Abstract:
Disclosed herein is a color display apparatus using a one-panel diffractive-type optical modulator. The color display apparatus includes a plurality of light sources, an illumination lens system, a diffractive-type optical modulator, a filter system, and a projection system. The light sources simultaneously emit the light beams of corresponding wavelengths. The illumination lens system allows respective light beams to be converted into linear parallel light. The diffractive-type optical modulator forms diffractive light by diffracting incident light when the locations of at least two neighboring reflection parts vary to a predetermined distance by an actuating means. The filter system allows diffractive light having a desired diffractive order for respective wavelengths to pass therethrough when diffractive light having a plurality of diffractive orders for the respective wavelengths enters from the diffractive-type optical modulator. The projection system generates an image on a target object by scanning diffractive light filtered by the filter system on the target object.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to a color display apparatus and, more particularly, to a color display apparatus using a one-panel diffractive-type optical modulator that is capable of forming diffractive light for incident light having a plurality of wavelengths using a single optical modulation device. 
   2. Description of the Related Art 
   With the development of micro technology, so-called micro Electro Mechanical Systems (MEMS) devices and small-sized equipment in which the MEMS devices are assembled have attracted significant attention. 
   A MEMS device is a device in which an actuation body which is formed on a substrate, such as a silicon substrate or a glass substrate, in a micro-structure form and configured to output mechanical actuation force, and a semiconductor Integrated Circuit (IC) that is configured to control the actuation body are electrically and mechanically combined. The MEMS device is basically characterized in that the actuation body having a mechanical structure is a part of the device, and the operation of the actuation body is electrically performed using Coulomb&#39;s force between electrodes. 
     FIG. 1  is a view showing the construction of a Grating Light Valve (GLV) device that Silicon Light Machine (SLM) Inc. has developed as a light intensity conversion device for a laser display, that is, an optical modulator. 
   The GLV device  21 , as shown in  FIG. 1 , is configured such that a common substrate-side electrode  23  is formed on an insulation substrate  22 , such as a glass substrate, a plurality of beams  24 , for example, six beams  241 ,  242 ,  243 ,  244 ,  245  and  246  in the present invention, that cross the common substrate-side electrode  23 , are installed in a bridge form, and are arranged in parallel. 
   The beams  24 , each of which is formed of a bridge member  25  and a combined reflective layer and actuation-side electrode  26  mounted on the bridge member  25 , are parts that are collectively called ribbons. 
   When minute voltage is applied between the substrate-side electrode  23  and the combined reflective layer and actuation-side electrodes  26 , the beams  24  approach the substrate-side electrode  23  due to the above-described electrostatic phenomenon. In contrast, when the application of voltage is stopped, the beams  24  move away from the substrate-side electrode  23  and are restored to their original positions. 
   The GLV device  21  alternately varies the heights of the combined reflective layer and actuation-side electrodes  26  due to the approach and separation operation of the plurality of beams  24  with respect to the substrate-side electrode  23  (that is, the approach and separation operation of alternate beams), and modulates the intensity of light reflected from the actuation-side electrode  26  using the diffraction of light (one light spot is irradiated for all of the six beams  24 ). 
     FIG. 2A  is a diagram showing an example of a conventional one-panel optical apparatus using a GLV device as an optical modulation device to which a MEMS device is applied, or using a piezoelectric diffractive-type optical modulator. 
   Referring to  FIG. 2A , the conventional one-panel optical apparatus includes a light source system  50 , a light condensing unit  52 , an illumination lens system  54 , a flat-type color wheel  57 , a GLV device  58 , a Fourier filter system  59 , a projection system  62 , and a screen  65 . 
   The light source system  51  is formed of a plurality of light sources  51   a  to  51   c , and the light-condensing unit  52  is formed of a single reflective mirror  53   a  and a plurality of dichroic mirrors  53   b  and  53   c.    
   The plurality of light sources  51   a  to  51   c  includes, for example, a Red (R) light source  51   a , a Green (G) light source  51   b , and a Blue (B) light source  51   c . The light condensing unit  52  condenses a blue-colored light, a green-colored light and a red-colored light using the single reflective mirror  53   a  and a plurality of dichroic mirrors, so that a multi-beam is formed, therefore a single illumination system is constructed. 
