This research article proposes an alternative method to measure the discoloration or the color changes of EBT3 films due
to exposure by solar ultraviolet (UV A+B) dose. Common methods to measure the color changes of EBT3 are through
imaging technique measured by flatbed scanner and through absorbance spectroscopy measured by visible spectrometer.
The research presented in this article measure the color changes of EBT3 through simplified optical system using the
combination of light emitting diode (LED) as the light source and photodiode as the detector. In this research, 50 pieces
of Gafchromic EBT3 films were prepared with the dimension of 3 cm x 2 cm. Color of the films changed from light
green to dark green based on the total accumulated UV dose (mJ/cm2) by each film that depends on the duration of
exposure, irradiance level (mW/cm2) and condition of the sky. The exposed films were then taken to the laboratory for its
color measurement using absorbance spectroscopy technique and using newly developed simplified optical instrument
using LED-photodiode. Results from spectroscopy technique indicate that wavelength within red region exhibit better
response in term of linearity and responsivity towards the colors of EBT3 films. Wavelength of 626 nm was then
selected as the peak emission wavelength for LED-photodiode absorbance system. UV dose measurement using LEDphotodiode
system produced good result with coefficient of determination, R2 of 0.97 and root mean square of error,
RMSE of 431.82 mJ/cm2 while comparatively, similar wavelength but analyzed from spectroscopy dataset produced R2
of 0.988 and RMSE of 268.94 mJ/cm2.
Ahmad Fairuz Omar, Ummi Shuhada Osman, and Kok Chooi Tan, "Characterizing the discoloration of EBT3 films in solar UV A+B measurement using red LED," Proc. SPIE 10425, Optics in Atmospheric Propagation and Adaptive Systems XX, 1042505 (Presented at SPIE Remote Sensing: September 13, 2017; Published: 29 September 2017); https://doi.org/10.1117/12.2278160.
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