JP2003270419A - Diffractive optical element and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To optimize a polarization split characteristic even in a state where an element temperature becomes high relative to room temperature such as temperature inside a projector by using a material having the temperature dependency of comparatively high refractive index as a component like a liquid crystal material. <P>SOLUTION: In a diffracted optical element composed of a structure in which a first region and second region 6 and 7 each having different temperature dependency in the refractive index with each other are arranged alternatively, the element temperature at which diffraction efficiency for incident light in a specific polarization direction becomes minimal is set within the limits of 25 to 70 degrees C. <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 a diffractive optical element that selectively diffracts incident light having a specific polarization direction, and an image display device configured using this diffractive optical element.

[0002]

2. Description of the Related Art Conventionally, a liquid crystal material or the like is used,
A polarization-selective diffractive optical element that selectively diffracts incident light in a specific polarization direction has been proposed. Further, an image display device using such a diffractive optical element has been proposed.

Liquid crystal materials and the like have a relatively large temperature dependence of the refractive index. Therefore, the diffraction efficiency characteristic of a polarization-selective diffractive optical element using this liquid crystal material as a constituent, for example, a holographic polymer dispersed liquid crystal (hereinafter, referred to as "H-PDLC") element, depends on the element temperature. Greatly affected. This is mainly because the apparent refractive index of the liquid crystal fluctuates due to a change in microvibration intensity of liquid crystal molecules due to a temperature change.

This phenomenon will be described below with reference to a simple model. As shown in FIG. 28, the “H-PDLC” polarization-selective diffractive optical element includes a first liquid crystal molecule having a high composition ratio.
Area 101 and a second area 102 having a high composition ratio of the polymer material are sequentially arranged.

Here, in order to simplify the explanation, the first
Region 101 is made of a liquid crystal material having a positive optical anisotropy, and the optical axis directions of the liquid crystal are the first and second regions 10.
It is assumed that the orientation is perpendicular to the boundary surface of 1,102.
Further, the second region 102 is assumed to be made of an isotropic polymer. Then, at room temperature (20 degrees Celsius), it is assumed that the refractive indices for the polarization azimuths in the direction parallel to the boundary surface between the first and second regions 101 and 102 are equal in the first and second regions 101 and 102. Yes (Fig. 2
In the incident light which is parallel to the paper surface and obliquely enters the “H-PDLC” polarization selective element as shown in FIG.
Polarized light corresponds to this polarization direction).

That is, it is assumed that the ordinary refractive index of the liquid crystal material and the refractive index of the polymer material are the same at room temperature. In this case, as the temperature rises, the vibration of the liquid crystal molecules increases, and among the refractive indexes of the first region 101, the optical axis of the liquid crystal molecules (perpendicular to the boundary surface between the first and second regions 101 and 102). The polarized light along the direction (direction) is decreased, and the polarized light along the direction (direction parallel to the boundary surface between the first and second regions 101 and 102) orthogonal thereto is increased. On the other hand, in the second region 102 made of a polymer, the change in the refractive index with respect to this temperature increase is
Compared to 01, it is very small as shown in FIG.
In FIG. 29, the first and second regions 101, 1
An example of the temperature dependence of the diffraction efficiency corresponding to the refractive index of No. 02 and the difference between these refractive indexes is shown in the first and second regions 101, 1
The incident light has a polarization azimuth (P polarization in FIG. 29) and a parallel polarization azimuth (S polarization in FIG. 29) orthogonal to the 02 boundary surface.

Due to such temperature dependence, especially when this "H-PDLC" element is used as a polarization separation element utilizing the presence or absence of diffraction by the polarization direction, the polarization direction set so that the diffraction efficiency becomes low. The diffraction efficiency for
A large change rate is exhibited due to a slight change in the refractive index modulation degree.
Therefore, the polarization separation characteristic, that is, the ratio of the diffraction efficiency to the polarization azimuth set to increase the diffraction efficiency and the diffraction efficiency to the polarization azimuth set to be orthogonal to the polarization azimuth to decrease the diffraction efficiency It will deteriorate rapidly.

[0008]

By the way, it is known that the temperature inside a so-called liquid crystal projector, which is an image display device, generally rises about 15 to 30 degrees Celsius with respect to the ambient temperature.

Therefore, a device in which the diffraction efficiency is temperature dependent, such as the "H-PDLC" polarization selective element,
In particular, when a device in which the diffraction efficiency with respect to the polarization azimuth giving the lowest diffraction efficiency has temperature dependence is used in the projector, even if the characteristics at room temperature are optimized, for example, in the case of the above-mentioned polarization separation element, S
Even if the polarization diffraction efficiency is minimized, good polarization separation characteristics cannot be obtained in actual use.

Therefore, the present invention has been proposed in view of the above-mentioned circumstances, and a polarization selective refractive index using a material such as a liquid crystal material whose refractive index has a relatively large temperature dependence as a constituent element. In the modulation type diffractive optical element, the polarization splitting characteristics are optimized even in a situation where the element temperature is higher than room temperature such as in an image display apparatus (projector apparatus).

[0011]

In order to solve the above-mentioned problems, the diffractive optical element according to the present invention has a first region and a second region in which the refractive index anisotropy and the temperature dependence of the refractive index are different from each other. A polarization-selective refractive index modulation type diffractive optical element that has a structure in which regions are alternately arranged and diffracts incident light, and the diffraction efficiency for incident light of a specific polarization direction has a minimum value. Is in the range of 25 degrees Celsius or more and 70 degrees Celsius or less.

In this diffractive optical element, the diffraction efficiency with respect to the incident light of a specific polarization direction has a minimum value in the element temperature range of 25 ° C. or higher and 70 ° C. or lower. In this case, the diffraction efficiency for incident light of a specific polarization direction can be suppressed low over the entire operating temperature range, and good optical characteristics can be maintained.

The diffractive optical element according to the present invention has a structure in which first regions and second regions having different refractive index anisotropy and temperature dependence of the refractive index are alternately arranged. , A polarization selective refractive index modulation type diffractive optical element for diffracting incident light, the element temperature of which is 25 degrees Celsius or more and 7 degrees Celsius.
It is characterized in that the diffraction efficiency for incident light of a specific polarization direction is 1% or less within a range of 0 degree or less.

This diffractive optical element has a diffraction efficiency of 1% or less for incident light of a specific polarization direction when the element temperature is in the range of 25 degrees Celsius or more and 70 degrees Celsius or less. In such a case, the diffraction efficiency with respect to the incident light of a specific polarization direction can be suppressed low over the entire operating temperature range, and good optical characteristics can be maintained.

Further, in the image display device according to the present invention, the light source that emits the illumination light and the first region and the second region where the refractive index anisotropy and the temperature dependence of the refractive index are different from each other are alternately arranged. A polarization-selective refractive index modulation type diffractive optical element that has a structure arranged in diffracting incident light, and an illumination optical system that causes illumination light emitted from a light source to enter the diffractive optical element,
Illumination light diffracted by the diffractive optical element or a reflective spatial light modulator that modulates the polarization state of the illumination light transmitted through the diffractive optical element, and the illumination light that has passed through the reflective spatial light modulator and the diffractive optical element are real images Alternatively, it has an image forming optical system for forming a virtual image.

Further, according to the present invention, in this image display device, the diffractive optical element has an element temperature at which the diffraction efficiency with respect to incident light of a specific polarization direction has a minimum value within a range of 25 ° C. to 70 ° C. The imaging optical system is characterized by projecting the transmitted light or the diffracted light of the diffractive optical element on the screen or on the observer's pupil.

In this image display device, when the element temperature of the diffractive optical element is within the range of 25 degrees Celsius or more and 70 degrees Celsius or less, the diffraction efficiency of the incident light of a specific polarization direction with respect to this diffraction grating has a minimum value. The diffraction efficiency for incident light of a specific polarization direction can be suppressed low over the entire operating temperature range, and good optical characteristics can be maintained.

According to the present invention, in the above-mentioned image display device, the diffractive optical element has a diffraction efficiency of 1% with respect to the incident light of a specific polarization azimuth within an element temperature range of 25 ° C. or higher and 70 ° C. or lower. The image forming optical system is characterized in that the transmitted light of the diffractive optical element or the diffracted light is projected on the screen.

In this image display device, when the element temperature of the diffractive optical element is in the range of 25 degrees Celsius or more and 70 degrees Celsius or less, the diffraction efficiency of incident light of a specific polarization direction with respect to this diffraction grating is 1% or less. Therefore, the diffraction efficiency with respect to the incident light of a specific polarization direction can be suppressed low over the entire operating temperature range, and good optical characteristics can be maintained.

Further, in the image display device according to the present invention, the light source that emits the illumination light and the first region and the second region in which the refractive index anisotropy and the temperature dependence of the refractive index are different from each other are alternately arranged. A polarization-selective refractive index modulation type diffractive optical element having a structure arranged in diffracting incident light, and color separation means for separating illumination light into a plurality of wavelength band components different from each other,
An illumination optical system that makes illumination light separated into a plurality of wavelength band components different from each other enter the diffractive optical element, illumination light diffracted by the diffractive optical element, or illumination light transmitted through the diffractive optical element. A plurality of reflective spatial light modulators that respectively modulate polarization states of different wavelength band components, and a color combiner that combines illumination lights of different wavelength bands that are respectively modulated by the plurality of reflective spatial light modulators , And an image forming optical system for forming the illumination light that has passed through the color combining means into a real image or a virtual image.

Further, according to the present invention, in this image display device, the diffractive optical element is such that the element temperature at which the diffraction efficiency with respect to the incident light of a specific polarization direction has a minimum value is within the range of 25 degrees Celsius or more and 70 degrees Celsius or less. The imaging optical system is characterized in that the illumination light transmitted through the diffractive optical element or diffracted by the diffractive optical element and passed through the color combining means is projected on the screen or the pupil of the observer. is there.

In this image display device, when the element temperature of the diffractive optical element is within the range of 25 degrees Celsius or more and 70 degrees Celsius or less, the diffraction efficiency of the incident light of a specific polarization direction with respect to this diffraction grating has a minimum value. In addition, the diffraction efficiency with respect to the incident light of a specific polarization direction can be suppressed to be low over the entire operating temperature range, and a color image can be displayed while maintaining good optical characteristics.

According to the present invention, in the above-described image display device, the diffractive optical element has a diffraction efficiency of 1% with respect to incident light having a specific polarization direction within a range of an element temperature of 25 degrees Celsius or more and 70 degrees Celsius or less. Below, the imaging optical system is characterized in that the illumination light transmitted through the diffractive optical element or diffracted by the diffractive optical element and passed through the color combining means is projected onto the screen or the pupil of the observer. Is.

In this image display device, when the element temperature of the diffractive optical element is in the range of 25 degrees Celsius or more and 70 degrees Celsius or less, the diffraction efficiency of the incident light of a specific polarization direction with respect to this diffraction grating is 1% or less. Therefore, the diffraction efficiency with respect to the incident light of a specific polarization direction can be suppressed to be low over the entire operating temperature range, and a color image can be displayed while maintaining good optical characteristics.

[0025]

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

[Embodiment of Diffractive Optical Element] As a polarization-selective refractive index modulation type diffractive optical element according to the present invention, a liquid crystal panel made of polymer dispersed liquid crystal (hereinafter referred to as “PDLC”) is used as a material. Polarization-selective "holographic PDL" constructed by generating interference fringes by graphic means
A C ”(hereinafter referred to as“ H-PDLC ”) optical element will be described as an example. This polarization-selective “H-PDLC” diffractive optical element is manufactured by the following manufacturing process, as shown in FIG.

That is, first, "PDLC" in which a polymer material (hereinafter referred to as "prepolymer") before photopolymerization, a nematic liquid crystal, an initiator, a dye and the like are mixed is filled between the glass substrates 1 and 2. To do. At this time, the weight ratio of the nematic liquid crystal is about 40% of the whole. The layer thickness of the “PDLC”, that is, the distance (cell gap) between the glass substrates 1 and 2 is in the range of 2 μm to 15 μm, and the specifications of the polarization selective “H-PDLC” diffractive optical element to be completed. The optimum value can be selected according to.

In this polarization-selective "H-PDLC" diffractive optical element, the "prepolymer" is a polyfunctional monomer, or 2
It is composed of a functional group monomer and a monofunctional group monomer, and the action of each monomer differs depending on its material. In general,
Monofunctional monomers are used to improve the affinity with other materials and are sometimes called binder monomers. Two
Since a polyfunctional monomer having a functional group or more has good polymerizability,
It functions as a skeleton for forming polymers. The composition ratio of this "prepolymer" is 40 wt% to 60 wt% for the polyfunctional monomer and the bifunctional monomer, 5 wt% to 20 wt% for the monofunctional group monomer, and 30 wt% to 5 wt% for the liquid crystal.
0 wt%, and the photopolymerization initiator and sensitizing dye are set to several wt% or less.

Generally, such a polymerizable monomer is a photopolymerizable compound having an ethylenically unsaturated bond, and has at least one ethylenically unsaturated double bond in one molecule, Photopolymerizable and photocrosslinkable monomers, oligomers, prepolymers and mixtures thereof.

Examples of these include unsaturated carboxylic acids and salts thereof, esters of unsaturated carboxylic acids with aliphatic polyhydric alcohol compounds, and amides of unsaturated carboxylic acids with aliphatic polyhydric amine compounds. .

