Optical color separation and synthesis system, and method of constructing optical color separation and synthesis system

An optical color separation and synthesis system is constructed according to a method, in which four first to fourth polarization beam splitters are arranged in such a manner that polarization separating surfaces of the polarization beam splitters form an X-shape, a predetermined gap is formed between facing surfaces of the polarization beam splitters before bonding the polarization beam splitters onto a base platform, and thereafter a frame comprising an opening in a middle portion thereof and a stepped portion to be bonded to an optical function plate in a peripheral portion thereof is secured to any of the first to fourth polarization beam splitters.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to an optical color separation and synthesis system for use in a reflective type projection display apparatus, and a method of constructing an optical color separation and synthesis system.

2. Description of the Related Art

In an optical color separation and synthesis system for use in a projection display apparatus for projecting a color image, white light emitted from a light source unit is separated into light of three primary colors of red (R), green (G), and blue (B), and the three-primary-color light is guided to a corresponding spatial light modulation element of each color. Furthermore, color synthesized light obtained by synthesizing the color of each color light modulated by each color spatial light modulation element according to a video signal is emitted on the side of a projection lens.

As this type of optical color separation and synthesis system, the present applicants have previously proposed an example in which four first to fourth polarization beam splitters are arranged as a plurality of polarization beam splitters in such a manner that polarization separating surfaces of the respective polarization beam splitters form an X-shape as viewed from an upper-surface side. Moreover, if necessary, a wavelength selecting polarization transforming plate is disposed facing any of the first to fourth polarization beam splitters, the first polarization beam splitter is disposed on the side of the light source unit, and the fourth polarization beam splitter is disposed on the side of the projection lens. Then, the spatial light modulation elements of the respective colors corresponding to RGB are disposed facing any surface of the second, third polarization beam splitters (see, e.g., Japanese Patent Application Laid-Open Nos. 2002-228809 and 2002-287094).

In the Japanese Patent Application Laid-Open Nos. 2002-228809 and 2002-287094, although not shown, to construct the optical color separation and synthesis system, all of the four first to fourth polarization beam splitters are integrally bonded beforehand by a light transmitting bonding member (e.g., adhesive). Alternatively, two or three of the four first to fourth polarization beam splitters are integrally bonded beforehand by the light transmitting bonding member (e.g., adhesive). Thereafter, the four first to fourth polarization beam splitters are secured onto a base platform in such a manner that the polarization separating surfaces of the respective polarization beam splitters are arranged in an X-shape as viewed from the upper-surface side.

Additionally, in the Japanese Patent Application Laid-Open Nos. 2002-228809 and 2002-287094, an optical characteristic of the optical color separation and synthesis system is satisfactorily obtained. However, to integrally bond at least two or more polarization beam splitters to each other beforehand by the light transmitting bonding member (e.g., adhesive), the polarization beam splitters are mutually positioned. Moreover, if necessary, the wavelength selecting polarization transforming plate is inserted and integrally bonded between the facing surfaces of the polarization beam splitters. Therefore, much time is required in constructing the optical color separation and synthesis system, and problems occur in productivity.

SUMMARY OF THE INVENTION

There has been a demand for a optical color separation and synthesis system, and a method of constructing a optical color separation and synthesis system, by which various optical function plates such as a notch filter, wavelength selecting polarization transforming plate, half-wave plate, and ghost buster plate to be disposed facing any of first to fourth polarization beam splitters if necessary can be attached to the polarization beam splitters with good constructing properties, when a method is adopted. In the method, four first to fourth polarization beam splitters are secured to a base beforehand in such a manner that polarization separating surfaces of the respective polarization beam splitters form an X-shape as viewed from an upper-surface side, without integrally bonding the polarization beam splitters to one another beforehand by a light transmitting bonding member (e.g., adhesive). Additionally, optical characteristics of the optical color separation and synthesis system can be satisfactorily maintained, and further dust is also taken into consideration.

In order to achieve the above object, there is provided an optical color separation and synthesis system comprising at least first to fourth polarization beam splitters which chromatically separate white light into a plurality of color beams and which guide the plurality of color beams into a plurality of reflective type spatial light modulation elements corresponding to colors and which chromatically synthesize the respective color beams optically modulated by the respective color reflective type spatial light modulation elements according to a video signal to thereby emit color synthesized light; an optical function plate arranged facing any of the first to fourth polarization beam splitters; a base platform on which the first to fourth polarization beam splitters are arranged in such a manner that polarization separating surfaces of the polarization beam splitters form an X-shape and onto which the polarization beam splitters are bonded while a predetermined gap is formed between facing surfaces of the polarization beam splitters; and a plurality of frames each of which has an opening in a middle portion thereof and a stepped portion for bonding each optical function plate on a peripheral portion thereof and which are secured to any of the first to fourth polarization beam splitters.

According to the present invention, especially, the system comprises the base platform which arranges the first to fourth polarization beam splitters in such a manner that the polarization separating surfaces of the respective polarization beam splitters form the X-shape and which bonds the polarization beam splitters while forming the predetermined gap between the facing surfaces of the polarization beam splitters. The system also comprises a plurality of frames each comprising the opening in the middle portion thereof, and the stepped portion for bonding the optical function plate in the peripheral portion thereof, and each bonded to any of the first to fourth polarization beam splitters. Therefore, various optical function plates can be attached to the polarization beam splitters with good constructing properties, and further optical characteristics of the optical color separation and synthesis system can be satisfactorily maintained.

In a preferable embodiment of the present invention, the stepped portion of the frame inserted between the facing surfaces of the polarization beam splitters has a depth for allowing a part of the polarization beam splitter bonded to the stepped portion and facing the optical function plate to enter the stepped portion.

According to the mode, considerations can be taken in such a manner as to prevent the optical color separation and synthesis system from being invaded by dust.

In the preferable embodiment of the present invention, the frame inserted between the facing surfaces of the polarization beam splitters and having the stepped portion into which the optical function plate is bonded is appropriately combined with the frame having the stepped portion into which the optical function plate is not bonded, and the frames are arranged in such a manner as to cross each other at right angles.

In the preferable embodiment of the present invention, the frame disposed on an incidence side of white light has a bonding flange portion bonded to the first polarization beam splitter and formed in such a manner as to protrude behind a rear surface on an opposite side of a front surface along any side surface of the frame. On the other hand, the frame disposed on an emission side of color synthesized light has a bonding flange portion bonded to the fourth polarization beam splitter and formed in such a manner as to protrude behind the rear surface on the opposite side of the front surface along any side surface of the frame.

According to the mode, the frames can be securely bonded to the first and fourth polarization beam splitters by the adhesive.

In the preferable embodiment of the present invention, in each of the frames disposed on the incidence side of the white light and on the emission side of the color synthesized light, a concave groove for charging the adhesive in the protruded bonding flange portion is formed in an opened state on a rear end, or a through hole for charging the adhesive in the bonding flange portion is formed.

Furthermore, in order to achieve the above object, there is provided a method of constructing an optical color separation and synthesis system comprising at least first to fourth polarization beam splitters which chromatically separate white light into a plurality of color beams and which guide the plurality of color beams into a plurality of reflective type spatial light modulation elements corresponding to colors and which chromatically synthesize the respective color beams optically modulated by the respective color reflective type spatial light modulation elements according to a video signal to thereby emit color synthesized light; and an optical function plate arranged facing any of the first to fourth polarization beam splitters, the method comprising: arranging the first to fourth polarization beam splitters in such a manner that polarization separating surfaces of the polarization beam splitters form an X-shape; forming a predetermined gap between facing surfaces of the polarization beam splitters to bond the polarization beam splitters onto a base platform; and thereafter securing a frame comprising an opening in a middle portion thereof and a stepped portion for bonding the optical function plate on a peripheral portion thereof to any of the first to fourth polarization beam splitters.

