Image forming apparatus having light emission control and image forming method

Abstract

An image forming apparatus includes a plurality of print heads, a sensor, a processor, and an image forming unit. The plurality of print heads are arranged in parallel. The sensor detects a color shift amount of each color to be printed by the plurality of print heads in a main scanning direction based on an output result of a test pattern by the plurality of print heads. The processor sets a color shift correction value for correcting the color shift amount on the basis of a color having a largest color shift amount. The processor controls light emission of the plurality of print heads based on the color shift correction value and image data. The image forming unit forms an image based on the image data on a sheet by light emission of the plurality of print heads.

1 . An image forming apparatus comprising:
 an image forming unit configured to form an image on a sheet based on image data, the image forming unit comprising a plurality of print heads arranged in parallel;   each of the plurality of print heads configured to emit light through a transfer medium to print a color based on the image data in a valid image area commonly covered by the plurality of print heads;   a sensor configured to detect a color shift amount of each color to be printed by the plurality of print heads in a main scanning direction based on a test pattern result printed by the plurality of print heads; and   a processor configured to:
 detect the valid image area commonly covered by the plurality of print heads based on the test pattern result; 
 determine, based on a corresponding color having a largest color shift amount, a color shift correction value for correcting the color shift amount, 
 set the color shift correction value for correcting the color shift amount so that an image of each color in the main scanning direction falls within a range of the valid image area, and 
 control light emission of the plurality of print heads based on the color shift correction value and image data. 
   
     
     
         2 . The image forming apparatus according to  claim 1 , further comprising:
 an interface configured to acquire a displacement correction value for correcting a displacement amount of the image in the main scanning direction with respect to the sheet, wherein   the processor is configured to control the light emission of the plurality of print heads based on the color shift correction value, the displacement correction value, and the image data.   
     
     
         3 . The image forming apparatus according to  claim 2 , wherein
 the interface is configured to acquire the displacement correction value based on the test pattern result.   
     
     
         4 . The image forming apparatus according to  claim 2 , wherein
 the processor is configured to change the displacement correction value acquired by the interface so that the image of each color in the main scanning direction falls within the range of the valid image area.   
     
     
         5 . The image forming apparatus according to  claim 2 , wherein
 the interface is configured to set a validity setting as valid or invalid for displacement correction, and   the processor is configured to control the light emission of the plurality of print heads based on the color shift correction value, the displacement correction value, and the image data corresponding to the validity setting.   
     
     
         6 . The image forming apparatus according to  claim 5 , wherein the processor is configured to set the validity setting of displacement correction to be valid when an image is formed on a sheet of a first size in the main scanning direction. 
     
     
         7 . The image forming apparatus according to  claim 5 , wherein the processor is configured to set the validity setting of displacement correction to be invalid when an image is formed on a sheet of a second size smaller than the first size in the main scanning direction. 
     
     
         8 . An image forming method comprising:
 forming, at an image forming unit, an image on a sheet based on image data by light emission of a plurality of print heads through a transfer medium, the print heads being arranged in parallel;   detecting, at a sensor, a color shift amount of color to be printed by each of the plurality of print heads in a main scanning direction based on a test pattern result printed by the plurality of print heads;   detect, by a processor, a valid image area commonly covered by the plurality of print heads based on the test pattern result;   setting, by the processor, a color shift correction value for correcting the color shift amount on the basis of a color having a largest color shift amount so that an image of each color in the main scanning direction falls within a range of the valid image area commonly covered by the plurality of print heads; and   controlling, by the processor, light emission of the plurality of print heads based on the color shift correction value and the image data.   
     
     
         9 . The method according to  claim 8 , further comprising:
 acquiring, by an interface, a displacement correction value for correcting a displacement amount of the image in the main scanning direction with respect to the sheet; and   controlling, by the processor, the light emission of the plurality of print heads based on the color shift correction value, the displacement correction value, and the image data.   
     
     
         10 . The method according to  claim 9 , wherein
 acquiring the displacement correction value comprises determining the displacement correction value based on the test pattern result.   
     
     
         11 . The method according to  claim 9 , further comprising
 adjusting, by the processor, the displacement correction value acquired by the interface such that the image of each color in the main scanning direction falls within the range of the valid image area.   
     
     
         12 . The method according to  claim 9 , further comprising:
 setting, by the interface, a validity setting as valid or invalid for displacement correction; and   controlling, by the processor, the light emission of the plurality of print heads based on the color shift correction value, the displacement correction value, and the image data corresponding to the validity setting.   
     
     
         13 . The method according to  claim 12 , wherein the validity setting of displacement correction is valid when an image is formed on a sheet of a first size in the main scanning direction. 
     
     
         14 . The method according to  claim 12 , wherein the validity setting of displacement correction is invalid when an image is formed on a sheet of a second size smaller than the first size in the main scanning direction.