Abstract:
An illumination station for viewing reflection copy images such as documents, photos, and the like having a back-plate against which a reflection copy image is disposed for viewing, one or more overhead light sources disposed in a top member, and a reflector at the base of the back-plate configured to reflect incident light on the lower portion of the back-plate. The use of a reflector provides enhanced illumination to the lower portion of the back-plate and therefore improves the uniformity of illumination of the entire back-plate, and, consequently, of the reflection copy image affixed thereto.

Description:
FIELD OF INVENTION 
       [0001]    The present invention relates generally to illuminated stations for viewing reflection copies such as documents, particularly color images, commonly known as light booths. More particularly, the invention is directed to a light booth having improved uniformity of illumination across a viewing region to facilitate a viewer&#39;s perception of a reflection copy placed in the viewing region by providing a better lit and more uniformly lit reflection copy image. 
       BACKGROUND 
       [0002]    Illuminated viewing environments, commonly known as light booths, are well known in the photographic and graphic arts for transmission or reflectance viewing of color prints, proofs, transparencies and the like. Typically, a light booth comprises a back-plate against which a reflection copy image such as a document or photograph, is placed for viewing and an overhead lighting source, such as incandescent, fluorescent, or ultraviolet lamp, for illuminating the document. Such viewing systems have found wide-spread use for visual color assessment, comparison of color variations, color-matching, the detection of metamerism (the detection of slight color differences), and soft-proofing. 
         [0003]    One shortcoming of conventional light booths is uneven illumination of the back-plate resulting from the fact that the intensity of light incident is attenuated by the square of the distance from the light source. The function that describes how apparent brightness changes with distance is given by the mathematical relationship: 
         [0000]    
       
