Abstract:
Disclosed is a cooling apparatus of a color wheel for color separation in a single plate type projector and a projection system using the projector, which comprises an airflow generator, thereby cooling the color wheel and a rod lens of the single plate type projector. The cooling apparatus of the color wheel of the projector of the present invention prevents the color wheel and the rod lens from being thermally degraded by using the high-powered lamp. Further, an airflow generator such as the airfoil-shaped or plate-shaped blades is formed on a hub of the color wheel, thereby miniaturizing the system of the projector and reducing its production cost.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to the field of the cooling of a projector, and more particularly to a cooling apparatus of a color wheel for color separation in a single plate type projector and a projection system using the projector. The cooling apparatus comprises an airflow generator, thereby cooling the color wheel and a rod lens of the single plate type projector. 
   2. Description of the Related Art 
   A general projector comprises three picture displays. The picture display may be a projective liquid crystal display (LCD), a digital micro-mirror display (DMD), or a reflective liquid crystal display (LCD). Each of light sources including red, green, and blue colors is provided to a corresponding one of three picture displays. Then, the projector combines the colors, thereby displaying a picture. However, a single plate type reflective projector comprises one picture display. The light sources including red, green, and blue colors are provided to the single picture display in a time-sharing mode or in a blocked scroll mode, thereby outputting a synchronized picture signal. That is, the single plate type reflective projector refers to a projector for displaying a color picture using one picture display. 
     FIG. 1  is a schematic view showing an optical arrangement in a conventional reflective projector. 
   With reference to  FIG. 1 , the conventional reflective projector comprises a lamp  100 , a color wheel  110 , a rod lens  120 , a first lens  130 , a reflecting mirror  140 , a second lens  150 , a prism  160  with a panel  161 , and a projecting lens  170 . 
   The color wheel  110  serves to separate light generated by the lamp  100  into three colors, i.e., red, green, and blue colors. Herein, the light generated by the lamp  100  is metal halide or xenon. 
   The color wheel  110  is rotated by a driving gear (not shown). Three filters corresponding to each color such as red, green, and blue are distributed on the color wheel  110  into equal parts. 
   The rod lens  120  serves to irregularly reflect incident light, thereby mixing the incident light and generating uniform light. The light passing through the rod lens  120  is provided to the panel  161  of the prism  160  via an optical system including the first lens  130 , the reflecting mirror  140 , and the second lens  150 , thereby reflecting a synchronized picture signal and expensively projecting the signal through the projecting lens  170 . 
   In this case, in order to control the shape of focused light, instead of a fly eye lens (FEL), the projector uses the rod lens  120 . Therefore, the light generated by the lamp  100  is focused on a plane of incidence of the rod lens  120  having a small area. 
     FIGS. 2   a  and  2   b  show a color wheel of a conventional reflective projector in detail. 
   With reference to  FIGS. 2   a  and  2   b , the light generated by a lamp  210  passes through the color wheel  220 . At this time, the color wheel  220  serves to separate the light generated by the lamp  210  into plural colors. The separated light is incident on a plane of incidence of a rod lens  230 . 
     FIG. 2   a  is a perspective view of the color wheel  220  of the conventional reflective projector, and  FIG. 2   b  is a cross-sectional view of the color wheel  220  of the conventional reflective projector. 
   As shown in  FIG. 2   b , the light generated by the lamp  210  passes through the color wheel  220  and is focused on the plane  231  of incidence of the rod lens  230 , thereby overheating a plane  221  of the color wheel  220  as well as the plane  231  of incidence of the rod lens  230 . 
   A glass with high refractivity, such as BK-7 which is used as lens material, has a heat resistance, to a maximum temperature of about 400. A color separation filter used in the color wheel is generally made of polymer and has a heat resistance, to a maximum temperature of about 200. 
   The color wheel  220  is rotated by the driving gear (not shown). The rotation of the color wheel  220  increases the incident area of light. Airflow generated by the rotation of the color wheel  220  provides a cooling effect to the color wheel  220  itself. Therefore, during the operation of the projector, the color wheel  220  can be cooled itself to some degree. 
   However, during the operation of the projector, a large quantity of the light is always focused on the small area of the rod lens  230 , i.e., the plane  231  of incidence. Therefore, although the material of the rod lens  230  has a heat resistance greater than that of the color wheel  220 , the rod lens  230  is not high in heat resistance. Particularly, when the plane  231  of incidence of the rod lens  230  is coated, the resistance to thermal degradation of the coating layer cannot be assured. 
