JP2001318229A - Polarization converting element and projection-type display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarization converting element with polarization separating performance at a low cost by overcoming shortcomings of an expensive manufacturing cost of a prism type polarization separating element as a whole, which has superior polarization separating performance, however, necessitates many steps for working of two triangular prisms comprising the polarization separating element. SOLUTION: The polarization converting element is used for an illuminating optical system of a projection-type display device and comprises an optically anisotropic polymer film 22, having different refractive indexes between in the vertical direction and in the horizontal direction with respect to the plane of incidence, an adhesive 23 and an optical block 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a polarization conversion element used for an illumination optical system of a projection display apparatus and a projection display apparatus using the polarization conversion element.

[0002]

2. Description of the Related Art In recent years, with the spread of multimedia devices and personal computers, the demand for large-sized display devices has increased more than before. For example, a liquid crystal projector including a light modulation unit such as a liquid crystal panel and optical components such as a light source and a projection lens has been widely used as a television receiver or a display device for presentation using a personal computer.

FIG. 11 shows an example of a large display device.
1 shows a typical configuration example of an optical unit 1 which is a three-panel type liquid crystal projector. The light emitted from the light source 2 such as a metal halide lamp or a halogen lamp selectively cuts and transmits only the light in the visible light region and cuts off the unnecessary ultraviolet and infrared light. After passing through the filter 3, the light from a light beam that is non-polarized light enters a polarization conversion element 4 that converts the light into polarized light polarized in a specific direction, and becomes linearly polarized light.
LA) makes the light intensity distribution uniform. Thereafter, the light is separated into red, green, and blue by the dichroic mirror 6. After being incident on the liquid crystal light valve 7 corresponding to each color and modulated, the light is combined again by the dichroic prism 8, and this combined light is projected on the screen 10 by the projection lens 9.

[0004] Liquid crystal projectors can be roughly classified as shown in FIG.
FIG. 12A shows a front projection type projector in which the optical unit 1 and the screen 10 are separate bodies, and FIG.
There is a rear projection display device in which the optical unit 1 and the screen 10 are integrally arranged in a cabinet 11 shown in FIG.

FIG. 13 is a partial sectional view of a typical liquid crystal light valve. The liquid crystal light valve 7 used in the optical unit 1 comprises two polarizing plates 15a and 15b and a liquid crystal panel 16. . The liquid crystal panel 16 can use only linearly polarized light whose light oscillation direction is constant due to its driving principle. Therefore, more than half of the energy of the light beam emitted from the light source 2 is absorbed by the incident-side polarizing plate 15a, and only the light beam of which the vibration direction of the remaining light is constant is incident on the liquid crystal panel 16, and the light beam whose vibration direction is fixed. Only emitted.

With an increase in the size of the display device, a light source having a larger output has been used in order to secure the brightness of the image. In the above-described method for obtaining polarized light, half of the incident light is absorbed by the incident-side polarizing plate 15a, so that the temperature of the incident-side polarizing plate 15a rises more than necessary, and the optical characteristics of the polarizing plate deteriorate. There has been a problem that it cannot be used due to heat deformation or thermal deformation. Further, since about half of the light emitted from the light source 2 is absorbed by the polarizing plate 15a, the problem that the light use efficiency is very poor has also been highlighted.

FIG. 14 shows an example of a projection display device for avoiding this problem. FIG. 14 is a sectional view of a projection type display device using a prism type or plate type polarization conversion element. In this projection type display device, a polarization conversion element 4 is provided between a light source 2 and a liquid crystal light valve 7 so that a desired linearly polarized light is obtained in advance, and then light is incident on a liquid crystal panel. Optical systems have been proposed that minimize absorption and increase light use efficiency.

As shown in FIG. 14, the polarization conversion element 4 is of a prism type or a plate type.
No. 7 and the latter are described in detail in JP-A-6-250120.

FIG. 14A is a diagram for explaining the function of the prism type polarization conversion element 17. The prism type polarization separation element is a triangular prism 1 composed of two transparent optical members.
7a, and a polarization separation film 17b is formed on the bonding surface. The light emitted from the light source 2 is incident on the prism-type polarization separation element 17, and the negative linear polarization light (S-polarized light) is reflected by the polarization separation film 17 b, while the other linear polarization light (P-polarized light) is To Penetrate. After the reflected S-polarized light is aligned in the direction of the light by a reflection mirror 18 or the like, the polarization direction is converted by a half-wave plate (phase difference plate) 19 to be P-polarized light, and the projection shown in FIG. S-polarized light, which has been wasted in the apparatus, is also effectively used.

