle formed by the principal ray of the illumination light flux from the illumination optical system 2 with respect to the liquid crystal modulation element 1 is set. They are arranged so as to be orthogonal to each other.

For example, in the illumination optical system 2 having an F number of 2.4, the incident angle range to the projection lens 3 is about 1 ° so that the entire illumination angle range of ± 12 ° can be taken into the projection lens 3. I have a margin. That is, the illumination light beam is incident on the projection lens 3 even if it is tilted by 13 ° with respect to the optical axis of the projection lens 3. Therefore, the inclination angle of the circularly polarizing plate 4 is set to 8.5 ° so as to be orthogonal to the principal ray in a medium having a refractive index of 1.52.

The white balance can be adjusted by rotating the transmission axis of the polarization element by an appropriate amount with respect to the polarization axis after passing through the dichroic prism.

[Embodiment 4] Furthermore, as shown in FIG. 14, the image display apparatus according to the present invention has the same structure as in Embodiment 2 except that the position of the field lens 5 is set to the cross type dichroic prism 16 and each liquid crystal. Modulation elements 1R, 1G,
1B may be replaced and arranged.

Further, in this structure, the phase difference plate 15 for compensating for the phase difference in the liquid crystal phase of each liquid crystal modulation element 1R, 1G, 1B has the field lens 5 and each liquid crystal modulation element 1R, 1G, 1B. And the field lens 5, the retardation plate 15 and the liquid crystal modulators 1R, 1G and 1B are optically coupled.

Further, a dummy block 17 made of an optical material having the same refractive index as the cross type dichroic prism 16 is arranged between the cross type dichroic prism 16 and the projection lens 3. This dummy block 17
The cross type dichroic prism 16 is optically coupled.

White balance can be adjusted by rotating the transmission axis of the polarizing element by an appropriate amount with respect to the polarization axis after passing through the dichroic prism.

[Embodiment 5] Further, as shown in FIG. 15, the image display apparatus according to the present invention is constructed by using the circularly polarizing plate 4 having a reflective polarizing plate in the construction of the above-mentioned Embodiment 4. May be.

In this case, the field lens 5 is shifted with respect to the optical axis of the projection lens 3 and the liquid crystal modulators 1R and 1R are arranged in the same manner as in the above-described respective embodiments.
G and 1B are inclined with respect to the optical axis of the projection lens 3.

Here, the inclination angle of the circularly polarizing plate 4 may be smaller than that of the configuration of the above-mentioned third embodiment. That is,
In this embodiment, the F number of the illumination optical system 2 is 2.5,
The shift amount of the field lens 5 is 11 mm, the diameter of the fly-eye lens is 40 mm, and each liquid crystal modulator 1R, 1G, 1
The tilt angle of B is 5 °, the refractive index of the substrate of each liquid crystal modulation element 1R, 1G, 1B is 1.52, and from the reflective polarizing plate of the circular polarization plate 4 to the reflection surface of each liquid crystal modulation element 1R, 1G, 1B. Circularly polarizing plate 4 when the distance is 7 mm (air conversion)
The inclination angle may be about 1 °.

White balance can be adjusted by rotating the transmission axis of the polarizing element by an appropriate amount with respect to the polarization axis after passing through the dichroic prism.

[Embodiment 6] Furthermore, as shown in FIG. 16, the image display apparatus according to the present invention is a dichroic prism that separates only one of the three primary colors instead of the above-mentioned cross type dichroic prism 16. 18, a liquid crystal modulator 1R corresponding to one of the three primary colors is arranged facing one exit surface of the dichroic prism 18, and the other two surfaces of the three primary colors are opposed to the other one surface. The liquid crystal modulator 1GB corresponding to the above may be arranged.

In this case, for the liquid crystal modulation element 1GB corresponding to two colors, as a means for displaying two colors, a structure in which a color filter is formed on the substrate of the liquid crystal modulation element 1GB, a microlens array and a color separation filter are used. Configuration used,
It can be configured by combining with an existing color switching technique such as a configuration in which it is combined with a field sequential color display element. Position of field lens 5,
The configuration and the like of the circularly polarizing plate 4 are the same as those of the above-described second to fifth embodiments.
The configuration may be any of the above.

[Circular Polarizing Plate, Liquid Crystal Part Film Thickness Condition and Black Level] In this image display device, as shown in FIG.
In the case where the circularly polarizing plate 4 is composed of the linearly polarizing plate 19 and the 1 / 4λ plate 20, the 1 / 4λ plate 20 is used as the liquid crystal modulator 1.
Will be located on the side.