   Recently, a brighter projector has been required more and more. In order to satisfy this recent trend, a high-powered lamp is required. In this case, a color separation system including the color wheel and the rod lens of the single plate type optical system further demands a cooling apparatus for cooling the color wheel and the rod lens. 
   SUMMARY OF THE INVENTION 
   Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a cooling apparatus of a color wheel for color separation in a single plate type projector and a projection system using the projector, which comprises an airflow generator, thereby cooling the color wheel and a rod lens of the single plate type projector. 
   In accordance with one aspect of the present invention, the above and other objects can be accomplished by the provision of a cooling apparatus of a color wheel of a projector. The cooling apparatus comprises a light source for generating light, a color wheel, on which the light generated by the light source is incident, including blades for generating airflow by the rotation of the color wheel, and a lens, on which the light having passed through the color wheel is incident. 
   Preferably, the light source may comprise a lamp, and the lens may be a rod lens. 
   Further, preferably, the blades may be shaped in an airfoil or a plate, and installed on both side surfaces of the color wheel. 
   In accordance with another aspect of the present invention, there is provided a cooling apparatus of a color wheel of a projector, wherein light generated by a light source is incident on the color wheel, and blades are installed on a hub of the color wheel, thereby generating airflow by the rotation of the color wheel. 
   Preferably, the blades may be shaped in an airfoil or a plate, and installed on both side surfaces of the color wheel. 
   The cooling apparatus of the color wheel of the projector of the present invention prevents the color wheel and the rod lens from being thermally degraded by using the high-powered lamp. 
   Further, an airflow generator such as the airfoil-shaped or plate-shaped blades is formed on a hub of the color wheel, thereby miniaturizing the system of the projector and reducing its production cost. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a schematic view showing an optical arrangement of a conventional reflective projector; 
       FIGS. 2   a  and  2   b  are a perspective view and a cross-sectional view of a color wheel of a conventional reflective projector, respectively; 
       FIGS. 3   a  and  3   b  are a plan view and a perspective view of a cooling apparatus of a color wheel of a projector in accordance with an embodiment of the present invention, respectively; 
       FIGS. 4   a  and  4   b  are a plan view and a perspective view of a cooling apparatus of a color wheel of a projector in accordance with another embodiment of the present invention, respectively; and 
       FIG. 5  is a cross-sectional view showing an operation of the cooling apparatus of the color wheel of the projector of the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 3   a  and  3   b  are a plan view and a perspective view of a cooling apparatus of a color wheel of a projector in accordance with an embodiment of the present invention, respectively. 
   With reference to  FIGS. 3   a  and  3   b , the cooling apparatus of the color wheel of the projector in accordance with an embodiment of the present invention comprises a light source  310  for generating light, a color wheel  320 , on which the light generated by the light source  310  is incident, and a lens  330 , on which the light having passed through the color wheel  320  is incident. A plurality of airfoil-shaped blades  321  are installed on the color wheel  320 . The airfoil-shaped blades  321  serve to generate airflow for preventing the color wheel  320  from being thermally degraded by the energy of the incident light. 
   Generally, a lamp is used as the light source  310 . The light generated by the lamp is separated into red, green, and blue colors by the color wheel  320 . Then, the separated light passes through the lens  330 . 
   Three color filters such as red, green, and blue filters are distributed on the color wheel  320  into equal parts. The color wheel  320  is rotated by a driving gear (not shown). The lens  330  irregularly reflects the incident light, thereby mixing the incident light and generating uniform light. 
   Herein, the lens  330  is a rod lens. 
   The airfoil-shaped blades  321  are formed on a hub of the color wheel  320 . Therefore, as the color wheel  320  rotates, a airflow is generated by the airfoil-shaped blades  321 , thereby blowing air in a centrifugal direction and cooling the heated color wheel  320  and lens  330  by the energy of the light generated by the light source  310 . 
   Herein, the shape of the blade, i.e., the airflow generator of the color wheel of the projector, is not limited to the airfoil. 
     FIGS. 4   a  and  4   b  are a plan view and a perspective view of a cooling apparatus of a color wheel of a projector in accordance with another embodiment of the present invention, respectively. 
