Optical apparatus and projection apparatus

An optical apparatus provided with a light combining prism having three light incident faces, receiving the three beams of light having different wavelength bands through the three light incident faces, and combining the three incident beams of light for output, three reflection type polarization plates, three plate-like reflection type polarization elements provided corresponding to the three reflection type liquid crystal panels, each receiving a different wavelength band of light among the three different wavelength bands, each selecting a first polarized beam component to pass and making it strike the corresponding reflection type liquid crystal panel by two perpendicular polarized beam components, and each making modulated light spatially modulated and converted to a second polarized beam component at the reflection type liquid crystal panel strike the corresponding incident face among the three light incident faces of the combining prism, and at least three fixing plates with surfaces which can be joined with the three light incident faces of the light combining prism, wherein at least the reflection type polarization elements between the reflection type polarization elements and reflection type liquid crystal panels are fixed to the corresponding light incident faces of the light combining prism via the fixing plates, and a projection apparatus using the same.

CROSS REFERENCES TO RELATED APPLICATIONS

The present invention contains subject matter related to Japanese Patent Application No. 2004-258634 filed in the Japan Patent Office on Sep. 6, 2004, the entire contents of which being incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical apparatus for combining light modulated by a reflection type liquid crystal display device and to a projection apparatus using the same.

2. Description of the Related Art

Known in the art is a projection type display device for displaying projected image by spatially modulating and emitting incident light and focusing and projecting the emitted light according to an electric signal supplied to a spatial light modulation device. In general, a color display projection apparatus has an illumination optical system having a light source constituted by a lamp and a condensing mirror, splitting the light emitted from the light source to three wavelength bands, and condensing the split lights at corresponding spatial light modulation devices to illuminate, a light combining prism for combining lights modulated by spatial light modulation devices, and a projection lens for projecting the emitted light of the light combining prism to a screen etc. (the projection apparatus will be referred to as a “projector” hereinafter).

A liquid crystal projector uses spatial light modulation devices using liquid crystal materials (hereinafter, referred to as “liquid crystal panels”). As the projector, a transmission type projector passing light through the liquid crystal panels and modulating the light in the process of passing through the liquid crystal panels and a reflection type projector emitting light to the liquid crystal panels and modulating the light when reflected at the liquid crystal panels to change the polarization axes are known.

A reflection type liquid crystal projector using reflection type liquid crystal panels can be realized with small sized panels with a high resolution. A reflection type liquid crystal projector requires use of a polarization element able to combine and split two perpendicular linear polarized beams (s polarized light and p polarized light).

As such a polarization element, a polarized beam splitter constituted by a glass block is known (refer to Japanese Unexamined Patent Publication (Kokai) No. 2001-350024). As disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2001-350024, by forming a plurality of thin films between two pieces of glass, it becomes possible to split or combined two linear polarized beams.

However, such a polarized beam splitter constituted by a glass material is affected in characteristics by distortion of the glass, therefore low distortion glass must be used. For this, lead etc. must be dissolved in the glass resulting in glass having a very high specific gravity. There therefore arises the problem of increase of the weight.

As opposed to this, as a projector realizing a light weight reflection type liquid crystal panel optical system, a projector using a reflection type polarization plate has been proposed (refer to Japanese Unexamined Patent Publication (Kokai) No. 2003-508813). Japanese Unexamined Patent Publication (Kokai) No. 2003-508813 proposes a projector using a wire grid element forming a metal conductor in a lattice state to split incident light into two perpendicular linear polarized beams one of which passes through the plate and the other of which is reflected at the plate. In an optical system using such a reflection type polarization plate, a reduction of weight can be realized.

When using three reflection type liquid crystal panels, inputting the three primary colors of light to the panels, combining the modulated light again, a projector enabling full color display can be realized.

FIG. 1is a view of the schematic configuration of an optical system of a liquid crystal projector using three liquid crystal panels and able to display not a black and white, but a color image.

This liquid crystal projector10has, as shown inFIG. 1, a light source11having a lamp111and a condensing mirror112, an illumination optical system12, three reflection type liquid crystal panels13R,13G, and13B, a light combining prism14, and a projection lens15.

The illumination optical system12has a lens121oriented so that light output from the optical system having the function of aligning the light emitted from the light source11with a predetermined polarization (for example p polarization) is emitted toward the reflection type liquid crystal panels13R,13G, and13B, a dichroic mirror122for splitting it into light LR having a red wavelength region and light LGB having green and blue wavelength regions, a reflection mirror123for reflecting the red light LR split at the dichroic mirror122, a reflection mirror124for reflecting the green and blue light LGB split at the dichroic mirror122, a dichroic mirror125for reflecting only the green wavelength region in the light LGB reflected at the reflection mirror124and passing the blue wavelength region therethrough, a polarization plate126R for passing the p polarized red light LR reflected at the reflection mirror123therethrough to make it strike the reflection type liquid crystal panel13R and reflecting the red light spatially modulated and s polarized at the reflection type liquid crystal panel13R and making it strike the light combining prism14, a polarization plate126G for passing the p polarized green light LG reflected at the dichroic mirror125therethrough to make it strike the reflection type liquid crystal panel13G and reflecting the green light spatially modulated and s polarized at the reflection type liquid crystal panel13G and making it strike the light combining prism14, a polarization plate126B for passing the p polarized blue light LB reflected at the dichroic mirror125therethrough to make it strike the reflection type liquid crystal panel13B and reflecting the blue light spatially modulated and s polarized at the reflection type liquid crystal panel13B and making it strike the light combining prism14, and optical lenses127to129arranged at incident sides of the polarization plates126R,126G, and126B.

In the liquid crystal projector10, white light output from the light source11is made uniform by a not shown integrating optical system (integrator) and aligned with a predetermined polarization by a polarization conversion element (P-S converter). Then, the output light is oriented by the lens121of the illumination optical system11so as to strike the reflection type liquid crystal panels13R,13G, and13B and then split to three wavelength regions of light by the color splitting mirrors constituted by the dichroic mirrors122,125, etc. The split color beams of light strike the reflection type polarization plates. Only the light in a certain polarization direction is selected by the polarization plates126R,126G, and126B and strikes the reflection type liquid crystal panels13R,13G, and13B. The reflection type liquid crystal panels13R,13G, and13B are struck by RGB light.

