| 摘要 |
PROBLEM TO BE SOLVED: To detect abnormal state of light beam accurately by driving any one of a plurality of light beams in a prescribed region and recording a test pattern. SOLUTION: When a test pattern signal 334 becomes TRUE, a laser A records black pixels at a constant interval in main scanning direction and driving of a laser B is prohibited during that interval. When a laser B is turned on/off according to a test pattern signal 335, driving of the laser A is prohibited so that longitudinal lines are printed in the upper and lower regions on a paper, respectively, by the lasers A and B. Deterioration of the laser B can be checked because lower half of the paper plane is rendered pure white due to deteriorated beam when the laser is not lighted perfectly. Transient state before deterioration can be determined because thin longitudinal lines are printed in that region. |
