| 摘要 |
A liquid scintillation counter 10 serving as an optical measurement apparatus includes: an HPD 24, a charge amplifier 26, a voltage amplifier 28, a comparator 30, a counter 32, a multi-channel analyzer 34, a display 38, and the like. The HPD 24 has a photocathode 24 a and an APD 24 b for outputting a signal that corresponds to the number of incident photons. The comparator 30 outputs a logic pulse signal, serving as a comparison result signal, only when the signal outputted from the HPD 24 and amplified by the charge amplifier 26 and voltage amplifier 28 is larger than a prescribed threshold value. This threshold value is set larger than an output signal that is outputted when a single photoelectron is emitted from the photocathode 24 a and smaller than another output signal that is outputted when two or more photoelectrons are emitted.
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