Abstract:
An illuminating apparatus includes: a light source that emits a source light; and a light guiding module that has an overlap rod portion which can pass luminous fluxes traveling in different directions therethrough and has a returning member which returns the luminous fluxes having passed through the overlap rod portion at least once so that the luminous fluxes enter the overlap rod portion in directions different from the previous time, whereby the source light is made uniform.

Description:
BACKGROUND  
       [0001]     1. Technical Field  
         [0002]     The present invention relates to an illuminating apparatus which illuminates an optical modulating device such as a liquid crystal light valve, and a projector having the same therein.  
         [0003]     2. Related Art  
         [0004]     For a first projector, there is one which collects source light from a light source lamp, enters it into one end of a rod integrator through an opening that is disposed at the center of a reflecting mirror and obtains the luminous light of a single polarization component through a polarization separation device that is disposed at the other end (see JP-A-2003202523) In this case, in reciprocating the reflected light from the polarization separation device by the reflecting mirror, the polarization direction is changed by a wave plate disposed on an optical path, and thus the light is passed through the polarization separation device.  
         [0005]     For a second projector, there is one which collects source light emitted from a light source lamp, causes it to enter one end of a rod integrator and subjects the light emitted from the other end side to polarization conversion by a polarization conversion unit formed of a polarization beam splitter and other devices and thus obtains the luminous light having a uniform single polarization component (see  FIG. 14  in JP-A-2000-56266).  
         [0006]     For a third projector, there is one which is provided with a solid light source on the incident end face of a rod and disposed with a light valve on the output end face of the rod through a lens (JP-A-2003-262795). In this projector, the light from the solid light source is made uniform in the rod, and emitted from the output end face. The output end face directly illuminates the light valve.  
         [0007]     However, among the projectors above, in the first projector, a half of the components that first transmit through the polarization separation device are not made uniform sufficiently.  
         [0008]     In addition, in the second and third projectors, the rod integrator makes the luminous light uniform. Thus, the targeted uniform light cannot be achieved unless the rod integrator is made long, and the unit of an illuminating apparatus tends to be increased in size.  
       SUMMARY  
       [0009]     An advantage of some aspects of the invention is to provide a small-sized illuminating apparatus which can irradiate highly uniform luminous light, and a projector using the same.  
         [0010]     An illuminating apparatus according to an aspect of the invention includes: (a) a light source that emits a source light, and (b) a light guiding module that uniformize the source light, the light guiding module having an overlap rod portion and a returning member; and wherein  
         [0011]     the overlap rod portion can pass luminous fluxes traveling in different directions therethrough, and  
         [0012]     the returning member returns the luminous fluxes having passed through the overlap rod portion at least once so that the luminous fluxes enter the overlap rod portion in directions different from the previous time.  
         [0013]     In the illuminating apparatus, the returning member returns the luminous fluxes having passed through that overlap rod portion at least once so that the luminous fluxes enter the overlap rod portion in directions different from the previous time. Thus, the source light is allowed to pass through the overlap rod portion for multiple times while the generation of interference is prevented. Accordingly, the overlap rod portion can be used double or more, and the source light can be made uniform in a relatively small space. Therefore, a small-sized illuminating apparatus can be provided which makes the source light uniform in a small space.  
         [0014]     In addition, in the illuminating apparatus according to a specific aspect or viewpoint of the invention, the returning member includes a mirror that bends an optical path. In this case, the luminous fluxes having passed through the overlap rod portion can be folded and returned in a small space, and the size of the illuminating apparatus can be reduced easily.  
         [0015]     According to another aspect of the invention, the light guiding module has an extension rod part that is jointed to at least one end face not jointed to the returning member among a plurality of end faces disposed on the overlap rod portion. In this case, the targeted uniformity can be achieved not only by the overlap rod portion and the returning member but also by the extension rod part.  
         [0016]     According to another aspect of the invention, the overlap rod portion and the extension rod part are each formed of a solid transparent member, and are jointed to each other with an adhesive that has a refractive index lower than that of the overlap rod portion and the extension rod part. In this case, the jointing surfaces of the overlap rod portion to the extension rod part also serve as a total reflection surface which allows the luminous fluxes to propagate while they are reflected, the luminous fluxes travel in the direction orthogonal to the direction in which the extension rod part extends.  
         [0017]     According to another aspect of the invention, the returning member is formed of a solid transparent member, and is jointed to the overlap rod portion with an adhesive that has a refractive index lower than that of the overlap rod portion and the returning member. In this case, the jointing surfaces of the overlap rod portion to the returning member also serve as a total reflection surface which allows the luminous fluxes to propagate while they are reflected, the luminous fluxes travel In the direction orthogonal to the end face jointed to the returning member.  