According to the present invention, especially, the first to fourth polarization beam splitters are arranged in such a manner that the polarization separating surfaces of the respective polarization beam splitters form the X-shape, and bonded to the base platform while forming the predetermined gap between the facing surfaces of the polarization beam splitters. Thereafter, the frame having the opening in the middle portion, and the stepped portion to be bonded to the optical function plate in the peripheral portion is secured to any of the first to fourth polarization beam splitters. Therefore, various optical function plates can be attached to the polarization beam splitter with good constructing properties, and further optical characteristics of the optical color separation and synthesis system can be satisfactorily maintained.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of an optical color separation and synthesis system, and a method of constructing the optical color separation and synthesis system according to the present invention will be described hereinafter in detail in order of Embodiments 1, 2 with reference toFIGS. 1 to 18.

FIG. 1is a principle diagram of an optical color separation and synthesis system of Embodiment 1 according to the present invention.FIG. 2is an enlarged perspective view showing wavelength selecting polarization transforming plates (polarization transforming plates for R, G, B) shown inFIG. 1.

An optical color separation and synthesis system10of Embodiment 1 according to the present invention shown inFIG. 1is disposed between a light source unit and a projection lens in a reflective type projection display apparatus.

The optical color separation and synthesis system10has a function of separating a white beam emitted from the light source unit into three primary color beams of red (R), green (G), and blue (B), and guiding the three primary color beams to three reflective type spatial light modulation elements30R,30G,30B corresponding to R, G, B, respectively. Furthermore, the system has a function of emitting color synthesized light, to a projection lens side, obtained by chromatically synthesizing the respective color beams optically modulated by the reflective type spatial light modulation elements30R,30G,30B of the respective colors according to a video signal.

In this case, for example, reflective type liquid crystal panels are used in the reflective type spatial light modulation elements30R,30G,30B corresponding to the three primary color beams of R, G, B, and the reflective type spatial light modulation elements30R,30G,30B will be hereinafter referred to as the reflective type liquid crystal panels30R,30G,30B.

More concretely, in the optical color separation and synthesis system10of Embodiment 1 according to the present invention, four first to fourth polarization beam splitters11to14formed into rectangular parallelepiped shapes (also including cubic shapes) using optical glass are arranged in such a manner that polarization separating surfaces11ato14aof the respective polarization beam splitters form an X-shape as viewed from an upper-surface side.

In this case, in the plan view ofFIG. 1, the second polarization beam splitter12is disposed on the left side of the first polarization beam splitter11. Moreover, the third polarization beam splitter13is disposed above the first polarization beam splitter11, and the fourth polarization beam splitter14is disposed above the second polarization beam splitter12and on the left side of the third polarization beam splitter13. Furthermore, a light incidence surface of the first polarization beam splitter11crosses a light emission surface of the fourth polarization beam splitter14at right angles by arrangement relations of various optical function plates21to27and reflective type liquid crystal panels30R,30G,30B described later.

Moreover, the first polarization beam splitter11which white light enters on the light source unit side, and the fourth polarization beam splitter14which emits the color synthesized light on the projection lens side are formed into large sizes. Moreover, the respective polarization separating surfaces11a,14aof the first and fourth polarization beam splitters11,14are diagonally arranged.

Moreover, the second and third polarization beam splitters12,13are formed to be one size smaller than the first and fourth polarization beam splitters11,14. Moreover, the respective polarization separating surfaces12a,13aof the second and third polarization beam splitters12,13are diagonally arranged in such a manner as to cross the polarization separating surfaces11a,14aof the first and fourth polarization beam splitters11,14at right angles.

Furthermore, on the respective polarization separating surfaces11ato14aof the first to fourth polarization beam splitters11to14, a translucent/reflective polarization film which transmits p-polarized light and reflects s-polarized light is formed along a diagonal line of the rectangular parallelepiped shape.

It is to be noted that in the following description, an Rp beam, Gp beam, and Bp beam of three colors indicate the p-polarized light corresponding to R, G, B, respectively, as described later. On the other hand, an Rs beam, Gs beam, and Bs beam of three colors indicate the s-polarized light corresponding to R, G, B, respectively.

Additionally, the reflective type liquid crystal panel30R for R, and the reflective type liquid crystal panel30G for G are disposed facing the left-side surface and the lower surface of the small-sized second polarization beam splitter12in such a manner as to cross each other at right angles. Moreover, the reflective type liquid crystal panel30B is disposed facing the right-side surface of the small-sized third polarization beam splitter13. Accordingly, the reflective type liquid crystal panels30R,30G,30B can be arranged substantially on extension lines of outer frames of the first and fourth polarization beam splitters11,14. Therefore, the optical color separation and synthesis system10can be miniaturized.

It is to be noted that all the first to fourth polarization beam splitters11to14may be formed into equal sizes. In this case, the reflective type liquid crystal panels30R,30G,30B are arranged outside the extension lines of the respective outer frames of the first and fourth polarization beam splitters11,14. Therefore, the optical color separation and synthesis system10is larger than that of Embodiment 1.

Moreover, a notch filter plate21which cuts light having a wavelength in the vicinity of 580 nm, and a wavelength selecting polarization transforming plate (hereinafter referred to as the polarization transforming plate for B)22having a function of rotating the polarization surface of B light by 90° are disposed beside the light incidence surface of the first polarization beam splitter11on the light source unit side. A wavelength selecting polarization transforming plate (hereinafter referred to as the polarization transforming plate for G)23having a function of rotating the polarization surface of G light by 90° is disposed between the first polarization beam splitter11and the second polarization beam splitter12. A wavelength selecting polarization transforming plate (hereinafter referred to as the polarization transforming plate for R)24having a function of rotating the polarization surface of R light by 90° is disposed between the second polarization beam splitter12and the fourth polarization beam splitter14. A half-wave plate25for adjusting the polarization is disposed between the first polarization beam splitter11and the third polarization beam splitter13. A wavelength selecting polarization transforming plate (hereinafter referred to as the polarization transforming plate for B)26having a function of rotating the polarization surface of B light by 90° is disposed between the third polarization beam splitter13and the fourth polarization beam splitter14. A ghost buster plate27for turning the light emitted from the emission surface by λ/4 with respect to a wavelength λ of the light to prevent the light from being returned into the optical color separation and synthesis system10is disposed beside the light emission surface of the fourth polarization beam splitter14on the projection lens side.

In this case, as each of the wavelength selecting polarization transforming plates for the respective colors, including the polarization transforming plate22for B, the polarization transforming plate23for G, the polarization transforming plate24for R, and the polarization transforming plate26for B, as enlarged and shown inFIG. 2, organic films of transparent polycarbonate are laminated (stacked) in about ten layers having different phases. This polycarbonate laminate member having a thickness of about 0.6 to 0.9 mm is formed into a plate shape in accordance with an outer shape of each of the polarization beam splitters11to14.

