Color separation and synthesis systems, color separation systems and color synthesis systems, illumination optical systems, projection optical systems, and projection display devices using the Number:7,438,419 from the United States Patent and Trademark Office (PTO) owispatent

Title: Color separation and synthesis systems, color separation systems and color synthesis systems, illumination optical systems, projection optical systems, and projection display devices using the

Abstract: Color separation and synthesis systems, color separation systems and color synthesis systems, illumination optical systems, projection optical systems, and projection display devices using these systems include a wavelength-splitting element that reflects linearly polarized light of one wavelength and transmits light of another wavelength; a polarization-transforming element that changes the direction of polarization of linearly polarized light of one wavelength and that is arranged adjacent and at least nearly parallel to the wavelength-splitting element; and a polarization-sensitive beam splitter that reflects light having one direction of linear polarization and transmits light with another linear polarization. These systems provide for dividing rind combining three linearly polarized light beams of different wavelengths so that they provide imaging beams to and from display elements, such as LCOSs, that can produce a high quality full color image with fewer optical elements in the various systems and the projection display device.

Patent Number: 7,438,419 Issued on 10/21/2008 to Yamamoto

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Inventors:	Yamamoto; Chikara (Kodaira, JP)
Assignee:	Fujinon Corporation (Saitama, JP)
Appl. No.:	11/785,191
Filed:	April 16, 2007

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Related U.S. Patent Documents

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	Application Number	Filing Date	Patent Number	Issue Date
	10954185	Oct., 2004	7220002

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Foreign Application Priority Data

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Oct 01, 2003 [JP]			2003-343687

Current U.S. Class:	353/20 ; 353/31; 359/634
Current International Class:	G03B 21/14 (20060101)
Field of Search:	353/20,31,33,34,37 349/5,7,8,9 359/490,495,496,501,502,629,634

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References Cited [Referenced By]

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U.S. Patent Documents

5267029	November 1993	Kurematsu et al.
5648870	July 1997	Mistutake
6123424	September 2000	Hayashi et al.
6388718	May 2002	Yoo et al.
6550919	April 2003	Heine
6628346	September 2003	Ebiko
6961045	November 2005	Tsao
7220002	May 2007	Yamamoto
2003/0048421	March 2003	Du

Foreign Patent Documents

	2001-100155		Apr., 2001		JP

Primary Examiner: Dowling; William C.
Attorney, Agent or Firm: Arnold International Henry; Jon W. Arnold; Bruce Y.

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Parent Case Text

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This is a divisional application of allowed U.S. application Ser. No. 10/954,185 filed Oct. 1, 2002 now U.S. Pat. No. 7,220,002, the benefit of priority of which is hereby claimed under 35 U.S.C. 120.

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Claims

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What is claimed is:

1. A color separation and/or synthesis system for receiving at least two incident light beams whose wavelengths are different from each other, comprising: a wavelength-splitting element that reflects light of one wavelength and transmits light of another wavelength; a polarization-transforming element that changes the direction of polarization of linearly polarized light of one wavelength and that is arranged adjacent and at least nearly parallel to the wavelength-splitting element; and a polarization-sensitive beam splitter that reflects light having one direction of linear polarization and transmits light having another direction of linear polarization; wherein the polarization-sensitive beam splitter is arranged adjacent and at least nearly parallel to the wavelength-splitting element; and the color separation and/or synthesis system operates on two linearly polarized light beams of different wavelengths that are incident on the color separation and synthesis system so that one of the linearly polarized light beams is emitted from the color separation and/or synthesis system linearly polarized in a direction that is different than its direction of polarization upon incidence on the color separation and/or synthesis system, and so that one of the linearly polarized beams is emitted from the color separation and/or synthesis system in a different direction than its direction of propagation upon incidence on the color separation and/or synthesis system.

2. A color separation and synthesis system for receiving incident light from different directions and emitting light in different directions, comprising: a wavelength-splitting element that reflects light of one wavelength and transmits light of another wavelength; a polarization-transforming element that changes the direction of polarization of linearly polarized light of one wavelength and that is arranged adjacent and at least nearly parallel to the wavelength-splitting element; and a polarization-sensitive beam splitter that reflects light having one direction of linear polarization and transmits light having another direction of linear polarization; wherein the polarization-sensitive beam splitter is arranged adjacent and at least nearly parallel to the wavelength-splitting element; and the color separation and synthesis system operates on first and second linearly polarized light beams of different wavelengths that are incident on the color separation and synthesis system from one direction and operates on a third linearly polarized beam of a wavelength different from each of said first and second linearly polarized light beams and that is incident on the color separation and synthesis system from another direction so that the first and third linearly polarized light beams are emitted from the color separation and synthesis system in the same direction but with directions of linear polarization that are different from one another, and the second linearly polarized light beam is emitted from the color separation and synthesis system in a direction that is different from said same direction.

3. The color separation and synthesis system of claim 2, wherein the three light beams of different wavelengths are incident on the color separation and synthesis system with the same direction of linear polarization.

4. The color separation and synthesis system of claim 2, wherein at least one of the three light beams passes twice through the polatization-transforming element.

5. The color separation and synthesis system of claim 3, wherein at least one of the three light beams passes twice through the polarization-transforming element.

6. The color separation and synthesis system of claim 2, wherein at least two of the three light beams that are incident on the color separation and synthesis system from directions that are different pass through the polarization-transforming element at least once.

7. The color separation and synthesis system of claim 3, wherein at least two of the three light beams that are incident on the color separation and synthesis system from directions that are different pass through the polarization-transforming element at least once.