Many of the polymerizable monomers used in the present invention are esters of unsaturated carboxylic acids with aliphatic polyhydric alcohol compounds. In the present invention, trimethylolpropane triacrylate (TMPTA), pentaerythritol triacrylate (PETA), dipentaerythritol hydroxypentaacrylate (DPHPA), dipentaerythritol hexaacrylate (DPHA), etc. are used as the polyfunctional monomer. be able to. An addition compound of hydroxypivalic acid neopentyl glycol diacrylate is used as the bifunctional monomer. The addition compound of hydroxypivalic acid neopentyl glycol diacrylate is a simple substance of hydroxypivalic acid neopentyl glycol diacrylate.
For example, compounds modified with the following adducts.

Ε-caprolactone adduct (-(OC ₅ H
₁₀ CO) _m −) Ethylene oxide adduct (− (OC ₂ H ₄ ) _m −) Propylene oxide adduct (− (OC ₃ H ₆ ) _m −) These addition compounds are hydroxypivalic acid neopentyl glycol diacrylate simple substance. The properties such as low skin irritation, weather resistance, softness and low shrinkage are improved without losing the properties described above.

The combination of the photopolymerizable monomers must be selected in consideration of the diffractive rate of the material, the viscosity related to substance diffusion, and the curing rate.

As the liquid crystal, a cyanobiphenyl liquid crystal,
Commonly used liquid crystals such as halogen-based liquid crystals, tolan-based liquid crystals, and cyanoester-based liquid crystals can be used, but the liquid crystal material used in the present invention has a refractive index anisotropy Δn of 0.15 or more. Is desirable. This is because, in the present invention, since the phase modulation hologram is used, Δn directly affects the diffraction efficiency. Further, in the present invention, by using a cyanobiphenyl liquid crystal having a large refractive index anisotropy, it becomes possible to manufacture a hologram optical element having a good polarization selectivity.

The photopolymerization initiator is sensitive to ultraviolet rays (UV light) and functions as a photopolymerization initiator for monomers. As the photopolymerization initiator, generally, thioxanthone type, benzophenone type, diketone type, and acetophenone type can be used.

As the sensitizing dye, those of xanthene type, coumarin type, rhodamine type, carbocyanine type and the like can be used. The sensitizing dye has a function of exciting, in visible light, a polymerization initiator that is excited only by UV (ultraviolet) light. That is, the sensitizing dye has a function of absorbing visible light and transmitting the energy thereof to the photopolymerization initiator by undergoing a photopolymerization process by a visible light laser. From this function, strict consistency is required for the permissible energy level of the sensitizing dye and the permissible energy level of the photopolymerization initiator, and the combination of the photopolymerization initiator and the sensitizing dye to be used is important.

In the present invention, for a green laser, a combination of N-phenylglycine (below, [Chemical formula 1]) as a photopolymerization initiator and mouth benzengal (below [Chemical formula 2]) as a sensitizing dye is used. Used for main. For blue laser, TAZ-101 (below, [Chemical Formula 3]) as a photopolymerization initiator and BC (below, [Chemical Formula 4]) as a sensitizing dye.
Or a combination of N-phenylglycine and BC
Was used.

[0038]

[Chemical 1]

[0039]

[Chemical 2]

[0040]

[Chemical 3]

[0041]

[Chemical 4]

Here, the stress buffer layers are formed on the optical glass substrates 1 and 2, respectively. These stress buffer layers are formed between the optical glass substrates 1 and 2 and the “H-PDLC” material to realize the relaxation of the contraction stress due to the photopolymerization of the “H-PDLC” material, and also the “H-PDLC” material. While preventing the PDLC "material from peeling from the interface between the glass substrates 1 and 2,
Prevents degradation of "H-PDLC" material by heat and light.

As the stress buffer layer, one made of an organic film material such as polyimide can be used. As a manufacturing method, a polyimide film is formed by diluting polyimide with an appropriate diluting solvent, applying it by a spin coating method, and baking it at a predetermined temperature. The thickness of this stress buffer layer was 10 nm to 50 nm.

Next, in order to record interference fringes on the "PDLC" panel 3, an object beam 4 from a laser light source (not shown) is recorded.
And the reference light 5 is applied to the “PDLC” panel 3 to generate light intensity B due to interference. Then, in a bright place of the interference fringes, that is, in a place where the energy of the photon is large, the energy of the photon causes the prepolymer in "PDLC" to undergo photopolymerization to become a polymer. Therefore, the prepolymer is supplied one after another from the peripheral portion, and as a result, the polymerized prepolymer is divided into a dense region and a sparse region.
In the region where the prepolymer is sparse, the concentration of nematic liquid crystal is high. In this way, the "PDLC" panel 3
Inside, two regions, that is, a polymer region 6 which is a first region and a liquid crystal region 7 which is a second region are formed. The two regions of the polymer region 6 and the liquid crystal region 7 are sequentially arranged along the interference fringes formed by the object light 4 and the reference light 5.

In this embodiment, since the object light 4 and the reference light 5 are radiated from the surface on the same side with respect to the “PDLC” panel 3, the polarization selectivity “HP” to be manufactured is obtained.
The "DLC" diffractive optical element is a transmissive element. If the object light 4 and the reference light 5 are applied to the “PDLC” panel 3 from different surfaces, the reflection type polarization selectivity “H” can be obtained.
-PDLC "diffractive optical elements can be manufactured.

The polarization selectivity "H
In the “-PDLC” diffractive optical element, the polymer region 6 is
Isotropic with respect to refractive index. The polymer region 6 has a refractive index of 1.5, for example. On the other hand, the liquid crystal region 7 is anisotropic with respect to the refractive index. Liquid crystals are generally described using an index ellipsoid. The refractive index on the minor axis side of the refractive index ellipsoid is expressed as the ordinary ray refractive index nlo, and the refractive index on the major axis side is expressed as the extraordinary ray refractive index nle. In the liquid crystal region 7, the major axis direction of the liquid crystal molecules is the polymer region 6
It is possible to consider a case where the liquid crystal molecules are aligned so as to be perpendicular to the boundary surface with and a case where the long axis direction of the liquid crystal molecules is parallel to the boundary surface with the polymer region 6. it can. In either case, the refractive index of the liquid crystal region 7 depends on the incident polarization direction.

(A) When the major axis direction of the liquid crystal molecules is perpendicular to the boundary surface with the polymer region In this case, let us consider the light rays incident on the “H-PDLC” panel 3. Incident light can be divided into P-polarized component light and S-polarized line segment light. Here, the S-polarized component that becomes an ordinary ray will be considered. The refractive index of the liquid crystal region 7 for S-polarized light is the ordinary ray refractive index nlo, and the refractive index of the polymer region 6 is the isotropic refractive index nlp. Then, if the ordinary refractive index nlo of the liquid crystal region 7 is made substantially equal to the refractive index nlp of the polymer region 6 (for example, if the refractive index difference is less than 0.01), the refraction of the incident light with respect to the S-polarized component will be performed. The rate modulation becomes extremely small, and the S-polarized component does not cause diffraction.

On the other hand, in the liquid crystal, the difference between the ordinary ray refractive index nlo and the extraordinary ray refractive index nle is about 0.1 to 0.2. Therefore, even if the light beams have the same incident direction, the P-polarized component has a difference in refractive index between the liquid crystal region 7 and the polymer region 6, and is diffracted. That is, in this case, "H-
PDLC "functions as a phase modulation hologram. This is the operating principle of the polarization selective "H-PDLC" diffractive optical element.

(B) When the long axis direction of the liquid crystal molecules is parallel to the boundary surface with the polymer region In this case, the long axis direction of the liquid crystal molecules is perpendicular to the boundary surface with the polymer region 6. Compared with, the alignment direction of the liquid crystal is 9
0 ° different. Then, the refractive index nlo of the liquid crystal region and the refractive index nlp of the polymer region 6 with respect to the P-polarized component become substantially equal, and the diffraction efficiency approaches zero. On the other hand, for S-polarized light, a difference in refractive index occurs between the liquid crystal region 7 and the polymer region 6,
Diffraction occurs.

As a technique for orienting liquid crystal molecules, an orientation film such as polyimide is applied onto two glass substrates 1 and 2 by a method such as spin coating, followed by heating and baking,
A method of performing rubbing treatment in a certain direction by using a roller or the like and orienting is generally used. There is also an alignment method in which transparent electrodes are formed on the glass substrates 1 and 2 and an electric field is applied to the “H-PDLC” cell. In addition, there is a method of aligning the liquid crystal by applying a very large external electric field or magnetic field from the outside of the “H-PDLC” cell. In the present invention, by selecting the polymer material and the liquid crystal and optimizing the compounding ratio, the liquid crystal molecules can be aligned in the direction perpendicular to the interference fringes without performing special alignment treatment.

Next, the temperature dependence of the refractive index of the polymer region 6 and the liquid crystal region 7 in this polarization selective "H-PDLC" diffractive optical element will be described.

For the sake of simplicity, it is assumed here that the polymer region 6 has a refractive index isotropic property almost completely. The polymer region 6 and the liquid crystal for the polarization component (S-polarized light in FIG. 28) parallel to the interference fringes formed by the polymer region 6 and the liquid crystal region 7 and the polarization component (P-polarized light in FIG. 28) perpendicular to the interference fringe. The temperature dependence of the refractive index of the region 7 is
As shown in FIG. 2, as compared with the refractive index of the liquid crystal region 7, the polymer region 6 has a characteristic that the refractive index changes very little due to the temperature rise.

This is because in the polymer region 6, there are few liquid crystal molecules present and they are arranged in a substantially disordered manner, and the temperature dependence of the refractive index is mainly due to the temperature dependence of the refractive index of the polymer material. Because there is.

On the other hand, the refractive index of the liquid crystal region 7 changes relatively greatly as the temperature rises, decreases with the temperature rise for P-polarized light, and increases with the temperature rise for S-polarized light. This is because, as described above, many liquid crystal molecules existing in the liquid crystal region 7 are aligned with the optical axis direction perpendicular to the walls of the interference fringes (the boundary surface between the polymer region 6 and the liquid crystal region 7), As shown in FIG. 3, as the temperature rises, the order parameter (order) of the liquid crystal molecules decreases, so that the apparent refractive index seen from the P-polarized light decreases,
This is because the apparent refractive index seen from the S-polarized light increases. In addition, for example, a cyanobiphenyl liquid crystal (4-cyano-4′-) used as a liquid crystal material forming the liquid crystal region 7 is used.
In the case of an isotropic liquid such as pentyl biphenyl), the temperature dependence of the refractive index shows a value slightly higher than nlo.

Then, the polarization selectivity "HP" according to the present invention is obtained.
The DLC "diffractive optical element is characterized in that the diffraction efficiency for S-polarized light takes a minimum value when the element temperature is within the operating temperature range of the element. The case where the diffraction efficiency has a minimum value corresponds to the case where the polymer region 6 and the liquid crystal region 7 have the same refractive index.

In this embodiment, the element operating temperature is 25 ° C. to 70 ° C. Therefore, for example, as shown in the upper right graph in FIG. 2, within the operating temperature range of the element, more preferably, the element operating temperature is 25.
It suffices that the polymer region 6 and the liquid crystal region 7 have the same refractive index with respect to the S-polarized light in the vicinity of the median value of 45 ° C between ° C and 70 ° C. At this time, the S-polarized diffraction efficiency becomes 0, as shown in the lower right graph in FIG.

Alternatively, as shown in FIG. 4, the polymer region 6
Even if the refractive indices of the liquid crystal region 7 and the liquid crystal region 7 are not completely equal to each other, the difference between the refractive indices of the polymer region 6 and the liquid crystal region 7 with respect to S-polarized light is within the operating temperature range of the device, and more preferably,
As shown in the upper graph in FIG. 2, the minimum value may be taken in the vicinity of the median value of 45 ° C., which is the device operating temperature of 25 ° C. to 70 ° C. At this time, the S-polarized light diffraction efficiency has a minimum value as shown in the lower graph in FIG. The minimum value of this S-polarized light diffraction efficiency is preferably 1% or less.

Then, this polarization selectivity "H-PDLC"
In the diffractive optical element, it is desirable that the diffraction efficiency with respect to the S-polarized light is always 1% or less within the operating temperature range of the element, which is 25 ° C to 70 ° C.

As for the element use temperature, when an image display device to be described later is constructed by using this diffractive optical element, the actual measurement result at room temperature of 23 ° C. shows that it is near the liquid crystal panel which is the spatial light modulator. At room temperature, increased by 17.3 ° C from room temperature to 40.3 ° C, and in the vicinity of the lamp as a light source, increased from room temperature by 27.4 ° C to 50.3 ° C.
It was 0.4 ° C.

As a result of actually measuring the temperature dependence of the refractive index change of the liquid crystal region 7 with respect to the S-polarized light, as shown in FIG. 5, when the room temperature is 20 ° C., the element temperature rises by 60 ° C. from the room temperature. At 80 °, the refractive index is 0.00
3 change, element temperature increased by 80 ° C from room temperature 100
At °, the refractive index showed a change of 0.008. When this change is compared with the change in the refractive index of the polymer region 6 with respect to S-polarized light, as shown in FIG.
It can be seen that at 80 ° increased by ° C, the amount of change in the refractive index reaches 8 to 9 times.

The polarization selectivity "H-
In order to realize a “PDLC” diffractive optical element, for example,
Adjusting the refractive index after polymerization of the polymer material used, or the temperature dependence of the refractive index, adjusting the degree of phase separation between liquid crystal and polymer, adjusting the ordinary ray refractive index and extraordinary ray refractive index of liquid crystal molecules Alternatively, there is a method of adjusting the interaction force between the liquid crystal droplets and the polymer.

