Abstract:
A light source unit includes a light source which emits a light bundle in one direction; a polarizing unit which is formed to selectively transmit a certain polarized light of a certain wavelength in the light bundle; and a reflection unit which is formed so as to delay the phase of the polarized light so that the polarized light is reflected by the polarizing unit, convert one part of the wavelength of the polarized light, and reflect the polarized light toward the polarizing unit.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to an image projection device that outputs an image and a method of controlling the image projection device. 
     2. Background Art 
     With technical advances in the formation age, particular emphasis is placed on the importance of a display apparatus realizing a large-sized screen. As one example of the apparatus realizing the large-scale screen, there is a projector equipped with a function of enlarging an image. 
     In recent years, the focus has been on the performance of the projector, and various attempts are made to improve the performance of the projector in software. As one example, an attempt has been made to realize a projector that uses a light source, such as a laser diode (LD), a light emitting diode (LED), an organic EL (OLED), or a fluorescent material. 
     For example, when a voltage is applied to both ends of the laser diode, the laser diode emits a coherent light, that is a laser, which has a constant wavelength through stimulated emission and enhanced interference. The laser that is emitted from each of the multiple laser diodes is condensed through a lens and serves as a high-brightness light source. 
     Generally, a light source unit emits a light with various colors using a blue light. However, a propagation path for the blue light is necessary to obtain the blue light, and thus a space for forming a propagation path for the blue light has to be secured within the light source unit. 
     SUMMARY OF THE INVENTION 
     Therefore, an object of the present invention is to provide a more compact light source unit. 
     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a light source unit that includes a light source, a polarization unit, and a reflection unit. The light source emits a pencil of rays in one direction. The polarization unit is configured to selectively transmit a specific polarization light with a specific wavelength in the pencil of rays. The reflection unit is configured to retard a phase of the polarization light and to convert a wavelength of one portion of the polarization light in such a manner that the polarization light is reflected by the polarization unit, and to reflect the polarization light toward the polarization unit. 
     According to one embodiment of the present invention, the polarization unit may be configured to transmit a P wave blue light in the pencil of rays. 
     According to one embodiment of the present invention the reflection unit may include a phase retardation layer that is configured to retard a phase of the blue light in such a manner that the P wave blue light emitted from the polarization unit is converted into an S wave blue light. 
     According to one embodiment of the present invention, the phase retardation layer may be configured to retard a phase of the blue light by λ/4. According to one embodiment of the present invention, the reflection unit may further include a wavelength conversion wheel that includes a fluorescent region which includes a fluorescent material that converts the wavelength of the blue light. 
     According to one embodiment of the present invention, the wavelength conversion wheel may be sectioned based on a predetermined central angle to form a fluorescent region and a reflective region, the fluorescent region may include different fluorescent materials that convert the blue light into different wavelengths, and the reflective region may reflect the blue light. 
     According to one embodiment of the present invention, the wavelength conversion wheel may include a circle-shaped that is made of a metal material to reflect light, the fluorescent region that is formed along an edge of the base in such a manner as to have the shape of a closed loop and that includes at least one fluorescent material to convert the wavelength of the blue light, and the reflective region that is formed adjacent to the fluorescent region in such a manner as to have the shape of a closed loop along the edge and that reflects the blue light. 
     According to one embodiment of the present invention, the wavelength conversion wheel may include a circle-shaped base that is made of a metal material to reflect light, and at least one a fluorescent layer that is formed on one surface of the base along an edge of the base to a predetermined width in such a manner as to have the shape of a closed loop, and that includes at least one or more fluorescent materials that are superimposed onto one another. 
     According to one embodiment of the present invention, the wavelength conversion wheel may further include a heat sink that is formed to protrude from the other surface of the base in order to dissipate heat. 
     According to one embodiment of the present invention, the wavelength conversion wheel may include the circle-shaped base that is made of the metal material to reflect the light, and the fluorescent layer that is formed on one surface of the base along an edge of the base to a predetermined width in such a manner as to have the shape of a closed loop, and that converts the wavelength of the blue light into at least one wavelength, in which the fluorescent layer may be mixed with at least one fluorescent material that changes the wavelength of the blue light. 