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Description

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FIELD OF THE INVENTION

The present invention relates to separation and/or synthesis systems of light beams according to polarization and wavelength characteristics of the light beams. Additionally, the present invention relates to projection display devices that use such systems in their illumination optical systems and/or their projection optical systems and that use light beams that are modulated with image information by display elements for magnified projection, and especially relates to such projection display devices that use reflection-type display elements with polarization changing properties, such as some liquid crystal display elements.

BACKGROUND OF THE INVENTION

In recent years, the projector market has been growing rapidly, along with the use of personal computers. Liquid crystal display elements of the transmission-type and the reflection-type, and DMD display elements which include micromirrors in an orderly array, are known as light valves that modulate light in order to produce image light signals. In particular, an image display device of the reflection-type is suitable to create very small picture elements with high efficiency, and therefore it has gained attention as an image display device for producing a high quality image.

Various projection display devices have been developed that use reflection-type display elements and polarization properties of light beams. For instance, projection display devices that illuminate reflection-type display elements with polarization changes after color separation of the light beams according to wavelengths from a light source by an illumination optical system with a projection optical system that use four polarization-sensitive beam splitters, generally known as a COLORQUAD.TM., and that project imaging light beams from the reflection-type display elements, are known. FIG. 26 and FIG. 27 are cross-sectional diagrams of prior art Example 1 and prior art Example 2 of such devices. In FIG. 26 and FIG. 27, light beam channels corresponding to each of the three primary colors of light are shown as straight lines, and short intersecting lines and the black round shapes shown on these lines indicating the paths of the three light beams indicate one of two polarization states (S polarized light or P polarized light) of each of the light beams at particular locations in the projection display devices. In the following descriptions, the short intersecting lines are called the first polarization state and the black round shapes are called the second polarization state of the light beams.

Light from a light source (not shown), enters from the bottom as shown in FIG. 26 and FIG. 27 (into COLORQUAD.TM. 159 as shown in FIG. 26) as three different colors with their polarization states adjusted to be the same(the first polarization state). The light is separated into light beams of the three primary colors in the color quad 159. The light beams are modulated by the three reflection-type, liquid crystal panels 153a, 153b, and 153c, in particular LCOS (Liquid Crystal On Silicon), that are reflection-type display elements with polarization properties for modulating the light beams of the three primary colors with image information. A light beam that contains the image information of all three colors is synthesized and emitted from the COLORQUAD.TM., projected by the projection optical system 162d, and a full color image is formed on a screen (not shown). Each of the three different light paths shown in FIG. 26 may correspond to any one of the three primary colors blue, green and red in the following description of the operation of the COLORQUAD.TM. 159.

As shown in FIG. 26, in the COLORQUAD.TM. 159, four polarization-sensitive beam splitters (which term may hereinafter be abbreviated as PBSs) 170a, 150a, 150b, and 160a are arranged so that their internal polarization-sensitive filters 171, 151a, 151b, and 161, respectively, are aligned in the shape of the letter X. The first PBS is an illumination light beam separation element 170a; the second PBS is an optical path separation element 150a; the third PBS is an optical path separation element 150b; and the fourth PBS is a projection light beam synthesis element 160a. The COLORQUAD.TM. 159 includes first through third LCOS, 153a, 153b, and 153c, first through fourth wavelength-specific, polarization-transforming elements 143a, 143b, 143c, and 143d, first through third polarizing plates 142a, 142b, and 142c, and quarter-wave plates 152a, 152b, and 152c. Furthermore, in order to improve contrast of the projected image, the following arrangements are made: the polarizing plate 142a adjusts the polarization direction of an incident illumination light beam to the first polarization state; the polarizing plate 142b adjusts the polarization direction of the second color light beam which is incident thereon to the second polarization state; and the polarizing plate 142c adjusts the polarization direction of a projection light beam to the second polarization state. Furthermore, the wavelength-specific, polarization-transforming elements 143a, 143b, and 143d are elements for rotating the direction of linear polarization a specified angle. The wavelength-specific, polarization-transforming elements 143a and 143d transform the second color light beam to the second polarization state from the first polarization state, and the wavelength-specific, polarization-transforming elements 143b and 143c transform the first color light beam to the second polarization state from the first polarization state.

Illumination light beam separation element 170a receives light from the light source (not shown) and interiorly reflects part of the light to optical path separation element 150b and transmits part of the light to optical path separation element 150a, and projection light beam synthesis element 160a receives light from optical path separation elements 150a and 150b to synthesize the light beams to form a projection light beam.

Additionally, in order to achieve improved contrast of a projected image, the following arrangements are made: the polarizing plate 142a adjusts the polarization of the light beam incident on the COLORQUAD.TM. 159 to a light beam in the first polarization state; the polarizing plate 142b assures the direction of linear polarization of a light beam of a second color is in the second polarization state; and the polarizing plate 142c further adjusts the direction of linear polarization of the light beam projected from the COLORQUAD.TM. 159 that includes all three colors is in the second polarization state. Furthermore, each of the wavelength-specific, polarization-transforming elements 143a-143d is designed to rotate the direction of linear polarization of each light beam of a particular color a particular amount. The wavelength-specific, polarization-transforming elements 143a and 143d transform the second color light beam to the second polarization state from the first polarization state, and the wavelength-specific, polarization-transforming elements 143b and 143c transform the first color light beam to the second polarization state from the first polarization state.

With further reference to FIG. 26, the first color light beam is reflected within the illumination light beam separation element 170a, transmitted by optical path separation element 150b, and irradiates the LCOS 153a that modulates the first color light beam. The second color light beam is transmitted through illumination light beam separation element 170a and optical path separation element 150a and irradiates the LCOS 153b that modulates the second color light beam. The third color light beam is reflected within the illumination light beam separation element 170a and then is reflected within the optical path separation element 150b, and irradiates the LCOS 153c that modulates the third color light beam.

