PURPOSE: To prevent the destruction of laser by inhibiting lighting of a semiconductor laser when an output voltage of a luminous energy monitoring circuit has exceeded beyond a fixed value.
CONSTITUTION: A forced lighting device Sc forces a laser 31 to light for a fixed period of time since a time in which a computer 52 runs in disorderly manner. An inhibit lighting signal Sf detects a level before the destruction of a laser 31 from a resultant laser luminous energy due to driving by the forced lighting signal Sc. Then the enforced inhibition of lighting of a laser 31 occurs. When the computer runs wild, a lighting signal is supplied to the laser 31 and synchronized to this, the level of a current control signal Sa on a current generation circuit 48 is raised gradually using a low pass filter 55. Thus even during the disorderly operation of the computer, the laser 31 is forced to light and a drive current does not flow abruptly in the laser 31. An inhibit lighting means 100 detects this disorderly runaway status halfway through the process of a gradual increase in the drive current, stopping drive of the laser 31.
MURAHASHI TAKASHI
NAKAZAWA TOSHIHIKO
| US4237427A | 1980-12-02 |
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