Fig. 3.

Effective absorption optimization with consideration of the absorption spectrum of PpIX and power increase. As current is increased, the optical power is also increased, but effective PpIX activation is also impacted by spectral shifts in LED emission with increasing current. (a) Overlap in PpIX absorption spectrum and LED emission spectrum at 7A operating current. The overlapped area under PpIX and each LED spectral is the effective absorption for the specific LED spectrum. (b) Calculated effective PpIX absorption over a range of LED driving currents shows saturation at high currents and suggests there is no benefit in driving the LED at higher than approximately 7A.