Image forming apparatus to detect widths of recording material

An image forming apparatus comprising:

• a control unit configured to control an image formation on a recording material;
• a stack portion on which the recording material is to be stacked;
• a regulation portion configured to regulate a position of an edge of the recording material stacked on the stack portion;
• a detection unit configured to detect the position of the edge of the recording material regulated by the regulation portion, and to output a detection signal, having a value, in accordance with the detected position of the edge;
• and
• a storage unit configured to store difference information in association with values of the detection signal,
• wherein the difference information is calculated in advance by the control unit as a difference between a first width of the recording material, which is calculated based on the detection signal output from the detection unit, and second width of the recording material which is measured,
• wherein the control unit is configured to calculate difference information in accordance with the value of the detection signal output from the detection unit by reading out two values of the detection signal, which are previously stored in the storage unit and immediately adjacent the value of the detection signal output from the detection unit, and difference information, which are associated with the two values, respectively, from the storage unit, and performing linear interpolation in accordance with the value of the detection signal output from the detection unit, and
• wherein the control unit is configured to obtain a third width of the recording material by correcting the first width of the recording material based on the difference information calculated by the control unit in accordance with the value of the detection signal output from the detection unit.