JP2000165898A - Polarization lighting device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projector that has a display characteristic with high resolution, high luminance and high contrast by applying a diffracted optical element using a liquid crystal layer with an anisotropic refractive index to a polarization beam splitter for a reflection type light valve and combining it with a projective lens with a small F value. SOLUTION: The projector is provided at least with a light source, a diffraction optical element 102 having an anisotropic refractive index, a reflection type light valve 103, and a projection optical system 104 that projects an optical image on the light valve 103 with magnification. The diffraction optical element has a periodic structure including uniformly arranged liquid crystals and is configured to reflect a P wave component from the light source, to make the S wave component incident onto the light valve and to lead the P wave component of the light wave reflected in the light valve to the projection optical system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illumination device for a projection type projector using a reflection type light bulb and a method of manufacturing the same.

[0002]

2. Description of the Related Art An image display device using a liquid crystal element is widely used as a monitor of a notebook personal computer or a monitor of a portable information terminal because it is thin and lightweight. Also, a projection type projector which displays an image of a small liquid crystal light half-inch of about 1 inch on a large screen by an enlarged projection system.
However, a large market is expected in recent years due to improvements in resolution and brightness. In particular, a device using a reflection type light bulb can effectively use most of the area of a pixel even if one pixel size constituting a screen is reduced with improvement in resolution. For this reason, since the light use efficiency is higher than that of a transmissive light bulb, it is attracting attention as an element capable of responding to further improvement in resolution. Since image display of these liquid crystal elements is generally performed by modulating the polarization direction of light, optical components such as a polarizer and a polarization beam splitter for specifying the polarization direction of the light before and after the liquid crystal light half are used. .

[0003] It is effective to use a polarization beam splitter for the reflection type light bulb because it can be made compact. As this polarization beam splitter, MgF ₂ (refractive index: 1.3) is used.
9) A film having a different refractive index, such as TiO ₂ (refractive index: 2.30), is formed on a transparent external medium by using a film having a high refractive index and a low refractive index.
A type having a structure in which a plurality of types are alternately formed into a multilayer film and sandwiched by another external medium is used.

The polarization beam splitting principle of the polarization beam splitter is generally performed by reflecting S-polarized light and transmitting P-polarized light.
With respect to the P-polarized light, by setting the incident angle with respect to the multilayer film to an angle called Frewster's angle, a condition is used in which the P-polarized light is theoretically not reflected at the interface at all, and is transmitted at 100%.

For S-polarized light, reflection always occurs at the interface of the multilayer film. Therefore, by optimizing the film thickness of each layer, it is possible to reduce the transmitted light intensity as a whole multilayer film and increase the reflected light intensity by the light interference effect. Therefore, by optimizing the thicknesses of all the thin films constituting the multilayer film, it is necessary to use a condition in which the reflected light at the interface reinforces each other, and as a result, the intensity of the S-polarized light reflected by the entire multilayer film becomes large. it can.

[0006]

There is a great demand for a bright display screen in a projection type projector. For this reason, it is necessary to increase the light use efficiency. As an effective means, an optical system having a small F value (focal length / lens diameter) is used so as to take in more light from the light source. At this time, if a projection optical system having a small F-number is used, the amount of light whose angle is greatly shifted from the optical axis direction increases. The maximum angle at this time is represented by the following equation.

(Equation 1) θ = tan ⁻¹ (1 / 2F) In the above equation, the angle when using a lens with F = 3.0 is 9.
It is about 5 °. When the angle shift from the optical axis direction becomes large in this way, it affects the polarization separation function of the polarization beam splitter. That is, the angle of incidence of the S wave on the polarization beam splitter changes. Then, since the film thickness of the multilayer film is optimized in the optical axis direction, the film thickness of each layer deviates from the optimum value. As a result, the reflectance of the S-wave decreases.

[0008] The black portion of the display image on the light bulb is reflected as it is as the S wave and further reflected by the polarization beam splitter, and does not enter the projection optical system to be displayed on the screen in black. However, for a light beam deviated from the optical axis direction, there is a component that transmits the S wave instead of being completely zero. For this reason, the light reaches the portion where black display is originally performed, and the floating of black is increased. That is, a problem that the contrast of the image is reduced occurs.

The present invention solves the above-mentioned problems of the prior art,
Provided is a polarization illuminating device and a method of manufacturing the same in which there is no decrease in contrast for a combination of a high-brightness projection optical system having a small F value in a projection type projector using a reflection type light bulb having a high light use efficiency even at a high resolution. The purpose is to do.

[0010]

In order to achieve the above object, a polarized light illuminating apparatus according to the present invention comprises a light source, a diffractive optical element having a refractive index anisotropy, a reflective light bulb, and an optical element on the light bulb. At least a projection optical system for enlarging and projecting an image, wherein the diffractive optical element has a periodic structure including liquid crystals arranged uniformly, reflects a P-wave component from the light source, and generates an S-wave component. The P-wave component of the light wave incident on the light bulb and reflected on the light bulb is guided to a projection optical system.