FIG. 14B is a diagram for explaining the function of the plate-type polarization splitting element. The plate-type polarization separation element is constituted by a glass plate 20 coated with a dichroic polymer film such as polyvinyl alcohol, and is usually arranged obliquely with respect to the optical axis. If necessary, a plurality of glass plates 20 may be arranged in parallel. The light emitted from the light source 2 is incident on the glass plate 20 disposed obliquely, one linearly polarized light component (S-polarized light) is reflected by the front and back surfaces of the glass plate, and the other linearly polarized light component is reflected. (P-polarized light) passes. The reflected S-polarized light is aligned by a reflecting mirror 18 and then changed in polarization direction by a half-wave plate 19 to become P-polarized light.
The S-polarized light, which has been wasted in the projection device 3, is also effectively used.

FIG. 15 is a cross-sectional view showing a case where a conventional prism type polarizing beam splitter is applied to an illumination system. The direction of light from a light source is aligned by a light shielding plate 28, and the separation film of the prism type polarizing beam splitter is separated. 17b, the p-polarized light component is transmitted, and the reflected s-polarized light component is
And converted into a P-polarized component by the half-wavelength plate 19, and emitted as a light beam corresponding to the microlens of the lens system on a one-to-one basis.

[0012]

However, the above-mentioned polarization conversion device has the following problems. In the prism type polarization splitting element, although the polarization splitting performance is excellent, many steps are required for processing the two triangular prisms 17a constituting the polarization splitting element. The polarization separation film used in the prism type polarization separation element is an optical thin film obtained by alternately laminating high-refractive-index material layers and low-refractive-index material layers to obtain desired optical characteristics by an optical interference effect, and is usually vacuum-deposited. It is formed by a dry film forming method such as a sputtering method or a sputtering method. However, any apparatus used for the dry film forming method is expensive, and in addition, the number of layers is as large as about 30 to 50 layers, so that the manufacturing cost is high. As a result, there is a disadvantage that the manufacturing cost of the entire device is increased.

The plate-type polarization separation element is simple and inexpensive because it can be constituted by only one or a plurality of glass plates 20. On the other hand, each polarization component is obtained by utilizing only the reflection characteristics on the front and back surfaces of the glass plate. , The polarization separation performance is not sufficient as compared with the prism type polarization separation element, and there is a disadvantage that the absorption of light into the incident side polarizing plate of the liquid crystal panel 7 and the temperature rise are not necessarily suppressed. . FIG.
FIG. 9 is a diagram showing characteristics of various polarization separation elements.
The optical characteristics of the plate-type polarization splitting element (a) are as follows. The transmittance of S-polarized light in the wavelength range of 400 nm to 650 nm used in the projection display device is 20%, and the prism type shown in FIG. It shows that the separation performance is lower than that of the polarization separation element.

Further, an example in which a liquid crystal is used as a polarization separation film has been reported (SID98, LP-O "High").
-Contrast-Ratio Broad-Ang
leLC Polarizing Beamsplit
ter ", 1998, P691-P693). In this conventional example, as shown in FIG.
The liquid crystal is sealed between the substrates 1 and 1 to use the liquid crystal as a polarization separation film. Also in this conventional example, it cannot be said that it is particularly advantageous in terms of manufacturing difficulty and cost as compared with the case where the above-mentioned optical multilayer film is used as a polarization separation film.

The present invention has been made to solve the above problems, and has as its object to provide a polarization conversion element having necessary and sufficient polarization separation performance at a low cost. A polarization conversion element used in the illumination optical system of the projection display device, an optically anisotropic optical film or dielectric layer having a different refractive index in the vertical direction and the horizontal direction with respect to the light incident surface, and an optical block, Cost reduction can be achieved by using the polarization conversion element of the present invention constituted by a half-wave plate.

[Means for Solving the Problems]

According to the present invention, light from a white light beam is converted into specific linearly polarized light by a polarization conversion element, and then separated by a dichroic mirror into red, green, and blue light beams. After being incident on the corresponding liquid crystal light valve, each color light incident by the liquid crystal light valve is modulated and emitted, the modulated respective color lights are recombined by the dichroic prism, and finally the combined light is transmitted by the projection lens. Suitable for use as a polarization conversion element of a projection display device that is enlarged and projected on a screen,
The present invention relates to a polarization conversion element.