In the above-described embodiment, the liquid crystal region 7
The liquid crystal molecule having positive optical anisotropy present in 1 is mainly described in the case where the liquid crystal molecule is aligned with the optical axis perpendicular to the interference fringes. However, in the present invention, the liquid crystal molecule interferes with the optical axis. It is applicable also when aligned parallel to the stripes or when the liquid crystal molecules have negative optical anisotropy.

Further, according to the present invention, two regions having different refractive index anisotropy and temperature dependence of the refractive index are alternately arranged even if the liquid crystal material and the polymer material are not necessarily contained. Any refractive index modulation type diffractive optical element having a structure can be applied.

[Example 1 of Diffractive Optical Element] Specific examples of the diffractive optical element according to the present invention will be described below.
The mixture of the “H-PDLC” materials was mixed in a dark room so that the polymerization reaction would not start in visible light.

About 40 wt% of cyanobiphenyl liquid crystal "SY1018XX" (trade name) manufactured by Chisso Co., Ltd., a photopolymerizable trifunctional monomer, "Aronix M-309" manufactured by Tsukasa Co., Ltd. ( About 22 wt% (trade name) (chemical name: trimethylolpropane triacrylate) (the following [Chemical formula 5]), as a photopolymerizable bifunctional monomer, "KAYARAD HX-220" manufactured by Nippon Kayaku Co., Ltd. (Chemical name: ε-caprolactone-modified hydroxypivalic acid neopentyl glycol diacrylate) (the following [Chemical formula 6]) about 22 wt%, as a photopolymerizable monofunctional group monomer manufactured by Nippon Kayaku Co., Ltd., "KAYARAD R" -128
H ”(trade name) (chemical name: 2-hydroxy-3-phenoxypropyl acrylate) (the following [Chemical formula 7]) about 16
About 0.5 wt% of N-phenylglycine (Chemical formula 1) as a photopolymerization initiator and about 0.5 wt% of Rose Bengal (Chemical formula 2) as a sensitizing dye are weighed,
Mixing was performed.

[0066]

[Chemical 5]

[0067]

[Chemical 6]

[0068]

[Chemical 7]

The mixing was carried out by using a stirrer and ultrasonic waves. This mixture was filled between glass substrates facing each other with a gap of about 5 μm. Spacer beads made of glass or plastic were used to maintain the gap. A polyimide film having a thickness of 30 nm was formed as a stress buffer layer on the glass substrate.

Then, using a SHG laser having a wavelength of 532 nm, two-beam holographic exposure was performed from the same surface direction of the glass substrate to form interference fringes. Holographic exposure is used to prevent fluctuations due to vibration.
The laser intensity was increased and the exposure was performed in the shortest possible time.

The laser-exposed sample was irradiated with ultraviolet rays using a high pressure mercury lamp as a light source to cure the unpolymerized portion of the polymer. Through the above steps, “H-PDLC” in which the refractive index changes periodically inside the cell was obtained.

The photopolymerizable bifunctional group monomer is "HX-22".
0 ”instead of“ KAYARAD ”manufactured by Nippon Kayaku Co., Ltd.
MANDA "(trade name) (chemical name: neopentyl glycol diacrylate hydroxypivalate) (Chemical formula 8 below) may be used.

[0073]

[Chemical 8]

Next, the diffraction efficiency was measured using a He-Ne laser having a wavelength of 633 nm. The diffraction efficiency was measured at the angle at which the intensity of the diffracted light was the highest, and the value of the diffraction efficiency was calculated by the following formula. [Diffraction efficiency] = ([Intensity of diffracted light Id] / [Intensity of incident light]
Ii]) × 100 (%) As a result of measurement, the diffraction efficiency of P-polarized light was about 80%, and the diffraction efficiency of S-polarized light was 0.2%. The degree of polarization separation is 400 or more because it is the ratio of the diffraction efficiency of P-polarized light to the diffraction efficiency of S-polarized light.

Further, a glass substrate coated with polyimide and rubbed was filled with the mixed material, and then "H-
By making “PDLC”, it was possible to control the alignment of the liquid crystal and increase the degree of polarization separation.

[Example 2] Next, about 40 wt% of "Cyanobiphenyl liquid crystal SY1018XX" (trade name) manufactured by Chisso Corp. was used as a photopolymerizable trifunctional monomer, and Toagosei Co., Ltd. Aronix "M- 309 "(trade name) (chemical name: trimethylolpropane triacrylate) is about 25 wt% as a photopolymerizable bifunctional monomer," KAYARAD HX-220 "(trade name) manufactured by Nippon Kayaku Co., Ltd. Name: ε-caprolactone modified hydroxypivalic acid neopentyl glycol diacrylate) about 2
5 wt%, about 10 wt% of “N-vinyl-pyrrolidinone” (Chemical Formula 9 below) as a photopolymerizable monofunctional monomer, and about 0.5 wt of N-phenylglycine as a photopolymerization initiator.
%, Rose bengal as a sensitizing dye was weighed in an amount of about 0.5 wt%, and mixed.

[0077]

[Chemical 9]

The mixing of these was carried out using a stirrer and ultrasonic waves. This mixture was filled between glass substrates facing each other with a gap of about 5 μm. Spacer beads made of glass or plastic were used to maintain the gap. A polyimide film having a thickness of 30 nm was formed as a stress buffer layer on the glass substrate.

Then, using a SHG laser having a wavelength of 532 nm, two-beam holographic exposure was performed from the same surface direction of the glass substrate to form interference fringes. Holographic exposure is used to prevent fluctuations due to vibration.
The laser intensity was increased and the exposure was performed in the shortest possible time.

The laser-exposed sample was irradiated with ultraviolet rays from a high pressure mercury lamp as a light source to cure the unpolymerized portion of the polymer. Through the above steps, “H-PDLC” in which the refractive index changes periodically inside the cell was obtained.

The photopolymerizable bifunctional monomer is "HX-22".
0 ”instead of“ KAYARAD ”manufactured by Nippon Kayaku Co., Ltd.
MANDA ”(trade name) (chemical name: neopentyl glycol diacrylate hydroxypivalate) (the above [Chemical formula 8]) may be used.

The combination of the photopolymerization initiator and the sensitizing dye is not limited to the combination of rose bengal and N-phenylglycine, and a combination of materials suitable for the wavelength for exposure can be used. For example, wavelength 457nm
In the case of using SHG laser light for exposure, as the photopolymerization initiator, N-phenylglycine or "TAZ-101" (trade name) manufactured by Midori Kagaku Co., Ltd. (chemical name: 2,4) , 6 tris (trichloromethyl) -S-triazine (the above [Chemical Formula 3]), and as the sensitizing dye, "BC" (trade name) manufactured by Midori Kagaku Co., Ltd. (chemical name: 3,3'-
A combination of carbonyl-bis (7-diethylaminocoumarin (Formula 4 above)) was used.

Next, the diffraction efficiency was measured using a He-Ne laser having a wavelength of 633 nm. The diffraction efficiency was measured at the angle at which the intensity of the diffracted light was the highest, and the value of the diffraction efficiency was calculated by the following formula. [Diffraction efficiency] = ([Intensity of diffracted light Id] / [Intensity of incident light]
Ii]) × 100 (%) As a result of measurement, the diffraction efficiency of P-polarized light was about 70%, and the diffraction efficiency of S-polarized light was 0.3%. The degree of polarization separation is a ratio of the diffraction efficiency of P-polarized light to the diffraction efficiency of S-polarized light, and it can be seen that it is 200 or more.

Furthermore, the mixed material is filled in a glass substrate which is coated with polyimide and rubbed, and then "H-
By making “PDLC”, it was possible to control the alignment of the liquid crystal and increase the degree of polarization separation.

[Embodiment of Image Display Device (First to Third Embodiments)] Hereinafter, the polarization selectivity “H-PD” will be described.
A first embodiment of an image display device including an "LC" diffractive optical element and a reflective image display element will be described with reference to FIG. In this image display device,
On the “H-PDLC” panel 3 described above, a reflective FLC liquid crystal panel 10 serving as a reflective spatial light modulator is provided with an interface 11.
In the optical contact.

In this image display device, the spatial light modulator is a reflective spatial light modulator that modulates the light reflected by the spatial light modulator, and is a polarization-modulated space that modulates the polarization state of the incident light. A light modulator, for example,
The polarization direction of the incident linearly polarized light is rotated and reflected.

The reflective FLC liquid crystal panel 10 is constructed by enclosing a FLC layer (liquid crystal layer) 13 between a pair of glass substrates 12 and 15. In this embodiment, "H-
PDLC ”panel 3 has an incident angle of 0 °, as shown in FIG.
The object light 4 and the reference light 5 having the incident angle θ in-air. The tilt angle θint of the interference fringes at this time is obtained.

Assuming now that the refractive index of the glass substrate 1 is ngla and the average refractive index of "PDLC" is also ngla for simplification, the following formula is established.

Ngla · sin (θin-med) = sin (θin-air) (∵θin-med: incident angle in medium) In this equation, ngla = 1.5 and θin-air = 60 ° θin-med = 35.3 °. From this, the inclination angle θint of the interference fringe becomes θint = θin-med / 2 = 17.7 ° from the following formula.

Next, the operation principle of this image display device will be described. First, the reproduction light 5 including both the P-polarized light component and the S-polarized light component is incident from the glass substrate 1 of the “H-PDLC” panel 3 at the incident angle θ in-air. The incident light refracted by the glass substrate 1 subsequently enters the hologram layer 9 at an incident angle θin-med.

At this time, in this hologram layer 9, the P-polarized component is diffracted and enters as incident light 51 substantially perpendicularly to the reflective FLC liquid crystal panel 10.
Then, the P-polarized component is reflected by the aluminum reflecting surface 14, is modulated by reciprocating through the FLC layer 13, and is re-incident on the hologram layer 9. At this time, the P-polarized component is diffracted again in the hologram layer 9 and returns to the opposite direction of the reproduction light 5 as the emitted light 53, and the S-polarized component is not diffracted in the hologram layer 9 and is emitted as the emitted light 52. HP
Eject vertically from DLC "panel 3.

On the other hand, the S-polarized component of the reproduction light 5 is "HP
The light enters the reflective FLC liquid crystal panel 10 at the incident angle of θin-med without being diffracted by the hologram layer 9 of the “DLC” panel 3. At this time, the S-polarized component is modulated in polarization state by passing through the FLC layer 13 of the reflective FLC liquid crystal panel 10, but the reflected light 54 reflected by the aluminum reflecting surface 14 is a hologram in which the hologram layer 9 is thick. Therefore, the diffraction condition is not met, and the S-polarized component as well as the P-polarized component is hardly diffracted.
DLC ”panel 3 is transmitted. Even if the FLC layer 13
Even if a part of the P-polarized light component generated by the modulation in 1 is diffracted by the hologram layer 9, the emission direction of the reflected light 54 is set sufficiently different from the emission direction of the emission light 52, or The reflected light 54 and the emitted light 52 can be separated by providing a polarizing plate in the optical path of the emitted light 52 that selectively transmits the polarized component of the emitted light 52.

That is, in this image display device,
The polarization-selective “H-PDLC” diffractive optical element is 30 ° or more 90 ° with respect to the normal line of the illumination light receiving surface by the illumination optical system.
Illumination light enters at an incident angle of less than °, diffracts the P-polarized component or the S-polarized component of the illumination light, and emits it toward the reflective spatial light modulator, and is phase-modulated by the reflective spatial light modulator. Of the illuminating light that is re-incident, the diffraction efficiency with respect to the polarization component that is the polarization direction orthogonal to the polarization direction of the polarization component that is diffracted at the first incidence is 10%.
By being below, 70% or more of this polarized component is transmitted.

Here, the "thick hologram" will be described. The definition of "thick hologram" is that the following Q value is 1
It should be 0 or more (reference book: Junpei Tsujiuchi, "Holography" (Shikabo)). The Q value is defined by the following formula.

Q = 2πλt / (nΛ ² ) (∵λ: reproduction wavelength) (∵t: thickness of hologram layer) (∵n: average refractive index of hologram layer) (∵Λ: pitch of interference fringes) The pitch Λ of the interference fringes is determined as follows.

Λ = λc / | 2sin {(θs−θr) / 2} | (∵λc: manufacturing wavelength) (∵θs: incident angle of object light) (∵θr: incident angle of reference light) If λc = 0.55 μm, θs = 60 °, θr = 0
If λ, λ = 0.55 μm, t = 5 μm, and n = 1.5, the pitch of interference fringes becomes Λ = 0.55 μm and Q = 38.1, which applies to the definition of a thick hologram.

The thick hologram has a high diffraction efficiency, but the diffraction efficiency sharply decreases when the reproduction light conditions are deviated from the configuration such as the wavelength used during manufacturing, the object light and the incident angle of the reference light. Hold. That is, when the incident angle of the reproducing light is largely deviated from the incident angle giving the peak of the diffraction efficiency at a certain reproducing wavelength, the diffraction effect is not exhibited. Therefore, as described above, the reflected light 54 is less likely to be diffracted by the hologram layer 9, even if it is the P-polarized component.

