Sunglasses Introduction to detection methods and standards
Sunglasses belong to the category of individual eye and face protectors. The technical indicators to measure its quality are mainly reflected in the top focus, antique, anti-mechanical impact. Whether to block dazzling glare and other aspects, and the following should be paid attention to in the test.
Principle of ultraviolet transmittance detection of lens
The transmission ratio measurement of the sunglasses lens cannot be treated as a simple average of the spectral transmission ratio. At each wavelength but should be based on the weight of the different wavelengths. Through the weighted integration of the spectral transmission ratio. The human eyeball is a simple optical system. And the human eye’s sensitivity to different wavelengths of light radiation must be considered first when evaluating the quality of eyeglasses.
In a word, human eyes are sensitive to green light. So the transmittance of the green light band has a great influence on the transmittance of lens. That is, the weight of the green light band is larger. On the contrary, since human eyes are insensitive to purple and red light. The transmission ratio of purple and red light has less influence on the light transmission ratio of the lens. That is, the weight of the band of purple and red light is also relatively small. The effective method to detect the anti-uv performance of the lens is to quantitatively measure and analyze the transmittance of UVA and UVB spectra.
Testing instruments and methods
The spectral transmittance of sunglasses in the ultraviolet region can be determined by means of a spectral transmittance tester. Connect the spectral transmission instrument with the serial port of the computer. Start the operation program, conduct environmental correction at 23℃±5℃ (before calibration. It must be confirmed that the measurement part does not have a lens or filter). Set the test wavelength range as 280 ~ 480 nm, and observe the ultraviolet of the lens under the condition of magnification of transmittance curve. Finally, place the test lens on the test rubber plug for the light transmittance test. (note: wipe the lens and test rubber plug clean before the test).
Problems in measurement
In the detection of sunglasses, the transmission ratio of the ultraviolet band is calculated by a simple average method and is defined as the average transmission ratio. For the same sample under test, If two definitions of QB2457 and ISO 8980-3 are adopted for measurement, the results of the transmission ratio of the ultraviolet band are completely different.
When measured in accordance with the definition of iso8980-3, its transmission ratio at the UVB band was calculated to be 60.7%. However, when measured in accordance with the definition of QB2457, the calculated transmission ratio at the UVB band is 47.1%, with a difference of 13.6% between the two results.
It can be seen that the difference of reference standards will directly lead to the difference in technical requirements, and ultimately affect the accuracy and objectivity of measurement results. This problem cannot be ignored when measuring the transmittance of eyewear products.
The transmission ratio of sunglasses products and lens materials was tested and analyzed. The accurate value was obtained by weighted integral of the spectral transmission ratio, and the good and bad results of sunglasses products were obtained. Want to see lens material above all whether block ultraviolet ray UVA and UVB, can let visible light pass through more, achieve prevent dazzle function.
It is proved by experiments that the transmission performance of resin lenses is the best. Followed by glass lenses and worst by crystal lenses. The transmission performance of CR-39 lenses in resin lenses is far better than that of PMMA.