Furthermore, the first color light beam is modulated with image information for projection at the first LCOS 153a and becomes a light beam of the first polarization state before it is reflected within optical path separation element 150b and transmitted through projection light beam synthesis element 160a for projection. The second color light beam is reflected as a light beam modulated with image information at the second LCOS 153b and becomes a light beam of the first polarization state before it is reflected within optical path separation element 150a and projection light beam synthesis element 160a. The third color light beam is reflected as a light beam modulated with image information at the third LCOS 153c and becomes a light beam of the second polarization state before it is transmitted by optical path separation element 150band projection light beam synthesis element 160a. Thus, as shown in FIG. 26, the light beams of the three different colors are combined as they are emitted from the COLORQUAD.TM. 159.

It has also been proposed to use only two PBSs in order to improve the contrast of a projection display device while achieving lower cost, lighter weight, and improved polarization properties over a construction with four PBSs.

FIG. 27 shows a projection display device that uses reflection-type display elements, particularly LCOS 153a-153c, each of which is illuminated subsequent to color separation based on wavelengths of light from the illumination light sources. The projection display device of FIG. 27 uses two PBSs in a manner similar to the projection display device of FIG. 26, and light beams containing the image information from the three LCOS 153a-153c related to different wavelengths are similarly projected through the projection optical system 162d. In the projection display device of FIG. 27 a dichroic mirror 170b initially divides the light beams according to color rather than a PBS such as PBS 170a of FIG. 26 that initially divides the light beams according to polarization state. Similarly, in the projection display device of FIG. 27 a dichroic mirror 160b synthesizes the light beams based on wavelength for projection rather than a PBS such as PBS 160a that synthesizes the light beams according to polarization state.

In the projection display device shown in FIG. 26, a total of four wavelength-specific, polarization-transforming elements 143a-143d are present, each of which is either in the illumination optical system (from the light source to the LCOS) or in the projection optical system (from the LCOS to the projection lens), whereas a total of only two wavelength-specific, polarization-transforming elements are arranged in the projection display device of FIG. 27. However, the angle of incidence properties and wavelength selective properties of the wavelength-specific, polarization-transforming elements are not necessarily satisfactory and may be the main causes of deterioration of contrast and deterioration of image formation performance of the projected image.

Concerning these problems, Japanese Laid-Open Patent Application 2001-100155 describes a projection display device that uses two PBSs and does not include any wavelength-specific, polarization-transforming elements. In this publication, a low cost optical system that uses two PBSs is disclosed for a projection display device that uses reflection-type, liquid crystal display elements. This optical system provides separation of a light beam from a light source or device into plural light beams according to wavelengths by a first dichroic mirror and provides a ninety degree rotation of the direction of linear polarization of one of the separated light beams by a polarization-transforming element. This optical system also uses a second dichroic mirror to further separate one of the previously separated light beams according to wavelengths, as well as to synthesize the other of the light beams previously separated by wavelength at the first dichroic mirror with one of the light beams of a different wavelength separated according to wavelengths at the second dichroic mirror. Subsequently, the light beams of the three different wavelengths illuminate different reflection-type, liquid crystal display elements.

The illumination optical system of this projection display device enables two adjacent reflection-type, liquid crystal display elements to be illuminated with light beams of different wavelengths and different polarization states appropriate for operation with an adjacent PBS without using a wavelength-specific, polarization-transforming element while making the entire device compact and decreasing the number of PBSs required. Two light beams having different directions of linear polarization and different wavelengths are emitted in the same direction toward the PBS from the second dichroic mirror that performs both separation and synthesis of various light beams, and th light beam of the other wavelength is emitted in a different direction.

However, there is a problem with this projection display device in that the polarization-transforming element that changes the direction of linear polarization needs to be in relatively close proximity to the light source (namely, in front of the second dichroic mirror), which makes it necessary for the polarization-transforming element to be relatively large.

Additionally, Japanese Laid-Open Patent Application 2001-100155 includes no description of the polarization element used to adjust the polarization direction in the illumination optical system of the projection display device described. However, in order to make a projection display device with a projected image of satisfactory contrast, a polarization element that adjusts the polarization direction is needed in the optical path. Due to the inability to accommodate the polarization element in the optical path where light beams having different polarization directions are present, the polarization element is placed in this optical system closer to the light source than the second dichroic mirror. However, because this position is closer to the light source, the large size of the polarization element and the deterioration of the polarization properties by placing the polarization element far from the PBSs that are adjacent the reflection-type display elements are concerns. It is preferable that the polarization element be arranged closer to the reflection-type display elements and adjacent to the incident side of a PBS.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to color separation and synthesis systems, color separation systems, and color synthesis systems that, through considerations of the required directions of the linearly polarized light and wavelengths of the light beams in such systems, enable an increase in the choices of the arrangements of the optical members and enable enhancing the degree of freedom in the design of these systems, including positioning a polarization-transforming element at a location where it may be relatively small, decreasing the number of wavelength-specific, polarization-transforming elements, and making it possible to position a polarization element adjacent to the incident side of a polarization-sensitive beam splitter, for instance,in an illumination optical system and a projection optical system of a projection display device that uses reflection-type display elements with polarization changing properties. The present invention further relates to color separation and synthesis systems, color separation systems, and color synthesis systems, as well as illumination optical systems and projection optical systems that they may include, systems, and projection display devices including any of such systems, that are compact, of high contrast and with excellent color reproduction, and low in production costs.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given below and the accompanying drawings, which are given by way of illustration only and thus are not limitative of the present invention, wherein:

