CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is based on and claims priority from Japanese Patent Application Number 2012-200234, filed on Sep. 12, 2012, the disclosure of which is hereby incorporated by reference herein in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Present Invention 
         [0003]    The present invention relates to an illumination light source device, a projection device including the illumination light source device and an improved method to control the projection device. 
         [0004]    2. Description of the Related Art 
         [0005]    Conventionally, light source devices employing a high-intensity discharge lamp such as an extra high pressure mercury lamp, as illumination light source devices for projection devices (projector) projecting on-screen information of a personal computer (hereinafter referred to as “PC”) at conferences and meetings have been known. 
         [0006]    However, the discharge lamp takes a necessary time to emit light stably after start of lighting, while enables high-brightness at low cost. 
         [0007]    Then, using a solid-state light-emitting element such as a light-emitting diode or an organic light emitting diode of red (R), green (G), and blue (B) as an alternate light source in place of the discharge lamp has been proposed and put into practical use. 
         [0008]    By using the solid-state light-emitting element as a light source for a projector, the projector can be started-up quickly and can be configured to accomplish a care of environment. 
         [0009]    Then, for example, Japanese Patent Application Publication No. 2011-013316 (Patent Document 1) and Japanese Patent Application Publication No. 2010-085745 (Patent Document 2) were developed to solve the problem mentioned above. 
         [0010]    As the illumination light source device employing the solid-state light-emitting element, for example, it is widely known that the skill to obtain a colored projection image by irradiating a fluorescent body with laser light as a excitation light emitted by a blue laser diode used as a first light source (excitation light source), producing each light of R, G, and B by exiting the fluorescent body, and controlling gradation each light of R, G, and B by use of a light modulation device such as a DMD (Digital Micromirror Device)(refer to Patent Document 1). 
         [0011]    An illumination light source device according to Patent Document 1 includes a luminescent plate (fluorescent wheel) composed of a fluorescent body layer having a plurality of segmented regions divided in a rotational direction and emitting fluorescent light by receiving excitation light and a transmission region transmitting the excitation light directly, a first light source irradiating the fluorescent body with the excitation light, a second light source emitting light of a different wavelength from both of the excitation light and the fluorescence emitted by the fluorescent body layer, a light collection optical system collecting light emitted by the luminescent plate (fluorescent wheel) and the light emitted by the second light source on the same light-path, and an emission control section controlling the first light source and the second light source. 
         [0012]    The emission control section turns off the first light source not to emit a light by the first light source and turn on the second light source to emit a light by the second light source, in order to prevent a color mixture at a boundary of adjacent segmented regions. 
         [0013]    The illumination light source device according to Patent Document 1 can prevent the color mixture at the boundary of the adjacent segmented regions by being configured to control to turn off the first light source at the boundary. However, a time period that the segmented region is irradiated with the excitation light per unit time (one second) is constant regardless of its revolutions of the fluorescent wheel per unit time (one second), since the illumination light source device is configured so that the fluorescent body of the fluorescent wheel is directly irradiated with the excitation light. Therefore, a fluorescence property of the fluorescent body may be deteriorated if a mini-region of the segmented region remains irradiated with the excitation light. 
         [0014]    Now, there are being developed illumination light source devices capable of keeping the fluorescent property of the fluorescent body from deteriorating by enabling the fluorescent body to change the time that being irradiated with the excitation light in unit time by providing a reflection-transmission wheel as a reflection-transmission member having a transmission region and the reflection region on a light-path of the excitation light emitted by the first light source, providing a fluorescent wheel as a fluorescent member on at least one of a transmission light-path made of the transmission region and a reflection light-path made of the reflection region, and switching the light-path of the excitation light between the transmission light-path and the reflection light-path in an unit time (one second) of rotation of the fluorescent wheel. 
         [0015]    However, a color mixture occurs when the reflection-transmission wheel is irradiated with the excitation light while a boundary region between the reflection region and the transmission region is passing through, even if the illumination light source device is configured so that the reflection-transmission wheel is provided on the light-path of the excitation light emitted by the first light source. 
         [0016]    Moreover, to prevent the color mixture, turning off an excitation light source while the boundary region between the reflection region and the transmission region is passing through the light-path of the excitation light is one idea. But, such a configuration to turn off the excitation light source decreases the brightness. 
       SUMMARY OF THE INVENTION 
       [0017]    The present invention is made in view of the above, and an object thereof is to provide an illumination light source device capable of further preventing the deterioration of a fluorescent body, capable of improving a color reproducibility by obtaining a lot of colors by use of the color mixture generated at a boundary region between a transmission light-path and a reflection light-path effectively and capable of improving brightness of an image, a projector including the illumination light source device and a method to control the projector. 
         [0018]    An illumination light source device according to an embodiment of the present invention includes a reflection-transmission member provided on a light-path of an excitation light from an excitation light source having a transmission region transmits an excitation light as an optical wavelength and a reflection region reflecting the excitation light from the excitation light source and the transmission region and the reflection region sequentially traverse the light-path of the excitation light from the excitation light source, a fluorescent body member provided on at least one of the reflection light-path formed of the reflection region or the transmission light-path formed of the transmission region having the fluorescent body emitting fluorescence when excited by the excitation light, and a control section turning-on the excitation light source while the boundary of the transmission region and the reflection region of the reflection-transmission wheel traverses the light-path of the excitation light. 
         [0019]    The illumination light source device according to the present invention is configured so that the fluorescent body is excited by the excitation light led by at least one of the transmission region and the reflection region of the reflection-transmission member, and a time that the fluorescent body is irradiated with the excitation light in unit time can be shortened, thus a deterioration of the fluorescent body can be prevented. 
         [0020]    Moreover, the illumination light source device according to the present invention can improves the color reproducibility by obtaining a wide variety of colors by use of the color mixture occurred in the boundary region between the transmission light-path and the reflection light-path effectively, and improves the brightness of projection image, because of having a configuration so that the excitation light source is turned-on while the boundary between the transmission region and the reflection region on the reflection-transmission member traverses the light-path of the excitation light-path. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  illustrates an optical system of an illumination light source device according to a first embodiment of the present invention; 
           [0022]      FIG. 2  is an enlarged plan view of a fluorescent wheel in the illumination light source device shown in  FIG. 1 ; 
           [0023]      FIG. 3  is an enlarged plan view of a reflection-transmission wheel in the illumination light source device shown in  FIG. 1 ; 
           [0024]      FIG. 4  illustrates a relationship between the reflection-transmission wheel and a light-path of a first illumination optical system in the illumination light source device shown in  FIG. 1 ; 
           [0025]      FIG. 5  illustrates an example of a configuration of a projection device according to a second embodiment of the present invention using the illumination light source device shown in  FIG. 1 ; 
           [0026]      FIG. 6  illustrates an example of a relationship among a color of light irradiating with an image generator shown in  FIG. 5 , on/off timing of each light source, and reflection /transmission of the reflection-transmission wheel, in relationship to a frame of images; 
           [0027]      FIG. 7  illustrates a relationship between a rotational angle position of the reflection-transmission wheel shown in  FIG. 1  and the light-path of the first illumination optical system shown in  FIG. 1 ; 
           [0028]      FIG. 8  is a block diagram illustrating the configuration of a control section shown in  FIG. 5 ; 
           [0029]      FIG. 9A  illustrates a state that one boundary of the reflection-transmission wheel is overlaps with one of tangent to a spot region when the boundary traverses the spot region; 
           [0030]      FIG. 9B  illustrates a state in that one boundary of the reflection-transmission wheel overlaps with other tangent to a spot region when the boundary traverses the spot region; 
           [0031]      FIG. 10  illustrates a relationship among a rotational phase of the reflection-transmission wheel, a lighting of the second light source, and intensity of illumination light, wherein (a) illustrates the rotational phase of the reflection-transmission wheel, (b) illustrates on-state of the second light source, and (c) illustrates a relationship between intensity of excitation light at a wavelength λA and intensity of fluorescence at a wavelength λB corresponding to the rotational phase (a); 
           [0032]      FIG. 11  illustrates variations of angular range of the spot region wherein  FIGS. 11A , B are same to  FIGS. 9A , B and reposted for reference, and FIGS.  11 C,D are  FIGS. 11A , B wherein the angular range is doubled; 
           [0033]      FIG. 12  illustrates an example of a relationship of intensity between the wheel-rotational phase of the reflection-transmission wheel and the illumination wherein (a) and (c) are same to  FIG. 10(   a )( c ) and reposted for reference, (b) illustrates the wheel-rotational phase corresponding to  FIGS. 11C , and  11 D, and (d) illustrates a relationship between the intensity of the excitation light at the wavelength λA and the intensity of fluorescence at the wavelength λB corresponding to the wheel-rotational phase shown in  FIG. 12(   b ); 
           [0034]      FIG. 13  illustrates other examples of the reflection-transmission wheel wherein  FIGS. 13A , and  13 B are same to  FIGS. 9A , and  9 B and reposted for reference, and  FIGS. 13C ,  13 D, and  13 E illustrate a state that the reflection region is split into a beam-splitter region and the total reflection region, wherein  FIG. 13C  illustrates a state that forward boundary of the beam-splitter region in rotational direction is overlapped with one of the tangent,  FIG. 13D  illustrates a state that the boundary between the beam-splitter region and the total reflection region is overlapped with one of the tangent,  FIG. 13E  illustrates a state that forward boundary of the total reflection region in rotational direction is overlapped with other tangent; 
