Quantifying the properties of a dosimeter responsive to blue light hazard effective wavelengths

Quantifying the properties of a dosimeter responsive to
blue light hazard effective wavelengths

The research reported in this dissertation characterizes the properties of a proposed blue light dosimeter suitable for measuring the ocular blue light hazard. Blue light of high intensity with shorter wavelengths (400-500 nm) has been shown to produce an adverse effect on the healthy human eye, and the hypothesis proposed is that a dosimeter based on polysulphone and phenothiazine has the properties to act as a dosimeter to measure exposure to the blue light hazard. Exposure to the shorter wavelengths of blue light is
measured by weighting the spectral irradiance of a light source against the blue light hazard action spectrum, and the dosimeter employed in this study uses a long pass filter
to remove ultraviolet wavelengths shorter than 380 nm. An examination of the polysulphone and phenothiazine dosimeters was completed for the change in absorbance,
dose response, the dark reaction, repeatability of measurement, the influence of the angle of the receiving plane, and stability against changes in irradiation and temperature. The results show that a change in the dosimeter optical transmission occurs as a result of
exposure to blue light, with maximum dosimeter response after exposure to wavelengths around 420 nm. The polysulphone and phenothiazine dosimeters were exposed to four light sources and dose response calibration curves established that relate blue light exposure to the change in absorbance. The effect of the angle of the receiving plane was found to be approximated by a cosine function for angles up to 70º from the normal, with the difference between measured and theoretical values in this angle range being less than about 0.2. Dosimeter response to repeated solar radiation exposure was found to be reproducible with a standard error in the A of 0.005. The dark reaction of the dosimeter in terms of the average change in absorbance in darkness was also found to be small, with a change of 0.056 at zero hours being 0.058 after 24 hours and 0.067 after one week. Dosimeter rate variations with irradiance variations between 10 W/m² and 15 W/m² were found to be only ± 10 %, and thus within the measurement error of the badges. Dosimeter responses were also found to be stable for temperatures ranging from 23 ºC to 37 ºC. Taken together, all these results lead to the conclusion that polysulphone and phenothiazine dosimeters have characteristics that enable their widespread use for rapid,
convenient and low-cost assessment of the blue light hazard.