Fluorescence detection device and fluorescence detection method

A fluorescence detection device by processing a fluorescent signal obtained by receiving fluorescence emitted by a measurement object which is irradiated with laser light, the device comprising:

• a light source unit operable to emit laser light with which a measurement object is irradiated while modulating an intensity of the laser light;
• a light-receiving unit operable to output a fluorescent signal of fluorescence emitted by the measurement object irradiated with the laser light;
• a light source control unit operable to generate a modulating signal for modulating the intensity of the laser light emitted from the light source unit;
• a first processing unit that includes an amplifier that amplifies the fluorescent signal outputted by the light-receiving unit, a mixer that generates a component of the amplified fluorescent signal in phase with the modulation signal and a 90 degrees phase-shifted component of the amplified fluorescent signal which is phase-shifted by 90 degrees with respect to the modulation signal, and an AD converter that digitizes the generated in-phase component and 90 degrees phase-shifted component;
• a second processing unit operable to calculate, by using the digitized in-phase component and the 90 degrees phase-shifted component, a fluorescence intensity signal and a phase delay of the fluorescence with respect to the modulation signal and operable to calculate, by using the calculated fluorescence intensity signal and the phase delay, a fluorescence intensity and a fluorescence relaxation time of the fluorescence emitted by the measurement object;
• and
• a signal control unit operable to control an operation amount of at least one of a signal level of a DC component of the modulation signal used for intensity modulation and a gain of the amplifier so that a value of the fluorescence intensity signal falls within a preset range.