FIG. 1 is a cross-sectional schematic diagram of the color separation and synthesis system of Embodiment 1 of the present invention;

FIG. 2 is a cross-sectional schematic diagram of the color separation and synthesis system of Embodiment 2 of the present invention;

FIG. 3 is a cross-sectional schematic diagram of the color separation and synthesis system of Embodiment 3 of the present invention;

FIG. 4 is a cross-sectional schematic diagram of the color separation and synthesis system of Embodiment 4 of the present invention;

FIG. 5 is a cross-sectional schematic diagram of the color separation and synthesis system of Embodiment 5 of the present invention;

FIG. 6 is a cross-sectional schematic diagram of a color separation and synthesis system of Embodiment 6 of the present invention;

FIG. 7 is a cross-sectional schematic diagram of a color separation and synthesis system of Embodiment 7 of the present invention;

FIG. 8 is a cross-sectional schematic diagram of a color separation and synthesis system of Embodiment 8 of the present invention;

FIG. 9 is a cross-sectional schematic diagram of a color separation and synthesis system of Embodiment 9 of the present invention;

FIG. 10 is a cross-sectional schematic diagram of a color separation and synthesis system of Embodiment 10 of the present invention;

FIG. 11 is a cross-sectional schematic diagram of a color separation and synthesis system of Embodiment 11 of the present invention;

FIG. 12 is a cross-sectional schematic diagram of a color separation and synthesis system of Embodiment 12 of the present invention;

FIG. 13 is a cross-sectional schematic diagram of a color separation and synthesis system of Embodiment 13 of the present invention;

FIG. 14 is a cross-sectional schematic diagram of a color separation and synthesis system of Embodiment 14 of the present invention;

FIG. 15 is a cross-sectional schematic diagram of a color separation and synthesis system of Embodiment 15 of the present invention;

FIG. 16 is a cross-sectional schematic diagram of a color separation and synthesis system of Embodiment 16 of the present invention;

FIG. 17 is a cross-sectional schematic diagram of a color separation system or color synthesis system of Embodiment 17 of the present invention;

FIG. 18 is a cross-sectional schematic diagram of a color separation system or color synthesis system of Embodiment 18 of the present invention;

FIG. 19 is a cross-sectional schematic diagram of a color separation system or color synthesis system of Embodiment 19 of the present invention;

FIG. 20 is a cross-sectional schematic diagram of a projection display device of Embodiment 20 of the present invention;

FIG. 21 is a cross-sectional schematic diagram of a projection display device of Embodiment 21 of the present invention;

FIG. 22 is a cross-sectional schematic diagram of a projection display device of Embodiment 22 of the present invention;

FIG. 23 is a cross-sectional schematic diagram of a projection display device of Embodiment 23 of the present invention;

FIG. 24 is a cross-sectional schematic diagram of a projection display device of Embodiment 24 of the present invention;

FIG. 25 is a cross-sectional schematic diagram of a projection display device of Embodiment 25 of the present invention;

FIG. 26 is a cross-sectional schematic diagram of a projection display device of prior art Example 1;

FIG. 27 is a cross-sectional schematic diagram of a projection display device of prior art Example 2; and

FIG. 28 is a cross-sectional schematic diagram of a projection display device of prior art Example 3.

DETAILED DESCRIPTION

Color separation and synthesis systems, color separation systems, as well as color synthesis systems, that relate to preferred embodiments of illumination optical systems, projection optical systems and projection-type display devices of the present invention that use such systems will be described with reference to FIGS. 1-28.

In particular, color separation and synthesis systems will first be described with reference to FIGS. 1-16. More specifically, Embodiments 1-4 of the color separation and synthesis systems that pertain to a first mode of the color separation and synthesis systems will first be described with reference to FIGS. 1-4, respectively, then Embodiments 5-14 of the color separation and synthesis systems that pertain to a second mode of the color separation and synthesis system will be described with reference to FIGS. 5-14, respectively, and then Embodiments 15 and 16 of the color separation and synthesis systems that pertain to a third mode of the color separation and synthesis system will be described with reference to FIGS. 15 and 16, respectively. Additionally, FIG. 20, more fully described below, is a cross-sectional schematic diagram of a projection display device that may use color separation and synthesis systems of the present invention as one part of the illumination optical system of a projection display device. The term "systems" will be used in the following descriptions to refer generally to the color separation and synthesis systems, color separation systems, color synthesis systems, illumination optical systems, projection optical system, and even to projection display devices that include these systems, of the present invention and characteristics of the various embodiments of the present invention described herein extend to all the systems disclosed herein to which the embodiments described herein are useful.

Color Separation and Synthesis Systems (Embodiments 1-16)

FIG. 1 is a cross-sectional schematic diagram of Embodiment 1 of the color separation and synthesis systems of the present invention. As shown as 1a in FIG. 1, Embodiment 1 of the color separation and synthesis system of the present invention includes a wavelength-splitting element, which is a dichroic mirror 10a in FIG. 1, that reflects or transmits portions of an incident light beam according to the wavelength of the light and at least one polarization-transforming element, which is a half-wave plate 11a in FIG. 1, that changes the direction of polarization of linearly polarized light of one wavelength and that is arranged adjacent and at least nearly parallel to the wavelength-splitting element. The phrase "arranged adjacent and at least nearly parallel" includes states of the polarization-transforming element and the wavelength-splitting element being superimposed or where they abut one another in a parallel or nearly parallel relationship. The phrase "nearly parallel" encompasses slight variations from parallelism that to at least a first approximation provide the same effects as an exact parallel relationship would provide. A small separation of the polarization-transforming element and the wavelength-splitting element is allowed based on considerations of manufacture. However, the systems will tend to become too large if the separation is too large.

