Low-cost, frequency-domain, fluorescence lifetime confocal microscopy

We describe the theory and implementation of a frequency-domain fluorescence lifetime confocal microscope using switched diode laser illumination. Standard, communications-type, radio-frequency electronics are used to provide inexpensive modulation references and to perform phase-sensitive detection. This allows the rapid acquisition of fluorescence intensity and lifetime images and their display in real time. We show fluorescence lifetime images of bead objects and fluorescence lifetime images of biological specimens from a single confocal scan.