   Subsequently, the illumination lens system  54  converts the condensed multi-beam into a linear parallel light beam, and causes the linear parallel light to enter into the GLV device  58  through the flat-type color wheel  57 . 
   In more detail, the flat-type color wheel  57  includes color filters that allow only light beams of the multi-beam corresponding to respective colors to pass therethrough, a coupler to which the color filters are attached, and a motor that is attached to the coupler and configured to generate rotational force. The flat-type color wheel  57  sequentially separates the colors of light beam from each other as the coupler and the color filters attached to the coupler in a flat form rotate according to the rotational velocity of the motor. 
   When a linear parallel light having a single wavelength enters from the flat-type color wheel  57 , the GLV device  58  forms diffractive light by performing optical modulation on the linear parallel light having the corresponding wavelength for the entering time, and causes the formed diffractive light to be incident on the Fourier filter system  59 . 
   It is preferred that the Fourier filter system  59  be composed of a Fourier lens  60  and a dichroic filter  61 . The Fourier filter system  59  separates the diffractive light according to order and passes only desired orders of diffractive light therethrough. 
   Meanwhile, the projection system  62  includes a scanner  63  and a projection lens  64 , and projects the entering diffractive light onto the screen  65 . 
     FIG. 2B  is a diagram showing an example of a conventional three-panel optical apparatus using a GLV device as an optical modulation device to which a MEMS device is applied, or using a piezoelectric diffractive-type optical modulator. In the present example, a case where the optical apparatus is applied to a laser display is described 
   The laser display  51  related to the present example is used as, for example, a large-sized screen projector and, in particular, a digital image projector or the image projection apparatus of a computer. 
   The laser display  51 , as shown in  FIG. 2B , include laser light sources  52 R,  52 G and  52 B, respectively provided with R, G and B colors, mirrors  54 R,  54 G and  54 B respectively installed on the optical axes of the laser light sources, color illumination optical systems (lens group)  56 R,  56 G and  56 B, and GVL devices  58 R,  58 G and  58 B. 
   The laser light sources  52 R,  52 G and  52 B, for example, emit an R laser beam (having a wavelength of 642 nm and an optical output of about 3 W), a G laser beam (having a wavelength of 532 nm and an optical output of about 2 W), and a B laser beam (having a wavelength of 457 nm and an optical output of about 1.5 W), respectively. 
   Furthermore, the laser display  51  includes a color synthesizing filter  60  for synthesizing the R, G and B laser beams whose intensities of light are respectively modulated by the GVL devices  58 R,  58 G and  58 B, a spatial filter  62 , a diffuser  64 , a mirror  66 , a Galvano-scanner  68 , a projection optical system (lens group)  70 , and a screen  72 . The color synthesizing filter  60  includes, for example, a dichroic mirror. 
   In the laser display  51  of the present example, RGB laser beams emitted from the laser light sources  52 R,  52 G and  52 B respectively pass through the mirrors  54 R,  54 G and  54 B, and are respectively incident on the GVL devices  58 R,  58 G and  58 B of the color illumination optical systems  56 R,  56 G and  56 B. The laser beams are color-separated video signals, and are input to the GVL devices  58 R,  58 G and  58 B in a synchronized manner. 
   Furthermore, the respective laser beams are diffracted by the GVL devices  58 R,  58 G and  58 B, thus being spatially modulated. These tri-color diffractive light beams are synthesized by the color synthesizing filter  60  and then only signal components are extracted by the spatial filter  62 . 
   Thereafter, the RGB video signals experience a decrease in the laser spectrum thereof by the diffuser  64 , are emitted on a space by the Galvano-scanner  68  that is synchronized with video signals through the mirror  66 , and are projected in full-color image form onto the screen  72  by the projection optical system  70 . 
   Meanwhile, as described above, the one-panel-type optical apparatus has a simple structure, reduces cost, and enables the realization of the optical system. However, the one-panel-type optical apparatus is problematic in that the optical modulator used requires operation velocity three times faster than that of an existing modulator and, therefore, the life span thereof is reduced by ⅓. Furthermore, the one-panel-type optical apparatus is problematic in that light efficiency is lowered because a color wheel is necessary. 