According to a first aspect of the present invention, there is provided a first column-shaped first member made of optical glass or plastic material and having a polygonal cross section.
, A column-shaped second block having a polygonal cross section made of glass or plastic material for optics, between one surface of the first block, and one surface of the second block. A polarizing beam splitter, comprising: an optically anisotropic optical film having a different refractive index in a direction perpendicular and parallel to a light incident surface, which is sandwiched via a bonding material. Item 2 is a column-shaped first block having a polygonal section made of an optical glass or plastic material and a column-shaped second block having a polygonal section made of an optical glass or plastic material. And between one surface of the first block and one surface of the second block via a bonding material,
An optically anisotropic optical film having a different refractive index in a direction perpendicular to and parallel to a light incident surface, and a surface on which the optical film of the first or second block is not bonded via a bonding material. A polarizing conversion element having a phase difference film attached thereto, wherein the first block having a polygonal cross-section made of glass or plastic material for optics is a column-shaped first block. And a column-shaped second block made of glass or plastic material for optics and having a polygonal cross section, one surface of the first block, and one surface of the second block. Optically anisotropic optical film having different refractive indexes in a direction perpendicular and parallel to a light incident surface, which is sandwiched between materials,
A phase difference film attached to a surface of the first or second block where the optical film is not bonded via a bonding material, and a light beam or the optically anisotropic film transmitted through the phase difference plate; A polarization conversion element comprising: a direction conversion unit configured to change a direction of a light beam that has passed through a surface of another block that is symmetric with the phase difference plate.

According to a fourth aspect of the present invention, there is provided a light source, a polarization conversion element for converting a polarization direction of light emitted from the light source into linearly polarized light in a specific direction, and a light beam of linearly polarized light emitted from the polarization conversion element. And a projection type display device having a projection unit for enlarging and projecting a modulated light beam emitted from the light valve onto a screen, wherein the polarization conversion element has a cross section made of optical glass or plastic material. A polygonal column-shaped first block, a column-shaped second block made of a glass or plastic material for optical use having a polygonal cross section, one surface of the first block, and the second block. An optically anisotropic optical film having different refractive indices in a direction perpendicular and parallel to a light incident surface, which is sandwiched between one surface of the block via a bonding material; 6. A projection display device comprising: a retardation film attached to a surface of the first or second block to which the optical film is not bonded via a bonding material. Is a light source,
A polarization conversion element that converts a polarization direction of light emitted from the light source into linear polarization in a specific direction, a light valve that modulates a linearly polarized light beam emitted from the polarization conversion element, and a modulated light beam that is emitted from the light valve. A projection means for enlarging and projecting the luminous flux onto a screen, wherein the polarization conversion element has a columnar first shape made of an optical glass or plastic material and having a polygonal cross section.
, A column-shaped second block having a polygonal cross section made of glass or plastic material for optics, between one surface of the first block, and one surface of the second block. An optically anisotropic optical film having different refraction in a direction perpendicular and parallel to a light incident surface, which is sandwiched via a bonding material, and the optical film of the first or second block is A retardation film adhered to a surface that is not joined via a joining material, and a surface of another block that is symmetric with the retardation plate with respect to the light flux transmitted through the retardation plate or the optically anisotropic film. And a direction changing means for changing the direction of the light beam having passed through the projection type display device.

According to a sixth aspect of the present invention, there is provided the first column-shaped first member made of optical glass or plastic material and having a polygonal cross section.
And a column-shaped second block having a polygonal cross section made of glass or plastic material for optics, and having different refractive indexes in a direction perpendicular to and parallel to a light incident surface. An isotropic dielectric layer is formed on one surface of the first block, and the first block is formed on one surface of the second block via a bonding material so as to sandwich the dielectric layer. A polarized light separating element characterized by being bonded, wherein the invention according to claim 7 is a column-shaped first block having a polygonal cross section made of optical glass or plastic material, and optical glass or plastic. A column-shaped second block having a polygonal cross section made of a plastic material, and a dielectric layer having optical anisotropy having different refractive indices in a direction perpendicular to and parallel to a light incident surface. One of the first blocks And the first block is bonded to one surface of the second block via a bonding material so as to sandwich the dielectric layer, and the first or second block is insulated. 9. A polarization conversion element, wherein a retardation film is attached to a surface not joined via a body layer via a joining material.
The invention of the present invention comprises a column-shaped first block having a polygonal cross section made of an optical glass or plastic material, and a column-shaped second block having a polygonal cross section made of an optical glass or plastic material. A dielectric layer having optical anisotropy having different refractive indices in a direction perpendicular to and parallel to a light incident surface is formed on one surface of the first block, and the dielectric layer The first block is bonded to one surface of the second block via a bonding material so as to be sandwiched therebetween, and the first or second block is positioned on a surface not bonded via the dielectric layer. A phase difference film is attached via a bonding material, and converts a direction of a light beam transmitted through the phase difference plate or a direction of a light beam transmitted through another block surface that is symmetrical to the phase difference plate with respect to the dielectric layer. Direction changing means A polarization conversion element, characterized by.

