Polarization conversion element, polarization illuminator, display using the same illuminator, and projector

A polarizing conversion device in accordance with the invention includes a first optical element for condensing an incident beam and forming a plurality of intermediate beams spatially separated from one another, and a second optical element for spatially separating each intermediate beam into two polarized beams and aligning the polarization directions of the polarized beams, thereby obtaining the same type of polarized beams. In the second optical element, a shading plate is placed to prevent light from directly entering a section corresponding to a reflecting plane of a polarizing separation unit array. Since the ability of separating the intermediate beam into two polarized beams is thereby enhanced, it is possible to perform conversion into the same type of polarized beams polarized in the same direction, with high efficiency.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polarizing conversion device and a polarizing illumination device for generating, from incident light beams as randomly polarized beams, illuminating beams that have a more uniform light intensity distribution in an illumination region than that of the incident beams and are polarized in almost the same direction. Furthermore, the present invention relates to a display apparatus and aprojection display apparatusprojectorusing these devices.

2. Description of Related Art

A polarizing illumination device capable of efficiently generating the same type of polarized light beams is ideal as an illuminating device for use in a display apparatus, such as a liquid crystal apparatus, which employs a panel for modulating polarized light beams. Accordingly, an illuminating optical system has been proposed that converts random polarized light beams emitted from a light source into the same type of polarized light beams and illuminates a liquid crystal apparatus with the light beams so that a bright display is achieved. Japanese Unexamined Patent Publication No. 7-294906 discloses an image display apparatus equipped with such an illuminating optical system.

The principal part of the illuminating optical system disclosed in Japanese Unexamined Patent Publication No. 7-294906 will be briefly described with reference to FIG.15. This optical system mainly comprises a lens plate910, a plurality of polarizing beam splitters920, a plurality of reflecting prisms930, and a plurality of λ/2phase plates940. Incident beams as randomly polarized beams are separated into two types of polarized beams (P polarized beams and S polarized beams) through the polarizing beam splitters920which are respectively provided with polarizing separation planes331and the reflecting prisms930which are respectively provided with reflecting planes332. After the separation, the polarization direction of polarized beams of one of the types is matched with that of polarized beams of the other type by using the λ/2 phase plates940, thereby obtaining polarized beams of the same type and illuminating a liquid crystal device950with the light beams. In general, since a space for forming two types of polarized beams therein is needed in the polarized beam separation process, the optical system is inevitably widened. Accordingly, this optical system reduces the diameter of the beams, which are incident on the respective polarizing beam splitters920, to less than about half the diameter of small lenses911formed in the lens plate910by means of the small lenses911, and places the reflecting prisms (reflecting planes)930in the spaces produced by the reduction of the diameter of the beams, whereby the same type of polarized beams are obtained without widening the optical system.

The optical system disclosed in Japanese Unexamined Patent Publication No. 7-294906 has, however, the following problems.

In reducing the diameter of the beam by the lens, generally, the minimum beam diameter is almost directly and exclusively determined by the refractive power of the lens and parallelism of the light beam incident on the lens. That is, in order to reduce the beam diameter to less than half the lens diameter as in the optical system disclosed in Japanese Unexamined Patent Publication No. 7-294906, it is necessary to use a lens having an extremely high refractive power (in other words, a lens having an extremely small F-number) and a light source capable of emitting a light beam having extremely high parallelism. However, a real light source has a limited emission area. Therefore, parallelism of the light beam emitted from the light source is not always good.

On the other hand, the polarizing separation ability of the polarizing separation plane formed in the polarizing beam splitter is highly dependent on the incident angle of light. In other words, when the light that is incident on the polarizing separation plane has a large angular component, the polarizing separation plane cannot exhibit and ideal polarizing separation ability, and S polarized beam mixes into the P polarized beam transmitting through the polarizing separation plane, and the P polarized beam mixes into the S polarized beam reflected from the polarizing separation plane. Consequently, it is impossible to excessively increase the refractive power of the small lens used for reducing the diameter of the beam.

For the above reasons, it is difficult to sufficiently reduce the diameter of the light beam that is incident on the polarizing beam splitter, and, in actuality, a relatively large amount of light also directly enters the reflecting prism adjoining the polarizing beam splitter. The light that is directly incident on the reflecting prism is reflected by the reflecting plane, enters the adjoining polarizing beam splitter, and is separated into two types of polarized beams by the polarizing separation plane in the same manner as the light beam that is directly incident on the polarizing beam splitter. The light beam that is incident on the polarizing beam splitter through the reflecting prism and the light beam that is directly incident on the polarizing beam splitter are different by 90° in the incident with respect to the polarizing beam splitter. As a consequence of the existence of the light beam directly incident on the reflecting prism, the S polarized beam directly incident on the reflecting prism and separated through the polarizing beam splitter mixes into the P polarized beam that transmits through the polarizing beam splitter without changing its direction of travel. Similarly, the S polarized beam mixes into the P polarized beam that directly enters the polarizing beam splitter and is emitted through the reflecting prism and the λ/2 phase plate. Since the S polarized beam mixed into the P polarized beam because of the existence of the light beam directly incident on the reflecting prism is quite unnecessary for the liquid crystal device, it is absorbed by a polarizing plate and generates heat, which is the main factor that increases the temperature of the polarizing plate.

Thus, in the process in which the conventional optical system disclosed in Japanese Unexamined Patent Publication No. 7-294906 converts random light beams emitted from the light source into polarized beams of the same type, a relatively large number of polarized beams of another type inevitably mix. As a result, the polarized beams, which are unnecessary for display and are polarized in a different direction, are required to be absorbed by the polarizing plate in order to obtain an extremely bright display image. In addition, a large cooling device is essential to restrict the increase in temperature of the polarizing plate caused by the absorption of the polarized beams.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to solve the above problems by substantially restricting the mixing of other polarized beams, which are polarized in a different direction, in a process of converting randomly polarized beams emitted from a light source into the same type of polarized beams.

In order to solve the above problems, a polarizing conversion device in accordance with the present invention comprises a polarizing separation element that has a polarizing separation plane for separating P and S polarized beams by transmitting one of the polarized beams therethrough and reflecting the other polarized beam, and a reflecting plane disposed substantially parallel with the polarizing separation plane to reflect the polarized beam reflected by the polarizing separation plane toward the emergent direction of the polarized beam transmitted through the polarizing separation plane, and a selective phase plate located on the light emergent side of the polarizing separation element to align the polarization direction of one of the S and P polarized beams separated by the polarizing separation element with the polarization direction of the other polarized beam, wherein at least one of a shading means and an optical attenuating means for preventing light from directly entering the reflective plane is provided on the light incident side of the polarizing separation element.

The above structure enables the polarizing conversion device of the present invention to effectively prevent or restrict a phenomenon in which other polarized beams polarized in a different direction mix into polarized beams of almost the same type polarized in the same direction. Therefore, it is possible to generate specific polarized beams with an extremely high efficiency.

In the above-mentioned polarizing conversion device, it is preferable that the shading means or the optical attenuating means and the polarizing separation element are integrated. It is therefore possible to reduce light losses at an interface, and to thereby provide a polarizing conversion device having a high light use efficiency.