Video signals (image signals) of colors corresponding to the incident light are supplied to the reflection type liquid crystal panels13R,13G, and13B, whereupon the incident light beams are rotated in polarization directions, modulated, and output according to the video signals. The modulated light beams emitted from the liquid crystal panels strike the polarization plates126R,126G, and126B again. Only the polarized light component rotated by 90 degrees is selected from among the polarized beams of light striking the polarization plates126R,126G, and126B and striking the light combining prism14. The color beams of light modulated at the three reflection type liquid crystal panels are combined and emitted to the same direction at the light combining prism14. The emitted combined light from the light combining prism14is output and projected to a screen etc. by the projection lens15.

SUMMARY OF THE INVENTION

In the above mentioned optical system using reflection type polarization plates there are the following disadvantages exist.

In the liquid crystal projector10, video light obtained by three reflection type liquid crystal panels13R,13G, and13B are passed through the reflection type polarization plates126R,126G, and126B and the light combining prism14for combining the video light, whereupon three images are superposed on the screen by the projection lens15. The positions of the liquid crystal panels are adjusted so that images of three panels are superposed on the screen, then the panels are fixed in place by a binder etc. After fixing them in place, if the reflection type liquid crystal panels or the members up to the projection lens move, there is the problem that the images of the liquid crystal panels will become deviated in position in the projected image on the screen. This will be referred to as “registration deviation”.

In the past, in an optical system using reflection type polarization plates, as shown inFIG. 2, a base chassis16has a light combining prism14affixed to it by bonding etc. Reflection type polarization plates126R,126G, and126B are then fixed onto the base chassis16to fix the positions of the reflection type polarization plates with respect to the light combining prism14.

However, the base chassis16is generally made of a metal member. As the metal member, if considering molding, aluminum (linear expansion coefficient of 23.5×10−6K−1) and magnesium (linear expansion coefficient of 27×10−6K−1) can be considered. However, both have relatively large thermal expansion coefficients (linear expansion coefficients). For this reason, a change in temperature of the air outside the apparatus etc. will cause the base chassis to expand/shrink resulting in a change in the positional relationship between the reflection type polarization plates and the combining prism and a high possibility of occurrence of registration deviation.

As described above, it is desired to realize an optical apparatus and projection apparatus able to suppress occurrence of registration deviation with a simple configuration.

According to a first aspect of an embodiment of the present invention, there is provided an optical apparatus comprising a light combining prism having three light incident faces, receiving the three beams of light having different wavelength bands through the three light incident faces, and combining the three incident beams of light for output; three reflection type liquid crystal panels; three plate-like reflection type polarization elements disposed corresponding to the three reflection type liquid crystal panels, each receiving a different wavelength band of light among the three different wavelength bands, each selecting a first polarized beam component and making it strike the corresponding reflection type liquid crystal panel, and each providing modulated light spatially modulated and converted to a second polarized beam component at the reflection type liquid crystal panel to the corresponding incident face among the three light incident faces of the light combining prism; and at least three fixing plates with surfaces which can be joined with the three light incident faces of the light combining prism, wherein at least the reflection type polarization elements between the reflection type polarization elements and reflection type liquid crystal panels are fixed to the corresponding light incident faces of the light combining prism via the fixing plates.

Preferably, each of the fixing plates is formed to a trigonal column, among the three side faces, one side face forms a joint surface with a light incident face of the light combining prism, a second side face forms a surface for attachment of the reflection type polarization element, and a third side face forms a surface for attachment of the reflection type liquid crystal panel, and the reflection type polarization elements and the reflection type liquid crystal panels are fixed to the corresponding light incident faces of the light combining prism via the fixing plates.

Preferably, the light incident faces of the light combining prism have optically transparent spacers joined to them, and the fixing plates are joined with the light incident faces in a state supported by side portions of the spacers.

Preferably, a plurality of the fixing plates are joined with the light incident faces of the light combining prism at predetermined intervals.

Preferably, the fixing plates have prism side brackets joined with them, the reflection type liquid crystal panels have panel side brackets fastened to them, and the prism side brackets and the panel side brackets are joined to thus fix the reflection type liquid crystal panels to the corresponding light incident faces of the light combining prism.

Preferably, the fixing plates have linear expansion coefficients of 10×10−6K−1or less. Preferably, the fixing plates are made of glass materials. Alternatively, the fixing plates are formed by stainless steel or FeNiCo.

According to a second aspect of an embodiment of the present invention, there is provided a projection apparatus comprising a light source, an optical apparatus for splitting light generated from the light source into three according to the wavelength bands, combining three modulated light beams and emitting the result, and a projecting portion for outputting and projecting the light emitted from the optical apparatus, wherein the optical apparatus has a light combining prism having three light incident faces, receiving the three beams of light having different wavelength bands through the three light incident faces, and combining the three incident beams of light for output; three reflection type liquid crystal panels; three plate-like reflection type polarization elements disposed corresponding to the three reflection type liquid crystal panels, each receiving a different wavelength band of light among the three different wavelength bands, each selecting a first polarized beam component and making it strike the corresponding reflection type liquid crystal panel, and each providing modulated light spatially modulated and converted to a second polarized beam component at the reflection type liquid crystal panel to the corresponding incident face among the three light incident faces of the light combining prism; and at least three fixing plates with surfaces which can be joined with the three light incident faces of the light combining prism, wherein at least the reflection type polarization elements between the reflection type polarization elements and reflection type liquid crystal panels are fixed to the corresponding light incident faces of the light combining prism via the fixing plates.

According to an embodiment of the present invention, plate-like (also including film-like) polarization elements are fixed to the light incident faces of the light combining prism via fixing plates having for example relatively low linear expansion coefficients.

According to an embodiment of the present invention, it becomes possible to prevent registration deviation of the liquid crystal projector by a simple structure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Principal Components of Projector

Below, an explanation will be given of a projector according to a first embodiment of the present invention with reference toFIG. 3. Note that the same notations as those ofFIG. 1are assigned for the illumination optical system having the same configuration as that explained inFIG. 1.

This liquid crystal projector100has, as shown inFIG. 3, a light source11having a lamp111and a condensing mirror112, an illumination optical system12, three reflection type liquid crystal panels201,202, and203, a first polarized beam filters (PBF)261, a second PBF262, a third PBF263, a light combining prism210, and a projection lens216.