         [0018]     According to another aspect of the invention, the overlap rod portion and the returning member perform wavefront splitting and superimposition of the luminous fluxes by internal reflection. In this case, the source light can be made uniform as it is passing through the overlap rod portion and the returning member.  
         [0019]     According to another aspect of the invention, the light source includes a solid light source, and the apparatus further includes a polarization conversion member that converts a source light from the light source to a polarized light in a particular direction. In this case, a simple, small-sized light source using a solid light source can be provided, and the source light from this light source can be converted into the linear polarized light by the polarization conversion member to give the luminous light.  
         [0020]     A projector according to an aspect of the invention includes: (a) a plurality of illuminating apparatuses described above for individual colors that generates a color light as a luminous light, (b) a plurality of optical modulating device for individual colors that modulates each of color lights from the illuminating apparatus for individual colors in accordance with image information, (c) a light combining optical system that combines and emits the light of an image in each color modulated by the optical modulating device for individual colors, and (d) a projection optical system that projects the light of the image combined through the light combining optical system.  
         [0021]     Since the projector uses the illuminating apparatus having the features above, a small-sized, inexpensive color projector, for example, can be provided by a small-sized illuminating apparatus for individual colors which can make the light uniform in a small space. In addition, the luminous light from the illuminating apparatus is allowed to directly enter the optical modulating device not through the lens and so on. In this case, the optical modulating device can be disposed close to the rod end face and so on that is the output end of the light guiding module, and thus efficient illumination can be achieved.  
         [0022]     A projector according to another aspect of the invention includes: (a) the illuminating apparatus described above, (b) an optical modulating device that modulates a luminous light from the illuminating apparatus in accordance with image information, and (c) a projection optical system that projects the light of an image formed by the light at the optical modulating device.  
         [0023]     Since the projector uses the illuminating apparatus having the features above, a small-sized, inexpensive projector can be provided by a small-sized illuminating apparatus which can make the light uniform in a small space. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]     The Invention will be described with reference to the accompanying drawing, wherein like numbers reference like elements.  
         [0025]      FIG. 1  shows a block diagram conceptually illustrating a projector according to a first embodiment.  
         [0026]      FIG. 2  shows a plan view depicting a blue light illuminating apparatus shown in  FIG. 1 .  
         [0027]      FIG. 3  shows a side view depicting the blue light illuminating apparatus shown in  FIG. 1 .  
         [0028]      FIG. 4  shows a diagram depicting a partially enlarged blue light illuminating apparatus shown in  FIG. 1  and the other drawings.  
         [0029]      FIG. 5  shows a diagram illustrating a unit of an illuminating apparatus of a projector according to a second embodiment.  
         [0030]      FIG. 6  shows a plan view depicting a unit of an illuminating apparatus of a projector according to a third embodiment.  
         [0031]      FIG. 7  shows a side view partially depicting a blue light illuminating apparatus shown in  FIG. 6 .  
         [0032]      FIG. 8  shows a diagram illustrating a projector according to the fourth embodiment. 
     
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS  
       [0033]     First Embodiment  
         [0034]      FIG. 1  shows a block diagram conceptually illustrating the structure of a projector according to a first embodiment, which has an illuminating apparatus according to an embodiment of the invention therein.  
         [0035]     A projector  10  has an illuminating section  20 , an optical modulating section  30 , a projection lens  40 , and a control unit  80 . Here, the illuminating section  20  has a blue light illuminating apparatus  21 , a green light illuminating apparatus  23 , a red light illuminating apparatus  25 , and a light source drive unit  27 . In addition, the optical modulating section  30  has three liquid crystal display panels  31   33  and  35  which are optical modulating devices, a cross dichroic prism  37  which is a light combining optical system, and a device drive unit  38  which outputs a drive signal to each of the liquid crystal display panels  31 ,  33  and  35 .  
         [0036]     In the illuminating section  20  described above, the blue light illuminating apparatus  21  has a pair of blue light source units  51   a  and  51   b,  a pair of polarization conversion units  61   a  and  61   b,  a pair of light guiding parts  71   a  and  71   b,  and an integrating rod part  78 . Here, each of the blue light source units  51   a  and  51   b  is a blue light source which emits blue source light. Each of the polarization conversion units  61   a  and  61   b  is a blue polarization conversion member which converts the blue source light to a particular polarization component. Each of the light guiding parts  71   a  and  71   b  and the integrating rod part  78  are a blue uniform optical system which makes the blue source light uniform.  
