To provide a light measuring instrument which can accurately measure the quantity of incident luminous flux.
This light measuring instrument 10 is equipped with a photon detection part 12 which outputs an output signal corresponding to the number of incident photons, a timing signal generating circuit 14 which generates a periodic signal having a period smaller than the duration of the output signal from the photon detection part 12 when one photon is made incident, an A/D converter 16 which converts the output signal from the photon detection part 12 from analog to digital according to the cycle signal generated by the timing signal generating circuit 14, an adder 18 which adds the output signal after the A/D conversion by the A/D converter 16, and a CPU 20 which counts photons made incident on the photon detection part 12 according to the addition signal outputted by the adder 18. The photon detection part 12 is equipped with an HPD (hybrid photodetector) 24 which detects photons and a TZ (transimpedance) amplifier 26 which amplifies the output signal from the HPD 24.
KAWAI KATSUHIKO
MORITA TETSUYA
OBA KOICHIRO
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