           [0035]      FIG. 14  illustrates an example of a relationship of intensity between the wheel-rotational phase of the reflection-transmission wheel and the illumination wherein (a) is same to  FIG. 12(   a ) and reposted for reference, (b) illustrates the wheel-rotational phase when the boundary between the transmission region and the beam-splitter region on the reflection-transmission wheel shown in  FIGS. 13C ,  13 D, and  13 E is passing through the spot region, (c) illustrates the wheel-rotational phase when the boundary between the beam-splitter region and the total reflection region on the reflection-transmission wheel shown in  FIGS. 13C ,  13 D, and  13 E is passing through the spot region, (d) is same to  FIG. 12(   c ) and reposted for reference, (e) illustrates a relationship between the intensity of excitation light at the wavelength λA and the intensity of fluorescence at the wavelength λB corresponding to the rotational phase of the reflection-transmission wheel shown in  FIG. 12(   b ); 
           [0036]      FIG. 15  illustrates white-light generation wherein  FIGS. 15A , and  15 B are same to  FIGS. 9A , and  9 B and reposted for reference; 
           [0037]      FIG. 16  illustrates white-light generation wherein (a) is same to  FIG. 10(   a ) and reposted for reference, (b) illustrates a driving state of the light source  2 , (c) illustrates a driving state of the light source  3 , and (d) illustrates a generated white-light; 
           [0038]      FIG. 17  is a pattern diagram illustrates an example of a sensor detecting the rotational angle position of reflection-transmission wheel; 
           [0039]      FIG. 18  is a pattern diagram illustrates a relationship between the rotational angle position and the gravity acceleration of an acceleration sensor; 
           [0040]      FIG. 19  illustrates an optical system of a light source device according to a third embodiment of the present invention; 
           [0041]      FIG. 20  illustrates an example of a relationship among a color of light which irradiates an image generator by use of the illumination light source shown in  FIG. 19 , on/off timing of each light source, and reflection/transmission of the reflection-transmission wheel, in relationship to a frame of images; 
           [0042]      FIG. 21  illustrates another example of a relationship among colors of light irradiating an image generator by use of the illumination light source shown in  FIG. 19 , on/off timing of each light source, and reflection/transmission of the reflection-transmission wheel, in relationship to a frame of images; 
           [0043]      FIG. 22  illustrates an optical system of a light source device according to a fourth embodiment of the present invention; 
           [0044]      FIG. 23  is a partially enlarged view of the first illumination optical system shown in  FIG. 22 ; 
           [0045]      FIG. 24  illustrates the spot region generated on the reflection-transmission wheel by the first illumination optical system shown in  FIG. 22 ; 
           [0046]      FIG. 25  illustrates an optical system of a light source device according to a fifth embodiment of the present invention; 
           [0047]      FIG. 26  is a plan view of the reflection-transmission wheel shown in  FIG. 25 ; 
           [0048]      FIG. 27  is a plan view of a fluorescent wheel shown in  FIG. 25 ; 
           [0049]      FIG. 28  illustrates an example of a relationship among a color of light which irradiates the image generator by use of the illumination light source device shown in  FIG. 25 , on/off timing of each light source, and reflection/transmission of the reflection-transmission wheel, in relationship to a frame of images; 
           [0050]      FIG. 29A  illustrates the rotational angle position of the reflection-transmission wheel shown in  FIG. 26  wherein one boundary is angled at 45 degrees as a reference position; 
           [0051]      FIG. 29B  illustrates the rotational angle position of the reflection-transmission wheel shown in  FIG. 26  wherein one boundary is angled at 135 degrees; 
           [0052]      FIG. 29C  illustrates the rotational angle position of the reflection-transmission wheel shown in  FIG. 26  wherein one boundary is angled at 150 degrees; 
           [0053]      FIG. 29D  illustrates the rotational angle position of the reflection-transmission wheel shown in  FIG. 26  wherein one boundary is angled at 165 degrees; 
           [0054]      FIG. 29E  illustrates the rotational angle position of the reflection-transmission wheel shown in  FIG. 26  wherein one boundary is angled at 195 degrees; 
           [0055]      FIG. 29F  illustrates the rotational angle position of the reflection-transmission wheel shown in  FIG. 26  wherein one boundary is angled at 210 degrees; 
           [0056]      FIG. 29G  illustrates the rotational angle position of the reflection-transmission wheel shown in  FIG. 26  wherein one boundary is angled at 225 degrees; 
           [0057]      FIG. 30A  illustrates the rotational angle position of the fluorescent wheel shown in  FIG. 27  wherein one boundary is angled at 0 as a reference position; 
           [0058]      FIG. 30B  illustrates again the rotational angle position of the fluorescent wheel shown in  FIG. 27  wherein one boundary is angled at 0 degree; 
           [0059]      FIG. 30C  illustrates the rotational angle position of the fluorescent wheel shown in  FIG. 27  wherein one boundary is angled at 60 degrees; 
           [0060]      FIG. 30D  illustrates the rotational angle position of the fluorescent wheel shown in  FIG. 27  wherein one boundary is angled at 120 degrees; 
           [0061]      FIG. 30E  illustrates the rotational angle position of the fluorescent wheel shown in  FIG. 27  wherein one boundary is angled at 240 degrees; 
           [0062]      FIG. 30F  illustrates the rotational angle position of the fluorescent wheel shown in  FIG. 27  wherein one boundary is angled at 300 degrees; 
           [0063]      FIG. 30G  illustrates the rotational angle position of the fluorescent wheel shown in  FIG. 27  wherein one boundary is angled at 60 degrees; 
           [0064]      FIG. 31  illustrates a relationship among the rotational angle position of each wheel, the rotational phase of each wheels, and a color of light which irradiates the image generator when the light source  2  is turned on, with using the reflection-transmission wheel shown in  FIG. 26  and the fluorescent wheel shown in  FIG. 27 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0065]    Embodiments of the present invention will be described hereinafter in detail with reference to the accompanying drawings. 
       First Embodiment 
       [0066]      FIG. 1  illustrates an optical system of a light source device according to a first embodiment of the present invention wherein numeral  1  shows an illumination optical system. 
       (Schematic Configuration of the Illumination Optical System  1   
       [0067]    In this case, the illumination optical system has two illumination light sources (hereinafter referred to as “light sources”)  2 ,  3 . The light source  2  forms a part of a first illumination optical system  1 A, and the light source  3  forms a part of a second illumination optical system  1 B. 
         [0068]    The first illumination optical system  1 A is schematically composed of a coupling lens  2   a  as a first optical element, a reflection-transmission wheel  2   b  as a reflection-transmission member, a total reflection mirror  2   c , and a fluorescent wheel  2   e  as a fluorescent body member. 
         [0069]    The reflection-transmission wheel  2   b  is arranged on a light-path of the light source  2 . The light-path of the light source  2  is split into a transmission light-path and a reflection light-path by a transmission region and a reflection region of the reflection-transmission wheel  2   b  (it will be described later). 
         [0070]    The second illumination optical system  1 B is schematically composed of a coupling lens  3   a , a dichroic mirror  3   b , and a dichroic mirror  3   c . The dichroic mirror  3   b  and the dichroic mirror  3   c  are shared by the first illumination optical system  1 A. 
         [0071]    The fluorescent wheel  2   e  is formed of a disk-shaped substrate  2   g  and a fluorescent body  2   h , and arranged on the transmission light-path formed by the transmission region of the reflection-transmission wheel  2   b . A collecting element  2   i  is provided on a front side of the fluorescent wheel  2   a.    
       (Detailed Configuration of the First Illumination Optical System  1 A) 
       [0072]    The light source  2  is a solid-state light-emitting element emitting an excitation light of a short wavelength. For example, a blue laser diode emitting a blue laser light as a visible light is used as the light source  2 . Note that, a light-emitting diode emitting a blue light can be used in place of the blue laser diode. Here, the light source  2  emits light in a wavelength λA (400 nm&lt;λA&lt;450 nm). 
         [0073]      FIG. 2  illustrates the disk-shaped substrate  2   g  of the fluorescent wheel  2   e  viewed from the side where the fluorescent body  2   h  is formed. The disk-shaped substrate  2   g  is formed of a reflection material, and the fluorescent body  2   h  is formed into a ring shape. The disk-shaped substrate  2   g  is rotationally driven by a drive part  2   f  as a second drive member on a rotating shaft  2   j.    
         [0074]    The light in the wavelength λA is reflected by the total reflection mirror  2   c  after transmitting the transmission region of the reflection-transmission wheel  2   b , collected by the collecting element  2   j , and irradiates the fluorescent wheel  2   e.    
         [0075]    At that time, a mini-region  2   hm  of the fluorescent body  2   h  is irradiated with the light in the wavelength λA in a spot as shown in  FIG. 2 . If the same mini-region  2   hm  of the fluorescent body  2   h  remains irradiated by the light in the wavelength λA, the fluorescent body  2   h  may become so called a “burnt” state, and a property of the fluorescent body  2   h  may be deteriorated or broken. 
         [0076]    However, in the configuration according to the first embodiment, it is prevented that the same mini-region  2   hm  of the fluorescent body  2   h  continues to be irradiated with the light energy in the wavelength λA and the property of the fluorescent body  2   h  is deteriorated since the disk-shaped substrate  2   g  is constantly rotationally driven on a rotating shaft  2   j  and the mini-region of the fluorescent body  2   hm  irradiated with the light in the wavelength λA is temporally-shifted. Note that, a rotating speed of the disk-shaped substrate  2   g  is not limited in particular. 
         [0077]    Note that, the first embodiment is configured to prevent that the same mini-region of a fluorescent body  2   hm  continues to be irradiated by the light in the wavelength λA by rotating the disk-shaped substrate  2   g , but not limited to this configuration. For example, the mini-region  2   hm  of the fluorescent body  2   h  irradiated with the light in the wavelength λA can be temporally-shifted by employing a rectangle-shaped substrate (not shown) in place of the disk-shaped substrate  2   g , forming the fluorescent body  2   h  extending in a longitudinal direction of the rectangle-shaped substrate, and periodically reciprocating the rectangle-shaped substrate in a longitudinal direction and in a direction perpendicular to the light in the wavelength λA. 
         [0078]    The fluorescent body  2   h  is excited by the light in the wavelength λA and emits fluorescence in a wavelength λB longer than the wavelength λA as shown in  FIG. 1 . For example, a range of the wavelength λB is within 495 nm&lt;λB&lt;570 nm which is a green fluorescence. 
         [0079]    The fluorescence in the wavelength λB is reflected by disk-shaped substrate  2   g , collected by a collecting element, and emitted from the fluorescent wheel  2   e.    
         [0080]    The reflection-transmission wheel  2   b  is rotationally driven on a rotating shaft  2   m  by a drive part  2   n  as a first drive member. The reflection-transmission wheel  2   b  has a fan-shaped reflection region  2   p  bounded by two radial region boundary  2   r   1 ,  2   r   2  and an arc  2   r   5  as shown in  FIG. 3 . 