According to a ninth aspect of the present invention, there is provided a light source, a polarization conversion element for converting a polarization direction of light emitted from the light source into linearly polarized light in a specific direction, and a light beam of linearly polarized light emitted from the polarization conversion element. And a projection device for enlarging and projecting the modulated light flux emitted from the light valve onto a screen, the polarization conversion element has a cross section made of optical glass or plastic material. A first column-shaped block having a polygonal shape, and a second block having a columnar shape formed of a glass or plastic material for optics having a polygonal cross section, in a direction parallel to a direction perpendicular to a light incident surface. And a dielectric layer having an optical anisotropy having a different refractive index between one of the first blocks.
The first block is formed on one surface of the second block via a bonding material so as to sandwich the dielectric layer.
Wherein the first or second block is not joined via a dielectric layer, and a retardation film is attached via a joining material. A display device, wherein the invention according to claim 10 is a light source, a polarization conversion element that converts a polarization direction of light emitted from the light source into linear polarization in a specific direction, and a light beam of linear polarization emitted from the polarization conversion element And a projection means for enlarging and projecting the modulated light flux emitted from the light valve onto a screen, wherein the polarization conversion element is made of optical glass or plastic material. It has a first column-shaped block having a polygonal cross section and a second column-shaped block having a polygonal cross section made of glass or plastic material for optics. A dielectric layer having an optical anisotropy having a different refractive index in a direction perpendicular to and parallel to a projection surface is formed on one surface of the first block, and the second layer is sandwiched between the dielectric layers. The first block is bonded to one surface of the block via a bonding material, and the phase difference film is bonded to a surface where the first or second block is not bonded via a dielectric layer. Direction conversion means for changing the direction of the light flux transmitted through the phase difference plate or the direction of the light flux transmitted through the surface of another block that is symmetrical to the phase difference plate with respect to the dielectric layer. It is a projection type display device characterized by having.

[0021]

FIG. 1 is a partially enlarged cross-sectional view of a polarization beam splitting element according to a first embodiment of the present invention. An optical film 22 having an optical anisotropy having a different refractive index in a direction perpendicular to and parallel to a light incident surface is bonded between two optical blocks 21 via a bonding agent 23. The bonding agent neutralizes the refractive index on the optical block side or the optical film side. FIG. 2 (a)
FIG. 2B is a partially enlarged cross-sectional view of a polarization conversion element according to a second example of the embodiment of the present invention. In each case, a half-wave plate is attached to the minus side of the optical block of the polarization separation element shown in FIG. 1, and in FIG.
A dielectric layer 24 is used instead of 2.

As the optical block 21, any material is preferably used as long as it is transparent in the visible light region, such as resin such as acrylic and polycarbonate, and glass. The optical film 22 having an optical anisotropy having a different refractive index in a direction perpendicular to and parallel to a light incident surface is made of PET.
Any material such as (polyethylene terephthalate) and PEN (polyethylene naphthalate) may be used as long as it is transparent in the visible light region. Usually, these films are formed by continuously stretching a molten raw material in one direction into a film. Has optical anisotropy. If necessary, various dyes, pigments, dyes, and the like may be added to the film raw material to further improve the optical anisotropy performance.

As a material of the dielectric layer 24 shown in FIG. 2B, TiO2, Ta2O5, Nb2O5, SiO2, Z
rO2, MgF2 or the like is preferably used, and the crystal is oriented at a predetermined angle with respect to the normal direction of the surface, so that the refractive index differs between the direction perpendicular to the light incident surface and the direction parallel to the light incident surface. Anisotropy is developed. 3 and 4
Figure 2 shows the conceptual diagram. The dielectric layer has a polycrystalline structure,
In addition, the orientation direction of the crystal is oriented in a direction having a certain angle with respect to the normal direction, and acts as a polarization conversion element. These dielectric layers 24 are generally formed by a dry film forming method such as a vacuum evaporation method or a sputtering method, and as shown in FIG. Is formed.

FIG. 5 (a) is a diagram for explaining the refraction characteristics of the birefringent material of the present invention. The polarization using the birefringence characteristics of a crystal made of quartz, calcite (calcite, CaCO ₃ ), etc. The non-polarized light, which is the polarizer 29 and entered from the upper surface of the polarizer, is separated into two polarization components whose polarization planes are orthogonal to each other, and is emitted as linearly polarized light.
One of the emitted light rays is called a normal light ray (ordinary light ray) because it is a light ray according to Snell's law and the law of reflection, and the other is called an extraordinary light ray.