         [0037]      FIG. 2  shows a plan view depicting the blue light illuminating apparatus  21  shown in  FIG. 1 , and  FIG. 3  shows a side view depicting the blue light illuminating apparatus  21 .  
         [0038]     In the blue light illuminating apparatus  21 , the first blue light source unit  51   a  is formed in which a plurality of LEDs  22   f  which are light emitting devices called a solid light source or a semiconductor light source are mounted on a circuit board  22   g  in proper two dimensional arrangement (for example, in matrix arrangement), having a light gathering lens array  22   b  in which lens elements for shaping beams are separately disposed on the front side of each of the LEDs  22   f  that is a light source. Each of the LEDs  22   f  generates blue light included in blue (B) among three primary colors. The blue light taken out of the LED  22   f , that is, a first source light LB passes through the light gathering lens array  22   b , and enters the incident end of the first polarization conversion unit  61   a,  that is, an incident port IPa thereof. On this occasion, the blue light from each of the LEDs  22   f  is properly spread by each of the lens elements configuring the light gathering lens array  22   b  as well as it is shaped into an elliptic or rectangular beam in cross section that gathers at a predetermined position. More specifically, the blue light from each of the LEDs  22   f  is collected as a whole at the rectangular incident port IPa disposed on the first polarization conversion unit  61   a,  and all enters the incident port IPa as it is superimposed on each other.  
         [0039]     The second blue light source unit  51   b  has the same structure as that of the first blue light source unit  51   a , only different in the arrangement. Although the detailed description is omitted, in the second blue light source unit  51   b , the blue light from each of the LEDs  22   f  on the circuit board  22   g  is collected by the light gathering lens array  22   b , and all enters a rectangular incident port IPb disposed on the second polarization conversion unit  61   b  as it is superimposed on each other.  
         [0040]     The first polarization conversion unit  61   a  is disposed on the output side of the first blue light source unit  51   a  as it faces thereto, which aligns the polarization direction of the first source light LB entering from the incident port IPa. The first polarization conversion unit  61   a  is formed by bonding a right angled triangle prism to a parallelogram prism, having a polarization separation film  62   a  which is sandwiched between the two prisms, a reflective film  62   b  which is formed on the opposite side of the polarization separation film  62   a  as the parallelogram prism is sandwiched therebetween, and a wave plate  62   d  which is disposed on the light guiding part  71   a  side of the parallelogram prism.  
         [0041]     The polarization separation film  62   a  and the reflective film  62   b  are a polarization separation member that is formed of a dielectric multilayer formed on the slope of each of the prisms by vapor deposition, and arranged in the state in which they are tilted at an angle of 45 degrees with respect to a system optical axis SA. In the blue light that is the random polarized light from the first blue light source unit  51   a,  the former polarization separation film  62   a  transmits a linear polarized light component (for example, a polarized light P) in a particular direction, and reflects a linear polarized light component (for example, a polarized light S) in the direction orthogonal thereto. Consequently, it efficiently separates the two linear polarized light components orthogonal to each other. In addition, the latter reflective film  62   b  reflects one of the linear polarized light components reflected at the polarization separation film  62   a  (in the case above, the polarized light S), and bends the optical path. The reflective film  62   b  may be replaced by a mirror having a metal film deposited thereon. As described above, the first linear polarized light component having passed through the polarization separation film  62   a  (in the case above, the polarized light P) is emitted from an output port OP 1  disposed on the right angled triangle prism side. The second linear polarized light component having been reflected at the polarization separation film  62   a  and the reflective film  62   b  (in the case above, the polarized light S) is emitted from an output port OP 2  disposed on the parallelogram prism side. The wave plate  62   d  disposed as it faces the output port OP 2  is a phase device which is formed of a half wave plate. It converts the second linear polarized light component reflected at the reflective film  62   b  and emitted from the parallelogram prism in the direction of the system optical axis SA (in the case above, the polarized light S) to the first linear polarized light component orthogonal thereto (that is, the polarized light P). Consequently, the first polarization conversion unit  61   a  can efficiently convert the first source light LB which entered the incident port IPa only to the first linear polarized light (in this case, the polarized light P), and emit it out of two output ports OP 1  and OP 2 ′.  
         [0042]     The second polarization conversion unit  61   b  has the same structure as that of the first polarization conversion unit  61   a  only different in the arrangement, omitting the detailed description. The second polarization conversion unit  61   b  can efficiently convert the first source light LB which entered the incident port IPb only to the first linear polarized light(in this case, the polarized light P), and emit it on the second light guiding part  71   b  side.  