      
       I=I 
       o 
       /r 
       2  
      
     
         [0000]    As shown by the formula, the intensity of the light varies as the inverse square of the separation from the light source (r). 
         [0004]    As such, because the light source is typically placed towards the top of the back-plate, the brightness of the back-plate will be greater at the top of the back-plate than at the bottom. Such uneven illumination makes accurate color assessment of the entire reflection copy image difficult. 
         [0005]    Therefore, there is a need in the art for light booths which overcome the deficiencies of the prior art by providing substantially uniform light intensity across the surface of the back-plate and thus across the reflection copy image disposed thereupon. It is therefore an object of the present invention to provide viewing environments, particularly those known in the art as light booths, for illuminating reflection copies, in particular colored documents such as photographs, which provide improved uniformity of light across the entire viewing region. 
       SUMMARY OF THE INVENTION 
       [0006]    In accordance with the foregoing objectives and others, the present invention provides illuminated stations for viewing reflection copy images such as documents and the like, having a back-plate against which a reflection copy image is disposed for viewing, one or more overhead light sources disposed in a top member, and a reflector at the base of the back-plate configured to reflect incident light on the lower portion of the back-plate. It has surprisingly been found that the use of a reflector, configured as described herein, provides enhanced illumination to the lower portion of the back-plate and therefore improves the uniformity of illumination of the entire back-plate, and, consequently, of the reflection copy image affixed thereto. 
         [0007]    In an embodiment of the present invention, the light booth comprises a back-plate against which a reflection copy image is disposed for viewing; at least one overhead light disposed in a top member of the light booth; and a reflector at a base of the back-plate configured to reflect incident light at the lower portion of the back-plate thereby improving the uniformity of illumination of the back-plate and consequently of the reflection copy disposed thereon. 
         [0008]    In an exemplary embodiment of the present invention, the light booth comprises: a back-plate for supporting a reflection copy; a top member having a proximal end and a distal end wherein the proximal end is coupled to the upper end of the back-plate to form an angle in the range of or about 82 to 86 degrees; a base comprising a reflective portion; wherein the reflective portion has a proximal end, a distal end, and a width dimension; wherein the proximal end is coupled to the lower end of the back-plate to form an angle in the range of or about 88 to 92 degrees. The light booth further comprises a first and second overhead light disposed in the top member for illuminating the back-plate; the first and second overhead light disposed such that each optical axis of light incident to the proximal end of the reflective portion has an angle dimension relative to the width dimension sufficient to reflect incident light rays towards a bottom portion of the back-plate, thereby increasing the intensity of light on the bottom portion and improving the overall uniformity of illumination of the back-plate. 
         [0009]    These and other features, aspects, and advantages of the present invention will become better understood with reference to the following detailed description, drawings, and appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is side view of a conventional light booth. 
           [0011]      FIG. 2  is a side view of an embodiment of a viewing apparatus in accordance with the present invention. 
           [0012]      FIG. 3  is a side view of an embodiment of a viewing apparatus in accordance with an embodiment of the present invention showing exemplary dimensions that maximize the illumination of the bottom portion of a back-plate having a height of or about 35 cm. 
           [0013]      FIG. 4  is a side view of an embodiment of a viewing apparatus in accordance with an embodiment of the present invention showing exemplary dimensions that maximize the illumination of the bottom portion of a back-plate having a height of or about 32 cm. 
           [0014]      FIG. 5  is a side view of an embodiment of a viewing apparatus in accordance with an embodiment of the present invention showing exemplary dimensions that maximize the illumination of the bottom portion of a back-plate having a height of or about 44 cm. 
           [0015]      FIG. 6  is a side view of an embodiment of a viewing apparatus in accordance with an embodiment of the present invention showing exemplary dimensions that maximize the illumination of the bottom portion of a back-plate having a height of or about 62 cm. 
           [0016]      FIG. 7  is a frontal view of an embodiment of a viewing apparatus in accordance with the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    As used herein, all terms are intended to have their ordinary and accustomed meaning in the art unless otherwise specified. The term “light booth” is not meant to be particularly limiting and refers generally to any apparatus for viewing an object against a vertical or inclined plate in which overhead lighting illuminates the viewing surface. 
         [0018]    Referring now to  FIG. 1 , a conventional light booth  10  of the prior art is illustrated. Light booth  10  comprises an inclined back-plate  20  which is mounted on a base  30 . A top member  40  houses one or more light sources (shown as  50   a  and  50   b ) disposed towards the proximal end  55  of top member  40  in relation to the viewer. This configuration minimizes the distance between light sources  50   a  and  50   b  and the top and bottom of back-plate  20 . Base  30  is typically inclined away from back-plate  20  so as to form an obtuse angle therewith. In this configuration, some light (e.g.  60   a  and  60   b ) incident on the base is reflected away from the viewing surface as shown by the arrows, and therefore, does not illuminate back-plate  20 . In practice it has been observed that a substantial gradient in light intensity exists from top half  15   a  to bottom half  15   b  of the viewing surface in light booths such as those shown in  FIG. 1 . 