The incident light beam of FIG. 1 includes light of three different wavelengths. In FIG. 1, as well as in FIGS. 2-25, the path of the light beams of each wavelength is shown schematically by straight lines with short intersecting lines and black circles showing the alternative polarization states, either one of the two polarization states (S polarized light and P polarized light) of different polarization direction. Further, in the systems that relate to the present invention, to be described below, and in the color separation and synthesis system 1a, the light beams of the three wavelengths are preferably primary color light beams that are used to create a full color picture image. In particular, light beams of blue, red, and green can correspond in any order to the light beams of three different wavelengths shown in FIG. 1.

As indicated with regard to the three different wavelengths being, for example, blue, red, and green, each light beam of a different wavelength may include light with a band of wavelengths that relate generally to the same color, such as red, blue, or green and is not limited to a monochromatic light beam of only one wavelength. Similarly, as used herein, a light beam of a first, second or third wavelength encompasses a light beam made up of a band of wavelengths that are similarly reflected, transmitted, or have their polarization properties changed by optical elements as described herein.

The color separation and synthesis system of Embodiment 1 is designed for the following operation: the light beams of the first, second, and third wavelengths are variously incident from different directions and undergo color separation and synthesis as shown in FIG. 1. In particular, light beams of the first and third wavelengths are emitted in the same direction linearly polarized in different directions, and a light beam of a second wavelength is emitted in a different direction from which light beams of the first and third wavelengths are emitted.

As shown in FIG. 1, the light beams of the first and second wavelengths are incident from the right side of the page, and the light beam of the third wavelength is incident from the lower side of the page. The color separation and synthesis system 1a undertakes color separation of the light beams of the first and the second wavelengths and also color synthesis of the light beams of the first and third wavelengths; the light beams of the first and third wavelengths are emitted to the left side of the page; and the light beam of the second wavelength is emitted to the upper side of the page. In other words, the dichroic mirror 10a is set so that the light beam of the first wavelength can be transmitted and the light beams of the second and third wavelengths can be reflected.

Furthermore, the light beams of all three wavelengths are in the first polarization state when they are incident to the color separation and syntheses system 1a. Regarding the light beams that are emitted from the color separation and synthesis system 1a, the light beam of the first wavelength is transmitted once through the half-wave plate 11a and emitted in the second polarization state. The light beam of the second wavelength is emitted in the first polarization state without being transmitted through the half-wave plate 11a. The light beam of the third wavelength is transmitted through and back through the half-wave plate so that it is emitted in the first polarization state. In particular, the polarization-transforming element of the present invention is designed to establish a specified optical path length so that when transmitting the light beams that are incident at a specific angle of incidence to this element, the half-wave plate 11a, for example, creates a phase difference of one-half the wavelength of the incident light beam, specifically, for example, an angle of forty-five degrees as shown in FIG. 1.

FIGS. 2-4 show cross-sectional schematic diagrams of Embodiments 2-4 of the color separation and synthesis systems of the present invention, which are referenced by reference numerals 1b-1d in FIGS. 2-4, respectively. The arrangements of Embodiments 2-4 are clear from FIGS. 2-4, respectively, and the description of Embodiment 1 above. Therefore, further detailed descriptions are omitted.

The color separation and synthesis systems 1b-1d are different from the color separation and synthesis system 1a in at least one way with regard to transmission and reflection properties of the dichroic mirrors 10b-10d, the arrangement of the dichroic mirrors 10b-10d and the half-wave plates 11b-11d, and/or the emitting directions of the light beams of the first, second, and third wavelengths.

However, similar operation may be achieved by having the light beams of the first and second wavelengths incident from different directions so that light beams of first and third wavelengths are still emitted in the same direction linearly polarized in different directions, and a light of a second wavelength is still emitted in a different direction from which light beams of the first and third wavelengths are emitted.

Embodiments 1-4 that relate to a first mode of the color separation and synthesis systems of the present invention include the smallest number of wavelength-splitting elements and polarization-transforming elements (namely, one of each, for a total of two such elements), and the light beams of the first, second, and third wavelengths are all incident on the color separation and synthesis systems linearly polarized in the same direction.

Furthermore, among the color separation and synthesis systems 1a-1d of Embodiments 1 through 4 that relate to the first mode, Embodiments 1, 3, and 4 are constructed so that a specified light beam is transmitted through and back through the half-wave plate 11a, 11c, or 11d so that the specified light beam is emitted in the first polarization state, that is, with the same polarization state as the specified light beam is incident on the color separation and synthesis system. Additionally, among the color separation and synthesis systems 1a-1d of Embodiments 1 through 4 that relate to the first mode, Embodiments 1-3 are constructed so that at least two specified light beams incident from different directions are transmitted through the hall-wave plate 11a, 11b, or 11c to be emitted in the same direction and with different polarization states, as shown with regard to light beams of the first and third wavelengths of Embodiment 1. These constructions effectively enable reducing the number of optical elements and increase the degrees of freedom in designing illumination optical systems and projection display devices.

Embodiments 5-14 of the color separation and synthesis systems that pertain to a second mode of the color separation and synthesis systems will now be described with reference to FIGS. 5-14, respectively.

As shown as 2a in FIG. 5, Embodiment 5 of the color separation and synthesis systems of the present invention includes: a wavelength-splitting element, which is a dichroic mirror 10e in FIG. 5, that reflects and transmits portions of an incident light beam according to the wavelength of the light; at least one polarization-transforming element, which is a half-wave plate 11e in FIG. 5, that changes the direction of polarization of linearly polarized light of one wavelength and that is arranged adjacent and at least nearly parallel to the wavelength-splitting element; and a polarization-sensitive beam splitter, which is a reflection-type polarization-sensitive beam splitter 12a in FIG. 5, that reflects or transmits an incident light beam according to the direction of linear polarization of the light beam and that is arranged adjacent and at least nearly parallel to the wavelength-splitting element and the polarization-transforming element.

