| 摘要 |
PURPOSE:To detect the deterioration in performance of a laser beam generating means without intermission of a recording job by providing a detecting circuit detecting a difference between an output of a measuring device when a prescribed density value is inputted to a semiconductor laser drive circuit and a predetermined reference value in response to the inputted prescribed density value. CONSTITUTION:A density signal A corresponding to recording information is given to a semiconductor laser drive circuit 3 over a time T1 after a time t1 is elapsed after a photodiode 7 detects a laser beam every time the laser beam scans a photosensitive body 1, resulting in that an electrostatic latent image in response to the recording density is formed on the photosensitive body 1. After the photodiode 7 detects the laser beam and a time t2 is elapsed, a prescribed density B generated by a density generator 8 is given to the semiconductor laser drive circuit 3 by a gate circuit 9 over the time T2. The output of the semiconductor laser 2 is measured by a photodiode 10, the difference with a reference value is detected by a detecting circuit 11, and when the difference exceeds a prescribed value, an alarm circuit 12 raises an alarm.
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