   Furthermore, the three-panel-type optical apparatus is problematic in that the optical systems thereof are complicated and the cost thereof increases because optical modulators are provided so as to correspond to respective colors of laser light sources. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a color display apparatus using a one-panel diffractive-type optical modulator which is capable of forming diffractive light for incident light having a plurality of wavelengths using a single optical modulator. 
   In order to accomplish the above object, the present invention provides a color display apparatus using a one-panel diffractive-type optical modulator, including a plurality of light sources for simultaneously emitting the light beams of corresponding wavelengths; an illumination lens system for allowing respective light beams, which are emitted from the plurality of light sources, to be converted into linear parallel light and simultaneously enter, a diffractive-type optical modulator comprising a substrate, a plurality of reflecting parts arranged to form an array, configured such that center portions of the plurality of reflection parts are spaced apart from the substrate and surfaces of the plurality of reflection parts oppose the substrate reflect incident light, and configured to be supported by the substrate, and an actuating means for moving the center portions of the plurality of reflection parts so as to become away from or approach the substrate, the diffractive-type optical modulator forming diffractive light by diffracting incident light when the locations of at least two neighboring reflection parts vary to a predetermined distance by the actuating means, and the reflecting parts simultaneously emitting diffractive light having a plurality of wavelengths by allowing the plurality of reflective units to generate and emit diffractive light for the incident light of respective assigned wavelengths when the wavelengths of the incident light to have to be modulated by the plurality of reflective unit are assigned and linear parallel light having different wavelengths different enters simultaneously, a filter system for allowing diffractive light having a desired diffractive order for respective wavelengths to pass therethrough when diffractive light having a plurality of diffractive orders for the respective wavelengths enters from the diffractive-type optical modulator, and a projection system for generating an image on a target object by scanning diffractive light filtered by the filter system on the target object. 
   In addition, the present invention provides A color display apparatus using a one-panel diffractive-type optical modulator, including a plurality of light sources for simultaneously emitting the light beams of corresponding wavelengths; an illumination lens system for converting the light beams, which are emitted from the plurality of light sources, into linear parallel light and causing the converted light to enter, a diffractive-type optical modulator comprising a substrate, a plurality of first reflection parts arranged to form an array, configured such that center portions of the plurality of first reflection parts are spaced apart from the substrate and have one or more one holes so that surfaces of the plurality of first reflection parts oppose the substrate reflect incident light and the incident light is passed therethrough, and configured to be supported by the substrate, a second reflection part configured to be located between the first reflection parts and the substrate, to be spaced apart from the first reflection parts, and to reflect incident light that passes through one or more open holes of the first reflection parts, and an actuating means for moving the center portions of the plurality of reflection parts so as to vary distances to the second reflection parts and varying the amount of diffractive light formed by reflective light of the first and second reflection parts, the diffractive-type optical modulator forming diffractive light by diffracting incident light when the locations of at least two neighboring first reflection parts vary to a predetermined distance with respect to those of the second reflection parts by the actuating means, and emitting diffractive light having a plurality of wavelengths by allowing the plurality of first reflective unit to generate and emit diffractive light for incident light of assigned wavelengths when the wavelengths of the incident light to have to be modulated by the plurality of first reflective units are assigned and linear parallel light having different wavelengths enters simultaneously, a filter system for passing diffractive light having a desired diffractive order for respective wavelengths therethrough when diffractive light having a plurality of diffractive orders for the respective wavelengths enters from the diffractive-type optical modulator, and a projection system for generating an image on a target object by scanning diffractive light filtered by the filter system on the target object 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and 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 view showing the construction of a GLV device that SLM Inc. has developed as a light intensity conversion device for a laser display, that is, an optical modulator, 