The shading means may be formed of a reflecting plate. When the shading means is formed of a reflecting plate, it does not absorb much light, and therefore, does not generate much heat. Consequently, it is possible to prevent peripheral optical elements from being thermally influenced by heat generation of the shading means. This is effective particularly when the selective phase plate is made of an organic substance that is not heat-resistant.

Furthermore, when the shading means and the polarizing separation element are integrated, the shading means may be formed of a reflecting film that is formed on the light incident surface of the polarizing separation element. Such a structure also provides similar advantages as those achieved in the situation wherein the shading means is formed of a reflecting plate. The reflecting film may be formed of a dielectric multilayer film, or a thin film of metal having high reflectivity, such as silver or aluminum.

Still furthermore, the optical attenuating means in the polarizing conversion device may be formed of a light diffusing plate. When the optical attenuating means is formed of a light diffusing plate, it is possible to reduce the cost of the polarizing conversion device.

When the shading means and the polarizing separation element are integrated, the optical attenuating means may be formed of a light diffusing surface formed on the light incident surface of the polarizing separation element. Such a structure also provides similar advantages as those achieved in the situation wherein the optical attenuating means is formed of a light diffusing plate. The light diffusing surface may be formed by roughening a specific region on the light incident surface of the polarizing separation element.

A polarizing illumination device in accordance with the present invention comprises a light source, a first optical element for separating a light beam emitted from the light source into a plurality of intermediate beams, and a second optical element disposed near the position where the intermediate beams converge, wherein the second optical element has a condenser lens array that includes a plurality of condenser lenses for respectively condensing the intermediate beams, a polarizing separation element for spatially separating each of the intermediate beams into an S polarized beam and a P polarized beam, a selective phase plate for aligning the polarization direction of one of the S and P polarized beams separated by the polarizing separation element with the polarization direction of the other polarized beam, and a superimposing lens for superimposing the polarized beams, the polarizing separation element has a polarizing separation plane for separating the P and S polarized beams by transmitting one of the polarized beams therethrough and reflecting the other polarized beam and a reflecting plane disposed substantially parallel with the polarizing separation plane to reflect the polarized beam reflected by the polarizing separation plane toward the emergent direction of the polarized beam transmitted through the polarizing separation plane, and at least one of a shading means and an optical attenuating means for preventing each of the intermediate beams from directly entering the reflecting plane is interposed between the first optical element and the polarizing separation element.

By adopting the above structure, the polarizing illumination device in accordance with the present invention can effectively prevent or restrict a phenomenon in which other polarized beams polarized in a different direction mix into polarized beams of almost the same type polarized in the same direction. Therefore, it is possible to obtain as illumination light polarized beams with a considerably high degree of polarization.

According to the above structure, an incident beam is initially separated into a plurality of intermediate beams and the intermediate beams are finally superimposed on one illumination region. Therefore, even if the intensity distribution of the incident beam is very imbalanced in the cross section thereof, it is possible to use as illumination light polarized beams that are uniform in brightness and color. Furthermore, even when each of the intermediate beams cannot be separated into a P polarized beam and an S polarized beam that have equal light intensity and spectral characteristics, and even when the light intensity and the spectral characteristics of one of the polarized beams changes in a process of aligning the polarization directions of the polarized beams, it is possible to use as illumination light polarized beams that are uniform in brightness and color.

In addition, a plurality of polarized beam brought into almost one type of polarization state are gathered as a whole, superimposed on one illumination region, and form a large bundle of beams. Since the polarized beams of this large bundle of beams themselves do not accompany a beam component that has a large divergence angle, illumination with these light beams secures a high illumination efficiency.

The light source may include a light source lamp and a reflector. A metal halide lamp, a xenon lamp, a halogen lamp, and similar devices may be used as the light source lamp, and a parabolic reflector, an elliptic reflector, a spherical reflector, and similar devices may be used as the reflector.

In the above polarizing illumination device, the shading means or the optical attenuating means may be placed at any position between the polarizing separation element and the first optical element. However, if the shading means or the optical attenuating means is integrated with the polarizing separation element, it is possible to reduce light loss at the interface and to therapy provide a polarizing illumination device having a high light use efficiency. Furthermore, the second optical element can be formed in one piece by integrating the shading means or the optical attenuating means and the polarizing separation element, and in that situation, the second optical element can be made to be considerably compact.

The shading means or the optical attenuating means may be integrated with the condenser lens array. This provides similar advantages to those of the situation in which the shading means or the optical attenuating means is integrated with the polarizing element. Furthermore, in this situation, when the condenser lens array integrated with the shading means or the optical attenuating means is placed spatially apart from other optical elements to form the second optical element (for example, the polarizing separation element and the selective phase plate), even if the shading means or the optical attenuating means generates heat due to light absorption, it is possible to prevent the other optical elements from being thermally influenced by the heat generation.

In the above polarizing illumination device, the shading means may be formed of a reflecting plate. When the shading means is formed of a reflecting plate, it does not absorb much light, and therefore, does not generate much heat. Consequently, it is possible to prevent peripheral optical elements from being thermally influenced by heat generation of the shading means. This is effective particularly when the selective phase plate is made of an organic substance that has small heat resistance. Moreover, when the shading means is formed of a reflecting plate, light reflected by the reflecting plate is allowed to return the light source once, to be reflected again by the reflector at the light source, and to enter the polarizing separation element again. Therefore, it is possible to effectively use the light from the light source without waste.

Furthermore, when the shading means is integrated with the polarizing conversion device and the condenser lens array, the shading means may be formed of a reflecting film that is formed on the light incident surface of the polarizing separation element or the light emergent surface of the condenser lens array. Such a structure also provides similar advantages to those of the situation in which the shading means is formed of a reflecting plate. The reflecting film may be formed of a dielectric multilayer film, or a thin film of metal having high reflectivity, such as silver or aluminum.

In the above polarizing illumination device, the optical attenuating means may be formed of a light diffusing plate. When the optical attenuating means is formed of a light diffusing plate, it is possible to achieve cost reduction of the polarizing illumination device.

When the optical attenuating means is integrated with the polarizing conversion device of the condenser lens array, it may be formed of a light diffusing surface formed on the light incident surface of the polarizing separation element or the light emergent surface of the condenser lens array. Such a structure also provides similar advantages as those achieved in the situation in which the optical attenuating means is formed of a light diffusing plate, and the situation in which the optical diffusing plate is integrated with the polarizing separation element or the condenser lens array. The light diffusing surface may be formed by roughening a specific region on the light incident surface of the polarizing separation element or the light emergent surface of the condenser lens array.

