Abstract:
An image projection apparatus including a light source for emitting a plurality of monochromatic color beams having different wave lengths; a first light transmit unit; a light switch unit having a plurality of mirrors for selectively deflecting the monochromatic color beams at a predetermined angle; a quadrangular beam generating unit for converting the reflected monochromatic color beams into quadrangular beams having certain ratios of length to height; a panel for receiving the converted quadrangular beams and forming a monochromatic color bar on at least one portion of upper, mid, and lower portions thereof; and a projection lens unit disposed opposite to the panel. Accordingly, by using the light switches, a monochromatic color bar is formed on single panel with the same utilization efficiency of light as that of three panels, thereby embodying a high image quality.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image projection apparatus, and more particularly, to an image projection apparatus for forming red (R), green (G), and blue (B) color bars on a single panel using light switches arranged in the structure of square matrix. This Application claims priority from Korean Patent Application No. 2002-0018095, filed Apr. 2, 2002, which is incorporated in full herein by reference. 
     2. Description of the Prior Art 
     A projector or a projection system displays an image by projecting an inputted image signal onto a screen. Such a display device is used to aid in a presentation at a meeting, or used in places such as a theater or home. 
     A conventional method used in order to realize a wide vision in the display device is magnifying an image displayed on a Liquid Crystal Display (LCD), a Cathode Ray Tube (CRT) or some such other display with a lens and projecting the image onto a screen. However the conventional method may be advantageous in achieving the wide vision, yet it is relatively weak in guaranteeing a clear image quality. In order to solve this problem, an image projection apparatus employing a Digital Micromirror Device (DMD) panel has been suggested. 
     The DMD is a semiconductor light switch using a micro drive mirror, i.e. micromirror. This micromirror controls a deflection of light according to an inputted image signal. In the DMD according to a digital method, a reproduction of color of the image signal is excellent and also a contrast between light and shade is clear. Since the DMD does not require A/D·D/A conversion, a clear image can be obtained. Also, since there is no loss of light that is caused by a polarizing filter, the DMD can obtain large amount of light output. 
     FIG. 1 is a view showing a basic structure of a conventional image projection apparatus using a color wheel. 
     Referring to FIG. 1, the conventional image projection apparatus  100  using a conventional color wheel comprises a light source  110 , a color wheel  120 , a DMD panel  130 , and a projection lens  140 . A light path of white light is indicated by one-dotted line in FIG.  1 . 
     The light source  110  emits the white light using an arc lamp or a laser beam. The color wheel  120  is rotated by a rotation driver in an arrowed direction of FIG.  1  and has R (red), G (green), and B (blue) regions. 
     The white light emitted from the light source  110  is subdivided into R.G.B. beams by the R.G.B. regions. 
     The DMD panel  130  comprises a plurality of micromirrors  130   a . The R.G.B. beams divided according to the respective wavelengths are projected onto the DMD panel  130  and then deflected from the micromirrors  130   a . The deflected R.G.B. beams penetrate the projection lens  140  and are formed on the screen as an image. 
     The conventional image projection apparatus  100  can process response signals with respect to the divided R.G.B. beams rapidly due to the presence of the individually operated micromirror  130   a . That is, with a simplified structure, excellent quality of color image can be realized. 
     However, when a color filter such as the color wheel  120 , and the DMD panel  130  are used to form an image, the DMD panel  130  uses only ⅓ amount of the white light emitted from the light source  110 . For example, with respect to the R region of the color wheel  120 , the R beam penetrates the color wheel  120 , while the G and B beams are blocked by the color wheel  120  and discarded. This phenomenon occurs with respect to the G and B beams. 
     Accordingly, since only ⅓ amount of the incident white light is used in the color filtering method, a brightness of the image is reduced to ⅓. That is, since the amount of white light emitted from the light source  100  is reduced while penetrating the color wheel  120 , light efficiency deteriorates and optimal brightness of the image cannot be obtained. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an image projection apparatus capable of enhancing the use of light that is decreased to ⅓ at a single panel, by using a high reflective mirror. 