FIG. 5B is an explanatory diagram of a Glan-Thompson prism 30 which is a polarizing prism utilizing birefringence characteristics. The Glan-Thompson prism 30 is obtained by bonding two calcites with a bonding agent, and the ordinary ray is totally reflected at the interface between the calcite and the bonding agent due to the difference in the refractive index between the calcite and the bonding agent. It is absorbed by the absorption layer 31. On the other hand, the extraordinary ray is transmitted as it is, and a linearly polarized light having a high degree of polarization can be obtained.

Next, the operation of the present invention will be described. FIG. 6 (a)
As shown in FIG. 5, when light is incident from the medium A having the large refractive index n1 to the medium B having the small refractive index n2, the light is transmitted to the interface In between the two media when the incident angle exceeds the critical angle θc.
Causes total internal reflection. The critical angle θc is, according to Snell's law,
It is given by the following equation. θc = sin ⁻¹ (n ₂ / n ₁ ) n1> n2 Therefore, when incident at an incident angle θ smaller than the critical angle θc, the light enters the medium B as shown in FIG. When light is incident at an incident angle θ larger than the angle θc, as shown in FIG. 6C, total reflection occurs at the interface In. It no longer enters medium B.

FIG. 7 shows the relationship between the refractive indices n1 and n2 of the media A and B and the critical angle. FIG. 7A shows the relationship between the refractive indices n1 and n2.
Is a diagram showing the relationship between the refractive index n2 and the critical angle θ when the value changes from 1.5 to 2.0, and FIG. 7B is a diagram showing the concept. In this figure, the upper side of each curve indicates a region where light is incident from the medium A to the medium B, and the lower side indicates a region where light is reflected at the interface.

When the refractive index n2 of the medium B has optical anisotropy in which the refractive index differs in a direction perpendicular to the light incident surface (S polarization direction) and in a direction parallel to the light incidence surface (P polarization direction), If the incident angle θ of the light and the refractive index n1 of the medium A are appropriately selected so that the light is totally reflected in the polarization direction with the smaller refractive index, the light in the polarization direction with the larger refractive index is not totally reflected at the interface In, It becomes possible to enter the medium B, and each polarized light component can be separated. Whether the S-polarized light or the P-polarized light is transmitted or reflected is determined by the magnitude of the refractive index for each polarized light of the optical film having optical anisotropy, and the polarized light having the larger refractive index is transmitted.

The incident angle θ of light and the refractive index of the optical film used in each polarization direction can be appropriately selected according to the layout of the optical system to be applied. Since there is practically no bulk material transparent in the visible light region having a refractive index smaller than 1.3, n1 (for example, around 1.7) and n2 are appropriately set in a region where the light incident angle θ is around 70 °. (For example, 1.4
~ 1.5).

FIGS. 8A and 8B schematically show a case where the polarization splitting element and the polarization conversion element of the present invention are applied to an illumination system of a liquid crystal projector. The polarization splitting element 25 shown in FIG. 8A transmits light polarized in a direction perpendicular to the light incident surface (S polarization direction) and reflects light polarized in a parallel direction (P polarization direction). Is set to After the light emitted from the light source 2 enters the polarization separation element 25, only the S-polarized light is emitted. in this way,
What can be set to transmit S-polarized light is the characteristics of a beam splitter using a stretched optical film. If you also want to use the reflected P-polarized light effectively,
As shown in FIG. 8B, the P-polarized light that has entered the polarization conversion element 26 and reflected by the polarizing film is a half-wave plate 1
At 9, the light is converted into S-polarized light, is aligned in the same direction as the S-polarized light by the reflection mirror 18, and is introduced into the liquid crystal light valve.

FIGS. 9 (a), 9 (b) and 9 (c) show the optical characteristics of the plate type, the prism type and the polarization splitting element of the present invention, respectively. The polarization separating element has better separation performance as the transmittance of one polarized component (P-polarized light in this figure) is higher and the transmittance of the other polarized component (S-polarized light in this figure) is lower. Will be. A plate-type polarization separation element and a prism-type polarization separation element are used.
When compared at 0 nm, the performance is almost the same for P-polarized light, but about 20% leaks for S-polarized light in the case of the plate-type polarization separation element. It can be seen that is inferior in performance as compared with the prism type polarization separation element. On the other hand, when comparing the prism type and the polarization separation element of the present invention, it can be seen that the transmittance is almost the same and the polarization separation performance is also at the same level.

