Design of a Multi-Wavelength LED Photo-Rejuvenating System

To realize cosmetic phototherapy, a multi-wavelength LED cold light source design method is proposed in this work, which combines the 455nm, 595nm, 630nm, 661nm, and 828nm LED chips into a single light module. Compared with the conventional phototherapies using laser or intense pulsed light, the proposed light source has the advantages of improved safety and longer life time. The electrical design to drive the system is also proposed. The system can be used in different photo-rejuvenating applications, e.g. whitening and tendering skin, treating acne, by choosing different wavelengths. Another feature of this system is that the temperature of skin area exposed to the light can be monitored in real time. Experiments have been implemented to test the radiant power density and uniformity. The results show that the maximally achievable power density of the system is about 75mW/cm²; and the uniformity of spot is above 80%.