Abstract:
An image scanning apparatus for realizing an image on a screen includes: a spatial light modulator module for diffracting light beams having different wavelengths into relevant modes; and an iris for limiting light beams of modes except a mode of 0 th -order among the modes diffracted by the spatial light modulator module.

Description:
CLAIM OF PRIORITY 
   This application claims priority under 35 U.S.C. § 119 to an application entitled “Image Scanning Apparatus,” filed in the Korean Intellectual Property Office on Oct. 10, 2005 and assigned Ser. No. 2005-95072, the contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to an image scanning apparatus, and in particular, to a portable image scanning apparatus including a spatial modulator module. 
   2. Description of the Related Art 
   Recently, image scanning apparatuses using a laser light source, such as a semiconductor laser, have been suggested. Such an image scanning apparatus having a laser light source can be used in projectors, projector televisions, color scanners, and color printers. When the image scanning apparatus including a laser light source is used in projectors and projector televisions, the image scanning apparatus obtains an image on a screen. When the image scanning apparatus including a laser light source is used in color scanners and color printers, the image scanning apparatus reproduces an image on a drum. 
   The image scanning apparatus includes laser light sources, such as a semiconductor laser, for generating light beams having different visible wavelengths and a spatial light modulator for irradiating the light beams on each pixel according to the necessity. Various types of spatial light modulators are used for image scanning apparatuses. 
   For the spatial light modulators, diffraction gratings capable of modulating the characteristic of incident light are generally used. Examples of the diffraction gratings are: a planar grating light-valve (GLV) as a spatial light modulator described by David M. Bloom et al. in U.S. Pat. No. 5,459,610 issued Oct. 17, 1995; a grating electromechanical system (GEMS) described by Kowarz et al in U.S. Pat. No. 6,476,848 issued Jun. 25, 2002; an image scanning apparatus using a GLV is described by Paul K. Manhart et al. in U.S. Pat. No. 6,088,102 issued Jul. 11, 2000; and an image scanning apparatus using a GEMS is described by Kowarz et al. in U.S. Pat. No. 6,724,515 issued Apr. 20, 2004. 
   The above-described image scanning apparatus including a diffraction grating type spatial light modulator classifies incident light into a negative mode and a positive mode based on a mode of 0 th -order and uses the modes except the mode of 0 th -order. That is, a clear image can be realized by using the diffraction grating type spatial light modulator. 
   However, image scanning apparatuses are large and requires more power consumption, thus not an ideal for used as a portable device. In particular, a system configuration is complicated and bulkier to limit the mode of 0 th -order as a separate configuration must be further included, as described in U.S. Pat. No. 6,724,515 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to substantially solve at least the above problems and/or disadvantages and to provide additional advantages, by providing an image scanning apparatus that can be portable because of its compact size and less power consumption. 
   According to one aspect of the present invention, there is provided an image scanning apparatus comprising: a spatial light modulator module for diffracting light beams having different wavelengths into relevant modes; and an iris for limiting light beams of modes except a mode of 0 th -order among the modes diffracted by the spatial light modulator module. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which: 
       FIG. 1  is a configuration of an image scanning apparatus according to a first embodiment of the present invention; 
       FIG. 2  is a perspective view of a portion of the configuration of  FIG. 1 ; 
       FIGS. 3A and 3B  are graphs showing the magnitude of a spot of red light; 
       FIGS. 4A and 4B  are graphs showing the magnitude of a spot of blue light; 
       FIGS. 5A and 5B  are graphs showing the magnitude of a spot of green light; 
       FIG. 6  is a diagram for explaining a correlative non-spherical surface; 
       FIG. 7  is a configuration of an image scanning apparatus according to a second embodiment of the present invention; and 
       FIG. 8  is a configuration of an image scanning apparatus according to a third embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Embodiments of the present invention will be described herein below with reference to the accompanying drawings. In the drawings, the same or similar elements are denoted by the same reference numerals even though they are depicted in different drawings. For the purposes of clarity and simplicity, well-known functions or constructions are not described in detail as they would obscure the invention in unnecessary detail. 
     FIG. 1  is a configuration of an image scanning apparatus  100  according to a first embodiment of the present invention.  FIG. 2  is a perspective view of a portion of the configuration of  FIG. 1 . 
   Referring to  FIG. 1 , the image scanning apparatus  100  includes first to third light sources  111 ,  115 , and  118  for generating light beams of different visible wavelength bands, collimation optics ( 114 ,  116 , and  119 ) for collimating the light beams, line scan optics ( 121 , 122 , and  123 ) for forming a stripe pattern line scan perpendicular to the traveling direction of the collimated light beams, a spatial light modulator  124 , image-forming optics  130 , an iris  136 , a scan mirror  135 , and a screen. For the first to third light sources  111 ,  115 , and  118 , a semiconductor laser or second harmonic generator (SHG), which can generate the three primary colors, i.e., green, blue, and red, can be used. 
   The image scanning apparatus  100  can be used as a portable compact projector. To assist the understanding of the operation of the inventive apparatus, a three-axis coordinate system (x, y, and z) will be used. The z-axis can be defined as an optical axis coincident with the light traveling direction, the y-axis can be defined as an arbitrary axis perpendicular to the z-axis, and the x-axis can be defined as an axis perpendicular to both the z-axis and the y-axis. The line scan denotes a stripe pattern obtained while the major axis of light beams obtained by collimating the light beams with respect to the y-axis and converging the light beams with respect to the x-axis travels along the y-axis. The light beams are controlled to a line scan state to be easily input to the spatial light modulator  124 . 