A polarized light illuminating apparatus according to the present invention comprises at least a light source, a diffractive optical element having refractive index anisotropy, a reflective light bulb, and a projection optical system for enlarging and projecting an optical image on the light bulb. The diffractive optical element has a periodic structure including liquid crystals uniformly arranged, reflects a P-wave component from the light source, enters an S-wave component into the light bulb, and reflects it on the light bulb. The light wave from the light source is guided to a projection optical system, and the light beam from the light source is divided into three light beams having different wavelengths substantially corresponding to R (red), G (green), and B (blue). It is characterized in that a diffractive optical element which separates the light into light beams and has a periodic structure of different switches for the light beams having different wavelengths is combined.

In the above structure, the diffractive optical element has a periodic structure formed by using a liquid crystal having a refractive index anisotropy, and a polarization component (P wave or S wave) of incident light in one direction.
Wave) produces a refractive index distribution corresponding to the periodic structure,
It is desirable to have a function of causing light diffraction due to this refractive index difference and preferentially proceeding straight ahead with respect to a component (S wave or P wave) substantially orthogonal to the incident light.

In the above structure, it is desirable that the periodic structure of the diffractive optical element is formed by the inclination of the optical axis of the liquid crystal having the refractive index anisotropy.

The method for manufacturing a polarized light illuminating device according to the present invention is directed to a diffractive optical element used in a polarized light illuminating device having a structure in which an optical medium containing a liquid crystal and a polymer is sealed in a region sandwiched between transparent insulating substrates. Producing an interference fringe consisting of a bright portion and a dark portion corresponding to a periodic intensity distribution formed by two-beam interference of a laser beam on the optical medium, the region belonging to the bright portion of the interference fringe. The liquid crystal molecules begin to cure at an early stage, and the liquid crystal molecules are oriented with a substantially uniform inclination with respect to the cured polymer layer in the first initial step of forming a periodic structure independent of the polarization component. The periodic structure is completed through a second step of forming the periodic structure so as to diffract only the wave component.

In the above structure, it is preferable that the optical medium contains a photopolymerization initiator and a dye for absorbing the wavelength of laser light.

Further, in the manufacturing method of the polarized light illuminating device according to the present invention, a thin film which has been subjected to an alignment treatment made of a polymer is formed on a transparent insulating substrate, and a light or thermosetting liquid crystal layer is formed on the thin film. A first step of uniformly curing and then curing, and after forming a polymer thin film on the liquid crystal layer, a light or thermosetting liquid crystal layer is formed in a direction substantially orthogonal to the liquid crystal molecule direction of the liquid crystal layer. And a second step of forming
And a second step are continuously and repeatedly performed to form a periodic structure having refractive index anisotropy.

Further, in the manufacturing method of the polarized light illuminating device according to the present invention, a thin film which has been subjected to an alignment treatment made of a polymer is formed on a transparent insulating substrate, and a light or thermosetting liquid crystal layer is formed on the thin film. After uniformly aligning, a manufacturing method of forming a periodic structure by repeating the curing step a plurality of times, wherein the ordinary light refractive index of the liquid crystal layer is approximately equal and the extraordinary light refractive index is alternately laminated with different liquid crystal layers. To form a periodic structure.

In the above-mentioned structure, the diffractive optical element is constituted to include liquid crystals arranged uniformly, and a photopolymerizable monomer or a photo-crosslinkable liquid crystal polymer is added.
It is desirable that the direction of the molecular axis of the liquid crystal be fixed with respect to the irradiation of light in the ultraviolet region.

In the above structure, it is preferable that the step of curing the liquid crystal is performed in an inert gas atmosphere.

[0020]

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

(Embodiment 1) FIG. 1 schematically shows a polarization illuminating apparatus for a projection type projector using a diffractive optical element constituted in Embodiment 1 of the present invention. As the light source 101, a fluorescent lamp, a xenon lamp, a metal halide lamp, a mercury lamp, an LED, an FED, a laser beam, an inorganic or organic EL element, or the like can be used. Light from the light source 101 is emitted as substantially parallel light by a reflector of the light source, and has a polarization direction in a direction parallel to the plane of the paper (defined as a P wave 105 here) and a polarization direction in a direction perpendicular to the plane of the paper. It is configured to include light (defined here as S wave 106).

When these lights are incident on the diffractive optical element 102, the following effects occur. The diffractive optical element 102 is formed using an optical medium having refractive index anisotropy, and has a thickness of about 10 μm, so that the refractive index distribution is periodically distributed also in the thickness direction. For this reason, the diffractive action differs depending on the polarization direction, and the diffractive action has a characteristic of exhibiting high diffraction efficiency in one direction.

Of the light incident on the diffractive optical element 102, P
Since the wave 105 acts as an extraordinary light component, the wave 105 is modulated by the refractive index distribution of the periodic structure formed in the element, and is emitted with its traveling direction bent below the plane of the diffractive optical element 102 shown in FIG. For this reason, almost no light enters the light valve 103.