Here, as shown in FIG. 18, a part of the light transmitted through the linear polarizing plate 19 is reflected at the interface between the ¼λ plate 20 and the air. The reflectance here is
As shown in FIG. 19, P-polarized light and S-polarized light are different. That is, the reflectance Rs of S-polarized light increases as the incident angle increases, whereas the reflectance Rp of P-polarized light decreases as the incident angle increases. Therefore,
Part of the reflected light at the interface between the 1/4 λ plate 20 and the air is transmitted through the circularly polarizing plate 4 and causes a reduction in the contrast of the displayed image.

Therefore, as shown in FIG. 20, the contrast of the displayed image can be improved by adding the antireflection film 21 to the interface between the ¼λ plate 20 and the air layer. Also, by optically coupling the circularly polarizing plate 4 and other optical components, eliminating the air interface has the same effect. However, when the circularly polarizing plate 4 needs to be cooled, it is necessary to be in contact with the air layer, and therefore it is effective to provide the antireflection film 21.

The results of countermeasures against interface reflection on the premise that the optical component has an air interface will be described below.

The configuration in which the circular polarization plate 4 is arranged between the field lens 5 and the liquid crystal modulation element 1 and the configuration in which the field lens 5 is between the circular polarization plate 4 and the liquid crystal modulation element 1 are as follows. The characteristics required for the circularly polarizing plate 4 are different.

In the former configuration in which the circularly polarizing plate 4 is arranged between the field lens 5 and the liquid crystal modulation element 1, the angular distribution of the light flux passing through the circularly polarizing plate 4 is distributed to the liquid crystal modulation element 1. It coincides with the incident and outgoing angle distribution. And
As shown in FIGS. 21 and 22, the circularly polarizing plate 4 including the linearly polarizing plate and the broadband ¼λ plate in the above-described Example 1.
When circularly polarized light is incident on the right-handed circularly polarized light (RCP) and the left-handed circularly polarized light (LCP), the incident angle dependencies of the respective transmittances are different from each other. 21 and 22, the radial distance indicates the tilt angle of the incident light beam, and the azimuth indicates the incident light beam azimuth. The tilt angle is an angle in air and is up to 80 °. Two circles indicated by thick lines in FIG. 21 are ranges of the illumination light flux incident by the illumination optical system 2 having the F number of 2.5.

On the other hand, in the structure in which the field lens 5 is located between the circular polarization plate 4 and the liquid crystal modulation element 1, as shown in FIG. Is different from the incident / emission angle distribution of.
This is also the case when the circularly polarizing plate 4 having a reflective polarizing plate is used. As shown by the thick circle in FIG. 23 (range of illumination light flux incident by the illumination optical system 2 with F number 2.5), even if the incident / emission angle distribution on the circularly polarizing plate 4 is different, If the F number of the optical system 2 is 2.5, it is possible to display an image with a contrast of 1000: 1 or more even if the incident / emission angle distributions are largely different.

In the first embodiment described above, the liquid crystal modulator 1
The transparent electrode (ITO) of the liquid crystal layer and the alignment film (P
The black level reflectance when the film thickness of I) is changed is shown in FIG. 24 (ITO: 10 nm, PI: 10 n).
m), FIG. 25 (ITO: λ / 4, PI: λ / 4) and FIG. 26 (ITO: λ / 2, PI: λ / 2),
It can be seen that the reflectance at the black level is lowered and the contrast of the displayed image is improved by setting the film thickness to be sufficiently thin (10 nm) or the conditions of λ / 4 and λ / 2.

In the case where the transparent electrode (ITO) and the alignment film (PI) each have a thickness of 100 nm, FIG.
As shown in FIG. 7, the reflectance at the black level becomes high, and the contrast of the displayed image may deteriorate. Note that FIG.
The angle shown in the inside is the angle converted into the angle in the medium (refractive index 1.6). Here, the reflection of the reflective electrode is ideal, that is, the reflectances of P-polarized light and S-polarized light are both 10
This is the case of 0%.

The case where the reflective electrode is aluminum (Al) is shown below. FIG. 28 shows the relationship between the film thickness and the contrast when the refractive index of the alignment film is 1.6 and the refractive index of the ITO is 1.9. The orientation direction is 45 °. Here, the incident light azimuth angle is 0 ° (S-polarization azimuth), and the tilt angle is the medium angle (n = 1.
It is 12 ° in 6). The circular polarizer is a linear polarizer (transmission axis 0
°), 1/2 λ plate, 1/4 λ plate, each 15
The azimuth angle is 75 °. FIG. 29 shows the case where the film thickness is optimized in the case of the Al electrode (ITO film thickness 40n
m, in the case of an alignment film thickness of 160 nm) shows the incident angle dependence of the contrast. The range indicated by a circle is the illumination angle range.