Among the above-described constituting members, the notch filter plate21, polarization transforming plate22for B, polarization transforming plate23for G, polarization transforming plate24for R, half-wavelength plate25, polarization transforming plate26for B, and ghost buster plate27have inherent optical functions, when transmitting the light. Therefore, these members will be sometimes generically referred to as the optical function plates formed into light transmitting types.

Next, an operation of the optical color separation and synthesis system10constituted as described above will be described with reference toFIG. 1. The white light comprising the p-polarized light including the Rp, Gp, and Bp beams obtained from the light source unit is first applied into the notch filter plate21. After light having a wavelength of around 580 nm is cut by the notch filter plate21, the light enters the polarization transforming plate22for B. Then, the Bp beam of the p-polarized light is polarized/transformed into the Bs beam of the s-polarized light by the polarization transforming plate22for B, and enters the first polarization beam splitter11. Moreover, since the polarization transforming plate22for B does not act on the Rp and Gp beams of the p-polarized light, the Rp and Gp beams passes through the polarization transforming plate22for B, and enters the first polarization beam splitter11.

Moreover, the Rp and Gp beams of the p-polarized light, which have entered the first polarization beam splitter11, pass through the polarization separating surface11a, travel straight as such, and enter the polarization transforming plate23for G. Then, since the polarization transforming plate23for G does not act on the Rp beam of the p-polarized light, the Rp beam passes through the polarization transforming plate23for G, and enters the second polarization beam splitter12. Moreover, the Gp beam of the p-polarized light is polarized/transformed into the Gs beam of the s-polarized light by the polarization transforming plate23for G, and enters the second polarization beam splitter12.

Thereafter, the Rp beam of the p-polarized light which has entered the second polarization beam splitter12passes through the polarization separating surface12a, and enters the reflective type liquid crystal panel30R for R. The beam is optically modulated by the reflective type liquid crystal panel30R for R according to the video signal corresponding to R, and the optically modulated and produced Rs beam which is an s-polarized light component is emitted from the reflective type liquid crystal panel30R. The beam is reflected by the polarization separating surface12a, thereafter turns its direction by 90°, and enters the polarization transforming plate24for R. On the other hand, the Gs beam of the s-polarized light which has entered the second polarization beam splitter12is reflected by the polarization separating surface12a, thereafter turns its direction by 90°, and enters the reflective type liquid crystal panel30G for G. The beam is optically modulated by the reflective type liquid crystal panel30G for G according to the video signal corresponding to G, and the optically modulated and produced Gp beam which is a p-polarized light component is emitted from the reflective type liquid crystal panel30G, passes through the polarization separating surface12a, and enters the polarization transforming plate24for R.

Moreover, the Rs beam of the s-polarized light which has entered the polarization transforming plate24for R is polarized/transformed into the Rp beam of the p-polarized light, and enters the fourth polarization beam splitter14. On the other hand, the Gp beam of the p-polarized light which has entered the polarization transforming plate24for R does not act. Therefore, the Gp beam passes through the polarization transforming plate24for R, and enters the fourth polarization beam splitter14.

Thereafter, the Rp and Gp beams of the p-polarized light, which have entered the fourth polarization beam splitter14, pass through the polarization separating surface14a, travel straight as such, and are emitted on a projection lens side via the ghost buster plate27. In this case, as described above, the ghost buster plate27turns the light emitted from the fourth polarization beam splitter14by λ/4 with respect to the wavelength λ of the light, and prevents the light from being returned into the optical color separation and synthesis system10.

Moreover, the Bs beam of the s-polarized light which has entered the first polarization beam splitter11is reflected by the polarization separating surface11a, thereafter turns its direction by 90°, and enters the half-wave plate25. After the half-wave plate25adjusts the polarization, the beam enters the third polarization beam splitter13. Thereafter, the Bs beam of the s-polarized light which has entered the third polarization beam splitter13is reflected by the polarization separating surface13a, thereafter turns its direction by 90°, and enters the reflective type liquid crystal panel30B for B. The beam is optically modulated by the reflective type liquid crystal panel30B for B according to the video signal corresponding to B, and the optically modulated and produced Bp beam which is a p-polarized light component is emitted from the reflective type liquid crystal panel30B. The beam passes through the polarization separating surface13a, travels straight as such, and enters the polarization transforming plate26for B. Moreover, the Bp beam which has entered the polarization transforming plate26for B and which is the p-polarized light component is polarized/transformed into the Bs beam of the s-polarized light, and the beam enters the fourth polarization beam splitter14. Furthermore, the Bs beam of the s-polarized light which has entered the fourth polarization beam splitter14is reflected by the polarization separating surface14a, turns its direction by 90°, and is emitted on the projection lens side via the ghost buster plate27. Thereafter, the color synthesized light obtained by synthesizing the Rp and Gp beams of the p-polarized light from the light emission surface of the fourth polarization beam splitter14and the Bs beam of the s-polarized light is emitted on the projection lens side via the ghost buster plate27.

Next, a technical idea in the optical color separation and synthesis system10constituted as described above will be described. In the system, the first to fourth polarization beam splitters11to14are bonded onto a base platform15, and various optical function plates, including the notch filter plate21, polarization transforming plate22for B, polarization transforming plate23for G, polarization transforming plate24for R, half-wavelength plate25, polarization transforming plate26for B, ghost buster plate27and the like, are attached to the first to fourth polarization beam splitters11to14in predetermined positions. It is to be noted that the drawing is complicated and therefore omitted in hereinafter describing the reflective type liquid crystal panels30R,30G,30B constituting the optical color separation and synthesis system10.

FIG. 3is a perspective view showing a state in which four first to fourth polarization beam splitters are bonded onto the base platform beforehand.FIGS. 4A and 4Bare side view and bottom plan view showing an operation of bonding the four first to fourth polarization beam splitters onto the base platform.

As shown inFIGS. 3,4A and4B, when the optical color separation and synthesis system10of Embodiment 1 according to the present invention is constructed, four first to fourth polarization beam splitters11to14are bonded onto the base platform15beforehand.

That is, four first to fourth polarization beam splitters11to14are grasped by a known robot, and mounted onto the base platform15in such a manner that the polarization separating surfaces11ato14aof the respective polarization beam splitters (11to14) form an X-shape when viewed from upper surfaces11bto14b. Moreover, a predetermined gap S (FIGS. 4A and 4B) is formed between facing surfaces of the polarization beam splitters (11to14). Additionally, after positioning the first to fourth polarization beam splitters11to14using an optical measurement unit, lower surfaces11cto14cof the splitters are bonded using an ultraviolet setting resin adhesive16.

Concretely, as shown inFIGS. 4A and 4B, as to the base platform15, square transparent glass15bis fitted inside an outer frame15aformed using a black resin material, and integrally secured/bonded. Moreover, the ultraviolet setting resin adhesives16are applied to the vicinities of corner portions in which the polarization separating surfaces11ato14across one another in the X-shape in the respective lower surfaces11cto14cof the four first to fourth polarization beam splitters11to14. Then, the first to fourth polarization beam splitters11to14are positioned in predetermined positions on the base platform15, and thereafter ultraviolet rays are applied from below the transparent glass15bto thereby bond the lower surfaces.

In this case, the predetermined gaps S are formed to be substantially equal between the first and second polarization beam splitters11,12, between the second and fourth polarization beam splitters12,14, between the fourth and third polarization beam splitters14,13, and between the third and first polarization beam splitters13,11on the base platform15. As described later, the second frames42L,42R (FIG. 7) to which the optical function plates are bonded can be inserted in each predetermined gap S from the facing side surfaces of the polarization beam splitters (11to14). Additionally, countermeasures are applied to the respective lower surfaces of the second frames42L,42R in a case where the ultraviolet setting resin adhesive16sticks out in the predetermined gap S on the base platform15. The countermeasures will be described later.