         [0043]     The first light guiding part  71   a  is a light guiding module which has a first rod part  72   a,  a second rod part  72   c,  a first prism part  72   e,  a second prism part  72   f,  and reflecting mirrors M 1 , M 2  and M 3 . Among them, the first rod part  72   a  is a solid prismatic rod integrator formed of glass, plastics and so on. It functions as an extension rod part. The first rod part  72   a  has an incident port IP 2  which faces the output ports OP 1  and OP 2 ′, of the first polarization conversion unit  61   a,  and the output side end face thereof is jointed to a first incident end face IF 1  of the second rod part  72   c.  The second rod part  72   c  is also a solid prismatic rod integrator which is formed of glass, plastics and so on having the same refractive index as that of the first rod part  72   a . It functions as an overlap rod portion. The second rod part  72   c  has a first output end face OF 1  on the opposite side of the first incident end face IF 1  jointed to the first rod part  72   a . The first output end face OF 1  is jointed to the incident side end face of the first prism part  72   e . The first prism part  72   e  configures a returning member along with the second prism part  72   f,  which has the role to cause the luminous fluxes emitted from the second rod part  72   c  to enter the second rod part  72   c  from the direction different from the previous time. The first and the second prism parts  72   e  and  72   f  are a solid member which is formed of glass, plastics and so on having the same refractive index as that of the first and the second rod parts  72   a  and  72   c . In addition, on the side surfaces on the outside of the first and the second prism parts  72   e  and  72   f,  the reflecting mirrors M 1 , M 2  and M 3  are formed which bend the traveling directions of the luminous fluxes propagating through inside these prisms, and these also configure a part of the returning member. The second prism part  72   f  has an output side end face which is adjacent to the surface to which the first prism part  72   e  is jointed, and which is orthogonal to the incident side end face of the first prism part  72   e . The output side end face is jointed to a second incident end face IF 2  of the second rod part  72   c.    
         [0044]     Some of the luminous fluxes which entered from the incident port IP 2  of the first rod part  72   a  travel straight, and some are totally reflected at the side surface in the inner surface. However, as a whole, it travels along the system optical axis SA in a direction AB, and enters the first incident end face IF 1  of the second rod part  72   c . Some of the luminous fluxes which entered from the first incident end face IF 1  of the second rod part  72   c  travel straight, or some are totally reflected at the side surface in the inner surface. However, as a whole, it travels along the system optical axis SA in the direction AB, and enters the first prism part  72   e  through the first output end face OF 1 . The optical paths of the luminous fluxes which entered the first prism part  72   e  are bent at an angle of 90 degrees by the reflecting mirror M 1  which bends the optical paths, and the luminous fluxes enter the second prism part  72   f . The optical path of the luminous fluxes which entered to the second prism part  72   f  are further bent at an angle of 90 degrees by the reflecting mirrors M 2  and M 3  which bend the optical path, and the luminous fluxes are outputted from the second prism part  72   f . The outputted light from the second prism part  72   f  enters the second incident end face IF 2  of the second rod part  72   c . Some of the luminous fluxes which entered from the second incident end face IF 2  of the second rod part  72   c  travel straight, or some are totally reflected at the side surface in the inner surface. However, as a whole, it travels along the system optical axis SA in a direction CD orthogonal to the direction AB, and enters the integrating rod part  78 , described later, through the second output end face OF 2 .  
         [0045]      FIG. 4  shows a diagram illustrating light propagation in the second rod part  72   c . Four side surfaces of the second rod part  72   c  are jointed to the rod parts  72   a  and  78  and the prism parts  72   e  and  72   f  therearound with an adhesive AD having a low refractive index. On this account, luminous fluxes L 00 , L 01  and L 02  enter from the first rod part  72   a  through the first incident end face IF 1 , and travel almost in parallel with the system optical axis SA. The luminous fluxes as a whole travel inside the second rod part  72   c  in the direction AB as they are totally reflected at the upper and lower side surfaces. In addition, luminous fluxes L 03 , L 04  and L 05  enter from the second prism part  72   f  through the second incident end face IF 2 , and travel almost in parallel with the system optical axis SA. The luminous fluxes as a whole travel inside the second rod part  72   c  in the direction CD although they are totally reflected at the right and left side surfaces. As described above, the luminous fluxes enter the second rod part  72   c  from the two directions, and thus the second rod part  72   c  can be utilized as the rod integrator twice. In addition, the first and the second prism parts  72   e  and  72   f  also make the luminous flux distribution uniform as one kind of the rod integrator. Therefore, the luminous fluxes that have passed through the second rod part  72   c  twice has an extremely high degree of uniformity with respect to the cross section direction vertical to the system optical axis SA.  
