Abstract:
A lighting device is provided which efficiently achieves a high brightness and a high image quality by using a solid light source which has long service life and does not need mercury. The lighting device includes a first light source section, a second light source section, a second rod integrator for combining lights emitted from the first and second light source sections, and a first rod integrator for guiding the light from the first light source section, to the second rod integrator. On an incident surface of the second rod integrator, a first region on which the light emitted from the first light source section is incident and a second region on which the light emitted from the second light source section is incident do not overlap each other, and the surface area of the first region and the surface area of the second region are different from each other.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The disclosure of Japanese Patent Application No. 2010-071996, filed on Mar. 26, 2010, is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to lighting devices that efficiently combine a plurality of light sources and that combine lights from different types of light sources, thereby allowing an image quality to be improved. Further, the present invention relates to projection type image display apparatuses using the lighting devices. 
         [0004]    2. Description of the Background Art 
         [0005]    In recent years, LEDs have been used as light sources for generic illumination, since they have long service life and high light-emission efficacy. The use of LEDs as light sources for projection type image display apparatuses is under consideration, since, for example, LEDs have long service life, do not include mercury, and do not rupture. However, LEDs have a broad light-emitting surface area and poor light-converging efficiency, and therefore, as light sources for projection type image display apparatuses in which light must be converged on an image display element that is a small-scale unit, at present, LEDs have not been used for projection type image display apparatuses other than ultra-compact apparatuses which cause no problems even when output of light is low. 
         [0006]    Therefore, methods for increasing output of light, such as by using and combining a plurality of LED light sources, or combining LED light sources and another light sources, have been proposed. For example, as shown in  FIG. 13 , in Japanese Laid-Open Patent Publication No. 2006-39338, a large number of LEDs  1311  are arranged and optically combined, thereby improving light output. 
         [0007]    Further, as shown in  FIG. 14 , in Japanese Laid-Open Patent Publication No. 2009-259583, a fluorescent material  1411  that allows green light to pass therethrough and that wavelength-converts blue light into green light, is disposed on an optical path for a green LED. As an excitation source for the fluorescent material, a laser beam is used. Since a laser element allows light to be converged on a small surface area even when output is increased, a point light source having high output can be formed. As a result, green light brightness is increased, and improvement of light output of an output image is achieved. 
         [0008]    Here, etendue is used as a definition of light which allows for optical handling. When it is assumed that there are no limitations on optical parts in a projection type image display apparatus, among light emitted from a light source, light for the same etendue as the etendue of a liquid crystal panel or DMD used as an image display element, can be handled. The etendue is defined as follows: 
         [0000]      etendue=π× A ×(sin θ) 2   (1),
 
         [0000]    wherein
       A denotes the surface area of a portion at which light is handled, and   θ denotes a converging angle relative to the portion A, or a light-emitting angle.       
 
       SUMMARY OF THE INVENTION 
       [0011]    In the invention described in Japanese Laid-Open Patent Publication No. 2006-39338, regarding the etendue of a light source, the sum of the surface areas of the LED light-emitting parts (emitters) is considered as a light source surface area A. Thus, even though the amount of light is increased by providing a large number of LEDs, the etendue also increases in proportion to the increased amount of light. Therefore, for introducing light emitted from such a light source, an image display apparatus having a high etendue, namely, an image display apparatus that can handle light incident on a large surface area or at a high angle, is required. This results in an increase in the size and cost of the image display apparatus, and the image display apparatus becomes very expensive. 
         [0012]    In the invention described in Japanese Laid-Open Patent Publication No. 2009-259583, as shown in  FIG. 14 , red light, blue light, and green light all pass through a converging lens located at an upper right position in  FIG. 14 , and enters an image display apparatus. Thus, the etendue depends at least on LEDs used for red light, blue light, and green light, respectively. Meanwhile, there is the fluorescent material  1411  on the optical path of green light, and the fluorescent material  1411  is excited by a blue laser beam to emit green light. Further, the light-emission efficacy of the fluorescent material  1411  is low only with the green light emitted from the LED, and thus most part of the green light emitted from the fluorescent material  1411  is fluorescent light generated by the excitation caused by the blue laser beam. However, the green fluorescent light has spectral characteristics in which a spectral distribution extends over a wide wavelength range as compared to that of the green LED light. Specifically, the peak wavelength of the spectral distribution is located to the long wavelength side of the peak wavelength of ideal green light, and the spectral distribution includes wavelengths of blue light. As a result, the color purity of green color is decreased, and it is difficult to obtain a high-quality video image. 
         [0013]    Therefore, an object of the present invention is to provide: a lighting device that efficiently achieves a high brightness and a high image quality by using a solid light source that has long service life and does not need mercury; and a projection type image display apparatus using the lighting source. 
         [0014]    A lighting device according to the present invention includes a first light source section, a second light source section, and a light combining section for combining light emitted from the first light source section and light emitted from the second light source section. On an incident surface of the light combining section, a first region on which the light emitted from the first light source section is incident and a second region on which the light emitted from the second light source section is incident do not overlap each other, and the surface area of the first region and the surface area of the second region are different from each other. 
         [0015]    Further, a projection type image display apparatus according to the present invention includes: the above lighting device; an image display element on which light emitted from the lighting device is incident and that modulates the incident light in accordance with a video signal; and a projection lens for projecting onto a screen the light modulated by the image display element. 
