Patent ID: 8330124

Claim:
A fluorescence detection device using intensity-modulated laser light, which irradiates a measurement object with laser light, receives fluorescence emitted from the measurement object to obtain a fluorescent signal, and determines fluorescence relaxation time from the fluorescent signal, the device comprising: a laser light source unit emitting intensity-modulated laser light with which a measurement object is to be irradiated; a light-receiving unit outputting a fluorescent signal of fluorescence emitted from the measurement object irradiated with the intensity-modulated laser light; a signal generating unit generating a modulation signal having a predetermined frequency to modulate an intensity of laser light emitted from the laser light source unit and further generating, separately from the modulation signal, a reference signal having a frequency identical or almost identical with that of the modulation signal and synchronized with the modulation signal; a signal processing unit performing first mixing processing to mix the reference signal and the fluorescent signal outputted by the light-receiving unit by irradiating the measurement object with the laser light whose intensity has been modulated using the modulation signal, and further performing, on a mixed signal resulted from the first mixing processing, first low-pass filtering to remove a signal component having a sum frequency of a frequency of the modulation signal and a frequency of the reference signal to output a fluorescent signal-based low-frequency signal; and a fluorescence detection unit calculating a phase of the fluorescent signal relative to the modulation signal using the fluorescent signal-based low-frequency signal to determine, from the calculated phase, a fluorescence relaxation time of the fluorescence emitted from the measurement object.