       FIG. 2A  is a diagram showing an example of a conventional one-panel optical apparatus using a GLV device as an optical modulation device to which a MEMS device is applied, or using a piezoelectric diffractive-type optical modulator, 
       FIG. 2B  is a diagram showing an example of a conventional three-panel optical apparatus using a GLV device as an optical modulation device to which a MEMS device is applied, or using a piezoelectric diffractive-type optical modulator, 
       FIG. 3A  is a perspective view of a recess and diffractive-type optical modulator that is applied to the present invention; 
       FIGS. 3B and 3C  are sectional views taken along line A-A′ of  FIG. 3A , which show examples of the construction of a one-panel diffractive-type optical modulator according to the present invention; 
       FIG. 4A  is a perspective view of an open hole-based diffractive-type optical modulator that is applied to the present invention; 
       FIGS. 4B and 4C  are sectional views taken along line B-B′ of  FIG. 4A , which show examples of the construction of the one-panel diffractive-type optical modulator according to the present invention; 
       FIG. 5  is a diagram showing the construction of a color display apparatus using the one-panel diffractive-type optical modulator of  FIGS. 4A and 4B ; and 
       FIG. 6  is a conceptual diagram illustrating the incident light of a color display apparatus using the one-panel diffractive-type optical modulator of  FIGS. 4A and 4C . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Now, a color display apparatus using a one-panel diffractive-type optical modulator according to a preferred embodiment of the present invention is described in detail with reference to the accompanying drawings. 
     FIG. 3A  is a perspective view of a recess and diffractive-type optical modulator that is applied to the present invention.  FIGS. 3B and 3C  are sectional views taken along line A-A′ of  FIG. 3A , which show examples of the construction of the one-panel diffractive-type optical modulator according to the present invention. 
   The one-panel diffractive-type optical modulator refers to a device for performing optical modulation on a plurality of wavelengths using a single diffractive-type optical modulator. 
   That is, in general three-panel diffractive-type optical modulator, in the case where a color display apparats is desired to be implemented using R, G and B colors, three diffractive-type optical modulator that can modulate respective colors of wavelengths are necessary. However, if the one-panel diffractive-type optical modulator is used, the color display apparatus can be implemented only using the one-panel diffractive-type optical modulator. 
   Referring to  FIG. 3A , the one-panel diffractive-type optical modulator that is applied to the present invention includes a silicon substrate  60 , and a plurality of elements  62   a  to  62   n.    
   In this case, the plurality of elements  62   a  to  62   n  may constitute a one-panel diffractive-type optical modulator by being uniformly arranged with the same width. Furthermore, the plurality of elements  62   a  to  62   n  may constitute a one-panel diffractive-type optical modulator by being alternately arranged with different widths from each other. 
   The plurality of elements  62   a  to  62   n  can diffract incident light only when they include at least two elements (for example  62   a  and  62   b ). That is, when the wavelength of light entering into one element (for example, the element  62   a ) and another element (for example, the element  62   b ) neighboring the element  62   a  is defined as λ and a difference in height is a multiple of λ/4, incident light is diffracted and, therefore, diffractive light having a plurality of orders is formed. The formed diffracted light corresponds to a single pixel on a screen. 
   Accordingly, at least two elements (for example, the elements  62   a  and  62   b ) are necessary to constitute one pixel. In order to increase the intensity of diffractive light, four elements (for example, the elements  62   a  to  62   d ) may constitute one pixel, eight elements (for example, the elements  62   a  to  62   h ) may constitute one pixel, or twelve elements (for example the elements  62   a  to  62   l ). 
   Meanwhile, a case where two elements, which are a minimal unit of elements, constitute one pixel to implement the one-panel diffractive-type optical modulator of the present invention is described as an example with reference to  FIGS. 3A and 3B . The one-panel diffractive-type optical modulator alternately performs optical modulation on a two-element basis in a one direction (in a rightward direction). For example, the optical modulation is performed in such a way that elements  62   a  and  62   b  perform optical modulation on an incident light beam having an R wavelength, elements  62   c  and  62   d  perform optical modulation on an incident light beam having an G wavelength, elements  62   e  and  62   f  perform optical modulation on an incident light beam having an B wavelength, and elements  62   g  and  62   h  perform optical modulation on an incident light beam having an R wavelength, and so on. 