         [0046]     The second light guiding part  71   b  has the same structure as that of the first light guiding part  71   a  only different in the arrangement, omitting the detailed description. The second light guiding part  71   b  serves as a light guiding module which causes the first source light LB to enter the second rod part  72   c  from the second polarization conversion unit  61   b  through the first rod part  72   a,  and again causes it to enter the second rod part  72   c  through the prism parts  72   e  and  72   f . The first source light LB that has passed through the second rod part  72   c  twice is finally jointed to the integrating rod part  78 .  
         [0047]     The integrating rod part  78  is a solid prismatic rod integrator which is formed of glass, plastics and so on having the same refractive index as that of the first rod part  72   a  and so on. The integrating rod part  78  has an end face EF 4  close to the second rod part  72   c  disposed in the first and the second light guiding parts  71   a  and  71   b , which is jointed to the second rod part  72   c  through the end face EF 4 . The integrating rod part  78  is extended in the direction orthogonal to the first rod part  72   a  as the second rod part  72   c  is sandwiched, which allows the luminous fluxes having finally been outputted from the second rod part  72   c  to go out of an output port OP 4  as a first luminous light LB 2 . The integrating rod part  78  configures the light guiding module along with the first and the second light guiding parts  71   a  and  71   b , which functions as the extension rod part.  
         [0048]     The operation of light in the blue light illuminating apparatus  21  will be described. The first source light LB generated at the first blue light source unit  51   a  passes through the first polarization conversion unit  61   a  to be formed in the linear polarized light in a particular direction, and travels as it is totally reflected at the inner side surface of the first light guiding part  71   a . On this occasion, the first source light LB propagates through the first rod part  72   a  for one way, the second rod part  72   c  for one way twice, the prism parts  72   e  and  72   f  for one way, and the integrating rod part  78  for one way, while it is being made uniform, and it is outputted from the output port OP 4  as the linear polarized light. On the other hand, the first source light LB generated at the second blue light source unit  51   b  passes through the second polarization conversion unit  61   b  to be formed in the linear polarized light in a particular direction, and it travels as it is totally reflected at the inner side surface of the second light guiding part  71   b.  On this occasion, the first source light LB propagates through the first rod part  72   a  for one way, the second rod part  72   c  for one way twice, the prism parts  72   e  and  72   f  for one way, and the integrating rod part  78  for one way, while it is being made uniform, and it is outputted from the output port OP 4  as the linear polarized light. More specifically, the first source light LB generated at the first and the second blue light source units  51   a  and  51   b  is made uniform as it is converted to the linear polarized light, and is outputted from the output port OP 4  as the first luminous light LB 2  of highly uniform polarization.  
         [0049]     Returning to  FIG. 1 , the green light illuminating apparatus  23  has a pair of green light source units  53   a  and  53   b,  a pair of polarization conversion units  63   a  and  63   b,  a pair of light guiding parts  73   a  and  73   b,  and an integrating rod part  78 . Among them, the green light source units  53   a  and  53   b  have the structure as similar to that of the blue light source units  51   a  and  51   b.  However, each of LEDs incorporated therein generates green light included in green (G) among three primary colors. A second source light LG having the green light passes through a light gathering lens array, not shown, and all enters incident ports IPa and IPb of the polarization conversion units  63   a  and  63   b  as it is superimposed on each other. Each of the polarization conversion units  63   a  and  63   b  has the structure similar to that of the polarization conversion unit  61   a  shown in  FIG. 2 . The second source light LG having passed through the polarization conversion units  63   a  and  63   b  undergoes polarization separation, optical path bending, and polarization switching, and it is efficiently converted to the linear polarized light having a single component as similar to the case of the polarization conversion units  61   a  and  61   b . It is further guided into the light guiding parts  73   a  and  73   b  having the same structure as that of the light guiding parts  71   a  and  71   b  shown in  FIG. 2  and so on, and is joitned to the integrating rod part  78 . A second luminous light LG 2  having passed through the light guiding parts  73   a  and  73   b  and the integrating rod part  78  is made uniform with no loss by wavefront splitting and superimposition utilizing the reflection in the rod inner surface. It enters the green light liquid crystal display panel  33  through a first polarization filter  26   b  which is arranged oppositely to the output port OP 4  of the integrating rod part  78  in the optical modulating section  30 . Therefore, the area to be irradiated onto the liquid crystal display panel  33  is uniformly illuminated by the green linear polarized light.  