The illumination optical system12has a lens121oriented so that light output from the optical system having the function of aligning the light emitted from the light source11with a predetermined polarization (for example p polarization) is emitted toward the reflection type liquid crystal panels201,202, and203, a dichroic mirror122for splitting it into light LR having a red wavelength region and light LGB having green and blue wavelength regions, a reflection mirror123for reflecting the red light LR split at the dichroic mirror122, a reflection mirror124for reflecting the green and blue light LGB split at the dichroic mirror122, a dichroic mirror125for reflecting only the green wavelength region in the light LGB reflected at the reflection mirror124, and passing the blue wavelength region therethrough, a first PBF261for passing the p polarized red light LR reflected at the reflection mirror123to make it strike the reflection type liquid crystal panel201and reflecting the red light spatially modulated and s polarized at the reflection type liquid crystal panel201to make it strike the light combining prism210, a second PBF262for passing the p polarized green light LG reflected at the dichroic mirror125to make it strike the reflection type liquid crystal panel202and reflecting the green light spatially modulated and s polarized at the reflection type liquid crystal panel202to make it strike the light combining prism210, a third PBF263for passing the p polarized blue light LB reflected at the dichroic mirror125to make it strike the reflection type liquid crystal panel203and reflecting the blue light spatially modulated and s polarized at the reflection type liquid crystal panel203to make it strike the light combining prism21Q, and optical lenses127to129arranged on incident sides of the first, second, and third PBFs261,262, and263.

The first, second, and third PBFs261,262, and263and the reflection type liquid crystal panels201,202, and203are fixed to corresponding light incident faces of the light combining prism210via the fixing plates310-1,310-2, and310-3.

In the liquid crystal projector100, white light output from the light source11is integrated by a not shown integration optical system (integrator) and aligned with a predetermined polarization by a polarization conversion element (P-S converter). The output light is oriented by the lens121of the illumination optical system11so as to strike the reflection type liquid crystal panels201,202, and203, then is split to three wavelength regions of light by the color splitting mirrors constituted by the dichroic mirrors122,125, etc. The split color beams strike the reflection type polarization plates. Only light in a certain polarization direction is selected by the first, second, and third PBFs261,262, and263and strikes the reflection type liquid crystal panels201,202, and203. The reflection type liquid crystal panels201,202, and203are struck by RGB light.

Video signals (image signals) of colors corresponding to incident light are supplied to the reflection type liquid crystal panels201,202, and203, whereupon the incident light beams are rotated in polarization directions, modulated, and output according to the video signals. The modulated light beams emitted from the liquid crystal panels strike the PBFs261,262, and263again. Only the polarized beam component rotated by 90 degrees is selected from among the polarized beams striking the PBFs261,262, and263and striking the light combining prism210. The color beams modulated at the three reflection type liquid crystal panels are combined to the same direction at the light combining prism210and emitted. The emitted combined light from the light combining prism210is output and projected to a screen etc. by the projection lens216.

Structure of Optical Apparatus

First, an explanation will be given of structures for attachment of PBFs of an optical apparatus300.

FIGS. 4A and 4Bare views for explaining incident faces and an emitting face of the light combining prism.

The light (color) combining prism210is constituted by joining for example a plurality of glass prisms (four right-angled isosceles prisms having substantially the same shapes) and two interference filters having predetermined optical characteristics formed at the joined surfaces of the glass prisms. A first interference filter reflects the blue light and allows the red light and green light to pass herethrough. A second interference filter reflects the red light and allows the green light and blue light to pass therethrough. Accordingly, the beams of colored light modulated by the reflection type liquid crystal panels201,202, and203are combined and strike the projection lens216.

The light combining prism210has a cube or rectangular parallelopiped shape. A first face2101forms an incident face of the light reflected at the third PBF263and modulated by the liquid crystal panel203, a second face2102perpendicular to the first face2101forms an incident face of the light reflected at the second PBF262and modulated by the liquid crystal panel202, and a third face2103facing the first face2101and perpendicular to the second face2102forms an incident face of the light reflected at the first PBF261and modulated by the liquid crystal panel201. Also, in the light combining prism210, a fourth face2104perpendicular to the first face2101and the third face2103and facing the second face2102forms the emitting face of the combined light.

In the present embodiment, the three incident faces of the light combining prism210constituted by the first face2101, the second face2102, and the third face2103have fixing plates formed by for example glass materials joined to them. The first to third PBFs261to263and the reflection type liquid crystal panels201to203are attached to these fixing plates.

FIG. 5is a view of an example of the configuration of a fixing plate according to the present embodiment. The fixing plate310is formed by, as shown inFIG. 5, for example a trigonal columnar plate having a side cross-section forming a right-angled isosceles triangle. Among three side faces311to313, the side face311is the face contacting the light combining prism, the side face312is the face contacting the reflection type polarization element constituted by the PBF, and the side face313becomes a face holding the reflection type liquid crystal panel.

FIG. 6is a view of a state where fixing plates are joined with three incident faces of the light combining prism.

The light combining prism210and the fixing plate310are joined as shown inFIG. 6. In the example of this figure, one incident face of the light combining prism210has two fixing plates joined to its upper end lower edges inFIG. 6. Specifically, side faces311of fixing plates310-1U and310-1B having the same shape and same size are joined to the first face2101of the light combining prism210by a binder etc. Side faces311of fixing plates310-2U and310-2B having the same shape and same size are joined to the second face2102of the light combining prism210by a binder etc. Side faces311of fixing plates310-3U and310-3B having the same shape and same size are joined to the third face2103of the light combining prism210by a binder etc.

At this time, faces312for joining the reflection type polarization elements constituted by the first to third PBFs261to263of each two fixing plates310-1U and310-1B,310-2U and310-2B, and310-3U and310-3B attached to the same incident faces of the light combining prism210are parallel or substantially parallel and located on substantially the same plane in perpendicular directions.

FIGS. 7A and 7Bare views of a state where reflection type polarization elements constituted by the PBFs are attached to the fixing plates.

As shown inFIGS. 7A and 7B, the reflection type polarization elements constituted by the first to third PBFs261to263are attached to faces312for joining the reflection type polarization elements of each two fixing plates310-1U and310-1B,310-2U and310-2B, and310-3U and310-3B.

FIGS. 8A and 8Bare views of a state where the reflection type liquid crystal panels constituted by the PBFs are attached to the fixing plates.

As shown inFIGS. 8A and 8B, the reflection type liquid crystal panels201,202, and203are attached to the faces313for holding the reflection type liquid crystal panels of each two fixing plates310-1U and310-1B,310-2U and310-2B, and310-3U and310-3B by for example a binder.

FIGS. 9A and 9Bare views of an example of a preferred structure for attachment of the reflection type liquid crystal panels with respect to the fixing plates.

