Blue Light Blocking Lenses Measuring Device

The objective of this study is to develop a measurement system for blue light blocking lens. The main features of the system are using a light pulse modulator and filtering circuit technology to prevent ambient light interference, no any expensive optical filters are needed. Our system is composed of a transmitter circuit, a receiver circuit and a signal processing circuit. The transceiver driving circuit including the modulated LED of 10 kHz and measured the light signals from unwanted noise and unmodulated all light by a photodiode, and then converted by the transimpedance amplifer. The transmitter circuit uses Darlington drive circuit to optimize the LED operating current. The percentage error of the transmittance data is nearly 6%, compared with that of the OCEAN USB 2000 spectrometer's, so proved that this device is feasibility. This experiment has also shown that the chromaticity coordinates will be changed when using blue light lens. Based on the experiment, the brightness of the blue light blocking lenses cannot be too low which will cause color deviation problems. From the analysis result in table 4, the color deviation is nearly 17% at green blocking blue light lenses and 21% at yellow blocking blue light lenses on y coordinates. Therefore, these two blocking blue light lenses are not suitable for use as blue light blocking lenses. The color deviation of coated blue film and brown 20% blocking blue light lens have nearly 3% on x-y coordinates. But, those of 8% in 30% brown and 17% in green lenses are also not suitable for blue light blocking lens using. Thus the most suitable for blue light blocking lenses using is 20% brown blocking lens. In the future, this proposed device may be used as a powerful measurement tool on the eyeglasses test line.