Here, the first frames41L,41R for use in attaching various optical function plates to the light incidence surface of the first polarization beam splitter11and the light emission surface of the fourth polarization beam splitter14will be described with reference toFIGS. 5A and 5B,6A to6F.

FIGS. 5A and 5Bare enlarged perspective views showing the first frames41L,41R.FIGS. 6A to 6Fare top plan view, front view, left-side view, rear view, X—X sectional view, and part-A enlarged view showing the first frame41L.

As shown inFIGS. 5A and 5B, the first frames41L,41R are formed into substantially rectangular frame shapes using a black resin material having a thermal expansion coefficient substantially equal to that of the optical function plate, and are formed into one size larger vertical/horizontal dimensions as compared with those of the large-sized first and fourth polarization beam splitters11,14. The first frames41L,41R are different from each other only in that the bonding flange portions formed on the right/left side surfaces are symmetrically formed, and other portions are formed into the same shapes.

That is, as shown inFIGS. 5A,6A to6F, in the first frame41L attached to the light incidence surface of the first polarization beam splitter11, a first stepped portion41a1is opened into a rectangular frame shape in accordance with an optical function plate having a predetermined outer dimension in an inner peripheral portion on the side of a front surface41a. Moreover, a second stepped portion41a2having one size larger outer dimension is opened into a rectangular frame shape in accordance with one size larger optical function plate as compared with the predetermined outer dimension in a front peripheral portion of the first stepped portion41a1. Furthermore, four paste margin portions41a3for the adhesives are formed in upper/lower/right/left corner portions of the first stepped portion41a1.

Moreover, after two optical function plates21,22(FIG. 1) having different sizes are fitted into the first and second stepped portions41a1,41a2from the front surface41aof the first frame41L, the adhesives (not shown) are charged in four paste margin portions41a3to thereby bond two optical function plates21,22(FIG. 1). Needless to say, when only one optical function plate is attached to the front surface41aof the first frame41L, the plate may be fitted into only one of the first and second stepped portions41a1,41a2.

Furthermore, in a middle portion of a rear surface41bof the first frame41L, an opening41b1having an aperture function for passing the light is opened into a rectangular shape having one size smaller than the first stepped portion41a1formed in the inner peripheral portion of the front surface41a, and thicknesses of the first stepped portion41a1and the rear surface41bare set to be small.

Additionally, on an upper surface41cof the first frame41L, a bonding flange portion41c1is horizontally formed along the upper surface41cprotruding behind the rear surface41bon the opposite side of the front surface41a. Moreover, in the side surfaces of the bonding flange portion41c1behind the rear surface41b, concave grooves41c1-1,41c1-2for charging the adhesives (not shown) on the side of the first polarization beam splitter11are formed while rear ends of the grooves are opened.

Moreover, in the same manner as described above, on a lower surface41dof the first frame41L, a bonding flange portion41d1is horizontally formed along the lower surface41dprotruding behind the rear surface41b. Moreover, in the side surfaces of the bonding flange portion41d1behind the rear surface41b, concave grooves41d1-1,41d1-2for charging the adhesives (not shown) on the side of the first polarization beam splitter11are formed while rear ends of the grooves are opened.

Furthermore, in the same manner as described above, on a left-side surface41eof the first frame41L, a bonding flange portion41e1is vertically formed along the left surface41eprotruding behind the rear surface41b. Moreover, in vertical side surfaces of the bonding flange portion41e1behind the rear surface41b, concave grooves41e1-1,41e1-2for charging the adhesives (not shown) on the side of the first polarization beam splitter11are formed while rear ends of the grooves are opened.

It is to be noted that any bonding flange portion is not formed on a right-side surface41fof the first frame41L.

Moreover, the adhesives (not shown) are charged into the respective concave grooves41c1-1,41c1-2,41d1-1,41d1-2,41e1-1,41e1-2of the bonding flange portions41c1,41d1,41e1formed in the upper surface41c, lower surface41d, and left-side surface41eof the first frame41L, and accordingly the first frame41L is bonded to the first polarization beam splitter11on the light source side.

On the other hand, as shown inFIG. 5B, on the right-side surface41fof the first frame41R attached to the light emission surface of the fourth polarization beam splitter14, a bonding flange portion41f1is vertically formed along the right-side surface41fprotruding behind the rear surface41b. Moreover, in vertical side surfaces of the bonding flange portion41f1behind the rear surface41b, concave grooves41f1-1,41f1-2for charging the adhesives (not shown) on the side of the fourth beam splitter14are formed while rear ends of the grooves are opened. This respect is different from the first frame41L. Although not described in detail, the first frame41R is bonded to the fourth polarization beam splitter14on the projection lens side. It is to be noted that when the first frame41L is vertically reversed, the shape of the first frame41R is obtained. Therefore, the first frame41R does not have to be separately prepared. The first frame41L or the first frame41R only may be used in common with respect to the first and fourth polarization beam splitters11,14.

Next, the second frames42L,42R for use in attaching various optical function plates to the predetermined gaps S (FIGS. 4A and 4B) formed between the facing surfaces of the polarization beam splitters (11to14) will be described with reference toFIGS. 7A and 7B,8A to8H.

FIGS. 7A and 7Bare enlarged perspective views showing the second frames42L,42R.FIGS. 8A to 8Hare top plan view, front view, left-side view, rear view, Y—Y sectional view, X—X sectional view, part-A enlarged view, and bottom plan view showing the second frame42L.

As shown inFIGS. 7A and 7B, the second frames42L,42R are also formed into substantially rectangular frame shapes using a black resin material having a thermal expansion coefficient substantially equal to that of the optical function plate, and are formed into one size larger vertical/horizontal dimensions as compared with those of the small-sized second and third polarization beam splitters12,13. The second frames42L,42R are different from each other only in that only tapered surfaces are symmetrically formed for allowing the frames42L,42R to cross each other at right angles, when the frames are inserted into the predetermined gaps S (FIGS. 4A and 4B) formed between the facing surfaces of the polarization beam splitters (11to14) as described above with respect toFIGS. 4A and 4B, and other portions are formed into the same shapes.

Moreover, as described later, the second frame42L is inserted between the first and second polarization beam splitters11,12, and between the third and fourth polarization beam splitters13,14. On the other hand, the second frame42R is inserted between the second and fourth polarization beam splitters12,14, and between the first and third polarization beam splitters11,13.

That is, as shown inFIGS. 7A,8A to8H, in the second frame42L, a stepped portion42a1is opened into a rectangular frame shape in accordance with an optical function plate having a predetermined outer dimension in a peripheral portion of a front surface42a. Moreover, four paste margin portions42a2for the adhesives are formed in upper/lower/right/left corner portions of the stepped portion42a1. Furthermore, after one optical function plate is fitted into the stepped portion42a1from the front surface42aof the second frame42L, the adhesives (not shown) are charged in four paste margin portions42a2to thereby bond one optical function plate.

