Implementation and uniformity calibration of LED array for photodynamic therapy

Irradiance uniformity is an important parameter for a Photodynamic Therapy (PDT) device. The calibration and verification of a LED array light source based on computer vision technology were implemented and carried out. First, the correlation coefficients between the pulse width modulate value and the irradiance were calibrated. Then, the correction of the actual light center and divergence angle were solved by image processing to reduce errors from each LED lens. Finally, uniformity was optimized according to the irradiance formula of the Lambertian source. The lowest coefficients of variation of irradiance were 4.87% in a 5cm×12cm area and 3.55% in a 3cm×10cm area within the depth range of 8-12cm when the expected irradiance was 100mW/cm2. This finding indicated that the light source can achieve a more uniform illumination and provide a better therapeutic effect for the PDT of port-wine stains.