| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus such as a printer, which shortens a time required for detecting whether printing has already been made on recording paper, and which reduces manufacturing costs by downsizing a sensor necessary for detection. <P>SOLUTION: In the formation of an image on the recording paper P, bar code-type discrimination marks 41 and 42 for discriminating between printed and unprinted statuses are preprinted at the upper and lower ends of the recording paper P: it is detected whether or not the printing has already been done on the front and back sides of the recording paper P, on the basis of read data on one line 33 along the carrying direction E of the recording paper P. Thus, the image forming apparatus can make a time for reading data, required for detection, shorter than a conventional image forming apparatus which detects whether or not the printing has already been done on the recording paper on the basis of read data on the whole image forming surface. The manufacturing costs is reduced by downsizing the sensors 31 and 32 necessary for the detection. <P>COPYRIGHT: (C)2007,JPO&INPIT |