Similar to Embodiment 1-4 of the first mode, light beams of the first, second, and third wavelengths are variously incident on the color separation and synthesis systems of the second mode in different directions in order to undergo color separation and synthesis. Furthermore, the color separation and synthesis systems of the second mode operate similarly to the systems of the first mode, as follows. In particular, light beams of the first and third wavelengths are emitted in the same direction linearly polarized in different directions, and a light beam of a second wavelength is emitted in a different direction from which light beams of the first and third wavelengths are emitted.

As shown in FIG. 5, the light beams of the first and second wavelengths are incident from the right side of the page, and the light beam of the third wavelength is incident from the lower side of the page. The color separation and synthesis system 2a undertakes color separation of the light beams of the first and the second wavelengths and also color synthesis of the light beams of the first and third wavelengths; the light beams of the first and third wavelengths are emitted to the left side of the page; and the light beam of the second wavelength is emitted to the upper side of the page. In other words, the dichroic mirror 10e is set so that the light beams of the first and third wavelengths are transmitted and the light beam of the second wavelength is reflected.

Furthermore, the light beams of all three wavelengths are in the second polarization state when they are incident onto the color separation and synthesis system 2a. Regarding the light beams that are emitted from the color separation and synthesis system 2a, the incident light beam from the right side of the page of the first wavelength and second polarization state is transmitted by the polarization-sensitive beam splitter 12a, rotated by the half-wave plate 11e to the first polarization state, and then is emitted by the dichroic mirror 10e in the first polarization state. The light beam from the right side of the page of the second wavelength and second polarization state is transmitted through the polarization-sensitive beam splitter 12a, is changed to the first polarization state by the half-wave plate 11e, is reflected by the dichroic mirror 10e, transmits back through the half-wave plate 11e, and subsequently is transmitted again through the polarization-sensitive beam splitter 12a and emitted in the second polarization state toward the top of the page. In other wolds, the polarization-sensitive beam splitter 12a is set so that the light beam of the second polarization state is transmitted and the light beam of the first polarization state is reflected.

FIGS. 6-13 are cross-sectional schematic diagrams of Embodiments 6-13 of the color separation and synthesis systems of the present invention, which are referenced by reference numerals 2b-2i in FIGS. 6-13, respectively. The arrangements of Embodiments 6-13 are clear from FIGS. 6-13, respectively, and the description of Embodiment 5 above. Therefore, further detailed descriptions are omitted.

Operation of Embodiments 6-13 similar to the operation of Embodiment 5 is achieved with respect to light beams of the first, second, and third wavelengths that are variously incident from different directions and that undergo color separation and color synthesis. In particular, light beams of the first and third wavelengths are emitted in the same direction linearly polarized in different directions, and light of a second wavelength is emitted in a different direction from which light beams of the first and third wavelengths are emitted.

The color separation and synthesis systems 2b-2i are different from the color separation and synthesis system 2a in at least one way with regard to the transmission and reflection properties of the dichroic mirrors 10f-10m, the arrangement of the dichroic mirrors 10f-10m and the half-wave plates 11f-11m, the emitting directions of the light beams of the first, second, and third wavelengths, and/or the polarization states of the light beams of the first, second, and third wavelengths at the time of incidence on the color separation and synthesis systems 2b-2i.

However, similar operation may be achieved by having the light beams of the first and second wavelengths incident from different directions so that light beams of the first and third wavelengths are still emitted in the same direction linearly polarized in different directions, and a light beam of a second wavelength is still emitted in a different direction from which light beams of the first and third wavelengths are emitted.

Furthermore, among the color separation and synthesis systems 2a-2i of Embodiments 5-13 that relate to the second mode. Embodiments 5-10, 12, and 13 are constructed so that a specified light beam is transmitted through and back through the half-wave plate 11e-11j, 11l, or 11m so that the specified light beam is emitted with the same polarization state as the specified light beam is incident onto the color separation and synthesis system. Additionally, among the color separation and synthesis systems 2a-2i of the above Embodiments 5-13, Embodiments 5, 9, 10, and 12 are constructed so that at least two specified light beams incident from different directions are transmitted through the half-wave plate 11e, 11i, 11j, or 11l and are emitted in the same direction and with different polarization states, as shown with regard to the light beams of the first and third wavelengths of Embodiment 5. These constructions effectively enable reducing the number of optical elements and increase the degree of freedom in designing illumination optical systems and projection display devices.

FIG. 14 is a cross-sectional schematic diagram of Embodiment 14 of the color separation and synthesis systems of the present invention. FIG. 14 shows color separation and synthesis system 2j of the second mode of the color separation and synthesis systems of the present invention. The polarization-transforming element according to the present invention is not limited to a single half-wave plate as shown in Embodiments 1-13. As shown in FIG. 14, Embodiment 14 includes two quarter-wave plates 13a and 13b as the polarization-transforming element.

In FIG. 14, the light beams of the first and second wavelengths are incident from the right side of the page and the light beam of the third wavelength is incident from the lower side of the page; the light beams of the first and third wavelengths are emitted to the left side of the page, and the light beam of the second wavelength is emitted to the upper side of the page. The dichroic mirror 10n is set so that the light beam of the first wavelength is transmitted and the light beam of the second wavelength is reflected.