On the other hand, since the S-wave 106 acts on the diffractive optical element 102 as an ordinary light component, the S-wave 106 is not affected by the refractive index distribution having a periodic structure, but isotropically uniform in the refractive index. Exhibit the same characteristics as when passing through a medium. For this reason, the S wave 106 passes through the diffractive optical element 102 as it is. Therefore, the diffractive optical element 10
After passing through the light 2, only the S wave 106 having the same polarization direction is incident on the light valve 103.

Here, as the light valve 103, a twisted nematic liquid crystal or a VA mode liquid crystal element of a homeotropic type can be used. S-wave 1 incident on Light Hall
06 is reflected by the light bulb, and becomes a light wave in which a P wave and an S wave are mixed corresponding to the display screen. Pixels corresponding to black on the display screen are not subjected to light modulation and are reflected as S-waves. At white or intermediate brightness, light is modulated according to the applied electric field to become light waves containing P-wave components. Out.

That is, after passing through the liquid crystal element, the polarization direction of light differs depending on the presence or absence of the electric field of the pixel corresponding to the passing position. These lights enter the diffractive optical element 102 again. Here, as described above, the component of the S wave 106 passes through the diffractive optical element 102 as it is, and the P wave 105
Is reflected by the diffractive optical element 102, guided to the projection lens 104, expanded by this lens, and projected on the screen. Here, the twist nematic liquid crystal VA mode liquid crystal has been described as an example. However, as the light bulb 103, a ferroelectric liquid crystal or an antiferroelectric liquid crystal in which the direction of arrangement of liquid crystal molecules differs depending on the polarity of an electric field can be used.

Next, the operation when a light wave enters the diffractive optical element 102 of the present invention will be described in detail with reference to FIG. FIG. 2 is a cross-sectional view of the internal configuration of the diffractive optical element 102. The diffractive optical element 102 is made of an optical medium having a refractive index anisotropy.

The inside of the device has a periodic layer structure in the thickness direction from the surface on which light enters. Then, the inclination of the optical axis of the optical medium having the refractive index anisotropy between adjacent layers is arranged such that one is parallel to the surface of the diffractive optical element 102 and the other is with respect to the surface. They are arranged vertically.

Now, consider a case where light is incident on an optical medium having refractive index anisotropy. When light whose polarization direction is parallel to the optical axis of the optical medium is incident, the light becomes an extraordinary ray, and thus the refractive index indicates a value of Ne. Further, when the polarization direction is perpendicular to the optical axis of the optical medium, it becomes an ordinary ray and shows a refractive index of No. Here, Ne> No.

Next, in the diffractive optical element 102 shown in FIG. 2, light having a polarization direction perpendicular to the paper surface is defined as an ordinary ray S-wave 106, and light having a polarization direction parallel to the paper surface is regarded as an extraordinary ray P. The behavior when these lights enter the diffractive optical element 102 as the wave 105 will be considered. First, when an ordinary ray is incident, the polarization direction is perpendicular to the optical axis of the optical medium constituting each layer in any case. For this reason, the refractive index of each layer is No, regardless of the direction of the optical axis between the layers. That is, since a medium having a uniform refractive index of No is present, the ordinary ray incident on the medium is not affected by diffraction and is transmitted as it is as shown in FIG.

Next, a case where an extraordinary ray is incident will be considered. In a layer in which the optical axis of the optical medium having the refractive index anisotropy is arranged parallel to the incident surface, the polarization direction of the incident light is parallel to the optical axis. This corresponds to the case where the light passes through a layer having a refractive index of Ne.

For a layer in which the optical axis of the optical medium is perpendicular to the incident surface of the diffractive optical element 102, this corresponds to the case where the polarization direction is perpendicular to the optical axis. Treated as having a rate.

Therefore, the diffractive optical element 102 for an extraordinary ray passes through a plurality of layers having different refractive indexes periodically in the thickness direction which is the traveling direction of the incident light. As a result, the incident light beam is subjected to a so-called Bragg diffraction effect, in which the light is focused in a specific direction corresponding to the periodic switch of this layer. As shown in FIG. 2, the extraordinary ray is reflected by the layer structure formed inside the element of the diffractive optical element 102 and changes its optical path to the upper right of the paper.

By having a structure having a periodic structure in the thickness direction as shown in FIG. 2, the Bragg diffraction condition is applied. This is because when light having a certain wavelength enters each layer forming the periodic structure, the light scattered in each layer causes a phenomenon in which the scattered component strengthens in a specific direction corresponding to the wavelength, the incident angle, and the switch between the layers. . This is what is called Bragg's diffraction condition. Such a condition results in a three-dimensional configuration for a conventional two-dimensional diffractive optical element, and the effect of blazing (focusing light in one direction) is obtained. Will have.

Therefore, the diffraction efficiency can be dramatically improved as compared with the conventional diffractive optical element, and theoretically 100%
Efficiency is possible.

