belong to the category of personal eye and face protection products. The technical indicators to measure their quality are mainly reflected in several aspects such as vertex power, UV protection, mechanical impact resistance, and whether they can block dazzling glare. 1. Lens ultraviolet transmittance detection principle. The transmittance measurement of sunglasses
lenses cannot be processed as a simple average of the spectral transmittance at each wavelength. Instead, it should be obtained by weighted integration of the spectral transmittance according to the weight of different wavelengths. The human eye is a simple optical system. When evaluating the quality of glasses
, the sensitivity of the human eye to light radiation of different wavelengths must first be considered. All in all, the human eye is sensitive to green light, so the transmittance of the green light band has a great influence on the light transmittance of the lens, that is, the weight of the green light band is greater; on the contrary, because the human eye is not sensitive to purple light and red light, so The transmittance of purple light and red light has a relatively small effect on the light transmittance of the lens, that is, the weight of the purple light and red light bands is also relatively small. An effective method for the anti-ultraviolet performance of lenses is to quantitatively determine and analyze the transmittance of UVA and UVB spectra. 2. Lens ultraviolet transmittance detection instrument and method can use the spectral transmittance tester to measure the spectral transmittance in the ultraviolet region to judge the quality of the ultraviolet transmittance of the sample. Connect the spectral transmittance meter to the computer serial port, start the operating program, perform environmental calibration at 23°C±5°C (before calibration, you must confirm that there is no lens or filter in the measurement part), and set the test wavelength range to 280～480 nm, observe the ultraviolet rays of the lens with the transmittance curve magnified. After that, place the tested lenses on the test rubber plugs to test the light transmittance (note: wipe the lenses and the test rubber plugs clean before testing). 3. Problems in the measurement of ultraviolet transmittance In sunglasses
, the transmittance calculation in the ultraviolet band adopts a simple average method of spectral transmittance and defines it as the average transmittance. In addition, the wavelength range of medium-wave ultraviolet (UN-B) specified by QB2457-99 is 290 nm to 315 nm. For the same sample under test, if the two definitions of QB2457 and IS08980-3 are used for measurement, the results of the ultraviolet band transmittance obtained are completely different. When measured in accordance with the definition of IS08980-3, the calculated result of the transmittance in the UV-B band is 60.7%; and if measured in accordance with the definition of QB2457, the calculated result of the transmittance in the UV-B band is 47.1 %. There is a 13.6% difference between the two results. It can be seen that the difference in the reference standard will directly lead to the difference in technical requirements and requirements, and ultimately affect the accuracy and objectivity of the measurement results. When measuring the transmittance of glasses products, this problem cannot be ignored. The transmittance of sunglasses
products and lens materials is tested and analyzed, and the accurate value is obtained by weighted integration of the spectral transmittance. The result is that the quality of the sunglasses products depends on whether the lens material can block ultraviolet rays, UVA and UVB, and can It allows more visible light to pass through to achieve anti-glare function. The above experiments prove that the transmission performance of resin lenses is good, followed by glass lenses, and crystal lenses are inferior. The transmission performance of CR-39 lenses among resin lenses is far better than PMMA.
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