A display apparatus in accordance with the present invention comprises a light source, a first optical element for separating a light beam emitted from the light source into a plurality of intermediate beams, a second optical element located near the position where the intermediate beams converge, and a modulating device for modulating a light beam emitted from the second optical element, wherein the second optical element has a condenser lens array that includes a plurality of condenser lenses for respectively condensing the intermediate beams, a polarizing separation element for spatially separating each of the intermediate beams into an S polarized beam and a P polarized beam, a selective phase plate for aligning the polarization direction of one of the S and P polarized beams separated by the polarizing separation element with the polarization direction of the other polarized beam, and a superimposing lens for superimposing the polarized beams, the polarizing separation element has a polarizing separation plane for separating the P and S polarized beams by transmitting the one of the polarized beams therethrough and reflecting the other polarized beam and a reflecting plane disposed substantially parallel with the polarizing separation plane to reflect the polarized beam reflected by the polarizing separation plane toward the emergent direction of the polarized beam transmitted through the polarizing separation plane, and at least one of a shading means and an optical attenuating means for preventing each of the intermediate beams from directly entering the reflecting plane is interposed between the first optical element and the polarizing separation element.

By adopting the above structure, the display apparatus in accordance with the present invention can effectively prevent a phenomenon in which other polarized beams polarized in a different direction mix into polarized beams of almost the same type polarized in the same direction. Therefore, when a polarizing plate is used to obtain a required polarized beam modulated by the modulating device, it is possible to prevent the increase in temperature of the polarizing plate caused by absorption of an unnecessary polarized beam, and to substantially simplify and miniaturize a cooling device for cooling the polarizing plate. A liquid crystal device may be used as the modulating device.

According to the above structure, an incident beam is initially separated into a plurality of intermediate beams and the intermediate beams are finally superimposed on the modulating device. Therefore, even if the light distribution of the light emitted from the light source is very imbalanced in the cross section thereof, it is possible to obtain as illumination light polarized beams that are uniform in brightness and color. Consequently, it is possible to achieve a compact display apparatus capable of producing a display that is bright and uniform in brightness and color.

Aprojection display apparatusprojectorin accordance with the present invention comprises a light source, a first optical element for separating a light beam emitted from the light source into a plurality of intermediate beams, a second optical element disposed near the position where the intermediate beams converge, a modulating device for modulating a light beam emitted from the second optical element, and a projection optical system for projecting the light beam modulated by the modulating device onto a projection plane, wherein the second optical element has a condenser lens array that includes a plurality of condenser lenses for respectively condensing the intermediate beams, a polarizing separation element for spatially separating each of the intermediate beams into an S polarized beam and a P polarized beam, a selective phase plate for aligning the polarization direction of one of the S and P polarized beams separated by the polarizing separation element with the polarization direction of the other polarized beam, and a superimposing lens for superimposing the polarized beams, the polarizing separation element has a polarizing separation plane for separating the P and S polarized beams by transmitting one of the polarized beams therethrough and reflecting the other polarized beam and a reflecting plane located almost in parallel with the polarizing separation plane to reflect the polarized beam reflected by the polarizing separation plane toward the emergent direction of the polarized beam transmitted through the polarizing separation plane, and at least one of a shading means and an optical attenuating means for preventing each of the intermediate beams from directly entering the reflecting plane is interposed between the first optical element and the polarizing separation element.

By adopting the above structure, theprojection display apparatusprojectorof the present invention can effectively prevent a phenomenon in which other polarized beams polarized in a different direction mix into polarized beams of almost the same type polarized in the same direction. Therefore, when a polarizing plate is used to obtain a required polarized beam to be modulated by the modulating device, it is possible to prevent the increase in temperature of the polarizing plate caused by absorption of an unnecessary polarized beam, and to substantially simplify and reduce the size of a cooling device for cooling the polarizing plate. A liquid crystal device may be used as the modulating device.

According to the above structure, an incident beam is initially separated into a plurality of intermediate beams and the intermediate beams are finally superimposed on the modulating device. Therefore, even if the intensity distribution of the light emitted from the light source is very imbalanced in the cross section thereof, it is possible to obtain as illumination light polarized beams that are uniform in brightness and color. Consequently, it is possible to achieve a compact display apparatus capable of producing a display that is bright and uniform in brightness and color.

Theprojection display apparatusprojectorfurther comprises a color light separation means for separating the light beam emitted from the second optical element into a plurality of colored lights, a plurality of modulating devices for respectively modulating the colored lights, and a colored light synthesizing means for synthesizing the colored lights modulated by the modulating devices, wherein a synthesized beam synthesized by the colored light synthesized means is projected onto the projection plane through the projection optical system. Since exclusive modulating devices can be placed respectively for more than two separated colored lights, it is possible to achieve a compactprojection display apparatusprojectorcapable of projecting and displaying a color image that is bright and has a high color reproducibility and a high resolution.

In the aboveprojection display apparatusprojector, the modulating device may be formed of a reflection-type liquid crystal device. In general, the reflection-type liquid crystal device provides the advantage of easily obtaining a relatively high aperture ratio even if pixel density is increased. Therefore, adopting of the above structure makes it possible to achieve a compactprojection display apparatusprojectorcapable of projecting and displaying a color image that is bright and has a high color reproducibility and a high resolution.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Modes for carrying out the present invention will be described below in connection with embodiments and with reference to the drawings. In the following embodiments, three directions orthogonal to one another are, for the sake of convenience, taken as an X direction (lateral direction), a Y direction (longitudinal direction), and a Z direction, unless otherwise stated. Although S polarized beams are obtained as the same type of polarized beams of the same type from randomly polarized beams in any of the embodiments, of course. P polarized beams may be obtained. Moreover, in the embodiments that will be described below, sections that have substantially the same functions and structure are denoted by the same numerals, and a description thereof is omitted.

First Embodiment

FIG. 1is a schematic structural plan view of the principal part of a polarizing illumination device according to a first embodiment.FIG. 1is a plan view in the XZ plane which passes through the center of a first optical element200which will be described later. The polarizing illumination device1of this embodiment generally comprises a light source section10and a polarized light generation device20that are arranged along a system optical axis L. Light beams emitted from the light source section10and polarized in random directions (hereinafter referred to as randomly polarized beams) are converted by the polarized light generating device20into the same type of polarized beams that are polarized in almost the same direction, and directed to an illumination region90.

The light source section10generally comprises a light source lamp101and a parabolic reflector102. Light radiated from the light source lamp is reflected by the parabolic reflector102in one direction, and made incident on the polarized light generating device20in the form of almost parallel light beams. The light source section10is placed so that a light source optical axis R thereof is shifted in parallel from the system optical axis L by a required distance D in the X direction.

The polarized light generating device20comprises a first optical element200and a second optical element300.

The first optical element200, as outwardly shown inFIG. 2, includes a matrix of a plurality of beam splitting lenses201each having a rectangular outline in the XY plane. The positional relationship between the light source section10and the first optical element200is set so that the light source optical axis R aligns with the center of the first optical element200. Light that is incident on the first optical element200is split into a plurality of intermediate beams202by each beam splitting lens201, and simultaneously, the same number of condensed images203as that of the beam splitting lenses are formed, by a condensing action of the beam splitting lenses, at positions in a plane (the XY plane inFIG. 1) perpendicular to the system optical axis L, where the intermediate beams coverage. The outline of each beam splitting lens201in the XY plane is set so that it is similar to that of the illumination region90. Since it is assumed that the illumination region in this embodiment extends laterally in the X direction in the XY plane, the outline of the beam splitting lens201in the XY plane is also extended laterally.