FIG. 10 is a sectional view showing another embodiment of the present invention. In this embodiment, it is set so as to use P-polarized light. In the example of the present embodiment, the polarization conversion element 24 is applied to an illumination system, and only parallel light uniform from the light source 2 is emitted from the optically anisotropic polymer film or the dielectric layer by the light shielding plate 28. Incident on the polarization separation film 24, the P-polarized light is transmitted, the S-polarized light is reflected, and
By passing through the wave plate, it is converted into P-polarized light,
The light is reflected by the reflection mirror 18 and is incident on an illumination system (not shown) as a light flux parallel to the P-polarized light transmitted through the polarization separation film 24.

As described in detail above, the performance of the polarization separation element of the present invention using an optical film having an optical anisotropy having different refractive indices in a direction perpendicular to and parallel to a light incident surface is as follows. Since there is no need to use an expensive optical thin film in spite of being equivalent to the prism type, the cost can be significantly reduced. In addition, the same function can be obtained when an obliquely oriented dielectric film is used instead of an optical film, and desired optical characteristics can be obtained with several layers unlike ordinary optical thin films, so that relatively low cost can be achieved. I can do it.

Next, examples of the present invention are shown together with comparative examples. The polarization conversion device of the present invention using an optical film or a dielectric layer having an optical anisotropy having different refractive indexes in a direction perpendicular to and parallel to a light incident surface was evaluated as follows. The brightness of the center of the screen equivalent to 40 inches enlarged and projected by the optical unit incorporating the polarization conversion element was measured with an illuminometer. The higher the illuminance, the brighter the image projected on the screen and the higher the performance. Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to the following examples.

COMPARATIVE EXAMPLE 1 As a result of measuring the brightness at the center of the screen of a projection type display apparatus comprising an optical unit having a conventional prism type polarization conversion element therein, the illuminance was 345 lux.

Example 1 The direction perpendicular to the light incident surface (S-polarized light) and the direction parallel to the
The optical film having the optical anisotropy whose refractive index of the polarized light is 1.5 and 1.4, respectively, is placed in an optical block (optical glass B).
K7) was manufactured. Subsequently, the brightness at the center of the screen of the projection display device including the optical unit having the polarization conversion element therein was measured. As a result, the illuminance was 350 lux.

Example 2 An obliquely oriented dielectric layer having an optical anisotropy having refractive indices of 1.6 and 1.5 respectively in a direction perpendicular to and parallel to a light incident surface was formed on an optical block (optical glass BK7). Manufactured by the company). Subsequently, as a result of measuring the brightness at the center of the screen of the projection type display device including the optical unit having the polarization conversion element therein, the illuminance was 3.
It was 90 looks.

Example 3 Polarization conversion in which an optical film having an optical anisotropy whose refractive index in the direction perpendicular to the light incident surface and in the direction parallel to the light incident surface was 1.5 and 1.4, respectively, was sandwiched between acrylic optical blocks. An element was manufactured. Subsequently, the brightness at the center of the screen of the projection display device including the optical unit having the polarization conversion element therein was measured. As a result, the illuminance was 350 lux.

[0039]

According to the present invention, there is provided an optical film or a dielectric layer having an optical anisotropy in which a polarization conversion element has an optical anisotropy having different refractive indices in a direction perpendicular to and parallel to a light incident surface, and an optical block. Because it is composed of a wave plate and a reflection mirror,
An inexpensive and high-performance projection display device having high polarization conversion performance can be provided.

[Brief description of the drawings]

FIG. 1 is a partially enlarged cross-sectional view of a polarization beam splitter of the present invention.

FIG. 2 is an enlarged cross-sectional view of a part of the polarization conversion element of the present invention;
(A) shows an example in which a polymer film having optical anisotropy is used as a polarization separation element, and (b) shows an example in which a dielectric multilayer film is used as a polarization separation element.

FIG. 3 is a conceptual diagram showing the principle of the present invention, and is a conceptual diagram of an oblique alignment film.

FIG. 4 is a conceptual diagram showing a state where a dielectric layer of the present invention is generated.

FIG. 5 shows the principle of the birefringence characteristic of the present invention.
FIG. 3B is a conceptual diagram showing a principle of separation into a normal ray and an extraordinary ray by birefringence, and FIG.

FIG. 6 is a view for explaining incidence and reflection of light at an interface of the polarization separation element.

FIG. 7 is a diagram for explaining the operation of the polarization beam splitter of the present invention.

FIGS. 8A and 8B are cross-sectional views illustrating an embodiment of the polarization beam splitter of the present invention, wherein FIG. 8A shows a case where only one polarized light is used, and FIG. 8B shows a case where two polarized lights are used. Sectional drawing which shows the example of FIG.