In this case, a depth of the stepped portion42a1of the second frame42L is set to be larger than the thickness of the optical function plate to be bonded to the stepped portion, and accordingly a part of the polarization beam splitter (11to14) facing the optical function plate can be inserted. Therefore, considerations can be taken in such a manner as to prevent the optical color separation and synthesis system10from being invaded by dust. Moreover, a slight space is set to be obtained between the surface of the inserted polarization beam splitter (11to14) and the optical function plate, and this can prevent temperature rise between the optical function plate and the polarization beam splitter (11to14). It is to be noted that the temperature rise occurs in the optical color separation and synthesis system10by the white light emitted from the light source unit.

Furthermore, in a middle portion of a rear surface42bof the second frame42L, an opening42b1having an aperture function for passing the light is opened into a rectangular shape having one size smaller than the stepped portion42a1formed in the peripheral portion of the front surface42a, and thickness between the stepped portion42a1and the rear surface421bare set to be small.

Additionally, on an upper surface42cof the second frame42L, a bonding flange portion42c1is horizontally formed protruding behind the rear surface42bon the opposite side of the front surface42a. Moreover, in upper bonding flange portion42c1, a concave grooves42c1-1for charging the adhesive (not shown) is formed while a rear end of the groove is opened. The adhesive (not shown) is charged into the concave groove42c1-1, and accordingly the second frame42L is bonded to the upper surface of the first polarization beam splitter11or the fourth polarization beam splitter14.

Furthermore, a lower surface42dof the second frame42L is cut out to be shallow upwards on the side of a left-side surface42eto thereby form a cutout portion42d1. This cutout portion42d1functions as a relief for avoiding a sticking-out portion of the ultraviolet setting resin adhesive16in a case where the ultraviolet setting resin adhesive16sticks out into the predetermined gap S formed between the facing surfaces of the polarization beam splitters (11to14) on the base platform15, when the first to fourth polarization beam splitters11to14are bonded onto the base platform15using the ultraviolet setting resin adhesive16as described above with reference toFIGS. 4A and 4B.

Moreover, on the left-side surface42eof the second frame42L, a tapered surface42e1is formed inside the front surface42a, and into an opened state with respect to the front surface42a. This tapered surface42e1is formed in such a manner that the second frame42L can cross the second frame42R at right angles, when the tapered surface abuts on a tapered surface42f2formed on a right-side surface42fof the second frame42R shown inFIG. 7Bas described later.

Furthermore, a stopper surface42f1is formed on the right-side surface42fof the second frame42L. This stopper surface42f1abuts on the side surface of the positioned optical function plate. Moreover, as described later, when the second frame42L is inserted into the predetermined gap S from the tapered surface42e1on the base platform15described above with reference toFIGS. 4A and 4B, the side surface of the second polarization beam splitter12or the third polarization beam splitter13is positioned to thereby abut on the stopper surface42f1.

Additionally, as enlarged and shown inFIG. 8G, a stepped portion42b2slightly indented inside the rear surface42bis formed in the rear surface42bin the vicinity of the tapered surface42e1formed on the left-side surface42eof the second frame42L. This stepped portion42b2functions as a relief for preventing the side surface of the first polarization beam splitter11or the fourth polarization beam splitter14from being damaged, when the second frame42L is inserted along the first or fourth polarization beam splitter11,14.

On the other hand, as shown inFIG. 7B, since the second frame42R is different from the second frame42L only in that the tapered surface42f2is formed on the right-side surface42fas described above, detailed description thereof is omitted. The second frame42R is also bonded to the upper surface of the first polarization beam splitter11or the fourth polarization beam splitter14.

It is to be noted that to bond two optical function plates to the second frames42L,42R, the first and second stepped portions having different sizes may be formed into frame shapes on the front surface42ain the same manner as in the first frames41L,41R.

Furthermore, in Embodiment 1, the respective bonding flange portions42c1formed on the upper surfaces42cof the second frames42L,42R are formed in such a manner as to be bonded to the upper surface of the first polarization beam splitter11or the fourth polarization beam splitter14, but the present invention is not limited to this embodiment. The second frames42L,42R may be attached to any of the first to fourth polarization beam splitters11to14.

Here, the constructing of the optical color separation and synthesis system10of Embodiment 1 according to the present invention will be described with reference toFIGS. 9 to 13.

FIG. 9is a partially sectional plan view showing that the optical color separation and synthesis system of Embodiment 1 according to the present invention is constructed.FIGS. 10A and 10Bare sectional view and perspective view showing that the first and second frames are attached to the first polarization beam splitter.FIG. 11is an enlarged plan view showing that tapered surfaces of four second frames intersect with one another in an X-shape.FIG. 12is a perspective view showing that the optical color separation and synthesis system of Embodiment 1 according to the present invention is constructed.FIG. 13is a plan view showing that a transparent seal is attached to the upper surfaces of four second frames whose tapered surfaces intersect with one another in the X-shape in the optical color separation and synthesis system of Embodiment 1 according to the present invention.

First, as shown inFIG. 9, the four first to fourth polarization beam splitters11to14are arranged in such a manner that the polarization separating surfaces11ato14aof the respective polarization beam splitters (11to14) form an X-shape as viewed from the upper surfaces of the splitters. Moreover, the predetermined gap S is formed between the facing surfaces of the polarization beam splitters (11to14), while the splitters are bonded onto the base platform15. Thereafter, the second frames42L,42R to which the optical function plate has been secured are inserted in the predetermined gap S, and the second frames42L,42R are bonded to the upper surface of either the first polarization beam splitter11or the fourth polarization beam splitter14.

This will be concretely described. The second frame42L to which the polarization transforming plate23for G has been bonded is inserted from the tapered surface42e1between the first and second polarization beam splitters11,12toward an arrow Y1direction from the respective side surfaces of the first and second polarization beam splitters11,12, and the second frame42L is bonded to the upper surface of the first polarization beam splitter11.

Moreover, the second frame42R to which the polarization transforming plate24for R has been bonded is inserted from the tapered surface42f2between the second and fourth polarization beam splitters12,14toward an arrow X1direction from the side surfaces of the second and fourth polarization beam splitters12,14, and the second frame42R is bonded to the upper surface of the fourth polarization beam splitter14.

Furthermore, the second frame42R to which the half-wavelength plate25has been bonded is inserted from the tapered surface42f2between the first and third polarization beam splitters11,13toward an arrow X2direction from the side surfaces of the first and third polarization beam splitters11,13, and the second frame42R is bonded to the upper surface of the first polarization beam splitter11.

Additionally, the second frame42L to which the polarization transforming plate26for B has been bonded is inserted from the tapered surface42e1between the third and fourth polarization beam splitters13,14toward an arrow Y2direction from the side surfaces of the third and fourth polarization beam splitters13,14, and the second frame42L is bonded to the upper surface of the fourth polarization beam splitter14.

With the insertion of the second frames42L,42R, the bonding flange portions42c1formed on the upper surfaces42cof the second frames42L,42R are inserted in such a manner as to abut on the upper surface of the large-sized first polarization beam splitter11or fourth polarization beam splitter14. Moreover, the rear surfaces42bof the second frames42L,42R are brought into close contact with the side surface of the first polarization beam splitter11or the fourth polarization beam splitter14, and inserted. In this case, when the rear surfaces42bof the second frames42L,42R are brought into close contact with the side surfaces of the first and fourth polarization beam splitters11,14, and inserted, the side surfaces of the first and fourth polarization beam splitters11,14are not damaged. Because, on each rear surface42b, the stepped portion42b2slightly indented behind the rear surface42bis formed in a leading portion of an insertion direction as shown inFIGS. 8D and 8G.