The second optical element300is a complex that generally includes a condenser lens array310, a shading plate370, a polarizing separation until array320, a selective phase plate380, and a superimposing lens390, and is placed in a plane (the XY plane inFIG. 1) perpendicular to the system optical axis L near the positions where the condensed images203are formed by the first optical element200. When the light beams that are incident on the first optical element200are extremely parallel, the condenser lens array310does not have to be included in the second optical element. The second optical element300operates to spatially separate each intermediate beam202into a P polarized beam and an S polarized beam, aligns the polarization direction of one polarized beam and that of the other polarized beam, and directs the beams polarized in substantially the same direction to one point in the illumination region90.

The condenser lens array310has almost the same structure as the first optical element200, that is, it comprises a matrix of the same number of condenser lenses311as that of the beam splitting lenses201of the first optical element200. The condenser lens array310operates to condense and direct each intermediate beam to a specific position in the polarizing separation unit array320. Therefore, it is preferable to optimize the lens properties of the condenser lenses in accordance with the properties of the intermediate beams202formed by the first optical element200, and considering that the ideal placement of the principal ray of the light incident on the polarizing separation unit array320is parallel with the system optical axis L. Generally, in consideration of cost reduction and easy design of the optical system, an element entirely identical with the first optical element200may be used as the condenser lens array310, or a condenser lens array that includes condenser lenses similar in shape to the beam splitting lenses201in the XY plane may be used. Therefore, in this embodiment, the first optical element200is used as the condenser lens array310. The condenser lens array310may be placed apart from the shading plate370and the polarizing separation unit array320(on the side closer to the first optical element200).

The shading plate370, as outwardly shown inFIG. 3, includes an array of a plurality of shading surfaces371and a plurality of open surfaces372. The shading surfaces371and the open surfaces372are arranged in a manner corresponding to the arrangement of polarizing separation units330which will be described later. Four broken lines parallel with the X axis on the shading plate370inFIG. 3are drawn to explain the correspondence to the polarizing separation unit array which will be described later. This also applies to a reflecting plate373shown inFIG. 6 and alight diffusing plate376shown in FIG.7. Light beams that are incident on the shading surfaces371of the shading plate370are blocked, and light beams that are incident on the open surfaces372pass through the shading plate370unchanged. Therefore, the shading plate370operates to control the light beams in accordance with the positions thereon where the light beams transmit, and the shading surfaces371and the open surfaces372are arranged so that the condensed images203are respective formed by the first optical element200only on polarizing separation planes331of the polarizing separation units330which will be described later. A flat transparent member, such as a glass plate, partially provided with opaque films made of chrome, aluminum or similar materials as in this embodiment, an opaque flat plate, such as an aluminum plate, provided with open sections, and similar structures may be used as the shading plate370. Particularly, when opaque films are used, even if they are directly formed on the condenser lens array310or the polarizing separation unit array320, which will be described later, it is possible to provide similar functions.

The polarizing separation unit array320, as outwardly shown inFIG. 4, includes a matrix of a plurality of polarizing separation units330. The polarizing separation units330are arranged corresponding to the lens properties and arrangement of the beam splitting lenses201which form the first optical element200. Since the first optical element200include the concentric beam splitting lenses201which all have the same lens properties and are arranged in a rectangular matrix in this embodiment, the polarizing separation unit array320also includes all the same polarizing separation units320which are arranged in the same direction and in a crossed matrix. When the polarizing separation units aligned in the Y-direction column are of all the same type, it is preferable that the polarizing separation unit array320include polarizing separation units which are long in the Y direction and are arranged in the X direction, which is advantageous in reducing light losses at the interfaces between the polarizing separation units and in reducing the production cost of the polarizing separation unit array.

Each polarizing separation unit330is, as outwardly shown inFIG. 5, a member shaped like a quadrangular prism and provided with a polarizing separation plane331and a reflecting plane332therein, and operates to spatially separate each intermediate light beam, that enters the polarizing separation unit, into a P polarized beam and an S polarized beam. The outline of the polarizing separation unit330in the XY plane is similar to that of the beam splitting lens201in the XY plane, that is, it is shaped like a rectangular which is extended laterally. Therefore, the polarizing separation plane331and the reflecting plane332are placed so that they are arranged in the lateral direction (the X direction). The polarizing separation plane331and the reflecting plane332are placed so that the polarizing separation plane331inclines at about 45° with respect to the system optical axis L, the reflecting plane332is parallel to the polarizing separation plane331. The projection area of the polarizing separation plane331in the XY plane (that is equal to the area of a P emergent surface333described later) and the projection area of the reflecting plane332in the XY plane (that is equal to the area of an S emergent surface334described later) are equal to each other. Therefore, in this embodiment, a width Wp of a region in the XY plane, where the polarizing separation plane331exists, and a width Wm of a region in the XY plane, where the reflecting plane332exists, are equally set so that they are each half a width W of the polarizing separation unit in the XY plane. In general, the polarization separation plane331may be made of a dielectric multilayer film, and the reflecting plane332may be made of a dielectric multilayer film or an aluminum film.

Light incident on the polarizing separation unit330is separated by the polarizing separation plane331into a P polarized beam335that transmits through the polarizing separation plane331without changing its direction of travel and an S polarized beam336that is reflected by the polarizing separation plane331and changes its direction of travel toward the adjoining reflecting plane332. The P polarized beam335is emitted from the polarizing separation unit through the P emergent surface33unchanged, and the S polarized beam336again changes its direction of travel at the reflecting plane332, and is emitted from the polarizing separation unit through the S emergent surface334substantially parallel with the P polarized beam335. Therefore, randomly polarized beams incident on the polarizing separation unit330are separated into two types of polarized beams polarized in different directions, the P polarized beam335and the S polarized beam336, and are emitted substantially the same direction from different sections of the polarizing separation unit (the P emergent surface333and the S emergent surface344). Since the polarizing separation unit has the above-mentioned functions, it is necessary to lead each intermediate beam202to the region of the polarizing separation unit330where the polarizing separation plane331exists. Accordingly, the positional relationship between each polarizing separation unit330and each condenser lens311and the lens properties of the condenser lens311are set so that the intermediate beam enters the center of the polarizing separation plane in the polarizing separation unit. Particularly, in this embodiment, the condenser lens array310is placed offset from the polarizing separation unit array320by the distance D, which corresponds to ¼ of the width W of the polarizing separation unit, in the X direction so that the center axis of each condenser lens aligns with the center of the polarizing separation plane331in each polarizing separation unit330.

Any polarizing separation unit array may be used as long as the above-mentioned polarizing separation planes and reflecting planes are regularly formed therein, and it is not always necessary to use the above-mentioned polarizing separation units as basic constituents. Herein, the polarizing separation units are discussed as constituents only to explain the function of the polarizing separation unit array.

Description will be made again with reference to FIG.1.