Furthermore, the light beams of all three wavelengths are in the first polarization state when they are incident on the color separation and synthesis system 2j. Regarding the light beams that are emitted from the color separation and synthesis system 2j, the light beam of the first wavelength is transmitted through the quarter-wave plates 13a, 13b and the polarization-sensitive beam splitter 12j in that order, and emitted in the second polarization state. The light beam of the second wavelength is transmitted through and back through the quarter-wave plate 13a and is emitted in the second polarization state. The light beam of the third wavelength is reflected at the polarization-sensitive beam splitter 12j and emitted in the first polarization state. This is different from Embodiments 5-13 in that the color separation and synthesis system 2j transforms the polarization state of the light beam of the second wavelength so that it is emitted in a different polarization state than that in which it is incident. The polarization-sensitive beam splitter 12j, similar to Embodiments 5-13, in the color separation and synthesis system 2j of Embodiment 14 is set so that the light beam of the first polarization state is reflected and the light beam of the second polarization state is transmitted.

Similar to Embodiments 5-13, the color separation and synthesis system 2j of Embodiment 14, which includes a plurality of polarization-transforming elements, operates with light beams of the first, second, and third wavelengths variously incident on the color separation and synthesis system from different directions in order to undergo color separation and synthesis. Also, light beams of the first and third wavelengths are emitted in the same direction linearly polarized in different directions, and a light beam of a second wavelength is emitted in a different direction from which light beams of the first and third wavelengths are emitted.

A desirable feature when a plurality of polarization-transforming elements are used is that the number of times each light beam passes through the polarization-transforming element, such as a quarter-wave plate, should be as nearly the same as possible.

In addition, a reflection-type polarization-sensitive beam splitter is used in the second mode of the color separation and synthesis systems. Because the polarization-sensitive beam splitter operates to direct in different directions light beams that are linearly polarized in different directions, when this system is arranged as an optical system or part of a device, there may be instances where linear polarizing functions may be combined with the polarization-sensitive beam splitter in order to simplify the construction of the system or device.

Color separation and synthesis systems of the second mode operate with light beams of first, second, and third wavelengths that are linearly polarized in the same direction and that are variously incident on the color separation and synthesis systems from different directions.

FIG. 15 is a cross-sectional schematic diagram of Embodiment 15 of the color separation and synthesis systems of the present invention that represents a third mode of the color separation and synthesis systems of the resent invention. FIG. 15 shows color separation and synthesis system 3a of Embodiment 15 that includes a wavelength-splitting element, which is a dichroic mirror 10o in FIG. 15, and a polarization-sensitive beam splitter, which is a reflection-type polarization sensitive beam splitter 12k in FIG. 15, that reflects or transmits an incident light beam depending on the direction of linear polarization of the incident light beam and that is arranged adjacent and at least nearly parallel to the wavelength-splitting element.

Similar to the first mode of the color separation and synthesis systems of Embodiments 1-4 described above, in this third mode the light beams of the first, second, and third wavelengths are variously incident on the color separation and synthesis systems from different directions. Furthermore, the color separation and synthesis system 3a undertakes color separation of the light beams of the first and the second wavelengths and also color synthesis of the light beams of the first and third wavelengths, the light beams of the first and third wavelengths are emitted in the same direction with different polarization states, and the light beam of the second wavelength is emitted in a different direction.

In FIG. 15 the light beams of the first and second wavelengths are incident from the right side of the page, and the light beam of the third wavelength is incident from the lower side of the page. The color separation and synthesis system 3a undertakes color separation of the light beams of the first and second wavelengths and also color synthesis of the light beams of the first and third wavelengths; the light beams of the first and third wavelengths are emitted to the left side of the page; and the light beam of the second wavelength is emitted to the upper side of the page. In other words, the dichroic mirror 10o is set so that the light beams of the first and third wavelengths are transmitted and the light beam of the second wavelength is reflected. In addition, the color separation and synthesis system 3a is constructed so that the light beam of the third wavelength is transmitted through and back through the dichroic mirror 10o.

Furthermore, the light beams of the first and second wavelengths are incident on the color separation and synthesis system 3a in the second polarization state, and the light beam of the third wavelength is incident on the color separation and synthesis system 3a in the first polarization state. Regarding the light beams that are emitted from the color separation and synthesis system 3a, the light beam of the first wavelength is transmitted through the reflection-type, polarization sensitive beam splitter 12k and emitted in the second polarization state. The light beam of the second wavelength is transmitted through and back through the reflection-type, polarization-sensitive beam splitter 12k and emitted in the second polarization state. The light beam of the third wavelength is reflected by the reflection-type, polarization-sensitive beam splitter 12k and emitted in the first polarization state. In other words, the reflection-type, polarization-sensitive beam splitter 12k is set so that light beams of the first polarization state are reflected and light beams of the second polarization state are transmitted.

FIG. 16 is a cross-sectional schematic diagram of Embodiment 16 of the color separation and synthesis system 3b of the present invention, which, like Embodiment 15, belongs to a third mode of the color separation and synthesis systems of the present invention. The arrangement of Embodiment 16 is clear from the description of Embodiment 15 above. Therefore, further detailed description is omitted.

As shown in FIG. 16, the color separation and synthesis system 3b of Embodiment 16 is different from the color separation and synthesis system 3a of Embodiment 15 (FIG. 15) in the order of arrangement of the dichroic mirror 10p and the reflection-type polarization sensitive beam splitter 12l, and the dichroic mirror 10p may be set so that the light beam of the first wavelength is transmitted and the light beam of the second wavelength is reflected. However, similar operation may be achieved by having the light beams of the first and second wavelengths incident from different directions so that light beams of the first and third wavelengths are still emitted in the same direction linearly polarized in different directions, and a light beam of a second wavelength is still emitted in a different direction from which light beams of the first and third wavelengths are emitted.