         [0081]    The reflection region  2   p  has a function that totally reflects the light in the wavelength λA. The rest of the reflection region  2   p  of the reflection-transmission wheel  2   b  is a transmission region  2   q  totally transmitting the light in the wavelength λA. 
         [0082]    In the first embodiment, the reflection-transmission wheel  2   b  is formed of a transparent disk with the fan-shaped reflection region  2   p , that is to say the rest of the reflection region  2   p  is the transmission region  2   q . But, if the reflection-transmission wheel  2   b  is formed by the fan-shaped reflection region  2   p  itself, a material can be saved, and the production cost for a device can be reduced. 
         [0083]    Note that, in the first embodiment, an angular range of the fan-shaped reflection region  2   p , a pivot point thereof is the rotating shaft  2   m , is 90 degrees, but a dimension of the reflection region  2   p  is not limited to this. 
         [0084]    Moreover, in the first embodiment, the reflection region  2   p  and the transmission region  2   q  are switched by rotating the reflection-transmission wheel  2   b , but the reflection region  2   p  and the transmission region  2   q  can be switched by reciprocating the rectangle-shaped substrate. 
         [0085]    The reflection-transmission wheel  2   b  is arranged obliquely relative to an optical axis O 1  of the light-path of the first illumination optical system  1 A. In the first embodiment, the reflection-transmission wheel  2   b  is arranged at 45 degrees relative to the optical axis O 1 , but it is not limited to this angle if the light-path of the excitation light in the wavelength λA can be switched. 
         [0086]    Furthermore, the incidence of speckle pattern can be decreased by using the diffuser panel in place of the transmission region  2   q  of the reflection-transmission wheel  2   b.    
         [0087]    The reflection-transmission wheel  2   b  is appropriately rotated in synchronization with the image data, and the transmission light-path and the reflection light-path are appropriately selected corresponding to the color of the image data to be formed. Here, for example, the reflection-transmission wheel  2   b  rotates 30 times every second, and rotates once or twice every one frame (e.g., 1/30 seconds). 
         [0088]    Namely, the light in the wavelength λA emitted from the light source  2  is led to the reflection-transmission wheel  2   b  via the coupling lens  2   a . Next, the light in the wavelength λA is reflected by the reflection region  2   p  of the reflection-transmission wheel  2   b  and led to the dichroic mirror  3   b  when the reflection region  2   p  is placed at the light-path of the first illumination optical system  1 A, on the other hand, the light in the wavelength λA is led to the total reflection mirror  2   c  through the transmission region  2   q  of the reflection-transmission wheel  2   b  when the transmission region  2   q  is placed at the light-path of the first illumination optical system  1 A. 
       (Detailed Configuration of the Second Illumination Optical System  1 B) 
       [0089]    The light source  3  is the solid-state light-emitting element emitting the light in a wavelength λC longer than the wavelength λB. For example, the range of the wavelength λC is within 620 nm&lt;λC&lt;750 nm which is a red light. Note that, the numeral O 2  refers to the optical axis of the second illumination optical system  1 B. 
         [0090]    The dichroic mirror  3   b  has a function that reflects the light in the wavelength λA and transmits the wavelength λC. The dichroic mirror  3   c  has the function that transmits the light in the wavelength λA and a light in the wavelength λC and reflects a light in the wavelength λB. 
         [0000]    (Detailed Light-Path Formed of the Reflection-Transmission Wheel  2   b , the Dichroic Mirror  3   b , and the Dichroic Mirror  3   c ) 
         [0091]    When the reflection region  2   p  of the reflection-transmission wheel  2   b  is placed at the light-path of the first illumination optical system  1 A, the light in the wavelength λA is reflected by the reflection region  2   p , lead to and reflected by the dichroic mirror  3   b , and emitted as a blue light from the first illumination optical system  1  through the dichroic mirror  3   c.    
         [0092]    When the transmission region  2   q  of the reflection-transmission wheel  2   b  is placed at the light-path of the first illumination optical system  1 A, the light in the wavelength λA transmits the transmission region  2   q , and is reflected by the total reflection mirror  2   c , and led to the fluorescent wheel  2   e  through the dichroic mirror  3   c.    
         [0093]    The light in the wavelength λA is collected by the collecting element  2   i  and irradiates the miniregion of the fluorescent body  2   hm  (see  FIG. 2 ) of the fluorescent body  2   h , then the fluorescent body  2   hm  is excited and emits the light in the wavelength λB. 
         [0094]    The light in the wavelength λA and the light in the wavelength λB are reflected by the disk-shaped substrate  2   g , collected by the collecting element  2   i , and led to the dichroic mirror  3   c . The light in the wavelength λA traverses the dichroic mirror  3   c , on the other hand, the light in the wavelength λB is reflected by the dichroic mirror  3   c  and emitted as a green light from the first illumination optical system  1 . 
         [0095]    The light in the wavelength λC is led to the dichroic mirror  3   b  through the coupling lens  3   a , and emitted as the red light from the first illumination optical system  1  through the dichroic mirror  3   b  and the dichroic mirror  3   c.    
         [0096]    The dichroic mirror  3   c  functions as a light-path junction element forming the converged light-path by converging on the transmission light-path and the reflection light-path which split by the reflection-transmission wheel  2   b.    
         [0097]    According to the first embodiment, the light-path of the excitation light is split into the transmission light-path and the reflection light-path by providing the reflection-transmission wheel  2   b , and a time that the fluorescent body is irradiated with the excitation light in unit time (one second) can be shortened, thus a deterioration of the fluorescence property of the fluorescent body can be prevented. 
         [0000]    (A Problem of the Color Mixture at the Boundary between the Reflection Region  2   p  and the Transmission Region  2   q  of the Reflection-Transmission Wheel  2   b ) 
         [0098]    The light in the wavelength λA traverses the reflection-transmission wheel  2   b  with given dimension as shown in  FIG. 4 . That is to say, the reflection-transmission wheel  2   b  is irradiated with the light in the wavelength λA as a spot. In  FIG. 4 , reference numeral  2   s  refers to the spot region (dimension of the light-path) that the reflection-transmission wheel  2   b  is irradiated with the light in the wavelength λA. 
         [0099]    When the light in the wavelength λA irradiates a boundary region of the reflection-transmission wheel  2   b , the light in the wavelength λA (blue) reflected by the reflection region  2   p  is reflected by the dichroic mirror  3   b  and emitted from the first illumination optical system  1 . On the other hand, the light in the wavelength λA traversed the transmission region  2   q  is reflected by the total reflection mirror  2   c , led to the fluorescent wheel  2   e  through the dichroic mirror  3   c , excites the fluorescent body  2   h  of the fluorescent wheel  2   e , and the green fluorescence (the light in the wavelength λB) from the fluorescent body  2   h  is reflected by the dichroic mirror  3   c  and emitted from the first illumination optical system  1 . 
         [0100]    Thereby, the light which is a mixture of blue light and green right is emitted from the first illumination optical system  1 . Therefore, color mixture is occurred when region boundary  2   r   1 ,  2   r   2  between the reflection region  2   p  and the transmission region  2   q  of the reflection-transmission wheel  2   b  traverse the light-path of the first illumination optical system  1 A. For example, an image of cyan is periodically produced when an image of blue or green is demanded, and color purity is impaired. 
         [0101]    If the light source  2  is turned off in order to prevent the occurrence of the color mixture when the boundary region of the reflection-transmission wheel  2   b  traverses the light-path (spot region), the brightness is decreased since the illumination light from the light source  2  is fail to efficiently utilized. 
         [0102]    Then, in the first embodiment, the light source  2  is turned on positively regardless of the image data and the light source  3  is also turned on in synchronization with the light source  2  when the region boundary  2   r   1 ,  2   r   2  between the reflection region  2   p  and the transmission region  2  of the reflection-transmission wheel  2   b  traverse the light-path of the first illumination optical system  1 A. 
         [0103]    As the result, decreasing of the brightness can be prevented and the color reproducibility can be improved when the region boundary  2   r   1 ,  2   r   2  between the reflection region  2   p  and the transmission region  2   q  of the reflection-transmission wheel  2   b  traverses the light-path. The controlling of the lighting-up will hereinafter be described in detail. 
       Second Embodiment 
       [0104]      FIG. 5  illustrates a second embodiment of the configuration of a projection device  10  using the illumination optical system  1  according to the first embodiment. In  FIG. 5 , elements which are same as in the first embodiment are provided by attaching same numerals thereto and their detailed descriptions are omitted. 
         [0105]    The projection device  10  has a control section  11  controlling the illumination optical system  1 , a collecting element  12 , an integrator  13 , a collecting element  14 , a reflection mirror  15 , an image generator  16 , and a projection lens  17  provided on the light-path forward of the illumination optical system  1 . The collecting element  12 , the integrator  13 , the collecting element  14 , the reflection mirror  15 , the image generator  16 , and the projection lens  17  forms a projection optical system. 
         [0106]    The light flux in the wavelength λA, λB, and λC are collected by the collecting element  12 , diffused uniformly by the integrator  13  to remove an uneven light intensity and irradiates the image generator  16  through the collecting element  14  and the reflection mirror  15 . Hereinafter, the configuration and the function of the image generator  16  will be described. The control section  11  will be described later. 
       (Configuration and Function of the Image Generator  16 ) 
       [0107]    In the image generator  16 , image generation data are inputted. The image generator  16  is formed of, for example, a DMD (Digital Micromirror Device) which is publicly known. 
         [0108]    The DMD has pixel-based micromirrors. The each angle of the micromirrors is two-position controlled, and the micromirror can control the gradation by controlling the repeating time interval of the two-position control. 
         [0109]    Then, the full-color images are generated by use of persistence of vision by irradiating each color of RGB, R (red: wavelength λC), G (green: wavelength λB), and B (blue: wavelength λA) in a time frame of the image by switching, driving the image generator  16  by micromirror drive signal based on the pixel-based image generation data in synchronization with the timing of the irradiating of the each color of RGB. 
       (Configuration and Function of the Control Section  11 ) 
       [0110]    The control section  11  has a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). 
         [0111]    The control section  11  totally controls a performance of the projection device  10  in accordance with the program memorized in advance by use of the RAM as a working memory. 
         [0112]    Furthermore, the control section  11  has an interface (not shown) to external information equipment and can road image data from, for example, a personal computer. 
         [0113]    And the control section  11  processes the loaded image data, and generates the image generation data adapted to drive the image generator  16 . 