FIG. 30 shows the incident angle dependence of the contrast when a reflection increasing film is added on the Al electrode. The reflection-increasing film is formed of Al, SiO ₂ , TiO ₂ , SiO ₂ , and Ti in this order.
It has a four-layer structure of O ₂ . The orientation direction is 90 °. Here, the incident light azimuth angle is 90 ° (S polarization azimuth). The circularly polarizing plate has a linear polarizing plate (transmission axis 90 °), a ½λ plate, and a ¼λ plate, and has azimuth angles of 15 ° and 75 °, respectively. IT
The O film thickness is 10 nm and the orientation film thickness is 10 nm. The range indicated by a circle is the illumination angle range.

FIGS. 31, 32 and 33 show the relationship between the Nz coefficient and the transmittance of the 1 / 2λ plate and the 1 / 4λ plate which form the circularly polarizing plate (in FIG. 31, Nz coefficient = 0. 3, Figure 3
2 is Nz coefficient = 0.5, and FIG. 33 is Nz coefficient = 1).

34 and 35 show the case where a negative retardation plate is provided for the optical compensation of the liquid crystal part and the case where it is not provided (FIG. 34 has optical compensation, and FIG. 35 does not have optical compensation). Here, the other conditions are the same as those in FIG.

[Structure in which Alignment Direction is Determined by Electric Field Around Pixel] Liquid crystal modulator 1 shown in the above-mentioned Example 1
As shown in FIG. 36, the liquid crystal layer of is a counter electrode (common electrode) 22, a liquid crystal layer 23, a pixel electrode 24, and a light shielding electrode 25.
Has a laminated structure. FIG. 37 shows a result of simulating the potential distribution at the time of modulation in the liquid crystal modulation element 1. In FIG. 37, the two pixels on the left side are in the white level state, and the two pixels on the right side are in the black level state. . Then, in FIG. 37, the liquid crystal director distribution, equipotential lines, and relative reflectance distribution are shown. The light-shielding electrode 25 has a common potential.

Thus, in this liquid crystal layer, VA
In the mode (vertical alignment mode), when the light-shielding electrode is set to the same potential as the counter electrode, the alignment means utilizing the electric field around the pixel is used, thereby eliminating the need for alignment treatment such as rubbing or oblique vapor deposition.

[0094]

As described above, in the image display device according to the present invention, the main constituent requirements are the reflective spatial light modulator and the circularly polarizing plate arranged corresponding to the spatial light modulator. The number of optical components is small,
Miniaturization is possible.

Further, compared with the optical system using the conventional polarization beam splitter, the light utilization efficiency can be improved,
Further, when the dichroic prism is used as the color separation / combination element, both the incident light and the emission light can be S-polarized, so that it is possible to prevent the reduction of the light use efficiency in the color separation / combination.

Further, in this image display device, the reduction of the contrast of the display image can be prevented by making the surface reflection light of the optical component not enter the entrance pupil of the projection lens. In addition, by optimizing the three-dimensional refractive index of the quarter-wave plate that constitutes the circularly polarizing plate,
A display image with high contrast can be obtained over a wide angle range.

Then, by adding a retardation plate for compensating the phase difference with respect to obliquely incident light to the liquid crystal layer constituting the spatial light modulation element to the spatial light modulation element, a high contrast display over a wide angle range can be obtained. It is possible to obtain an image. Also, by optimizing the thickness of the thin film that forms the liquid crystal layer that forms the spatial light modulator, it is possible to obtain a display image with high contrast over a wide angle range.

Further, in the liquid crystal layer of the spatial light modulator, in the VA mode (vertical alignment mode), when the light shielding electrode is set to the same potential as the counter electrode, the rubbing is performed by using the alignment means utilizing the electric field around the pixel. In addition, it is possible to eliminate the need for alignment treatment such as oblique vapor deposition.

That is, the present invention makes it possible to use a bright illumination optical system having a low F number, prevent the deterioration of light utilization efficiency in the color separation / combination element, and perform a bright image display. Can be provided.

[Brief description of drawings]

FIG. 1 is a side view showing a basic configuration of an image display device according to the present invention.

FIG. 2 is a side view showing a configuration in which an optical axis of a field lens is shifted with respect to an optical axis of a projection lens in the image display device.

FIG. 3 is a side view showing a configuration in which the spatial light modulator is tilted in the image display device.