     The above object of the present invention is achieved by providing an image projection apparatus comprising: a light source for emitting a plurality of monochromatic color beams having different wave lengths; a first light transmit unit having a plurality of optical fibers which the respective monochromatic color beams pass through; a light switch unit having a plurality of mirrors for selectively deflecting the monochromatic color beams at a predetermined angle; a quadrangular beam generating unit for converting the reflected monochromatic color beams into quadrangular beams having certain ratios of length to height; a single panel for receiving the converted quadrangular beams and forming a monochromatic color bar on at least one portion of upper, mid, and lower portions thereof; and a projection lens unit disposed opposite to the single panel. 
     More specifically, the light switch unit comprises a plurality of output ports disposed at output terminals thereof, for outputting the monochromatic color beams. The monochromatic color beam deflected from a first mirror among the plurality of mirrors is output through an output port corresponding to the first mirror. The image projection apparatus further comprises a second light transmit unit having a plurality of optical fibers for transmitting the monochromatic color beam output from the output port into the quadrangle beam generating unit. 
     The mirror comprises: a deflection mirror having one deflection surface; and a drive unit for driving the deflection mirror such that the defection mirror varies from a first position to a second position, the reflection mirror at the first position deflects the monochromatic color beams to any one of the upper, mid, and lower portions of the panel, the reflection mirror at the second position allows the monochromatic color beams to pass therethrough. 
     The light switch unit has the mirrors arranged according to a square matrix structure of (n×n), with n being a positive number greater than or equal to 3. The light switch unit is operated such that only one mirror is positioned at the first position with respect to one row and one column. The mirrors are Micro Electro Mechanical System (MEMS) mirrors. 
     Each of the (n×n) mirrors is positioned at the first position at least one time by a predetermined order to realize one image. The n equals the number of monochromatic color beams of different wavelengths emitted from the light source. A predetermined order comprises an illumination sequence of n light illuminations. 
     And during one sequence, each of the upper, mid, and lower portions of the panel receives at least one illumination from each of the monochromatic color beams of different wavelengths emitted from the light source. 
     The panel is a Digital Micromirror Device (DMD) for modulating the plurality of the monochromatic color bars into a digital signal and deflecting the signal to the projection lens unit. The projection lens unit concentrates the incident beams from the panel and projects the beam onto a display device. 
     The above object of the present invention is achieved by providing an image projection apparatus comprising: light source means for emitting a plurality of monochromatic color beams having different wave lengths; light switch means having a plurality of mirrors for selectively deflecting the monochromatic color beams at a predetermined angle; quadrangular beam generating means for converting the reflected monochromatic color beams into quadrangular beams having certain ratios of width to height; and panel means for receiving the converted quadrangular beams by formation of a monochromatic color bar on at least one of an upper, mid, and lower portion thereof. 
     More specifically, the light switch means has the plurality of mirrors arranged according to a square matrix structure of (n×n), with n being a positive integer greater than or equal to 3 
     According to the present invention, the R.G.B color bars are formed by using light switches arranged in the structure of square matrix of 3×3, thereby improving the utilization efficiency of the light. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objects and features of the present invention will become more apparent by description of preferred embodiments of the present invention with reference to the accompanying drawings, in which: 
     FIG. 1 is a view showing a basic structure of a conventional image projection apparatus using a color wheel; 
     FIG. 2 is a view showing a basic structure of an image projection apparatus according to the preferred embodiment of the present invention; 
     FIG. 3 is a view showing a basic structure of light switches employed in an image projection apparatus according to the present invention; 
     FIGS. 4A through 4C are views showing one image formed as the light switches are manipulated by a predetermined order according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Hereinafter, the present invention will be described in greater detail with reference to the accompanying drawings. 
     FIG. 2 is a view showing a basic structure of an image projection apparatus according to the preferred embodiment of the present invention. 