         [0114]    The image generation data is inputted to a drive signal generator  18 , the drive signal generator  18  generates a drive signal based on the image generation data, and the drive signal outputted to the image generator  16 . 
         [0115]    Moreover, the control section  11  controls the lighting-up of the light sources  2 ,  3 , and the rotation of the drive parts  2   f ,  2   n.    
         [0116]    Hereinafter, an embodiment of controlling by the control section  11  will be described with reference to  FIG. 6 . 
         [0117]      FIG. 6(   a ) illustrates a formation time T of the Nth frame of images (e.g., T= 1/30 sec) corresponding to the rotational angle position of the reflection-transmission wheel  2   b , for example, by dividing the time T into five time period. In  FIG. 6 , the time periods are indicated by the numeral a to e, and the light fluxes irradiates each time periods a to e are supposed to be Rn (red), Gn (green), Bn (blue), Yn (yellow), Mn (magenta). 
         [0118]      FIG. 6(   b ) illustrates on/off timing of the light sources  2 ,  3 , and reflection/transmission timing of the reflection-transmission wheel to each time periods a to e. In the time period a, i.e. the rotational angle position of the region boundary  2   r   2  is within the range of 0 to 90 degrees, the light-path of the first illumination optical system  1 A is in the transmission region  2   q , when the light source  2  is turned off and the light source  3  is turned on by the control section  11 , the image generator  16  is irradiated with the red light (Rn) by the second illumination optical system  1 B. 
         [0119]    In the time period b, i.e. the rotational angle position of the region boundary  2   r   2  is within the range of 90 to 180 degrees, when the light source  2  is turned on and the light source  3  is turned off by the control section  11 , and the control section  11  controls the rotational angle position of the reflection-transmission wheel  2   b  is controlled by the control section  11  so that the transmission region  2   q  is in the light-path of the first illumination optical system  1 A the image generator  16  is irradiated with the green light (Gn). 
         [0120]    In the time period c, i.e. the rotational angle position of the region boundary  2   r   2  is within the range of 180 to 225 degrees, when the light source  2  is turned on and the light source  3  is turned off by the control section  11 , and the rotational angle position of the reflection-transmission wheel  2   b  is controlled by the control section  11  so that the reflection region  2   p  is in the light-path of the first illumination optical system  1 A in synchronization with the lighting timing of the light sources, the image generator  16  is irradiated with the blue light (Bn). 
         [0121]    In the time period d, i.e. the rotational angle position of the region boundary  2   r   2  is within the range of 225 to 270 degrees, when the light source  2 ,  3  are turned on at the same time by the control section  11 , and the rotational angle position of the reflection-transmission wheel  2   b  is controlled by the control section  11  so that the reflection region  2   p  is in the light-path of the first illumination optical system  1 A, the image generator  16  is irradiated with the magenta light (Mn) by the principle of the additive color system since the blue light (Bn) and the red light (Rn) are emitted from the illumination optical system  1  at the same time. 
         [0122]    In the time period e, i.e. the rotational angle position of the region boundary  2   r   2  is within the range of 270 to 360 degrees, when the light source  2 ,  3  are turned on at the same time by the control section  11 , and the rotational angle position of the reflection-transmission wheel  2   b  is controlled by the control section  11  so that the transmission region  2   q  is in the light-path of the first illumination optical system  1 A, the image generator  16  is irradiated with the yellow light (Yn) by the principle of the additive color system since the green light (Gn) and the red light (Rn) are emitted from the illumination optical system  1  at the same time. 
         [0123]    Thus, according to the second embodiment, the full-color images can be generated and the gradation control can be achieved by two-position controlling of the irradiation timing of each light of red, green, blue, magenta, and yellow and the angle of each DMD by use of the persistence of vision, since the image generator  16  can be irradiated with the each colored light of red, green, blue, magenta, and yellow, within each time period, I.e. one of a time frame divided by five. 
         [0124]    Note that, in this embodiment, the dimension of the light-path of the first illumination optical system  1 A, i.e. the dimension of the spot region, is ignored, and only the rotational angle position of the region boundary  2   r   2  is described for the convenience of description. However, it is possible to relate 60 degrees of the rotation angular range of the reflection-transmission wheel  2   b  to each color, and to use rest of 60-digree angle where the color mixture is generates, i.e. both side of 30 degrees straddling the boundary, for white light with both the light source  2  and  3  turned on. 
         [0125]    Furthermore, on/off timing of the light source  2 ,  3  and the color of light irradiating the image generator  16  are illustrated in  FIG. 4  for ease of comprehension. 
         [0126]    According to the second embodiment, the reflection light-path from the reflection region  2   p  of the reflection-transmission wheel  2   b  returns the same route since the disk-shaped substrate  2   g  of the fluorescent wheel  2   e  is made of a reflection material. Therefore, the illumination optical system  1  can be downsized. 
       (Detailed Description of the Controlling of the Rotational Angle Position of the Reflection-Transmission Wheel  2   b  by the Control Section  11 ) 
       [0127]    The reflection-transmission wheel  2   b  is rotated on the rotating shaft  2   m  so as to traverse the light-path from the first illumination optical system  1 A as shown in  FIG. 7 . 
         [0128]    Note that, a spot region  2   s , which has the same dimension to the light-path of the illumination optical system, is indicated in  FIG. 7  by dashed line in place of the light-path of the illumination optical system  1  for the convenience of description. 
         [0129]    The region boundary  2   r   1 ,  2   r   2  between the reflection region  2   p  and the transmission region  2   q  traverses the spot region  2   s  once every 1 round. 
         [0130]    Furthermore, the rotational angle positions in every rotation of the reflection-transmission wheel  2   b  are indicated in  FIG. 7  with appropriate angles in clockwise direction from horizontal line (0 degrees) as a reference position, for the convenience of description. 
         [0131]    In  FIG. 7 , two tangent lines extending in a radial direction from the center of the rotating shaft  2   m  and circumscribing on a circle of the spot region  2   s  are indicated as the reference numbers  2   r   1 ′,  2   r   2 ′. 
         [0132]    The angle θ formed by the two tangent lines  2   r   1 ′,  2   r   2 ′ is dependent on a radius of the spot region  2   s  and the distance from the center of the rotating shaft  2   m  to the center of the spot region  2   s  (the optical axis O 1 ). 
         [0133]    Here, the angle θ is, for example, 30 degrees. When one of the region boundary  2   r   1  or the region boundary  2   r   2  is in a fun-shaped region a enclosed by the two tangent lines  2   r   1 ′,  2   r   2 ′ and an arc and the light source  2  is turned on, the light in the wavelength λA (blue) transmits the transmission region  2   q  and is reflected by the reflection region  2   p.    
         [0134]    Thus, the light with the color mixture of the light in the wavelength λA (blue) reflected by the reflection region  2   p  and the dichroic mirror  3   b , and the light in the wavelength λB (green) generated by being reflected by total reflection mirror  2   c  after passing through the transmission region  2   q  and led to the fluorescent wheel  2   e , can be obtained. 
       (Description of a Block Diagram of a Specific Control by the Control Section  11 ) 
       [0135]      FIG. 8  is a block diagram illustrating the configuration of a control section. As noted earlier, the control section  11  has the CPU, the ROM, and the RAM, and totally controls the performance of the projection device  10  in accordance with the program memorized in advance by use of the RAM as the working memory. 
         [0136]    The control section  11  has a wheel phase signal setup circuit  11   a , an LD driver  11   b , an LD drive circuit  11   c , and an image generator control circuit  11   d  besides the circuit elements described above. The wheel phase signal setup circuit  11   a  sets up the wheel phase by obtaining the rotational angle position by the sensor Se described below. 
         [0137]    The control section  11  switches the wheel phase from “1” to “0” as shown in  FIG. 10  by the wheel phase signal setup circuit  11   a  when the region boundary  2   r   1  (or region boundary  2   r   2 ) overlaps with one of a tangent line  2   r   2 ′ circumscribed on a circle of the spot region  2   s  as shown in  FIG. 9A , and switches the wheel phase from “0” to “1” as shown in  FIG. 10  by the wheel phase signal setup circuit  11   a  when the region boundary  2   r   1  (or region boundary  2   r   2 ) overlaps with another tangent line  2   r   1 ′ circumscribed on the circle of the spot region  2   s  as shown in  FIG. 9B . 
         [0138]    The wheel phase signal setup circuit  11   a  turns on the LD drive circuit  11   c  and the image generator control circuit  11   d  at least while the time t 1 , the time from the point that the wheel phase is changed from “1” to “0” to the point that the wheel phase is changed from “0” to “1”. 
         [0139]    By the LD driver  11   b , the LD drive circuit  11   c  is driven and at least the light source  2  is turned on while the time t 1  from the point that the wheel phase is changed from “1” to “0” to the point that the wheel phase is changed from “0” to “1” as shown in  FIG. 10 . 
         [0140]    Furthermore, the image generator control circuit  11   d  turns on the image generator  16  while the wheel phase is in “0”. Thereby, a cyan light generated by mixture of blue light and green light is projected to the screen. 
         [0141]    For example, as shown in  FIG. 10(   c ) simplistically, when the light source  2  is turned on, the green fluorescence of constant intensity is emitted from the projection device  10  until just before that the region boundary  2   r   1  is circumscribed on the spot region  2   s . Then, the green fluorescence is decreased while the blue excitation light is increased by the region boundary  2   r   1  passing through the spot region  2   s , and when the time t 1  is elapsed, becomes the blue light of constant intensity. 
         [0142]    Note that, the angle θ is described as 30 degrees in this embodiment, but not limited to the angle θ=30, since the angle θ is dependent on the radius of the spot region  2   s  and the distance from the center of the rotating shaft  2   m  to the center of the spot region  2   s  (the optical axis O 1 ). 
       (An Example of the Coordination of a Creation Time of the Cyan Light) 
       [0143]      FIG. 11 ,  12  illustrate the coordination of a creation time of the cyan light by adjusting the dimension of the spot region  2   s.    
         [0144]      FIG. 11A , B are same to  FIG. 9A , B and reposted for reference, and FIG.  11 C,D illustrate the angle θ (=30 degrees) formed by the tangent lines  2   r   1 ′,  2   r   2 ′ on the spot region  2   s  are changed to 2θ (=60 degrees). 