         [0016]    According to the present invention, a lighting device can be achieved which can most efficiently obtain a high brightness and a high image quality by using a solid light source that has long service life and does not need mercury. In addition, a projection type image display apparatus using the lighting device can be provided. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a configuration diagram of a lighting device according to a first embodiment; 
           [0018]      FIG. 2  is a schematic diagram for explaining a rotation plate of the lighting device shown in  FIG. 1 ; 
           [0019]      FIG. 3A  is a graph diagram showing spectral characteristics of fluorescent light; 
           [0020]      FIG. 3B  is a graph diagram showing spectral characteristics of LED light; 
           [0021]      FIG. 4  is a configuration diagram of a lighting device according to a second embodiment; 
           [0022]      FIG. 5  is a configuration diagram of a lighting device according to a third embodiment; 
           [0023]      FIG. 6  is a schematic diagram for explaining a diffusion plate of the lighting device shown in  FIG. 5 ; 
           [0024]      FIG. 7  is a configuration diagram of a lighting device according to a fourth embodiment; 
           [0025]      FIG. 8  is a configuration diagram of a lighting device according to a fifth embodiment; 
           [0026]      FIG. 9  is a configuration diagram of a lighting device according to a sixth embodiment; 
           [0027]      FIG. 10  is a configuration diagram of a lighting device according to a seventh embodiment; 
           [0028]      FIG. 11  is a configuration diagram of a lighting device according to an eighth embodiment; 
           [0029]      FIG. 12  is a configuration diagram of a projection type image display apparatus according to a ninth embodiment; 
           [0030]      FIG. 13  is a configuration diagram of a lighting device according to a conventional example; and 
           [0031]      FIG. 14  is a configuration diagram of a lighting device according to a conventional example. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
       [0032]      FIG. 1  is a configuration diagram of a lighting device according to a first embodiment. 
         [0033]    The lighting device  1  combines lights emitted from a plurality of light sources and performs uniform illumination with a high brightness. The lighting device  1  includes a first light source section  100 , a second light source section  122 , a first rod integrator  114 , and a second rod integrator  119 . 
         [0034]    The first light source section  100  includes a laser element  101  emitting blue light, an LED  102  emitting green light, an LED  103  emitting blue light, collimator lenses  104 ,  106 , and  116 , red reflection dichroic mirrors  105  and  111 , a blue reflection dichroic mirror  112 , a rotation plate  141 , a motor  110  rotating the rotation plate  141 , and a converging lens  113 . The rotation plate  141  includes: a disc-shaped base plate  108  formed from glass; a blue transmission dichroic mirror coat  107  applied to one surface of the base plate  108  (a surface thereof on the side opposite to the second rod integrator  119 ); and a fluorescent material  109  that is provided on the blue transmission dichroic mirror coat  107  and that has fluorescence to emit red light upon receiving blue excitation light. 
         [0035]    The blue light emitted from the laser element  101  is converted into a very thin parallel light beam by the collimator lens  104  and passes through the red reflection dichroic mirror  105  and the collimator lens  106 . The passed blue laser beam is applied to the fluorescent material  109  of the rotation plate  141 . Thus, the fluorescent material  109  is excited to emit red fluorescent light. The rotation plate  141  is rotated by the motor  110  provided at the center thereof. The red fluorescent light emitted from the fluorescent material  109  (including light reflected by the blue transmission dichroic mirror coat  107  on the back surface of the fluorescent material  109 ) is emitted at a high divergence angle. The collimator lens  106  is designed such that a focal point thereof is located on the surface of the fluorescent material  109 , and thus the red fluorescent light is converted into substantially parallel light by passing through the collimator lens  106 . The red fluorescent light having been converted into the parallel light is reflected by the red reflection dichroic mirrors  105  and  111 , and then passes through the blue reflection dichroic mirror  112 . The passed red fluorescent light is converged on an incident surface  115  of the first rod integrator  114  by the converging lens  113 . In addition, the green light emitted from the LED  102  is converted into substantially parallel light by the collimator lens  116  of which a focal point is located on a light-emitting surface of the LED  102 . The green light having been converted into the parallel light passes through the red reflection dichroic mirror  111 , and then passes through the blue reflection dichroic mirror  112 , similarly to the red light. The passed green light is converged on the incident surface  115  of the first rod integrator  114  by the converging lens  113 . Moreover, the blue light emitted from the LED  103  is converted into substantially parallel light by the collimator lens  117  of which a focal point is located on a light-emitting surface of the LED  103 . The blue light having been converted into the parallel light is reflected by the blue reflection dichroic mirror  112 , and then converged on the incident surface  115  of the first rod integrator  114  by the converging lens  113 . 
         [0036]    The second light source section  122  includes a laser element  123  emitting blue light, collimator lenses  124 ,  126 , and  136 , a blue transmission dichroic mirror  125 , a blue reflection dichroic mirror  134 , total reflection minors  133  and  137 , a rotation plate  142 , a motor  132  rotating the rotation plate  142 , and a converging lens  135 . The rotation plate  142  includes a base plate  128 ; a blue transmission dichroic mirror coat  127  applied to one surface of the base plate  128  (a surface thereof on the side opposite to the second rod integrator  119 ); a fluorescent material  129  that has fluorescence to emit red light upon receiving blue excitation light; a fluorescent material  130  that is excited to emit green light when being irradiated with a blue laser beam; and a light-transmitting part  131  having a light-diffusing function. 
