| 摘要 |
PROBLEM TO BE SOLVED: To render double protection with a simple constitution, as compared with a prior art. SOLUTION: An aligner includes: a motor 38 including a Hall element H1 for detecting the rotating speed of a rotor 50 in the state where power is supplied from a power source 52, and outputting a signal showing the rotating speed, a Hall element H4 for detecting the rotating speed of the rotor 50 in the state where power is supplied from a power source 56 different from the first power source (power source 52), and outputting a signal showing the rotating speed, and a PLL circuit 60 for detecting whether or not the rotating speed of a polygon mirror 36 reaches a target rotating speed required for image formation based on the signal showing the rotating speed, output from the Hall element H1; a signal output circuit 44 for detecting whether or not the rotating speed of the motor 38 is equal to or more than a predetermined threshold; and a laser diode driver 40 that controls a laser diode 34 so that light corresponding to image information may be emitted from the laser diode 34 only when detecting that the rotating speed is equal to or more than the predetermined threshold. COPYRIGHT: (C)2010,JPO&INPIT |