     According to one embodiment of the present invention may further include a color wheel that is configured to be partitioned into segments with multiple colors and to rotate about the center of the color wheel in such a manner that the pencil of rays that is reflected by the polarization beam splitting film is incident on the color wheel and is light-split into the multiple colors, in which the color wheel may be driven in such a manner a rotation speed of the color wheel is the same as a rotation speed of the wavelength conversion wheel. 
     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided an image projection device including a body that makes up an external appearance; a light source unit that is arranged within the body and that emits a pencil of rays that includes at least one color; and an image formation unit that forms an image using the pencil of rays. 
     In the image projection device, the light source unit may include a light source that emits a pencil of rays in one direction, a polarization unit that is configured to selectively transmit a polarization light with a specific wavelength in the pencil of rays; and a reflection unit that retards a phase of the polarization light and converts a wavelength of one portion of the polarization light in such a manner that the polarization light is reflected by the polarization unit, and that reflects the polarization light toward the polarization unit. 
     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a light source unit including: a wavelength conversion wheel that converts one portion of a blue light with a first phase, and converts wavelengths of the rest of the blue light; a phase retardation film that changes the first phase of the emitted light into a second phase; and a polarization beam splitting film that is configured to reflect to the second phase. 
     According to one example of the present invention, the light source unit may further include a light source that provides the polarization beam splitting film with the blue light that has a third phase which is retarded by λ/2 from the second phase. 
     According to the present invention, a blue light and wavelengths of the multiple lights are generated along substantially the same propagation path by utilizing a specific polarization component of the blue light as a light source through the use of a polarization beam splitting film that including a reflection region which reflects the blue light and of a phase retardation film. Therefore, a construction for forming a propagation path for the blue light is unnecessary, and thus a construction of a light source unit is simplified. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating operation of an image projection device according to one embodiment of the present invention; 
         FIGS. 2A and 2B  are perspective diagrams of the image projection device in  FIG. 1  when viewed from in front of and in rear of the image projection device, respectively; 
         FIG. 3  is an exploded diagram illustrating the image projection device in  FIG. 1 ; 
         FIG. 4  is a diagram for describing a construction of a light source unit in  FIG. 3 ; 
         FIG. 5  is a diagram of one portion of the light source unit for describing a light propagation path; 
         FIG. 6  is a diagram of a wavelength conversion wheel according to one embodiment; 
         FIG. 7  is a diagram of a wavelength conversion wheel according to another embodiment; 
         FIGS. 8A to 8C  are diagrams for describing a wavelength conversion wheel according to another embodiment; and 
         FIGS. 9A and 9B  are diagrams for describing a wavelength according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
       FIG. 1  is a diagram illustrating operation of an image projection device according to one embodiment of the present invention. 
     An image projection device  100  according to the present invention projects a large-scaled image onto a screen S that is positioned a very short distance away from the image projection device  100 . 
     The image projection device  100  is an apparatus that realizes an image using light emitted from a light source, and projects the realized image. As the image projection device  100 , for example, there is a projector that enlarges and projects an image as illustrated. As one example of the image projection device  100  according to the present invention, the projector will be described below. However, the image projection device  100  is not limited to this and may be applied to, for example, a projection apparatus that is built into a projection television set and the like. As an example, the projector is described in the present specification. 
     As illustrated, the image projection device  100  is positioned in front of the screen S but below (above) the screen  3 , in such a manner that a large-scaled image is projected onto the screen S. 
     The image projection device  100  will be described below.  FIGS. 2A and 2B  are perspective diagrams of the image projection device  100  in  FIG. 1  when viewed from in front of and in rear of the image projection device  100 , respectively. 
     Constituent elements illustrated in  FIGS. 2A and 2B  are not necessarily indispensable. The image projection device  100  may include only one or more of these or may further include other constituent elements. 
     Referring to the drawings, upper and lower cases  111  and  112  make up the exterior appearance of the image projection device  100 . Various optical components and electronic components are accommodated in a space that is formed by the upper and lower cases  111  and  112 . At least one or more middle cases may be arranged between the upper and lower cases  111  and  112 . 
     An operation unit  113  is arranged in the upper case  111 . Any tactile manner that gives a user a tactile feeling when operating the operation unit  113  may be employed. 