         [0037]      FIG. 2  is a schematic diagram for explaining the rotation plate of the lighting device shown in  FIG. 1 . 
         [0038]    The fluorescent material  129 , the fluorescent material  130 , and the light-transmitting part  131  are provided on circumferentially equally divided portions, respectively, of the blue transmission dichroic mirror coat  127  of the rotation plate  142 . 
         [0039]    Referring back to  FIG. 1 , the blue laser beam emitted from the laser element  123  is converted into a very thin parallel light beam by the collimator lens  124  and passes through the blue transmission dichroic mirror  125  and the collimator lens  126 , and then enters the rotation plate  142 . The rotation plate  142  is rotated by the motor  132  provided at the center thereof. Thus, the fluorescent material  129 , the fluorescent material  130 , and the light-transmitting part  131  are repeatedly irradiated in order with the blue laser beam. When the fluorescent material  129  is irradiated with the blue laser beam, red fluorescent light is emitted. The red fluorescent light (including light reflected by the blue transmission dichroic mirror coat  127 ) is emitted at a high divergence angle. The collimator lens  126  is designed such that a focal point thereof is located on the surface of the fluorescent material  129  or  130 , and thus the red fluorescent light is converted into substantially parallel light by passing through the collimator lens  126 . The red fluorescent light having been converted into the parallel light is reflected in order by the blue transmission dichroic mirror  125  and the total reflection mirror  133 , and then passes through the blue reflection dichroic mirror  134 . The passed red fluorescent light is converged on an incident surface  120  of the second rod integrator  119  by the converging lens  135 . In addition, when the fluorescent material  130  is irradiated with the blue laser beam, green fluorescent light is emitted. The green fluorescent light (including light reflected by the blue transmission dichroic mirror coat  127 ) is emitted at a high divergence angle. The green fluorescent light is converted into parallel light by the collimator lens  126 . The green light having been converted into the parallel light is reflected in order by the blue transmission dichroic mirror  125  and the total reflection mirror  133 , and then passes through the blue reflection dichroic mirror  134 . The passed green fluorescent light is converged on the incident surface  120  of the second rod integrator  119  by the converging lens  135 . Moreover, when the blue laser beam passes through the light-transmitting part  131 , the blue laser beam is diffused. The collimator lens  136  is designed such that a focal point thereof is located on the surface of the light-transmitting part  131 , and thus the diffused blue light is converted into substantially parallel light by passing through the collimator lens  136 . The blue light having been converted into the parallel light is reflected in order by the total reflection mirror  137  and the blue reflection dichroic mirror  134 , and then converged on the incident surface  120  of the second rod integrator  119  by the converging lens  135 . Note that by causing a timing of the first light source section  100  emitting each of red light, green light, and blue light to coincide with a timing of the second light source section  122  emitting each of red light, green light, and blue light, it is also possible to sequentially emit light of each color from the second rod integrator  119 . 
         [0040]    The first rod integrator  114  guides light emitted from the first light source section  100 , to the second rod integrator  119 . The light emitted from the first light source section  100  is incident on the incident surface  115  of the first rod integrator  114 , and then propagated in the first rod integrator  114  while being repeatedly totally reflected inside the first rod integrator  114 . The first rod integrator  114  is a rectangular-columnar optical element that is formed from glass, and the incident surface  115  and an exit surface  118  thereof are inclined relative to its central axis, longitudinally. 
         [0041]    The second rod integrator  119  is a rectangular-columnar optical element that is formed from glass, and combines the light emitted from the first light source section  100  and light emitted from the second light source section  122 . Specifically, the exit surface  118  of the first rod integrator  114  is in contact with a part of the incident surface  120  of the second rod integrator  119  or may face the part of the incident surface  120  of the second rod integrator  119  at a very short interval. The light from the first light source section  100  is incident on a first region R 1 , of the incident surface  120  of the second rod integrator  119 , which is in contact with the exit surface  118  of the first rod integrator  114 . Meanwhile, the light from the second light source section  122  is directly incident on a second region R 2  that is a part of the incident surface  120  of the second rod integrator  119  excluding the first region R 1 . The first region R 1  and the second region R 2  do not overlap each other, and have different surface areas. Light incident on the incident surface  120  in an oblique direction is repeatedly totally reflected inside the second rod integrator  119 . Lights having various incident angles are propagated while being repeatedly totally reflected, whereby the lights are combined, and light having a uniform intensity distribution is emitted from an exit surface  121  of the second rod integrator  119 . 
         [0042]    Since the exit surface  118  is inclined relative to the central axis of the first rod integrator  114  as described above, when the exit surface  118  is in contact with the incident surface  120 , the central axis of the first rod integrator  114  is inclined relative to the incident surface  120  of the second rod integrator  119 . By so doing, the incident surface  115  and the exit surface  118  are located at positions that are different in the vertical direction in  FIG. 1  from each other. Thus, a space is formed to the second light source section  122  side of the first region R 1  and the second region R 2 . Here, light that passes through substantially the center of the incident surface  115  of the first rod integrator  114  and that is perpendicularly incident on the incident surface  115  is perpendicularly emitted from the exit surface  118 . Then, by converging the light emitted from the second light source section  122  within this space and causing the converged light to be incident on the second region R 2 , an optical system can be disposed such that: the first light source section  100  and the second light source section  122  do not interfere with each other; and an optical path of the light emitted from the first light source section  100  and an optical path of the light emitted from the second light source section  122  do not interfere with each other. 