         [0145]    Thus, when the angle θ formed by the tangent lines  2   r   1 ′,  2   r   2 ′of the spot region  2   s  is doubled, and it is assumed that the number of rotations of the reflection-transmission wheel  2   b  is constant, the time t 1 , where the wheel phase is “0”, can be doubled as shown in  FIG. 12(   b ) compared to  FIG. 12(   a ). Thereby, the time t 1  to emits the cyan light as shown in  FIG. 12(   d ) compared to  FIG. 12(   c ). 
         [0146]    The dimension of the spot region  2   s  can be adjusted by moving the coupling lens  2   a  back and forth in an optical axis direction by use of a drive mechanism, or adjusting the rotating speed of the reflection-transmission wheel  2   b . Note that, these operations can be operated manually by button with watching the projected images. 
       (Another Example of the Coordination of a Creation Time of the Cyan Light) 
       [0147]      FIG. 13 ,  14  illustrate another example of the coordination of a creation time of the cyan light by adjusting the dimension of the reflection region  2   p.    
         [0148]      FIG. 13A , B are same to  FIG. 9A , B and reposted for reference, and  FIG. 13C  to (e) illustrate the reflection-transmission wheel  2   b  wherein ⅓ angle region in the forward part of the reflection region  2   p  in rotational direction of the reflection-transmission wheel  2   b  is a semi-transmissive region  2   p   0  (beam splitter region), while ⅔ angle region the backward part in rotational direction is a total reflection region  2   p   i . 
         [0149]    The reflection rate of the total reflection region  2   p   1  is 100%, and the reflection rate of the semi-transmissive region is settable conveniently. In this example, as shown in  FIG. 13C , the cyan light is generated by the green fluorescence generated by the excitation light transmitted the semi-transmissive region  2   p   0  and the blue excitation light reflected by the semi-transmissive region,  2   p   0  while the time from the point that the region boundary  2   r   1  of the semi-transmissive region  2   p   0  contacts the tangent line  2   r   2 ′ to the point that the region boundary  2   pr   1  between the semi-transmissive region  2   p   0  and the total reflection region  2   p   1  contacts the tangent line  2   r   2 ′. 
         [0150]    As shown in  FIG. 13D , the cyan light is generated by the green fluorescence generated by the excitation light transmitted the semi-transmissive region  2   p   0  and the blue excitation light reflected by the total reflection region  2   p   1  until the region boundary  2   pr   1  between the semi-transmissive region  2   p   0  and the total reflection region  2   p   1  contacts the tangent line  2   r   1 ′. 
         [0151]    Next, the blue excitation light is emitted since the excitation light is reflected by the total reflection region  2   p   1  until the region boundary  2   r   2  of the total reflection region  2   p   1  (the region boundary of the reflection region  2   p ) contacts the tangent line  2   r   2 ′. Then, when the region boundary  2   r   2  of the total reflection region  2   p   1  (the region boundary of the reflection region  2   p ) contacts the tangent line  2   r   2 ′, the cyan light is generated by the excitation light reflected by the reflection region  2   p  and the green light generated by the excitation light transmits the transmission region  2   q.    
         [0152]    Therefore, as shown in  FIG. 14 , the creation time t 1  of the cyan C can be adjusted by forming the beam splitter region  2   p   0  on the reflection region  2   p   1 . 
       (Generation of the White Light by the Light Source  2  and the Light Source  3 ) 
       [0153]    In the embodiments described above, it is described that to generate the cyan light while the region boundary  2   r   1 ,  2   r   2  traverses the spot region  2   s . However, if he light source device is configured to control to turn on both the light source  2  and the light source  3  at the same time, the light source device can emits tricolored light of blue, green, and red at the same time, i.e. white light, and highly intensity images can be obtained as shown in  FIG. 15 ,  FIG. 16 . 
         [0154]      FIGS. 15A , B are same to  FIGS. 9A , B and reposted for reference, and  FIG. 16(   a ) to ( d ) simplistically illustrate that the white light W can be obtained in the time between yellow Y and magenta M. 
       (An Example of a Sensor Detecting the Rotational Angle Position of Reflection-Transmission Wheel  2   b  (a Rotation Angle Detector or a Boundary Region Detector)) 
       [0155]    A ring-shaped rotational angle position detecting pattern Sp is formed around the rotating shaft  2   m  on the reflection-transmission wheel  2   b  as shown in  FIG. 17  simplistically. An image sensor Sx forming a part of an encoder is provided at the opposed position of the rotational angle position detecting pattern Sp. And, the rotational angle position detecting pattern Sp is received by the image sensor Sx when passing through the spot region  2   s . The image sensor Sx and the rotational angle position detecting pattern Sp configure the sensor Se. 
         [0156]    The image sensor Sx outputs the image signal to the CPU. The CPU can detect the rotational angle position of the reflection-transmission wheel  2   b  since the rotational angle position detecting pattern Sp correspond one-to-one with the rotational angle position. 
         [0157]    Note that, a potentiometer that the resistance value varies in proportion to the rotation angle can be used in place of the sensor Se formed of the rotational angle position detecting pattern Sp and the image sensor Sx. 
         [0158]    An acceleration sensor can be used to detect the rotational angle position of the reflection-transmission wheel  2   b . As shown in  FIG. 18  simplistically, acceleration is “0G” when the acceleration sensor (not shown) is in a horizontal position, and the acceleration is “1G” when the acceleration sensor is in a vertical position. There is a sinusoidal relationship between the angle θx and the acceleration. 
         [0159]    Thus, the rotational angle position of the reflection-transmission wheel  2   b  can be detected by converting a gravity acceleration G detected by the acceleration sensor provided on the rotating shaft  2   m  of the reflection-transmission wheel  2   b  into the rotational angle position by a sine function. Note that, detection of the rotational angle position is not limited to this. 
         [0160]    In the second embodiments, the on/off control of the light source  2  and  3  when the region boundary  2   r   1 ,  2   r   2  between the transmission region  2   q  and the reflection region  2   p  traverses the spot region is described above, but also the on/off control of the light source  2  and  3  in the rest of the time is obviously possible. 
       Third Embodiment 
       [0161]    In the third embodiment, as shown in  FIG. 19 , light sources emitting light in the same wavelength λA (e.g. a blue laser diode) are used as both of the light source  2  of the first illumination optical system  1 A and the light source  3  of the second illumination optical system  1 B. The configuration of the coupling lens  3   a , the reflection-transmission wheel  2   b , the drive part  2   n , and the rotating shaft  2   m  provided to the first illumination optical system  1 A and the configuration of the coupling lens  3   a  of the second illumination optical system  1 B are same to the first embodiment. 
         [0162]    The fluorescent wheel  2   e  as the second fluorescent wheel is provided in the transmission light-path of the first illumination optical system  1 A. A pair of collecting elements  2   i  are provided on both side of the disk-shaped substrate  2   g  of the fluorescent wheel  2   e . In this embodiment, the disk-shaped substrate  2   g  of the fluorescent wheel  2   e  is formed of a transmissive material. 
         [0163]    The fluorescence property of the fluorescent body  2   h  of the fluorescent wheel  2   e  is same as the first embodiment, i.e., the fluorescent body  2   h  is excited by the light in the wavelength λA and emits the light in a wavelength λB (green). The light in the wavelength λB is collected by the collecting element  2   i  after transmitting the disk-shaped substrate  2   g  and reflected by the total reflection mirror  2   c  to the dichroic mirror  3   c.    
         [0164]    The fluorescent wheel  2   e ′ as the first fluorescent wheel is provided in the reflection light-path of the first illumination optical system  1 A. The disk-shaped substrate  2   g ′ of the fluorescent wheel  2   e ′ is formed of the transmissive material as with the disk-shaped substrate  2   g  of the fluorescent wheel  2   e.    
         [0165]    A pair of collecting elements  2   i ′ are provided on both side of the disk-shaped substrate  2   g ′. A ring-shaped fluorescent body  2   hn  is provided on the disk-shaped substrate  2   g ′, and the fluorescent body  2   hn  is excited by the light in the wavelength λA and emits the light in a wavelength λC (red). The light in the wavelength λC (red; 620 nm to 750 nm) is collected by the collecting element  2   i ′ after transmitting the disk-shaped substrate  2   g ′ and led to the dichroic mirror  3   b.    
         [0166]    The dichroic mirror  3   b  has a function that transmits the light in the wavelength λA (blue; 400 nm to 450 nm) and reflects the wavelength λC (red; 620 nm to 750 nm). The light in the wavelength λC is reflected by the dichroic mirror  3   b  and led to the dichroic mirror  3   c . The dichroic mirror  3   c  has a function that transmits the light in the wavelength λA and the light in the wavelength λC and reflects the light in the wavelength λB. 
         [0167]    In this embodiment, the light in the wavelength λA from the light source  3  of the second illumination optical system  1 B is emitted from the illumination optical system  1  after transmitting the dichroic mirror  3   b  and the dichroic mirror  3   c.    
         [0168]    When the reflection region  2   p  of the reflection-transmission wheel  2   b  is in the light-path of the first illumination optical system  1 A, the light in the wavelength λA from the light source  2  is reflected by the reflection region  2   p  and led to the fluorescent wheel  2   e ′ provided in the reflection light-path. Then, the fluorescence in the wavelength λC is generated by the light in the wavelength λA as the excitation light, reflected by the dichroic mirror  3   b , transmits the dichroic mirror  3   c , and emitted from the illumination optical system  1 . 
         [0169]    When the transmission region  2   q  of the reflection-transmission wheel  2   b  is in the light-path of the first illumination optical system  1 A, the light in the wavelength λA from the light source  2  transmits the transmission region  2   q  and led to the fluorescent wheel  2   e  provided on the transmission light-path. The fluorescence in the wavelength λB is generated by the light in the wavelength λA as the excitation light, reflected by the total reflection mirror  2   c  and the dichroic mirror  3   c , and emitted from the illumination optical system  1 . 
       (An Example of the Irradiation Timing to the Image Generator  16 ) 
       [0170]      FIG. 20  simplistically illustrates an example of a relationship among emission timing of the RGB light, on/off timing of the light source  2  and  3 , and reflection/transmission timing of the reflection-transmission wheel, of the Nth frame of images. 