   That is, the one-panel diffractive-type optical modulator of the present invention alternately performs optical modulation in the order of R, G and B on a two-element basis. 
   The one-panel diffractive-type optical modulator may be implemented such that elements corresponding to the number of all pixels necessary for displaying an image onto the screen perform optical modulation for a certain wavelength from one side, sequent elements corresponding to the number of all pixels necessary for displaying an image onto the screen perform optical modulation for another wavelength, and then sequent elements corresponding to the number of all pixels necessary for displaying an image onto the screen perform optical modulation for further wavelength. 
   A description related to this is given below with reference to  FIG. 3C . Elements ranging from reference numeral  62   a  to reference numeral  62 ( n /3) perform optical modulation for a certain wavelength, elements ranging from reference numeral  62 ( n /3+1) to reference numeral  62 ( 2   n /3) perform optical modulation for a G wavelength, and elements ranging from reference numeral  62 ( 2   n /3+1) to reference numeral  62   n  perform optical modulation for an incident light beam having a B wavelength. 
   That is, a general diffractive-type optical modulator is classified according to a block. A certain block performs optical modulation for a certain wavelength, a sequent block performs optical modulation for another wavelength, and a sequent block performs optical modulation for further wavelength. 
   The descriptions of the silicon substrate  60  and the elements  62   a  to  62   n  constituting the one-panel diffractive-type optical modulator are made below. 
   The silicon substrate  60  is provided with a recess to provide an air space for elements  62   a  to  62   n , an insulation layer  61  is disposed on the silicon substrate  60 , and the end portions of the elements  62   a  to  62   n  are attached beside the recess. 
   Each of the elements (although only a description of an element indicated by reference numeral  62   a  is representatively made, descriptions of the others  62   b  to  62   n  are the same) has a ribbon shape, and is provided with a lower support  63   a , the lower surfaces of both ends of which are attached beside the recess of the silicon substrate  60  such that the center portion of the element is spaced apart from the recess of the silicon substrate  60 , and a portion  67   a  of which can move upward and downward, the portion being located above the recess of the silicon substrate  60 . 
   Furthermore, the element  62   a  includes a lower electrode layer  64   a  disposed on the left end portion of the lower support  63   a  and configured to provide piezoelectric voltage, a piezoelectric material layer  65   a  disposed on the lower electrode layer  64   a  and configured to generate upward and downward drive forces due to contraction and expansion when voltage is applied to the two sides thereof, and a upper electrode layer  66   a  disposed on the piezoelectric material layer  65   a  and configured to provide piezoelectric voltage to the piezoelectric material layer  65   a.    
   Furthermore, the element  62   a  includes a lower electrode layer  64   a  disposed on the left end portion of the lower support  63   a  and configured to provide piezoelectric voltage, a piezoelectric material layer  65   a ′ disposed on the lower electrode layer  64   a ′ and configured to generate upward and downward drive forces due to contraction and expansion when voltage is applied to the two sides thereof and a upper electrode layer  66   a ′ disposed on the piezoelectric material layer  65   a ′ and configured to provide piezoelectric voltage to the piezoelectric material layer  65   a′.    
     FIG. 4A  is a perspective view of an open hole-based diffractive-type optical modulator that is applied to the present invention, and  FIGS. 4B and 4C  are sectional views taken along line B-B′ of  FIG. 4A , which show examples of the construction of the one-panel diffractive-type optical modulator according to the present invention. 
   Referring to  FIG. 4A , the open hole-based diffractive-type optical modulator that is applied to the present invention includes a silicon substrate  601 , an insulation layer  602 , a lower micromirror  603 , and a plurality of elements  610   a  to  610   n . In this case, although the insulation layer and the lower micromirror are formed on different layers, the insulation layer itself may function as the micromirror when the insulation layer has a characteristic of reflecting light lower. 
   The silicon substrate  601  is provided with a recess to provide an air space for the elements  610   a  to  610   n , an insulation layer  602  is disposed on the silicon substrate  501 , a lower micromirror  603  is deposited on the insulation layer  502 , and the lower surfaces of elements  610   a  to  610   n  are attached on the two sides of the recess. The silicon substrate  501  may be formed of a material, such as Si, Al2O3, ZrO2, Quartz or SiO2, and the bottom and top of the recess (in  FIG. 4A , indicated by dotted lines) may be formed of heterogeneous materials different from each other. 