         [0043]    In order to obtain high output with an LED, a light-emitting surface area needs to be large. Meanwhile, when a fluorescent material is excited by a laser beam, high output can be obtained while a light-emitting part is reduced in size, by converging the laser beam on a small spot. Thus, as understood from the above equation (1), in the second light source section  122 , the etendue can be decreased by converging the laser beam to reduce a light-emitting surface area. In other words, where E 1  denotes the etendue of the first light source section  100  and E 2  denotes the etendue of the second light source  122 , a relationship of E 1 &gt;E 2  is satisfied. 
         [0044]    As an incident angle of a light beam incident on the second rod integrator  119  increases, an emission angle of the light beam emitted from the exit surface  121  increases. Thus, as a converging angle of light incident on the incident surface  120  of the second rod integrator  119  increases, a region irradiated by the second rod integrator  119  increases in size. Therefore, when a plurality of light source sections is used, if a converging angle of each light source section is different from those of the others, a region irradiated with light from each light source section does not agree with those from the others, and the center of an illuminated region and the surrounding of the center are different in brightness from each other. For that reason, in the present embodiment, a converging angle θ 1  of the first light source section  100  is substantially equalized with a converging angle θ 2  of the second light source section  122 , whereby the light intensity and the spectral characteristics on the illuminated region can be uniformed. 
         [0045]    Where: A 1  denotes the size of a light source image formed on the incident surface  120  of the second rod integrator  119  by the light emitted from the first light source section  100 ; and A 2  denotes the size of a light source image formed on the incident surface  120  of the second rod integrator  119  by the light emitted from the second light source section  122 , when E 1 &gt; E 2 , a relationship of A 1 &gt;A 2  is satisfied due to the relationship of the above equation (1). Thus, in the present embodiment, in order to efficiently introduce both of the light source images into the second rod integrator  119  and to effectively use the lights from the first light source section  100  and the second light source section  122 , the surface area S 1  of the first region R 1  is set so as to be larger than the surface area (S 2 −S 1 ) of the second region R 2 . Here, S 1  corresponds to the first region R 1 , S 2  corresponds to the area of the incident surface  120  of the second rod integrator  119 , and S 2 −S 1  corresponds to the second region R 2 . As a result, a wasteful space is eliminated from the incident surface  120  of the second rod integrator  119  and the second rod integrator  119  is made compact, while output of light with a high brightness is enabled. 
         [0046]    Further, more preferably, as shown in the following equation (2), the surface area S 1  of the first region R 1  and the surface area (S 2 −S 1 ) of the second region R 2  are substantially proportional to the etendues of the first and second light source sections  100  and  122 , respectively. By this, the lights from the first and second light source sections  100  and  122  are more effectively used. 
         [0000]        S 1 /E 1≈( S 2 −S 1)/ E 2  (2)
 
         [0047]    Moreover, preferably, the image of the first light source section  100  and the first region R 1  are similar in shape to each other, and the image of the second light source section  122  and the second region R 2  are similar in shape to each other. By this, the lights from the first light source section  100  and the second light source section  122  can be more efficiently introduced. 
         [0048]      FIG. 3A  is a graph diagram showing spectral characteristics of fluorescent light, and  FIG. 3B  is a graph diagram showing spectral characteristics of LED light. 
         [0049]    When  FIG. 3A  and  FIG. 3B  are compared to each other, the wavelength width of each of red fluorescent light, green fluorescent light, and blue fluorescent light are large as compared to that of LED light, and each fluorescent light has a low color purity. Meanwhile, when LEDs are used as light sources of a lighting device, the light output of a green LED is insufficient, and the light output and the spectral characteristics of a red LED greatly change depending on the junction temperature. In contrast, in the present embodiment, each of the first light source section  100  and the second light source section  122  stabilizes its light output by using red fluorescent light. In addition, in the first light source section  100 , the LED is used for green light, thereby compensating for the green fluorescent light in the second light source section  122 , which has a low color purity. 
         [0050]    Further, a blue laser beam does not have high wavelengths and has a deep color, and thus it has poor visibility. In contrast, in the present embodiment, the blue LED is used in the first light source section  100 , thereby reproducing blue color having good visibility. 
         [0051]    In the lighting device  1 , when high output is required, both the first light source  100  and the second light source  122  are used. However, when the lighting device  1  is used in an energy-saving mode, it is desirable to use only the first light source  100  that has excellent color reproducibility. 
         [0052]    In the first embodiment, setting is made so as to satisfy E 1 &gt;E 2 . However, when an LED having high output with a small light-emitting part can be used in the first light source section  100 , E 1 &gt;E 2  is satisfied, and thus it suffices that the surface area S 1  of the first region R 1  is set so as to be smaller than the surface area (S 2 −S 1 ) of the second region R 2 . 
       Second Embodiment 
       [0053]      FIG. 4  is a configuration diagram of a lighting device according to a second embodiment. 
         [0054]    The lighting device  2  according to the second embodiment is different from the lighting device  1  according to the first embodiment in the configurations of the light source sections. 
