DISCUSSION
UV Light Sources. Emissions from the widely used mercury-based UV lamps (GIA and UVP Mineralight lamps) do not contain pure 365 nm LWUV and 254 nm SWUV peaks, but instead show multiple excitation energies of widely varying bandwidths. Similarly, the popular LED UV loupe has a visible emission of 405 nm, rather than the standard for LWUV (365 nm). The emissions from GIA’s LED fluorescence meter and commercial LED light sources show a well-constrained LWUV emission in the 364–367 nm range. The variability in excitation wavelengths and bandwidths among commonly used lamps and LED UV sources demonstrates that the colors and intensities of observed fluorescence in a single sample can vary depending on the light source. UV lamp emissions tend to fluctuate according to the age of the bulbs and filters as well as warm-up times, making it very difficult to achieve consistent results from one source to another. LED sources are far more constrained in emission bandwidth and purity, but they are manufactured in such a wide range of wavelengths that consistency among different products remains a problem. Nevertheless, the well-controlled emissions suggest that LEDs can provide better accuracy and consistency in interpreting the fluorescence response to a LWUV source, as long as an LED near 365 nm is used.
DISCUSSIONUV Light Sources. Emissions from the widely used mercury-based UV lamps (GIA and UVP Mineralight lamps) do not contain pure 365 nm LWUV and 254 nm SWUV peaks, but instead show multiple excitation energies of widely varying bandwidths. Similarly, the popular LED UV loupe has a visible emission of 405 nm, rather than the standard for LWUV (365 nm). The emissions from GIA’s LED fluorescence meter and commercial LED light sources show a well-constrained LWUV emission in the 364–367 nm range. The variability in excitation wavelengths and bandwidths among commonly used lamps and LED UV sources demonstrates that the colors and intensities of observed fluorescence in a single sample can vary depending on the light source. UV lamp emissions tend to fluctuate according to the age of the bulbs and filters as well as warm-up times, making it very difficult to achieve consistent results from one source to another. LED sources are far more constrained in emission bandwidth and purity, but they are manufactured in such a wide range of wavelengths that consistency among different products remains a problem. Nevertheless, the well-controlled emissions suggest that LEDs can provide better accuracy and consistency in interpreting the fluorescence response to a LWUV source, as long as an LED near 365 nm is used.
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