   The first light source  111  can use an SHG, and the second and third light sources  115  and  118  can include a semiconductor laser. The semiconductor lasers used for the second and third light sources  115  and  118  can generate red and blue light beams having the oval spot. 
     FIG. 3A  shows a beam width on the minor axis of the red light, and  FIG. 3B  shows a beam width on the major axis of the red light. That is, the minor axis shown in the graph of  FIG. 3A  is located on the x-axis, and the major axis shown in the graph of  FIG. 3B  is located on the y-axis.  FIG. 4A  shows a beam width on the minor axis of the blue light, and  FIG. 4B  shows a beam width on the major axis of the blue light. 
   Referring to  FIGS. 3A ,  3 B,  4 A, and  4 B, the second and third light sources  115  and  118  for generating the blue and red light beams are aligned so that the major axis of each of the blue and red light beams can be output in parallel to the y-axis. That is, for the generated blue and red light beams, the major axis travels in parallel to the y-axis, and the minor axis travels in parallel to the x-axis. 
   However, since it is difficult to generate the green light beam using the semiconductor laser, the green light beam can be generated using the SHG.  FIG. 5A  shows a beam width on the x-axis of the green light, and  FIG. 5B  shows a beam width on the y-axis of the green light. As shown in  FIGS. 5A and 5B , the green light beam forms a circular spot having almost the same beam width on the x and y-axis. 
   The collimation optics are optics system for collimating the three primary colors generated by the first to third light sources  111 ,  115 , and  118  and includes first to third lenses  114 ,  116 , and  119  for respectively performing the collimation corresponding to the first to third light sources  111 ,  115 , and  118 , a reflective mirror  113 , and first and second wavelength selection filters  117  and  120 . The first to third light sources  111 ,  115 , and  118  can be arranged in the order of green, red, and blue, the order of red, green, and blue, the order of red, blue, and green, the order of green, blue, and red, the order of blue, red, and green, or the order of blue, green, and red. 
   An optical detector  101  monitors the magnitude of the green light beam from a portion of the green light beam, which is reflected by the first wavelength selection filter  117 . 
   The first lens  114  is located between the reflective mirror  113  and the first wavelength selection filter  117 , collimates the green light beam reflected by the reflective mirror  113 , and outputs the collimated green light beam to the first wavelength selection filter  117 . 
   The reflective mirror  113  changes the traveling path of the green light beam generated by the first light source  111  to the vertical direction by reflecting the green light beam. The reflective mirror  113  can use a dielectric or metal vapor deposited thin-film filter. 
   The first wavelength selection filter  117  is located between the first lens  114  and the second wavelength selection filter  120 , which are on the z-axis, and outputs the red light beam input from the second lens  116  and the green light beam reflected by the reflective mirror  113  to the line scan optics  121  to  123 . The second wavelength selection filter  120  is located between the line scan optics  121  to  123  and the first wavelength selection filter  117 , which are on the z-axis, reflects the blue light beam input from the third lens  119  to the line scan optics  121  to  123 , and passes the green and red light beams to the line scan optics  121  to  123 . 
   The line scan optics  121  to  123  includes a first diffusion lens  121 , a y-axis collimation lens  122 , and an x-axis convergence lens  123 , converts the green, red, and blue light beams input from the second wavelength selection filter  120  into a line scan pattern, and outputs the line scan pattern to the spatial light modulator  124 . 
   A diffraction grating type component, such as a SOM, a GLV, or a GEMS, can be used for the spatial light modulator  124 , and the spatial light modulator  124  diffracts the input line scan pattern light beams to modes of 0 th -order, 1 st  order, and multi-orders in the direction of the image-forming optics  130 . 
   The image-forming optics  130  can include a plurality of lenses  131  to  134 , converges the modes diffracted by the spatial light modulator  124  into the scan mirror  135  in the side of the y-z plane, and outputs the modes diffracted by the spatial light modulator  124  to the scan mirror  135  in a collimated state. 
   The iris  136  limits the modes of diffraction orders except 0 th -order among the light beams reflected by the scan mirror  135 , and the scan mirror  135  converges the mode of 0 th -order, which has passed through the iris  136 , among the incident modes onto specific pixels on the screen. The green, red, and blue light beams are sequentially irradiated by turns, and an entire image can be formed by overlapping the green, red, and blue light beams on specific pixels by a line scan. 
   The image scanning apparatus  100  can further include a second diffusion lens  112  located between the first light source  111  and the reflective mirror  113 . 
     FIG. 6  is a diagram for explaining a correlative non-spherical surface. As shown, the equations below can be deducted. Equation 1 indicates a correlation between a spot area of an input light beam and a spot area of an output light beam, and Equations 2 and 3 indicate the size and the magnitude of a spot transformed from the equivalent relationship of Equation 1.
 dφ in =dφ out   (1) I in dArea in =I out dArea out   (2) I in 2πrdr=I out 2πsds  (3) 
   In Equations 2 and 3, I in  denotes the magnitude of an input spot, I out  denotes the magnitude of an output spot, dArea in  denotes the size of the input spot, dArea out  denotes the size of the output spot, 2πrdr denotes the size of the input spot according to a radius thereof, and 2πsds denotes the size of the output spot according to a radius thereof. 
   Equation 3 can be transformed into an exponential function, i.e., Equation 4, and a function of the radius s of the output spot, i.e., Equation 5, can be obtained from Equation 4. 
   