         [0055]    A first light source section  200  is the same as the second light source section  122  of the first embodiment, but light converged by the converging lens  135  is converged on an incident surface  202  of a first rod integrator  201 . 
         [0056]    A second light source section  207  includes an LED  208  emitting green light, an LED  213  emitting blue light, an LED  215  emitting red light, collimator lenses  209 ,  214 , and  216 , a blue reflection dichroic mirror  210 , a red reflection dichroic mirror  211 , and a converging lens  212 . 
         [0057]    The green light emitted from the LED  208  is converted into substantially parallel light by the collimator lens  209  of which a focal point is located on a light-emitting surface of the LED  208 . The green light having been converted into the parallel light passes in order through the blue reflection dichroic mirror  210  and the red reflection dichroic mirror  211 , and then is converged on an incident surface  205  of a second rod integrator  204  by the converging lens  212 . The blue light emitted from the LED  213  is converted into substantially parallel light by the collimator lens  214  of which a focal point is located on a light-emitting surface of the LED  213 . The blue light having been converted into the parallel light is reflected by the blue reflection dichroic mirror  210 , and then passes through the red reflection dichroic mirror  211 . The passed blue light is converged on the incident surface  205  of the second rod integrator  204  by the converging lens  212 . The red light emitted from the LED  215  is converted into substantially parallel light by the collimator lens  216  of which a focal point is located on a light-emitting surface of the LED  215 . The red light having been converted into the parallel light is reflected by the red reflection dichroic mirror  211 , and then converged on the incident surface  205  of the second rod integrator  204  by the converging lens  212 . 
         [0058]    Since the first light source section  200  employs the laser element, the etendue E 1  of the first light source section  200  is lower than the etendue E 2  of the second light source section  207 . In addition, a converging angle θ 1  of light emitted from the first light source section  200 , and a converging angle θ 2  of light emitted from the second light source section  207 , are set so as to be substantially equal to each other. Thus, in the second embodiment, the surface area S 1  of the first region R 1  is smaller than the surface area (S 2 −S 1 ) of the second region R 2 . 
       Third Embodiment 
       [0059]      FIG. 5  is a configuration diagram of a lighting device according to a third embodiment. 
         [0060]    The lighting device  3  according to the third embodiment includes a pair of first rod integrators  301  and  317 , a second rod integrator  304 , a pair of first light source sections  300  and  316 , and a second light source section  307 . 
         [0061]    Each of the first rod integrators  301  and  317  is the same as the first rod integrator  114  of the first embodiment. The first rod integrators  301  and  317  are disposed such that central axes thereof are inclined relative to an incident surface  319  of the second rod integrator  304 , and so as to spread apart with increasing distance from the incident surface  319 . Thus, a space is formed to the second light source section  307  side of first regions R 1  and R 1 ′ and a second region R 2 . By converging light emitted from the second light source section  307  within this space, an optical system can be disposed such that: the first light source section  300 , the second light source section  307 , and the first light source section  316  do not interfere with each other; and an optical path of light emitted from the first light source section  300 , an optical path of the light emitted from the second light source section  307 , and an optical path of light emitted from the first light source section  316  do not interfere with each other. 
         [0062]    Similarly to the second light source section  207  of the second embodiment, the first light source section  300  includes an LED  325  emitting green light, an LED  326  emitting blue light, and an LED  327  emitting red light. The light of the color emitted from each of the LEDs  325 ,  326 , and  327  is converged on an incident surface  302  of the first rod integrator  301  by a converging lens  364 . Similarly to the second light source section  207  of the second embodiment, the first light source section  316  also includes an LED  365  emitting green light, an LED  366  emitting blue light, and an LED  367  emitting red light. The light of the color emitted from each of the LEDs  365 ,  366 , and  367  is converged on the incident surface  318  of the first rod integrator  317  by a converging lens  368 . 
         [0063]    The second light source section  307  includes a laser element  308  emitting green light, collimator lenses  309  and  314 , a diffusion plate  310 , an aperture  313 , and a converging lens  315 . 
         [0064]      FIG. 6  is a schematic diagram for explaining the diffusion plate of the lighting device shown in  FIG. 5 . 
         [0065]    The diffusion plate  310  includes a base material  311  and beads  312  that are included in the base material  311  and that have a refractive index different from that of the base material  311 . 
         [0066]    An optical path of a light beam incident on the diffusion plate  310  (incident toward the left side in the drawing) is differently bent depending on a position where the light beam is incident on the beads  312 . As a result, the light incident on the diffusion plate  310  is emitted as diffused light from the diffusion plate  310 . Note that returning of the light having entered the diffusion plate  310 , to the incident side is suppressed. 
         [0067]    Referring back to  FIG. 5 , the green light emitted from the laser element  308  is converted into very thin parallel light by the collimator lens  309 , and enters the diffusion plate  310 . The green light having entered the diffusion plate  310  is converted into diffused light and passes through an opening of the aperture  313 , and then is converted into parallel light by the collimator lens  314 . The green light having been converted into the parallel light is converged on an incident surface  305  of the second rod integrator  304  by the converging lens  315 . 