     Input into the operation unit  113  are commands for controlling the operation of the image projection device  100 . In terms of functionality, the operation unit  113  is used for inputting a start command, an end command, or the like on an operation menu. 
     In addition, the operation unit is operated for zooming-in or zooming-out on an image that is projected from the image projection device  100 . The operation unit  113  is operated for an image projected from the image projection device  100  to remain in focus. 
     An air flow unit  112 , an interface  115 , and a power supply  116  are arranged in the lower case  112 . 
     The air flow unit  114  is configured to have multiple through holes through which outside air is introduced into the image projection device  100 . Thus, by convection, the image projection device  100  is air-cooled. 
     The interface  115  provides a connection to an external apparatus for data exchange. External image data that corresponds to an image which is projected from the image projection device  100  is input through the interface  115 . Referring to the drawings, the interface  115  includes terminals that are electrically connected to electronic apparatuses that can supply image or sound data, such as a computer and a DVD player. 
     The power supply  116  that supplies power to the image projection device  100  is mounted in the lower case  112 . The power supply  116  is configured to convert alternating current, which is supplied for home use, into direct current. However, the configuration of the power supply  116  is not limited to this, and may be a rechargeable battery that is removably attached. 
     A sound output unit in the form of a speaker is provided in either of the upper and lower cases  111  and  112 . For example, an antenna for receiving broadcast signals may additionally be either of the upper and lower cases  111  and  112 . 
     As illustrated, a projection unit  117  is configured to project an image from an upper surface of the upper case  111  to the outside. The projection unit  117  includes a projection system  140  (or an optical system) (refer to  FIG. 3 ) in which multiple lenses and mirrors are arranged given distances away from one another. With the operation of the operation unit  113 , the projection unit  117  is configured to adjust distances between each of the multiple lenses and the mirrors. Thus, the image projection device  100  performs a zooming or focusing function. 
     The image projection device  100  includes a light source unit that emits light. The light source unit according to the present invention includes a light source that emits a blue light, and is configured in such a manner that a propagation path for the blue light is the same as the propagation paths for multiple lights that have different wavelengths from a wavelength of the blue light. A construction of the light source unit will be described in detail below. 
       FIG. 3  is an exploded diagram of the image projection device in  FIG. 1 .  FIG. 4  is for a diagram for describing the construction of the light source unit in  FIG. 3 .  FIG. 5  is a diagram of one portion of the light source unit for describing a light propagation path. 
     Referring to  FIG. 3 , the image projection device  100  includes the upper case  111 , the lower case  112 , a control circuit board  121 , a light source unit  300 , an image conversion device and a projection lens  140 . 
     The control circuit board  121  is mounted in the lower case  112 . The control circuit board  121  is configured as one example of a controller that performs various functions of the image projection device  100 . 
     The light source unit  300  is mounted in the lower case  112 . The light source unit  300  means a system that is configured from optical components for realizing an image of an object using reflection and refraction of light. A frame (not illustrated) of assemble for the light source unit  300  is additionally arranged between the light source unit  300  and the lower case  112 . 
     The image conversion device is configured to form an image using incident light from the light source unit  300 . For example, the image conversion device is an optical system that performs light conversion or light separation on generated light and performs image conversion using a display element. The image that is output from the image conversion device passes through the projection lens  140  in order to be projected onto the screen in a large-scaled manner. 
     The light source unit  300  is configured to form a pencil of rays using electric energy. The light source unit  300  according to the present invention will be described in detail below. 
     Referring to  FIGS. 3 and 4 , the light source unit  300  includes a light source  301 , a first condensing lens  302 , a Fly&#39;s Eye lens  303 , a second condensing lens  304 , a polarization beam splitting film  305 , a phase retardation film  306 , a third condensing lens  307 , a wavelength conversion wheel  310 , a fourth condensing lens  308 , and a color wheel  309 . 
     The light source  301  is configured in such a manner that the light source  301  is provided with electric energy, converts the electric energy into light energy, and thus generates a pencil of rays. The light source  301  is configured from LEDs, OLEDs, or fluorescent materials. The light source  301  according to the embodiment of the present invention is configured from multiple laser diodes (LD). The light source  301  according to the present invention is configured from an LD array of multiple high-power blue laser diodes. 