In this case, for example, the second frame42L to which the polarization transforming plate23for G has been bonded is inserted between the first and second polarization beam splitters11,12as shown inFIGS. 10A and 10B. In this case, the leading tapered surface42e1in the arrow Y1direction is opened with respect to the front surface42a. Therefore, a part of the small-sized second polarization beam splitter12disposed facing the stepped portion42a1of the second frame42L can overlap by a dimension T and enter the stepped portion42a1formed in the front surface42a. Consequently, invasion of dust between the first and second polarization beam splitters11,12is prevented, and the side surface of the second polarization beam splitter12abuts on the stopper surface42f1formed on the right-side surface42fof the second frame42L, and is positioned with respect to the insertion direction. Thereafter, the adhesive (not shown) is charged in the concave groove42c1-1of the bonding flange portion42c1protruded behind the rear surface42bfrom the upper surface42cof the second frame42L to thereby bond the frame to the upper surface of the large-sized first polarization beam splitter11.

Needless to say, also with regard to the second frames42L,42R, a part of the small-sized second polarization beam splitter12overlaps and enters the stepped portion42a1formed on the front surface42aby the dimension T, and the second frames42L,42R are bonded to the upper surface of either the large-sized first polarization beam splitter11and fourth polarization beam splitter14.

Moreover, when the second frames42L,42R are inserted between the facing surfaces of the polarization beam splitters (11to14), as enlarged and shown inFIG. 11, the tapered surfaces42e1,42f2are arranged along the extension lines of the polarization separating surfaces12a,13aof the second and third polarization beam splitters12,13, and further four second frames42L,42R in total are arranged in such a manner as to cross one another at right angles.

Turning back toFIG. 9, after inserting the second frames42L,42R between the facing surfaces of the polarization beam splitters (11to14), the first frame41L to which the notch filter plate21and polarization transforming plate22for B have been bonded is attached to the light incidence surface of the first polarization beam splitter11. Moreover, the first frame41R to which the ghost buster plate27has been bonded is attached to the light emission surface of the fourth polarization beam splitter14.

In this case, as described above with reference toFIGS. 5A and 5B, the adhesives (not shown) are charged in the respective concave grooves41c1-1,41c1-2,41d1-1,41d1-2,41e1-1,41e1-2(41f1-1,41f1-2) of the bonding flange portions41c1,41d1,41e1(41f1) protruded behind the rear surface41bon the upper surface41c, lower surface41d, left-side surface41e(right-side surface41f) of the first frame41L to thereby bond the first frame41L (41R) to the surface of the first (fourth) polarization beam splitter11(14).

Moreover, the first frames41L,41R and the second frames42L,42R are bonded to the first and fourth polarization beam splitters11,14, and constructed as shown inFIG. 12.

Furthermore, as shown inFIG. 13, after constructing the optical color separation and synthesis system10, a transparent seal43is attached to the upper surfaces of the tapered surfaces42e1,42f2while the four second frames42L,42R in total intersect with one another. Consequently, the optical color separation and synthesis system10is prevented from being invaded by the dust from above.

As described above, in the optical color separation and synthesis system10of Embodiment 1 according to the present invention, the four first to fourth polarization beam splitters11to14are arranged in such a manner that the polarization separating surfaces11ato14aof the polarization beam splitters form the X-shape when viewed from the upper surfaces. Moreover, the predetermined gap S is formed between the facing surfaces of the polarization beam splitters (11to14), and the lower surfaces11cto14care bonded onto the base platform15. Thereafter, the first frames41L,41R and the second frames42L,42R to which various optical function plates have been bonded are bonded to the large-sized first and fourth polarization beam splitters11,14. Therefore, various optical function plates can be attached to the first and fourth polarization beam splitters11,14with good constructing properties, further optical characteristics of the optical color separation and synthesis system10can be satisfactorily maintained, and considerations are taken in such a manner as to prevent the optical color separation and synthesis system10from being invaded by the dust.

Here, Modifications 1 to 3 in which the above-described first frames41L,41R of the optical color separation and synthesis system10of Embodiment 1 are partially modulated will be described with reference toFIGS. 14A to 16C.

It is to be noted that inFIGS. 14A to 16C, only first frames41L-(1) to41L-(3) of Modifications 1 to 3 to be attached to the light incidence surface of the first polarization beam splitter11are shown. On the other hand, first frames41R-(1) to41R-(3) of Modifications 1 to 3 to be attached to the light emission surface of the fourth polarization beam splitter14may be formed symmetrically with respect to the first frames41L-(1) to41L-(3) of Modifications 1 to 3, and therefore description and drawing thereof are omitted.

FIGS. 14A to 14Care explanatory views of a partially modified frame of Modification 1 in the optical color separation and synthesis system of Embodiment 1 according to the present invention,FIG. 14Ais a perspective view,FIG. 14Bis an X—X arrow sectional view, andFIG. 14Cis a Y—Y arrow sectional view.FIGS. 15A to 15Care explanatory views of the partially modified frame of Modification 2 in the optical color separation and synthesis system of Embodiment 1 according to the present invention,FIG. 15Ais a perspective view,FIG. 15Bis an X—X arrow sectional view, andFIG. 15Cis a Y—Y arrow sectional view.FIGS. 16A to 16Care explanatory views of the partially modified frame of Modification 3 in the optical color separation and synthesis system of Embodiment 1 according to the present invention,FIG. 16Ais a perspective view,FIG. 16Bis an X—X arrow sectional view, andFIG. 16Cis a Y—Y arrow sectional view.

First, as shown inFIGS. 14A to 14C, the first frame41L-(1) of Modification 1 is formed into a substantially rectangular frame shape using a black resin material having a thermal expansion coefficient equal to that of the optical function plate in the same manner as in the first frame41L described above with reference toFIGS. 5A and 6Ato6F. Only respects different from those of the first frame41L will be described.

On the upper surface41cof the first frame41L-(1) of Modification 1, bonding flange portions41c2,41c3are horizontally separately formed protruding behind the rear surface41bon the opposite side of the front surface41a. Moreover, through holes41c2-1,41c3-1for charging the adhesives (not shown) on the side of the first polarization beam splitter11are formed into rectangular shapes, extending through the bonding flange portions41c2,41c3behind the rear surface41b. In this case, in a mold, the through holes41c2-1,41c3-1are indented into concave portions behind the bonding flange portions41c2,41c3from the front surface41a, and are accordingly formed into rectangular shapes extending through the bonding flange portions41c2,41c3behind the rear surface41bvia the frame of the opening41b1formed into the rectangular shape in the rear surface41b.

Moreover, in the same manner as described above, on the lower surface41dof the first frame41L-(1), bonding flange portions41d2,41d3are horizontally separately formed protruding behind the rear surface41b. Furthermore, through holes41d2-1,41d3-1for charging the adhesives (not shown) on the side of the first polarization beam splitter11are formed into rectangular shapes, extending through the bonding flange portions41d2,41d3behind the rear surface41b.

Furthermore, in the same manner as described above, on the left-side surface41eof the first frame41L-(1), bonding flange portions41e2,41e3are vertically separately formed protruding behind the rear surface41b. Furthermore, through holes41e2-1,41e3-1for charging the adhesives (not shown) on the side of the first polarization beam splitter11are formed into rectangular shapes, extending through the bonding flange portions41e2,41e3behind the rear surface41b.

