A Study on Blue Light Cut-off Filter for White Light LED

Background: Now a days, high efficient LED light source are used commonly for the energy saving lighting. The portion of blue light in the white LED light is harmful to the eye. Objectives: In this study, we investigated properties of the blue light cut-off filter and then designed and manufactured a modified filter in order to block the blue wavelength region which has indicated a detrimental effect to the human eye due to the spectrum range of the white light LED. Findings: The blue light cut-off filter was designed and manufactured by the minus filter design method using two materials with differing refractive indexes. The relative spectral distribution, color rendering index, luminance and chromaticity coordinates were measured while applying the manufactured blue light cut-off filter to white light LED. The relative spectral distribution of the white light LED with the filter applied decreased by an average of 24.17% at a rejection band of 435 nm to 440 nm and by an average of 3.6% at the pass band than when the filter is not applied. Improvements/Applications: The general color rendering index of the white LED was 82.75 and when applying the filter to the white light LED, it was measured to be 81.375. When multiplied by the blue light hazard weighting function to relative spectral distribution, the blue light hazard was reduced 19.35%.