   The lower micromirror  603  is deposited on the upper portion of the silicon substrate  601 , and causes incident light to be diffracted using reflection. The lower micromirror  603  may be formed of material such as metal (Al, Pt, Cr or Ag). 
   Each of the elements (although only a description of an element indicated by reference numeral  610   a  is representatively made, the others are the same) has a ribbon shape, and is provided with a lower support  611   a , the lower surfaces of both ends of which are attached on two sides beside the recess of the silicon substrate  601  such that the center portion of the element is spaced apart from the recess of the silicon substrate  601 . 
   Piezoelectric layers  620   a  and  620   a ′ are provided on the two sides of the lower support  611   a ′, and generate the drive force of the element  610   a  using the contraction and expansion of the piezoelectric layers  620   a  and  620   a′.    
   A material for forming the lower support  511   a  may be Si oxide-based material (for example, SiO 2 ), Si nitride-based material (for example, Si 3 N 4 ), a ceramic substrate (Si, ZrO 2 , or Al 2 O 3 ), Si carbide, or the like. The lower support  611   a  may be omitted according to need. 
   Furthermore, the left and right piezoelectric layers  620   a  and  620   a ′ include lower electrode layers  621   a  and  621   a ′ for providing piezoelectric voltage, piezoelectric material layers  622   a  and  622   a ′ disposed on lower electrode layers  621   a ,  621   a ′ and configured to generate upward and downward drive forces due to contraction and expansion when voltage is applied to the two sides thereof, and upper electrode layers  623   a  and  623   a ′ disposed on the piezoelectric material layers  622   a  and  622   a ′ and configured to provide piezoelectric voltage to the piezoelectric material layers  622   a  and  622   a ′. When voltage is applied to the upper electrode layers  623   a  and  623   a ′ and the lower electrode layers  621   a  and  621   a ′, the piezoelectric material layers  622   a  and  622   a ′ are contracted or expanded, thus causing the lower support  611   a  to move upward or downward. 
   The electrodes  621   a ,  621   a ′,  623   a  and  623   a ′ may be formed of an electrode material, such as Pt, Ta, Ni, Au, Al, or RuO 2 , and the electrode materials are deposited within a range of 0.01 to 3 μm using a sputter method, an evaporation method, or the like. 
   Meanwhile, an upper micromirror  630   a  is deposited on the center portion of the lower support  611   a , and a plurality of open holes  631   a   1  to  631   a   4  are formed thereon. In this case, although it is preferred that each of the open holes  531   a   1  to  531   a   4  be formed in a rectangular shape, they may be formed in any closed-curve shape, such as a circular shape or an oval shape. Furthermore, in the case where the lower support is formed of a light-reflective material, it is not necessary to separately deposit the upper micromirror, and it is possible to allow the lower support to function as the upper micromirror. 
   The open holes  631   a   1  to  631   a   4  allow light incident on the element  610   a  to pass through the element  610   a  and to be incident on the portions of the lower micromirror layer  603  corresponding to the open holes  631   a   1  to  631   a   4 , thus allowing the lower micromirror layer  603  and the upper micromirror layer  603   a  to form pixels. 
   That is, for example, portion (A) of the upper micromirror layer  630   a , through which the open holes  631   a   1  to  631   a   4  are formed, and portion (B) of the lower micromirror layer  603  may form a single pixel. 
   In this case, incident light, which has passed through the portion of the upper micromirror layer  603   a  through which the open holes  631   a   1  to  631   a   4  are formed, can be incident on the corresponding portion of the lower micromirror layer  603 . When the interval between the upper micromirror layer  630   a  and the lower micromirror layer  630  is an odd multiple of λ/4, maximally diffracted light is generated. 