Additionally, the adhesives (not shown) are charged in the through holes41c2-1,41c3-1,41d2-1,41d3-1,41e2-1,41e3-1of the bonding flange portions41c2,41c3,41d2,41d3,41e2,41e3formed on the upper surface41c, lower surface41d, left-side surface41eof the first frame41L-(1), and accordingly the first frame41L-(1) is bonded to the first polarization beam splitter11on the light source side.

After bonding the first frame41L to the first polarization beam splitter11on the light source side, assuming that the first frame41L is intentionally peeled forwards. When a force is exerted in this manner, there is danger that the first frame41L is peeled while the only adhesive (not shown) remains on the side of the first polarization beam splitter11. This is because the rear end of each concave groove formed in each bonding flange portion for charging the adhesive is opened. On the other hand, in the first frame41L-(1) of the modification, each through hole formed in each bonding flange portion for charging the adhesive extends on the side of the first polarization beam splitter11. Therefore, there is not any danger that the only adhesive (not shown) remains on the side of the first polarization beam splitter11, and adhesive strength of the first frame41L-(1) to the first polarization beam splitter11can be enhanced.

Next, as shown inFIGS. 15A to 15C, the first frame41L-(2) of Modification 2 is formed into a substantially rectangular frame shape using a black resin material having a thermal expansion coefficient equal to that of the optical function plate in the same manner as in the above-described first frame41L and the first frame41L-(1) of Modification 1. Only respects different from those of the first frame41L and the first frame41L-(1) of Modification 1 will be described.

On the upper surface41cof the first frame41L-(2) of Modification 2, bonding flange portions41c4,41c5are horizontally separately formed protruding behind the rear surface41bon the opposite side of the front surface41a. Moreover, tapered through holes41c4-1,41c5-1for charging the adhesives (not shown) on the side of the first polarization beam splitter11are formed extending through the bonding flange portions41c4,41c5behind the rear surface41b. In this case, in a mold, the tapered through holes41c4-1,41c5-1are indented into concave portions behind the bonding flange portions41c4,41c5from the front surface41a, and are accordingly formed extending through the bonding flange portions41c4,41c5behind the rear surface41bvia the frame of the opening41b1formed into the rectangular shape in the rear surface41b.

Moreover, in the same manner as described above, on the lower surface41dof the first frame41L-(2), bonding flange portions41d4,41d5are horizontally separately formed protruding behind the rear surface41b. Furthermore, tapered through holes41d4-1,41d5-1for charging the adhesives (not shown) on the side of the first polarization beam splitter11are formed extending through the bonding flange portions41d4,41d5behind the rear surface41b.

Furthermore, in the same manner as described above, on the left-side surface41eof the first frame41L-(2), bonding flange portions41e4,41e5are vertically separately formed protruding behind the rear surface41b. Furthermore, tapered through holes41e4-1,41e5-1for charging the adhesives (not shown) on the side of the first polarization beam splitter11are formed extending through the bonding flange portions41e4,41e5behind the rear surface41b.

Additionally, the adhesives (not shown) are charged in the through holes41c4-1,41c5-1,41d4-1,41d5-1,41e4-1,41e5-1of the bonding flange portions41c4,41c5,41d4,41d5,41e4,41e5formed on the upper surface41c, lower surface41d, left-side surface41eof the first frame41L-(2), and accordingly the first frame41L-(2) is bonded to the first polarization beam splitter11on the light source side.

Also in the first frame41L-(2) of Modification 2, each tapered through hole formed in each bonding flange portion for charging the adhesive extends on the side of the first polarization beam splitter11. Therefore, in the same manner as in the first frame41L-(1) of Modification 1, there is not any danger that the only adhesive (not shown) remains on the side of the first polarization beam splitter11, and adhesive strength of the first frame41L-(2) to the first polarization beam splitter11can be enhanced.

Next, as shown inFIGS. 16A to 16C, the first frame41L-(3) of Modification 3 is formed into a substantially rectangular frame shape using a black resin material having a thermal expansion coefficient equal to that of the optical function plate in the same manner as in the above-described first frame41L, the first frame41L-(1) of Modification 1, and the first frame41L-(2) of Modification 2. Only respects different from those of the first frame41L, the first frame41L-(1) of Modification 1, and the first frame41L-(2) of Modification 2 will be described.

On the upper surface41cof the first frame41L-(3) of Modification 3, bonding flange portions41c6,41c7are horizontally separately formed protruding behind the rear surface41bon the opposite side of the front surface41a. Moreover, stepped through holes41c6-1,41c7-1for charging the adhesives (not shown) on the side of the first polarization beam splitter11are formed extending through the bonding flange portions41c6,41c7behind the rear surface41b. In this case, in a mold, the stepped through holes41c6-1,41c7-1are indented into concave portions with horizontal/vertical stepped portions behind the bonding flange portions41c6,41c7from the front surface41a, and are accordingly formed extending through the bonding flange portions41c6,41c7behind the rear surface41bvia the frame of the opening41b1formed into the rectangular shape in the rear surface41b.

Moreover, in the same manner as described above, on the lower surface41dof the first frame41L-(3), bonding flange portions41d6,41d7are horizontally separately formed protruding behind the rear surface41b. Furthermore, stepped through holes41d6-1,41d7-1for charging the adhesives (not shown) on the side of the first polarization beam splitter11are formed extending through the bonding flange portions41d6,41d7behind the rear surface41b.

Furthermore, in the same manner as described above, on the left-side surface41eof the first frame41L-(3), bonding flange portions41e6,41e7are vertically separately formed protruding behind the rear surface41b. Furthermore, stepped through holes41e6-1,41e7-1for charging the adhesives (not shown) on the side of the first polarization beam splitter11are formed extending through the bonding flange portions41e6,41e7behind the rear surface41b.

Additionally, the adhesives (not shown) are charged in the stepped through holes41c6-1,41c7-1,41d6-1,41d7-1,41e6-1,41e7-1of the bonding flange portions41c6,41c7,41d6,41d7,41e6,41e7formed on the upper surface41c, lower surface41d, left-side surface41eof the first frame41L-(3), and accordingly the first frame41L-(3) is bonded to the first polarization beam splitter11on the light source side.

Also in the first frame41L-(3) of Modification 3, each stepped through hole formed in each bonding flange portion for charging the adhesive extends on the side of the first polarization beam splitter11. Therefore, in the same manner as in the first frames41L-(1),41L-(2) of Modifications 1, 2, there is not any danger that the only adhesive (not shown) remains on the side of the first polarization beam splitter11, and adhesive strength of the first frame41L-(3) to the first polarization beam splitter11can be enhanced.

FIG. 17is a principle diagram of an optical color separation and synthesis system of Embodiment 2 according to the present invention.FIG. 18is a partially sectional plan view showing that the optical color separation and synthesis system of Embodiment 2 according to the present invention is constructed.

An optical color separation and synthesis system10′ of Embodiment 2 shown inFIGS. 17 and 18is different from the above-described optical color separation and synthesis system10of Embodiment 1 in arrangements of various optical function plates and reflective type spatial light modulation elements (reflective type liquid crystal panels)30R,30G,30B. For the sake of convenience of the description, the above-described constituting members are denoted with the same reference numerals, and constituting members different from those of Embodiment 1 will be denoted with new reference numerals and described.