         [0171]    Here, the creation time of the frame of images is divided into 3 time period, and the time periods are referred by the reference numbers a to c. In the time period a, i.e. the rotational angle position of the region boundary  2   r   2  is within the range of 0 to 90 degrees, the light source  2  is turned on and the light source  3  is turned off by the control section  11 , and the transmission region  2   q  is put in the light-path of the first illumination optical system  1 A. Thereby, the image generator  16  is irradiated with the green light (Gn) in the wavelength λB. 
         [0172]    In the time period b, i.e. the rotational angle position of the region boundary  2   r   2  is within the range of 180 to 270 degrees, the light source  2  is turned on and the light source  3  is turned off by the control section  11 , and the reflection region  2   p  of the reflection-transmission wheel  2   b  is put in the light-path of the first illumination optical system  1 A. Thereby, the image generator  16  is irradiated with the red light (Rn) in the wavelength λC. 
         [0173]    In the time period c, i.e. the rotational angle position of the region boundary  2   r   2  is within the range of 270 to 360 degrees, the light source  2  is turned off and the light source  3  is turned on by the control section  11 , and the transmission region  2   q  of the reflection-transmission wheel  2   b  is put in the light-path of the first illumination optical system  1 A. Thereby, the image generator  16  is irradiated with the blue light (Bn) in the wavelength λA. 
         [0174]    Thus, according to this embodiment, each color of RGB can irradiates the image generator  16  in a time frame of the image, and the projection of the full-color images and the white rite become available by use of persistence of vision. 
         [0175]    A color tone can be varied by adjusting or changing the length of the time period a, b, and c. For example, to make the projection image being tinged with red by lengthening the time period a in one frame. Furthermore, color temperature can be changed by adjusting or changing the time periods a, b, and c frame by frame. 
         [0176]    Also, in this Embodiment, the brightness of projected image can be improved while the region boundary  2   r   1 ,  2   r   2  between the transmission region  2   q  and the reflection region  2   p  of the reflection-transmission wheel  2   b  traverses the spot region  2   s.    
       (Other Example of the Emission Timing to the Image Generator  16 ) 
       [0177]      FIG. 21  simplistically illustrates other example of a relationship among emission timing of the RGB light, on/off timing of the light source  2  and  3 , and reflection/transmission timing of the reflection-transmission wheel  2   b , of the Nth frame of images. 
         [0178]    In the other example, the Nth time period a is divided into the time period a 1  and the time period a 2 , while the Nth time period b is divided into the time period b 1  and the time period b 2 . In the time period a 1 , i.e. the rotational angle position of the region boundary  2   r   2  is within the range of 0 to 90 degrees, the light source  2  is turned on and the light source  3  is turned off by the control section  11 . Furthermore, the transmission region  2   q  is put in the light-path of the first illumination optical system  1 A. Thereby, the image generator  16  is irradiated with the green light (Gn) in the wavelength λB. 
         [0179]    In the time period a 2 , i.e. the rotational angle position of the region boundary  2   r   2  is within the range of 90 to 180 degrees, the light source  2  and the light source  3  is turned on in the same time, and the transmission region  2   q  is put in the light-path of the first illumination optical system  1 A. Thereby, the cyan illumination light is generated by mixture of the green light in the wavelength λB and the blue light in the wavelength λA, and the image generator  16  is irradiated with the cyan illumination light. 
         [0180]    In the time period b 1 , i.e. the rotational angle position of the region boundary  2   r   2  is within the range of 180 to 225 degrees, the light source  2  is turned on and the light source  3  is turned off by the control section  11 . Furthermore, the reflection region  2   p  of the reflection-transmission wheel  2   b  is put in the light-path of the first illumination optical system  1 A. Thereby, the image generator  16  is irradiated with the red light (Rn) in the wavelength λC. 
         [0181]    In the time period b 2 , i.e. the rotational angle position of the region boundary  2   r   2  is within the range of 225 to 270 degrees, the light source  2  is turned on and the light source  3  is turned off by the control section  11 . Furthermore, the reflection region  2   p  of the reflection-transmission wheel  2   b  is put in the light-path of the first illumination optical system  1 A. Thereby, the magenta (Mn) illumination light is generated by mixture of the red (Rn) light in the wavelength λC and the blue light (Bn) in the wavelength λA, and the image generator  16  is irradiated with the magenta illumination light. 
         [0182]    In the time period c, i.e. the rotational angle position of the region boundary  2   r   2  is within the range of 270 to 360 degrees, the light source  2  is turned off and the light source  3  is turned on, and the transmission region  2   q  of the reflection-transmission wheel  2   b  is put in the light-path of the first illumination optical system  1 A. Thereby, the image generator  16  is irradiated with the blue light (Bn) in the wavelength λA. Also in this case, the occurrence of color mixture is prevented while the brightness of projected image can be improved. Therefore, a brighter projected image can be generated. 
       Fourth Embodiment 
       [0183]    In this fourth embodiment, as shown in  FIG. 22 ,  FIG. 23 , a collecting element  2   w  is provided in the light-path of the first illumination optical system  1 A in addition to the third embodiment, the coupling lens  2   x  is provided in the transmission light-path, and the coupling lens  2   x ′ is provided in the reflection light-path. The collecting element  2   w  and the coupling lens  2   x ,  2   x ′ configure the second optical element together. 
         [0184]    According to the fourth embodiment, as shown in  FIG. 23 , the light in the wavelength λA emitted from the light source  2  is collected by the coupling lens  2   a , led to the collecting element  2   w  as a parallel beam, and converged by the collecting element  2   w , and led to the reflection-transmission wheel  2   b.    
         [0185]    When the reflection region  2   p  is in the light-path of the first illumination optical system  1 A, the converged light in the wavelength λA is reflected by the reflection region  2   p , led to the coupling lens  2   x ′, led to the collecting element  2   i ′ by the coupling lens  2   x ′ as the parallel beam, converged by the collecting element  2   i ′, and irradiates the fluorescent body  2   hn.    
         [0186]    When the transmission region  2   q  is in the light-path of the first illumination optical system  1 A, the converged light in the wavelength λA transmits the transmission region  2   q  and is led to the coupling lens  2   x , led to the collecting element  2   i  by the coupling lens  2   x  as the parallel beam, converged by the collecting element  2   i , and irradiates the fluorescent body  2   h.    
         [0187]    In the fourth embodiment, as shown in  FIG. 24 , the dimension of the spot region  2   s ′ can be reduced in size compared to the size of the spot region  2   s  of the first illumination optical system  1 A in the third embodiment, since a beam in the wavelength λA irradiates the reflection-transmission wheel  2   b  after being converged. 
         [0188]    Thus, the time that the region boundary  2   r   1 ,  2   r   2  between the transmission region  2   q  and the reflection region  2   p  of the reflection-transmission wheel  2   b  passing through the spot region  2   s ′ can be shorten. 
         [0189]    Therefore, according to the fourth embodiment, the color reproducibility and the brightness of the images can be improved since the creation time of the mixed color light can be adjusted by changing the dimension of the spot region  2   s.    
         [0190]    Detailed descriptions are omitted since the other of the configuration and functions are similar to that in the third embodiment. 
       Fifth Embodiment 
       [0191]    In this embodiment, the number of the light source of the illumination optical system  1  is one. For this light source, the light source emitting the light in the wavelength λA (blue) as with the first embodiment is used, and referred to as the same reference number  2  as shown in  FIG. 25 . 
         [0192]    As shown in  FIG. 26 , the reflection-transmission wheel  2   b  is formed of the reflection region  2   p  and the transmission region  2   q  being arranged symmetrically with respect to a straight line passing through the center of the rotating shaft  2   m . The rest of the configuration and the total reflection mirror  2   c  will be described with the same reference numbers as shown in  FIG. 1 , since they are similar to the first embodiment. 
         [0193]    In  FIG. 26 , the straight line passing through the center of the rotating shaft  2   m  is divided into two lines at the rotating shaft  2   m , and one of them is referred as the radial region boundary  2   r   1 , and another one is referred as the radial region boundary  2   r   2 . 
         [0194]    As shown in  FIG. 27 , the ring-shaped fluorescent body  2   h  of the fluorescent wheel  2   e  is formed of a semicircular fluorescent body  2   h ′ emitting the fluorescence in the wavelength λB (green) and a semicircular fluorescent body  2   h ″ emitting the fluorescence in the wavelength λC (red) different from the wavelength λB. In this embodiment, the disk-shaped substrate  2   g  is divided into two parts, and semicircular fluorescent bodies  2   h ′,  2   h ″ are formed on the disk-shaped substrate  2   g , but the configuration of the fluorescent body  2   h  is not limited thereto. 
         [0195]    In  FIG. 27 , a straight line passing through the center of the rotating shaft  2   j  and forming the boundary between the semicircular fluorescent body  2   h ′ and the semicircular fluorescent body  2   h ″ is divided into two lines at the rotating shaft  2   j , one of the lines is referred to a radial region boundary  2   r   3  and another one of the lines is referred to a radial region boundary  2   r   4 . 
         [0196]    The dichroic mirror  3   b  is provided in the reflection light-path of the reflection-transmission wheel  2   b , and the dichroic mirror  3   c  is provided in the transmission light-path. The dichroic mirror  3   b  has a function that transmits the light in the wavelength λA, and reflects the light in the wavelength λB, λC. 
         [0197]    The drive part  2   f  is formed of, for example, a stepping motor. The disk-shaped substrate  2   g  is rotationally driven on the rotating shaft  2   j  based on a predetermined rotational angle position of the semicircular fluorescent body  2   h′, h ″. The blue light in the wavelength λA irradiates the reflection-transmission wheel  2   b  when the light source  2  is turned on. 
         [0198]    When the transmission region  2   q  is in the light-path of the illumination optical system  1 , the blue light in the wavelength λA is led to the transmission region  2   q  by the coupling lens  2   a  as a parallel beam and transmits the transmission region  2   q , reflected by the total reflection mirror  2   c , led to the dichroic mirror  3   c , reflected by the dichroic mirror  3   c  and emitted from the illumination optical system  1 . 
         [0199]    When the reflection region  2   p  is in the light-path of the illumination optical system  1 , the blue light in the wavelength λA is led to the reflection region  2   p  by the coupling lens  2   a  as a parallel beam, reflected by the reflection region  2   p , led to the collecting element  2   i  after transmitting the dichroic mirror  3   c , converged by the collecting element  2   i , and irradiates the fluorescent wheel  2   e.    