         [0019]    One embodiment of the inventive light booth is shown in  FIG. 2 . Light booth  200  comprises an inclined back-plate  220  which is mounted on a base  230 . A top member  240  houses one or more light sources (shown as  250   a  and  250   b ) disposed towards the proximal end  255  of top member  240  in relation to the viewer. Unlike conventional light booths such as that shown in  FIG. 1 , the inventive light booth of  FIG. 2  has a base  230  that comprises a reflective portion  232  that is inclined towards back-plate  220  so as to be substantially orthogonal to back-plate  220 . The reflective portion  232  can be made of any material capable of reflecting incident light having a reflective coefficient in the range of or about 0.5 to 1, preferably a mirror. The reflective portion can either be integral with base  230  or releasably attached to base  230 . In this configuration, some light (e.g.,  260   a  and  260   b ) incident on the base  230  is reflected back towards the lower portion  215   b  of the back-plate  220  as shown by the arrows. Therefore, some light is effectively rerouted to illuminate the lower portion of the back-plate  220 , thereby improving the uniformity of illumination of the back-plate and therefore the reflection copy thereon. 
         [0020]    The width of the reflector and the angle formed by the reflector coupled to the back-plate relative to the length of the back-plate and the distance of the light sources from the back-plate, all affect the amount of light reflected onto the back-panel and the reflection copy disposed thereon. The most significant dimension to affect the amount of light reflected onto the back-panel is the angle formed by the intersection of the geometrical plane of the reflector and the geometrical plane of the back-plate. Too great an angle of the reflector and the back-plate relative to the iterated dimensions, and minimal light will reflect back onto the reflection copy surface so as not to sufficiently increase the brightness of the bottom portion of the back-plate. Too little an angle of the reflector and the back-plate relative to the additional dimensions will result in a heavy band of light formed on the lower portion of the back-plate close to the mirror. 
         [0021]    The preferred embodiment of the light booth of the present invention comprises the following dimensions. Generally with reference to  FIG. 2 , the angle formed by the intersection of the geometrical plane of the back-plate  220  and the geometrical plane of the top member  240  forms an angle in the range of or about 82° to 86°. The angle formed by the intersection of the geometrical plane of the reflective portion  232  of the base and the geometrical plane of the back-plate  220  forms an angle in the range of or about 88° to 92°. The angle formed by the intersection of the optical axis ray  260   a  of the light source  250   a  nearest the back-plate  220  and the proximal edge  231  of the reflective portion  232  of the base  230  forms an angle of or about 102° to 112°. The angle formed by the intersection of the optical axis light ray  260   b  of the light source  250   b  furthest from the back-plate  220  and the proximal edge  231  of the reflective portion  232  of the base  230  forms an angle in the range of or about 108° to 120°. The angle formed by the intersection of the optical axis ray  260   a  of the light source  260   a  closest to the back-plate  220  forms an angle at the proximal edge  231  of the reflective portion  232  of the base  230  with the optical axis ray  260   b  of the light source  250   b  furthest away from the back-plate  220  in the range of or about 3° to 9°. 
         [0022]    The International Standards Organization (ISO) Specification 3664 defines the optimal viewing-conditions for graphical technology and photography and specifically establishes the luminance levels for reflection copies. According to ISO 3664, any departures from complete uniformity should gradually diminish from the center of the viewing surface to the edge. ISO 3664 further dictates that with respect to viewing areas less than or equal to 1 meter square, the luminance at any point within the square shall not be less than 75% of the luminance measured at the center of the illuminated viewing surface. For larger viewing areas, the ISO 3664 specification indicates that the limit shall not be less than 60%.  FIGS. 3 ,  4 ,  5 , and  6  show exemplary light booths having dimensions for ensuring maximum results of light evenness to illuminate a reflection copy in accordance with the requirements of ISO 3664. 
         [0023]      FIG. 3  shows one embodiment of the inventive light booth having dimensions that effectuate a uniform illumination of the back-panel and therefore of a reflection copy disposed thereon. Light booth  300  comprises an inclined back-plate  320  of a length of or about 35 cm which has a top member  340  of a length of or about 33.3 cm mounted thereupon to form an angle  365  of or about (+or −2) 84°. Base  330  has a reflective portion  332  of a width of or about 5.6 cm coupled to back-plate  320  to form an angle  375  of or about (+or −2) 90°. Light source  350   a  as the furthest light source from the back-plate  320  is disposed in the top member  340  at a distance from the back-plane  320  such that an optical axis light ray  360   a  of the light emitted from the light source  350   a  forms an incident angle  370  with the proximal edge  365  of the reflective portion  332  of or about (+or −4) 116°. This angle  370  indicates the widest angle that can be formed by the disposal of an overhead light source in top member  340  at a distance from back-plate  320  such that light can be properly reflected on the back-plate  320  without being wasted as spill light in this embodiment. The second light source  350   b  is disposed in the top member  340  such that the optical axis ray  360   b  of this second light source  350   b  forms an angle  380  at the proximal edge  365  of the reflective portion  332  with the optical axis ray  360   a  of the first light source  350   a  of or about (+or −2) 6.5°. This second angle  380  determines the closest distance to the back-plate  320  an overhead light source can be disposed in top member  340  such that the light can be properly reflected on the back plate  320  without creating a band of light on the lower portion  315   b  of back-plate  320  close to the reflective portion  332  in this embodiment. 
