Sunglasses

The olive trees are a traditional crop of the Mediterranean landscape with olive oil being the primary source of fat and one of the major components of the Mediterranean diet [1]. The major components of olive oil are the fatty acids, of which oleic acid (mono-unsaturated fatty acid) represents 55 to 83%, linoleic acid (poly-unsaturated fatty acid) represents 4 to 21% and palmitic acid (saturated fatty acid) represents 7.5 to 20%, see Figure 1. Owing to the high amount of mono-unsaturated fatty acids, olive oil has antioxidant and anti-inflammatory properties and is essential to reduce bad cholesterol levels, therefore decreasing the risk of cardiovascular diseases [2].

Figure 1 – Rule Gratings

Mid-range UV wavelengths (UV-B) ranges from 280 to 315 nm and contributes around 5% to the total UV light that reaches our planet’s surface. The large fraction of UV light that reaches the planet’s surface (UV-A) ranges from 315 to 400 nm and contributes up to 95% of total UV light [1-3]. When the wavelength decreases, the spectral energy increases, and higher spectral energy raises the potential for eye damage. For ophthalmic standards, the International Organization for Standardization (ISO) 8980/3 outlines the attenuation of solar radiation for optical products at 380 nm.

However, due to the potential danger of UV-A, several organizations (World Health Organization, European Council of Optometry and Optics, and others) adopted the attenuation of solar radiation for optical products at 400 nm [4,5].

In this application note, we combine DWHP light source with a FLEX spectrometer and two lens holder to investigate the amount of ultraviolet and visible light that pass through an optical sun lens of five different sunglasses.

Figure 2 – Holographic Gratings

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The amount of dispersion (also known as groove density or groove frequency) is usually expressed in nm/mm and determines the range of wavelengths that are dispersed by the grating into the detector. It increases with the increase of the groove density (lines/mm), which allows an improvement of the resolution for a certain slit width. On the other hand, groove density also defines the operational range of wavelengths of the grating being, therefore, an important parameter not only to determine the optical resolution of the spectrometer but also to set the range of wavelengths in which it works. In this sense, increasing the groove density (higher than 1200 lines/mm) leads to a higher spectral resolution value and a small operational wavelength range of the spectrometer. In contrast, decreasing the groove density (lower than 1200 lines/mm) leads to a lower spectral resolution value and a higher operational wavelength range of the spectrometer, see Figure  3.

Figure 3 – Absolute efficiency curve of two holographic gratings, the first with 600 grooves/mm (orange line) and the second with 1800 grooves/mm (blue line).

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The amount of dispersion (also known as groove density or groove frequency) is usually expressed in nm/mm and determines the range of wavelengths that are dispersed by the grating into the detector. It increases with the increase of the groove density (lines/mm), which allows an improvement of the resolution for a certain slit width. On the other hand, groove density also defines the operational range of wavelengths of the grating being, therefore, an important parameter not only to determine the optical resolution of the spectrometer but also to set the range of wavelengths in which it works. In this sense, increasing the groove density (higher than 1200 lines/mm) leads to a higher spectral resolution value and a small operational wavelength range of the spectrometer. In contrast, decreasing the groove density (lower than 1200 lines/mm) leads to a lower spectral resolution value and a higher operational wavelength range of the spectrometer, see Figure  3.

Figure 3 – Absolute efficiency curve of two holographic gratings, the first with 600 grooves/mm (orange line) and the second with 1800 grooves/mm (blue line).

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