Imaging deviation compensation

Abstract

Imaging offset problems in imaging systems, such as electrophotographic (EPG) printers and copiers, are overcome. Imaging offset results from misaligned exposure units that, when uncompensated, produce dots on a photoreceptor belt at exposure positions that are offset from ideal dot positions. An imaging-offset compensating method of the invention first determines the imaging offset, which is a distance that may include a magnitude and a direction. The imaging offset is determined with respect to the ideal dot position. A time factor is then determined based on the magnitude of the imaging offset for each exposure unit. The time at which each exposure unit is actuated is modified by a respective time factor so that a dot produced by each exposure unit matches the ideal dot location thereof.

What is claimed is:  
     
         1 . A method of compensating for imaging offset of a dot produced by an exposure unit, on a substrate, in an imaging system, the imaging system comprising an array of exposure units, with at least one exposure unit misaligned in comparison with the other exposure units, the method comprising: 
 determining the imaging offset as a distance between the ideal dot position and the uncompensated dot position for each exposure unit; and    matching the uncompensated dot position to the ideal dot position.    
     
     
         2 . The method of  claim 1 , wherein the matching step comprises: 
 delaying a formation of the dot on the substrate by an amount of time corresponding to the imaging offset.    
     
     
         3 . The method of  claim 1 , wherein the matching step further comprises: 
 determining a time factor based on the imaging offset.    
     
     
         4 . The method of  claim 3 , wherein the step of determining a time factor further comprises: 
 determining a time factor that is proportional to a magnitude of the distance of the imaging offset.    
     
     
         5 . The method of  claim 1 , wherein the determining step further comprises: 
 determining a magnitude of the distance of the imaging offset.    
     
     
         6 . The method of  claim 5 , wherein the matching step further comprises: 
 determining a time factor that is proportional to the magnitude of the distance of the imaging offset.    
     
     
         7 . The method of  claim 6 , wherein the matching step further comprises: 
 actuating the exposure unit at a time modified by the time factor.    
     
     
         8 . The method of  claim 5 , wherein the determining step further comprises: 
 determining a direction of the imaging offset.    
     
     
         9 . The method of  claim 8 , wherein the matching step further comprises: 
 determining a time factor that is proportional to the magnitude of the distance of the imaging offset and that has a sign indicative of the direction of the imaging offset.    
     
     
         10 . The method of  claim 9 , wherein the matching step further comprises: 
 actuating the exposure unit at a time modified by the time factor.    
     
     
         11 . A method of compensating for imaging offset of a dot produced by an exposure unit, on a substrate, in an imaging system, the imaging system comprising an array of exposure units, with at least one exposure unit misaligned, in comparison with the other exposure units, the method comprising: 
 determining the imaging offset as a distance between the ideal dot position and the uncompensated dot position for each exposure unit; and    matching the uncompensated dot position to the ideal dot position for each exposure unit.    
     
     
         12 . The method of  claim 11 , wherein the determining step further comprises: 
 determining a direction of the imaging offset.    
     
     
         13 . The method of  claim 12 , wherein the matching step further comprises: 
 determining a time factor for each exposure unit based on the imaging offset.    
     
     
         14 . The method of  claim 13 , further comprising: 
 actuating each exposure unit at a time modified by the time factor thereof to form a latent image on the substrate.    
     
     
         15 . The method of  claim 12 , further comprising: 
 developing the latent image on sheet material.    
     
     
         16 . The method of  claim 11 , wherein the determining step further comprises: 
 retrieving the imaging offset from a network.    
     
     
         17 . The method of  claim 16 , wherein the retrieving step further comprises retrieving the imaging offset from the Internet.  
     
     
         18 . An electrophotographic (EPG) module for printing images free of imaging offset, the EPG module comprising: 
 a substrate;    a light source including a plurality of exposure units each for producing a dot on the substrate;    the plurality of exposure units including at least one misaligned exposure unit that is out of alignment with the other exposure units; and    each of the misaligned exposure units producing a dot at an uncompensated dot position when uncompensated for misaligned thereof such that each of the misaligned exposure units has an imaging offset corresponding to a distance defined between the uncompensated dot position and an ideal dot position; and    a matching device in communication with the light source for causing each of the misaligned exposure units to be actuated based on the imaging offset to produce a dot in the ideal dot position.    
     
     
         19 . The EPG module of  claim 18 , wherein the matching device includes a device for causing the misaligned exposure units to be actuated at a time different from an ideal actuation time that produces a dot in the ideal dot position.  
     