         [0050]     The red light illuminating apparatus  25  has a pair of red light source units  55   a  and  55   b,  a pair of polarization conversion units  65   a  and  65   b,  a pair of light guiding parts  75   a  and  75   b , and an integrating rod part  78 . Among them, the red light source units  55   a  and  55   b  have the structure similar to that of the blue light source units  51   a  and  51   b.  However, each of LEDs incorporated therein generates red light included in red (R) among three primary colors. A third source light LR having the red light passes through a light gathering lens array, not shown, and all enters incident ports IPa and IPb of the polarization conversion units  65   a  and  65   b  as it is superimposed on each other. Each of the polarization conversion units  65   a  and  65   b  has the structure similar to that of the polarization conversion unit  61   a  shown in  FIG. 2 . The third source light LR having passed through the polarization conversion units  65   a  and  65   b  undergoes polarization separation, optical path bending, and polarization switching, and is efficiently converted to the linear polarized light having a single component as similar to the case of the polarization conversion units  61   a  and  61   b . It is guided into the light guiding parts  75   a  and  75   b  having the same structure as that of the light guiding parts  71   a  and  71   b  shown in  FIG. 2  and so on, and is further coupled to the integrating rod part  78 . A third luminous light LR 2  having passed through the light guiding parts  75   a  and  75   b  and the integrating rod part  78  is made uniform with no loss by wavefront splitting and superimposition utilizing the reflection in the rod inner surface. It enters the red light liquid crystal display panel  35  through the first polarization filter  26   c  which is arranged oppositely to the output port OP 4  of the integrating rod part  78  in the optical modulating section  30 . Therefore, the area to be irradiated onto the liquid crystal display panel  35  is uniformly illuminated by the red linear polarized light.  
         [0051]     Each of the liquid crystal display panels  31 ,  33  and  35  is a light transmissive optical modulating device which switches the polarization direction of the luminous light in units of pixels in accordance with an image signal inputted from outside and thus two dimensionally modulates the luminous light of each color that comes from each units of the illuminating apparatus  21 ,  23  and  25  and enters each of the liquid crystal display panels  31 ,  33  and  35 . On the incident side of each of the liquid crystal display panels  31 ,  33  and  35 , the first polarization filters  26   a,    26   b  and  26   c  are arranged as they face the incident plane of the panels, and they can illuminate each of the liquid crystal display panels  31 ,  33  and  35  with the polarization component having an increased degree of polarization. In addition, on the output side of each of the liquid crystal display panels  31 ,  33  and  35 , the second polarization filters  36   a,    36   b  and  36   c  are arranged as they face the out going plane of the panels, and can transmit only the polarization component that has passed through each of the liquid crystal display panels  31 ,  33  and  35  in the direction orthogonal to a particular direction. Here, the first polarization filter  26   a,  the liquid crystal display panel  31 , and the second polarization filter  36   a  configure a blue liquid crystal light valve. The first polarization filter  26   b , the liquid crystal display panel  33 , and the second polarization filter  36   b  configure a green liquid crystal light valve. The first polarization filter  26   c , the liquid crystal display panel  35 , and the second polarization filter  36   c  configure a red liquid crystal light valve. More specifically, the luminous lights LB 2 , LG 2  and LR 2  come from each illuminating apparatus  21 ,  23  and  25 , and enter the liquid crystal display panels  31 ,  33  and  35 , respectively. They are two dimensionally modulated in the intensity by the liquid crystal display panels  31 ,  33  and  35 . The light of an image in each color having passed through each of the liquid crystal display panels  31 ,  33  and  35  is combined at the cross dichroic prism  37 , and emitted from one of the side surfaces thereof. The image of the combined light emitted from the cross dichroic prism  37  enters the projection lens  40  which is the projection optical system, and is projected onto a screen (not shown) at a proper magnification. More specifically, a color image that combines images of each color (blue, green, and red) formed on each of the liquid crystal display panels  31 ,  33  and  35  is projected onto the screen as video or a still image by the projector  10 .  
         [0052]     Second Embodiment  
         [0053]     Next, a second embodiment according to the invention will be described with reference to  FIG. 5 . The basic configuration of a projector according to the embodiment is the same as that of the first embodiment, but the configuration of the illuminating apparatus is partially different from the first embodiment.  
         [0054]     A blue light illuminating apparatus  121  shown in the drawing has a blue light source unit  51   a , a polarization conversion unit  61   a,  a light guiding part  171   a,  and an integrating rod part  78 . Among them, the light guiding part  171   a  has a first rod part  72   a,  a second rod part  72   c,  a third rod part  172   n,  a fourth rod part  172   m,  a pair of prism parts  172   e  and  172   f,  and reflecting mirrors M 1 , M 2  and M 3 .  
