Image forming apparatus which accepts multiple types of test sheets for calibration of image density and geometric characteristics

Abstract

An image forming apparatus includes an image forming unit configured to form an image, a conveying unit configured to convey a sheet on which the image is formed, a reader configured to read the sheet conveyed by the conveying unit and a controller. The controller is configured to execute first calibration in which a density of an image to be formed by the image forming unit is controlled based on a result of reading by the reader, and execute second calibration in which a geometric characteristic of an image to be formed by the image forming unit is controlled based on a result of reading by the reader. The controller allows usage of a sheet of a first type in the first type of calibration, wherein the controller prevents usage of a sheet of a second type in the first type of calibration.

What is claimed is: 
     
         1 . An image forming apparatus comprising:
 an image forming unit configured to form an image;   a conveying unit configured to convey a sheet on which the image is formed;   a reader configured to read the sheet conveyed by the conveying unit; and   a controller configured to:
 execute first calibration in which a density of an image to be formed by the image forming unit is controlled based on a result of reading by the reader; and 
 execute second calibration in which a geometric characteristic of an image to be formed by the image forming unit is controlled based on a result of reading by the reader, and 
   wherein the controller allows usage of a sheet of a first type in the first type of calibration,   wherein the controller prevents usage of a sheet of a second type in the first type of calibration,   wherein the controller allows usage of a sheet of the first type in the second type of calibration, and   wherein the controller allows usage of a sheet of the second type in the second type of calibration.   
     
     
         2 . The image forming apparatus according to  claim 1 , wherein a basis weight of the sheet of the second type is smaller than a basis weight of the sheet of the first type. 
     
     
         3 . The image forming apparatus according to  claim 1 ,
 wherein, in the first calibration, the controller controls the image forming unit to form a first test image, obtains first reading data related to the first test image on a sheet, and controls the density of an image to be formed by the image forming unit based on the first reading data, and   wherein, in the second calibration, the controller controls the image forming unit to for a second test image, obtains second reading data related to the second test image on a sheet, and controls the geometric characteristic of an image to be formed by the image forming unit.   
     
     
         4 . The image forming apparatus according to  claim 1 ,
 wherein, in the first calibration, the reader reads the sheet of the first type conveyed by the conveying unit, and   wherein, in the first calibration, the reader is prevented from reading the sheet of the second type conveyed by the conveying unit.   
     
     
         5 . The image forming apparatus according to  claim 1 ,
 wherein, in the first calibration, the controller is configured to perform a density control based on the result of reading the sheet of the first type, and   wherein, in the first calibration, the controller is configured to not perform a density control based on the result of reading the sheet of the second type.   
     
     
         6 . The image forming apparatus according to  claim 1 ,
 wherein the reader includes a sensor configured to read an original,   wherein the image forming unit is configured to form a copy image of an original based on reading data obtained by the sensor, and   wherein the conveying unit includes a document feeder configured to convey the original to the sensor.   
     
     
         7 . The image forming apparatus according to  claim 1 ,
 wherein the image forming unit includes a fixing device configured to fix the image, and   wherein the reader is arranged downstream of the fixing device in a direction of conveying the sheet by the conveying unit.   
     
     
         8 . The image forming apparatus according to  claim 1 , wherein, in the first calibration, the controller generates a tone correction table based on the result of reading by the reader.