   With reference to  FIGS. 4   a  and  4   b , the configuration and function of the cooling apparatus of the color wheel of the projector in accordance with another embodiment of the present invention are similar to those of the aforementioned embodiment of  FIGS. 3   a  and  3   b , except for the shape of the airflow generator. 
   That is, the cooling apparatus of the color wheel of the projector in accordance with another embodiment of the present invention comprises a light source  410  for generating light, a color wheel  420 , on which the light generated by the light source  410  is incident, and a lens  430 , on which the light having passed through the color wheel  420  is incident. A plurality of plate-shaped blades  421  are installed on the color wheel  420 . The plate-shaped blades  421  serve to generate airflow for preventing the color wheel  420  from being thermally degraded by the energy of the incident light. Herein, the lens  430  is also a rod lens. 
   The light generated by the light source  410  is separated into red, green, and blue colors by the color wheel  420 . Then, the separated light passes through the lens  430 . As the color wheel  420  rotates, airflow is generated by the plate-shaped blades  421  installed on a hub of the color wheel  420 , thereby blowing air in a centrifugal direction and cooling the heated color wheel  420  and lens  430  by the energy of the light generated by the light source  410 . 
   Compared to the cooling apparatus of the color wheel provided with airfoil-shaped blades  321 , the cooling apparatus of the color wheel provided with the plate-shaped blades  421  is more easily manufactured, thereby reducing the production cost. 
   Those skilled in the art will appreciate that the shape of the blade, i.e., the airflow generator of the cooling apparatus of the color wheel of the projector, is not limited to the airfoil or the plate. 
     FIG. 5  is a cross-sectional view showing an operation of the cooling apparatus of the color wheel of the projector of the present invention. 
   With reference to  FIG. 5 , the cooling apparatus of the color wheel of the projector of the present invention comprises a lamp  510  for generating light, a color wheel  520 , on which the light generated by the lamp  510  is incident, a rod lens  530 , on which the light having passed through the color wheel  520  is incident. Blades  521  for generating airflow so as to prevent the color wheel  520  from being thermally degraded by the energy of the incident light are installed on the color wheel  520 . The blades  521  are shaped in an airfoil or a plate. 
   The light generated by the lamp  510  is separated into red, green, and blue colors by the color wheel  520 . The separated light passes through the rod lens  530 . 
   Three color filters such as red, green, and blue filters are distributed on the color wheel  520  into equal parts. The color wheel  520  is rotated by a driving gear (not shown). 
   The rod lens  530  irregularly reflects the incident light, thereby mixing the incident light and generating uniform light. 
   As the color wheel  520  rotates, the airfoil-shaped or plate-shaped blades  521  installed on the color wheel  520  generates airflow, thereby cooling the heated color wheel  520  and rod lens  530  by the energy of the light generated by the lamp  510 . 
   In order to more effectively cool the color wheel  520  and the rod lens  530 , the airfoil-shaped or plate-shaped blades  521  may be installed on both side surfaces of the color wheel  520 . 
   The present invention is applied to the single type reflective projector. As described above, the single plate type reflective projector comprises one picture display. The light sources including red, green, and blue colors are provided to the single picture display in a time-sharing mode or in a blocked scroll mode, thereby outputting a synchronized picture signal. The light generated by the lamp  510  is separated into red, green, and blue colors by the rotating color wheel  520 , in which three color filters such as red, green, and blue filters are distributed. The separated light is focused on the rod lens  530 . 
   The light generated by the lamp  510  passes through the color wheel  520  and focused on a plane  532  of incidence of the rod lens  530 , thereby imposing thermal overload to a plane  522  of the color wheel  520  as well as the plane  532  of incidence of the rod lens  530 . 
   In accordance with the present invention, the cooling apparatus of the color wheel of the projector comprises the airfoil-shaped or plate-shaped blades  521 , which are formed on a hub of the color wheel  520 . The airfoil-shaped or plate-shaped blades  521  serve as an airflow generator using the rotary power of the color wheel  520 . As the color wheel  520  rotates, the airfoil-shaped or plate-shaped blades  521  also rotate, thereby generating airflow around the color wheel  520  and the rod lens  530  and cooling the heated color wheel  520  and lens  530  by the energy of the light generated by the lamp  510 . 
   Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.