The calculation result of such a theoretical diffraction efficiency is described in H.-J. Kogelnik, (BellSys. Tec.)
h. J. , 48, 1969, p. 2909-294
It is disclosed in the analysis of 7).

In the structure shown in FIG. 2, the layer in which the molecules are perpendicular to the plane of incidence can be replaced by a polymer medium having a refractive index of about 1.5 instead of liquid crystal.

(Embodiment 2) FIG. 3 shows an example of a projection type display device capable of displaying images in color provided with a color separation and color synthesis system. This is applied to a reflection type light valve.

The portion indicated by (a) in the figure shows a color separation system that separates light from the light source on the second floor into light of each wavelength of R (red), G (green), and B (blue). . (B) shows a color synthesis system in which light of each wavelength guided from the color separation system of the second floor portion passes through the light valve and then performs color synthesis again.
Located on the floor. The second-floor part and the first-floor part shown in (a) and (b) are vertically overlapped to constitute a projection display device.

The reflection type system will be described in more detail. The light beam emitted from the light source 101 passes through an integrator 301 composed of a first lens group and a second lens group, and enters the dichroic prism 303 while maintaining the uniformity of the light beam in the plane.

The dichroic prism 303 has a configuration in which a wavelength filter for each band is formed inside. For this reason, the white light from the light source is decomposed into light corresponding to each of the three primary colors R, G and B corresponding to the wavelength filter. Then, for example, R, G, and B lights are respectively decomposed and emitted in directions indicated by arrows in the drawing. This has the same function as the three-piece dichroic mirror, but because of the prism configuration, it is possible to separate colors without using a large space, so that a compact system can be configured. It is also possible to use a dichroic mirror having substantially the same configuration as the dichroic prism.

Next, the light emitted in the three directions is reflected by the total reflection mirrors 305 to 307 and guided to the lower first floor. Then, these three lights are incident on the diffractive optical elements 308 to 310, and the S-polarized light component is transmitted as it is and is incident on the reflection type light valves 311 to 313. Here, for the sake of simplicity, the light bulb is displayed in the horizontal direction of the polarization beam splitter, but actually, the polarization beam splitters 308 to 3 are actually displayed.
It is placed on the back side of the paper. Reflective light bulbs 311-3
The light wave reflected by 13 re-enters the polarization beam splitter,
The P-wave component is reflected and enters the dichroic stream 304.

The dichroic frame 304 has a function opposite to that of the dichroic frame 303, and performs color synthesis of the R, G, and B divided light components, and performs color synthesis in the direction of the projection lens 104. It is emitted as light traveling in the direction. The light after passing through the projection lens # 104 is displayed as an enlarged image on the screen 302.

As shown in FIG. 3, the diffractive optical elements 308 to 3
Numeral 10 is applied to each light wave that has been separated into R, G, and B wavelengths by a dichroic stream 303.
Therefore, as described in the first embodiment, it is necessary to enhance the effect of diffraction for each light wave. For this purpose, it is preferable to use three diffractive optical elements each having a periodic switch optimized for each wavelength.

As will be described in detail in a later manufacturing method, R,
The diffraction optical element 308 is formed by forming the periodic structure switch of the refractive index distribution to be smaller as the wavelength becomes shorter as G and B.
３１０310 can be optimized for diffraction efficiency. In fact, even in the system shown in FIG.
In each of Examples No. to No. 310, a different periodic structure was used.

(Embodiment 3) Next, a manufacturing process of the diffractive optical element of the present invention will be described with reference to FIG. First, as a light source for exposing the interference fringes, for example, outgoing light having a wavelength of about 515 nm from an Ar laser can be used. The diameter is 30 mm to 50 mm using a beam expander or the like.
After the beam is spread to a beam of about mm, the beam is split in two directions by a beam splitter or the like, and a structure of an interference fringe to be irradiated on the diffractive optical element is formed by combining the mirror and the like.

Next, a manufacturing process of the diffractive optical element will be described. After washing the glass substrate to remove the dust, an optical medium in which a liquid crystal and a polymer are mixed is dropped on the glass substrate with a stapler or the like, and another glass substrate is adhered onto the glass substrate from above, and two glass substrates are laminated from above. A cell in which an optical medium was sealed in a gap between glass substrates was manufactured.

The optical medium is a nematic liquid crystal, and the polymer material is a mixture of a monomer and an oligomer. Specifically, Ph
enylglycidil ether acrylate hexamethylene diisocya
nateurethane prepolymer, 2-Hydroxyethyl Methacrylat
e, Dimethylol tricyclodecane diacrylate and the like can be used. Although the liquid crystal used this time has a positive dielectric anisotropy, it is also possible to use a liquid crystal having a negative dielectric anisotropy. N-Phenylglycine may be added as a photopolymerization initiator, and Dibromofluoresceine or the like may be added as a dye for absorbing light having a laser wavelength around 515 nm. Further, in order to maintain the uniformity of the cell cap, a paste having a diameter of about 10 μm may be added.