     A blue light emitted from the light source  301  passes through various types of lens in order to be condensed and be uniformly distributed. The lenses that the blue light passes through include the first condensing lens  302 , the Fly&#39;s Eye lens  303  and the second condensing lens  304 . 
     The condensing lens plays a role of focusing a pencil of rays onto a desired point in a desired direction. The Fly&#39;s Eye lens is configured from a small lens that has a rectangular surface and a direction of a longer side of the small lens corresponds to direction in which a light emitting unit focuses a pencil of rays. 
     The blue light that passes through the first condensing lens  302 , the Fly&#39;s Eye lens  303 , and the second condensing lens  304  reaches a polarization unit. The polarization unit is configured from the polarization beam splitting film  305 . The polarization beam splitting film (PBF)  305  is an optical system that selectively reflects or transmits only a specific polarization component of a specific wavelength. 
     For example, the polarization beam splitting film  305  selectively transmits a P wave in a wavelength (approximately 380 nm to approximately 480 nm) of blue light in a pencil of rays. In addition, the polarization beam splitting film  305  reflects not only red light R, green light G and yellow light Y, but also an S wave of blue light. 
     In this case, it is desirable that a transmission rate of a P wave of light with an approximately 420 nm to approximately 470 nm wavelength through the polarization beam splitting film  305  is approximately 90% or greater and a transmission rate of a S wave is approximately 10%. In addition, it is desirable that a transmission rate of light with an approximately 470 nm to approximately 800 nm wavelength is approximately 10% or smaller (a reflection rate is approximately 90% or greater). 
     Therefore, according to the present invention, because the light that passes through the polarization beam splitting film  305  is light that is finally provided, it is desirable that in order to improve efficiency, light that is emitted from the LD array is P wave blue light. 
     The P wave blue light that passes through the polarization beam splitting film  305  is reflected by a reflection unit and return to the polarization beam splitting film  305 . The reflection unit includes the phase retardation film  306 , the third condensing lens  307 , and the wavelength conversion wheel  310 . The P wave blue light passes through the phase retardation film  306  and the third condensing lens  307 , is reflected by the wavelength conversion wheel  310 , passes again through the third condensing lens  307  and the phase retardation film  306 , and reaches the polarization beam splitting film  305 . 
     The phase retardation film  306  is configured from a λ/4 wave plate that retards a phase of the P wave blue light only by λ/4 while the P wave blue light passes through the phase retardation film  306 . The phase retardation film  306  retards the phase of the blue light only by λ/4. The blue light that passes through the phase retardation film  306  passes through the third condensing lens  307 . The blue light condensed by the third condensing lens  307  is reflected by the wavelength conversion wheel  310 . 
     The wavelength conversion wheel  310  includes a wave conversion material that converts a wavelength of the blue light into red R, green G, and yellow Y wavelengths. Generally, the wavelength conversion wheel  310  is in the shape of a plate that is made of a material which reflects the light, and is configured in such a manner that the wavelength conversion wheel  310  rotates about a spindle that perpendicularly pierces through the center of the plate. The blue light is incident on the wavelength conversion wheel  310  that rotates, and blue light B, red light R, green light G, and yellow light Y are reflected from the wavelength conversion wheel  310 . 
     The wavelength conversion wheel  310  is configured to have RGBY regions, each of which a reflective mirror made of a metal material. A construction of the wavelength conversion wheel  310  according to various embodiments of the present invention will be described in detail below. 
     The blue light B, the red light R, the green light G, and the yellow light Y are condensed by the third condensing lens  307  and are incident on the phase retardation film  306 . 
     Referring to  FIG. 5 , phases of the blue light B, the red light R, the green light G, and the yellow light Y are retarded only by λ/4 by the phase retardation film  306 . However, in this case, a wavelength of each light incident on the phase retardation film  306  is not converted. 
     The phases of the blue light B, the red light R, the green light G, and the yellow light Y are retarded once more by λ/4 by the phase retardation film  306 , and thus the blue light B, the red light R, the green light G, and the yellow light Y are polarization-converted into an S wave. The S wave blue light B, the red light R, the green light G, and the yellow light Y reach the polarization beam splitting film  305 . 
