Abstract:
A display device having a uniform brightness and control method thereof are provided, which includes a circuit board having a light emitting diode mounting area, a light source unit comprising a plurality of light emitting diodes mounted to the light emitting diode mounting area so that light emitting characteristics can be symmetrical around the center of the light emitting diode mounting area, a light uniformizing unit for creating a uniform light from the light emitting diodes, a micro display unit located in front of the light uniformizing unit, a projection lens unit located in front of the micro display unit, and a screen located in front of the projection lens unit. Thus, the display device provides uniform brightness and color.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit under 35 U.S.C. § 119(a) of Korean Patent Application No. 2005-0117056, filed on Dec. 2, 2005, in the Korean Intellectual Property Office, the entire disclosure of which is hereby incorporated by reference.  
       BACKGROUND OF INVENTION  
       [0002]     1. Field of Invention  
         [0003]     The present invention relates to a display device and control method thereof. More particularly, the present invention relates to a display device having a uniform brightness by controlling an arrangement of light emitting diodes of a light source unit.  
         [0004]     2. Description of the Related Art  
         [0005]     A display device of a projection type comprises a light source unit emitting light, a micro display unit projecting an image beam by using the light of the light source unit, a reflection mirror reflecting an image beam, and a screen displaying an image by using the image beam.  
         [0006]     A lamp generating a depolarized white beam has been widely used as a light source of the light source unit, but recently, a light emitting diode having an excellent color reviving rate is also widely used.  
         [0007]     The light emitting diode comprises a red light emitting diode, a green light emitting diode, and a blue light emitting diode. A red light, green light and blue light generated from the light emitting diode are supplied for a micro display unit.  
         [0008]     However, the light emitting diode has a limitation, in which a light emitting characteristic, such as brightness, is not uniform due to special characteristics of a manufacturing process therefor. In the case that the light emitting diode having such a non-uniform light emitting characteristic is used, a problem exists in that screen brightness becomes non-uniform. Also, a problem exists in that the red light emitting diode, green light emitting diode, and blue light emitting diode respectively have an independent brightness distribution. As a result, screen color becomes non-uniform.  
         [0009]     Accordingly, there is a need for an improved display device comprising an LED light source and a uniform brightness and color.  
       SUMMARY OF THE INVENTION  
       [0010]     An aspect of exemplary embodiments of the present invention is to address at least the above problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of exemplary embodiments of the present invention is to provide a display device having uniform brightness and color.  
         [0011]     The foregoing and/or other aspects of exemplary embodiments of the present invention can be achieved by providing a display device, that comprises a circuit board having a light emitting diode mounting area, a light source unit comprising a plurality of light emitting diodes mounted to the light emitting diode mounting area so that light emitting characteristics can be symmetrical around the center of the light emitting diode mounting area, a light uniformizing unit for creating a uniform light from the light emitting diodes, a micro display unit located in front of the light uniformizing unit, a projection lens unit located in front of the micro display unit, and a screen located in front of the projection lens unit.  
         [0012]     According to an aspect of exemplary embodiments of the present invention, the light source unit comprises a plurality of sub light sources emitting lights different in color each other, and the circuit board comprises a plurality of sub circuit boards spaced from each other. To at least one of the plurality of sub circuit board is mounted at least one of the plurality of sub light sources emitting light of the same color.  
         [0013]     According to an aspect of exemplary embodiments of the present invention, the light emitting characteristics comprise at least one of brightness and a main wavelength.  
         [0014]     According to an aspect of the present invention, the light emitting diodes are arranged in a matrix shape.  
         [0015]     According to an aspect of exemplary embodiments of the present invention, the sub circuit boards comprise three sub circuit boards, at least one of the sub circuit boards is arranged in parallel with a light incident face of the light uniformizing unit, and at least two of the sub circuit boards are arranged perpendicular to the light incident face of the light uniformizing unit.  
         [0016]     According to an aspect of exemplary embodiments of the present invention, the display device further comprises a dichroic mirror for reflecting light from the sub circuit board arranged at a predetermined angle to the light incident face of the light uniformizing unit onto the light incident face of the light uniformizing unit.  
         [0017]     According to an aspect of exemplary embodiments of the present invention, the light source unit comprises a plurality of sub light sources emitting lights having different colors, light emitting characteristics comprising color of the emitting lights, and at least two of the plurality of sub light sources mounted to the circuit board.  