         [0024]      FIG. 4  shows another embodiment of the inventive light booth having dimensions that effectuate a uniform illumination of the back-panel and therefore of a reflection copy disposed thereon. Light booth  400  comprises an inclined back-plate  420  of a length of or about 31.8 cm which has a top member  440  of a length of or about 26.6 cm mounted thereupon to form an angle  465  of or about (+or −2) 84°. Base  430  has a reflective portion  432  of a width of or about 4.3 cm coupled to back-plate  420  to form an angle  475  of or about (+or −2) 90°. Light source  450   a  as the furthest light source from the back-plate  420  is disposed in the top member  440  at a distance from the back-plane  420  such that an optical axis light ray  460   a  of the light emitted from the light source  450   a  forms an incident angle  470  with the proximal edge  465  of the reflective portion  432  of or about (+or −4) 115°. This angle  470  indicates the widest angle that can be formed by the disposal of an overhead light source in top member  440  at a distance from back-plate  420  such that light can be properly reflected on the back-plate  420  without being wasted as spill light in this embodiment. The second light source  450   b  is disposed in the top member  440  such that the optical axis ray  460   b  of this second light source  450   b  forms an angle  480  at the proximal edge  465  of the reflective portion  432  with the optical axis ray  460   a  of the first light source  450   a  of or about (+or −2) 7°. This second angle  480  defines the closest distance to the back-plate  420  an overhead light source can be disposed in top member  440  such that the light can be properly reflected on the back plate  420  without creating a band of light on the lower portion  475  of back-plate  420  close to the reflective portion  432  in this embodiment. 
         [0025]      FIG. 5  shows an additional embodiment of the inventive light booth having dimensions that effectuate a uniform illumination of the back-panel and therefore of a reflection copy disposed thereon. Light booth  500  comprises an inclined back-plate  520  of a length of or about 43.8 cm which has a top member  540  of a length of or about 33.3 cm mounted thereupon to form an angle  565  of or about (+or −2) 84°. Base  530  has a reflective portion  532  of a width of or about 6.4 cm coupled to back-plate  520  to form an angle  575  of or about (+or −2) 90°. Light source  550   a  as the furthest light source from the back-plate  520  is disposed in the top member  540  at a distance from the back-plane  520  such that an optical axis light ray  560   a  of the light emitted from the light source  550   a  forms an incident angle  570  with the proximal edge  565  of the reflective portion  532  of or about (+or −4) 114°. This angle  570  indicates the widest angle that can be formed by the disposal of an overhead light source in top member  540  at a distance from back-plate  520  such that light can be properly reflected on the back-plate  520  without being wasted as spill light in this embodiment. The second light source  550   b  is disposed in the top member  540  such that the optical axis ray  560   b  of this second light source  550   b  forms an angle  580  at the proximal edge  565  of the reflective portion  532  with the optical axis ray  560   a  of the first light source  550   a  of or about (+or −2) 5°. This second angle  580  determines the closest distance to the back-plate  520  an overhead light source can be disposed in top member  540  such that the light can be properly reflected on the back plate  520  without creating a band of light on the lower portion  515   b  of back-plate  520  close to the reflective portion  532  in this embodiment. 
         [0026]      FIG. 6  shows an additional embodiment of the inventive light booth having dimensions that effectuate a uniform illumination of the back-panel and therefore of a reflection copy disposed thereon. Light booth  600  comprises an inclined back-plate  620  of a length of or about 61.6 cm which has a top member  640  of a length of or about 40.6 cm mounted thereupon to form an angle  665  of or about (+or −2) 84°. Base  630  has a reflective portion  632  of a width of or about 7.6 cm coupled to back-plate  620  to form an angle  675  of or about (+or −2) 90°. Light source  650   a  as the furthest light source from the back-plate  620  is disposed in the top member  640  at a distance from the back-plate  620  such that an optical axis light ray  660   a  of the light emitted from the light source  650   a  forms an incident angle  670  with the proximal edge  665  of the reflective surface  632  of or about (+or −4) 112°. This angle  670  indicates the widest angle that can be formed by the disposal of an overhead light source in top member  640  at a distance from back-plate  620  such that light can be properly reflected on the back-plate  620  without being wasted as spill light in this embodiment. The second light source  650   b  is disposed in the top member  640  such that the optical axis ray  660   b  of this second light source  650   b  forms an angle  680  at the proximal edge  665  of the reflective portion  632  with the optical axis ray  660   a  of the first light source  650   a  of or about (+or −2) 8°. This second angle  680  determines the closest distance to the back-plate  620  an overhead light source can be disposed in top member  640  such that the light can be properly reflected on the back plate  620  without creating a band of light on the lower portion  675  of back-plate  620  close to the reflective surface  632  in this embodiment. 
         [0027]      FIG. 7  shows a frontal view of a particularly preferred embodiment of the present invention. Light booth  700  comprises an inclined back-plate  720  which is mounted on a base  730 . A top member  740  houses one or more light sources (shown as  750   a  and  750   b ) disposed at the proximal end of top member  740  in relation to the viewer. Base  730  comprises a reflective portion  732  that is inclined towards back-plate  720  so as to be substantially orthogonal to back-plate  720 . The reflective portion  732  is preferably a mirror either integral with base  730  or releasably attached to base  730 . In this configuration, some light incident on the reflector  732  is reflected back towards the lower portion of the back-plate  720  and is thus effectively rerouted to illuminate the lower portion of the back-plate  720 , thereby improving the uniformity of illumination of the back-plate and therefore the reflection copy  722  thereon. 
         [0028]    Charts I-IV below illustrate the improvement in overall luminance uniformity of the above-described light booth embodiments of the present invention. Using a Minolta LS-100 luminance meter, luminance measurements were taken at pre-selected bottom intervals, and pre-selected top intervals of the embodiments of the inventive light booth and conventional light booths of the same size. The measurements at the top were taken at the center of the viewing area and 14 cm down from the top of the viewing area. The measurements at the bottom were taken at the center of the viewing area and 14 cm up from the bottom. The comparative data showing the improvement in uniformity of the exemplary embodiments of the present invention is presented in the following charts. 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 CHART I 
               
             
             
               
                   
               
               
                 (LIGHT BOOTH 200) 
               
             
          
           
               
                   
                 LIGHT BOOTH 
                 LIGHT BOOTH 
               
               
                   
                   
               
             
          
           
               
                 LUMINANCE MEASUREMENT 
                 181 fL 
                 181 fL 
               
               
                 TOP OF BACK-PLATE 
               
               
                 LUMINANCE MEASUREMENT 
                  68 fL 
                 106 fL 
               
               
                 BOTTOM OF BACK-PLATE 
               
               
                   
               
             
          
         
       
     
         [0029]    In the conventional light booth the illumination difference between the top of the back-plate and the bottom of the back-plate is 113 foot-Lamberts (fL). In inventive light booth  200 , on the other hand, the illumination difference between the top of the back-plate and the bottom of the back-plate has been reduced to 75 fL, resulting in a 27.5% improvement in the overall uniformity of luminance (calculated from center measurement). 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 CHART II 
               
             
             
               
                   
               
               
                 (LIGHT BOOTH 400) 
               
             
          
           
               
                   
                   
                 LIGHT BOOTH  
               
               
                   
                 LIGHT BOOTH 
                 400 
               
               
                   
                   
               
             
          
           
               
                 LUMINANCE MEASUREMENT 
                 217 fL 
                 217 fL 
               
               
                 TOP OF BACK-PLATE 
               
               
                 LUMINANCE MEASUREMENT 
                  60 fL 
                  98 fL 
               
               
                 BOTTOM OF BACK-PLATE 
               
               
                   
               
             
          
         
       
     
         [0030]    In the conventional light booth the illumination difference between the top of the back-plate and the bottom of the back-plate is 157 fL. In inventive light booth  200 , on the other hand, the illumination difference between the top of the back-plate and the bottom of the back-plate has been reduced to 119 fL, resulting in a 23.4% improvement in the overall uniformity of luminance (calculated from center measurement). 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 CHART III 
               
             
             
               
                   
               
               
                 (LIGHT BOOTH 500) 
               
             
          
           
               
                   
                   
                 LIGHT BOOTH 
               
               
                   
                 LIGHT BOOTH 
                 500 
               
               
                   
                   
               
             
          
           
               
                 LUMINANCE MEASUREMENT 
                 220 fL 
                 220 fL 
               
               
                 TOP OF BACK-PLATE 
               
               
                 LUMINANCE MEASUREMENT 
                  57 fL 
                  85 fL 
               
               
                 BOTTOM OF BACK-PLATE 
               
               
                   
               
             
          
         
       
     
         [0031]    In the conventional light booth the illumination difference between the top of the back-plate and the bottom of the back-plate is 163 fL. In inventive light booth  200 , on the other hand, the illumination difference between the top of the back-plate and the bottom of the back-plate has been reduced to 135 fL resulting in a 19.8% improvement in the overall uniformity of luminance(calculated from center measurement). 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 CHART IV 
               
             
             
               
                   
               
               
                 (LIGHT BOOTH 600) 
               
             
          
           
               
                   
                   
                 LIGHT BOOTH 
               
               
                   
                 LIGHT BOOTH 
                 600 
               
               
                   
                   
               
             
          
           
               
                 LUMINANCE MEASUREMENT 
                 190 fL 
                 190 fL 
               
               
                 TOP OF BACK-PLATE 
               
               
                 LUMINANCE MEASUREMENT 
                  42 fL 
                  73 fL 
               
               
                 BOTTOM OF BACK-PLATE 
               
               
                   
               
             
          
         
       
     
         [0032]    In the conventional light booth the illumination difference between the top of the back-plate and the bottom of the back-plate is 148 fL. In inventive light booth  200 , on the other hand, the illumination difference between the top of the back-plate and the bottom of the back-plate has been reduced to 117 fL, resulting in a 23.0% improvement in the overall uniformity of luminance (calculated from center measurement). 
         [0033]    As demonstrated by the charts above, the uniformity of the luminance is greatly improved in the light booth embodiments of the present invention, solving the need in the art for light booths which overcome the deficiencies of the prior art by providing substantially uniform light intensity across the surface of the back-plate and thus across the reflection copy image disposed thereupon. 
         [0034]    Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments herein.