The polarization selectivity "H-PDL" in the present invention
The “C” diffractive optical element has a bend angle | θs−θr in order to reduce the pitch Λ of the interference fringes for the purpose of high diffraction efficiency.
The feature is that | is set to 30 ° or more. However, if the bend angle is too large (for example, 80 ° or more), the wavelength band in which the diffraction effect is generated and the incident angle range are reduced, and the light utilization efficiency is reduced.

In the actual image display, since the FLC layer 13 of the reflective FLC liquid crystal panel 10 is controlled and the polarization state of the reflected light is modulated for each pixel, the image display is mainly performed by the emitted light 52 having the S polarization component. Is possible.

Here, the reproduction light incident angle θin-air on the “H-PDLC” panel 3 and the incident angle θin-m on the hologram layer 9 are.
Think about ed. The relationship between the two is, as described above, ngla · sin (θin-med) = sin (θin-air). Here, looking at the change rates of both, for example, when ngla = 1.5, θin-air is from 55 ° to 6 °
When changing 10 ° up to 5 °, θin-med is 33.1 °
To only 37.2 ° and 4.1 °. θin-air
Θin-m when changes from 65 ° to 75 ° by 10 °
ed changes from 37.2 ° to 40.1 ° and 2.9 °. This is nothing but moving to a place where the rate of change of the sin function is large by multiplying it by a certain magnification (in this case, the reciprocal of ngla). This means that it is possible to reduce the deterioration of the uniformity and the decrease of the diffraction efficiency due to the dependence of the diffraction efficiency of the “H-PDLC” panel 3 on the incident angle of the reproduction light.

The rate of change of θin-med with respect to θin-air can be made smaller as ngla is larger. For example, ngla
= 1.73, when θin-air changes from 55 ° to 65 °, θin-med remains a change of 28.3 ° to 31.6 ° and 3.3 °. However, "H-PDLC"
When the reproduction light incident angle θin-air on the panel 3 becomes too large (for example, 75 ° or more), not only the S-polarized light but also the P-polarized light has a large surface reflectance. It becomes difficult to keep it small.

Therefore, in the case where the reproduction light incident angle θin-air on the “H-PDLC” panel 3 exceeds 75 °,
As shown in FIG. 8 (second embodiment), it is effective to use the cubbling prism 19. However, in this case, the reproduction light incident angle θin-air on the “H-PDLC” panel 3 and the reproduction light incident angle θin-med on the hologram layer 9 are used.
Are equal to each other, and when the hologram layer 9 itself does not have a relatively wide allowable incident angle range, the light use efficiency is reduced.

In this reflective image display element, assuming that the coupling prism 19 is used, the bend angle becomes 30 ° or more when the diffracted light is made to enter the reflective spatial light modulator substantially vertically. The minimum incident angle is defined as the incident angle to the polarization selective “H-PDLC” diffractive optical element, that is, 30 °.

In order to maintain a high diffraction efficiency for the reproduction light in the high band, as shown in FIG. 9 (third embodiment), a plurality of polarization selective “H-PDLC” diffractive optical elements 3 are used.
R, 3G, and 3B are laminated to divide the wavelength band of the illumination light for illuminating the reflective spatial light modulator 10 into a plurality of wavelength bands, and each band is diffracted by one polarization selective “H-PDLC” diffractive optical element. To

In the case of this embodiment, a three-layer structure is used, but more layers or a two-layer structure may be used. Further, in order to maintain a high diffraction efficiency for reproduction light having a large incident angle range, a plurality of polarization selective “H-PDLC” diffractive optical elements having different acceptance ranges of the incident angle are stacked, and the respective incident angles are different. The range may be mainly diffracted by one polarization selective hologram optical element.

[Embodiment of Projection-Type Image Display Device (Fourth Embodiment)] The polarization selectivity “H
An embodiment of a projection-type image display device including a -PDLC "diffractive optical element and a reflective spatial light modulator will be described.

As a fourth embodiment of the image display device according to the present invention, as shown in FIG. 10, a color projection type image display device is constituted by using a reflection type FLC panel as a reflection type spatial light modulator. be able to. In this image display device, the illumination light emitted from the illumination light source 20 is incident on the illumination optical system 21 having the functions of correcting the cross-sectional shape of the light flux, making the intensity uniform, and controlling the divergence angle. Illumination optical system 21
Has a polarization conversion means (not shown), and in the case of this embodiment, S-polarized illumination light is used so that the incident light on the polarization-selective “H-PDLC” diffractive optical element 3 becomes P-polarized light. By rotating the polarization direction of the component by 90 °, it is converted into P-polarized light, and the light utilization efficiency is improved. The illumination light that has passed through the illumination optical system 21 passes through the color wheel 22 and is used for correction polarization selective “H-PDLC” diffractive optical element 2.
Incident on 3. The color wheel 22 time-divides white light radiated from the illumination light source 20 into spectral components of red light, green light, and blue light. This allows the so-called single-plate reflective FLC panel 10 to be used. The "field sequential color method" enables color display.

The illumination light that has entered the correction polarization-selective “H-PDLC” diffractive optical element 23 is diffracted only in the P-polarized component, and exits at an exit angle of about 60 °. The S-polarized component is not diffracted, and the polarization selectivity for correction “HP
DLC ”diffractive optical element 23 goes straight through. The illumination light mainly composed of the P-polarized component diffracted by the correction polarization-selective “H-PDLC” diffractive optical element 23 subsequently enters the polarization-selective “H-PDLC” diffractive optical element 3.

Here, the polarization selectivity for correction "H-PDL"
The “C” diffractive optical element 23 and the polarization-selective “H-PDLC” diffractive optical element 3 have the same structure and are arranged in parallel with each other. Therefore, the incident angle of the illumination light on the polarization-selective “H-PDLC” diffractive optical element 3 depends on the correction polarization-selective “H-PDLC” diffractive optical element 2.
Equal to the exit angle of the illumination light from 3.

This brings about two main advantages as follows. First, it is possible to cancel the variation in the diffraction angle due to the wavelength, and secondly, to correct the difference in the incident angle dependence of the diffraction efficiency depending on the wavelength.

The first advantage will be described. The incident angle θc and the diffraction angle θi in the interference fringes of the hologram are related by the following equation.

(Sin {θs} -sin {θr}) / λ = (sin
{Θi} -sin {θc}) / λc (∵θs: incident angle of object light during hologram production) (∵θr: incident angle of reference light during hologram production) (∵λ: hologram production wavelength) (∵λc: reproduction Wavelength) That is, the diffraction angle of the hologram having a certain specific interference fringe depends on the wavelength of the incident light beam. And
The smaller the interference fringe pitch Λ, the greater the rate of change. The interference fringe pitch Λ has the relationship shown in the following formula.

Λ = λ / | sin {θs} -sin {θr} | For example, θs = 0 °, θr = 60 °, λ = 550 nm,
When θc = 60 °, λc is 450 nm to 650 n
When changed to m, the diffraction angle θi changes from 9 ° to −9 °. This means that the angle of incidence of illumination light on the reflective spatial light modulator differs depending on the wavelength.

In the case of a real image forming system such as a projection type image display device, one of the main problems caused by such a change in the illumination light incident angle is a decrease in light utilization efficiency. That is, the illumination light to the reflective spatial light modulator is diffused, and the light collection rate of the projection optical system decreases.
Further, in the case of the virtual image display device, this leads to a problem that the tint of the display image changes as the observer's pupil moves. These problems are suppressed by reducing the diffraction allowable spectrum width of the polarization-selective “H-PDLC” diffractive optical element 3 and preparing a plurality of polarization-selective “H-PDLC” diffractive optical elements 3 for each wavelength band. It is possible to

However, it is not practical to divide the illumination light into wavelength bands infinitely small, and it is therefore difficult to completely eliminate the wavelength dependence of the diffraction angle. Therefore,
Polarization-selective "H-PDLC" with two equivalent performances
The diffractive optical elements 3 and 23 are used to correct this.

The S-polarized illumination light that is diffracted by the polarization-selective “H-PDLC” diffractive optical element 3 and enters the reflective spatial light modulator 10 is modulated in phase by the reflective spatial light modulator 10. Polarization selectivity "H-PDLC" again
The light enters the projection optical system 25 through the polarizing plate 24 that transmits the diffractive optical element 3 and selectively transmits only the S-polarized light.
By this projection optical system 25, the optical image displayed on the reflective FLC panel 10 is enlarged and projected on the screen 26.

On the other hand, the polarization selectivity "H-
The remaining outward illumination light that is not diffracted by the “PDLC” diffractive optical element 3 is transmitted through the polarization selective “H-PDLC” diffractive optical element 3 as it is, and is reflected by the aluminum reflection surface 14 of the reflective spatial light modulator 10 to be positive. It is reflected and emitted again in the left direction in FIG. This illuminating light becomes stray light and may cause deterioration of the contrast of the display image. Therefore, the energy is absorbed by the light absorbing means 27.

The correction of the incident angle by the correction polarization-selective “H-PDLC” diffractive optical element 23 will be described with reference to FIG. From the above equation, the correction polarization selectivity “H−
Emission angle θ of diffracted light in the “PDLC” diffractive optical element 23
i-1 is represented by the following formula.

Sin (θi-1) = λc / λ (sin {θs} -s
in {θr}) + sin (θc) Here, if θs = θc = 0 °, sin (θi-1) = − λc / λsin (θr) ... Formula (1) That is, the reproduction wavelength λc is long. The greater θi-1 becomes. Now, when the reproduction wavelengths L (for example, red), M (for example, green), and S (for example, blue) satisfy the relationship of L>M> S, the respective diffraction emission angles θi-1L, θi-1M, and θi-1S.
Satisfies the following relationship.

[Theta] i-1L> [theta] i-1M> [theta] i-1S Next, the polarization selectivity "H-PDLC" for correction is set in parallel with the polarization selectivity "H-PDL".
When applied to the “C” diffractive optical element 3, the incident angle is θi−1, and therefore the exit angle θi-2 satisfies the following formula.

(Sin {θs} -sin {θr}) / λ = (sin {θi-2} -sin {θi-1}) / λc Equation (2) These equations (1) and ( From 2), θi-2 = θs = 0 °
Therefore, the incident angle of the illumination light on the reflective spatial light modulator 10 can be always 0 ° regardless of the reproduction wavelength.

Next, the second merit described above will be described. The manufacturing wavelength 532 is shown in FIGS. 12, 13 and 13.
nm, object light incident angle 0 °, reference light incident angle 60 °, average refractive index 1.52, hologram thickness 5 μm, polarization selectivity “H
-PDLC shows the incident angle dependence of the diffraction efficiency of a diffractive optical element. 12 shows a reproduction wavelength of 450 nm, and FIG. 13 shows
The reproduction wavelength is 550 nm, and the reproduction wavelength is 650 n in FIG.
This is the case of m.

From the relationship between the incident angle dependence of the diffraction efficiency and the reproduction wavelength, the incident angle giving the peak of the diffraction efficiency differs depending on the wavelength. On the long wavelength side, the larger the incident angle, the higher the diffraction efficiency and the shorter wavelength. On the side, it can be seen that the smaller the incident angle, the higher the diffraction efficiency. Then, by using the correction polarization-selective “H-PDLC” diffractive optical element 23, the polarization-selective hologram 3 of the illumination light on the long wavelength side is obtained.
The incident angle on F is large, and the short wavelength side is small. Therefore, by using the correction polarization-selective “H-PDLC” diffractive optical element 23, high diffraction efficiency can be obtained in a wide wavelength band and high light utilization efficiency can be maintained.

As described above, the polarization selectivity "H-PDL" is
C "diffractive optical element 3 and correction polarization selectivity" H-PDL "
By combining with the “C” diffractive optical element 23, it becomes possible to illuminate the reflective spatial light modulation element 10 at the same incident angle with high efficiency even with illumination light in a wide wavelength band.

However, in this embodiment, the incident angle of the principal ray on the reflective spatial light modulator 10 is set to θob1 instead of 0 °. This is because, as described above, the diffraction efficiency of the thick transmission hologram is set to a large bend angle because a high refractive index cannot be secured unless the vent angle is large to some extent. Therefore, this θob
1 is set in a direction in which the bent angle of the polarization-selective hologram element 3 is increased in the plane of incidence. At this time, this θob
If 1 is set too large, problems such as deterioration of the contrast of the reflective spatial light modulator 10, enlargement of the projection optical system 25, and increase in aberration of the display image occur.
It is desirable to be within °.

However, by using the projection optical system 25 as a decentered optical system and effectively utilizing the obliquely emitted light from the reflective spatial light modulator 10, the center of the display image is projected onto the projection optical system 25.
It is possible to make the effective system of the projection optical system 25 small while shifting it from the optical axis of.

On the contrary, the polarization selectivity "H-PDL"
When the refractive index modulation degree of the “C” diffractive optical element is sufficiently large (for example, 0.05 or more), sufficient diffraction efficiency can be ensured even at a bend angle of about 50 °, so that the allowable wavelength band and the allowable incident angle are widened. , Θob1 is more advantageous in the direction of decreasing the bend angle. Also in this case, the absolute value of θob1 cannot be increased so much because of the reason described above, and it is preferably about 10 °.

When the bend angle is large (θob1 = 10 °),
FIGS. 15 and 16 show the dependence of the diffraction efficiency on the reproduction wavelength and the incident angle in the case where the bend angle is small (θob1 = −10 °).
Shown in. From these FIGS. 15 and 16, a small bend angle (θ
It can be seen that when obl = -10 °), the deterioration of the diffraction efficiency due to the reproduction wavelength and the incident angle is reduced.