The shading plate370is interposed between the polarizing separation unit array320and the condenser lens array310so that the center of each open surface372of the shading plate370is substantially aligned with the center of the polarizing separation plane331of each polarizing separation unit330. The opening width of the open surface372(the opening width in the X direction) is set about half the width W of the polarizing separation unit330. As a result, since intermediate beams are previously blocked by the shading surface371of the shading plate370, there are few beams that directly enter the reflecting plane332without passing through the polarizing separation plane331, and most of the light beams passed through the open surface372of the shading plate370enter only the polarizing separation plane331. Consequently, because of such placement of the shading plate370, few light beams directly enter the reflecting planes332and enter the adjoining polarizing separation planes331through the reflecting planes332in the polarizing separation unit.

The selective phase plate380, in which λ/2 phase plates381are regularly arranged, is placed on the emergent side of the polarizing separation unit array320. That is, the λ/2 phase plates381are respectively placed only at the P emergent surfaces333of the polarizing separation units330which form the polarizing separation unit array320, and no λ/2 phase plates381are placed at the S emergent surfaces334(see FIG.5). According to such an arrangement of the λ/2 phase plates381, when P polarized beams emitted from the polarizing separation units330respectively pass through the λ/2 phase plates381, they are conventional into S polarized beams by a polarization direction rotation action. On the other hand, since S polarized beams emitted from the S emitting surfaces334do not pass through the λ/2 phase plates381, they do not change their polarization direction and pass through the selective phase plate380unchanged. In summary, intermediate beams polarized in random directions are converted into polarized beams of the same type (in this case, the S polarized beams) by the polarizing separation unit array320and the selective phase plate380.

The superimposing lens390is placed on the emitting side of the selective phase plate380. The light beams, which are converted into the S polarized beams by the selective phase plate380, are directed to the illumination region90by the superimposing lens390and superimposed on the illumination region. The superimposing lens390is not limited to a single lens member, and it may be an assembly of a plurality of lenses like the first optical element200.

To summarize the operations of the second optical element300, the intermediate beams202separated by the first optical element200(that is, image planes cut out by the beam splitting lenses201) are superimposed on the illumination area90by the second optical element300. At the same time, the intermediate beams, which are randomly polarized beams, are spatially separated into two types of polarized beams polarized in different directions by the polarizing separation unit array320placed in the path, and converted into substantially one type of polarized beams when they pass through the selective phase plate380. Since the shading plate370is placed on the incident side of the polarizing separation unit array320and the intermediate beams are thereby allowed to enter only the polarizing separation planes331in the polarizing separation units330, few intermediate beams enter the polarizing separation planes331through the reflecting planes332, and therefore, the polarized beams emitted from the polarizing separation unit array320are limited to substantially one type. Consequently, the illumination region90is illuminated substantially uniformly with substantially one type of polarized beams.

As described above, the polarizing illumination device1of this embodiment is advantageous in that randomly polarized beams emitted from the light source section10are converted into substantially one type of polarized beams by the polarized light generating device20that includes the first optical element200and the second optical element300, and the illumination region90can be illuminated uniformly with the light beams polarized in the same direction. Moreover, since the process of generating the polarized beams accompanies little loss of light, almost all the light emitted from the light source section can be directed to the illumination region90, which provides extremely high light use efficiency. Furthermore, since the shading plate370is placed in the second optical element300, other beams polarized in a different direction rarely mix into polarized beams of the same type for illuminating the illumination region90. Therefore, when the polarizing illumination device of the present invention is used as a device for illuminating a modulating device that produces a display using polarized beams such as a liquid crystal device, it is possible to obviate a polarizing plate which is conventionally placed on the side of the modulating device where the illumination light enters. Even if the polarizing plate is placed as is conventionally done, since the amount of light absorbed by the polarizing plate is extremely small, it is possible to substantially reduce the size of a cooling device that is needed to minimize heat generation of the polarizing plate and the modulation device. As mentioned above, the size of the condensed images203formed by the first optical element200is influenced by the parallelism of light beams that enter the first optical element (light beams emitted from the light source in the illumination device). When parallelism is low, since only a large condensed image can be formed, a large number of intermediate beams directly enter the reflecting planes without passing the polarizing separation planes in the polarizing separation units, and therefore, a phenomenon in which other beams polarized in a different direction mix into the illumination beams is inevitable. Accordingly, the structure of the polarizing illumination device of the present invention has a great effect, particularly in adopting a light source for emitting light beams having low parallelism in the apparatus.

In this embodiment, the condenser lens array310, the shading plate370, the polarizing separation unit array320, the selective phase plate380, and the emergent-side lens390, which form the second optical element300, are optically integrated, so that light losses caused at interfaces therebetween are reduced, and the light use efficiency is further enhanced. Although it is not always necessary to optically integrate these optical elements, it is preferable to optically integrate or fix the shading plate370on the light incident surface of the polarizing separation unit array320in order to effectively prevent other beams polarized in a different direction from mixing into the illumination light. As a method of optically integrating the shading plate370with the light incident surface of the polarizing separation unit array320, it is possible to stick the shading plate370to the light incident surface of the polarizing separation unit array320with an adhesive layer, or to directly form the shading surfaces371on the light incident surface of the polarizing separation unit array320as will be described later. On the other hand, as a method of fixing the shading plate370on the light incident surface of the polarizing separation unit array320, it is possible to stick the peripheral portion of the shading plate370on the peripheral portion of the light incident surface of the polarizing separation unit array320by using a double-sided tape or similar device. In this situation, it is necessary to stick the entire peripheral portion of the shading plate370, and the peripheral portion only has to be stuck at at least two points. In order to fix the shading plate370parallel with the light incident surface of the polarizing separation unit array320, it is preferable to set the sticking points so that they are almost symmetrical with respect to the center point of the shading plate370.

Furthermore, the beam splitting lenses201which form the first optical element200each extend laterally in accordance with the shape of the illumination region90like a laterally extended rectangle, and at the same time, two types of polarized beams emitted from the polarizing separation unit array320are separated in the lateral direction (the X direction). This makes it possible to enhance illumination efficiency (light use efficiency) without wasting the light even in illuminating the illumination region90which is shaped like a laterally extended rectangle.

In general, when light beams polarized in random directions are merely separated into P polarized beams and S polarized beams, the overall width of the separated beams doubles, which increases the size of the optical system. The polarizing illumination device of the present invention, however, forms a plurality of minute condensed images203through the first optical element200, effectively uses the spaces provided in the formation process where no light exists, and respectively places the reflecting planes332of the polarization separation units330in the spaces, thereby absorbing the lateral widening of the beams caused by the separation into two types of polarized beams. As a result, the overall width of the beams does not increase, and a compact optical system can be achieved.

First Modification of First Embodiment

In the first embodiment, the shading surfaces371that form the shading plate370may be replaced with reflecting planes for reflecting light in almost the opposite direction. That is, a reflecting plate373that includes a plurality of reflecting surfaces374and a plurality of open surfaces375, as shown inFIG. 6, may be adopted instead of the shading plate370in the first embodiment. The reflecting surfaces374each can easily be formed of a dielectric multilayer film, a thin film made a metal having high reflectivity, such as silver or aluminum, or a combination thereof, and an extremely high reflectivity of more than ninety percent can be obtained depending on the type of the film. Even if the reflecting surfaces374are directly formed on the condenser lens array310or the polarizing separation unit array320shown inFIG. 1, similar functions are provided.