   Meanwhile, an example of implementing the one-panel diffractive-type optical modulator of the present invention is described with reference to  FIGS. 4A and 4B . The one-panel diffractive-type optical modulator alternately performs optical modulation on two-element basis in one side direction (in a right direction). For example, reference numeral  610   a  performs optical modulation on an incident light beam having an R wavelength, reference numeral  610   b  performs optical modulation on an incident light beam having an G wavelength, reference numeral  610   c  performs optical modulation on an incident light beam having an B wavelength, and reference numeral  610   d  performs optical modulation on an incident light beam having an R wavelength. 
   That is, the one-panel diffractive-type optical modulator of the present invention alternately performs optical modulation in R, G and B order on two-element basis. 
   The one-panel diffractive-type optical modulator may be implemented such that elements corresponding to the number of all pixels necessary for displaying an image onto the screen perform optical modulation for a certain wavelength from one side, sequent elements corresponding to the number of all pixels necessary for displaying an image onto the screen perform optical modulation for another wavelength, and then sequent elements corresponding to the number of all pixels necessary for displaying an image onto the screen perform optical modulation for further wavelength. 
   A descriptions related to this is given below with reference to  FIGS. 4A and 4C . Elements ranging from reference numeral  610   a  to reference numeral  610 ( n /3) perform optical modulation for a certain wavelength, elements ranging from reference numeral  610 ( n /3+1) to reference numeral  610 ( 2   n /3) perform optical modulation for a G wavelength, and elements ranging from reference numeral  610 ( 2   n /3+1) to reference numeral  610   n  perform optical modulation for an incident light beam having a B wavelength. 
   That is, a general diffractive-type optical modulator is classified according to a block. A certain block performs optical modulation for a certain wavelength, a sequent block performs optical modulation for another wavelength, and a sequent block performs optical modulation for further wavelength. 
     FIG. 5  is a diagram showing the construction of a color display apparatus using the one-panel diffractive-type optical modulator of  FIGS. 4A and 4B . 
   Referring to  FIG. 5 , the color display apparatus using the one-panel diffractive-type optical modulator of  FIGS. 4A and 4B  includes a plurality of light sources  800   a  to  800   c , a plurality of front-end dichroic mirrors  801   a  to  801   c , an illumination lens system  810 , a reflective mirror  820 , an optical modulation system  830 , a Fourier filter system  840 , a projection system  850 , and a screen  860 . 
   The plurality of light sources  800   a  to  800   c  generate and emit light beams having wavelengths different from each other, and the plurality front-end dichroic mirrors  801   a  to  801   c  gather and emit the light beams having wavelengths different from each other. The section of each of the light sources  800   a  to  800   c  is a circular shape, and the profile of each of the light beams has Gaussian distribution. 
   The illumination lens system  810  converts incident light into linear parallel light and emits the converted light, and is composed of a cylinder lens  811  and a collimation lens  821 . 
   In this case, the cylinder lens  811  converts the incident light, which is emitted from the front-end dichroic mirrors  801   a  to  801   c , into a lateral direction of linear light Thereafter, the linear light is converted into parallel light through the collimation lens  821  and enters into a one-panel diffractive-type optical modulator  832 . 
   The collimation lens  821 , for example, includes a concave lens and a convex lens. 
   The reflective mirror  820  reflects incident light so that the incident light almost vertically enters to the one-panel diffractive-type optical modulator  832 . 
   The optical modulation system  830  includes a substrate  831 , a one-panel diffractive-type optical modulator  832  formed in a substrate  831 , a drive Integrated Circuit (IC)  833 , and converts incident light into diffractive light and emits the resulting diffractive light. 
   In this case, the one-panel diffractive-type optical modulator  832  performs optical modulation on the incident light having a plurality of wavelengths on a wavelength basis, and generates and emits the diffractive light having a plurality of diffractive orders for each light beam. 
   Thereafter, the diffractive light formed by the one-panel diffractive-type optical modulator  832  is formed of 0-order of diffractive light, ±1-order of diffractive light, and 1-order of diffractive light in a periodical direction. In this case, the diffractive light of incident light, having a long wavelength, is further diffracted and, as a result, −1-order of R diffractive light, −1-order of G diffractive light, −1-order of B diffractive light, 0-order of RGB diffractive light, +1-order of B diffractive light, +1-order of G diffractive light, and +1-order of R diffractive light are formed from one side. 