     As described above, since the polarization beam splitting film  305  transmits only the P wave blue light, the S wave blue light B, the red light R, the green light G, and the yellow light Y are reflected by the polarization beam splitting film  305 . 
     The polarization beam splitting film  305  is arranged in such a manner that the polarization beam splitting film  305  is inclined by a predetermined angle with respect to the phase retardation film  306 . For example, the polarization beam splitting film  305  is arranged in such a manner that the polarization beam splitting film  305  is inclined by 45 degrees with respect to the phase retardation film  306 . In this case, light that is incident on the polarization beam splitting film  305  along a direction opposite to a first direction D 1  is reflected in a second direction D 2  perpendicular to the first direction D 1 . 
     However, a direction in which the light is finally emitted from a light source device is not limited to the second direction D 2 . That is, the direction of the light that is finally emitted from the light source device is adjusted by adjusting an angle of the polarization beam splitting film  305 . 
     That is, a propagation path for the blue light is changed by using the polarization beam splitting film that transmits only the specific wavelength and the specific polarization component and the retardation film that converts the polarization component. 
     Accordingly, the light source device according to the present invention, the blue light B that is generated in the light source propagates in the same propagation path as does the red light R and the green light G, and the yellow light Y that are regenerated from the wavelength conversion wheel  310 . That is, since the blue light B, and the red light R, the green light G, and the yellow light Y propagate along the same propagation path, a separate construction for emitting the blue light B along with lights with different wavelengths is unnecessary. 
     Accordingly, an internal frame of the power source device is simplified and a whole size of the power source device is reduced. 
     The light source device may further include a fourth condensing lens  308  that condenses the blue light B, the red light R, the green light G, and the yellow light Y that propagates in the second direction D 2 . A pencil of rays that is condensed by the fourth condensing lens  308  is color-split by the color wheel  309  and is emitted to the outside. 
     The color wheel  309  is configured in such a manner that that the color wheel  309  are repeatedly partitioned into multiple segments categorized into at least the blue, the red, the green, and the yellow and rotate at high speed. In order to rotate the color wheel  309 , a motor (not illustrated) is provided that is mounted on the color wheel  309 . 
     The color wheel  309  is formed to have the shape of a disk with a predetermined diameter. A pencil of rays that is provided from the fourth condensing lens is light-split into a light of any one of red, green, blue, and yellow according to a color of the color wheel  309 . 
     As described above, the blue light and the pencil of rays with the rest of the wavelengths propagate along the same propagation path by the wavelength conversion wheel including a reflective region and a fluorescent region. The fluorescent region is made of various types of fluorescent materials that convert the wavelength of the blue light, and the fluorescent material has various structures. A construction of the wavelength conversion wheel according to various embodiments of the present invention will be described in detail below. 
       FIG. 6  is a diagram of the wavelength conversion wheel according to one embodiment of the present invention. The wavelength conversion wheel illustrated in  FIG. 6  is configured from multiple segments, in such a manner that the rotation of the wavelength conversion wheel sequentially emits lights of multiple colors. 
     The wavelength conversion wheel  310  is configured to have the shape of a circular plate, in such a manner that the wavelength conversion wheel  310  rotates about the spindle that extends in a direction perpendicular to the circular plate from the center of the circular plate. The wavelength conversion wheel  310  in the shape of the circular plate is made of a metal disk. Therefore, the blue light incident on the wavelength conversion wheel  310  is reflected in the opposite direction by the wavelength conversion wheel  310  in the shape of the metal disk. 
     The reflective region  311  includes an aluminum (Al) reflective layer. The reflective region  311  is configured in such a manner that the reflective region  311  reflects the blue light in order for the blue light being propagated to the wavelength conversion wheel  310 . The wavelength and phase of the blue light do not change while the blue light is reflected by the reflective region  311 . That is, only a propagation path for the blue light changes by the reflective region  311 . 
     The reflective region  311  is configured to be integrated with a central portion of the circle-shaped disk that extends from the center of the center of the wavelength conversion wheel  310 . That is, the whole disk is made of an aluminum material. 