         [0200]    When the semicircular fluorescent body  2   h ′ of the fluorescent body  2   h  is irradiated with the blue light in the wavelength λA converged, the fluorescence in the wavelength λB (green) is generated by the blue light as the excitation light, and when the semicircular fluorescent body  2   h ″ is irradiated with the blue light in the wavelength λA converged, the fluorescence in the wavelength λC (red) is generated by the blue light as the excitation light. 
         [0201]    The fluorescence in the wavelength λB or λC is collected by the collecting element  2   i  and led to the dichroic mirror  3   b , reflected by the dichroic mirror  3   b , and emitted from the illumination optical system  1  after transmitting the dichroic mirror  3   c.    
       (An Example of Irradiation Timing to the Image Generator  16 ) 
       [0202]      FIG. 28  simplistically illustrates an example of a relationship among the irradiation timing of the RGB light, the reflection/transmission timing of the reflection-transmission wheel  2   b , and the fluorescent wheel  2   e  of Nth image frame in the fifth embodiment. 
         [0203]    An Nth time frame of images is divided into four time period a, b, c and d. In the time period a, i.e. the rotational angle position of the region boundary  2   r   2  is within the range of 45 to 67.5 degrees (the rotational angle position of the region boundary  2   r   3  is within the range of 0 to 90 degrees), the reflection region  2   p  is put in the light-path of the first illumination optical system  1 A by the control section  11 . Furthermore, the rotational angle position of the fluorescent wheel  2   e  is controlled by the control section  11  so that the semicircular fluorescent body  2   h ′ of the fluorescent wheel  2   e  is irradiated with the light in the wavelength λA. 
         [0204]    Thereby, the green fluorescence (Gn) in the wavelength λB is generated and emitted from the illumination optical system  1  via the dichroic mirror  3   b ,  3   c , and irradiates the image generator  16 . 
         [0205]    In the time period b, i.e. the rotational angle position of the region boundary  2   r   2  is within the range of 67.5 to 90 degrees (the rotational angle position of the region boundary  2   r   3  of the fluorescent wheel  2   e  is within the range of 90 to 180 degrees), the reflection region  2   p  of the reflection-transmission wheel  2   b  is put in the light-path of the first illumination optical system  1 A by the control section  11 . Furthermore, the rotational angle position of the fluorescent wheel  2   e  is controlled by the control section  11  so that the semicircular fluorescent body  2   h ″ of the fluorescent wheel  2   e  is irradiated with the light in the wavelength λA. 
         [0206]    Thereby, the red fluorescence (Rn) in the wavelength λC is generated and emitted from the illumination optical system  1  via the dichroic mirror  3   b ,  3   c , and irradiates the image generator  16 . 
         [0207]    In the time period c, d, i.e. the rotational angle position of the region boundary  2   r   2  is within the range of 90 to 135 degrees (the rotational angle position of the region boundary  2   r   3  of the fluorescent wheel  2   e  is within the range of 180 to 360 degrees), the transmission region  2   q  of the reflection-transmission wheel  2   b  is put in the light-path of the first illumination optical system  1 A by the control section  11 . The blue light (Bn) in the wavelength λA transmits the transmission region  2   q , and is reflected by the total reflection mirror  2   c  and the dichroic mirror  3   c , and emitted from the illumination optical system  1 . At that time, the rotational angle position of the fluorescent wheel  2   e  is arbitrarily-selected. 
         [0208]    Also, in the fifth embodiment, the full-color images can be generated and the white light can be projected as is the case in the first, third and fourth embodiments, since the image generator  16  can be irradiated with the light of the RGB color in a time frame. Furthermore, as is the case in the third embodiment, the color tone and the color temperature can be varied. A detailed description of the projection device is omitted since the projection device identical to the second embodiment is applicable except optical components of the illumination optical system  1 . 
         [0209]    According to the fifth embodiment, the illumination optical system  1  can be downsized, and the production cost can be reduced, since the number of the optical element of the illumination optical system  1  for the light source can be reduced to be one. 
       (An Example of Controlling in High-Intensity) 
       [0210]      FIG. 29A  to  FIG. 29G  illustrates a relationship between the rotational angle position of the reflection-transmission wheel and the spot region  2   s .  FIG. 30A  to  FIG. 30G  illustrate a relationship between the rotational angle position of the fluorescent wheel  2   e  and the spot region  2   s″.    
         [0211]    Note that, in this embodiment, the rotational angle position detecting part of the fluorescent wheel  2   e  is provided. 
         [0212]    In this embodiment, it is assumed that the light source  2  is turned on when the boundary region  2   r   2  traverses the spot region  2   s , whereas the light source  2  is turned on/off when the boundary region  2   r   1 ,  2   r   2  traverses the spot region  2   s  in the first embodiment. 
         [0213]    As shown in  FIG. 26 , when the boundary region  2   r   2  of the reflection-transmission wheel  2   b  traverses the spot region  2   s , a half of the light in the wavelength λA transmits the transmission region  2   q , and the other half is reflected by the reflection region  2   p  and led to the fluorescent wheel  2   e  through the reflection light-path. 
         [0214]    As shown in  FIG. 27 , when the boundary region  2   r   3  of the fluorescent wheel  2   e  traverses the spot region  2   s ″, the light in the wavelength λA from the light source  2  as the excitation light excites the semicircular fluorescent body  2   h ′ and generates the light in the wavelength λB, simultaneously excites the semicircular fluorescent body  2   h ″ and generates the light in the wavelength λC. The fluorescence is emitted from the illumination optical system  1  via the collecting element  2   i , the dichroic mirror  3   b , and  3   c . Thus, the mixed colored light can be generated. 
         [0215]    Thus, the control section  11  judges the rotational angle position of the reflection-transmission wheel  2   b  and the rotational angle position of the fluorescent wheel  2   e , and controls the lighting of the light source  2 . The angle θ formed by the two tangent lines  2   r   1 ′,  2   r   2 ′ extended in the radial direction from the center of the rotating shaft  2   m  and that contacts the spot region  2   s  is dependent on a radius of the spot region  2   s , and the distance from the center of the rotating shaft  2   m  to the center of the spot region  2   s  (the optical axis O 1 ). 
         [0216]    Here, the angle θ is, for example, 90 degrees. When the region boundary  2   r   1 ,  2   r   2  of the reflection-transmission wheel  2   b  is in a fun-shaped region β enclosed by the two tangent lines  2   r   1 ′,  2   r   2 ′ and an arc, and the light source  2  is turned on, the light in the wavelength λA (blue) transmits the transmission region  2   q  and is reflected by the reflection region  2   p  at the same time. 
         [0217]    The color mixture is also generated when the region boundary  2   r   3 ,  2   r   4  traverses the spot region  2   s ″. Also, as regarding the fluorescent wheel  2   e , the angle θ″ formed by the two tangent lines  2   r   1 ″,  2   r   2 ″ extended in the radial direction from the center of the rotating shaft  2   j  and contacts the spot region  2   s ″ is dependent on the radius of the spot region  2   s ″ and the distance from the center of the rotating shaft  2   j  to the center of the spot region  2   s″.    
         [0218]    Here, it is assumed that the fluorescent wheel  2   e  rotates in rotating speed of 4 times of the reflection-transmission wheel  2   b , and the angle θ″ is 60 degrees. Note that, the angle θ′, θ″ is indicated specifically just for convenience of description, and not limited to the angle θ′, θ″. 
         [0219]    As shown in  FIG. 29A , it is assumed that the reflection-transmission wheel  2   b  starts rotation when the rotational angle position of the region boundary  2   r   2  is within the 45 degrees to the reference angle of 0 degrees, whereas, the fluorescent wheel  2   e  starts rotation when the region boundary  2   r   3  is in the reference angle i.e. 0 degrees as shown in  FIG. 30A . 
         [0220]      FIG. 31  illustrates a relationship among the rotational angle position of each wheel, the rotational phase of each wheels, and a color of light irradiating the image generator when the light source  2  is turned on, when the reflection-transmission wheel shown in  FIG. 26  and the fluorescent wheel shown in  FIG. 27  are used. 
         [0221]    That is to say, a relationship among the rotation angle (rotational phase) of the region boundary  2   r   2 ,  2   r   1  of the reflection-transmission wheel  2   b , the rotation angle (rotational phase) of the region boundary  2   r   3 ,  2   r   4  of the fluorescent wheel  2   e , and a color of light emitted by the illumination optical system  1  and irradiates the image generator  16  when the light source  2  is turned on is illustrated. 
         [0222]    It is shown in  FIG. 31  that the rotation angle of four revolution of the fluorescent wheel  2   e  to the rotation angle of one revolution of the reflection-transmission wheel  2   b . The rotational angle position of the reflection-transmission wheel  2   b  is shown by 15-degree scale whereas the rotational angle position of the fluorescent wheel  2   e  is shown by 60-degree scale. 
         [0223]    It is assumed that the rotational phase of the reflection-transmission wheel  2   b  is “0” when the region boundary  2   r   2 ,  2   r   1  is in the spot region  2   s  and “1” when the region boundary  2   r   2 ,  2   r   1  is out of the spot region  2   s , on the other hand, the rotational phase of the fluorescent wheel  2   e  is “0” when the region boundary  2   r   3 ,  2   r   4  is in the spot region  2   s.    
         [0224]    Hereinafter, a relationship between the rotational phases of the reflection-transmission wheel  2   b  and the fluorescent wheel  2   e , and the on-state of the light source  2  will be described in detail with reference to  FIG. 29A to 29G ,  FIG. 30A to 30G , and  FIG. 31 . It is assumed that the fluorescent wheel  2   e  rotates four revolutions per one revolution of the reflection-transmission wheel  2   b.    
         [0225]    The rotational phase of the reflection-transmission wheel  2   b  is “0” when the rotational angle position of the region boundary  2   r   2  of the reflection-transmission wheel  2   b  is within the range of 45 to 135 degrees (see  FIG. 29  A and  FIG. 29B ), since the region boundary  2   r   2  traverses the spot region  2   s . On the other hand, the rotational phase of the reflection-transmission wheel  2   b  is “1” when the rotational angle position of the region boundary  2   r   2  of the reflection-transmission wheel  2   b  is within the range of 135 to 225 degrees (see  FIG. 29B  to  FIG. 29G ), since neither of the region boundaries  2   r   1  and  2   r   2  of the reflection-transmission wheel  2   b  traverse the spot region  2   s.    
