PURPOSE: To enhance the visibility of a reference line being formed through repetitive scanning of laser luminous flux by detecting an acceleration/ deceleration region of the moving speed of laser luminous flux and varying the quantity of light emitted from a laser light source.
CONSTITUTION: A microcomputer 82 compares an angle detection signal from a rotational angle detection circuit 91 with an angle setting signal from a rotational angle setting circuit 96 and drives a motor reversely within the range of a set rotational angle. A motor drive current at the time of reverse driving detected by a drive current detection circuit 92 and having an absolute value higher than a predetermined value is then detected by an acceleration/ deceleration region detecting circuit 93 and pulsated before being outputted to the microcomputer 82 as an acceleration/deceleration signal. Upon receiving the acceleration/deceleration signal, the microcomputer 82 judges that the laser luminous flux shifted from a constant speed region has changed to an acceleration/deceleration region and puts out a lease diode 23 through a laser diode drive circuit 95 during provision of the acceleration/deceleration signal and then lights the diode 23. Consequently, a reference line having constant luminance and high visibility can be formed.
SAKAI TERUO
ITO EIICHI
TAKAHASHI KENSHO
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