Method of and apparatus for optical sensing of media through a suction or mesh belt

Abstract

An optical sensing assembly ( 20 ) detects media ( 32 ) carried by a traveling mesh or suction belt ( 34 ) having material portions ( 82 ) that define therebetween open portions ( 84 ). An emitter ( 22 ) is disposed opposite and spaced apart from the first side of the belt ( 34 ). The emitter ( 22 ) emits light in a direction from the first side toward the second side of the belt ( 34 ). A detector ( 24 ) is disposed opposite and spaced apart from the second side of the belt ( 34 ) and generally opposite the emitter ( 22 ). A portion of the light emitted by the emitter ( 22 ) passes through the open portions ( 84 ) of the mesh belt ( 34 ) and impinges upon the detector ( 24 ). The detector ( 24 ) issues a detect signal (DET_SIG) indicative of a reduction in the detected portion of light. The detect signal (DET_SIG) is filtered to reject reductions in the detected portion of light that are not due to the presence of media ( 32 ) on the belt ( 34 ).

1 . An optical sensing assembly for detecting media carried by a traveling mesh or suction belt, the belt having material portions that define therebetween open portions, the belt further having a first side and a second side, said optical sensing assembly comprising: 
 an emitter disposed opposite to and spaced a predetermined distance from the first side of the belt, said emitter emitting light in a direction from the first side of the belt toward the second side of the belt; and    a detector disposed opposite to and spaced a predetermined distance from the second side of the belt, said detector being disposed in general alignment with said emitter, a detected portion of the light emitted by said emitter passing through the open portions of the belt and being detected by said detector, said detector issuing a detect signal indicative of a reduction in said detected portion of light upon transport of media by said belt between said emitter and said detector.    
   
   
       2 . The optical sensing assembly of  claim 1 , further comprising filtering means, said filtering means electrically connected to said detector and receiving said detect signal, a media-indicating signal issued by said filter when said detect signal indicates the reduction in said detected portion of light is due to media being disposed between said emitter and said detector.  
   
   
       3 . The optical sensing assembly of  claim 2 , wherein said filtering means comprises one of a digital, analog, and software-based filter.  
   
   
       4 . The optical sensing assembly of  claim 2 , wherein said filtering means comprises software filtering.  
   
   
       5 . The optical sensing assembly of  claim 2 , further comprising: 
 a controller electrically connected with said detector and receiving therefrom said detect signal, a calibration signal issued by said controller;    calibration software executed by said controller, said calibration software setting a level of said calibration signal dependent at least in part upon said detect signal; and    an emitter driver receiving said calibration signal, said emitter driver being electrically connected to said emitter and issuing thereto an emitter drive signal, said emitter drive signal being dependent at least in part upon said calibration signal.    
   
   
       6 . The optical sensing assembly of  claim 1 , further comprising a separation distance separating said emitter and said detector, said detector being spaced a predetermined portion of said separation distance from the second side of the belt.  
   
   
       7 . The optical sensing assembly of  claim 6 , wherein said predetermined portion of said separation distance comprises less than approximately thirty-three percent.  
   
   
       8 . The optical sensing assembly of  claim 1 , wherein said emitter emits infra-red light and said detector detects infra-red light.  
   
   
       9 . An electrophotographic printing or copying machine, comprising: a traveling suction belt having a first side and a second side, said belt configured for carrying sheets of media, said belt having material portions defining open portions therebetween; and 
 a transmissive optical sensing assembly associated with said belt for detecting at least one of the presence and absence of media upon said belt.    
   
   
       10 . The electrophotographic machine of  claim 9 , wherein said transmissive optical sensing assembly comprises: 
 an emitter disposed opposite and spaced a predetermined distance from said first side of said belt, said emitter emitting light in a direction from said first side of said belt toward said second side of said belt; and    a detector disposed opposite and spaced a predetermined distance from said second side of said belt, said detector disposed in general alignment with said emitter, a detected portion of said light emitted by said emitter passing through said open portions of said belt and being detected by said detector, said detector issuing a detect signal indicative of a reduction in said detected portion of light upon transport of media by said belt between said emitter and said detector.    
   
   
       11 . The electrophotographic machine of  claim 10 , further comprising filtering means, said filtering means electrically connected to said detector and receiving said detect signal, a media-indicating signal issued by said filter when said reduction in said detected portion of light is due to media being disposed between said emitter and said detector.  
   
   
       12 . The electrophotographic machine of  claim 11 , wherein said filter comprises one of a digital, analog, and software-based filter.  
   
   
       13 . The electrophotographic machine of  claim 11 , further comprising: a controller electrically connected with said detector and receiving therefrom said detect signal, a calibration signal issued by said controller; 
 calibration software executed by said controller, said calibration software setting a level of said calibration signal dependent at least in part upon said detect signal; and    an emitter driver receiving said calibration signal, said emitter driver being electrically connected to said emitter and issuing thereto an emitter drive signal, said emitter drive signal being dependent at least in part upon said calibration signal.    
   
   
       14 . The electrophotographic machine of  claim 11 , further comprising a separation distance separating said emitter and said detector, said detector being spaced a predetermined portion of said separation distance from said second side of said belt.  
   
   
       15 . The electrophotographic machine of  claim 11 , wherein said predetermined portion of said separation distance comprises less than approximately thirty-three percent.  
   
   
       16 . The electrophotographic machine of  claim 11 , wherein emitter emits infra-red light and said detector detects infra-red light.  
   
   
       17 . A method for detecting the presence or absence of media on a media-carrying mesh or suction belt traveling at a predetermined rate, the belt having material portions that define open portions therebetween, said method comprising: emitting light onto a first side of the belt; 
 receiving on the second side of the belt at least a portion of the emitted light that has passed through the open portions of the belt from the first side to the second side thereof;    detecting a reduction in the received portion of light; and    filtering the detected reductions in the received portion of light to thereby distinguish between reductions caused by media and reductions caused by material portions of the belt.    
   
   
       18 . The method of  claim 17 , wherein said emitting step comprises driving an infra-red light emitting diode with a drive signal.  
   
   
       19 . The method of  claim 17 , wherein said filtering step comprises rejecting reductions in the received portion of light having durations that are less than a predetermined minimum duration.  
   
   
       20 . The method of  claim 17 , comprising the further step of calibrating the emitting step to emit a level of light that ensures the material portions of the belt do not reduce the received portion of received light by a sufficient amount to be detected while ensuring a sufficient level of light passes through the open portions of the belt to reduce erroneous detections of reductions due to sources other than media on the belt.  
   
   
       21 . A fuser transport assembly, comprising: 
 a traveling suction belt having a first side and a second side, said belt configured for carrying sheets of media, said belt having material portions defining open portions therebetween; and    a transmissive optical sensing assembly associated with said belt for detecting at least one of the presence and absence of media upon said belt.    
   
   
       22 . The fuser transport assembly of  claim 21 , wherein said transmissive optical sensing assembly comprises: 
 an emitter disposed opposite and spaced a predetermined distance from said first side of said belt, said emitter emitting light in a direction from said first side of said belt toward said second side of said belt; and    a detector disposed opposite and spaced a predetermined distance from said second side of said belt, said detector disposed in general alignment with said emitter, a detected portion of said light emitted by said emitter passing through said open portions of said belt and being detected by said detector, said detector issuing a detect signal indicative of a reduction in said detected portion of light.    
   
   
       23 . The electrophotographic machine of  claim 22 , further comprising filtering means, said filtering means electrically connected to said detector and receiving said detect signal, a media-indicating signal issued by said filter when said reduction in said detected portion of light is due to media being disposed between said emitter and said detector.