As opposed to the shading surfaces371, the reflecting surfaces374hardly absorb light. Therefore, the adoption of the reflecting plate373can prevent peripheral optical elements from being thermally influenced by heat generation thereof. In addition, the light reflected by the reflecting surfaces374and reflected by the parabolic reflector102placed in the light source section10, can make enter again into the polarized light generating device20and lead into the open sections375of the reflecting plate373. Then it is possible to efficiently use the light from the light source without waste.

Second Modification of First Embodiment

In the first embodiment, even if the shading surfaces for forming the shading plate are replaced with light diffusing surfaces for diffusing light, almost the same advantages as those obtained by the shading surfaces can be provided. That is, in the first embodiment, a light diffusing plate376that includes an arrangement of a plurality of light diffusing surfaces377and a plurality of open surfaces378, as shown inFIG. 7, may be adopted instead of the shading plate370. Since light incident on the light diffusing surface377is diffused, it is possible to substantially reduce the intensity of light that directly enters the reflecting plane without passing through the polarizing separation plane of the polarizing separation unit, and to effectively prevent a phenomenon in which other beams polarized in a different direction mix into illuminating beams including substantially the same type of polarized beams that are polarized in the same direction. Each light diffusing surface377can easily be realized by forming a light diffusing member on or inside a flat transparent substrate, making the surface of the transparent substrate uneven, or merely roughening the surface thereof. Even if the light diffusing surfaces377are directly formed on the condenser lens array310or the polarizing separation unit array320shown inFIG. 1, similar functions can be provided.

Adopting the light diffusing plate376makes it possible to reduce the cost compared with adopting the shading plate370and the reflecting plate373using dielectric multilayer films, metal thin films, or similar materials.

Third Modification of First Embodiment

Although the shading plate370, the reflecting plate373and the light diffusing plate376in the first embodiment and the above-mentioned first and second modifications are each an optical element that is physically independent from the condenser lens array310and the polarizing separation unit array320located in front and in the rear thereof, even if the shading surface371for forming the shading plate370, the reflecting surfaces374for forming the reflecting plate373, or the light diffusing surfaces377for forming the light diffusing plate376are directly formed on the light incident surfaces of the polarizing separation units330for forming the polarizing separation unit array320, the same advantages as those obtained in the use of these optical elements can be obtained.

This modification will be specifically described with reference to FIG.8. In a polarizing separation unit array320A whose outward appearance is shown inFIG. 8, shading surfaces321are directly formed on light incident surfaces of polarizing separation units330A which form the polarizing separation unit array320A, and regions322where no shading surfaces are formed correspond to the open surfaces372of the above-mentioned shading plate370for transmitting light therethrough. When the polarizing separation unit array320A having the shading surfaces321directly formed thereon is used as in this modification, since there is no need to use the shading plate370as a physically independent optical element, it is possible to reduce the size and cost of the second optical element. Of course, reflecting surfaces of light diffusing surfaces may be directly formed on the polarizing separation units330A instead of the shading surfaces321, and this situation provides the same advantages as those of this modification.

Fourth Modification of First Embodiment

Although the shading plate370, the reflecting plate373and the light diffusing plate376in the first embodiment and the above-mentioned first and second modifications are each an optical element that is physically independent from the condenser lens array310and the polarizing separation unit array320located in front and in the rear thereof, even if the shading surfaces371for forming the shading plate370, the reflecting surfaces373for forming the reflecting plate373, or the light diffusing surfaces374for forming the light diffusing plate376are directly formed on the condenser lenses311for forming the condenser lens array310, the same advantages as those in the use of these optical elements can be obtained.

This modification will be specifically described with reference to FIG.9. In a condenser lens array310A whose outward appearance is shown inFIG. 9, shading surfaces312are directly formed on surfaces of condenser lenses311A for forming the condenser lens array310A from which light is emitted, and regions313where no shading surfaces are formed correspond to the open surfaces372of the above-mentioned shading plate370for transmitting light therethrough. When the condenser lens array310A having the shading surfaces312directly formed thereon is used as in this modification, since there is no need to use the shading plate370as a physically independent optical element, it is possible to reduce the size and cost of the second optical element. Of course, reflecting surfaces or light diffusing surfaces may be directly formed on the condenser lenses311A instead of the shading surfaces312of this modification, and this case provides the same advantages as those of this modification. In this modification, if the condenser lens array310A is placed spatially apart from the polarizing separation unit array and the selective phase plate that are other optical elements for forming the second optical element, it is possible to prevent the optical elements from being influenced by heat generation resulting from light absorption by the shading surfaces, the reflecting surfaces, and the light diffusing surfaces.

Fifth Modification of First Embodiment

Although a flat transparent member like a glass plate is partially provided with opaque films made of chrome, aluminum, or similar material in the shading plate370of the first embodiment, an opaque flat plate such as an aluminum plate may be provided with open sections.

This modification will be specifically described with reference to FIG.10. In a shading plate370A whose outward appearance is shown inFIG. 10, an opaque flat plate371A is provided with open sections372A. When the shading plate370A is fixed on the light incident surface of the polarizing separation unit array320in order to effectively prevent other beams polarized in a different direction from mixing into the illumination light, two sticking points379a and379b on the peripheral section of the shading plate371A are fixed on the light incident surface of the polarizing separation unit array230with double-sided tapes. Since the sticking points379a and379b are positioned so that they are almost symmetrical with respective to the center point of the shading plate370A, the shading plate370A is allowed to be fixed in parallel with the light incident surface of the polarizing separation unit array320.

When the shading plate370A having the opaque flat plate371A, such as an aluminum plate, provided with the open sections372A is used as in this modification, it is possible to reduce the costs compared with the shading plate370in which a flat transparent member, such as a glass plate, is partially provided with opaque films made of chrome, aluminum, or similar material.

Second Embodiment

A description will be given of a direct-view display apparatus in which the polarizing illumination device1of the first embodiment is incorporated. In this embodiment, a transmission-type liquid crystal device is used as a modulating device for modulating light beams emitted from the polarizing illumination device according to display information.

FIG. 11is a schematic structural view showing the principal part of an optical system of a display apparatus2according to this embodiment, and shows the sectional structure in the XZ plane. The display apparatus2of this embodiment roughly comprises the polarizing illumination device1shown described in the first embodiment, a reflecting mirror510, and a liquid crystal device520.

The polarizing illumination device1has a light source section10for emitting randomly polarized beams in one direction, and the randomly polarized beams emitted from the light source section10are converted into substantially the same type of polarized beams by a polarized light generating device20. The reflecting mirror510turns the light traveling direction of the polarized beams emitted from the polarizing illumination device1by about 90°. The liquid crystal device520is illuminated with substantially the same type of polarized beams. Polarizing plates521are placed in front of and behind the liquid crystal device520. A light diffusing plate (not shown) maybe placed before the liquid crystal device520(on the side of the reflecting mirror510) for the purpose of improving the angle of view.