     Referring to FIG. 2, an image projection apparatus  200  according to the present invention comprises a light source  210 , a first light transmit unit  220 , a light switch unit  230 , a second light transmit unit  230 , a quadrangular beam generating unit  250 , a single panel(or one panel)  260  and a projection lens unit  270 . 
     In the present embodiment, the image projection apparatus  200  has the light switches arranged in the matrix structure of (3×3). Light paths of respective R.G.B. laser beams in the light switch unit  230  are respectively illustrated. For example, a light path of the R laser beam, which is deflected from a predetermined light switch  230   a  and inputted into a first output port  232   a , is indicated by a dotted line. 
     The light source  210  emits a plurality of monochromatic color beams having different wave-lengths. The light source  210  uses a laser beam, an arc lamp, a metal halide lamp, a halogen lamp or a xenon lamp, or any such light source suitable for performing as required for the present invention. The present invention uses the laser beam by way of an example. The plurality of monochromatic color beams (hereinbelow, called “laser beams”) are, for example, red (R), green (G), and blue (B) laser beams. 
     The first light transmit unit  220  has a plurality of first optical fibers  222   a ,  222   b ,  222   c  and a plurality of first collimating lenses  224   a ,  224   b , and  224   c . The first optical fibers  222   a ,  222   b , and  222   c  allow the respective R.G.B. laser beams to pass therethrough, and the first collimating lenses  224   a ,  224   b , and  224   c  concentrate the laser beams transmitted through the optical fibers  222   a ,  222   b ,  222   c . The first collimating lenses  224   a ,  224   b , and  224   c  are disposed at output ends of the first optical fibers  222   a ,  222   b , and  222   c . The laser beams concentrated at the first collimating lenses  224   a ,  224   b , and  224   c  are transmitted to the light switch unit  230 . 
     The light switch unit  230  comprises a plurality of light switches for deflecting the respective R.G.B. laser beams at a predetermined angle or allowing the R.G.B. laser beams to pass therethrough. The light switch unit  230  has a matrix structure of (n×n), wherein n is a positive number. In other words, the light switch unit  230  has the light switches  230   a  through  230   i  as many as (n×n). In this embodiment, the light switch unit  230  has nine (9) light switches  230   a  through  230   i  arranged in the square matrix of (3×3). 
     The light switches  230   a  through  230   i  use high reflective mirror embodied by utilizing Micro Electro Mechanical System (MEMS) Technology. The light switches  230   a  through  230   i  output the R.G.B. laser beams directly as the light signal without the process of converting an input light signal into an electric signal. Accordingly, the switching speed is faster than in the conventional method which requires the process of converting the light signal into the electric signal. 
     Each of the light switches  230   a  through  230   i  has a deflection mirror A and a drive unit B (FIG.  3 ). The deflection mirror A has a deflection surface formed on a side thereof, for deflecting the laser beams, and is fabricated by utilizing the MEMS technology. The position of the deflection mirror A is varied from a first position (on-position) to a second position (off-position) by the drive unit B. The first position (on-position) allows a laser beam (among the R.G.B. laser beams) to be deflected from the deflection mirror A to any one portion of upper, mid, and lower portions of the DMD panel  260 , while the second position (off-position) allows the R.G.B. laser beams to go straight and not be directed toward the panel  260 . 
     That is, the first position (on-position) is the state where the light switches  230   a  through  230   i  are inclined to deflect the laser beams to desired output ports  232   a ,  232   b , and  232   c . The second position (off-position) is the state where the light switches  230   a  through  230   i  are in parallel relation to the direction of the laser beams passing through the light switches  230   a  through  230   i.    
     Also the light switch unit  230  is operated such that only one light switch in a row and a column is positioned at the first position. The light switch unit  230  is operated such that the three light switches are simultaneously positioned at the first position or the (3×3) light switches  230   a  through  230   i  are positioned at the first position by a predetermined order. 
     For example, if a light switch  230   a  is positioned at the first position (on-position), the other light switches  230   b ,  230   c ,  230   d , and  230   g  disposed in the same row and column as the light switch  230   a  are positioned at the second position (off-position). At this time, if another light switch  230   e  is positioned at the first position, the light switch unit  230  sets another light switch  230   i  to be positioned at the first position. 
     One image is realized when each of the (3×3) light switches  230   a  through  230   i  is positioned at the first position at least one time. 