FIG. 4 is an optical path of reflected light by a field lens in the image display device (when a circularly polarizing plate is between the field lens and the spatial light modulator, and the field lens is not shifted with respect to the spatial light modulator). It is a side view which shows.

FIG. 5 is an optical path of reflected light by a field lens in the above image display device (when the circularly polarizing plate is between the field lens and the spatial light modulator, and the field lens is shifted with respect to the spatial light modulator). It is a side view which shows.

FIG. 6 is a side view showing an optical path of reflected light by a field lens in the above image display device (when the circularly polarizing plate is between the field lens and the projection lens and the field lens is not tilted in the spatial light modulator). is there.

FIG. 7 is a side view showing an optical path of reflected light by a field lens in the image display device (when the circularly polarizing plate is between the field lens and the projection lens, and the field lens has the spatial light modulator tilted). is there.

FIG. 8 is an optical path of light reflected by a field lens in the image display device (when the circularly polarizing plate is between the field lens and the spatial light modulator, and the circularly polarizing plate is inclined).
It is a side view which shows.

FIG. 9 is a side view showing an optical path of reflected light by a field lens in the above image display device (when the circularly polarizing plate is between the field lens and the projection lens, and the circularly polarizing plate and the spatial light modulator are inclined). Is.

FIG. 10 is a side view showing the configuration of the first embodiment of the image display device.

FIG. 11 is a side view showing a configuration of a second embodiment of the image display device.

FIG. 12 is a plan view showing a configuration of a second embodiment of the image display device.

FIG. 13 is a side view showing a configuration of a third embodiment of the image display device.

FIG. 14 is a side view showing a configuration of a fourth embodiment of the image display device.

FIG. 15 is a side view showing a configuration of a fifth embodiment of the image display device.

FIG. 16 is a plan view showing the configuration of Example 6 of the image display device.

FIG. 17 is a sectional view showing a configuration of a circularly polarizing plate in the image display device.

FIG. 18 is a cross-sectional view showing a reflected light beam inside a circularly polarizing plate in the image display device.

FIG. 19 is a graph showing the incident angle dependence of the reflectance of P-polarized light and S-polarized light in the circularly polarizing plate in the image display device.

FIG. 20 is a cross-sectional view showing a state in which an antireflection film for preventing reflection in a circularly polarizing plate is provided in the image display device.

FIG. 21 is a graph showing an angular distribution of a light beam passing through a circular polarization plate in the above image display device (when the circular polarization plate is between the field lens and the spatial light modulation element). ) Is a graph showing the case.

FIG. 22 is a graph showing an angular distribution of a light beam passing through a circular polarization plate in the above image display device (when the circular polarization plate is between the field lens and the spatial light modulation element). ) Is a graph showing the case.

FIG. 23 is a graph showing an angular distribution of a light beam passing through a circularly polarizing plate in the image display device (when the circularly polarizing plate is between the field lens and the projection lens), showing a clockwise circularly polarized light (RCP). It is a graph which shows a case.

FIG. 24 is a graph showing an angular distribution of a light beam passing through a circularly polarizing plate in the image display device, which shows a transparent electrode (IT
It is a graph when the film thicknesses of O) and the alignment film (PI) are each 10 nm.

FIG. 25 is a graph showing an angular distribution of a light flux passing through a circularly polarizing plate in the image display device, which includes a transparent electrode (IT
9 is a graph when the film thicknesses of O) and the alignment film (PI) are each λ / 4.

FIG. 26 is a graph showing an angular distribution of a light beam passing through a circularly polarizing plate in the image display device, which includes a transparent electrode (IT
9 is a graph when the film thicknesses of O) and the alignment film (PI) are each λ / 2.

FIG. 27 is a graph showing an angular distribution of a light beam passing through a circularly polarizing plate in the image display device, including a transparent electrode (IT
It is a graph when the film thicknesses of O) and the alignment film (PI) are each 100 nm.

FIG. 28 is a graph showing the relationship between the film thickness and the contrast when the alignment film has a refractive index of 1.6 and the ITO refractive index is 1.9 in the image display device.

FIG. 29 shows a case where the film thickness is optimized in the case of an Al electrode in the above image display device (ITO film thickness 40n
3 is a graph showing the dependence of the contrast on the incident angle when m and the orientation film thickness are 160 nm).

FIG. 30 is a graph showing the incident angle dependency of contrast when a reflection increasing film is added on an Al electrode in the image display device.