In order to adjust the positions of and fix the three reflection type liquid crystal panels201,202, and203so that their projection positions become equal, a structure as in for exampleFIGS. 9A and 9Bis employed. “Prism side brackets320U and320B” are joined to the fixing plates310U and310B. “Panel side brackets321U and321B” are fixed to the reflection type liquid crystal panels201to203by screws etc. Then, the prism side brackets320U and320B and the panel side brackets321U and321B are joined. The prism side brackets320U and320B are formed so that their cross-sections form schematically L-shapes and can stably support the fixing plates310U and310B.

As the advantages of the attachment structure ofFIGS. 9A and 9B, it can be mentioned that only screws322-1U,322-2U,322-1B, and322-2B need be detached for detaching the panel side brackets and the liquid crystal panels when replacing the liquid crystal panels. This is because a liquid crystal panel is expensive and the re-use is desired. As shown inFIGS. 8A and 8B, if this is directly connected to the fixing plate310, after the liquid crystal panel is detached, it becomes necessary to remove the binder, solder, etc. used for joining them when re-using it.

Note that the panel side brackets may also be directly fixed to the fixing plates without using the prism side brackets.

As described above, in the present embodiment, the light combining prism210has the three reflection type liquid crystal panels201to203and the reflection type polarization elements constituted by the PBFs261to263joined and fixed to it by the fixing plates310U and310B. The fixing plates are made of glass materials. In the case of the related art, a material having a large linear expansion coefficient such as magnesium and aluminum was used, therefore the positions of the projected images of the three liquid crystal panels sometimes became deviated due to outer disturbance such as a temperature change. In the present embodiment, by fixing the reflection type liquid crystal panels201to203and the reflection type polarization elements constituted by the PBFs261to263to the light combining prism210by the same fixing plates310, movements of the liquid crystal panels and/or reflection type polarization elements due to thermal expansion etc. are small. By forming the fixing plates310by a material having a linear expansion coefficient less than 10×10−6K−1such as a glass material, the amounts of movement are greatly reduced.

FIGS. 10 to 14are views for explaining a further preferred structure for attaching the reflection type polarization elements constituted by the PBFs and the reflection type liquid crystal panels to the fixing plates.

In such an attachment structure, first, as shown inFIG. 10andFIG. 11, transparent base plates (columnar shaped)331to333are joined to the light incident faces2101,2102, and2103of the light combining prism210. These base plates331to333are shorter than the height of the light combining prism210. Namely, the fixing plates310are formed on the upper end lower edges of the surfaces2101,2102, and2103so that they can be reliably supported by the faces of the light combining prism210and the transparent base plates331to333. Here, the transparent base plates331to333will be referred to as “glass spacers”.

Next, as shown inFIG. 12andFIG. 13, single faces of the glass spacers331to333are made to abut against and are joined with the faces formed by incident faces2101,2102, and2103of the light combining prism210. The other fixing plates are joined in the same way. Due to this, each fixing plate can be joined between the two faces of one face of a fixing plate and an incident face of the combining prism210without interposing another holding member etc., and a stable joint with a high precision becomes possible.FIG. 14illustrates a case where the reflection type liquid crystal panel is attached.

Also, by such a configuration, space required for attachment etc. can be provided between for example the liquid crystal panel202and the light combining prism210, and an increase of back focus of the projection lens216can be reduced.

Namely, the refractive index of air and the refractive index N of the glass spacers331to333are different, therefore light passing through interfaces between the air layer and the glass spacers331to333is refracted. This refraction phenomenon is based on Snell Law of Refraction. For this reason, the optical distance from the projection lens216to the liquid crystal panel (in the case of conversion assuming the medium to be air) becomes shorter in the case of provision of the glass spacers331to333. When providing glass spacers331to333having a thickness of for example d, the distance becomes shorter by exactly an air conversion length of d(1−1/N). Due to this, the back focus of the projection lens216can be made shorter than that in the case where the glass spacers331to333are not provided.

Note that, the fixing plates310are formed by glass material/quartz/FeNiCo etc. The linear expansion coefficient is 10×10−6K−1.

By employing the above attachment structure, it becomes possible to prevent registration deviation of the liquid crystal projector by a simple structure. Namely, registration deviation occurs due to the deviation of incident angles with respect to reflection faces210aand210bof the light combining prism210. By using incident faces2101,2102, and2103of the light combining prism210machined with a high precision as reference surfaces and holding the PBFs261to263upon the fixing plates joined to the incident faces, the position deviation due to the change of temperature of at least the PBFs261to263which becomes the cause of the deviation of incident angles with respect to the reflection faces210aand210bcan be suppressed to the minimum as a change of the dimensions of the small sized fixing plates310.

Note that, in the above explanation, the example of use of an apparatus in which fixing plates310were individually formed was shown, but as shown inFIG. 15, it is also possible to apply the invention to an apparatus in which the fixing plates are integrally formed. In this case, by applying it to an attachment structure with reference toFIG. 10toFIG. 14, simplification of the attachment process can be achieved, so this is practical.

FIGS. 16A and 16Bare perspective views of a liquid crystal projector employing an optical apparatus according to a second embodiment of the present invention.FIG. 17is a view of an example of the configuration of the light source which can be applied to the projector illustrated inFIGS. 16A and 16B.FIG. 18is a view of a state where reflection type liquid crystal panels are attached to fixing plates in the second embodiment.FIG. 19is a view illustrating an example of the partial configuration and beam trace in the projector illustrated inFIGS. 16A and 16B.FIG. 20is a view schematically showing an arrangement of the optical system around a cross prism provided in the projector illustrated inFIGS. 16A and 16B.

Principal Components of Projector

InFIGS. 16A and 16B, a projector200has a light combining prism (hereinafter referred to as a “cross prism”)210A at an illustrated center portion and a projection lens216A in front of that. The projector200has the following optical systems in the three directions in total of the two sides of the light combining prism210A and a side facing the projection lens216A across the light combining prism210A. InFIGS. 16A and 16B, on the left side of the light combining prism210A, as a first optical system, provision is made of a first reflection type liquid crystal panel201A, a first PBF261A, a first linear polarization plate211, and a first 1/n (n is an integer of 2 or more) wavelength plate221. InFIGS. 16A and 16B, on the side facing the projection lens216A across the light combining prism210A, as a second optical system, provision is made of a second reflection type liquid crystal panel202A, a second PBF262A, and a second linear polarization plate212. InFIGS. 16A and 16B, on the right side of the light combining prism210A, as a third optical system, provision is made of a third reflection type liquid crystal panel203A, a third PBF263A, a third linear polarization plate213, and a third 1/n wavelength plate223.