As shown inFIG. 17, in the same manner as in Embodiment 1, in the optical color separation and synthesis system10′ of Embodiment 2 according to the present invention, four first to fourth polarization beam splitters11to14are arranged in such a manner that polarization separating surfaces11ato14aof the respective polarization beam splitters form an X-shape in a plane manner as viewed from upper surfaces.

In this case, in the plan view ofFIG. 17, the second polarization beam splitter12is disposed on the left side of the first polarization beam splitter11. Moreover, the third polarization beam splitter13is disposed above the first polarization beam splitter11, and the fourth polarization beam splitter14is disposed above the second polarization beam splitter12and on the left side of the third polarization beam splitter13. Furthermore, unlike Embodiment 1, a light incidence surface of the first polarization beam splitter11extends in parallel with a light emission surface of the fourth polarization beam splitter14by arrangement relations of various optical function plates51to54and reflective type liquid crystal panels30R,30G,30B.

Moreover, in the same manner as in Embodiment 1, the first polarization beam splitter11which white light enters on the light source unit side, and the fourth polarization beam splitter14which emits color synthesized light on the projection lens side are formed into large sizes. Moreover, the respective polarization separating surfaces11a,14aof the first and fourth polarization beam splitters11,14are diagonally arranged. The second and third polarization beam splitters12,13are formed to be one size smaller than the first and fourth polarization beam splitters11,14. Moreover, the respective polarization separating surfaces12a,13aof the second and third polarization beam splitters12,13are diagonally arranged in such a manner as to cross the polarization separating surfaces11a,14aof the first and fourth polarization beam splitters11,14at right angles.

Furthermore, on the respective polarization separating surfaces11ato14aof the first to fourth polarization beam splitters11to14, in the same manner as in Embodiment 1, a translucent/reflective polarization film which transmits p-polarized light and reflects s-polarized light is formed along a diagonal line of a rectangular parallelepiped shape.

Here, respects different from those of Embodiment 1 will be described. A reflective type liquid crystal panel30G for G is disposed facing the left-side surface of the small-sized second polarization beam splitter12. Moreover, a reflective type liquid crystal panel30R for R and a reflective type liquid crystal panel30B for B are arranged facing upper surface and right-side surface of the small-sized third polarization beam splitter13in such a manner as to cross each other at right angles. The reflective type liquid crystal panels30R,30G,30B are miniaturized in accordance with sizes of the second and third polarization beam splitters12,13.

Moreover, a wavelength selecting polarization transforming plate (hereinafter referred to as the polarization transforming plate for G)51having a function of rotating a polarization plane of G light by 90° is disposed beside the light incidence surface of the first polarization beam splitter11on the light source unit side. A wavelength selecting polarization transforming plate (hereinafter referred to as the polarization transforming plate for R)52having a function of rotating the polarization plane of R light by 90° is disposed between the first polarization beam splitter11and the third polarization beam splitter13. A wavelength selecting polarization transforming plate (hereinafter referred to as the polarization transforming plate for R)53having a function of rotating the polarization plane of R light by 90° is disposed between the third polarization beam splitter13and the fourth polarization beam splitter14. A wavelength selecting polarization transforming plate (hereinafter referred to as the polarization transforming plate for G)54having a function of rotating the polarization plane of G light by 90° is disposed beside the light emission surface of the fourth polarization beam splitter14on the light source side.

Among the respective constituting members, the polarization transforming plate51for G, the polarization transforming plate52for R, the polarization transforming plate53for R, and the polarization transforming plate54for G have inherent optical functions in transmitting the light, and therefore they will be sometimes generically referred to as the light transmitting type optical function plates.

In this case, in Embodiment 2, any optical function plate is not disposed between the first and second polarization beam splitters11,12, or between second and forth polarization beam splitters12,14. Therefore, the optical function plate may be disposed between the facing surfaces of the polarization beam splitters (11to14) if necessary.

Moreover, when the white light comprising Rs, Gs, and Bs beams of s-polarized light obtained from a light source unit enters the first polarization beam splitter11from the light incidence surface, the color synthesized light obtained by synthesizing Rp, Gp, and Bp beams of p-polarized light is emitted on the projection lens side from the light emission surface of the fourth polarization beam splitter14through shown light paths.

Next, to construct the optical color separation and synthesis system10′ of Embodiment 2, as shown inFIG. 18, the four first to fourth polarization beam splitters11to14are arranged in such a manner that the polarization separating surfaces11ato14aof the polarization beam splitters form the X-shape when viewed from the upper surfaces. A predetermined gap S is formed between the facing surfaces of the polarization beam splitters (11to14), and the splitters are bonded onto a base platform15. Thereafter, second frames42L,42R are inserted in the predetermined gap S, and bonded to the upper surface of either the first polarization beam splitter11or the fourth polarization beam splitter14.

This will be concretely described. The vacant second frame42L to which any optical function plate has not been bonded is inserted between the first and second polarization beam splitters11,12from an arrow Y1direction, and the second frame42L which does not have any optical function plate is bonded to the upper surface of the first polarization beam splitter11.

Moreover, the vacant second frame42R to which any optical function plate has not been bonded is inserted between the second and fourth polarization beam splitters12,14from an arrow X1direction, and the second frame42R which does not have any optical function plate is bonded to the upper surface of the fourth polarization beam splitter14.

Furthermore, the second frame42R to which the polarization transforming plate52for R has been bonded is inserted between the first and third polarization beam splitters11,13from an arrow X2direction, and the second frame42R including the optical function plate is bonded to the upper surface of the first polarization beam splitter11.

Additionally, the second frame42L to which the polarization transforming plate53for R has been bonded is inserted between the third and fourth polarization beam splitters13,14from an arrow Y2direction, and the second frame42L including the optical function plate is bonded to the upper surface of the fourth polarization beam splitter14.

The second frames42L,42R to which the optical function plates have been bonded are appropriately combined with the vacant second frames42L,42R to which any optical function plate has not been bonded, and the frames are arranged between the facing surfaces of the polarization beam splitters (11to14) in such a manner as to cross one another at right angles.

Moreover, after inserting the second frames42L,42R between the facing surfaces of the polarization beam splitters (11to14), the first frame41L to which the polarization transforming plate51for G has been bonded is attached to the light incidence surface of the first polarization beam splitter11. Furthermore, the first frame41L to which the polarization transforming plate54for G has been bonded is attached to the light emission surface of the fourth polarization beam splitter14.

Therefore, in the above-described optical color separation and synthesis system10′ of Embodiment 2 according to the present invention, in substantially the same manner as in Embodiment 1, the four first to fourth polarization beam splitters11to14are arranged in such a manner that the polarization separating surfaces11ato14aof the polarization beam splitters form the X-shape when viewed from the upper surfaces. Moreover, the predetermined gap S is formed between the facing surfaces of the polarization beam splitters (11to14), and the lower surfaces11cto14care bonded onto the base platform15. Thereafter, the first frames41L,41R to which various optical function plates have been bonded, and the second frames42L,42R including no optical function plate, and including the optical function plates are bonded to the large-sized first and fourth polarization beam splitters11,14. Therefore, various optical function plates can be attached to the first and fourth polarization beam splitters11,14with good constructing properties, further optical characteristics of the optical color separation and synthesis system10′ can be satisfactorily maintained, and considerations are taken in such a manner as to prevent the optical color separation and synthesis system10′ from being invaded by the dust.

It should be understood that many modifications and adaptations of the invention will become apparent to those skilled in the art and it is intended to encompass such obvious modifications and changes in the scope of the claims appended hereto.