Method for measuring density, printing method, method of calculating correction value, method of manufacturing printing apparatus and method for obtaining correction value

Abstract

A method for measuring density, includes: forming on a medium a pattern that consists of a plurality of dot rows formed respectively in a plurality of row regions lined up in a direction intersecting a movement direction in which a plurality of nozzles move, by forming each of the dot rows in the row region arranged in the movement direction by ejecting ink from the nozzles; reading the pattern by a scanner; measuring density of each of the row regions of the read pattern; calculating respective modification values corresponding to each of the row regions, based on at least a part of a measurement result of the density of the plurality of the row regions; and modifying respective measured values of the density of each of the row regions based on the respective modification values corresponding to each of the row regions.

1 . A method for obtaining a correction value, comprising:
 reading by a scanner a pattern that consists of a plurality of dot rows formed respectively in a plurality of row regions lined up in a direction intersecting a movement direction of nozzles;   measuring density of each of the row regions of the read pattern;   calculating a first correction value for correcting the density of a row region that is located in a first region of the pattern, based on a measured value of the density of that row region that is located in the first region;   calculating a second correction value for correcting the density of a row region that is located in a second region contiguous to the first region, based on a measured value of the density of that row region and a measured value of the density of another row region that is located in the second region; and   modifying at least one of the first correction value and the second correction value in order to reduce a difference between the first correction value and the second correction value.   
   
   
       2 . The method for obtaining a correction value according to  claim 1 , wherein:
 at least one of the first correction value and the second correction value is modified in order to reduce a difference between an average value of a plurality of the first correction values and an average value of a plurality of the second correction values.   
   
   
       3 . The method for obtaining a correction value according to  claim 2 , wherein:
 the difference between the average value of the first correction values and the average value of the second correction values is determined as a modification value; and   at least one of the first correction value and the second correction value is modified based on the modification value.   
   
   
       4 . The method for obtaining a correction value according to  claim 1 , wherein:
 in order to reduce a difference between the first correction value of a row region that is located in the first region and is contiguous to the second region and the second correction value of a row region that is located in the second region and is contiguous to the first region, at least one of the first correction value and the second correction value is modified.   
   
   
       5 . The method for obtaining a correction value according to  claim 4 , wherein:
 the difference between the first correction value of the row region that is located in the first region and is contiguous to the second region and the second correction value of the row region that is located in the second region and is contiguous to the first region is determined as a modification value; and   at least one of the first correction value and the second correction value is modified based on the modification value.   
   
   
       6 . The method for obtaining a correction value according to  claim 1 , wherein:
 the measured values of the density of each of the row regions are modified depending on the row regions; and   the first correction value and the second correction value are calculated based on the modified measured values.   
   
   
       7 . The method for obtaining a correction value according to  claim 6 , wherein:
 when modifying the measured values depending on the row regions, a linear fitting line and an average value are obtained from the measured values, and the measured values of the density of the row regions are modified depending on a difference between a value of the linear fitting line in each of the row regions and the average value.   
   
   
       8 . The method for obtaining a correction value according to  claim 7 , wherein:
 the linear fitting line is calculated based on the least-square method.   
   
   
       9 . The method for obtaining a correction value according to  claim 1 , wherein:
 the first region is a region including a first dot row formed by first printing; and   the second region is a region consisting of a second dot row formed by second printing that is different from the first printing.   
   
   
       10 . The method for obtaining a correction value according to  claim 1 , wherein:
 at least one of the first correction value and the second correction value is modified in order to reduce a difference between an average value of a plurality of the first correction values and an average value of a plurality of the second correction values,   the difference between the average value of the first correction values and the average value of the second correction values is determined as a first modification value,   at least one of the first correction value and the second correction value is modified based on the first modification value,   in order to reduce a difference between the first correction value of a row region that is located in the first region and is contiguous to the second region and the second correction value of a row region that is located in the second region and is contiguous to the first region,   at least one of the first correction value and the second correction value is modified,   the difference between the first correction value of the row region that is located in the first region and is contiguous to the second region and the second correction value of the row region that is located in the second region and is contiguous to the first region is determined as a second modification value,   at least one of the first correction value and the second correction value is modified based on the second modification value,   the measured values of the density of each of the row regions are modified depending on the row regions,   the first correction value and the second correction value are calculated based on the modified measured values,   when modifying the measured values depending on the row regions, a linear fitting line and an average value are obtained from the measured values, and the measured values of the density of the row regions are modified depending on a difference between a value of the linear fitting line in each of the row regions and the average value,   the linear fitting line is calculated based on the least-square method,   the first region is a region including a first dot row formed by first printing, and   the second region is a region consisting of a second dot row formed by second printing that is different from the first printing.   
   
