To detect intensity of incident light with high precision while a light intensity range able to correspond (dynamic range) is wide.
This device is provided with an avalanche photodiode(APD) 2 detecting the test specimen light entering through a converging optical system 1, a bias voltage setting circuit 6 setting the bias voltage, an amplifier 4 amplifying the output signal from the APD2 in a specified manner, and a pulse counter 5 counting the pulse wave contained in the amplified signal. At this time, a control means 7, which controls the bias voltage setting circuit 6 from the intensity of the test specimen light made incident on the APD2, in detecting intensity of the test specimen light from the count value of the pulse counter 5, and so adjusts the bias voltage for the APD2 that the output signal of the APD2 shows linearity to the intensity of the to-be-measured light, is provided.
SAITO YASUNORI
TANAKA KOKI
SAITO YASUNORI
HIOKI ELECTRIC WORKS