[Fifth Embodiment of Image Display Device] As a fifth embodiment of the image display device according to the present invention, a color projection type image using a reflection type TN liquid crystal panel as a reflection type spatial light modulator. The display device will be described with reference to FIG.

In this image display device, the illumination light source 2
The illumination light emitted from the illumination optical system 2 has the functions of correcting the cross-sectional shape of the light flux, making the intensity uniform, and controlling the divergence angle.
Incident on 1. This illumination optical system 21 has a polarization conversion means (not shown), and in the case of this embodiment, the incident light to the polarization selective “H-PDLC” diffractive optical element 3 is P-polarized light, The polarization direction of the illumination light of the S polarization component is set to 9
By rotating it by 0 °, it is converted into P-polarized light and the light utilization efficiency is improved.

The illumination light that has passed through the illumination optical system 21 passes through the polarizing plate 28 that selectively transmits the P-polarized light, and the blue, green, and red dichroic mirrors 29, 30,
It is incident on 31. These dichroic mirrors 29, 3
Nos. 0 and 31 are arranged such that the angles θb, θg, and θr formed by their reflecting surfaces and the traveling direction of the illumination light have a relationship of θb <θg <θr. As a result, the dichroic mirrors 29, 30 and 31 have the correction polarization selectivity “H-PDLC” shown in the above-described fourth embodiment.
It plays the same role as the diffractive optical element 23.

That is, the incident angle of the red light on the polarization selective "H-PDLC" diffractive optical element 3 is the largest, and
The order is green light and blue light. Polarization selectivity "H-PDL
Each of the color lights incident on the “C” diffractive optical element 3 has three hologram layers 9r, 9g, and 9b provided for the respective color lights.
Thus, the light is focused on the aluminum pixel electrodes 14r, 14g, and 14b of the corresponding color of the reflective spatial light modulator. The illumination light that travels back and forth through the TN liquid crystal layer 13 is phase-modulated, and its S-polarized component is transmitted without being diffracted by the polarization-selective “H-PDLC” diffractive optical element 3, and the S-polarized component is selectively transmitted. The light enters the projection optical system 25 via the polarizing plate 24.
The image light flux incident on the projection optical system 25 is reflected by the screen 26.
Projected on.

[Sixth Embodiment of Image Display Device] As a sixth embodiment of the image display device according to the present invention, FIG.
As shown in FIG. 8, a color projection type image display device using three reflection type antiferroelectric liquid crystal panels 10r, 10g and 10b as reflection type spatial light modulators will be described.

In this image display device, the illumination light source 2
The illumination light emitted from the illumination optical system 2 has the functions of correcting the cross-sectional shape of the light flux, making the intensity uniform, and controlling the divergence angle.
Incident on 1. This illumination optical system 21 has a polarization conversion means (not shown), and in the case of this embodiment, the incident light to the polarization selective “H-PDLC” diffractive optical element 3 is P-polarized light, Set the polarization direction of the S-polarized component of the illumination light to 9
By rotating it by 0 °, it is converted into P-polarized light and the light utilization efficiency is improved.

The illumination light that has passed through the illumination optical system 21 enters the correction polarization-selective "H-PDLC" diffractive optical element 23, where only the P-polarized component is diffracted and the exit angle is about 60 °.
Is injected with. The S-polarized light travels straight through the correction polarization-selective “H-PDLC” diffractive optical element 23 without being diffracted.

The illumination light which is the P-polarized component diffracted by the correcting polarization-selective “H-PDLC” diffractive optical element 23 is
The light is transmitted through the polarizing plate 28 that selectively transmits the P-polarized component, and is incident on the polarization-selective “H-PDLC” diffractive optical element 3. At this time, the correction polarization-selective “H-PDLC” diffractive optical element 23 and the polarization-selective “H-PDLC” diffractive optical element 3 have the same structure and are arranged parallel to each other. Therefore, the polarization selectivity "H-
The incident angle of the illumination light on the “PDLC” diffractive optical element 3 is equal to the exit angle of the illumination light from the correction polarization-selective “H-PDLC” diffractive optical element 23.

The illuminating light mainly incident on the polarization-selective “H-PDLC” diffractive optical element 3 and mainly composed of P-polarized light components is emitted in a direction substantially perpendicular to the polarization-selective “H-PDLC” diffractive optical element 3. The light is diffracted and enters the cross dichroic prism 32, and this cross dichroic prism 32
Is split into red light, green light, and blue light.

The separated color lights are incident on the corresponding reflection type spatial light modulators 10r, 10g and 10b, where they are modulated and reflected for each color light and for each pixel.
The modulated color lights again enter the cross dichroic prism 32, are re-combined, and are again polarized-selective "H".
-PDLC "incident on the diffractive optical element 3. At this time, S
The polarization component passes through the polarization-selective “H-PDLC” diffractive optical element 3 without being diffracted, further passes through the polarizing plate 24 that selectively transmits the S-polarization component, and enters the projection optical system 25. . Then, with this projection optical system 25,
A display image is formed on the screen 26.

[Seventh Embodiment of Image Display Device] As a seventh embodiment of the image display device according to the present invention, FIG.
As shown in FIG. 9, a color projection type image display device using two reflective FLC panels as reflective spatial light modulators will be described.

In this image display device, the illumination light source 2
The illumination light emitted from the illumination optical system 2 has the functions of correcting the cross-sectional shape of the light flux, making the intensity uniform, and controlling the divergence angle.
Incident on 1. This illumination optical system 21 has a polarization conversion means (not shown), and in the case of this embodiment, the incident light to the polarization selective “H-PDLC” diffractive optical element 3 is P-polarized light, Set the polarization direction of the S-polarized component of the illumination light to 9
By rotating it by 0 °, it is converted into P-polarized light and the light utilization efficiency is improved.

The illumination light that has passed through the illumination optical system 21 enters the color shutter 22 after passing through the polarizing plate 28 that selectively transmits the P-polarized component. The color shutter 22 has a function of rotating the polarization azimuth of a specific wavelength band of the linearly polarized white light emitted from the illumination light source 20 by 90 °. Therefore, the illumination light transmitted through the color shutter 22 can be time-divided into partial spectral components by polarization detection. Such time division enables color display by the "field sequential color method" by the single-plate reflective FLC panel 10 (reference paper: "Gray D. Sharp and
Kristina M. Johnson, High Brightness Saturated Col
or Shutter Technology, SID Symposium, Vo1.27, p41
1 (1996) ").

In this embodiment, the color shutter 22 is controlled so that two spectra of red light and blue light (magenta) and red light and green light (yellow) are transmitted in a time division manner. That is, the polarization directions of the green light and the blue light incident from the illumination light source 20 are alternately rotated by 90 °. The illumination light transmitted through the color shutter 22 is incident on the correction polarization-selective “H-PDLC” diffractive optical element 23, where only the P-polarized component is diffracted and the exit angle is about 60.
Injected at °. At this time, the color shutter 22
The green light or the blue light made into the S-polarized light is alternately corrected without being diffracted.
It goes straight through the “C” diffractive optical element 23 and is transmitted.

The illumination light mainly composed of the P-polarized light component diffracted by the correction polarization-selective “H-PDLC” diffractive optical element 23 is used as the polarization-selective “H-PDLC” diffractive optical element 3.
Incident on. At this time, the polarization selectivity for correction "H-PDL
Since the “C” diffractive optical element 23 and the polarization selective “H-PDLC” diffractive optical element 3 have the same configuration and are arranged in parallel to each other, the polarization selective “H-PD”
The angle of incidence of the illumination light on the “LC” diffractive optical element 3 is equal to the angle of exit of the illumination light from the correction polarization-selective “H-PDLC” diffractive optical element 23.

Polarization Selectivity “H-PDLC” The P-polarized component of the illumination light incident on the diffractive optical element 3 has a polarization selectivity “H-PDLC”.
The light is diffracted by the “PDLC” diffractive optical element 3 so as to be emitted almost vertically, and then enters the dichroic prism 34. The illumination light incident on the dichroic prism 34 is
Only the red light is deflected by 90 ° in the traveling direction, and the remaining illumination light mainly in the wavelength bands of green light and blue light is transmitted. The two separated color lights are reflected by the corresponding reflective spatial light modulator 10
These reflection type spatial light modulators 1 are made incident on r and 10 gb.
At 0r and 10gb, each color light and each pixel are modulated and reflected.

However, the green light and the blue light are displayed in a time division manner by the "field sequential color method". Time-division display for green light and blue light,
The reason why red light is not displayed in a time-division manner is that when a normal lamp light source is used, the red light has the shortest output when the white balance is taken in consideration of the visual sensitivity of the eye.

The modulated color lights again enter the dichroic prism 34, are recombined, and enter the polarization selective "H-PDLC" diffractive optical element 3 again. At this time, the S-polarized component is transmitted without being diffracted, and further enters the projection optical system 25 via the polarizing plate 24 which selectively transmits the S-polarized component. Then, with this projection optical system 25,
A display image is formed on the screen 26.

Further, as shown in FIG. 20, the space between the correction polarization-selective “H-PDLC” diffractive optical element 23 and the polarization-selective “H-PDLC” diffractive optical element 3 is filled with a glass plate 20, Polarization Selectivity for Correction "H-PDL
C "diffractive optical element 23 and polarization selectivity" H-PDLC "
The diffraction efficiency can be improved by increasing the effective bend angle of the hologram layer of the diffractive optical element 3.

However, at this time, the polarization selectivity for correction "H
-PDLC "diffractive optical element 23 and polarization selectivity" HP "
The wavelength band and the incident angle range in which the diffraction effect occurs in the DLC ”diffractive optical element 3 are reduced. The correction polarization selective “H-PDLC” diffractive optical element 23 and the glass plate 2
0 and between the polarization-selective “H-PDLC” diffractive optical element 3 and the glass plate 20 need to be optically in close contact with each other.

[Eighth Embodiment of Image Display Device] As an eighth embodiment of the image display device according to the present invention, FIG.
As shown in FIG. 1, a color projection type image display device using three reflection type TN vertical alignment liquid crystal panels 10r, 10g and 10b as reflection type spatial light modulation elements will be described.

In this image display device, the illumination light source 2
The illumination light emitted from the illumination optical system 2 has the functions of correcting the cross-sectional shape of the light flux, making the intensity uniform, and controlling the divergence angle.
Incident on 1. This illumination optical system 21 has a polarization conversion means (not shown), and in the case of this embodiment, the incident light to the polarization selective “H-PDLC” diffractive optical element 3 is P-polarized light, Set the polarization direction of the S-polarized component of the illumination light to 9
By rotating it by 0 °, it is converted into P-polarized light and the light utilization efficiency is improved.

The illumination light that has passed through the illumination optical system 21 is incident on the correction polarization-selective “H-PDLC” diffractive optical element 23, where only the P-polarized component is diffracted and reflected, and the polarization selectivity “H -PDLC "incident on the diffractive optical element 3. The S-polarized light component of the illuminating light has a polarization selectivity “H-PDL
Without being diffracted by the “C” diffractive optical element 23, it goes straight and passes through the correction polarization-selective “H-PDLC” diffractive optical element 23.

Here, the correction polarization selectivity "H-PDL" is used.
The “C” diffractive optical element 23 is a reflective polarization selective “H-PD
It is an "LC" diffractive optical element. In the case of the reflective type, the allowable value of the diffraction wavelength band is smaller than that of the transmissive type, so that the illumination light source 20 should have a spectrum with a steep peak value, or a hologram should be created for each of a plurality of wavelength bands. Then, by stacking these, the polarization selectivity for correction "H-
The PDLC ”diffractive optical element 23 is effective.

The illumination light mainly incident on the polarization-selective “H-PDLC” diffractive optical element 3 and mainly composed of the P-polarized component is diffracted so as to be emitted substantially vertically from the polarization-selective “H-PDLC” diffractive optical element 3. Then, the light enters the dichroic prism block 35. The dichroic prism block 35 is composed of three dichroic prisms and has two boundary surfaces 35b and 35g. The illumination light that has entered the dichroic prism block 35 first enters one boundary surface 35b, reflects only blue light, and the light excluding blue that has passed through this boundary surface 35b enters the other boundary surface 35g. . Then, only the green light is reflected on the other boundary surface 35g, so that the illumination light becomes R
It is split into each color of (red), G (green), and B (blue).

The respective color lights thus separated are incident on the corresponding reflection type spatial light modulation elements 10r, 10g and 10b, and the reflection type spatial light modulation elements 10r, 10g and 10b.
By b, it is modulated and reflected for each color light and for each pixel. The modulated color lights again enter the cross dichroic prism block 35, are recombined, and enter the polarization selective “H-PDLC” diffractive optical element 3 again. At this time, the S-polarized component is transmitted without being diffracted, and further enters the projection optical system 25 via the polarizing plate 24 which selectively transmits the S-polarized component. Then, this projection optical system 25
Thus, a display image is formed on the screen 26.

[Ninth Embodiment of Image Display Device] As a ninth embodiment of the image display device according to the present invention, FIG.
As shown in FIG. 2, a color projection type image display device using two reflective FLC panels as reflective spatial light modulators will be described.

In this image display device, the illumination light source 2
The illumination light emitted from the illumination optical system 2 has the functions of correcting the cross-sectional shape of the light flux, making the intensity uniform, and controlling the divergence angle.
Incident on 1. The illumination optical system 21 has a polarization conversion means (not shown), and in the case of this embodiment, the incident light to the polarization selective “H-PDLC” diffractive optical element 3 is S polarized light, Set the polarization direction of the P-polarized component of the illumination light to 9
By rotating it by 0 °, it is converted into S-polarized light and the light utilization efficiency is improved.

