Abstract:
A projector having an optical engine, the optical engine including: an optical synthesizer; a plurality of display devices corresponding to the optical synthesizer; a plurality of light sources emitting light; a light guide plate provided between each light source and each display device; and a heat pipe contacting the light sources to reduce a temperature deviation between the light sources.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of Korean Patent Application No. 2003-053836, filed Aug. 4, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a projector, particularly to a projector having a simple structure, to prevent a phase shift caused by a temperature difference between a plurality of light sources and to easily control temperatures of the light sources.  
         [0004]     2. Description of the Related Art  
         [0005]     A projector generally displays a desired picture by projecting image beams onto a screen, and is applied in a projection television having a similar projecting apparatus to form a picture.  
         [0006]     The projector may be either a transparent-type projector to form a picture with light passing through a display device, or a reflection-type projector to form a picture onto a screen with light reflected by the display device.  
         [0007]     A liquid crystal projector using an LCD panel as the display device of the projector has been developed. As various technologies are developed for an optical lamp device affecting color and resolution of a displayed picture, the liquid crystal projector generally may be either an SLPS (single LCD panel system) using one LCD panel, or a TLPS (triple LCD panel system) to split light from the optical lamp device into three primary colors and project the light using the LCD panels corresponding to the three primary colors.  
         [0008]      FIG. 1  is a schematic view of a projector according to a conventional TLPS method. As illustrated, the projector using three LCD panels includes a light source  100  to emit light, two fly-eye lenses  200  to synthesize and split the light emitted from the light source  100 , and a PBS array  300 . The projector further includes two primary light collection lenses  400 , four total reflection mirrors  500 , two dichroic mirrors  510 , a magnifying lens  520 , and secondary light collection lenses  600   a,    600   b,  and  600   c  to improve the straightness of the light reflected by the mirrors. The projector further includes three LCD panels  610   a,    610   b,  and  610   c  to transform the light having the straightness improved by the secondary light collection lenses  600   a,    600   b,  and  600   c  into respective colored lights having color signals R, G, and B, an optical synthesizer  700  to synthesize the colored lights having color signals R, G, and B from the LCDs  610   a,    610   b,  and  610   c,  and a projection lens  800  to magnify and project the light synthesized by the optical synthesizer  700 .  
         [0009]     An operation of the projector having the above configuration will be described hereinbelow. The light emitted from the light source  100  is synthesized and split through the fly-eye lenses  200 , the PBS array  300 , the primary light collection lenses  400 , the total reflection mirror  500 , the dichroic mirrors  510 , and the magnifying lens  520 . Also, the light split by the dichroic mirrors  510  goes through a light modulation process by the LCD panels  610   a,    610   b,  and  610   c  representing the color signals R, G, and B, respectively.  
         [0010]     The respective colored lights representing the color signals R, G, and B by the LCD panels  610   a,    610   b,  and  610   c  are synthesized by the optical synthesizer  700 . The light synthesized by the optical synthesizer  700  is magnified and projected through the projection lens  800 .  
         [0011]     However, the projector having the above configuration has a disadvantage because a structure thereof becomes complicated and the brightness decreases due to decrease in a transmission rate of the light.  
         [0012]     To solve this problem, Korean Patent First Publication No. 2003-57751 illustrates a projection display apparatus using an LED as a light source and providing individual lights to respective LCD panels. However, since such configuration also requires a plurality of LEDs (light emitting diodes) as the light source, a temperature difference among the plurality of LEDs causes a problem such as a phase shift which shifts the image.  
       SUMMARY OF THE INVENTION  
       [0013]     Accordingly, it is an aspect of the present invention to provide a projector having a simple structure, to prevent a phase shift caused by a temperature difference between a plurality of light sources and control temperature of the plurality of light sources easily.  
         [0014]     Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.  
         [0015]     The foregoing and/or other aspects of the present invention are achieved by providing a projector having an optical engine, the optical engine including: an optical synthesizer; a plurality of display devices corresponding to the optical synthesizer; a plurality of light sources each in a respective vicinity of the plurality of display devices to emit light; a light guide plate provided between each light source and each respective display device; and a heat pipe contacting the light sources to reduce a temperature deviation between the light sources.  
         [0016]     According to an aspect of the invention, the optical engine further includes: a temperature sensor installed on the heat pipe; a cooling part to cool the light sources; and a controller to control the cooling part according to a signal from the temperature sensor.  
         [0017]     According to an aspect of the invention, the optical synthesizer is shaped like a cube and three of the display devices are provided corresponding to respective faces of the optical synthesizer.  
         [0018]     According to an aspect of the invention, each light source includes an LED. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:  
         [0020]      FIG. 1  is a schematic view illustrating a conventional projector;  
         [0021]      FIG. 2  is a schematic view illustrating a projector according to an embodiment of the present invention;  
         [0022]      FIG. 3  is a perspective view illustrating an optical engine of the projector of  FIG. 2 ;  
         [0023]      FIG. 4  is a perspective view illustrating a light source and a heat pipe of  FIG. 2 ;  
         [0024]      FIG. 5  is a flow diagram illustrating temperature control according to the projector of  FIG. 2 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0025]     Reference will now be made in detail to the embodiments of the present invention, an example of which is illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiment is described below to explain the present invention by referring to the figures.  