     The reflective region  311  and the fluorescent region  312  are formed inward the center from a circumference of the wavelength conversion wheel  310  to a predetermined width. It is desirable that the predetermined width is set in such a manner that the predetermined width includes a region BA in which the blue light has the likelihood of reaching the wavelength conversion wheel  310  within the light source unit. 
     A size of the reflective region  311  and a size of the fluorescent region  312  are determined by color coordinates of a fluorescent material that converts a different wavelength. That is, an angle of the segment depends on a value that is obtained by calculating the time the blue light takes to reach according to the color ordinates and the brightness of the fluorescent material. 
     The fluorescent region  312  is partitioned into multiple regions that are made of fluorescent materials with different colors that convert the wavelength of the blue light into different wavelength. For example, the fluorescent region  312  includes a red region  312 R, a green region  312 G, and a yellow region  312 Y. 
     For example, an angle to which the reflective region  311  is formed is set to approximately 29 degrees, an angle to which the red region  312 R is formed is set to approximately 63 degrees, an angle to which the green region G is formed is set to approximately 52, and an angle to which the yellow region  31 Y is formed is set to approximately 36 degrees. 
     It is desirable that the green region  312 G, the red region  312 R, and the yellow region  312 Y are sequentially arranged in order for the wavelength conversion wheel  310  to emit various colors over time. While the wavelength conversion wheel  310  rotates, the blue light is incident to any one of the green region  312 G, the red region  312 R, the yellow region  312 Y, and the reflective region  311 , and any one of the blue light, the green light, the red light, and the yellow light is generated. 
     However, according to the speed at which the wavelength conversion wheel  310  rotates, lights of multiple different colors are mixed and are emitted as a white light. The pencil of rays that is emitted as the white light passes through the fourth condensing lens  308  and the color wheel  309 , and each color is realized and is emitted. 
     Formed in the color wheel are a blue B segment, a green G segment, a red R segment, and a yellow Y segment that correspond to the reflective region  311 , the green region  312 G, the red region  312 R, and the yellow region  312 Y, respectively. In addition, the wavelength conversion wheel  310  and the color wheel  309  are driven at substantially the same speed. In a case where the light forms a picture or an image by the wavelength conversion wheel  310  and the color wheel  309 , a speckle phenomenon is prevented. 
     A fluorescent material is dispensed onto each of the green region  312 G, the red region  312 R, and the yellow region  312 Y. That is, a mirror layer is formed on one surface of the metal disk in the wavelength conversion wheel  310 . A fluorescent material in powder form that is mixed with an organic binder such as silicone is dispensed onto the mirror layer in order to form each fluorescent region  312 . 
     In addition to the silicone resin, polymer or glass power may be used. 
     As the yellow wavelength conversion material, it is also possible to use YAG-based fluorescent materials such as (Y 1-x-y Gd x Ce y ) 3 Al 5 O 12 , (Y 1-x Ce x ) 3 Al 5 O 12 , (Y 1-x Ce x ) 3 (Al 1-y Ga y ) 5 O 12 , (Y 1-x-y Gd x Ce y )3(Al 1-z Ga z ) 5 O 12 , LuAG-based fluorescent materials such as (Y 1-x-y Lu x Ce y ) 3 Al 5 O 12 , a silicate-based fluorescent such as (Sr,Ca,Ba,Mg) 2 SiO 4 :Eu, and an oxynitride-based fluorescent material such as (Ca,Sr)Si 2 N 2 O 2 :Eu. 
     As the green wavelength conversion material, Y 3 (Al,Ga) 5 O 12 :Ce, CaSc 2 O 4 :Ce, Ca 3 (Sc,Mg) 2 Si 3 O 12 :Ce, (Sr,Ba) 2 SiO 4 :Eu,(Si,Al) 6 (O,N) 8 :Eu (β sialon), (Ba,Sr) 3 Si 6 O 12 N 2 :Eu, SrGa 2 S 4 :Eu, and BaMgAl 10 O 17 :Eu,Mn are desirable. It is further desirable that LuAG-based fluorescent material such as (Y 1-x-y Lu x Ce y ) 3 Al 5 O 12  is used. 