The optical apparatus300according to the embodiment of the present invention is formed by the light combining prism210A, the first optical system having the first reflection type liquid crystal panel201A, the first PBF261A, the first linear polarization plate211, and the first 1/n wavelength plate221, the second optical system having the second reflection type liquid crystal panel202A, the second PBF262A, and the second linear polarization plate212, and the third optical system having the third reflection type liquid crystal panel203A, the third PBF263A, the third linear polarization plate213, and the third 1/n wavelength plate223.

Note that, in the second optical system, the second wavelength plate corresponding to the first and third wavelength plates221and223is not provided. The reason for that will be explained next. When three primary colors are combined in the light combining prism210A, for two primary colors among the three primary colors, in the example ofFIG. 20, light271mstriking a reflection face210a′ in the light combining prism210A from the first optical system and light273mstriking the reflection face210b′ in the light combining prism210A from the third optical system are reflected at the reflection faces210a′ and210b′ in the light combining prism210A and thereby changed in phases by 90 degrees. On the other hand, the light striking the light combining prism210A from the second optical system is not reflected in the light combining prism210A. In order to adjust such phase inversion, the first optical system and the third optical system are provided with 1/n wavelength plates221and223. It is not necessary to provide the 1/n wavelength plate for the second optical system.

How the two primary colors among the three primary colors are selected can be suitably selected. Note that, in the light combining prism210A, the s polarized beam is suitable for reflection, and the p polarized beam is suitable for transmission. Accordingly, in the present embodiment, the polarization state is selected as exemplified.

The light combining prism210A and the projection lens216A are arranged on substantially the same plane. Sandwiching the light combining prism210A, the first PBF261A, the first linear polarization plate211, and the first 1/n wavelength plate221of the first optical system, the second PBF262A and the second linear polarization plate212of the second optical system, and the third PBF263A, the third linear polarization plate213, and the third 1/n wavelength plate223of the third optical system are arranged on substantially the same planes. In this way, the optical systems constituting the projector200are disposed (arranged) on substantially the same planes while sandwiching the light combining prism210A between them.

The projector200of this embodiment of the present invention has three types of light sources251to253outputting three primary colors, that is, blue (B) light, green (G) light, and red (R) light, in addition to the components (optical parts) of the optical systems explained above. Details thereof will be explained in detail later.

In the present embodiment, each of the three reflection type liquid crystal panels201A to203A functions to spatially modulate light of one color among the three primary colors, that is, the blue (B) light, green (G) light, and red (R) light. The configurations of these reflection type liquid crystal panels201A to203A are substantially the same except that the 1/n wavelength plate is not provided in the second optical system. It can be arbitrarily determined which among them to spatially modulate each of the blue B light, green (G) light, and red (R) light. Namely, it can be arbitrarily designed which primary color light is to be modulated by each of the first reflection type liquid crystal panel201A, the second reflection type liquid crystal panel202A, and the third reflection type liquid crystal panel203A.

The present embodiment will explain as an example a case where the first reflection type liquid crystal panel201A is made to function as a red reflection type liquid crystal panel for modulating the image of the red light, the second reflection type liquid crystal panel202A is made to function as a green reflection type liquid crystal panel for modulating the image of the green light, and the third reflection type liquid crystal panel203A is made to function as a blue reflection type liquid crystal panel for modulating the image of the blue light. Naturally, for this purpose, a not shown image signal processing apparatus outputs an image signal for modulating the red color to the red reflection type liquid crystal panel201A, an image signal for modulating the green color to the green reflection type liquid crystal panel202A, and an image signal for modulating the blue color to the blue reflection type liquid crystal panel203A in accordance with the image display content. Note that a detailed description of the image signal processing apparatus will be omitted.

Structure of Optical Apparatus

Next, the configuration of an optical apparatus used in the projector200will be shown. As described above,FIG. 18is a view of a state where the reflection type liquid crystal panels are attached to the fixing plates in the projector200. As shown inFIG. 18, the reflection type polarization elements constituted by the first to third PBFs261A to263A are attached to faces312A for joining each two (pair of) fixing plates310A-1,310A-2, and310A-3. Also, the reflection type liquid crystal panels201A,202A, and203A are attached to the side above the light combining prism211A (same side) with respect to the faces holding reflection type liquid crystal panels of each two (pair of) fixing plates310A-1,310A-2, and310A-3by for example a binder.

By employing such a configuration, when the ambient temperature changes, even when there is positional deviation (angle deviation) of the PBFs261A to263A due to the changes in dimensions of the fixing plates310A, positional deviation of the projected video accompanying occurs in the same direction for the reflection type liquid crystal panels201A,202A, and203A, therefore no registration deviation substantially occurs or is further reduced for the superposed videos.

Light Source

The projector200has a red illumination light source251for emitting red light271perpendicular to the surface of the red reflection type liquid crystal panel201A, a green illumination light source252for emitting green light272perpendicular to the surface of the green reflection type liquid crystal panel202A, and a blue illumination light source253for emitting blue light273perpendicular to the surface of the blue use reflection type liquid crystal panel203A. Various configurations and arrangements of these red illumination light source251, green illumination light source252, and blue illumination light source253are possible, but in the present embodiment, use can be made of the configuration exemplified inFIG. 17. Note that in the image projection apparatus of the embodiment of the present invention, the light source is not an indispensable factor and can be of various forms other than that illustrated inFIG. 17. Accordingly, the light source illustrated inFIG. 17is only an example.

A light source500illustrated inFIG. 17has a lamp501outputting a white beam, fly eye integrators502and503, a PS conversion element504for converting p polarization and s polarization, a red reflection dichroic mirror506, a green and blue reflection dichroic mirror507, all reflection mirrors508,509,512,511, and513, and condenser lenses515and516.