         [0026]      FIG. 2  is a schematic view illustrating a projector according to an embodiment of the present invention, and  FIG. 3  is a perspective view illustrating an optical engine of the projector according to  FIG. 2 . As illustrated in the drawings, the projector includes an optical engine  10 , and a cooling part  90  to cool the optical engine  10 . The optical engine  10  includes an optical synthesizer  70 , LCD panels  60   a,    60   b,  and  60   c  installed on three faces of the optical synthesizer  70 , light guide plates  50   a,    50   b,  and  50   c  respectively corresponding to rear surfaces of the LCD panels  60   a,    60   b,  and  60   c,  and a plurality of light sources  51   a,    51   b,  and  51   c  installed near upper sides and lower sides of the light guide plates  50   a,    50   b,  and  50   c.  Also, polarizing plates  61   a,    61   b,  and  61   c  are provided between the LCD panels  60   a,    60   b,  and  60   c  and the optical synthesizer  70 .  
         [0027]      FIG. 4  is a partial perspective view illustrating the light sources  51   a,    51   b,  and  51   c  and heat pipes  52   a,    52   b,  and  52   c  (as shown in  FIG. 3 ). Each of the heat pipes  52   a  has a light source  51   a,    51   b  or  52   c  of a single color (red, green or blue). As illustrated in  FIG. 4 , the light sources  51   a,    51   b  and  51   c  installed corresponding to the three faces of the optical synthesizer  70  each include a plurality of LEDs to emit the respective colored lights as an R-light source  51   a,  a G-light source  51   b,  and a B-light source  51   c.  The plurality of light sources  51   a,    51   b,  and  51   c  are attached to the heat pipes  52   a,    52   b,  and  52   c  shaped like a bar. The heat pipes  52   a,    52   b,  and  52   c  are each installed with temperature sensors  53 . The heat pipes  52   a,    52   b,  and  52   c  are made of copper having high thermal conductivity and are filled with a small amount of liquid. The insides of the heat pipes  52   a,    52   b,  and  52   c  have a low pressure to lower a boiling point of the liquid inside. Accordingly, the liquid in the heat pipes  52   a,    52   b,  and  52   c  boils at a low temperature keeping a constant temperature across the heat pipes  52   a,    52   b,  and  52   c,  regardless of positions of heat sources contacting the heat pipes  52   a,    52   b,  and  52   c.    
         [0028]      FIG. 5  is a block diagram illustrating a flow of a temperature control of the projector according to the embodiment of the present invention. As illustrated in the drawing, the temperature sensors  53  installed on the heat pipes  52   a,    52   b,  and  52   c  transfer temperature information of the light sources  51   a,    51   b,  and  51   c  to a controller  40 , and then the controller  40  controls an operation of the cooling part  90  according to an optimized temperature previously inputted to control the temperature of the light sources  51   a,    51   b,  and  51   c.    
         [0029]     Hereinbelow, an operation of the projector having the above configuration will be described. The lights from the light sources  51   a,    51   b,  and  51   c  including LEDs of colored signals R, G, and B are emitted toward the light guide plates  50   a,    50   b,  and  50   c.  The light guide plates  50   a,    50   b,  and  50   c  transfer the lights emitted from the light sources  51   a,    51   b,  and  51   c  to the LCD panels  60   a,    60   b,  and  60   c.  The lights emitted from the light sources  51   a,    51   b,  and  51   c  installed on the upper sides and lower sides of the light guide plates  50   a,    50   b,  and  50   c  can be transferred to the rear surfaces of the LCD panels  60   a,    60   b,  and  60   c  by the light guide plates  50   a,    50   b,  and  50   c.    
         [0030]     The optical synthesizer  70  is shaped like a cube and synthesizes the lights from the LCD panels  60   a,    60   b,  and  60   c.  The LCD panels  60   a,    60   b,  and  60   c  control the lights emitted from the light sources  51   a,    51   b,  and  51   c  having color signals R, G, and B to form the picture in the optical synthesizer  70 . A projection lens  80  projects the synthesized picture. The polarizing plates  61   a,    61   b,  and  61   c  provided between the LCD panels  60   a,    60   b,  and  60   c  and the optical synthesizer  70  improve the straightness of the light.  
         [0031]     The light sources  51   a,    51   b,  and  51   c  thermally contact each other through the heat pipes  52   a,    52   b,  and  52   c.  As described above, the heat pipes  52   a,    52   b,  and  52   c  reduce a temperature deviation among the heat sources contacting the heat pipes  52   a,    52   b,  and  52   c  because of their high thermal conductivity. Accordingly, the temperature deviation among the plurality of light sources  51   a,    51   b,  and  51   c  is reduced by the heat pipes  52   a,    52   b,  and  52   c.  Thus, a phase shift caused by a temperature difference among the light sources  51   a,    51   b,  and  51   c  can be removed.  
         [0032]     Additionally, the controller  40  controls an operation of the cooling part  90  to cool the heat radiated from the light sources  51   a,    51   b,  and  51   c  using the temperature sensors  53  installed on the heat pipes  52   a,    52   b,  and  52   c.  The high thermal conductivity of the heat pipes  52   a,    52   b,  and  52   c  enables the temperature sensors  53  to detect the temperature of the light sources  51   a,    51   b,  and  51   c  accurately. Accordingly, the controller  40  can keep the temperature of the light sources optimal according to the detected temperature by controlling the cooling part  90 .  
         [0033]     The embodiment of the present invention provides a projector having a simple structure, preventing the phase shift caused by temperature differences among a plurality of light sources and controlling the temperature of the plurality of light sources easily.  
         [0034]     Although an embodiment of the present invention has been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.