FIG. 31 is a graph showing the relationship between the Nz coefficient (= 0.3) and the transmittance of the ½λ plate and the ¼λ plate that form the circularly polarizing plate in the image display device.

FIG. 32 is a graph showing the relationship between the Nz coefficient (= 0.5) and the transmittance of the ½λ plate and the ¼λ plate that form the circularly polarizing plate in the image display device.

FIG. 33 is a graph showing the relationship between the Nz coefficient (= 1) and the transmittance of the ½λ plate and the ¼λ plate that form the circularly polarizing plate in the image display device.

FIG. 34 is a graph showing the incident angle dependency of contrast when a negative retardation plate is arranged in the image display device to perform optical compensation of the liquid crystal section.

FIG. 35 is a graph showing the incident angle dependence of contrast in the above image display device when optical compensation of the liquid crystal part is not performed.

FIG. 36 is a vertical cross-sectional view showing the configuration of the liquid crystal layer of the spatial light modulator in the image display device.

FIG. 37 is a vertical cross-sectional view showing the potential distribution in the liquid crystal layer of the spatial light modulator in the image display device.

FIG. 38 is a side view showing the configuration of a conventional image display device.

[Explanation of symbols]

1 liquid crystal modulator, 2 illumination optical system, 3 projection lens,
4 circular polarization plate, 5 field lens

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03B 21/00 G03B 21/00 EF term (reference) 2H048 FA11 FA22 GA11 GA23 GA61 2H049 BA02 BA03 BA06 BA07 BA43 BB02 BC22 2H088 EA14 EA15 EA16 GA02 HA13 HA16 HA20 HA24 HA28 JA10 MA06 2H091 FA05X FA08X FA10X FA14Y FA26X FA41X FD22 FD23 GA02 HA09 LA16 MA07

Claims (12)

[Claims] 1. A spatial light modulation element having a reflective electrode, an illumination optical system including a light source for illuminating the spatial light modulation element, and a projection lens for forming an image of the spatial light modulation element. One circularly polarizing plate is provided corresponding to each element, and the circularly polarizing plate functions as a polarizer for a light flux incident on the spatial light modulation element from the illumination optical system. An image display device, which functions as an analyzer for a light flux reflected by the spatial light modulator and incident on the projection lens. 2. The surface reflection light from an optical component existing between the illumination optical system and the circularly polarizing plate is prevented from entering the entrance pupil of the projection lens. Image display device. 3. The image display device according to claim 1, wherein the circularly polarizing plate comprises a linearly polarizing plate and at least one retardation plate having a three-dimensional refractive index control. 4. The image according to claim 1, wherein the spatial light modulation element is provided with a retardation plate for compensating for a phase difference with respect to a light beam obliquely incident on the liquid crystal layer of the spatial light modulation element. Display device. 5. The film thickness of the thin film in the spatial light modulator is:
The image display device according to claim 1, wherein the thickness is such that no phase difference is generated. 6. The circular polarization plate is a reflection type polarization plate having a reflection surface, and the reflection surface is arranged so as to be inclined with respect to the reflection electrode surface of the spatial light modulation element. The image display device according to claim 1. 7. The liquid crystal layer of the spatial light modulator is in a vertical alignment mode, and when the light-shielding electrode has the same potential as the counter electrode,
The image display device according to claim 1, wherein the orientation direction is determined by the electric field around the pixel. 8. Between the illumination optical system and the spatial light modulator,
One cross type dichroic prism is provided, and three spatial light modulation elements corresponding to the three primary colors are provided corresponding to the three emission surfaces of the cross type dichroic prism. The image display apparatus according to claim 1, wherein the die dichroic prism has a function of color separation and a function of color combination. 9. The image display device according to claim 8, wherein the light beam incident on the cross type dichroic prism is S-polarized with respect to the incident surface of the cross type dichroic prism. 10. A cross-type dichroic prism is provided between the illumination optical system and the spatial light modulator, and two spaces are provided corresponding to the two exit surfaces of the cross-type dichroic prism. A light modulation element is provided, one spatial light modulation element corresponds to one of the three primary colors, and the other spatial light modulation element corresponds to the other two colors of the three primary colors. The image display apparatus according to claim 1, wherein the die dichroic prism has a function of color separation and a function of color combination. 11. The image display device according to claim 10, wherein the light beam incident on the cross-type dichroic prism is S-polarized with respect to the incident surface of the cross-type dichroic prism. 12. The projection type image display according to claim 10, wherein the transmission axis of the polarizing element is rotated by an appropriate amount with respect to the polarization axis after passing through the dichroic prism for the purpose of adjusting white balance. apparatus.