The white beam emitted from the lamp501becomes illumination light integrated by the fly eye integrators502and503and is aligned in polarization direction by the PS conversion element504. The white illumination light520aligned in polarization direction in the PS conversion element504is condensed toward the reflection type liquid crystal panels201A to203A by a main condenser lens505. The white light520is split by the red reflection dichroic mirror506and the green and blue reflection dichroic mirror507to a blue color, green color, and red color. The red reflected light521reflected at the red reflection dichroic mirror506is changed in its orientation (polarized) by the all reflection mirror509, condensed by the condenser lens516, is reflected at the all reflection mirror513toward the direction of the red reflection type liquid crystal panel201A located above this light source500, and becomes the red light271. The reflected light522having green and blue spectrum reflected at the green and blue reflection dichroic mirror507is changed in its orientation (polarized) by the all reflection mirror508and reaches the green reflection dichroic mirror510. Due to this green reflection dichroic mirror510, the green light is reflected and changed in its orientation (polarized) to the direction of the all reflection mirror511, is changed in its orientation to the upward direction of the light source500.bythe all reflection mirror511, is condensed toward the green reflection type liquid crystal panel202A of the projector100by the condenser lens514, and becomes the green light272. The light reflected at the all reflection mirror508is condensed at the condenser lens515and condensed toward the blue reflection type liquid crystal panel203A of the projector100by the all reflection mirror512to become the blue light273.

In the present specification and drawings, for convenience, in the light source500illustrated inFIG. 17, the portion for outputting the red light271will be called the “red illumination light source251”, the portion for outputting the green light272will be called the “green illumination light source252”, and the portion for outputting the blue light273will be called the “blue illumination light source253”, illustrated by the broken lines inFIGS. 16A and 16B.

FIG. 19is a sectional view illustrating the positional relationships among the first reflection type liquid crystal panel201A, the red illumination light source251, and the first PBF261A disposed between them as representative in an enlarged manner. As illustrated inFIG. 19, the illustrated projector200has a first PBF261A arranged between the red illumination light source251and the red reflection type liquid crystal panel201A in a state inclined by 45 degrees on the surface of the red reflection type liquid crystal panel201A. The first PBF261A is also arranged in a state inclined by substantially 45 degrees with respect to the red light271which is output from the red illumination light source251and incident upon the red reflection type liquid crystal panel201A substantially perpendicular to the plane.

In the same way as above, the projector200has a second PBF262A arranged between the green illumination light source252and the green reflection type liquid crystal panel202A in a state inclined by 45 degrees on the surface of the green reflection type liquid crystal panel202A. The second PBF262A is arranged in a state inclined by substantially 45 degrees also with respect to the green light272which is output from the green illumination light source252and incident upon the green reflection type liquid crystal panel202A substantially perpendicular to the plane. Also, in the same way as above, the projector200has a third PBF263A arranged between the blue illumination light source253and the blue reflection type liquid crystal panel203A in a state inclined by 45 degrees on the surface of the blue reflection type liquid crystal panel203A. The third PBF263A is also arranged in the state inclined by substantially 45 degrees with respect to the blue light273which is output from the blue illumination light source253and incident upon the blue reflection type liquid crystal panel203A substantially perpendicular to the plane.

Red Beam Trace

Next, a detailed description will be given of the relationships among the red reflection type liquid crystal panel201A, the red illumination light source251, and the first PBF261A with reference toFIGS. 19A and 19B. The red illumination light source251emits red light271perpendicular to the surface of the red reflection type liquid crystal panel201A through the first PBF261A. In the present embodiment, the red illumination light source251emits the red light271toward the red reflection type liquid crystal panel201A from the bottom portion of the red reflection type liquid crystal panel201A. The red light271output from the red illumination light source251passes through the first PBF261A having the p polarization axis parallel to the sheet surface and strikes the red reflection type liquid crystal panel201A. As illustrated inFIG. 19A, when the red light271is not modulated at the red reflection type liquid crystal panel201A, the red light271having the p polarization axis is reflected at the red reflection type liquid crystal panel201A, strikes the first PBF261A again as it is, and returns to the red illumination light source251. As illustrated inFIG. 19B, on the other hand, when the red light271is modulated at the time of reflection at the red reflection type liquid crystal panel201A, the red light271having the p polarization axis parallel to the sheet surface becomes the red modulated light271mhaving the s polarization axis vertical to the sheet surface and striking the first PBF261A, is reflected at the first PBF261A to the light combining prism210A side, passes through the first linear polarization plate211and the first 1/n wavelength plate221, and goes toward the light combining prism210A.

In the red illumination light source251, the polarization axis is previously adjusted so as to output red light271that has the illustrated polarization axis (axis parallel to the figure) so as to become a p polarized beam with respect to the first PBF261A. The orientation of the first PBF261A is set to one that allows the p polarized beam with respect to the first PBF261A to pass therethrough and reflects the s polarized beam. Accordingly, the red light271emitted from the red illumination light source251having the illustrated polarization axis passes through the first PBF261A and strikes the red reflection type liquid crystal panel201A.

The red reflection type liquid crystal panel201A, the green reflection type liquid crystal panel202A, and the blue reflection type liquid crystal panel203A are set so as to modulate their polarization planes so that these reflection panels201A to203A do not rotate the polarization planes of the incident light when 0% black color is displayed, while rotate the polarization planes of the incident light by substantially 90 degrees when 100% of blue, red, and green are displayed. Which color of display is carried out by modulation work performed by the reflection type liquid crystal panels201A to203A depends upon the image signals input to these reflection type liquid crystal panels201A to203A from for example an image signal processing apparatus (not shown).

As illustrated inFIG. 19A, when the red reflection type liquid crystal panel201A displays 0% black, the red light271passes through the first PBF261A and strikes the red reflection type liquid crystal panel201a, but is reflected at the red reflection type liquid crystal panel201A as it is, passes through the first PBF261A again, and returns to the red illumination light source251side.

As illustrated inFIG. 19B, in the case of 100% red display of the red reflection type liquid crystal panel201A, the red light271passes through the first PBF261A, strikes the red reflection type liquid crystal panel201A, and is reflected at the red reflection type liquid crystal panel201a-during which time it is rotated in its polarization axis by 90 degrees by the red reflection type liquid crystal panel201A, therefore becomes the red modulated light271mhaving the p polarization axis, and the polarization axis of the red modulated light271mat that time becomes the s axis perpendicular to the sheet surface, becomes the s polarized beam with respect to the first PBF261A, is reflected at the first PBF261A, passes through the first linear polarization plate211, and advances to the direction of the light combining prism210A through the first 1/n wavelength plate221. The red modulated light271passes through the first linear polarization plate211and the first 1/n wavelength plate221arranged between the first PBF261A and the prism210A before striking the light combining prism210A in this way. The polarized beam transmission axis of the first linear polarization plate211is set to substantially the same orientation as that of the s polarized beam with respect to the first PBF261A, and the red modulated light271mcan pass through the first linear polarization plate211as it is. The axis of the first 1/n wavelength plate221is set so as to form an angle of 45 degrees with respect to its polarization axis. The polarization axis of the red modulated light271mpassed through the first 1/n wavelength plate221becomes an orientation which becomes the s polarized beam with respect to the reflection face of the light combining prism210A.