The display apparatus2having such a structure employs a liquid crystal device for modulating the same type of polarized beams. Therefore, if randomly polarized beams are directed to the liquid crystal device by using a conventional illumination device, about half the randomly polarized beams are absorbed by the polarizing plates521and turned into heat, whereby the light use efficiency is low. The display apparatus2of this embodiment, however, substantially improves such a problem.

In the polarizing illumination device1of the display apparatus2according to this embodiment, only one type of polarized beams, for example, P polarized beams, are subjected to a rotary polarization action by the λ/2 phase plate, and the polarization direction thereof is made identical with that of the other type of polarized beams, for example, S polarized beams. Since substantially the same type of polarized beams, which are polarized in the same direction, are directed to the liquid crystal device520, the amount of light to be absorbed by the polarizing plates521is extremely small, which makes it possible to enhance the use efficiency of the source light, and to thereby obtain a bright display state.

Particularly, in the polarizing illumination device1used as an illumination device, since the shading plate370is placed inside the second optical element300, other polarized beams which are unnecessary for display on the liquid crystal device rarely mix into the illumination light emitted from the polarizing illumination device1. As a result, the amount of light absorbed by the polarizing plate521placed on the light incident side of the liquid crystals device520is extremely small, and therefore, the amount of heat generated in light absorption is extremely small. Consequently, it is possible to omit a cooling device for minimizing the increase in temperature of the polarizing plate521and the liquid crystal device520, or to substantially reduce the size of the cooling device even if such omission is impossible.

Third Embodiment

A description will be given of a first example of aprojection display apparatusprojectorin which the polarization illumination device1described in the first embodiment is incorporated. In this embodiment, a transmission-type liquid crystal device is used as a modulating device for modulating light beams emitted from the polarizing illumination device according to display information.

FIG. 12is a schematic structural view showing the principal part of an optical system of aprojection display apparatusprojector3according to this embodiment, and shows the sectional structure in the XZ plane. Theprojection display apparatusprojector3of this embodiment generally comprises the polarizing illumination device1described in the first embodiment, a colored light separating means for separating a white light beam into three colored lights, three transmission-type liquid crystal devices for modulating the colored lights according to display information and thereby forming display images, a colored light synthesizing means for forming a color image by synthesizing the three colored lights, and a projection optical system for projecting and displaying the color image.

The polarizing illumination device1of this embodiment has a light source section10for emitting randomly polarized beams in one direction, and the randomly polarized beams emitted from the light source section10are converted into substantially the same type of polarized beams by a polarized light generating device20.

First, the red light of the light emitted from the polarizing illumination device1transmits through a blue-green reflecting dichroic mirror401serving as the colored light separating means, and the blue light and the green light are reflected. The red light is reflected by a reflecting mirror403and reaches a liquid crystal device411for red light. On the other hand, the green light of the blue and green lights is reflected by a green reflecting dichroic mirror402that also serves as the colored light separating means, and reaches a liquid crystal device412for green light.

Since the blue light has the longest optical path of the colored lights, a light guide means430formed of a relay lens system comprising an incident lens431, a relay lens432, and an emergent lens433is provided for the blue light. That is, after transmitting through the green reflecting dichroic mirror402and the incident lens431, the blue light is first reflected by a reflecting mirror435, and directed to and focused onto the relay lens432. After being focused onto the relay lens, the blue light is directed to the emergent lens433by a reflecting mirror436, and then, reaches a liquid crystal device413for blue light. The liquid crystal devices411,412, and413located at three positions respectively modulate the colored lights so that the colored lights contain corresponding image information, and make the modulated colored lights enter a crossed dichroic prism450serving as the colored light synthesizing means. The crossed dichroic prism450includes a dielectric multilayer film for reflecting red light and a dielectric multilayer film for reflecting blue light which are crossed in the form of X, and synthesizing the modulated light beams, thereby forming a color image. The color image formed therein is enlarged and projected onto a screen470by a projection lens460serving as the projection optical system, so that a projection image is formed.

Theprojection display apparatusprojector3having such a structure employs the liquid crystal devices each for modulating one type of polarized beam. Therefore, if randomly polarized beams are directed to the liquid crystal device by using a conventional illumination device, about half of them are absorbed by a polarizing plate (not shown) and turned into heat. Therefore, the light use efficiency is low, and there is a need for a large and noisy cooling device for minimizing heat generation of the polarizing plate. Theprojection display apparatusprojector3of this embodiment, however, substantially improves such problems.

In the polarizing illumination device1of theprojection display apparatusprojector3according to this embodiment, only one type of polarized beam, for example, a P polarized beam is subjected to the rotary polarization action by a λ/2 phase plate, and the polarization direction thereof is made identical with that of the other type of polarized beam, for example, and S polarized beam. Since substantially the same type of polarized beams, which are polarized in the same direction, are directed to the liquid crystal devices411,412, and413located at three position, the amount of light to be absorbed by the polarizing plate is extremely small, which makes it possible to enhance the light use efficiency, and to thereby obtain a bright projection image.

Particularly, in the polarizing illumination device1used as an illumination device, since the shading plate370is placed inside the second optical element300, other polarized beams which are unnecessary for display on the liquid crystal device rarely mix into the illumination light emitted from the polarizing illumination device1. As a result, the amount of light absorbed by polarizing plates (not shown) respectively placed on the light incident sides of the liquid crystal devices411,412, and413located at three positions is extremely small, and therefore, the amount of heat generated in light absorption is extremely small. Consequently, it is possible to substantially reduce the size of a cooling device for minimizing the increase in temperature of the polarizing plates and the liquid crystal devices. As mentioned above, a small cooling device will do for aprojection display apparatusprojectorcapable of displaying a considerably bright projection image with a considerably high-power light source lamp, which makes it possible to reduce noise of the cooling device, and to thereby achieve a quiet and high-performanceprojection display apparatusprojector.

Furthermore, the polarizing illumination device1spatially separates two types of polarized beams in the lateral direction (the X direction) by the second optical element300. Therefore, the polarizing illumination device1does not waste the light, and is convenient for illuminating a liquid crystal device shaped like a laterally extended rectangle.

As described in connection with the above described first embodiment, the widening of light beams emitted from the polarizing separation unit array320is restricted although the polarizing illumination device1of this embodiment incorporates polarizing conversion optical elements therein. This means that minimal light enters the liquid crystal device at a large angle in illuminating the liquid crystal device. Accordingly, it is possible to achieve a bright projection image without using a projection lens system having a small F-number and an extremely large aperture, and to thereby achieve a compactprojection display apparatusprojector.

Since the crossed dichroic prism450is used as the colored light synthesizing means in this embodiment, it is possible to reduce the size of the apparatus. Furthermore, since the optical paths between the liquid crystal devices411,412, and413, and the projection lens system are short, even if the projection lens system has a relatively small aperture, it is possible to achieve a bright projection image. Still furthermore, though only one of the three optical paths of the colored lights is difficult in length from the others, since the light guide means430formed of a relay lens system comprising the incident lens431, the relay lens432, and the emergent lens433is provided for the blue light having the longest optical path, no color inconsistency arises.