The liquid crystal sample prepared as described above was exposed to interference fringes using the above-described Ar laser. First, the diffractive optical element 102 was set at the position where the optical system was manufactured. The exposure time was adjusted by a shutter. The mirror was adjusted so that interference fringes of about 1 μm pitch were formed at the sample position. The irradiation intensity of the Ar laser at this time was about 50 mW to 100 mW.

Here, the relationship between the pitch of the interference fringes formed at the sample position and the wavelength of the laser will be considered. The pitch of the interference fringes formed on the sample becomes smaller as the intersection angle of the two light beams becomes larger and as the laser wavelength becomes shorter. This can be represented by the following equation:

(Equation 2) Pitch: P = λ / 2 sin θ; λ Racer ゛ wavelength, θ intersection angle Therefore, as described in the second embodiment, in order to enhance the effect of diffraction for R, G, and B light. As the wavelength becomes shorter, it is necessary to make the periodic structure smaller in correspondence with the time when the periodic structure is formed by the laser.

Next, the process of forming interference fringes on the liquid crystal sample by the laser will be described in detail.

First, the liquid crystal sample is set with the shutter closed and no light irradiation. Then, the shutter is opened for a predetermined time, here about 5 minutes, and then closed.
As shown in FIG. 4, as a result of this process, as an initial stage, the liquid crystal sample starts to cure the polymer material in a region belonging to a bright portion where the intensity of interference fringes formed by interference of two light beams of the laser. In this process, periodic polymer columns are formed. At the same time, the liquid crystal material is extruded from the cured polymer region because the curing reaction does not occur due to the laser exposure, and gathers in the dark region where the laser intensity is low. That is, a phase separation phenomenon occurs in which a periodic density distribution between the polymer and the liquid crystal occurs. This is the first step.

In the next second step, the liquid crystal molecules gathered in the dark part are macroscopically aligned in the direction in which the molecules stand as shown in FIG. Therefore, a layer in which liquid crystal molecules are arranged and a layer having a high polymer density are alternately and periodically formed. The refractive index of the polymer is generally about 1.5, which is almost equal to the ordinary light refractive index No of the nematic liquid crystal that is often used. Therefore, the refractive index of the liquid crystal is No for the ordinary ray of the incident light, and the refractive index of the polymer portion is also about No.

At this time, since the diffractive optical element is regarded as an isotropic medium, the incident light passes therethrough. This corresponds to the case where the S-wave 106 of FIG. 2 is incident.

On the other hand, with respect to extraordinary rays, the refractive index of the liquid crystal becomes Ne because the liquid crystal molecules are arranged in a direction perpendicular to the polymer layer, and the polymer layer has a refractive index anisotropy. No, it remains No. Therefore, a periodic structure having different refractive indices between the liquid crystal layer and the polymer layer is generated. Since this is the same as the case where the P-wave 105 described in FIG. 2 is incident, the extraordinary ray is diffracted in a specific direction corresponding to this refractive index distribution.

In FIG. 4, for the sake of simplicity, a description has been given of a diagram in which periodic structures are arranged in the horizontal direction. However, since the intensity distribution of the laser beam can be distributed in the thickness direction of the cell, as shown in FIG. It is also possible to make a pattern in which a periodic structure is formed in a vertical direction.

FIG. 5 explains in detail the time course of the first and second steps. This is because the observation of the formation process of the periodic structure during the interference exposure of the laser shown in FIG.
A 3 nm He-Ne laser is incident on a liquid crystal sample as monitor light, and shows the temporal change of the diffraction intensity. Since the laser light of this wavelength has a low light intensity and is out of the absorption band of the liquid crystal sample, it does not affect the grating formation.

FIG. 5A shows a case where an S-polarized light wave is incident by a polarizer, and FIG. 5B shows a case where a P-polarized light is incident. As can be seen from these figures, the change in the diffraction intensity is large and has two stages. That is,
There is a portion where the increase in diffraction intensity with time is small and hardly depends on the incident polarization direction, and a portion where the diffraction intensity sharply increases only for the incident P wave.

Since the value of the diffraction intensity is considered to correspond to the process of forming the periodic structure in the liquid crystal sample, the internal formation process can be inferred from the temporal change of the diffraction intensity. In other words, the first diffraction intensity at which the initial diffraction intensity gradually increases
Is a process in which the polymer is cured to form columns as shown in FIG. 4 and a density distribution of the liquid crystal and the polymer is generated. In this process, a density distribution between the polymer and the liquid crystal is formed,
In a portion where the density of the liquid crystal is high, the average value is higher on average than in the polymer layer, a periodic refractive index distribution is generated, and a phenomenon of diffraction occurs. At this stage, the orientation of the liquid crystal has not been formed, so that there is no dependence on the incident polarization direction.

Next, in the second step, a phenomenon occurs in which the liquid crystals are arranged in a region where the density of the liquid crystals is high with respect to the columns of the cured polymer. Therefore, in this case, it is considered that the incident polarization component has a strong diffraction dependency on the P wave, and this process occurs steeply, so that the temporal diffraction intensity increases.