   In this case, when the diffraction grating period of elements is appropriately adjusted, a diffracted angle varies according to wavelength, so that, from left side, +1-order of R diffractive light, +1-order of G diffractive light, +1-order of B diffractive light, 0-order of RGB diffractive light, 1-order of B diffractive light, −1-order of G diffractive light, and −1-order of R diffractive light are not formed, but a single of −1-order of RGB diffractive light, 0-order of RGB diffractive light, and +1-order of RGB diffractive light are formed. 
   Meanwhile, the Fourier filter system  840  is composed of a Fourier lens  841  and a dichroic filter  842 , and selectively passes 0-order of diffractive light or ±1-order of incident diffractive light therethrough. 
   The projection system  850  is composed of a scanner  851  and a projection lens  852 , and projects incident diffractive light onto the screen  860 . That is, the projection system  850  performs a role of forming a pixel by focusing diffractive beams, each of which has a diffractive and which enters through the dichroic filter  842 , onto the screen  860 . 
   Meanwhile, in the one-panel diffractive-type optical modulator  832 , the drive IC  831  alternately performs sequential control so as to form diffractive light for R, G and B incident light from the left side or from the right side in response to a control signal received from the outside. That is, the drive IC  831  alternately performs optical modulation on incident light in order of R, G, B, R, G, B, R, G and B beams. 
   Besides, the drive IC  831  classifies the one-panel diffractive-type optical modulator  832  according to block. A first block may be implemented so as to perform optical modulation on R light, a second block may be implemented so as to perform optical modulation on G light, and a third block may be implemented so as to perform optical modulation on B light. In this case, the construction of the optical system may differ slightly from that of the optical system described in  FIG. 5 . 
     FIG. 6  is a conceptual diagram illustrating the incident light of a color display apparatus using the one-panel diffractive-type optical modulator of  FIGS. 4A and 4C , where a one-panel diffractive-type optical modulator in which blocks are classified according wavelength is used. 
   That is, the one-panel diffractive-type optical modulator may be implemented such that elements corresponding to the number of all pixels necessary for displaying an image onto the screen perform optical modulation for a certain wavelength from one side, sequent elements corresponding to the number of all pixels necessary for displaying an image onto the screen perform optical modulation for another wavelength, and then sequent elements corresponding to the number of all pixels necessary for displaying an image onto the screen perform optical modulation for further wavelength. 
   Accordingly, the incident light of the color display apparatus using the one-panel diffractive-type optical modulator, as shown in  FIG. 6 , may be implemented such that corresponding incident light (R linear parallel light, G linear parallel light, and B linear parallel light) enters into corresponding blocks (R block, G block, and B block). 
   A description related to this is given below with reference to  FIGS. 4A and 4C . Elements ranging from reference numeral  610   a  to reference numeral  610 ( n /3) perform optical modulation for a certain wavelength and R linear parallel light enters in this block interval, elements ranging from reference numeral  610 ( n /3+1) to reference numeral  610 ( 2   n /3) perform optical modulation for a G wavelength and G linear parallel light enters in this block interval, and elements ranging from reference numeral  610 ( 2   n /3+1) to reference numeral  610   n  perform optical modulation for an incident light beam having a B wavelength and B linear parallel light enters in this block interval. 
   As described above, in the case where the one-panel diffractive-type optical modulator in which blocks are classified according wavelength is used, it is not necessary to condense respective wavelengths of diffractive light. For this purpose, a light-condensing optical system is further necessary. Such a light-condensing optical system may be easily implemented by those skilled in the art. 
   Meanwhile, although descriptions of the color display apparatus are made herein, it can be easily understood that the present invention can be applied to different application printers that use a plurality of optical modulators corresponding to a plurality of wavelengths. 
   As described above, in accordance with the present invention, optical efficiency can be increased, and the construction of an optical system can be simplified. 
   Furthermore, a single modulator is used instead of a plurality of optical modulators, so that the cost of a product can be lowered, therefore the competitiveness of price of the product can be enhanced. 
   Furthermore, stacking of the drive IC can be facilitated. 
   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.