As illustrated inFIG. 20, the reflection face210a′ of the light combining prism210A is formed (coated) with a coating for reflecting the red color. The red modulated light271mis reflected at the reflection face210a′, goes toward the projection lens216A, and is imaged (projected) onto the screen (not shown) located in front of the projection lens216A.

Blue Beam Trace

Next, a description will be given of the blue beam trace (path). The blue beam trace is basically the same as the red beam trace described above. The blue light273output from the blue illumination light source253located beneath the blue reflection type liquid crystal panel203A and the third PBF263A passes through the third PBF263A and strikes the blue reflection type liquid crystal panel203A. The polarization axis is previously adjusted so that the blue light273has a polarization axis so that it becomes a p polarized beam with respect to the third PBF263A. The third PBF263A is set in orientation so that it passes the p polarization axis with respect to the third PBF263A and reflects the s polarized beam, therefore passes the blue light273having the above polarization axis and makes it strike the blue reflection type liquid crystal panel203A.

In the case of 0% black display of the blue reflection type liquid crystal panel203A, the blue light273passed through the third PBF263A and striking the blue reflection type liquid crystal panel203A is reflected at the blue reflection type liquid crystal panel203A as it is and passes through the third PBF263A again while keeping the p polarization axis as it is so as to return to the blue illumination light source253side.

In the case of 100% blue display of the blue reflection type liquid crystal panel203A, the blue light273passed through the third PBF263A and striking the blue reflection type liquid crystal panel203A is rotated in its polarization axis by 90 degrees when reflected at the blue reflection type liquid crystal panel203A and becomes the blue modulated light273mhaving the s polarization axis. This blue modulated light273mhas a polarization axis which becomes the s polarized beam and becomes the s polarized beam with respect to the third PBF263A, therefore is reflected at the third PBF263A, passes through the third linear polarization plate213and the third 1/n wavelength plate223, and advances in the direction of the light combining prism210A. In this way, the blue modulated light273mpasses through the third linear polarization plate213and the third 1/n wavelength plate223arranged between the third PBF263A and the light combining prism210A before striking the light combining prism210A. The third linear polarization plate213has the polarized beam passage axis set to schematically the same orientation as that of the s polarized beam with respect to the third PBF263A, so the blue modulated light273mcan pass as it is. The third 1/n wavelength plate223is set in its axis so as to exhibit an angle of 45 degrees with respect to its polarization axis. The polarization axis of the blue modulated light273mpassed through this gets an orientation which becomes the s polarized beam with respect to the reflection face of the light combining prism210A. Also, the reflection face210b′ of the prism210A is formed with a coating for reflecting the blue color. The blue modulated light273mis reflected at the reflection face210b′ and goes toward the projection lens216A where it is imaged (projected) onto the screen by the projection lens216A.

Green Beam Trace

Next, a description will be given of the green beam trace (path). The green beam trace is also basically the same as the blue beam trace described above. The green light272output from the green illumination light source252located beneath the green reflection type liquid crystal panel202A and the second PBF262A passes through the second PBF262A and strikes the green reflection type liquid crystal panel202A. The green light272output from the green illumination light source252is previously adjusted in polarization axis so as to have a polarization axis that becomes a p polarized beam with respect to the second PBF262A. The second PBF262A is set in orientation so as to pass the p polarized beam with respect to the second PBF262A therethrough and reflects the s polarized beam, therefore the second PBF262A passes the green light272having the polarization axis of the s polarized beam therethrough and makes it strike the green reflection type liquid crystal panel202A.

In the case of 0% black display of the green reflection type liquid crystal panel202A, the green light272is reflected at the green reflection type liquid crystal panel202A as it is and passes through the second PBF262A again while keeping the p polarization axis as it is, then returns to the green illumination light source252side.

In the case of 100% green display of the green reflection type liquid crystal panel202A, the green light272passes through the second PBF262A and is rotated in its polarization axis by 90 degrees when reflected at the green reflection type liquid crystal panel202A, so becomes the green modulated light272mhaving the polarization axis of the s polarized beam. The green modulated light272mhas the polarization axis of the s polarized beam and becomes an s polarized beam. Since it becomes an s polarized beam with respect to the second PBF262A, it is reflected at the second PBF262A and advances in the direction of the light combining prism210A. The green modulated light272mpasses through the second linear polarization plate212arranged between the second PBF262A and the light combining prism210A before striking the light combining prism210A. The second linear polarization plate212has a polarized beam passage axis set to substantially the same orientation as that of the s polarized beam with respect to the second PBF262A, so the green modulated light272mcan pass through the second linear polarization plate212as it is.

Note that, as mentioned above, the second optical system is not provided with the second wavelength plate corresponding to the first and third polarization plates. The reflection faces210a′ and210b′ of the light combining prism210A have coatings reflecting blue color and red color formed thereon, but the reflection faces210a′ and210b′ allow the green color to pass therethrough, therefore the green modulated light271mincident upon the prism210A is passed and goes toward the direction of the projection lens216A where it is imaged (projected) onto the screen by the projection lens216A.

Evaluation

FIG. 21Ais a graph illustrating the relationships between the wavelengths λ and transmittances μ of the first PBF261A to the third PBF263A (also referred to as the “PBFs”) used for the projector200for the incident angles 45° and 55° upon for example the red reflection type liquid crystal panel201A of the red light271.FIG. 21Bis a graph illustrating the relationships between the wavelengths λ and transmittances μ of the polarized beam splitters used for a projector in related art for the incident angles 45° and 55° upon for example the red reflection type liquid crystal panel of the red light.

(1) When comparing a PBS and a PBF, a PBF has a very low wavelength dependency in comparison with a PBS. Namely, when PBFs are used, all of blue, green, and red having different wavelengths have the same degree of transmittance, therefore there is a little change of the transmittance due to the wavelength difference depending upon the type of the three primary colors. As a result, for example the levels of colors arriving at the prism210A become the same condition. In this way, according to the embodiment of the present invention, there is little reduction of the luminance and little reduction of the contrast. In other words, in comparison with a projector using PBS's, the F number of the projector200according to the embodiment of the present invention using the PBFs becomes small, resulting in a higher luminance and higher contrast also.