     
       
         
           
             
               
                 
                   
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   Equation 5 can define a correlative non-spherical surface characteristic for increasing a light distribution uniformity ratio of a spot in the direction of the major axis. That is, by applying Equation 5 to the line scan optics  121  to  123  according to the current embodiment, a light distribution uniformity ratio of the light beams, which are output from the spatial light modulator  124 , on the y-axis can be increased. 
     FIG. 7  is a configuration of an image scanning apparatus  200  according to a second embodiment of the present invention. As shown, the image scanning apparatus  200  includes first to third light sources  211 ,  215 , and  218  for generating light beams of different visible wavelength bands, collimation optics ( 214 ,  216 , and  219 ) for collimating the light beams, line scan optics ( 221 ,  222 , and  223 ) for forming a stripe pattern line scan perpendicular to the traveling direction of the collimated light beams, a spatial light modulator  224 , an image-forming optics  230 , an iris  236 , a scan mirror  235 , a screen, a reflective mirror  213 , first and second wavelength selection filters  217  and  220 , an optical detector  201  for monitoring the magnitude of a green light beam from a portion of the green light beam, which is reflected by the first wavelength selection filter  217 , and a second diffusion lens  212 . 
   The line scan optics includes a first diffusion lens  221 , a collimation lens  222 , and a convergence lens  223 . 
   The spatial light modulator  224  reflects the path of incident light beams by making a sharp bend. The image-forming optics  230  includes a plurality of lenses  231 ,  232 ,  233 , and  234  disposed on the path of the modes reflected by the spatial light modulator  224 . 
     FIG. 8  is a configuration of an image scanning apparatus  300  according to a third embodiment of the present invention. As shown, the image scanning apparatus  300  includes first to third light sources  311 ,  315 , and  318  for generating light beams of different visible wavelength bands, collimation optics ( 312 ,  316 , and  319 ) for collimating the light beams, line scan optics ( 321 ,  322 , and  323 ) for forming a stripe pattern line scan perpendicular to the traveling direction of the collimated light beams, a spatial light modulator  324 , an image-forming optics  330 , composed of elements  331 - 334 , an iris  336 , a scan mirror  335 , a screen, first and second reflective mirrors  313  and  320  for perpendicularly changing the path of the light beams, first and second wavelength selection filters  317   a  and  317   b , an optical detector  301  for monitoring the magnitude of a green light beam from a portion of the green light beam, which is reflected by the first wavelength selection filter  317 , and a second diffusion lens  312 . 
   The line scan optics includes a first diffusion lens  321 , a collimation lens  322 , and a convergence lens  323 . 
   As described above, according to the embodiments of the present invention, by realizing an image using only a mode of 0 th -order among modes diffracted by a spatial light modulator module, a configuration of an iris for using only the mode of 0 th -order can be simplified, thereby miniaturizing the entire system. 
   While the invention has been shown and described with reference to a certain preferred embodiment 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.