FIG. 9 is a diagram showing optical characteristics of a plate type, a prism type, and a polarization beam splitter of the present invention.

FIG. 10 is a sectional view showing an example in which the polarization conversion element of the present invention is applied to an illumination system.

FIG. 11 is a sectional view showing a typical configuration of an optical unit used in a conventional liquid crystal projector.

FIG. 12 is a schematic cross-sectional view of a conventional front projection type and rear projection type liquid crystal projector.

FIG. 13 is a partially enlarged cross-sectional view of a liquid crystal light valve.

FIG. 14 is a cross-sectional view for explaining functions of a conventional prism type and plate type polarization conversion element.

FIG. 15 is a cross-sectional view showing an example in which a conventional polarization conversion element is applied to an illumination system.

FIG. 16 is an explanatory diagram of a conventional example using a liquid crystal as a polarization separation element.

[Explanation of symbols]

Reference Signs List 1 optical unit, 2 light sources, 3 ultraviolet / infrared cut filter, 4 polarization conversion element, 5 multi-lens array, 6 dichroic mirror, 7 liquid crystal light valve, 8 dichroic prism, 9 projection lens, 1
0 screen, 11 cabinets, 12 observers,
15a / 15b polarizing plate, 16 liquid crystal panel, 17 prism type polarization conversion element, 17a triangular prism, 17
b polarization splitting film, 18 reflection mirror, 19 1/2 wavelength plate, 20 glass plate, 21 optical block, 22
Optical film, 23 bonding agent, 24 dielectric layer, 25
Polarization splitter, 26 polarization converter, 27 crystal, 28
Shielding plate, 29 polarizer, 30 Glan-Thompson prism, 31 absorption layer.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03B 21/00 G03B 21/00 E 5G435 G09F 9/00 336 G09F 9/00 336E 360 360D H04N 5/74 H04N 5/74 K (72) Inventor Koji Kita 6-35 Kita-Shinagawa, Shinagawa-ku, Tokyo F-term within Sony Corporation (reference) 2H042 CA01 CA07 CA14 CA17 2H049 BA05 BA06 BA42 BB03 BB44 BB61 BC03 BC22 2H088 EA14 EA17 HA09 HA13 HA16 HA21 HA24 HA28 KA05 MA01 MA20 2H091 FA05Z FA07Z FA11Z FA14Z FA26X FA26Z FA41Z FB02 FB06 FC01 KA01 LA12 LA16 5C058 BA35 EA11 5G435 AA03 AA17 BB12 BB15 BB17 DD05 FF25 GG03 FF02 GG03 FF25 GG02 FF02 GG03 FF03

Claims (10)

