LAUSR

Monitoring-based preventive medicine relies heavily on minimal or noninvasive, portable, and cost-effective measurement solutions. In this study, we present a handheld multiwavelength fluorescence measurement system for detection of dermally injected fluorescent tracers. The circular detection area of the device is positioned on the sample containing the fluorescent marker. The marker is excited at regular intervals by a pulse of light. The optical output power is controlled by a laser diode driver, which receives direct feedback on the emitted light intensity from the monitor photodiode integrated into the laser diode package. An optical diffuser is located in front of each laser diode to ensure uniform illumination of the measurement area. Pulsed excitation of the fluorescent tracer allows alternate measurement of foreground and background light intensity. By subtracting the background from the foreground and using a switched-input photocurrent measurement technique, the measured photocurrent represents the actual light emission from the marker. The instrument has interchangeable modules that contain the excitation electronics and emission filter. These modules allow the instrument to be configured for a variety of different fluorescent markers. In vitro measurements show that the device is capable of performing fluorescence measurements for its intended use as a point-of-care device in preventive medicine.