         [0018]     According to an aspect of exemplary embodiments of the present invention, the circuit board is arranged to be in parallel with the light uniformizing unit.  
         [0019]     According to an aspect of exemplary embodiments of the present invention, the light uniformizing unit comprises a light tunnel, and a mounting area size suitable for the size of a light incident face of the light tunnel.  
         [0020]     According to an aspect of exemplary embodiments of the present invention, the micro display unit comprises a digital micro-mirror display (DMD).  
         [0021]     Other objects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     The above and other objects, features, and advantages of certain exemplary embodiments of the prevent invention will be more apparent from the following description taken in conjunction with the accompany drawings, in which:  
         [0023]      FIG. 1  schematically illustrates a display device according to an exemplary embodiment of the present invention.  
         [0024]      FIGS. 2   a ,  2   b , and  2   c  illustrate a light source unit in a display device according to an exemplary embodiment of the present invention.  
         [0025]      FIG. 3  illustrates a light tunnel in a display device according to an exemplary embodiment of the present invention.  
         [0026]      FIGS. 4   a  and  4   b  illustrate a brightness distribution in a light emitting face of a light tunnel.  
         [0027]      FIGS. 5, 6 ,  7 , and  8 , respectively, illustrate an arrangement of light emitting diodes in a display device according to an exemplary embodiment of the present invention.  
         [0028]      FIG. 9  illustrates a display device according to an exemplary embodiment of the present invention.  
         [0029]      FIG. 10  illustrates an arrangement of light emitting diodes in a display device according to an exemplary embodiment of the present invention. 
     
    
       [0030]     Throughout the drawings, the same drawing reference numerals will be understood to refer to the same elements, features, and structures.  
       DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
       [0031]     The matters defined in the description such as a detailed construction and elements are provided to assist in a comprehensive understanding of the embodiments of the invention. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. Also, descriptions of well-known functions and constructions are omitted for clarity and conciseness.  
         [0032]     First, a display device according to an exemplary embodiment of the present invention will be described as follows by referring to  FIGS. 1, 2 , and  3 .  
         [0033]     As shown in  FIG. 1 , a display device  1  comprises a light source unit  110 , a light tunnel  140  creating uniform light from the light source unit  110 , a micro display unit  160  forming an image beam by using the light, a projection lens unit  180  enlarging the image beam, and a screen  190  on which the beam is displayed as a picture.  
         [0034]     The light source unit  110  comprises a first sub light unit  110   a  supplying a red light, a second sub light source unit  110   b  supplying a green light, and a third sub light source unit  110   c  supplying a blue light.  
         [0035]     The second sub light source unit  110   b  is arranged in parallel with a light incident face  140   a  of the light tunnel  140 . The first sub light source unit  110   a  and the third sub light source unit  110   c  facing each other is perpendicularly disposed to the light incident face  140   a  of the light tunnel  140 .  
         [0036]     The first sub light source unit  110   a  will be described below by referring  FIGS. 2   a  to  2   c.    
         [0037]     The first sub light source unit  110   a  comprises a rectangular shape circuit board  111  and light emitting diodes  115 . In the circuit board  111 , a rectangular mounting area  111   a  is provided and six light emitting diodes  115  are mounted to the mounting area  111   a . The light emitting diodes  115  are arranged in a shape of a matrix 2×3. The light emitting diodes  115  are connected to each other in series as shown in  FIG. 2   b . All the light emitting diodes  115  of the first sub-light source unit  110   a  emit red lights.  
         [0038]     The light emitting diodes  115  are mounted to the circuit board  111  after being separately manufactured. Here, the light emitting diodes  115  having different brightness may be mounted in one circuit board  111 .  
         [0039]     As shown in  FIG. 2   c , the six light emitting diodes  115  mounted to the first sub light source unit  110   a  are divided into a first group I and a second group II according to their brightness. The first group I comprise two light emitting diodes of which the relative brightness is 90 to 100. The first group is positioned in the middle of the circuit board  111 . The second group II comprises four light emitting diodes of which relative brightness is somewhat low, for example, 50 to 80. The second group II surrounds the first group.  
         [0040]     With this configuration, a light emitting characteristic of the light emitting diodes  115  forms a point symmetry with respect to the center of a light emitting area thereof. Through the arrangement of the light emitting diodes  115 , uniform brightness can be obtained.  