The illumination light that has passed through the illumination optical system 21 passes through the polarizing plate 28 that selectively transmits the S-polarized component and enters the color shutter 22. The color shutter 22 time-divides the white light emitted from the illumination light source 20 into its partial spectral components.
Color display is possible on the LC panel 10 by the “field sequential color method” (reference paper: “Gray
D. Sharp and Kristina M. Johnson, High Brightness
Saturated Color Shutter Technology, SID Symposiu
m, Vo1.27, p411 (1996) ”).

In this embodiment, the color shutter 22 is controlled so that two spectra of red light and blue light (magenta) and red light and green light (yellow) are transmitted in a time division manner. That is, the polarization directions of the incident green light component and blue light component are alternately rotated by 90 ° to form P-polarized light. The illumination light emitted from the color shutter 22 is
The light enters the correction polarization-selective “H-PDLC” diffractive optical element 23, where only the S-polarized component is diffracted and the exit angle is about 7.
Ejected at 0 °. At this time, the color shutter 2
The green light or blue light made into P-polarized light in 2 is
It goes straight without being diffracted by the correction polarization-selective “H-PDLC” diffractive optical element 23, and alternately passes through the correction polarization-selective “H-PDLC” diffractive optical element 23.

The illumination light mainly composed of the S polarization component diffracted by the correction polarization-selective “H-PDLC” diffractive optical element 23 is optically guided to the correction polarization-selective “H-PDLC” diffractive optical element 23. It is incident on the first coupling prism 37 that is closely adhered. Polarization Selectivity for Correction "H-PD
The illumination light emitted from the “LC” diffractive optical element 23 is transmitted through the first coupling prism 37 and the correction polarization selectivity “HP”.
Since the glass substrate 36 of the “DLC” diffractive optical element 23 is made of a glass material having substantially the same refractive index,
Refraction does not occur at these junction interfaces, and the light enters the first coupling prism 37 without changing the angle.

The illumination light incident on the first coupling prism 37 is emitted from the optical surface 38 of the first coupling prism 37 substantially vertically. Then, this illumination light enters the color select 33. This color select 33 changes the incident linear polarization azimuth to 9 depending on the wavelength band.
It is rotated by 0 ° (reference paper: "Gray D. Shar
p and J. R. Birge, Retarder Stack Technology for Co
lor Manipulation, SID Symposium, Vo1.30, p1072 (19
99) ").

In this embodiment, the incident polarization azimuth (S-polarized light) of the red light is preserved, and the polarization azimuths of the blue light and the green light are rotated by 90 ° to be P-polarized light.
The illumination light emitted from the color select 33 enters from the optical surface 39 to the second coupling prism 19 which is optically closely bonded to the polarization selective “H-PDLC” diffractive optical element 3. The optical surface 39 is substantially parallel to the optical surface 38 of the first coupling prism 37. Therefore, the incident illumination light is transmitted through the second coupling prism 19
The light travels straight on the optical surface 39 with almost no refraction and directly enters the polarization-selective “H-PDLC” diffractive optical element 3.

In this polarization-selective "H-PDLC" diffractive optical element 3, the red light which is S-polarized light is transmitted through the third coupling prism 40 without being diffracted and is reflected spatial light for red light. It is incident on the modulation element 10r. on the other hand,
Blue light and green light that are P-polarized light are diffracted to about 70
° The third cup ring prism 4 is deflected in the traveling direction.
The light enters the reflective spatial light modulator for blue-green light 10gb through 0.

At this time, since the blue light and the green light are alternately sent by the color shutter 22 in a time division manner, the reflective spatial light modulator for blue-green light 10gb is controlled in synchronization therewith. The reason why green light and blue light are time-divisional display and red light is not time-divisional display is that when a normal lamp light source is used, red light is emitted when white balance is taken in consideration of the visual sensitivity of the eye. This is because the output is the most insufficient.

Each reflection type spatial light modulator 10b,
The illumination light modulated at 10 gb has polarization selectivity "HP
It re-enters the DLC ”diffractive optical element 3. At this time, the S-polarized component of the reflected light from the reflection type spatial light modulator for blue-green light 10gb is not diffracted and the polarization selectivity "H".
-PDLC "Emits from the diffractive optical element 3 substantially vertically. In addition, the P-polarized component of the reflected light from the reflective spatial light modulator for red light 10r is diffracted and the polarization selectivity "HP" is obtained.
DLC ”diffractive optical element 3 also emits substantially vertically.

These two reflected lights pass through the second coupling prism 19 and enter the color select 33b joined to the optical surface of the second coupling prism 19. In this color select 33b, the incident polarization azimuth (S-polarized light) of the blue-green light is preserved, and the polarization azimuth of the red light is rotated by 90 ° to be S-polarized light.

These illumination lights enter the projection optical system 25 through the polarizing plate 24 which selectively transmits the S-polarized light. Then, the display image is formed on the screen 26 by the projection optical system 25.

On the other hand, a reflection type spatial light modulator for blue-green light 1
The P-polarized component of the reflected light from 0 gb is diffracted and transmitted by the polarization-selective “H-PDLC” diffractive optical element 3, and travels backward in the forward illumination optical path. In addition, the S-polarized component of the reflected light from the reflective spatial light modulator for red light 10r is not diffracted by the polarization-selective “H-PDLC” diffractive optical element 3 and also reverses the illumination optical path of the forward path. To do.

Also, in this embodiment, as shown in FIG. 23, the correction polarization-selective “H-PDLC” diffractive optical element 23, the first coupling prism 37, the color select 33, and the second coupling are used. The prism 19, the polarization-selective “H-PDLC” diffractive optical element 3, the third coupling prism 40, and the color select 33b may be optically joined.

[Tenth Embodiment of Image Display Device] As a tenth embodiment of the image display device according to the present invention,
As shown in FIG. 24, a color projection type image display device using a reflective FLC panel as a reflective spatial light modulator will be described.

In this image display device, the illumination light source 2
The illumination light emitted from the illumination optical system 2 has the functions of correcting the cross-sectional shape of the light flux, making the intensity uniform, and controlling the divergence angle.
Incident on 1. This illumination optical system 21 has a polarization conversion means (not shown), and in the case of this embodiment, the incident light to the polarization selective “H-PDLC” diffractive optical element 3 is P-polarized light, Set the polarization direction of the S-polarized component of the illumination light to 9
By rotating it by 0 °, it is converted into P-polarized light and the light utilization efficiency is improved.

The illumination light that has passed through the illumination optical system 21 passes through the color wheel 22 and undergoes correction polarization selectivity "H-PD".
It is incident on the “LC” diffractive optical element 23. Color wheel 2
2 represents white light emitted from the illumination light source 20, red light,
It is time-divided into green and blue light spectral components.
This time division enables color display by the "field sequential color method" on the single-plate reflective FLC panel 10.

The illumination light incident on the correction polarization-selective “H-PDLC” diffractive optical element 23 at an incident angle of 60 ° is diffracted only at the P-polarized component, and is emitted at an emission angle of about 0 °. The S-polarized component is a polarization-selective “H-PDL” for correction.
Without being diffracted by the “C” diffractive optical element 23, it goes straight and passes through the correction polarization-selective “H-PDLC” diffractive optical element 23.

The illumination light mainly composed of the P-polarized light component diffracted by the correction polarization-selective “H-PDLC” diffractive optical element 23 enters the polarization-selective “H-PDLC” diffractive optical element 3. The polarization-selective “H-PDLC” diffractive optical element 23 for correction and the polarization-selective “H-PDLC” diffractive optical element 3 have the same configuration, and the polarization-selective “H-PDLC” for correction is correct. The diffractive optical element 23 and the polarization-selective “H-PDLC” diffractive optical element 3 are arranged so that the incident angles of the illumination light are substantially the same. However,
When viewed from the illumination light (incident side), the diffraction directions (bend angles) of both are opposite. With this arrangement,
As described above, there are two merits that the variation of the diffraction angle due to the wavelength can be canceled and the difference of the incident angle dependency of the diffraction efficiency depending on the wavelength can be corrected.

The correction polarization selectivity "H-PDL" is used.
The space between the “C” diffractive optical element 23 and the polarization-selective “H-PDLC” diffractive optical element 3 may be filled with a coupling prism 19, as indicated by the broken line in FIG. However, in this case, since the bend angle is different, the correction polarization-selective “H-PDLC” diffractive optical element 23 and the polarization-selective “H-PDLC” diffractive optical element 3 are the same hologram element. Don't

Here, the correction polarization selectivity "H-PDL" is used.
The incident angle on the “C” diffractive optical element 23 is determined by the polarization selectivity “HP
The angle of incidence to the DLC ”diffractive optical element 3 is about 60 °, as described in the first embodiment.
This is to reduce the incident angle dependence of the diffraction efficiency of the correction polarization selective “H-PDLC” diffractive optical element 23.

Polarization Selectivity “H-PDLC” The P-polarized light diffracted by the diffractive optical element 3 has the polarization selectivity “H-PDLC”.
The light is emitted from the “PDLC” diffractive optical element 3 at an emission angle of 0 ° and enters the reflective spatial light modulation element 10. The reflective spatial light modulator 10 is arranged so that the longitudinal direction indicated by the arrow a in FIG. 24 matches the illumination light incident angle direction. This is because it is necessary to reduce the effective width of the incident illumination light in the diffraction direction to the correction polarization-selective “H-PDLC” diffractive optical element 23. This is to increase efficiency.

Further, for the same reason, the longitudinal direction of the light emitting portion 20a of the illumination light source 20 is set to the direction perpendicular to the paper surface in FIG. This is because the smaller the light emitting unit is, the smaller the diffusion angle is when the light beam diameter is narrowed, and thus the larger the diffusion angle is, the larger the invariant of the Lagrange-Helmholtz described above. This is because when the light is obliquely incident on the light modulation element, it is effective to shorten the length of the light emitting portion in the direction that coincides with the incident direction in order to improve the light utilization efficiency.

The S-polarized light whose phase is modulated and reflected by the reflective spatial light modulator 10 is reflected by the polarization selectivity "H-PD".
The light is transmitted through the “LC” diffractive optical element 3 and the polarizing plate 24 that selectively transmits only the S-polarized light, and then enters the projection optical system 25. By this projection optical system 25, the optical image displayed on the reflective FLC panel 10 is enlarged and projected as a display image on the screen 26.

On the other hand, the polarization selectivity "H-
The remaining illumination light on the outward path that is not diffracted by the “PDLC” diffractive optical element 3 passes through the polarization-selective “H-PDLC” diffractive optical element 3 as it is, and is positively reflected by the aluminum reflection surface 14 of the reflective spatial light modulation element 10. It is reflected and emitted again in the direction of C in FIG. This illumination light becomes stray light, which may cause deterioration of the contrast of the display image.
The energy is absorbed by 7.

[Eleventh Embodiment of Image Display Device] As an eleventh embodiment of the image display device according to the present invention,
As shown in FIG. 25, a color projection type image display device using a reflective FLC panel as a reflective spatial light modulator will be described.

In this image display device, the illumination light source 2
The illumination light emitted from the illumination optical system 2 has the functions of correcting the cross-sectional shape of the light flux, making the intensity uniform, and controlling the divergence angle.
Incident on 1. This illumination optical system 21 has a polarization conversion means (not shown), and in the case of this embodiment, the incident light to the polarization selective “H-PDLC” diffractive optical element 3 is P-polarized light, Set the polarization direction of the S-polarized component of the illumination light to 9
By rotating it by 0 °, it is converted into P-polarized light and the light utilization efficiency is improved.

The illumination light that has passed through the illumination optical system 21 passes through the color wheel 22 and is subjected to correction polarization selectivity "H-PD".
It is incident on the “LC” diffractive optical element 23. Color wheel 2
2 represents white light emitted from the illumination light source 20, red light,
It is time-divided into green and blue light spectral components.
This time division enables color display by the "field sequential color method" using the single-plate reflective FLC panel 10.

The illumination light that has entered the correction polarization-selective “H-PDLC” diffractive optical element 23 at the incident angle θin23 is diffracted only at the P-polarized component, and is emitted at the exit angle θout23. The S-polarized component is a polarization selective “H-PD
Without being diffracted by the “LC” diffractive optical element 23,
This correction polarization selective “H-PDLC” diffractive optical element 2
Go straight through 3

The illumination light mainly composed of the P-polarized light component diffracted by the correction polarization-selective “H-PDLC” diffractive optical element 23 is transmitted to the polarization-selective “H-PDLC” diffractive optical element 3.
It is incident at an incident angle θin3. At this time, the correction polarization selectivity “H-PDLC” diffractive optical element 23 and the polarization selectivity “H” are used.
-PDLC "diffractive optical element 3 has the same structure as
Moreover, the incident angle θin23 and the exit angle θout23 to the correction polarization selective “H-PDLC” diffractive optical element 23 are the same as the incident angle θin3 to the polarization selective “H-PDLC” diffractive optical element 3.
It is made equal to the emission angle θout3. However,
When viewed from the illumination light, the diffraction directions (bend angles) of both are opposite. Therefore, as described above, it is possible to cancel the variation in the diffraction angle depending on the wavelength and to correct the difference in the incident angle dependence of the diffraction efficiency depending on the wavelength.
You get two merits.