(2) A PBF has lower incident angle dependency than a PBS. Accordingly, in the projector200of the embodiment of the present invention using PBFs, even when there is a little inclination in the incident light upon the reflection type liquid crystal panels201A to203A, there is little reduction of the transmittance (little fluctuation of transmittance). As a result, for example, room is obtained in the arrangement of for example the red illumination light source251and the red reflection type liquid crystal panel201A and the first PBF261A. Namely, even when the optical arrangement of the red illumination light source251, the first PBF261A, and the red reflection type liquid crystal panel201A is slightly deviated, there is little reduction of the luminance and reduction of the contrast. As a result, fine adjustment of positions of optical parts after assembling the optical system etc. becomes unnecessary.

When considering the configuration or structure of the projector200illustrated inFIGS. 16A and 16B, as schematically illustrated inFIG. 20, three optical systems for the three primary colors are arranged in an orderly manner on the periphery of the light combining prism210A. When planarly considering this, for example, the first optical system for the red color (red reflection type liquid crystal panel201A, first PBF261A, first linear polarization plate211, first 1/n wavelength plate221) is arranged on the left side of the light combining prism210A, the second optical system for the green color (green reflection type liquid crystal panel202A, second PBF262A, second linear polarization plate212, second 1/n wavelength plate222) is arranged on the right side of the light combining prism210A, and the third optical system for the blue color (blue reflection type liquid crystal panel203A, third PBF263A, third linear polarization plate213) is arranged on the side opposite to the projection lens216A across the light combining prism210A. These three optical systems are arranged in the three directions of the light combining prism210A in that order. When cubically considering this, the above three optical systems are arranged at the same planar positions on the surface of the light combining prism210A, therefore the dimension of the projector200in the height direction can be made smaller. In such an arrangement, no additional optical system for dividing the red light271, green light272, and blue light273, for example, an all reflection mirror etc., is necessary. When considering the above description, the design of the layout of the projector200is easy, and also the efficiency of accommodation of the components is high, therefore the projector can be made compact, and a reduction in size and weight can be achieved.

A PBF is smaller in size and lighter in weight in comparison with a PBS. As a result, a further reduction in size and weight of the projector200can be achieved.

In the projector, the lamp portion of the light source and the liquid crystal panel portion consume large electric power and become high in temperature, therefore have to be cooled. In the projector200illustrated inFIGS. 16A and 16BandFIG. 17, image signals are applied to the red reflection type liquid crystal panel201A, the green reflection type liquid crystal panel202A, and the blue reflection type liquid crystal panel203A to drive the liquid crystal panels, therefore the power consumption in the projector200is large and the temperature becomes high, so cooling becomes necessary. Naturally, also the lamp510portion of the light source500consumes much electric power and becomes high in temperature, so becomes necessary to cool. In the cooling of the red reflection type liquid crystal panel201A, the green reflection type liquid crystal panel202A, and the blue reflection type liquid crystal panel203A, since these are arranged at the same height, cooling countermeasures are easy. For example, cooling air is blown in from a cooling fan in a horizontal direction along the surfaces of these reflection type liquid crystal panels201A to203A. The cooling effect is also high.

In the example illustrated inFIGS. 16A and 16B, all of the red illumination light source251, green illumination light source252, and blue illumination light source253can be constituted by for example a single light source500exemplified inFIG. 17, while the red illumination light source251, the green illumination light source252, and blue illumination light source253, that is, the light source500, are located beneath the prism210A and the three optical systems. In this way, the light source500and the optical system can be cubically separated, therefore the cooling countermeasures can be separately carried out.

The amount of heat radiation of the lamp501of the light source500and the amounts of heat radiation of the reflection type liquid crystal panels201A to203A are very different from each other. The amount of heat radiation of the lamp501is overwhelmingly larger. As mentioned above, the optical system including the light source500and the reflection type liquid crystal panels201A to203A can be separately arranged, therefore the influence of heat of the lamp501of the light source500which may be exerted upon the reflection type liquid crystal panels201A to203A can be prevented. Accordingly, the reflection type liquid crystal panels201A to203A may be designed considering only cooling countermeasures for themselves. It is not necessary to consider useless cooling countermeasures. From that viewpoint, the cooling fan may be made small in size, and the projector200can be further made small in size and light in weight. Also, the noise of the cooling fan is low.

When the apparatus is configured with the light source500, especially the lamp501, arranged outside of the housing of the projector200accommodating the components illustrated inFIGS. 16A and 16Band only the white beam520from the lamp501is introduced, the cooling countermeasures become very easy.

The wiring connectors of the reflection type liquid crystal panels201A to203A (portions illustrated showing a large number of cables connected) are oriented in different directions. In addition, the reflection type liquid crystal panels201A to203A are located in the top part, therefore the wiring to the wiring connectors is easy. The number of cables to the reflection type liquid crystal panels201A to203A becomes considerably large, therefore the mounting surface has a big effect. In this way, according to the projector200, there also are obtained the effects that laying the wiring is easy, little space is required for wiring, and compact wiring becomes possible.

As illustrated inFIGS. 16A and 16B, the components are not arranged around the projection lens216A, therefore the flexibility of arrangement of the projection lens216A is high and a vertical shift mechanism of the projection lens216A can be easily mounted.

As illustrated inFIGS. 16A and 16B, the reflection type liquid crystal panels201A to203A are arranged facing downward. Accordingly, dust etc. floating in the housing of the projector200will not easily adhere to the panel surfaces of the reflection type liquid crystal panels201A to203A, the reduction in level of the polarized beam due to the adhesion of dust is small, and there is therefore little drop in the quality of the displayed image.

The focus optical system including the reflection type liquid crystal panels201A to203A is arranged compactly around the light combining prism210A, so the structural rigidity of the mechanical is easily improved. For this reason, there is little deviation of pixel position etc. among three reflection type liquid crystal panels201A to203A, and a high quality image is obtained.

The image projection apparatus of the present invention is not limited to the above examples. Various modifications equivalent or similar to the embodiments mentioned above can be employed.

For example, the projector200illustrated inFIGS. 16A and 16Bmay be vertically reversed in orientation with for example the light source500(red illumination light source251, green illumination light source252, blue illumination light source252) arranged at the top portion and the light combining prism210A etc. arranged at the bottom portion, and the light source500and the light combining prism210A etc. may be laterally arranged on the same plane.