| 摘要 |
An image forming apparatus is arranged to form an image with laser light emitted from a semiconductor laser source, and is constructed so as to protect the laser source from a breakdown, by regulating electric current flowing to the laser source no matter when an adjusting circuit for adjusting the light amount of the semiconductor laser source is apt to supply the electric current that could break the laser source, to the laser source. The apparatus is constructed in such structure that during an automatic light amount control period the laser light amount emitted from the semiconductor laser source is detected and a current source circuit is made inactive when the light amount detected is over a set light amount and that during periods other than the control period the electric current flowing to the semiconductor laser is detected and the current source circuit is made inactive when the light amount detected becomes over a fixed ratio times the current detected during the automatic light amount control period. In this way, the protection circuit can operate effectively anytime of emission of the laser source, so as to protect the laser source from the breakdown.
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