         [0055]     The third rod part  172   n  is jointed to a first output end face OF 1  of the second rod part  72   c,  and is a solid prismatic rod integrator which is formed of glass, plastics and so on having the same refractive index as that of the first rod part  72   a . The fourth rod part  172   m  is jointed to a second incident end face IF 2  of the second rod part  72   c  through the second prism part  172   f,  and is also a solid prismatic rod integrator which is formed of glass, plastics and so on having the same refractive index as that of the first rod part  72   a . The third rod part  172   n  is connected to the fourth rod part  172   m  through the first prism part  172   e . The two prism parts  172   e  and  172   f  are a solid member which is formed of glass, plastics and so on having the same refractive index as that of the first rod part  72   a . The rod parts  172   m  and  172   n  and the prism parts  172   e  and  172   f  configure a returning member along with the reflecting mirrors M 1 , M 2  and M 3 , and have a role to cause the luminous fluxes emitted from the second rod part  72   c  to enter the second rod part  72   c  from the direction different from the previous time. In this case, the returning member is made sufficiently long to achieve further uniform luminous fluxes.  
         [0056]     In addition, for the light source and the uniform optical system formed of the blue light source unit  51   a , the polarization conversion unit  61   a  and the light guiding part  171   a  described above, another light source and another uniform optical system having the same function as that of them may be further provided, and the luminous fluxes from the light source and the uniform optical systems  51   a ,  61   a  and  171   a  may be coupled at the integrating rod part  78  as similar to the case shown in  FIG. 2 .  
         [0057]     The blue light illuminating apparatus  121  is described above. The green light illuminating apparatus  23  and the red light illuminating apparatus  25  shown in  FIG. 1  may have the structure similar to that of the blue light illuminating apparatus  121  shown in  FIG. 5 .  
         [0058]     Third Embodiment  
         [0059]     Next, a third embodiment according to the invention will be described. The basic configuration of a projector according to the embodiment is the same as that of the first embodiment, but the configuration of the illuminating apparatus is partially different from the first embodiment.  FIG. 6  shows a front view partially depicting an illuminating apparatus, and  FIG. 7  shows a side view partially depicting the illuminating apparatus.  
         [0060]     In a blue light illuminating apparatus shown in the drawing, a light guiding part  271   a  has a first rod part  72   a,  a second rod part  72   c,  four prism parts  272   e,    272   f,    272   g  and  272   h,  and six reflecting mirrors M 01 , M 02 , M 03 , M 04 , M 05  and M 06 .  
         [0061]     The first prism part  272   e  is jointed to the first output end face OFI of the second rod part  72   c . The second prism part  272   f  is jointed to the first prism part  272   e  and a second incident end face IF 2  of the second rod part  72   c . The third prism part  272   g  is jointed to a second output end face OF 2  of the second rod part  72   c . The fourth prism part  272   h  is jointed to the third prism part  272   g  and a third incident end face IF 3  of the second rod part  72   c . Each of the prisms parts  272   e  to  272   h  is formed of glass, plastics and so on having the same refractive index as that of the second rod part  72   c . Each of the prisms parts  272   e  to  272   h  configures a returning member along with the reflecting mirrors M 1  to M 6  formed outside thereof, which has a role to again cause the luminous fluxes emitted from the second rod part  72   c  to enter the second rod part  72   c  twice from two directions different from the previous time.  
         [0062]     A first source light LB from the first rod part  72   a  passes through the second rod part  72   c  in the direction AB through the first incident end face IF 1  and the first output end face OF 1 , and again enters the second rod part  72   c  from the second incident end face IF 2  through the first and the second prism parts  272   e  and  272   f . The luminous fluxes having again entered the second rod part  72   c  propagate through the second rod part  72   c  in a direction EF. It is emitted from the second output end face OF 2 , and again enters the second rod part  72   c  from the third incident end face IF 3  through the third and the fourth prism parts  272   g  and  272   h.  The luminous fluxes having again entered the second rod part  72   c  propagate through the second rod part  72   c  in the direction CD. It is emitted from the third output end face OF 3 , and enters the integrating rod part  78  through an end face EF 4 . When the light guiding part  271   a  described above is used, the number of times that the light passes through the second rod part  72   c  is increased, the returning member is made long sufficiently, and the luminous fluxes are made more uniform.  
         [0063]     As described above, the blue light illuminating apparatus  121  is described. The green light illuminating apparatus  23  and the red light illuminating apparatus  25  shown in  FIG. 1  may as well have the structure similar to that of the blue light illuminating apparatus  21  having the light guiding part  271   a  shown in  FIGS. 6 and 7 .  