The above two processes occurred without change even when the laser light intensity at the time of exposure was changed or when the amount of the photopolymerization initiator or dye to be added was changed.

The liquid crystal sample exposed to the interference fringes was irradiated with a substantially uniform light of mercury lamp for about 5 minutes so that the uncured portion of the entire sample was stably cured, thereby completing the sample. During the laser exposure of the liquid crystal sample, the temperature was raised to about 60 ° to lower the viscosity of the optical medium so that a good density distribution was formed.

FIG. 6 shows the evaluation results of the optical characteristics of the sample manufactured here. Green laser light having a wavelength of 544 nm was incident on this sample, and the diffraction efficiency was examined by changing the incident angle.
In the result, the S1 order is a component that does not transmit through the diffractive optical element and diffracts. The P1 order is a component diffracted by the diffractive optical element and used as reflected light. That is, the P1 / S1 ratio corresponds to the contrast on the screen, and the larger this value is, the more preferable it is when used in a polarized light illumination device.

This angle dependency is shown up to ± 10 ° at both ends, which corresponds to the case where a lens having an F of about 3.0 is used as the gap from the optical axis as described in the first embodiment. As can be seen from FIG. 6, the intensity of the P1 order decreases due to an angle change. Further, the value of the S1 order does not increase with the change in the angle, but decreases, and conversely, there is no phenomenon that the value rises with respect to the angle variation. As can be seen from (b), it can be seen that the contrast remains substantially constant with respect to the change in the angle.

When the manufactured diffractive optical element is used in the configuration shown in FIG. 1, even if the lens has a small F value, the S wave 10
6 is incident on the projection lens 104 at a low rate. Therefore, it has been found that a polarized light illuminating device with less decrease in contrast can be provided.

Further, in FIG. 1, the S wave 1 of the light wave from the light source is shown.
06 is incident on the light valve 103.
Since the transmitted wave of the S wave enters the light valve 103 without being diffracted into the diffractive optical element at a high order, the light use efficiency can be set high. In FIG. 6, the diffraction efficiency of the P1 order decreases as the angle increases, which leads to a decrease in the brightness of the white level. However, it can be improved by increasing Δn of the liquid crystal sample. Since the value of Δn of the liquid crystal used as the optical medium can be selected widely,
In the future, a diffractive optical element with higher P1 order diffraction efficiency and reduced angle dependence can be manufactured by the method shown here.
It is believed that an excellent polarized lighting device can be provided.

(Embodiment 4) Referring to FIG. 7, a UV-curable liquid crystal is used to form a periodic structure by spin coating.
A process for manufacturing a diffractive optical element having refractive index anisotropy will be described.

A glass substrate is prepared, and the substrate is washed to remove the dust. Then, an alignment film made of a polymer, for example, polyimide is applied by a spin coating method or the like, and the alignment film is formed by heat treatment. Formed on a substrate. Thereafter, a laser cracking process was performed in a specific direction using a roller or the like.

Next, this glass substrate was used as a scanner 701 in FIG.
Set ink on top. A UV curable liquid crystal containing a photopolymerizable liquid crystal monomer or a photo-crosslinkable liquid crystal polymer was coated on this glass substrate by spin coating. 1000 to 1000
It is about 10,000. The coating film was irradiated with UV light to be cured while the liquid crystal molecules were arranged in parallel with the substrate.
This curing process was performed in an inert gas atmosphere such as nitrogen so as not to be inhibited by oxygen in the atmosphere.

Thereafter, a vertical alignment film for vertically setting the liquid crystal molecules with respect to the substrate was formed on the cured liquid crystal. Then, in the same manner as above, the setting is performed again on the scanner 701 and the UV is applied.
A curable liquid crystal was similarly applied and cured. In addition, prior to continuous formation, only one layer of horizontal alignment and vertical alignment is formed on another glass substrate in advance, and a cross-Nicol polarizing plate is used to confirm that the UV-curable liquid crystal is horizontally or vertically aligned. It was confirmed by placing a sample underneath and observing with a microscope.

Next, by repeating the above steps continuously as shown in the right diagram of FIG. 7, a multilayer structure was formed in which liquid crystal molecules were alternately arranged horizontally and vertically with respect to the substrate. . Through this process, a diffractive optical element similar to that shown in FIG. 2 was completed. As described in the first embodiment, when the S wave 106 enters this diffractive optical element, it is regarded as an isotropic medium and is transmitted as it is, and the P wave 105 is reflected by a periodic refractive index distribution. Will be.

Actually, when the diffraction efficiency was evaluated by the same method as shown in FIG. 6, the S-wave was substantially transmitted, only the P-wave component was reflected, and a multilayer structure in which the orientation directions of the liquid crystal molecules were different was formed. It was confirmed that.

Further, although the P1 order decreased with respect to the angle change, the S1 order did not increase and the contrast did not change with the angle change. Therefore, it was found that the present invention can be applied to a lens having a small F-number when used in the system as shown in FIG.

