| 摘要 |
PURPOSE:To detect a dot omission of printing and an omitted character, which are caused by a fault of an optical system, by comparing an output signal of an ineffective light detected by a detector, with a dot printing information, detecting its difference, and detecting an abnormal state of an effective light. CONSTITUTION:A laser light outputted from a laser generator 1 passes through a condensing part 21, is condensed in the shape of a beam and reaches a polarizer 22. On the other hand, a printing information A from a logical circuit is inputted to a driving part 23 and a comparing transistor TR62, the driving part 23 controls the polarizer 22 so as to obtain an effective light B for executing a printing which synchronizes with a dot printing signal P1 of the information A, and also the beam-shaped laser light is controlled so as to be cut off by a slit plate 3 between adjacent signals P1. An ineffective light C cut off by this slit plate 3 is detected 4, converted to a corresponding electric signal, an output of the detector 4 is inverted by 180 degrees as to its phase by an inversion inverter 61, outputted to the TR62, compared with the information A, its difference is detected, and an abnormal state of the effective light B is detected. |