     As the red wavelength conversion material, it is possible to use (Ca,Sr,Ba) 2 Si 5 (N,O) 8 :Eu, (Ca,Sr,Ba)Si(N,O) 2 :Eu, (Ca,Sr,Ba)AlSi(N,O) 8 :Eu, (Sr,Ba) 3 SiO 5 :Eu, (Ca,Sr)S:Eu, (La,Y) 2 O 2 S:Eu, K 2 SiF 6 :Mn, and CaAlSiN:Eu. 
     However, the wavelength conversion materials are not limited to these fluorescent materials, and various fluorescent materials may be used. Light in each wavelength band is reflected by the wavelength conversion materials describe above. 
     On the other hand, the fluorescent region  312  may be formed in the form of an optoceramic instead of mixed silicone resin. The optoceramic, as a fluorescent film in a bulk form, may be bonded directly on the mirror. The optoceramic material is one that is mixed with an inorganic or organic pigment that absorbs or reflects (transmits) a light in a specific wavelength band, of which a wavelength is changed by a fluorescent material. 
     The optoceramic is made of a ceramic material. The optoceramic itself is conveniently bonded directly to the wheel. When the optoceramic is used thermal stability is improved compared to organic silicone resin. 
     As the optoceramic material, is possible to basically use YAG-based materials such as (Y 1-x-y Gd x Ce y ) 3 Al 5 O 12 , (Y 1-x CeO 3 Al 5 O 12 , (Y 1-x CeO 3 (Al 1-y Ga y ) 5 O 12 , and (Y 1-x-y Gd x Ce y ) 3 (Al 1-z Ga z ) 5 O 12 , LuAG-based materials such as (Y 1-x-y Lu x Ce y ) 3 Al 5 O 12 , and Y 3 (Al,Ga) 5 O 12 :Ce,(Si,Al) 6 (O,N) 8 :Eu (β sialon). 
     According to a type of mold that is provided, the optoceramic material is formed into various shapes such as a fan and a disc. The optoceramic material can be processed to a thickness of 0.2 t. 
       FIG. 7  is a diagram illustrating a wavelength conversion wheel according to another embodiment. 
     Referring to  FIG. 7 , a wavelength conversion wheel  320  is configured in such a manner as to simultaneously emit lights of multiple colors. The wavelength conversion wheel  320  includes a reflective region  321  and a fluorescent region  322 , each of which has the shape of a close loop ring. The wavelength conversion wheel  320  according to the present embodiment has substantially the same features as does the wavelength conversion wheel  310  except for shapes and arrangement constructions of the reflective region  321  and the fluorescent region  322 . According, the description that is provided referring to  FIG. 6  is referred to for a description that is omitted due to redundancy. 
     The wavelength conversion wheel  320  is configured to have the shape of a plate, and includes the reflective region  321  and the fluorescent region including a red region  322 R, a green region  322 G, and a yellow region  322 Y. The reflective region  321  and the fluorescent region  322  are formed inward toward the center of the plate from a circumference of the plate to a predetermined width. It is desirable that the predetermined width is set in such a manner that the predetermined width includes the region BA that the blue light reaches. 
     The red region  322 R is formed along a circumference of the plate and has the shape of a closed curve. The red region  322 R is formed to a predetermined width. The green region  322 G is formed in the shape of a closed loop along a circumference of the red region  322 R. Likewise, the reflective region  321  and the yellow region  322 Y are formed in the shape of a closed loop. For example, each region is formed in the shape of a ring or a band. 
     The regions are formed in such a manner as to have substantially the same width, but are not limited to the same width. The regions may have different widths according to the region BA that the blue light reaches and the circumference of the plate. 
     The blue light is incident on the reflective region  321 , the red region  322 R, the green region  322 G and the yellow region  322 Y at the same time. Therefore, when the blue light reaches the wavelength conversion wheel  320 , a blue light, a green light, a red light, and a yellow light are simultaneously reflected and thus a white light is emitted. 
     While the wavelength conversion wheel  320  according to the present embodiment rotates, lights of multiple colors are emitted at a time, and efficiency in the emittance of a pencil of lays is improved. 