The color separation and synthesis systems of the third mode may be formed with the minimum number of elements, namely a wavelength-splitting element and a polarization sensitive beam splitter, with light beams of first, second, and third wavelengths being variously incident from different directions.

Because of reflection-type polarization sensitive beam splitter is arranged as the polarization splitting plane in the color separation and synthesis system that relates to the third mode in the same manner as in the second mode, when this system is arranged in an optical system or is part of a device, there may be instances where linear polarizing functions may be combined with the polarization sensitive beam splitter in order to simplify the construction of the system or device.

In addition, the color separation and synthesis systems of the present invention described above also have the ability to be used with light paths reversed from those shown in FIGS. 1-16, as generally taught with regard to optical elements, such as lenses. In other words, these systems may be used with light traveling from what is the light emitting side to the light incident side as shown in FIGS. 1-16. In this situation, light beams of the first and third wavelengths are incident from the same direction with their directions of linear polarization being different, and light beams of the first and second wavelengths are emitted with the same direction of linear polarization and in a direction different from the direction in which the light beam of the third wavelength is emitted and the light beam of the second wavelength is incident.

Additionally, in this case, it is preferred that the light beams of the first, second, and third wavelengths that are emitted from the color separation and synthesis systems that relate to the first and the second modes (described above with reference to FIGS. 1-14) be emitted with the same direction of linear polarization. Furthermore, it is preferred that the light beams emitted from the color separation and synthesis systems that relate to the third mode be such that the light beams of the first and second wavelengths have the same direction of linear polarization that is different from the direction of linear polarization of the light beam of the third wavelength.

Color Separation Systems and Color Synthesis Systems (Embodiments 17-19)

Color separation systems and color synthesis systems that relate to preferred embodiments of illumination optical systems, projection optical systems and projection display devices of the present invention that use such systems will now be described with reference to FIGS. 17-19). More specifically, Embodiments 17 and 18 of the present invention, shown in FIGS. 17 and 18, respectively, relate to a first mode of color separation systems, and Embodiment 19 of the present invention, shown in FIG. 19, relates to a second mode of color separation systems.

As shown in FIG. 17, the color separation system 4a of the present invention includes: a wavelength-splitting element, which is a dichroic mirror 10q in FIG. 17, that reflects or transmits portions of an incident light beam according to the wavelength of the light; and a polarization-sensitive beam splitter, which is a reflection-type, polarization sensitive beam splitter 12m in FIG. 17, that reflects or transmits an incident light beam according to its direction of linear polarization and that is arranged adjacent, and at least nearly parallel, to the wavelength-splitting element.

The color separation systems of the first mode, which include Embodiment 17 of the present invention, operate with light beams of different first, second, and third wavelengths but that are incident on the color separation systems from the same direction. The color separation system undertakes color separation of these light beams by emitting the light beams of the first and third wavelengths in the same direction with different directions of linear polarization and emitting the light beam of the second wavelength in a different direction from the direction in which the light beams of the first and third wavelengths are emitted.

As shown in FIG. 17, the light beams of all three wavelengths are incident from the right side of the page. The color separation system 4a undertakes color separation of the light beam of the second wavelength from the light beams of the first and third wavelengths. The light beams of the first and third wavelengths are emitted to the upper side of the page, and the light beam of the second wavelength is emitted to the left side of the page. In other words, the dichroic mirror 10q is set so that the light beam of the first wavelength is reflected and the light beam of the second wavelength is transmitted.

Furthermore, the light beams of the first and second wavelengths that are incident on the color separation system 4a are in the second polarization state, and the light beam of the third wavelength is in the first polarization state. Regarding the light beams that are emitted from the color separation system 4a, the light beam of the first wavelength is transmitted through and back through the reflective-type polarization sensitive beam splitter 12m and emitted in the second polarization state. The light beam of the second wavelength is transmitted once through the reflection-type polarization sensitive beam splitter 12m and emitted in the second polarization state. The light beam of the third wavelength is reflected at the reflection-type polarization sensitive beam splitter 12m and emitted in the first polarization state. In other words, the reflection-type polarization sensitive beam splitter 12m is set so that light beams of the first polarization state are reflected and light beams of the second polarization state are transmitted.

FIG. 18 is a cross-sectional schematic diagram of a color separation system 4b of Embodiment 18 of the present invention that also relates to a first mode of the color separation systems. The arrangement of Embodiment 18 is clear from FIG. 18 and the description of Embodiment 17 above. Therefore, further detailed descriptions are omitted.

The color separation system 4b is different from the color separation system 4a in the order of the dichroic mirror 10r and the reflection-type, polarization-sensitive beam splitter 12n. The dichroic mirror 10r is also set so that the light beam of the first wavelength is reflected and the light beams of the second and third wavelengths are transmitted. However, a similar operation to that of Embodiment 17 is achieved with respect to how the light beams of the first, second and third wavelengths undergo color separation, and the light beams of the first and third wavelengths are emitted in the same direction linearly polarized in different directions while the light beam of the second wavelength is emitted in a different direction from the direction in which the light beams of the first and third wavelengths are emitted. Furthermore, the color separation system 4b is constructed so that the light beam of the third wavelength is transmitted through and back through dichroic mirror 10r.

The first mode of the color separation systems of the present invention may be formed with the minimum number of elements, namely, a wavelength-splitting element and a polarization-sensitive beam splitter, with light beams of first, second, and third wavelengths being incident from the same direction.

FIG. 19 is a cross-sectional schematic diagram of a color separation system 5a of Embodiment 19 of the present invention that a