Mass Spectrometry & Spectroscopy


Sun, Safety, Spectroscopy - The Science of


UV Measurement and Assessing Sun Protection Dieter Bingemann, PhD, Applications Scientist, Ocean Optics; Yvette Mattley, PhD, Principal Applications Scientist, Ocean Optics.


The long hot days of summer may be waning, but the effects of summer UV exposure, accelerated aging and deadly melanoma, can linger on. Many of us try our best to avoid the worst of this damage by donning sunglasses and slathering on the sunscreen, but just how effective are the products people rely on to protect themselves? Spectroscopy can tell us. The versatility of miniature spectroscopy can be used to characterise the amount of protection common interventions like sunglasses and sunscreen can provide.


With a plethora of these products in the market, at varying price points and protection factors, it’s diffi cult to gauge their effectiveness. But with miniature spectroscopy, the UV transmission properties of sunglass lenses and sunscreen can be quantifi ed and assessed.


Assessing UV Protection of Sunglasses


Sunglasses often are treated as fashion accessories or a means to simply block out irritating light. However, their most important job is to block UV radiation from the sun. Good eye protection prevents cataracts, benign growths on the eye’s surface, and photokeratitis -temporary but painful sunburn of the eye’s surface.


UV protection can be manufactured into sunglasses lenses, altering the capacity of the lenses to absorb UV radiation. Various additional coatings may be added to reduce glare, remove polarisation, or add colour. However, those coatings do not signifi cantly contribute to blocking UV radiation.


Transmission of UV and Vis-NIR wavelengths in sunglasses is regulated in many countries. With sunglasses, the focus is on the capacity of the lenses to absorb UV radiation, which can harm the eyes. Since most UVC radiation (100-280 nm) is blocked by the Earth’s ozone layer, the emphasis is on UVA (315-400 nm) and UVB (280-315 nm) wavelengths. With the range of options and price points available in sunglasses, it’s diffi cult for the consumer to know which will be most effective in the critical UVA-UVB range. A simple setup with a modular spectrometer can measure the transmission characteristics of sunglass lenses.


Characterising UV Transmission of Sunglasses


We used a compact, modular spectrometer to characterise transmission over the UV-Vis-NIR (200-1000 nm) range. A deuterium tungsten halogen light source was paired with a balancing fi lter to provide illumination over a wide range (~230-2500 nm), simulating exposure to sunlight. An integrating sphere was introduced to


measure transmission through the curved, irregular surfaces of the sample sunglass lenses. An integrating sphere ensures repeatability of measurements, even when refl ectivity of the sample changes at different viewing angles. Light was delivered via a collimating lens through the sample sunglasses and into the integrating sphere, which was coupled to the spectrometer. Each sample was measured in three different locations and the results were averaged.


To evaluate a range of eyewear options, six samples ranging from discount store sunglasses to luxury brand eyewear were tested:


Table 1. Sample Eyewear Eyewear Type


Inexpensive sunglasses with black lenses


Plastic lab safety glasses (standard lab eyewear protection against chemicals or projectiles)


Plastic UV blocking eyewear (designed for use with UV sources)


Progressive lens prescription eyewear with Transitions®


coating that darkens with exposure to UV light


Luxury brand polarised sunglasses with blue glass lenses


Luxury brand polarised sunglasses with grey plastic lenses


$350 $125


Estimated Price in US$


$1 $10 $30 $300


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