Theprojection display apparatusprojectormay comprise a mirror optical system using two dichroic mirrors as the colored light synthesizing means. Of course, it is also possible in that case to incorporate the polarizing illumination device of this embodiment, and to form a high-quality bright projection image having a high light use efficiency, similarly to this embodiment.

Fourth Embodiment

Another embodiment of aprojection display apparatusprojectorin which the polarizing illumination device1described in the first embodiment is incorporated will be described. In this embodiment, reflection-type liquid crystal devices are used as modulating devices for modulating light beams emitted from the polarizing illumination device according to display information.

FIG. 13is a schematic structural plan view of the principal part of an optical system in aprojection display apparatusprojector4of this embodiment. Theprojection display apparatusprojector4of this embodiment generally comprises the polarizing illumination device1of the first embodiment, a polarizing beam splitter480, a crossed dichroic prism450doubling as the colored light separation means and the colored light synthesizing means, three reflection-type liquid crystal devices414,415, and416serving as modulating devices, and a projection lens460serving as the projection optical system.

The polarizing illumination device1has a light source section10for emitting randomly polarized beams in one direction, and the randomly polarized beams emitted from the light source section10are converted into substantially the same type of polarized beams (S polarized beams in this embodiment) by a polarized light generating device20.

The light beams emitted from the polarizing illumination device1enter into the polarizing beam splitter480, and are reflected by a polarizing separation plane418. Then, the traveling direction of the light beams is changed by approximately 90°. Then, the light beams enter the adjoining crossed dichroic prism450. Although most of the light beams emitted from the polarizing illumination device1are S polarized beams, a few polarized beams polarized in a different direction from the S polarized beams (P polarized beams in this embodiment) sometimes mix, and the light beams polarized in the different direction (the P polarized beams) transmit through the polarizing separation plane481unchanged, and are emitted from the polarizing beam splitter480(these P polarized beams do not serve as illumination light for illuminating the liquid crystal devices.)

The S polarized beams that are incident on the crossed dichroic prism450are separated into three light beams of red, green, and blue by the crossed dichroic prism450in accordance with the wavelength, and the light beams respectively reach the reflection liquid crystal device414for red light, the reflection liquid crystal device415for green light, and the reflection liquid crystal device416for blue light, thereby illuminating the liquid crystal devices. That is, the crossed dichroic prism450acts as the colored light separation means for illumination light for illuminating the liquid crystal devices.

The liquid crystal devices414,415, and416used in this embodiment are of the reflection-type. They modulate respective colored lights, and provide the colored lights with corresponding external display information. At the same time, they respectively change the polarization directions of the light beams emitted from the liquid crystal devices, and almost reverse the direction of travel of the light beams. Therefore, the light beams respectively reflected from the liquid crystal devices are partially brought to a P polarized state according to display information, and then emitted. The modulated light beams emitted from the liquid crystal devices414,415, and416(mainly P polarized beams) enter the crossed dichroic prism450again, are synthesized into one optical image, and enter the adjoining polarizing beam splitter480again. That is, the crossed dichroic prism450acts as the colored light synthesizing means for the modulated light beams emitted from the liquid crystal devices.

Since the light beams modulated by the liquid crystal devices414,415, and416of the light beams that are incident on the polarizing beam splitter480are P polarized beams, they transmit through the polarizing separation plane481of the polarizing beam splitter480unchanged, and form an image on a screen470through the projection lens460.

Theprojection display apparatusprojector4having such a structure also employs liquid crystal devices that each modulate one type of polarized beam, similarly to the above describedprojection display apparatusprojector3. Therefore, when a conventional illumination device for using randomly polarized beams as illumination light is employed, light beams separated by the polarizing beam splitter480and directed to the reflection-type liquid crystal devices are reduced to approximately half the number of the randomly polarized beams, the light use efficiency is low and a bright projection image is difficult to obtain. In theprojection display apparatusprojector4of this embodiment, however, such a problem is substantially improved.

That is, theprojection display apparatusprojector4of this embodiment can efficiently generate substantially the same type of polarized beams, they are polarized in the same direction, by using the polarizing illumination device1of the present invention instead of the conventional illumination device, and therefore, almost all light beams that are incident on the polarizing beam splitter480are directed as illumination light beams to the reflection-type liquid crystal devices414,415, and416located at three positions. As a result, it is possible to obtain a bright projection image that is uniform in brightness and color.

Particularly, in the polarizing illumination device1used as an illumination device, since the shading plate370is placed inside the second optical element300, other polarized beams that are unnecessary for display on the liquid crystal apparatus hardly mix into the illumination light emitted from the polarizing illumination device1. Therefore, it is possible to obtain high-quality illumination light beams polarized in the same direction, and to thereby succeed in obtaining a high-quality bright projection image.

Moreover, the second optical element300in the polarizing illumination device1spatially separates two types of polarized beams in the lateral direction (the X direction). Therefore, the polarizing illumination device1does not waste the light and is convenient for illuminating a liquid crystal device shaped like a laterally extended rectangle.

As described in connection with the above described first embodiment, the widening of light beams emitted from the polarizing separation unit array320is restricted although the polarizing illumination device1of this embodiment incorporates polarizing conversion optical elements therein. This means that minimal light enters the liquid crystal device at a large angle in illuminating the liquid crystal device. Accordingly, it is possible to achieve a bright projection image without using a projection lens system having a small F-number and an extremely large aperture, and to thereby achieve a compactprojection display apparatusprojector.

Condenser lenses417may be respectively interposed between the crossed dichroic prism450and the liquid crystal devices414,415, and416located at three positions in theprojection display apparatusprojector4of this embodiment.FIG. 14shows a schematic structure of an optical system in that situation. Since such placement of these condenser lenses allows illumination light beams from the polarizing illumination device1to be directed to the liquid crystal devices while restricting the widening of the light beams, it is possible to further improve the efficiency in illuminating the liquid crystal devices, and the incident efficiency in making light beams reflected by the liquid crystal devices enter the projection lens460. From the viewpoint of reduction of light losses at the lens interfaces, it is preferable to place each condenser lens integrally with the liquid crystal device as shown inFIG. 14, or with the crossed dichroic prism.

Although S polarized beams are used as illumination light in theprojection display apparatusprojector4of this embodiment. P polarized beams may be used as illumination light. In this case, the polarizing illumination device1and the crossed dichroic prism450are placed opposed to each other through the polarizing beam splitter480.

Furthermore, though the crossed dichroic prism is used as the colored light separation means and the colored light synthesizing means in the embodiment, theprojection display apparatusprojectormay comprise two dichroic mirrors instead. Of course, it is also possible in that case to incorporate the polarizing illumination device of this embodiment, and to form a high-quality bright projection image having a high light use efficiency, similarly to this embodiment.

As described above, according to the present invention, it is possible to achieve a polarizing conversion device and a polarizing illumination device capable of generating with high efficiency only the same type of polarized beams that have a more uniform light intensity distribution in a illumination region than incident light beams, and, at the same, that are polarized in the same direction. Furthermore, it is possible to easily achieve a display apparatus and aprojection display apparatusprojectorcapable of displaying a high-quality bright image through the use of the polarizing conversion device and the polarizing illumination device of the present invention.