     At the output terminal of the light switch unit  230  are provided a plurality of output ports  232   a ,  232   b , and  232   c . The output ports  232   a ,  232   b , and  232   c  output the laser beams deflected from the light switches  230   a  through  230   i  of the light switch unit  230  into the second light transmit unit  240 . The second light transmit unit  240  has a plurality of second collimating lenses  242   a ,  242   b , and  242   c  and a plurality of second optical fibers  244   a ,  244   b ,  244   c . The second collimating lenses  242   a ,  242   b , and  242   c  concentrate the respective R.G.B. laser beams received through the output ports  232   a ,  232   b , and  232   c  to the respective second optical fibers  244   a ,  244   b , and  244   c . The second optical fibers  244   a ,  244   b , and  244   c  transmit the concentrated R.G.B. laser beams to the quadrangular beam generating unit  250 . 
     The quadrangular beam-generating unit  250  has a plurality of first lenses  252   a ,  252   b , and  252   c , a plurality of light tubes  254   a ,  254   b , and  254   c , and a second lens  256 . The quadrangular beam generating unit  250  is disposed at output ends of the second optical fibers  244   a ,  244   b , and  244   c , for converting the respective laser beams to a quadrangular beam. 
     The first lenses  252   a ,  252   b ,  252   c  disperse the respective R.G.B. laser beams such that the respective R.G.B. laser beams can be incident on the light tubes  254   a ,  254   b , and  254   c  corresponding to the first lenses  252   a ,  252   b , and  252   c . The light tubes  254   a ,  254   b , and  254   c  are shaped as a hexahedron and have passage holes formed therein. The respective light tubes  254   a ,  254   b , and  254   c  consist of four surfaces made of mirrors. When the laser beams dispersed from the first lenses  252   a ,  252   b , and  252   c  are incident in the passage hole defined in the light tube  254   a ,  254   b , and  254   c , the laser beams are converted to quadrangular beams that have a predetermined ratio of width to height. The second lens  256  disperses the quadrangular beams such that the beams are incident on the single panel  260 . 
     The single panel  260  consists of one digital micromirror device (DMD) panel or one liquid crystal display (LCD) panel. Hereinafter, the present invention using the DMD panel will be described. 
     The DMD panel  260  receives the monochromatic color beams i.e. the respective R.G.B. laser beams converted into the quadrangular beams to form the R.G.B. color bars on the upper, mid and lower portion thereof as shown in FIG.  2 . As shown in FIG. 2, R color bar is illustrated in an oblique line, G color bar in a vertical line, and B color bar in a reverse oblique line. 
     The DMD panel  260  has a plurality of drive mirrors. The drive mirrors digitalize the respective R.G.B. color bars formed on the DMD panel  260  and deflect them at a predetermined angle. The image deflected from the DMD panel  260  is projected onto a screen through the projection lens unit  270 . The projection lens unit  270  is disposed opposite the DMD panel  260 . 
     According to another embodiment of the present invention, the LCD panel can be used instead of the DMD panel. While DMD panel is a deflection type panel, the LCD panel is a projection type panel. When the LCD panel is used, the position of the projection lens and the screen can vary. 
     FIGS. 4A through 4C are views showing a process of realizing one image by a certain order of manipulation according to the preferred embodiment of the present invention. One image is realized by performing a series of processes as illustrated in FIGS. 4A through 4C. These processes can be changed without departing from the spirit of the invention. 
     Referring to FIGS. 4A and 4C, the R laser beam transmitted through the first light transmit unit  220  is incident on any one of the light switches  230   a  through  230   c  arranged in the first column, the G laser beam on any one of the light switches  230   d  through  230   f  arranged in the second column, and the B laser beam on any one of the light switches  230   g  through  230   i  arranged in the third column. 
     Also, the laser beams deflected from the light switches  230   a ,  230   d ,  230   g  of the first row form a color bar on the upper portion of the DMD panel  260  through the first output port  232   a , the laser beams deflected from the light switches  230   b ,  230   e , and  230   h  of the second row form a color bar on the mid portion of the DMD panel  260  through the second output port  232   a , and the laser beams deflected from the light switches  230   c ,  230   f , and  230   i  of the third row form a color bar on the lower portion of the DMD panel  260 . 
     These three monochromatic color bars are formed on the upper, mid, and lower portions of the DMD panel  260  by manipulating the light switch unit  230 . When the nine (9) light switches  230   a  through  230   i  of the light switch unit  230  are operated according to the following table 1, the color bars are formed on the DMD panel  260  as shown in FIG.  4 A. 
     