[Claims] 1. A first column-shaped block made of an optical glass or plastic material having a polygonal cross section, and a second column-shaped block made of an optical glass or plastic material having a polygonal cross section. The one side of the first block and the one side of the second block are refracted in a direction perpendicular and parallel to a light incident surface, which is sandwiched by a bonding material. A polarizing beam splitter comprising: an optically anisotropic optical film having a different ratio. 2. A first column-shaped block made of a glass or plastic material for optics and having a polygonal cross section, and a second block made of a column made of a glass or plastic material for optics and having a polygonal shape. The one side of the first block and the one side of the second block are refracted in a direction perpendicular and parallel to a light incident surface, which is sandwiched by a bonding material. Having an optically anisotropic optical film having different ratios, and a retardation film attached via a bonding material to a surface of the first or second block where the optical film is not bonded. Polarization conversion element. 3. A first column-shaped block made of an optical glass or plastic material having a polygonal cross section, and a second column-shaped block made of an optical glass or plastic material having a polygonal cross section. The one side of the first block and the one side of the second block are refracted in a direction perpendicular and parallel to a light incident surface, which is sandwiched by a bonding material. Optical anisotropic optical films having different ratios, a retardation film adhered to a surface of the first or second block where the optical film is not joined through a joining material, and the retardation plate A polarization conversion element comprising: a direction conversion unit configured to change a direction of a transmitted light beam or a light beam that has passed through a surface of another block that is symmetrical to the phase difference plate with respect to the optically anisotropic film. 4. A light source, a polarization conversion element for converting a polarization direction of light emitted from the light source into linearly polarized light in a specific direction, and a light valve for modulating a linearly polarized light beam emitted from the polarization conversion element, A projection unit for enlarging and projecting the modulated light beam emitted from the light valve onto a screen, wherein the polarization conversion element has a columnar shape having a polygonal cross section made of optical glass or plastic material. A first block having a polygonal cross section made of glass or plastic material for optics; one surface of the first block; and one surface of the second block An optically anisotropic optical film having a refractive index different between a direction perpendicular to and a direction parallel to the light incident surface, which is sandwiched by a bonding material between the first and second optical films; Projection display device characterized by having a phase difference film in which the optical film of the block is adhered by means of a bonding material to a surface which is not bonded. 5. A light source, a polarization conversion element that converts a polarization direction of light emitted from the light source to linear polarization in a specific direction, and a light valve that modulates a light beam of linear polarization emitted from the polarization conversion element. A projection unit for enlarging and projecting the modulated light beam emitted from the light valve onto a screen, wherein the polarization conversion element has a columnar shape having a polygonal cross section made of optical glass or plastic material. A first block having a polygonal cross section made of glass or plastic material for optics; one surface of the first block; and one surface of the second block An optically anisotropic optical film having a different refractive index in a direction perpendicular and parallel to a light incident surface, which is sandwiched by a bonding material between the first and second optical films; A retardation film adhered to a surface of the block where the optical film is not joined via a bonding material, and a luminous flux transmitted through the retardation plate or the optically anisotropic film and the symmetry with the retardation plate. A direction changing means for changing a direction of a light beam passing through a surface of another block. 6. A first column-shaped block made of a glass or plastic material for optics having a polygonal cross section, and a second block formed of a column having a polygonal cross section made of a glass or plastic material for optics. A dielectric layer having optical anisotropy having different refractive indices in a direction perpendicular to and parallel to a light incident surface is formed on one surface of the first block; 1 of the second block
A polarization separation element, wherein the first block is bonded to two surfaces via a bonding material. 7. A first column-shaped block made of an optical glass or plastic material having a polygonal cross section, and a second column-shaped block made of an optical glass or plastic material having a polygonal cross section. A dielectric layer having optical anisotropy having different refractive indices in a direction perpendicular to and parallel to a light incident surface is formed on one surface of the first block; One of the second blocks is sandwiched between layers.
The first block is bonded to one surface via a bonding material, and the retardation film is bonded to the surface where the first or second block is not bonded via the dielectric layer via the bonding material. A polarization conversion element, which is attached. 8. A first column-shaped block made of an optical glass or plastic material and having a polygonal section, and a second column-shaped block made of an optical glass or plastic material and having a polygonal shape. A dielectric layer having optical anisotropy having different refractive indices in a direction perpendicular to and parallel to a light incident surface is formed on one surface of the first block; 1 of the second block so as to sandwich
The first block is bonded to one surface via a bonding material, and the retardation film is bonded to the surface where the first or second block is not bonded via the dielectric layer via the bonding material. Direction conversion means for changing the direction of a light beam transmitted through the phase difference plate or a light beam passed through the surface of another block that is symmetrical to the phase difference plate with respect to the dielectric layer. Polarization conversion element. 9. A light source, a polarization conversion element for converting a polarization direction of light emitted from the light source into linearly polarized light in a specific direction, and a light valve for modulating a linearly polarized light beam emitted from the polarization conversion element, A projection unit for enlarging and projecting the modulated light beam emitted from the light valve onto a screen, wherein the polarization conversion element has a columnar shape having a polygonal cross section made of optical glass or plastic material. And a column-shaped second block having a polygonal cross section made of an optical glass or plastic material, and having a refractive index in a direction perpendicular and parallel to a light incident surface. A dielectric layer having a different optical anisotropy is formed on one surface of the first block, and one of the second blocks is sandwiched between the dielectric layers.
The first block is bonded to one surface via a bonding material, and the retardation film is bonded to the surface where the first or second block is not bonded via the dielectric layer via the bonding material. A projection display device, which is attached. 10. A light source, a polarization conversion element that converts a polarization direction of light emitted from the light source to linearly polarized light in a specific direction, and a light valve that modulates a light beam of linearly polarized light emitted from the polarization conversion element. A projection unit for enlarging and projecting the modulated light beam emitted from the light valve onto a screen, wherein the polarization conversion element has a columnar shape having a polygonal cross section made of optical glass or plastic material. And a column-shaped second block having a polygonal cross section made of an optical glass or plastic material, and having a refractive index in a direction perpendicular and parallel to a light incident surface. A dielectric layer having a different optical anisotropy is formed on one surface of the first block, and one of the second blocks is sandwiched between the dielectric layers.
The first block is bonded to one surface via a bonding material, and the retardation film is bonded to the surface where the first or second block is not bonded via the dielectric layer via the bonding material. Direction conversion means for changing the direction of the light beam transmitted through the phase difference plate or the light beam transmitted through the surface of another block that is symmetrical to the phase difference plate with respect to the dielectric layer. Projection type display device.