In the case of this embodiment, the polarization-selective “H-PDLC” diffractive optical element 3 and the reflective spatial light modulator 10 have an opening angle of θholo as shown in FIG. Will be placed. That is, the polarization selectivity "H-PDL
C "diffractive optical element 3, correction polarization selectivity" H-PDL "
In order to reduce the dependency of the diffraction efficiency of the “C” diffractive optical element 23 on the wavelength and the incident angle, it is effective to reduce the bend angle. At this time, (i) the incident angle is reduced. (Ii) Increase the emission angle in the direction of decreasing the bend angle. There are two possible methods. In the case of the method (i) of "increasing the incident angle", the variation of the incident angle to the hologram layer becomes large as described above, which is not preferable. Therefore, it is effective to use the method (ii) of "increasing the exit angle in the direction of decreasing the bend angle".

In the case of this embodiment, the polarization selectivity "H-
PDLC "diffractive optical element 3, polarization selection for correction" HP "
DLC ”Diffractive optical element 23 exit angles θout3, θout2
3 is set to about 5 ° to 20 ° to reduce the bend angle. In this way, incident illumination light and polarization selectivity "H-PDL
"C" diffractive optical element 3 and correction polarization selectivity "H-PDL"
When the relative relationship of the “C” diffractive optical element 23 is defined, it is attempted to make the diffracted light emitted from the polarization-selective “H-PDLC” diffractive optical element 3 enter perpendicularly to the reflective spatial light modulator 10. As shown in FIG. 25, the polarization selective “H-PDLC” diffractive optical element 3 and the reflective spatial light modulator 10 need to be arranged with an opening angle of θholo (= θout3).

In this way, the polarization selectivity "H-PDL" is
The P-polarized light diffracted by the “C” diffractive optical element 3 is incident on the reflective spatial light modulator 10 substantially vertically. The reflective spatial light modulator 10 is arranged so that the longitudinal direction indicated by the arrow a in FIG. 25 coincides with the illumination light incident angle direction. This is because it is necessary to reduce the effective width of the incident illumination light in the diffraction direction to the correction polarization-selective “H-PDLC” diffractive optical element 23. This is to increase efficiency.

For the same reason, the longitudinal direction of the light emitting portion 20a of the illumination light source 20 is set to the direction perpendicular to the paper surface in FIG. This is because the smaller the light emitting unit is, the smaller the diffusion angle is when the light beam diameter is narrowed, and thus the larger the diffusion angle is, the larger the invariant of the Lagrange-Helmholtz described above. This is because when the light is obliquely incident on the light modulation element, it is effective to shorten the length of the light emitting portion in the direction that coincides with the incident direction in order to improve the light utilization efficiency.

The S-polarized light whose phase is modulated by the reflective spatial light modulator 10 and reflected is the polarization selectivity "H-PD".
The light is transmitted through the “LC” diffractive optical element 3 and the polarizing plate 24 that selectively transmits only the S-polarized light, and then enters the projection optical system 25. Here, the polarizing plate 24 has a polarization selectivity of “H-PDL”.
In order to correct the astigmatism generated by passing through the “C” diffractive optical element 3, the polarization selective “H-PDLC” diffractive optical element 3 is directed in the direction opposite to the tilt angle θholo with respect to the reflective spatial light modulator 10. They are arranged with the same absolute value of inclination angle θpol. Due to the inclination of the polarizing plate 24, it is possible to cancel astigmatism in the modulated illumination light. Then, by the illumination light incident on the projection optical system 25,
The optical image displayed on the reflective spatial light modulator 10 is enlarged and projected as a display image on the screen 26.

[Embodiment of Virtual Image Display Device (First
Second Embodiment)] The twelfth embodiment of the image display device according to the present invention
As an embodiment of the present invention, as shown in FIG. 26, an image display device using a virtual image forming optical system using a reflective FLC panel as a reflective spatial light modulator will be described.

In this image display device, the illumination light emitted from the light emitting diode light source 41 with a lens that sequentially emits three colors of red light, green light and blue light independently and selectively transmits the P polarization component. The light passes through the polarization plate 42 and enters the polarization selective “H-PDLC” diffractive optical element 3. This incident light is diffracted by the polarization-selective “H-PDLC” diffractive optical element 3 and reflected almost vertically to the reflective FLC panel 1.
It is incident on 0.

The illumination light whose phase is modulated by the reflection type FLC panel 10 is reflected by the aluminum reflection surface 14 of the reflection type FLC panel 10, and again the polarization selectivity "H-PDL" is obtained.
It is incident on the “C” diffractive optical element 3. At this time, the P-polarized component is again diffracted by the polarization-selective “H-PDLC” diffractive optical element 3 toward the light-emitting diode light source 41, while the S-polarized component is polarized-selective “H-PDLC” diffractive optics. The light is transmitted as it is without being diffracted by the element 3. The S-polarized light transmitted through the polarization-selective “H-PDLC” diffractive optical element 3 is detected by the polarizing plate 43 that selectively transmits the S-polarized component, and then the free-form surface prism 44 constituting the virtual image observation optical system. Is incident on the free curved surface 45.

The light incident on the free-form surface prism 44 is
The light is totally reflected by the first optical surface 46, then reflected by the second free-form curved reflecting surface 47, then transmitted through the first optical surface 46, and guided to the observation region 48 of the observer. At this time, in order to enlarge the observation area 48, a diffusion plate is arranged between the light emitting diode light source 41 and the polarizing plate 42, or
Alternatively, in the polarization-selective “H-PDLC” diffractive optical element 3, interference fringes that cause a diffusing action at the time of diffraction with respect to the P-polarized component incident on the polarization-selective “H-PDLC” diffractive optical element 3 are recorded in advance. You may keep it.

[Embodiment of Virtual Image Display Device (First
Third Embodiment)] Next, as a thirteenth embodiment of the image display device according to the present invention, as shown in FIG. 27, two reflection FLC panels are used as reflection spatial light modulators to form a virtual image. An image display device using the image optical system will be described.

In this image display device, the illumination light emitted from the light-emitting diode light source 41 with a lens that sequentially emits three colors of red light, green light, and blue light independently, selects a polarization component that becomes P-polarized light. The light is incident on the polarization-selective “H-PDLC” diffractive optical element 3 via the polarizing plate 42 that is transparent to light. In this embodiment, the polarization selectivity "HP
The DLC ”diffractive optical element 3 is of the reflective type. The illumination light incident on the polarization-selective “H-PDLC” diffractive optical element 3 is polarized by the polarization-selective “H-PDLC” diffractive optical element 3.
The light is diffracted and reflected at and enters the reflective FLC panel 10 substantially vertically.

The illumination light whose phase is modulated in the reflection type FLC panel 10 is reflected by the aluminum reflection surface 14 of the reflection type FLC panel 10, and again the polarization selectivity "H-PD" is obtained.
It is incident on the “LC” diffractive optical element 3. At this time, the P-polarized light component of the illumination light is again diffracted and reflected by the polarization-selective “H-PDLC” diffractive optical element 3 and travels toward the light-emitting diode light source 42. The S-polarized component has a polarization selectivity of "H
The light passes through the polarization-selective “H-PDLC” diffractive optical element 3 as it is without being diffracted by the “PDLC” diffractive optical element 3.

The S-polarized light transmitted through the polarization-selective “H-PDLC” diffractive optical element 3 in this way is detected by the polarizing plate 43 that selectively transmits the S-polarized component, and then the virtual image observation optical system is used. The light enters the constituent free-form surface prism 44 from the free-form surface refracting surface 45.

The light incident on the free-form surface prism 44 is
The light is totally reflected by the first optical surface 46, then reflected by the second free-form curved reflecting surface 47, then transmitted through the first optical surface 46, and guided to the observation region 48 of the observer. At this time, in order to enlarge the observation area 48, a diffusion plate is arranged between the light emitting diode light source 41 and the polarizing plate 42, or
Alternatively, in the polarization-selective “H-PDLC” diffractive optical element 3, interference fringes that cause a diffusing action at the time of diffraction with respect to the P-polarized component incident on the polarization-selective “H-PDLC” diffractive optical element 3 are recorded in advance. You may keep it.

[0199]

As described above, in the diffractive optical element according to the present invention, when the element temperature is within the operating temperature range of the diffractive optical element (for example, 25 ° C. to 70 ° C.), Polarization selection with high polarization splitting characteristics by minimizing the difference in refractive index between the first region and the second region, which have different refractive index anisotropy and temperature dependence of refractive index, with respect to a specific incident polarization direction. It can be configured as a diffractive optical element of a refractive index modulation type.

Therefore, according to the present invention, in particular, in a polarization-selective refractive index modulation type diffractive optical element using a material such as a liquid crystal material whose refractive index has a relatively large temperature dependence as a constituent element, for example, an image display. Even when used in a device (projector device) where the element temperature is usually higher than room temperature, the polarization separation characteristics and the diffraction efficiency of non-diffracted polarized light can be optimized and minimized, respectively.

That is, according to the present invention, like a liquid crystal material,
In a polarization-selective refractive index modulation type diffractive optical element using a material whose refractive index has a relatively large temperature dependence as a constituent element, even in a situation where the element temperature is higher than room temperature such as in an image display device (projector device). The polarization splitting characteristics can be optimized. Then, the present invention can provide an image display device configured by using such a diffractive optical element.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a manufacturing process of a diffractive optical element according to the present invention.

FIG. 2 is a graph showing temperature dependence of refractive index and temperature dependence of diffraction efficiency in each region of P-polarized light and S-polarized light in the diffractive optical element.

FIG. 3 is a plan view showing changes in the apparent refractive index of liquid crystal molecules due to temperature changes in the diffractive optical element.

FIG. 4 is a graph showing temperature dependence of refractive index and temperature dependence of diffraction efficiency in each region of S-polarized light in the diffractive optical element.

FIG. 5 is a graph showing an actually measured value of temperature dependence of a refractive index change with respect to S-polarized light in a liquid crystal region in the diffractive optical element.

FIG. 6 is a graph showing measured values of temperature dependence of refractive index changes in the liquid crystal region and the polymer region of the diffractive optical element with respect to S-polarized light.

FIG. 7 is a vertical cross-sectional view showing the configuration of the first embodiment of the image display device according to the present invention.

FIG. 8 is a vertical sectional view showing the configuration of the second embodiment of the image display device according to the present invention.

FIG. 9 is a vertical cross-sectional view showing a configuration of a third embodiment of an image display device according to the present invention.

FIG. 10 is a vertical cross-sectional view showing the configuration of a fourth embodiment of the image display device according to the present invention.

FIG. 11 is a vertical cross-sectional view showing the configuration of the main parts of a fourth embodiment of an image display device according to the present invention.

FIG. 12 is a graph showing the incident angle dependence of the diffraction efficiency of blue light in the diffractive optical element.

FIG. 13 is a graph showing the incident angle dependence of the diffraction efficiency of green light in the diffractive optical element.

FIG. 14 is a graph showing incident angle dependence of diffraction efficiency of red light in the diffractive optical element.

FIG. 15 is an incident angle dependency and a reproduction wavelength dependency of a diffraction efficiency of green light in the diffractive optical element (large bend angle (θ
(ob1 = 10 °)).

FIG. 16 shows the incident angle dependence and the reproduction wavelength dependence of the diffraction efficiency of green light in the diffractive optical element (small bend angle (θ
(ob1 = -10 °))).

FIG. 17 is a vertical sectional view showing the configuration of the fifth embodiment of the image display device according to the present invention.

FIG. 18 is a vertical sectional view showing a configuration of a sixth embodiment of the image display device according to the present invention.

FIG. 19 is a vertical sectional view showing a configuration of a seventh embodiment of an image display device according to the present invention.

FIG. 20 is a vertical cross-sectional view showing a seventh embodiment of the image display device according to the present invention, in which a coupling prism is added.

FIG. 21 is a vertical sectional view showing the configuration of the eighth embodiment of the image display device according to the present invention.

FIG. 22 is a vertical sectional view showing a configuration of a ninth embodiment of the image display device according to the present invention.

FIG. 23 is a vertical sectional view showing a ninth embodiment of the image display device according to the present invention, in which a coupling prism is added.

FIG. 24 is a vertical cross-sectional view showing the configuration of the tenth embodiment of the image display device according to the present invention.

FIG. 25 is a vertical sectional view showing a configuration of an eleventh embodiment of an image display device according to the present invention.

FIG. 26 is a vertical sectional view showing the configuration of the twelfth embodiment of the image display device according to the present invention.

FIG. 27 is a vertical sectional view showing the configuration of the thirteenth embodiment of the image display device according to the present invention.

FIG. 28 is a vertical sectional view showing a basic structure of a diffractive optical element.

FIG. 29 shows P-polarized light and S in a conventional diffractive optical element.
It is a graph which shows the temperature dependence of the refractive index in each area | region of polarized light, and the temperature dependence of diffraction efficiency.