         [0068]    In the third embodiment, only the green light from the laser element  308  is emitted from the second light source section  307 . Where: E 1  denotes the etendue of the first light source section  300 ; E 2  denotes the etendue of the second light source section  307 ; and E 1 ′ denotes the etendue of the first light source section  316 , a relationship of E 1 =E 1 ′&gt;E 2  is satisfied. In addition, a converging angle θ 1  of light emitted from the first light source section  300 , a converging angle θ 2  of light emitted from the second light source section  307 , and a converging angle θ 1 ′ of light emitted from the first light source section  316  are substantially equal to each other. Thus, in the third embodiment, the surface area (S 2 −S 1 -S 1 ′) of the second region R 2  on which the light from the second light source section  307  is incident, is set so as to be smaller than: the surface area S 1  of the first region R 1  on which the light from the first light source section  300  is incident; and the surface area S 1 ′ of the first region R 1 ′ on which the light from the first light source section  316  is incident (where S 2  denotes the area of the incident surface  305 ), thereby effectively using the light from each light source section. 
         [0069]    Preferably, as shown in the following equation (3), the surface areas S 1  and S 1 ′ of the first regions R 1  and R 1 ′ and the surface area (S 2 −S 1 −S 1 ′) of the second region R 2  are substantially proportional to the etendues of the first light source sections  300  and  316  and the second light source section  307 , respectively. 
         [0000]        S 1 /E 1 =S 1 ′/E 1′=( S 2 −S 1 −S 1′)/ E 2  (3)
 
         [0070]    In the third embodiment, in the second light source section  307 , the diffusion plate  310  formed from the materials having different refractive indexes is used for diffusing the green light. However, the diffusion plate is not necessarily limited thereto, and, for example, frosted glass may be used as the diffusion plate. 
         [0071]    In the third embodiment, for the purpose of compensating for an insufficient amount of light, the laser element  308  of the second light source section  307  emits green light. Thus, when red light is insufficient, a laser element emitting red light may be used, and when blue light is insufficient, a laser element emitting blue light may be used. When lights of multiple colors are insufficient, multiple laser elements corresponding to the insufficient colors may be provided, and lights emitted from the multiple laser elements may be combined by a dichroic mirror. 
         [0072]    In the third embodiment, the first light source section  300  and the first light source section  316  have the same configuration. However, the present invention is not particularly limited thereto, and the first light source section  300  and the first light source section  316  may have different configurations such that E 1 ≠E 1 ′ (R 1 ≠R 1 ′). 
       Fourth Embodiment 
       [0073]      FIG. 7  is a configuration diagram of a lighting device according to a fourth embodiment. 
         [0074]    The lighting device  4  according to the fourth embodiment is different from the lighting device  1  according to the first embodiment in the configurations of the light source sections. 
         [0075]    Similarly to the second light source section  207  of the second embodiment, a first light source section  320  includes an LED  325  emitting green light, an LED  326  emitting blue light, and an LED  327  emitting red light. The light emitted from each of the LEDs  325 ,  326 , and  327  is converged on an incident surface  348  of a first rod integrator  347  by a converging lens  346 . 
         [0076]    A second light source section  321  includes a laser element  328  emitting green light, a laser element  334  emitting blue light, a laser element  339  emitting red light, collimator lenses  329 ,  332 ,  335 ,  338 ,  340 , and  343 , diffusion plates  330 ,  336 , and  341 , apertures  331 ,  337 , and  342 , and a converging lens  345 . 
       Fifth Embodiment 
       [0077]      FIG. 8  is a configuration diagram of a lighting device according to a fifth embodiment. 
         [0078]    The lighting device  5  according to the fifth embodiment is different from the lighting device  4  according to the fourth embodiment in the configuration of the second light source section. 
         [0079]    A second light source section  323  includes a laser element  351  emitting green light, a laser element  352  emitting blue light, and an LED  353  emitting red light. The light emitted from each of the laser elements  351  and  352  and the LED  353  is converged on an incident surface  363  of a second rod integrator  362  by a converging lens  361 . In light of uniformity and light use efficiency, it is desirable to set the etendue of the second light source section  323  to an etendue obtained after the lights from the laser elements are diffused. 
         [0080]    In the second light source section  323  of the fifth embodiment, only the red light is emitted from the LED, and the green light and the blue light are emitted from the laser elements. However, the present invention is not particularly limited thereto, and green light may be emitted from an LED and blue light and red light may be emitted from laser elements, or blue light may be emitted from an LED and green light and red light may be emitted from laser elements. 
       Sixth Embodiment 
       [0081]      FIG. 9  is a configuration diagram of a lighting device according to a sixth embodiment. 
         [0082]    In the lighting device  6 , instead of the first rod integrator, a right-angle prism  324  is used as an optical element that guides light from a first light source section  354  to a second rod integrator  356 . When three light source sections are provided as in the third embodiment, a pair of right-angle prisms may be used or a first rod integrator and a right-angle prism may be used in combination, instead of the pair of first rod integrators shown in  FIG. 5 . 
         [0083]    What is important in the first to sixth embodiments is that, when lights from a plurality of light source sections, which are guided by the first rod integrator and/or the right-angle prism, are incident on the incident surface of the second rod integrator, the central axes of the incident lights are parallel to each other, the converging angles of the incident lights are substantially equal to each other, and the incident area of each incident light is set to have an optimum size according to each light source section. As a result, even when a plurality of light source sections having etendues different from each other is used, an optical system can be achieved which can obtain a high-brightness and high-quality image. 