   
       11 . A printing method, comprising:
 reading by a scanner a pattern that consists of a plurality of dot rows formed respectively in a plurality of row regions lined up in a direction intersecting a movement direction of nozzles;   measuring density of each of the row regions of the read pattern;   calculating a first correction value for correcting the density of a row region that is located in a first region of the pattern, based on a measured value of the density of that row region that is located in the first region;   calculating a second correction value for correcting the density of a row region that is located in a second region contiguous to the first region, based on a measured value of the density of that row region and a measured value of the density of another row region that is located in the second region;   modifying at least one of the first correction value and the second correction value in order to reduce a difference between the first correction value and the second correction value;   when forming a print image on a medium, forming a dot row that is located in the first region and that the print image consists of, based on the first correction value corresponding to the row region in which that dot row is to be formed; and   forming a dot row that is located in the second region and that the print image consists of, based on the second correction value corresponding to the row region in which that dot row is to be formed.   
   
   
       12 . The printing method according to  claim 11 , wherein:
 at least one of the first correction value and the second correction value is modified in order to reduce a difference between an average value of a plurality of the first correction values and an average value of a plurality of the second correction values.   
   
   
       13 . The printing method according to  claim 12 , wherein:
 the difference between the average value of the first correction values and the average value of the second correction values is determined as a modification value; and   at least one of the first correction value and the second correction value is modified based on the modification value.   
   
   
       14 . The printing method according to  claim 11 , wherein:
 in order to reduce a difference between the first correction value of a row region that is located in the first region and is contiguous to the second region and the second correction value of a row region that is located in the second region and is contiguous to the first region, at least one of the first correction value and the second correction value is modified.   
   
   
       15 . The printing method according to according to  claim 14 , wherein:
 the difference between the first correction value of the row region that is located in the first region and is contiguous to the second region and the second correction value of the row region that is located in the second region and is contiguous to the first region is determined as a modification value; and   at least one of the first correction value and the second correction value is modified based on the modification value.   
   
   
       16 . The printing method according to  claim 11 , wherein:
 the measured values of the density of each of the row regions are modified depending on the row regions; and   the first correction value and the second correction value are calculated based on the modified measured values.   
   
   
       17 . The printing method according to  claim 16 , wherein:
 when modifying the measured values depending on the row regions, a linear fitting line and an average value are obtained from the measured values, and the measured values of the density of the row regions are modified depending on a difference between a value of the linear fitting line in each of the row regions and the average value.   
   
   
       18 . The printing method according to  claim 17 , wherein:
 the linear fitting line is calculated based on the least-square method.   
   
   
       19 . The printing method according to  claim 11 , wherein:
 the first region is a region including a first dot row formed by first printing; and   the second region is a region consisting of a second dot row formed by second printing that is different from the first printing.   
   
   
       20 . A printing apparatus comprising:
 a memory; and   a plurality of nozzles,   wherein:
 the printing apparatus forms a pattern that consists of a plurality of dot rows formed respectively in a plurality of row regions lined up in a direction interescting a movement direction of the nozzles, 
 a scanner reads the pattern; 
 the memory stores at least one modified correction value obtained by:
 measuring density of each of the row regions of the read pattern; 
 calculating a first correction value for correcting the density of a row region that is located in a first region of the pattern, based on a measured value of the density of that row region that is located in the first region; 
 calculating a second correction value for correcting the density of a row region that is located in a second region contiguous to the first region, based on a measured value of the density of that row region and a measured value of the density of another row region that is located in the second region; and 
 modifying at least one of the first correction value and the second correction value in order to reduce a difference between the first correction value and the second correction value, thereby forming the at least one modified correction value.