(Embodiment 5) Next, in the case of laminating UV-curable liquid crystals by spin coating in the same manner as in Embodiment 4, this time, instead of alternately laminating the liquid crystal molecules in the horizontal direction and the vertical direction, It was oriented in one direction only in the horizontal direction.
At this time, application of the first layer of liquid crystal was performed in the same manner as in Embodiment 4.

Next, as the type of liquid crystal in the second layer, a liquid crystal having an ordinary light refractive index of about 1.5 and the same, but an extraordinary light refractive index of about 0.1 was used. Specifically, the liquid crystal of the first layer is (N
o: 1.48, Ne: 1.55) The liquid crystal of the second layer is (N
o: 1.48, Ne: 1.65).

As described above, since the alignment directions of the liquid crystal can be equalized in the first layer and the second layer, one type of alignment film can be used, and the periodic structure can be designed more simply than the case where different alignments are alternately performed. Becomes Furthermore, by applying a liquid crystal to the alignment film that has been subjected to the first lamination and defining the alignment direction, it is possible to control the alignment direction of the second and subsequent layers to a certain extent. There is also a possibility that the formation can be omitted, and a simpler and more reliable manufacturing method can be provided as compared with the fourth embodiment.

FIG. 8 is a schematic view of the diffractive optical element 102 completed by the above steps. The liquid crystal of the first layer and the liquid crystal of the second layer are oriented in the same direction and have different refractive indexes for extraordinary light. Now, consider the case where a light wave is incident on this element as shown in FIG. The first layer and the second layer
Since the ordinary refractive index of the liquid crystal in the layer is equal to 1.48, it is regarded as an isotropic medium and passes straight through as it is without being affected by diffraction.

Next, when the P-wave 105 enters, the first
The extraordinary light refractive index of the liquid crystal of the layer is 1.55, and the extraordinary light refractive index of the second layer is 1.65, which results in a difference of 0.1 in refractive index. For this reason, the P-wave 105 receives a diffraction effect due to the periodic structure in which these liquid crystal layers are alternately stacked, and is emitted in the direction of reflection on the substrate as shown in FIG.

The diffraction efficiency of this diffractive optical element was evaluated in the same manner as in the fourth embodiment. As a result, the S wave was transmitted and the P wave was reflected. Regarding the angle dependence of the incident direction, the S-wave was reduced as the incident angle was changed, and the angle dependence of the contrast was hardly observed.
Therefore, it has been found that by using the diffractive optical element manufactured here in the system shown in FIG. 1, it can be applied to a lens having a small F value without lowering the contrast.

As described above, in the present invention, a structure and a manufacturing method when a diffractive optical element is manufactured using an optical medium having a refractive index anisotropy and applied to a polarized light illumination device have been described.

As the optical medium having the refractive index anisotropy,
Lithium niobate, KD ₂ PO ₄ , β-BaB ₂ O ₄ , PL
It is also possible to use a uniaxial crystal having an electro-optical effect such as ZT, and to obtain an effect by using a medium having a refractive index anisotropy including a biaxial optical crystal such as KTiPO _4. It is also possible to demonstrate.

[0083]

As described above, according to the present invention, a diffractive optical element having a three-dimensional layer structure is manufactured using an optical medium having a refractive index anisotropy, and this is applied to a polarized light illumination device. And a manufacturing method thereof. By using an optical medium having a refractive index anisotropy, a specific polarization component is transmitted, and a polarization component orthogonal to the specific polarization component has selectivity according to a polarization direction such as diffraction.

Further, the S-wave component corresponding to the black level of the light bulb decreases as the incident angle deviates from the optical axis direction.
For this reason, the floating of the black level does not occur even for light off the optical axis. Therefore, the present invention can be applied to a lens having a large F-number capturing angle. If this diffractive optical element is used together with a reflective light bulb and a projection lens having a small F-number to form a projection type projector, a system with higher resolution and higher brightness can be provided, which has great value.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of a projection display device using a diffractive optical element of the present invention.

FIG. 2 is a cross-sectional view illustrating an example of an internal configuration of the diffractive optical element.

FIG. 3 is a configuration diagram of an embodiment of a color-compatible projection display device using the diffractive optical element of the present invention.

FIG. 4 is a diagram showing an example of a process of manufacturing a diffractive optical element according to the present invention.

FIG. 5 is a diagram showing an example of a temporal change in the process of manufacturing the diffractive optical element of the present invention.

FIGS. 6A and 6B are diagrams showing an example of evaluation results of the diffractive optical element of the present invention.

FIG. 7 is a configuration diagram of an embodiment of a method for manufacturing a diffractive optical element according to the present invention.

FIG. 8 is a sectional view showing an example of the internal configuration of the diffractive optical element.