     
         20 . The EPG module of  claim 19 , wherein the matching device includes a delaying device for causing the misaligned exposure units to be actuated at a time later than an ideal actuation time that produces a dot in the ideal dot position.  
     
     
         21 . The EPG module of  claim 19 , wherein the matching device includes a device for causing the misaligned exposure units to be actuated at a time earlier than an ideal actuation time that produces a dot in the ideal dot position.  
     
     
         22 . The EPG module of  claim 20 , wherein the matching device includes a device for causing the misaligned exposure units to be actuated at a time earlier than an ideal actuation time that produces a dot in the ideal dot position.  
     
     
         23 . The EPG module of  claim 18 , further comprising a storage device for storing the imaging offset for each of the exposure units, wherein the storage device stores identification information unique to the EPG module.  
     
     
         24 . The EPG module of  claim 18 , wherein the substrate is a photoreceptor belt.  
     
     
         25 . A light-emitting diode print head (LPH) comprising: 
 a plurality of exposure units each for producing a dot on the substrate;    the plurality of exposure units including at least one misaligned exposure unit that is out of alignment with the other exposure units; and    each of the misaligned exposure units producing a dot at an uncompensated dot position when uncompensated for misalignment thereof such that each of the misaligned exposure units has an imaging offset corresponding to a distance defined between the uncompensated dot position and an ideal dot position; and    a matching device in communication with the storage device and the light source for causing each of the misaligned exposure units to be actuated based on the imaging offset to produce a dot in the ideal dot position.    
     
     
         26 . The LPH of  claim 25 , wherein the matching device comprises a delaying device for causing the misaligned exposure units to be actuated at a time different from an ideal actuation time that produces a dot in the ideal dot position.  
     
     
         27 . The LPH of  claim 25 , further comprising a storage device for storing the imaging offset for each of the exposure units.  
     
     
         28 . The LPH of  claim 27 , wherein the storage device stores identification information unique to the EPG module.  
     
     
         29 . An imaging system comprising: 
 a photoreceptor belt;    a light source including a plurality of exposure units each for producing a dot on the photoreceptor belt;    the plurality of exposure units including at least one misaligned exposure unit that is out of alignment with the other exposure units; and    each of the misaligned exposure units producing a dot at an uncompensated dot position when uncompensated for misalignment thereof such that each of the misaligned exposure units has an imaging offset corresponding to a distance defined between the uncompensated dot position and an ideal dot position; and    a processor in communication with the light source for causing each of the misaligned exposure units to be actuated based on the imaging offset to produce a dot in the ideal dot position.    
     
     
         30 . The imaging system of  claim 25 , wherein image data is stored in an image buffer before being passed to a compensation module.  
     
     
         31 . The imaging system of  claim 30 , wherein the image data is transferred to the image buffer using direct memory access.  
     
     
         32 . The imaging system of  claim 30 , wherein the image data is transferred from the image buffer using direct memory access.  
     
     
         33 . The imaging system of  claim 30 , wherein the image data is transferred to and from the image buffer using direct memory access.  
     
     
         34 . The imaging system of  claim 30 , wherein the processor delays the actuation of a misaligned exposure unit to be at a time later than an ideal actuation time that produces a dot in the ideal dot position.  
     
     
         35 . The imaging system of  claim 30 , wherein the processor delays the actuation of a misaligned exposure unit to be at a time earlier than an ideal actuation time that produces a dot in the ideal dot position.  
     
     
         36 . A computer-readable memory having stored thereon computer-readable instructions that, when loaded into a computer system, cause the computer system to perform a method of compensating for imaging offset of dots produced by an array of exposure units on a substrate in an imaging system, the dots having uncompensated dot positions that are out of alignment with ideal dot positions, the method comprising: 
 determining the imaging offset, for each exposure unit, as a distance between the ideal dot position and the uncompensated dot position; and    matching the uncompensated dot position to the ideal dot position, for each exposure unit.    
     
     
         37 . A method of compensating for imaging offset of a dot produced by an exposure unit, on a substrate, in an imaging system, the imaging system comprising an array of exposure units, with at least one exposure unit misaligned, in comparison with the other exposure units, the method comprising: 
 determining the imaging offset as a distance between the ideal dot position and the uncompensated dot position for each exposure unit;    determining a direction of the imaging offset;    retrieving the imaging offset from a network;    determining a time factor proportional to a magnitude of the distance of the imaging offset;    matching the uncompensated dot position to the ideal dot position;    actuating the exposure unit at a time modified by the time factor; delaying a formation of the dot on the substrate by an amount of time corresponding to the imaging offset;    storing the imaging offset for each of the exposure units in a storage device; and,    developing the latent image on sheet material.