       
         
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Port 1 
                 Port 2 
                 Port 3 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 RED 
                 230a: ON 
                 230b: OFF 
                 230c: OFF 
               
               
                   
                 GREEN 
                 230d: OFF 
                 230e: ON 
                 230f: OFF 
               
               
                   
                 BLUE 
                 230g: OFF 
                 230h: OFF 
                 230i: ON 
               
               
                   
                   
               
             
          
         
       
     
     In the table 1, ‘ON’ corresponds to the first position that allows the laser beams to be deflected, and ‘OFF’ corresponds to the second position that allows the laser beams to pass through the light switches. Reference numerals  230   a  through  230   i  indicate the light switches. If the light switch unit  230  manipulates the light switches  230   a  through  230   i  according to table 1, the color bars are formed on the DMD panel  260  as shown in FIG.  4 A. That is, the R color bar is formed at the upper portion, the G color bar at the middle portion, and the B color bar at the lower portion. 
     Also, when the nine light switches  230   a  through  230   i  of the light switch unit  230  are operated according to the following table 2, the color bars are formed on the DMD panel  260  as shown in FIG. 4B 
     
       
         
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Port 1 
                 Port 2 
                 Port 3 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 RED 
                 230a: OFF 
                 230b: ON 
                 230c: OFF 
               
               
                   
                 GREEN 
                 230d: OFF 
                 230e: OFF 
                 230f: ON 
               
               
                   
                 BLUE 
                 230g: ON 
                 230h: OFF 
                 230i: OFF 
               
               
                   
                   
               
             
          
         
       
     
     In the table 2, ‘ON’ corresponds to the first position that allows the laser beams to be deflected, and ‘OFF’ corresponds to the second position that allows the laser beam to pass through the light switches. Reference numerals  230   a  to  230   i  indicate the light switches. If the light switch unit  230  is operated according to the table 2, the color bars are formed on the DMD panel  260  as shown in FIG.  4 B. That is, the B color bar is formed at the upper portion, R color bar at the mid portion, and G color bar at the lower portion. 
     Also, when the nine light switches  230   a  through  230   i  of the light switch unit  230  are operated according to the following table 3, the color bars are formed on the DMD panel  260  as shown in FIG.  4 C. 
     
       
         
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 Port 1 
                 Port 2 
                 Port 3 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 RED 
                 230a: OFF 
                 230b: OFF 
                 230c: ON 
               
               
                   
                 GREEN 
                 230d: ON 
                 230e: OFF 
                 230f: OFF 
               
               
                   
                 BLUE 
                 230g: OFF 
                 230h: ON 
                 230i: OFF 
               
               
                   
                   
               
             
          
         
       
     
     In the table 3, ‘ON’ corresponds to the first position that allows the laser beams to be deflected, and ‘OFF’ corresponds to the second position that allows the laser beam to pass through the light switches. Reference numerals  230   a  through  230   i  indicate the light switches. If the light switch unit  230  is operated according to the table 3, the color bars are formed on the DMD panel  260  as shown in FIG.  4 C. That is, the G color bar is formed at the upper portion, B color bar at the mid portion, and R color bar at the lower portion. 
     According to the image projection apparatus, by forming monochromatic color bars on the panel sequentially using the light switches that utilize the MEMS technology, the use of light on the panel can be improved. That is, the light switches make it possible to achieve the efficient use of light of the three panels. Accordingly, the brightness of the formed image can be improved. Also, since the light switches output the light signal directly without the process of converting the light signal into the electric signal, the on/off switching speed increases. 
     The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. The description of the present invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures.