Illumination system for a printing press

Abstract

An illumination system for a web travelling from upstream to downstream in a longitudinal direction in a printing press is described. The illumination system includes a first and a second illuminator for emitting light, each illuminator having a long axis arranged in a lateral direction. Further, the system includes a first and a second reflector, with the second reflector being arranged downstream from the first reflector. Each reflector has a surface for reflecting light from a corresponding illuminator toward the web, wherein a cross-section of each reflecting surface is a portion of a parabola having a focal point, or a portion of an ellipse, having two focal points. An illuminator is located at a corresponding focal point.

1 . An illumination system for a web travelling from upstream to downstream in a longitudinal direction in a printing press, with a lateral direction substantially perpendicular to the longitudinal direction, the system comprising: 
 a first and a second illuminator for emitting light, each illuminator having a long axis arranged in the lateral direction, and    a first and a second reflector, the second reflector arranged downstream from the first reflector, each reflector having a surface for reflecting light from a corresponding illuminator toward the web, wherein a cross-section of each reflecting surface is a portion of a parabola having a focal point, and wherein a corresponding illuminator is centered at each focal point.    
   
   
       2 . The illumination system of  claim 1 , wherein light rays from each reflector hit the web at an angle of substantially 45 degrees from the plane of the web.  
   
   
       3 . The illumination system of  claim 1 , wherein the first and second reflectors are symmetric to each other about a plane perpendicular to the web.  
   
   
       4 . The illumination system of  claim 3 , wherein the reflecting surface of the first upstream reflector reflects a portion of the light emitted from the first illuminator that is directed substantially away from the web, and the reflecting surface of the second downstream reflector reflects a portion of the light emitted from the second illuminator that is directed substantially away from the web.  
   
   
       5 . The illumination system of  claim 3 , wherein the reflecting surface of the first upstream reflector reflects a portion of the light emitted from the first illuminator that is directed substantially toward the web, and the reflecting surface of the second downstream reflector reflects a portion of the light emitted from the second illuminator that is directed substantially toward the web.  
   
   
       6 . The illumination system of  claim 1 , wherein the first and second reflectors are not symmetric to each other.  
   
   
       7 . The illumination system of  claim 6 , wherein the reflecting surface of the first upstream reflector reflects a portion of the light emitted from the first illuminator that is directed substantially away from the web, and the reflecting surface of the second downstream reflector reflects a portion of the light emitted from the second illuminator that is directed substantially toward the web.  
   
   
       8 . The illumination system of  claim 6 , wherein the reflecting surface of the first upstream reflector reflects a portion of the light emitted from the first illuminator that is directed substantially toward the web, and the reflecting surface of the second downstream reflector reflects a portion of the light emitted from the second illuminator that is directed substantially away the web.  
   
   
       9 . An illumination system for a web travelling from upstream to downstream in a longitudinal direction in a printing press, with a lateral direction substantially perpendicular to the longitudinal direction, the system comprising: 
 a first and a second illuminator for emitting light, each illuminator having a long axis arranged in the lateral direction, and    a first and a second reflector, the second reflector arranged downstream from the first reflector, each reflector having a compound reflecting surface for reflecting light from a corresponding illuminator toward the web, wherein a cross-section of each compound reflecting surface includes a first curve that is a portion of a parabola having a focal point, and a second curve that is a portion of a circle centered at the focal point, and further wherein a corresponding illuminator is centered at each focal point.    
   
   
       10 . The illumination system of  claim 9 , wherein light rays from each reflector hit the web at an angle of substantially 45 degrees from the plane of the web.  
   
   
       11 . The illumination system of  claim 9 , wherein the first and second reflectors are symmetric to each other about a plane perpendicular to the web.  
   
   
       12 . The illumination system of  claim 11 , wherein the reflecting surface of the first upstream reflector reflects a portion of the light emitted from the first illuminator that is directed substantially away from the web, and the reflecting surface of the second downstream reflector reflects a portion of the light emitted from the second illuminator that is directed substantially away from the web.  
   
   
       13 . The illumination system of  claim 11 , wherein the reflecting surface of the first upstream reflector reflects a portion of the light emitted from the first illuminator that is directed substantially toward the web, and the reflecting surface of the second downstream reflector reflects a portion of the light emitted from the second illuminator that is directed substantially toward the web.  
   
   
       14 . The illumination system of  claim 9 , wherein the first and second reflectors are not symmetric to each other.  
   
   
       15 . The illumination system of  claim 14 , wherein the reflecting surface of the first upstream reflector reflects a portion of the light emitted from the first illuminator that is directed substantially away from the web, and the reflecting surface of the second downstream reflector reflects a portion of the light emitted from the second illuminator that is directed substantially toward the web.  
   
   
       16 . The illumination system of  claim 14 , wherein the reflecting surface of the first upstream reflector reflects a portion of the light emitted from the first illuminator that is directed substantially toward the web, and the reflecting surface of the second downstream reflector reflects a portion of the light emitted from the second illuminator that is directed substantially away the web.  
   
   
       17 . An illumination system for a web travelling from upstream to downstream in a longitudinal direction in a printing press, with a lateral direction substantially perpendicular to the longitudinal direction, the system comprising: 
 a first and a second illuminator for emitting light, each illuminator having a long axis arranged in the lateral direction, and    a first and a second reflector, the second reflector arranged downstream from the first reflector, each reflector having a surface for reflecting light from a corresponding illuminator toward the web, wherein a cross-section of each reflecting surface is a portion of an ellipse having a first and a second focus, wherein the first illuminator is centered at the first focus of the first reflector, and the second illuminator is centered at the first focus of the second reflector, and the second focus of the first reflector and the second focus of the second reflector are substantially coincident.    
   
   
       18 . The illumination system of  claim 17 , wherein a first angle between the web and a line connecting the first focus and the second focus of the first reflector is 45 degrees or slightly greater than 45 degrees, and a second angle between the web and a line connecting the first focus and the second focus of the second reflector is 45 degrees or slightly greater than 45 degrees.  
   
   
       19 . The illumination system of  claim 17 , wherein the first reflector and the second reflector both include a blind spot.