Reading device, image forming apparatus, position detecting method, and recording medium storing program code

A method of detection position comprising:

• detecting a reference pattern of a position reference member using a reader, the reference pattern having a line extending along a first direction of the position reference member, the position reference member movable in a second direction orthogonal to the first direction, relative to the reader including a plurality of pixels;
• determining coordinates of at least two pixels in the second direction, based on the detected reference pattern of the position reference member;
• calculating a first correction value in the second direction at a pixel to be used at least for detecting a position of a conveyed object, based on the coordinates determined for the at least two pixels of the reader in the second direction;
• detecting an outer shape of the conveyed object and a position of an image pattern on the conveyed object based on data read by the reader;
• obtaining a difference between an image of the conveyed object, of which a shape has been corrected based on the position detected by using the first correction value, and an image of the conveyed object, of which a shape has not been corrected;
• and
• setting a second correction value based on the obtained difference, the first correction value and the second correction value being used to detect the position of the conveyed object.

A non-transitory recording medium storing a program for causing a computer to carry out:

• detect a reference pattern of a position reference member using a reader, the reference pattern having a line extending along a first direction of the position reference member, the position reference member movable in a second direction orthogonal to the first direction, relative to the reader including a plurality of pixels;
• determine coordinates of at least two pixels in the second direction, based on the detected reference pattern of the position reference member;
• calculate a first correction value in the second direction at a pixel to be used at least for detecting a position of a conveyed object, based on the coordinates determined for the at least two pixels of the reader in the second direction;
• detect an outer shape of the conveyed object and a position of an image pattern on the conveyed object based on data read by the reader;
• obtain a difference between an image of the conveyed object, of which a shape has been corrected based on the position detected by using the first correction value, and an image of the conveyed object, of which a shape has not been corrected;
• and
• set a second correction value based on the obtained difference, the first correction value and the second correction value being used to detect the position of the conveyed object.