         [0064]     Fourth Embodiment  
         [0065]     Next, a fourth embodiment will be described with reference to  FIG. 8 . A projector according to the embodiment is a so-called single panel projector in which the illuminating section  20 , the optical modulating section  30  and the other units according to the first embodiment are properly modified in the projector  10  shown in  FIG. 1 .  
         [0066]     A projector  310  has an illuminating section  320 , an optical modulating section  330 , and a projection lens  40 . Here, the illuminating section  320  has an illuminating apparatus  321  which generates nearly white source light, and a light source drive unit  27 . In addition, the optical modulating section  330  has a liquid crystal display panel  331  which is an optical modulating device, and a device drive unit  38  which outputs a drive signal to the liquid crystal display panel  331 .  
         [0067]     The illuminating apparatus  321  has a pair of white light source units  351   a  and  351   b , a pair of polarization conversion units  61   a  and  61   b , a pair of light guiding parts  71   a  and  71   b , and an integrating rod part  78 . Here, the white light source units  351   a  and  351   b  are a light source which emits a white source light LW. Each of the polarization conversion units  61   a  and  61   b  is a polarization conversion member which converts the source light LW to a particular polarization component. The light guiding parts  71   a  and  71   b  and the integrating rod part  78  are a uniform optical system which makes the source light LW uniform.  
         [0068]     The white light source units  351   a  and  351   b  have the structure similar to that of the blue light source unit  51   a  shown in  FIG. 2 , except the specifications of wavelengths. Although the detailed description is omitted, in each of the white light source units  351   a  and  351   b , each white light from LEDs is collected by a light gathering lens array, and all enters incident ports IPa and IPb disposed on each of the polarization conversion units  61   a  and  61   b  as it is superimposed on each other. The polarization conversion units  61   a  and  61   b  and the light guiding parts  71   a  and  71   b  are the same as those shown in  FIGS. 1, 2 , and so on, omitting the description.  
         [0069]     The illuminating apparatus  321  shown in the drawing makes the source light LW uniform that is generated at the white light source units  351   a  and  351   b  while the light is being converted to the linear polarized light. The light is emitted as highly uniform polarized light, and illuminates the area to be irradiated onto the liquid crystal display panel  331 . The light of an image having passed through the liquid crystal display panel  331  is incident to the projection lens  40  which is a projection optical system, and is projected on a screen (not shown) at a proper magnification. More specifically, an image formed on the liquid crystal display panel  331  is projected as video or a still image on the screen by the projector  31 O.  
         [0070]     In addition, for the liquid crystal display panel  331 , both of color and monochrome liquid crystal panels can be used.  
         [0071]     The invention has been described in accordance with the embodiments above, but the invention is not limited to the embodiments. For example, in the embodiments, the liquid crystal display panels  31 ,  33  and  35  are used for optical modulation, but a micro mirror device may be used for optical modulation instead of the liquid crystal display panels  31 ,  33  and  35 .  
         [0072]     In addition, the polarization conversion units  61   a,    61   b ,  63   a ,  63   b,    65   a , and  65   b  are not limited to those taken as an example. As long as the linear polarized light can be obtained from the random polarized light and so on, polarization conversion modules in various structures may be used.  
         [0073]     In addition, the form and size of the second rod part  72   c  which is incorporated in the light guiding parts  71   a  and  71   b  and the others are not limited to those shown in the drawings, which can be freely modified in accordance with the form and so on of the area to be irradiated onto the liquid crystal display panels  31 ,  33  and  35 . In addition, the path and direction to pass the luminous fluxes through the second rod part  72   c  for multiple times are also not limited to those shown in the drawings, which can be freely modified in accordance with purposes for use and so on.  
         [0074]     The first rod part  72   a,  the integrating rod part  78 , and the prism parts  72   e  and  72   f  and the others can be replaced by a hollow member which reflects the luminous fluxes in its inner surface.  
         [0075]     In addition, in the first embodiment, the illuminating section  20  is not limited to the blue light illuminating apparatus  21 , the green light illuminating apparatus  23  and the red light illuminating apparatus  25 , which may be an illuminating apparatus having color more than one using the other wavelengths. In the illuminating apparatus for individual colors, a unit is used which is adapted to the wavelength for use as it corresponds to each of the color light source units  51   a  and  51   b ,  53   a ,  53   b ,  55   a ,  55   b  and so on, and thus a desired luminous light can be obtained.  
         [0076]     The entire disclosure of Japanese Patent Application No. 2005-194642 filed Jul. 4, 2005 is expressly incorporated by reference herein.