         [0084]    In the above first to sixth embodiments, a mirror rod type in which four mirrors are formed in a state where a reflection surface faces inward, may be used as the second rod integrator. 
         [0085]    Further, in the above first to sixth embodiments, the configurations shown in  FIGS. 1 ,  4 ,  5 ,  7 ,  8 , and  9  are used as the configurations of the first light source section and the second light source section, but the present invention is not particularly limited thereto. In the present invention, any combination of: a light source section in which LEDs emit lights of three primary colors, respectively; a light source section in which fluorescent materials emit lights of three primary colors, respectively by being excited by light emitted from a laser element; a light source section in which diffusion sections each diffusing light emitted from a laser element emits lights of three primary colors, respectively; a light source section that includes light sources respectively emitting lights of three primary colors, in combination with an LED and a fluorescent material that emits light by being excited by light emitted from a laser element; a light source section that includes light sources respectively emitting lights of three primary colors, in combination with an LED and a diffusion section that diffuses light emitted from a laser element; a light source section that includes light sources respectively emitting lights of three primary colors, in combination with a fluorescent material that emits light by being excited by light emitted from a laser element and a diffusion section that diffuses light emitted from a laser element, can be used as the first and second light source sections. The surface area of the first region and the surface area of the second region can be set to be optimum according to the etendue of each light source section. 
       Seventh Embodiment 
       [0086]      FIG. 10  is a configuration diagram of a lighting device according to a seventh embodiment. 
         [0087]    The lighting device  7  includes a first light source section  400 , a second light source section  405 , a right-angle prism  401 , a first multi-lens array integrator  402 , a second multi-lens array integrator  403 , and a converging lens  404 . 
         [0088]    In the first multi-lens array integrator  402 , a large number of lenses are two-dimensionally arranged. An incident surface  407  of the first multi-lens array integrator  402  is divided into a first region R 1  on which light from the first light source section  400  is incident, and a second region R 2  on which light from the second light source section  405  is incident. 
         [0089]    In the second multi-lens array integrator  403 , a large number of lenses are two-dimensionally arranged. Each lens constituting the second multi-lens array integrator  403  corresponds to each lens constituting the first multi-lens array integrator  402  in a one-to-one relation. Each lens constituting the first multi-lens array integrator  402  has a focal point located on the corresponding one of the lenses constituting the second multi-lens array integrator  403 . Thus, the light emitted from the first light source section  400  forms, on each lens of the first multi-lens array integrator  402 , an image having a shape of the lens, and enters the converging lens  404 . 
         [0090]    The converging lens  404  coaxially overlaps the image formed on each lens of the first multi-lens array integrator  402 . Thus, uniform illumination is achieved. 
         [0091]    The right-angle prism  401  guides the light emitted from the first light source section  400 , to the first multi-lens array integrator  402 . Specifically, the light emitted from the first light source section  400  is bent by the right-angle prism  401 , and is perpendicularly incident on the first region R 1  on the incident surface  407  of the first multi-lens array integrator  402 . Meanwhile, the light from the second light source section  405  is directly incident on the second region R 2 . 
         [0092]    The right-angle prism  401  is disposed to the opposite side of the first multi-lens array integrator  402  with respect to the second multi-lens array integrator  403  (to the light side in the drawing) in a state where an exit surface  421  thereof faces the first region R 1 . A reflecting surface  411  of the right-angle prism  401  is inclined relative to a plane that includes the boundary between the first region R 1  and the second region R 2  and that is perpendicular to the incident surface  407  of the first multi-lens array integrator  402 . Thus, a space is formed to the second light source section  405  side of the first region R 1  and the second region R 2 . By causing the light emitted from the second light source section  405  to pass within this space, an optical system can be disposed such that: the first light source section  400  and the second light source section  405  do not interfere with each other; and an optical path of the light from the first light source section  400  and an optical path of the light from the second light source section  405  do not interfere with each other. 
         [0093]    The first light source section  400  is obtained by omitting the converging lens from the first light source section  300  of the third embodiment, and the second light source section  405  is obtained by omitting the converging lens from the second light source section  321  of the third embodiment. Thus, the repeated description is omitted here. 
         [0094]    The etendue E 1  of the first light source section  400  is higher than the etendue E 2  of the second light source section  405 . In addition, the light that is emitted from the first light source section  400  and enters the first multi-lens array integrator  402 , and the light that is emitted from the second light source section  405  and enters the first multi-lens array integrator  402 , are substantially parallel to each other. Thus, on the basis of the above equation (1), the surface area (indicated by S 1 ) of the first region R 1  is set so as to be larger than the surface area (indicated by S 2 −S 1 ; here, S 2  is equal to the area of the exit surface  421  of the right-angle prism  401 ) of the second region R 2 . 
       Eighth Embodiment 
       [0095]      FIG. 11  is a configuration diagram of a lighting device according to an eighth embodiment. 
         [0096]    The lighting device  8  according to the eighth embodiment is different from the lighting device  7  according to the seventh embodiment in the number of right-angle prisms and the configurations of the light source sections. 
         [0097]    The lighting device  8  includes a pair of right-angle prisms  412  and  414 , a pair of first light source sections  408  and  410 , a second light source section  409 , a first multi-lens array integrator  416 , a second multi-lens array integrator  420 , and a converging lens  421 . 