         [0226]    Light intensity of the excitation light (light B) is increased (see  FIG. 31  B 1 ) when the rotational angle position of the region boundary  2   r   2  is within the range of 45 to 135 degrees, since the spot region  2   s  relatively moves from the reflection region  2   p  to the transmission region  2   q.    
         [0227]    The light intensity of the excitation light (light B) is constant (see  FIG. 31  B 2 ) when the rotational angle position of the region boundary  2   r   2  is within the range of 135 to 225 degrees, since the spot region  2   s  is only in the transmission region  2   q.    
         [0228]    the rotational phase of the reflection-transmission wheel  2   b  is “0” when the rotational angle position of the region boundary  2   r   2  of the reflection-transmission wheel  2   b  is within the range of 225 to 315 degrees (not shown), i.e., the rotational angle position of the region boundary  2   r   1  is within the range of 45 to 135 degrees, since the region boundary  2   r   1  traverses the spot region  2   s.    
         [0229]    The light intensity of the excitation light (light B) emitted from illumination optical system  1  and irradiates the image generator  16  is increased (see the reference number B 3  in  FIG. 31 ) when the rotational angle position of the region boundary  2   r   2  is within the range of 225 to 315 degrees, since the spot region  2   s  relatively moves from the transmission region  2   q  to the reflection region  2   p.    
         [0230]    The rotational phase of the reflection-transmission wheel  2   b  is “1” when the rotational angle position of the region boundary  2   r   2  of the reflection-transmission wheel  2   b  is within the range of 315 to 45 degrees (not shown), i.e., the rotational angle position of the region boundary  2   r   1  is within the range of 135 to 225 degrees, since neither of the region boundaries  2   r   1  and  2   r   2  traverse the spot region  2   s.    
         [0231]    When the rotational angle position of the region boundary  2   r   2  is within the range of 315 to 45 degrees, the spot region  2   s  is only in the reflection region  2   p . The excitation light (light B) is not emitted by the illumination optical system  1  and does not irradiates the image generator  16  (see the reference number B 4  in  FIG. 31 ). 
         [0232]    The rotational phase of the fluorescent wheel  2   e  is “1” when the rotational angle position of the region boundary  2   r   3  of the fluorescent wheel  2   e  is within the range of 0 to 60 degrees (see  FIG. 30B  and  FIG. 30C ), since neither of the region boundaries  2   r   3 ,  2   r   4  traverse the spot region  2   s″.    
         [0233]    The green fluorescence (G light) is generated and emitted from the illumination optical system  1  and irradiates the image generator  16  (see the reference number G 1  in  FIG. 31 ) whereas red fluorescence (R light) is not generated (see the reference number R 1  in  FIG. 31 ) when the rotational angle position of the region boundary  2   r   3  is within the range of 0 to 60 degrees, since the spot region  2   s ″ is only in the semicircular fluorescent body  2   h′.    
         [0234]    The rotational phase of the fluorescent wheel  2   e  is “ 0 ” when the rotational angle position of the region boundary  2   r   3  of the fluorescent wheel  2   e  is within the range of 60 to 120 degrees (see  FIG. 30C  and  FIG. 30D ), since the region boundary  2   r   3  traverses the spot region  2   s″.    
         [0235]    The light intensity of the G light which is emitted by illumination optical system  1  and irradiates the image generator  16  is decreased (see  FIG. 31  G 2 ), and the R light which is emitted by illumination optical system  1  and irradiates the image generator  16  is increased (see  FIG. 31  R 2 ) when the rotational angle position of the region boundary  2   r   3  is within the range of 60 to 120 degrees, the spot region  2   s ″ relatively moves from the semicircular fluorescent body  2   h ′ to the semicircular fluorescent body  2   h″.    
         [0236]    The rotational phase of the fluorescent wheel  2   e  is “1” when the rotational angle position of the region boundary  2   r   3  of the fluorescent wheel  2   e  is within the range of 120 to 240 degrees (see  FIG. 30D  and  FIG. 30E ), since neither of the region boundaries  2   r   3 ,  2   r   4  traverse the spot region  2   s″.    
         [0237]    The R light which is emitted by the illumination optical system  1  and irradiates the image generator  16  is constant (see the reference number R 3  in  FIG. 31 ) if the light intensity of the excitation light reflected by the reflection region  2   p  is constant when the rotational angle position of the region boundary  2   r   3  is within the range of 120 to 240 degrees, since the spot region  2   s ″ is only in the semicircular fluorescent body  2   h ″. On the other hand, the G light is not emitted by the illumination optical system  1  and does not irradiates the image generator  16  (see  FIG. 31  G 3 ) since the spot region  2   s ″ is not in the semicircular fluorescent body  2   h′.    
         [0238]    Note that, the light intensity of the R light is not constant in practice since the light intensity of the reflected excitation light is increased or decreased while the rotational phase of the reflection-transmission wheel  2   b  is “0”. 
         [0239]    The rotational phase of the fluorescent wheel  2   e  is “0” when the rotational angle position of the region boundary  2   r   3  of the fluorescent wheel  2   e  is within the range of 245 to 300 degrees (see  FIGS. 30E ,  30 F), since the region boundary  2   r   4  traverses the spot region  2   s″.    
         [0240]    When the rotational angle position of the region boundary  2   r   3  is within the range of 240 to 300 degrees, the spot region  2   s ″ relatively moves from the semicircular fluorescent body  2   h ″ to the semicircular fluorescent body  2   h ′. The light intensity of the R light which is emitted by illumination optical system  1  and irradiates the image generator  16  is decreased (see the reference number R 4  in  FIG. 31 ), and the B light which is emitted by illumination optical system  1  and irradiates the image generator  16  is increased (see the reference number G 4  in  FIG. 31 ). 
         [0241]    The rotational phase of the fluorescent wheel  2   e  is “1” when the rotational angle position of the region boundary  2   r   3  of the fluorescent wheel  2   e  is within the range of 300 to 60 degrees (see  FIG. 30F  and  FIG. 30G ), since neither of the region boundaries  2   r   3  and  2   r   4  traverse the spot region  2   s″.    
         [0242]    Therefore, the relationship of the rotational phase of the fluorescent wheel  2   e  to the reflection-transmission wheel  2   b  in one revolution of the reflection-transmission wheel  2   b  is that illustrated in  FIG. 31 . 
         [0243]    The spot region  2   s ″ is in the semicircular fluorescent body  2   h ′ when the rotational angle position of the region boundary  2   r   3  is within the range of 300 to 60 degrees. At the time, the G light is emitted by the illumination optical system  1  and irradiates the image generator  16  (see the reference number G 5  in  FIG. 31 ) while the region boundary  2   r   3  is within the range of 300 to 0 degrees since the excitation light λA is led to the fluorescent wheel  2   e  by the reflection region  2   p.    
         [0244]    Therefore, the colors of light emitted by the illumination optical system  1  while the fluorescent wheel  2   e  rotates one revolution, equal to that the reflection-transmission wheel  2   b  rotates from the angle 45 to 135 degrees are cyan (C), white (W), magenta (M), white (W), and cyan (C). 
         [0245]    Furthermore, the color of light emitted by the illumination optical system  1  while the fluorescent wheel  2   e  rotates one revolution, equal to that the reflection-transmission wheel  2   b  rotates from the angle 135 to 225 degrees, is blue (B). 
         [0246]    Similarly, the colors of light emitted by the illumination optical system  1  while the fluorescent wheel  2   e  rotates one revolution, equal to that the reflection-transmission wheel  2   b  rotates from the angle 225 to 315 degrees, are cyan (C), white (W), magenta (M), white (W), and cyan (C). 
         [0247]    Also, the colors of light emitted by the illumination optical system  1  while the fluorescent wheel  2   e  rotates one revolution, equal to that the reflection-transmission wheel  2   b  rotates from the angle 315 to 45 degrees, are green (G), yellow (Y), red (R), yellow (Y), and green (G) since there is no B light transmitting the transmission region  2   p  in this angular range. 
         [0248]    In this embodiment, it is assumed that the fluorescent wheel  2   e  rotates in rotating speed of 4 times of the reflection-transmission wheel  2   b , but the rotating speed is not limited thereto. 
         [0249]    Since the rotational angle position of the reflection-transmission wheel  2   b  and the rotational angle position of the fluorescent wheel  2   e  can be detected by the rotational angle position detector, each colored light of red, green, blue, cyan, magenta, yellow, and white can be generated by controlling the timing of the lighting of the light source  2  and the image generator  16  (DMD), when the dimension of the spot region  2   s ″ is detected. 
         [0250]    The dimension of the spot regions  2   s ,  2   s ″ can be determined at the planning phase and memorized in the RAM or the like in the control section  11 , and additionally the varying in the dimension of the spot regions  2   s ,  2   s ″ depending on the driving of the coupling lens  2   a  in direction of the optical axis can be obtained by calculations based on the reference dimension of the spot regions  2   s ,  2   s ″ which are preset in advance. 
         [0251]    Furthermore, the relationship between the rotating speed of the fluorescent wheel  2   e  and the rotating speed of reflection-transmission wheel  2   b  can be memorized as a table. 
         [0252]    Although the present invention has been described in terms of exemplary embodiments, it is not limited thereto. It should be appreciated that variations may be made in the embodiments described by persons skilled in the art without departing from the scope of the present invention as defined by the following claims.
An illumination light source device includes a reflection-transmission wheel provided on a light-path from an excitation light source and having a transmission region that transmits an excitation light and a reflection region reflecting the excitation light, a fluorescent wheel provided on at least one of the reflection light-path and the transmission light-path and having a fluorescent body emitting fluorescence when excited by the excitation light, and a control section turning-on the excitation light source while the boundary of the transmission region and the reflection region traverses the light-path, in order to provide an illumination light source device capable of preventing a deterioration of the fluorescent body, whereby improving a color reproducibility by use of the color mixture occurred at the boundary region between the transmission light-path and the reflection light-path effectively and improving the brightness of image.