| 摘要 |
PROBLEM TO BE SOLVED: To prevent a sheet of paper whose both surfaces are already printed from being erroneously printed, even if this paper coexists in a paper feeding tray by deciding whether the front and rear surfaces of the paper are already printed or not. SOLUTION: When the top end of the paper reaches an image detecting part 134A, this image detecting part 134A is started to scan a surface subject to the printing from its top end to its rear end, so that the face that the surface subject to the printing is already printed or not is detected to inform an engine detecting part 131. This engine detecting part 131 starts a printing part 132, when it is decided that the surface subject to the printing is of a 'black paper', by referring to the result of the detection. Therefore, a toner image formed on a photoreceptor drum 203 is transferred onto the arrival paper and further, toner is fixed by a heating roller 204. On the other hand, when the result of the decision is recognized as 'the presence of an image', the printing part 132 is instructed to stop the printing, for stopping a printing operation and the paper is carried to a paper reverse part 135A. |