         [0041]     The second sub light source unit  110   b  and the third sub light source unit  110   c  also have configurations similar to that of the first sub light source unit  110   a . However, the second sub light emitting unit  110   b  comprises the light emitting diodes  115  emitting green lights and the third sub light unit  110   c  comprises the light emitting diode  115  emitting blue lights.  
         [0042]     In front of each of the sub light source units  110   a ,  110   b , and  110   c , is positioned a collimating lens  121 . The light emitted from each of the sub light source units  110   a ,  110   b , and  110   c  proceeds perpendicularly to the circuit board  111  without being diffused by the collimating lens  121 .  
         [0043]     Between the second sub light source unit  110   b  and a first optical lens unit  130  are positioned a first dichroic mirror  125  and a second dichroic mirror  126 . The dichroic mirrors  125  and  126  are arranged forming an angle of 45° with respect to the light incident face  140   a  of the light tunnel  140 .  
         [0044]     The first dichroic mirror  125  reflects only the red light, and transmits the other color lights. The second dichroic mirror  126  reflects only the blue light, and transmits the other color lights.  
         [0045]     The red light emitted from the first sub light source unit  110   a  is reflected by the first dichroic mirror  125  to be directed to the first optical lens unit  130 . The green light emitted from the second sub light source unit  110   b  transmits both the dichroic mirrors  125  and  126 , and directs to the first optical lens unit  130 . The blue light emitted from the third sub light source unit  110   c  is reflected by the second dichroic mirror  126  and then directs to the first optical lens unit  130 .  
         [0046]     As described above, the lights emitted from all the sub-light source units  110   a ,  110   b , and  110   c  can be directed to the first optical lens unit  130 . The first optical lens unit  130  focuses and supplies the emitted lights for the light tunnel  140 . In order to embody a colored screen, as the respective sub light source units  110   a ,  110   b , and  110   c  are sequentially driven, the red light, the green light, and the blue light are sequentially supplied for the light tunnel  140 .  
         [0047]     The light tunnel  140  creates a uniform light from the lights. As shown in  FIG. 3 , the inner surface of the light tunnel  140  having a square cylindrical shape is made of a light reflecting material, similar to a mirror. The lights projected into the light tunnel  140  repeats reflecting in the internal side to form a light having a uniform brightness distribution, which is emitted from the light tunnel  140 .  
         [0048]     As shown in  FIG. 1 , the light emitted from the light tunnel  140  is reflected by the reflection mirror  170  via a second optical lens unit  150  and then directed to the micro display unit  160 . The micro display unit  160  comprises a digital micro-mirror display (DMD)  161  and controls the DMD  161  to form an image beam.  
         [0049]     In addition to certain exemplary embodiments of the present, the micro display unit  160  may comprise a liquid crystal display panel (LCDP) or a liquid crystal on silicon (LCOS).  
         [0050]     The image beam emitted from the micro display unit  160  is projected onto the screen  190  via a projection lens unit  180 . A fresnel lens, which improves a rectilinear property of the projected beam to increase a frontal brightness, may be formed in the screen  190 .  
         [0051]     A process of brightness that becomes uniform according to an exemplary embodiment of the present invention will be described below by referring to  FIGS. 4   a  and  4   b.    
         [0052]      FIGS. 4   a  and  4   b  illustrate a brightness distribution on the light exiting face  140   b  of the light tunnel  140 , and a brightness distribution by the light emitted from the light emitting diodes  115  in a position as shown in  FIG. 2   c.    
         [0053]      FIG. 4   a  illustrates brightness in a position according to line X-X in  FIG. 3 , and  FIG. 4   b  illustrates brightness in a position according to line Y-Y in  FIG. 3 .  
         [0054]     As shown in the figures, the brightness is relatively uniform along the line Y-Y position, whereas the brightness is not uniform along the line X-X position. That is, light from one of the light emitting diodes  115  is emitted from the light tunnel  140  non-uniformly.  
         [0055]     In  FIG. 4   a , the brightness of the light emitting diode  115  in an ‘f’ position is illustrated on the left thereof, and the brightness of the light emitting diode  115  in an ‘a’ position is illustrated on the right thereof. Here, if the light emitting diodes  115 , which are positioned in the ‘a’ position and the ‘f’ position according to an exemplary embodiment of the present invention, have the same brightness, the light emitting diodes  115  compensate for their brightness. Therefore, uniform light can be obtained from the light exiting face  140   b  of the light tunnel  140 .  
