The Improvement of the Irradiance Uniformity in LED Phototherapy to Match the Standard Requirements

Abstract

Light Emitting Diode (LED) phototherapy (SEDRA 811) luminaire from Medical Engineering Group (MEG) was improved after the collaboration between the R&D group of MEG and National Institute for Standards (NIS). The initial LED luminaire consists of 10 Blue super LEDs which provide irradiance levels of 332 to 5719 µW/cm2±4.5% distributed over the effective surface area (treatment bed). The uniformity of these irradiance levels were 0.06 at the total effective area and 0.2 at central area. A new design of the LEDs position over the luminaire using elliptical lenses improves the irradiance uniformity to 3.7 times. At the new design the overall irradiance distribution was improved, the high irradiance levels areas shared their intensities with their neighbors of low irradiance levels. So while the high areas were reduced by 42%, the low ones were increased by 54%. As a result the new design provides more homogenous irradiance levels lying in the intensive levels. Also it provides the uniformity to reach 0.4 (the accepted border) at the central area (20 X 40 cm).