PURPOSE: To measure accurately the intensity of an optical pulse without reference to a pulse duty ratio by generating a trigger pulse signal when the peak level of a photodetection pulse signal is larger than that of a fed-back reference signal.
CONSTITUTION: A photodetecting element 1 photodetects an optical pulse L inputted periodically; and generates a photodetection pulse signal Vi. A trigger pulse generating circuit 2 inputs the signal Vi and generates a trigger pulse signal V2 when its peak level is larger than the reference signal Vr. An extension pulse generating circuit 3 is operated with the signal V2 and generates an extension pulse signal V3 whose pulse width is somewhat larger than the period of the pulse light L. A light intensity output circuit 4 outputs a light intensity signal Vo which increases with a specific gradient during the input of the signal V3 and decreases with a specific gradient in other cases. The signal Vo, on the other hand, is fed back to the circuit 2 as the reference signal Vr by the circuit 5. Then, the signal Vo varies following up the peak level of the signal Vi, so the intensity of the pulse light is known accurately without reference to the pulse duty ratio of the pulse light L.
KAGO YOSHIYUKI
ONOKI NOBUYOSHI
NIPPON DENSO CO