         [0056]     Turning to  FIG. 2   c , the light emitting diodes  115  having the same brightness are disposed symmetrically with respect to the center of the mounting area  111   a . That is, the light emitting diodes  115  mounted to a ‘b’ position and an ‘e’ position which are mutually symmetrical belong to a first group I, the light emitting diodes  115  mounted to the ‘a’ position and the ‘f’ position which are mutually symmetrical belong to a second group II. Also, the light emitting diodes  115  mounted to a ‘c’ position and a ‘d’ position, which are mutually symmetrical, belong to the second group II.  
         [0057]     Accordingly, lights from the light emitting diodes  115  in symmetrical positions compensate for each other to thereby generate a light having a uniform brightness.  
         [0058]      FIGS. 5 through 8  illustrate an arrangement of light emitting diodes in a display device according to an exemplary embodiment of the present invention.  
         [0059]     As shown in  FIG. 5 , in an exemplary embodiment of the present invention, the light emitting diodes  115  are divided into two groups according to their main wavelength. Alternatively, the light emitting diodes  115  may be divided in consideration of both the main wavelength and the brightness, and it may be considered that the main wavelength and the brightness have different weights.  
         [0060]     As shown in  FIG. 6 , in an exemplary embodiment of the present invention, the light emitting diodes  115  are divided into two groups according to their brightness. The first sub light source  110   a  comprises eight light emitting diodes  115  which are arranged in the shape of a matrix 2×4.  
         [0061]     As shown in  FIG. 7 , in an exemplary embodiment of the present invention, the light emitting diodes  115  are divided into four groups according to their brightness. The first sub light source  110   a  comprises twelve light emitting diodes  115  which are arranged in the shape of a matrix 3×4.  
         [0062]     As shown in  FIG. 8 , in an exemplary embodiment of the present invention, the light emitting diodes  115  are divided into five groups according to their brightness. The first sub light source  110   a  comprises fifteen light emitting diodes  115  which are arranged in the shape of a matrix 3×5.  
         [0063]     In the above exemplary embodiments, the light emitting diodes  115  having the same light emitting characteristics are arranged symmetrically with respect to the center of the mounting area  111   a . Accordingly, a uniform light can be obtained from the light exiting face  140   b  of the light tunnel  140 .  
         [0064]     In the above exemplary embodiments of the present invention, the mounting area  111   a  has a rectangular shape, but may be variously changed into a triangular shape, a round shape or the like.  
         [0065]     Hereinafter, a display device according to an exemplary embodiment of the present invention will be described by referring to  FIGS. 9 and 10 .  
         [0066]     In a display device  2  according to an exemplary embodiment of the present invention, the light source unit  110  comprises a singular sub light source unit  110   d . Six light emitting diodes  115  are positioned in the light source  110 . The light emitting diodes  115  comprise a pair of first sub light emitting diodes  115   a  emitting a red light, a pair of second sub light emitting diodes  115   b  emitting a green light, and a pair of third sub light emitting diodes  115   c  emitting a blue light. Here, the pair of first sub light emitting diodes  115   a  is symmetrically arranged with respect to the center of a mounting area, and the pair of second sub light emitting diodes and the pair of third sub light emitting diodes  115   c  are symmetrically arranged around the center thereof.  
         [0067]     The light from the light exiting face  140   a  of the light tunnel  140  must have uniform brightness and color. For example, as non-uniform color, compared with non-uniform brightness, is easily recognized by a user. According to an exemplary embodiment of the present invention, as the sub-light emitting diodes  115   a ,  115   b , and  115   c  compensate for mutual colors, a uniform colored beam can be obtained.  
         [0068]     The display device  2  may not be provided with the first optical lens unit  130  as necessary. In an exemplary implementation, the light source unit  110  may be arranged in contact with the light incident face  140   a  of the light tunnel  140 , and the mounting area of the circuit board  111  may be provided to have a size to be suitable for the light incident face  140   a  of the light tunnel  140 .  
         [0069]     As described above, a display device according to an exemplary embodiment of the present invention provides uniform brightness and color.  
         [0070]     While the invention has been show and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.