       FIGS. 8A to 8C  are diagrams for describing a wavelength conversion wheel  330  according to another embodiment.  FIG. 8A  is a diagram of the wavelength conversion wheel  330 .  FIG. 8B  is a cross-sectional diagram of the wavelength conversion wheel  330  taken along line  8 B- 8 B on  FIG. 8A . The wavelength conversion wheel  330  according to the present invention is formed in such a manner that a reflective layer  331  and a fluorescent layer  332  are superimposed onto each other in an incident direction of the blue light. Thus, the blue light is reflected by each layer, thereby having different colors. 
     That is, as illustrated in  FIG. 8B , a red fluorescent layer  332 R is formed on the reflective layer  331  that reflects light, a green fluorescent layer  332 G is formed on the red fluorescent layer  332 R, and yellow fluorescent layer  332 Y is formed on the green fluorescent layer  332 G. The reflective layer  331  and the fluorescent layer  332  are formed along the circumference of the plate in such a manner as to have the shape of a closed loop. In addition, it is desirable that the reflective layer  331  and the fluorescent layer  332  are formed to have predetermined widths in such a manner that the reflective layer  331  and the fluorescent layer  332  includes the region BA on which a blue light is incident. 
     The blue light is incident on the wavelength conversion wheel  330 , and a yellow light of which a wavelength is converted by a fluorescent material included in the yellow fluorescent layer  332 Y is reflected to the outside of the wavelength conversion wheel  330 . In the same manner, the green fluorescent layer  332 G and the red fluorescent layer  332 R converts the wavelength of the blue light and then reflects the green and red light. In addition, the blue light of which the wavelength is not converted by the fluorescent layer  332  is reflected by the reflective layer  331 . Accordingly, the blue light, the green light, the red light, and the yellow light are emitted from the region BA on which the blue light is incident and are provided as the white light. Accordingly, efficiency in the emittance of light is improved. 
       FIG. 8C  is a diagram for describing the wavelength conversion wheel on which a heat sink is mounted. Referring to  FIG. 8C , a heat sink  333  is arranged on the back side of the reflective layer  331 . The heat sink  333  is made of a metal material. 
     On the other hand, the heat sink is made of the same material as that of the reflective layer  331 , and the reflective layer  331  and the heat sink are integrated into one piece. 
     That is, the fluorescent layer  332  is formed on one surface of the reflective layer  331 , and the heat sink  333  that includes at least one protrusion for dissipating heat is formed on the other surface of the reflective layer  331 . 
     According to the present embodiment, one surface of the wavelength conversion wheel is made of a metal material, and thus the heat sink is simply formed without going through a separate process of manufacturing the heat sink. 
       FIGS. 9A to 9B  are diagrams for describing a wavelength conversion wheel according to another embodiment.  FIG. 9A  is a diagram of the wavelength conversion wheel.  FIG. 9B  is a cross-sectional diagram of the wavelength conversion wheel taken along line  9 B- 9 B on  FIG. 9A . 
     A wavelength conversion wheel  340  includes a reflective layer  341  and a fluorescent layer  342 . The fluorescent layer  342  includes at least one material. For example, the fluorescent layer  342  includes a red fluorescent material  342  R, a green fluorescent material  342 G, and a yellow fluorescent material  342 Y. 
     That is, the reflective layer  341  and the fluorescent layer  342  are combined into at least one layer. When the blue light is incident on each fluorescent material, the wavelength of the blue light is converted and is reflected. 
     The light source unit according to the present invention is mounted not only on the image projection device and but also on a lighting apparatus. For example, in a case where the light source unit is mounted in the lighting apparatus that, over time, emits a blue light, a green light, a red light, and yellow light, as substantially the same color, a white light, a configuration of the color wheel is omitted. When the light source unit is installed in a narrow space, illumination with an improved lighting efficiency can be realized. 
     The configuration and the method relating to the light source unit, and the image projection device and the lighting apparatus that include the light source unit, described above according to the embodiments, are not applied in a limited manner, but all of or some of the embodiments may be selectively combined with each other to create various modifications to the embodiments. 
     The configuration and the method of the embodiments according to the present invention, described above, are not applied in a limiting manner, but all of or some of the embodiments may be selectively combined with each other to create various modifications to the embodiments. 
     It will also be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.