[Explanation of symbols]

 Reference Signs List 101 light source 102 diffractive optical element 103 light bulb 104 projection lens 105 P-wave 106 S-wave 301 integrator 302 screen 303, 304 dichroic prism 305-307 total reflection mirror 308-310 diffractive optical element 311-313 reflective light bulb 401 glass substrate 701 Swiener 702 Orientation film

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Yukio Tanaka 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Akio Takimoto 1006 Odaka Kadoma Kadoma City, Osaka Matsushita Electric Industrial F Term (Reference) 2H091 FA05X FA10X FA14X FA14Z FA19X FA26X FA41X FA41Z FB06 FB12 FB13 FC01 FC23 FD06 GA06 LA03 LA17 MA07 2H099 AA12 BA17 CA17 5C060 BA03 BA08 BC05 DA00 DA05 EA00 GA01 GB02 GB06 HC00 HC20 ACOB BB06 JCO DD05 FF05 GG01 GG03 GG08 GG28 GG46 LL15

Claims (10)

[Claims] 1. A light source, a diffractive optical element having refractive index anisotropy, a reflective light valve, and a projection optical system for enlarging and projecting an optical image on the light valve, wherein the diffractive optical element is uniform. A periodic structure including the liquid crystal arranged in the light source is formed, the P-wave component from the light source is reflected, the S-wave component is incident on the light bulb, and the P of the light wave reflected on the light bulb is reflected.
A polarized light illumination device configured to guide a wave component to a projection optical system. 2. A light source, a diffractive optical element having refractive index anisotropy, a reflective light bulb, and a projection optical system for enlarging and projecting an optical image on the light bulb, wherein the diffractive optical element is uniform. A periodic structure including the liquid crystal arranged in the light source is formed, the P-wave component from the light source is reflected, the S-wave component is incident on the light bulb, and the P of the light wave reflected on the light bulb is reflected.
What is claimed is: 1. A polarization illuminating device comprising: a light source configured to guide a wave component to a projection optical system, wherein a light beam from the light source substantially corresponds to R (red), G (green), and B (blue). A polarization illuminating apparatus, comprising: performing color separation into three light beams having different wavelengths; and combining a diffractive optical element having a periodic structure of different switches with respect to the light beams having different wavelengths. 3. The diffractive optical element has a periodic structure formed by using a liquid crystal having a refractive index anisotropy, and the periodic structure is not affected by a polarization component (P wave or S wave) of incident light in one direction. And a component (S) that causes diffraction of light and is substantially orthogonal to the incident light.
3. The polarized light illuminating device according to claim 1, wherein the polarized light illuminating device has a function of traveling straight ahead with respect to a wave or a P wave. 4. The polarized light illuminator according to claim 3, wherein the periodic structure of the diffractive optical element is formed by tilting the optical axis of a liquid crystal having a refractive index anisotropy. 5. A method for manufacturing a diffractive optical element used in a polarized light illuminating device having a structure in which an optical medium containing a liquid crystal and a polymer is sealed in a region sandwiched between transparent insulating substrates, the method comprising: Then, an interference fringe consisting of a bright portion and a dark portion corresponding to the periodic intensity distribution formed by the two-beam interference of the laser beam is generated. The first initial step of forming a periodic structure independent of the wave component, and the periodic structure is arranged such that the liquid crystal molecules are aligned with a substantially uniform inclination with respect to the cured polymer layer and diffract only the P-wave component. A method for manufacturing a diffractive optical element used in a polarized light illumination device, wherein a periodic structure is completed through a second step to be formed. 6. The method according to claim 5, wherein the optical medium contains a photopolymerization initiator and a dye for absorbing the wavelength of the laser light. 7. A first method comprising: forming a thin film on a transparent insulating substrate which has been subjected to an alignment treatment comprising a polymer; and uniformly orienting a light or thermosetting liquid crystal layer on the thin film, followed by curing. And a second step of forming a polymer thin film on the liquid crystal layer and then forming a light or thermosetting liquid crystal layer in a direction substantially perpendicular to the liquid crystal molecule direction of the liquid crystal layer. A method of manufacturing a diffractive optical element for use in a polarized light illumination device, wherein a periodic structure having refractive index anisotropy is formed by repeatedly performing the first and second steps a plurality of times. 8. A step of forming a polymer-oriented thin film on a transparent insulating substrate, uniformly orienting a light or thermosetting liquid crystal layer on the thin film, and then curing the liquid or thermosetting liquid crystal layer. Is repeated a plurality of times to form a periodic structure, wherein the periodic structure is formed by alternately stacking liquid crystal layers having substantially the same ordinary light refractive index as the liquid crystal layer and different extraordinary light refractive indexes. A method for manufacturing a diffractive optical element used in a polarized light illumination device. 9. The diffractive optical element is constituted by including liquid crystals arranged uniformly, and a photopolymerizable monomer or a photocrosslinkable liquid crystal polymer is added to the diffractive optical element. 9. The method according to claim 7, wherein the direction is fixed. 10. The method according to claim 7, wherein the step of curing the liquid crystal is performed in an inert gas atmosphere.
3. The method for manufacturing a polarized light illumination device according to item 1.