[Explanation of symbols]

1, 2 glass substrate, 3 "H-PDLC" panel, 4
Reference light, 5 object light, 6 polymer region, 7 liquid crystal region, 10 reflective FLC liquid crystal panel

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02F 1/1335 520 G02F 1/1335 520 1/13357 1/13357 // G03F 7/004 521 G03F 7/004 521 F-term (reference) 2H025 AB14 BC14 BC32 BC42 BH05 2H049 AA25 AA34 AA43 AA50 AA60 BA05 BA45 BB03 BC22 2H088 EA33 EA48 FA21 HA01 HA02 HA03 HA13 HA18 HA21 HA28 JA05 KA06 MA02 MA06 MA20 2H091 FA05X FA07X FA08X FA14Y FA19X FA31X FA37X FA41X FA45X FB02 FB11 FC01 FC10 FC22 FC23 GA01 GA02 GA03 GA06 GA08 HA07 HA12 KA01 LA15 LA17 2H099 AA12 BA09 CA17 DA03

Claims (29)

[Claims] 1. A polarization selectivity for diffracting incident light, which has a structure in which first regions and second regions having different refractive index anisotropy and temperature dependence of refractive index are arranged alternately. A refractive index modulation type diffractive optical element, characterized in that the element temperature at which the diffraction efficiency with respect to incident light of a specific polarization direction has a minimum value is within the range of 25 degrees Celsius or more and 70 degrees Celsius or less. Optical element. 2. The diffractive optical element according to claim 1, wherein the minimum value is 1% or less. 3. The diffractive optical element according to claim 1, wherein the specific polarization azimuth of the incident light is an azimuth parallel to a boundary between the first and second regions. 4. The diffractive optical element according to claim 1, wherein at least one of the first and second regions is a region containing a liquid crystal material. 5. The refractive index of the first region with respect to incident light of the specific polarization direction is smaller than the refractive index of the second region with respect to the incident light at an element temperature of 25 degrees Celsius. , Is large at 70 degrees Celsius, and the refractive index of the first region with respect to the incident light in the polarization direction orthogonal to the specific polarization direction is relative to the refractive index of the second region with respect to the incident light, 2. The diffractive optical element according to claim 1, wherein the element temperature is large in the range of 25 degrees Celsius or more and 70 degrees Celsius or less. 6. The first and second regions are configured to include at least a polymer material and a liquid crystal material, and the first region has a higher liquid crystal material content than the second region. The diffractive optical element according to claim 1, wherein the content of the polymer material is low. 7. A mixture of a photopolymerizable polyfunctional monomer, a photopolymerizable difunctional monomer, a photopolymerizable monofunctional monomer and a liquid crystal is formed in a layer having a predetermined thickness between a pair of optical substrates, and this layer is formed. Is a polarization-selective refractive index modulation type diffractive optical element formed by holographic exposure with respect to, wherein the photopolymerizable bifunctional group monomer is hydroxypivalic acid neopentyl glycol diacrylate, or The diffractive optical element according to claim 1, which is an addition compound. 8. The diffractive optical element according to claim 7, wherein the photopolymerizable bifunctional monomer contains ε-caprolactone-modified neopentyl glycol diacrylate hydroxypivalate. 9. The diffractive optical element according to claim 7, wherein 2-hydroxy-3-phenoxypropyl acrylate is used as the photopolymerizable monofunctional group monomer. 10. The diffractive optical element according to claim 7, wherein N-vinyl-pyrrolidinone is used as the photopolymerizable monofunctional group monomer. 11. The diffractive optical element according to claim 7, wherein trimethylolpropane triacrylate is used as the photopolymerizable polyfunctional monomer. 12. A polarization selectivity for diffracting incident light, which has a structure in which first regions and second regions having different refractive index anisotropy and temperature dependence of refractive index are arranged alternately. A refractive index modulation type diffractive optical element having a diffraction efficiency of 1% with respect to incident light of a specific polarization direction when the element temperature is in the range of 25 degrees Celsius or more and 70 degrees Celsius or less.
A diffractive optical element characterized by the following. 13. The diffractive optical element according to claim 12, wherein the specific polarization azimuth of the incident light is an azimuth parallel to the boundary between the first and second regions. 14. The diffractive optical element according to claim 12, wherein at least one of the first and second regions is a region containing a liquid crystal material. 15. The refractive index of the first region with respect to incident light of the specific polarization azimuth is the second refractive index with respect to the incident light.
The element temperature is small at 25 degrees Celsius and large at 70 degrees Celsius with respect to the refractive index of the area, and the first area of the first area with respect to the incident light in the polarization direction orthogonal to the specific polarization direction is 13. The diffractive optical element according to claim 12, wherein the refractive index is large with respect to the refractive index of the second region with respect to the incident light in a range where the element temperature is 25 degrees Celsius or more and 70 degrees Celsius or less. 16. The first and second regions are configured to include at least a polymer material and a liquid crystal material, and the first and second regions are provided.
13. The diffractive optical element according to claim 12, wherein the region is configured so that the content of the liquid crystal material is higher and the content of the polymer material is lower than that of the second region. 17. A photopolymerizable polyfunctional monomer, a photopolymerizable 2
Polarization-selective refraction formed by forming a mixture of a functional group monomer, a photopolymerizable monofunctional group monomer, and a liquid crystal in a layer having a predetermined thickness between a pair of optical substrates and subjecting this layer to holographic exposure. 13. A diffractive optical element of the rate modulation type, wherein the photopolymerizable bifunctional group monomer is hydroxypivalic acid neopentyl glycol diacrylate or an addition compound thereof. . 18. The photopolymerizable difunctional monomer contains ε-caprolactone-modified neopentyl glycol diacrylate hydroxypivalate.
7. The diffractive optical element according to 7. 19. The diffractive optical element according to claim 17, wherein 2-hydroxy-3-phenoxypropyl acrylate is used as the photopolymerizable monofunctional group monomer. 20. The N-vinyl-pyrrolidinone is used as the photopolymerizable monofunctional group monomer.
The diffractive optical element described. 21. The diffractive optical element according to claim 17, wherein trimethylolpropane triacrylate is used as the photopolymerizable polyfunctional monomer. 22. A light source that emits illumination light, and a structure in which first regions and second regions having different refractive index anisotropy and temperature dependence of the refractive index are alternately arranged are incident. A polarization-selective refractive index modulation type diffractive optical element that diffracts light, an illumination optical system that causes the illumination light emitted from the light source to enter the diffractive optical element, and a polarization of the illumination light diffracted by the diffractive optical element. A reflective spatial light modulator that modulates a state, and an imaging optical system that forms an illumination light that has passed through the reflective spatial light modulator and the diffractive optical element into a real image or a virtual image, and the diffractive optical element, The element temperature at which the diffraction efficiency with respect to the incident light of a specific polarization direction has a minimum value is in the range of 25 degrees Celsius or more and 70 degrees Celsius or less, and the imaging optical system transmits the transmitted light of the diffraction optical element on the screen. Or in the observer's eyes An image display device characterized by projection. 23. A light source for emitting illumination light, and a structure in which first regions and second regions having different refractive index anisotropy and temperature dependence of refractive index are arranged alternately are incident. A polarization-selective refractive index modulation type diffractive optical element that diffracts light, a color separation unit that separates the illumination light into a plurality of different wavelength band components, and an illumination light that is separated into a plurality of different wavelength band components An illumination optical system that enters the diffractive optical element, a plurality of reflective spatial light modulators that respectively modulate polarization states of a plurality of different wavelength band components of the illumination light diffracted by the diffractive optical element, Color synthesizing means for synthesizing illumination light of different wavelength bands respectively modulated by a plurality of reflective spatial light modulators, and imaging optics for forming illumination light passing through the color synthesizing means into a real image or a virtual image. In the diffractive optical element, the element temperature at which the diffraction efficiency for incident light of a specific polarization direction has a minimum value is within a range of 25 degrees Celsius or more and 70 degrees Celsius or less, and the imaging optical system includes An image display device, characterized in that the illumination light transmitted through the diffractive optical element and passed through the color combining means is projected on a screen or an observer's pupil. 24. A light source for emitting illumination light, and a structure in which first regions and second regions having different refractive index anisotropy and temperature dependence of refractive index are arranged alternately are incident. A polarization-selective refractive index modulation type diffractive optical element that diffracts light, an illumination optical system that causes the illumination light emitted from the light source to enter the diffractive optical element, and a polarization of the illumination light diffracted by the diffractive optical element. A reflective spatial light modulator that modulates a state, and an imaging optical system that forms an illumination light that has passed through the reflective spatial light modulator and the diffractive optical element into a real image or a virtual image, and the diffractive optical element, Element temperature is 25 degrees Celsius or more 7 degrees Celsius
Within the range of 0 degrees or less, the diffraction efficiency with respect to the incident light of a specific polarization azimuth is 1% or less, and the imaging optical system projects the transmitted light of the diffractive optical element onto the screen or the observer's pupil. An image display device characterized by the above. 25. A light source for emitting illumination light, and a structure in which first regions and second regions having different refractive index anisotropy and temperature dependence of refractive index are arranged alternately are incident. A polarization-selective refractive index modulation type diffractive optical element that diffracts light, a color separation unit that separates the illumination light into a plurality of different wavelength band components, and an illumination light that is separated into a plurality of different wavelength band components An illumination optical system that enters the diffractive optical element, a plurality of reflective spatial light modulators that respectively modulate polarization states of a plurality of different wavelength band components of the illumination light diffracted by the diffractive optical element, Color synthesizing means for synthesizing illumination light of different wavelength bands respectively modulated by a plurality of reflective spatial light modulators, and imaging optics for forming illumination light passing through the color synthesizing means into a real image or a virtual image. The diffractive optical element has an element temperature of 25 degrees Celsius or more and 7 degrees Celsius or more.
Within the range of 0 degrees or less, the diffraction efficiency with respect to the incident light of a specific polarization azimuth is 1% or less, and the imaging optical system screens the illumination light that has passed through the diffractive optical element and passed through the color combining means. An image display device, characterized in that the image is projected onto an upper part or an observer's pupil. 26. A light source that emits illumination light, and a structure in which first regions and second regions having different refractive index anisotropy and temperature dependence of the refractive index are alternately arranged are incident. A polarization-selective refractive index modulation type diffractive optical element that diffracts light, an illumination optical system that causes the illumination light emitted from the light source to enter the diffractive optical element, and a polarization state of the illumination light that has passed through the diffractive optical element. A reflective spatial light modulating element, and an imaging optical system that forms an illumination light that has passed through the reflective spatial light modulating element and the diffractive optical element into a real image or a virtual image, and the diffractive optical element is The element temperature at which the diffraction efficiency with respect to the incident light having the polarization azimuth has a minimum value is in the range of 25 degrees Celsius or more and 70 degrees Celsius or less, and the imaging optical system causes the diffracted light of the diffractive optical element on the screen or Project on the observer's eyes An image display device characterized by the above. 27. A light source for emitting illumination light, and a structure in which first regions and second regions having different refractive index anisotropy and temperature dependence of refractive index are alternately arranged and incident. A polarization-selective refractive index modulation type diffractive optical element that diffracts light, a color separation unit that separates the illumination light into a plurality of different wavelength band components, and an illumination light that is separated into a plurality of different wavelength band components An illumination optical system that is incident on the diffractive optical element, a plurality of reflective spatial light modulators that respectively modulate polarization states of a plurality of different wavelength band components of the illumination light that has passed through the diffractive optical element, and the plurality of A color synthesizing means for synthesizing the illumination light of different wavelength bands respectively modulated by the reflection type spatial light modulating element, and an image forming optical system for forming the illumination light passing through the color synthesizing means into a real image or a virtual image. In the diffractive optical element, the element temperature at which the diffraction efficiency with respect to incident light of a specific polarization direction has a minimum value is within a range of 25 degrees Celsius or more and 70 degrees Celsius or less, and the imaging optical system includes the diffraction optical element. An image display device characterized in that illumination light diffracted by an optical element and passed through the color combining means is projected on a screen or an observer's pupil. 28. A light source that emits illumination light and a structure in which first regions and second regions having different refractive index anisotropy and temperature dependence of refractive index are alternately arranged are incident. A polarization-selective refractive index modulation type diffractive optical element that diffracts light, an illumination optical system that causes the illumination light emitted from the light source to enter the diffractive optical element, and a polarization state of the illumination light that has passed through the diffractive optical element. A reflective spatial light modulating element, and an imaging optical system for forming illumination light that has passed through the reflective spatial light modulating element and the diffractive optical element into a real image or a virtual image, and the diffractive optical element is an element. Temperature is over 25 degrees Celsius 7 degrees Celsius
Within the range of 0 degrees or less, the diffraction efficiency with respect to the incident light of a specific polarization azimuth is 1% or less, and the imaging optical system projects the diffracted light of the diffractive optical element on the screen or the observer's pupil. An image display device characterized by the above. 29. A light source that emits illumination light, and a structure in which a first region and a second region having different refractive index anisotropy and temperature dependence of the refractive index are alternately arranged are incident. A polarization-selective refractive index modulation type diffractive optical element that diffracts light, a color separation unit that separates the illumination light into a plurality of different wavelength band components, and an illumination light that is separated into a plurality of different wavelength band components An illumination optical system that is incident on the diffractive optical element, a plurality of reflective spatial light modulators that respectively modulate polarization states of a plurality of different wavelength band components of the illumination light that has passed through the diffractive optical element, and the plurality of A color synthesizing means for synthesizing the illumination light of different wavelength bands respectively modulated by the reflection type spatial light modulating element, and an image forming optical system for forming the illumination light passing through the color synthesizing means into a real image or a virtual image. The diffractive optical element has an element temperature of 25 degrees Celsius or more and 7 degrees Celsius.
Within the range of 0 degrees or less, the diffraction efficiency with respect to the incident light of a specific polarization direction is 1% or less, and the imaging optical system diffracts the illumination light diffracted by the diffractive optical element and passed through the color combining means. An image display device characterized by projecting on a screen or an observer's pupil.