         [0098]    The right-angle prism  412  guides light emitted from the first light source section  408 , to a first region R 1  on an incident surface  417  of the first multi-lens array integrator  416 . The right-angle prism  414  guides light emitted from the first light source section  410 , to a first region R 1 ′ on the incident surface  417  of the first multi-lens array integrator  416 . 
         [0099]    The right-angle prisms  412  and  414  are disposed to the opposite side of the first multi-lens array integrator  402  with respect to the second multi-lens array integrator  403  (to the right side in the drawing) in a state where exit surfaces  418  and  419  face the first regions R 1  and R 1 ′, respectively. A reflecting surface  413  of the right-angle prism  412  is inclined relative to a plane that includes the boundary between the first region R 1  and the second region R 2  and that is perpendicular to the incident surface  417  of the first multi-lens array integrator  416 . Similarly, a reflecting surface  415  of the right-angle prism  414  is inclined relative to a plane that includes the boundary between the first region R 1 ′ and the second region R 2  and that is perpendicular to the incident surface  417  of the first multi-lens array integrator  416 . Further, the reflecting surfaces  413  and  415  spread apart with increasing distance from the incident surface  417 . Thus, a space is formed to the second light source section  409  side of the first regions R 1  and R 1 ′ and the second region R 2 . By causing light emitted from the second light source section  409  to pass within this space, an optical system can be disposed such that: the first light source section  408 , the second light source section  409 , and the first light source section  410  do not interfere with each other; and an optical path of the light from the first light source section  408 , an optical path of the light from the second light source section  409 , and an optical path of the light from the first light source section  410  do not interfere with each other. 
         [0100]    The first multi-lens array integrator  416 , the second multi-lens array integrator  420 , and the converging lens  421  are the same as the first multi-lens array integrator  402 , the second multi-lens array integrator  403 , and the converging lens  404  of the seventh embodiment. Thus, the repeated description is omitted here. 
         [0101]    The first light source sections  408  and  410  have the same configuration as that of the first light source section  400  of the fourth embodiment. In addition, the second light source section  409  has a configuration obtained by omitting the converging lens  135  from the second light source section  122  of the first embodiment. Thus, the repeated description is omitted here. 
         [0102]    In the seventh and eighth embodiments, the lights from the light source sections are guided to the first multi-lens array integrator by using the right-angle prism. However, a total reflection mirror plate may be used instead of the right-angle prism. 
         [0103]    Further, in the seventh and eighth embodiments, a rod integrator can be used instead of the right-angle prism. However, parallel light, or light having an acute converging angle relative to the incident surface, enters the first multi-lens array integrator. Thus, when the right-angle prism is used, the length of the optical path of the light can be shortened, and hence this advantageously contributes to size reduction and cost reduction of the lighting device. 
       Ninth Embodiment 
       [0104]      FIG. 12  is a configuration diagram of a projection type image display apparatus according to a ninth embodiment. 
         [0105]    The projection type image display apparatus  10  includes the lighting device  1  shown in  FIG. 1 , relay lenses  501  and  502 , a redirecting mirror  503 , a curved mirror  504 , a digital mirror device (DMD)  505 , which is an image display element, and a projection lens  506 . 
         [0106]    Light emitted from the second rod integrator is incident on the DMD  505  through the relay lenses  501  and  502 , the redirecting mirror  503 , and the curved mirror  504 . In the DMD  505 , micro-mirrors are two-dimensionally arranged, and an inclination of each mirror is adjusted in accordance with an external input signal. For example, a mirror located at a position corresponding to a pixel for white display is inclined in a direction that decreases the incident angle of light. Meanwhile, a mirror located at a position corresponding to a pixel for black display is inclined in a direction that increases the incident angle of light. Light reflected by each mirror passes through the projection lens  506 , and is projected as an image on a screen (not shown). At this time, the shape of the exit surface of the second rod integrator is transferred on the DMD  505 , and thus the light emitted from the second rod integrator can be efficiently and uniformly converged. 
         [0107]    Moreover, the DMD  505  performs high-speed drive of the minors by a drive circuit (not shown), for example, in accordance with video signals for red, green, and blue, thereby performing color display. Therefore, when the DMD  505  is driven in accordance with a video signal for red, the lighting device  1  is controlled such that red light is emitted from both the first light source section  100  and the second light source section  122 ; when the DMD  505  is driven in accordance with a video signal for green, the lighting device  1  is controlled such that green light is emitted from both the first light source section  100  and the second light source section  122 ; and when the DMD  505  is driven in accordance with a video signal for blue, the lighting device  1  is controlled such that blue light is emitted from both the first light source section  100  and the second light source section  122 . 
         [0108]    In the ninth embodiment, the DMD is used as an image display element. However, for example, an LCOS (LIQUID CRYSTAL ON SILICON) which quickly switches a drive signal may be used. 
         [0109]    Further, in the ninth embodiment, the lighting device using the second rod integrator is used, but the lighting device using the first and second multi-lens array integrators as shown in  FIG. 10  may be used. 
         [0110]    The present invention is applicable to, for example, a lighting device that is required to have high output of light, and a projection type image display apparatus using the lighting device. 
         [0111]    Although the present invention has been fully described by way of example with reference to the accompanying drawings, it is to be understood that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modification depart from the scope of the present invention, they should be construed as being included therein.