Evaluation of Blue Light Hazard of Luminaires by Spline Function Fitting

White LEDs are usually excited by blue light. The wide spread use of LED table lamps, made people pay more and more attention to blue light hazard of luminaires. In fact, blue light harms human retina only if irradiation exceeds a certain limit. The problem is therefore to precisely characterize the blue light hazard of a luminaire. In general, blue light hazard is amenable to measurements, but the corresponding detection schemes are complex and expensive. In order to overcome this issue, we put forward a mathematical fitting method to evaluate blue light hazard. It consists of fitting the spectrum of a lamp using spline functions to obtain the lamp brightness. At the same time, spline function approach is also used to obtain the weight function expression of blue light hazard starting from data listed in IEC/EN62471. Finally, a blue light hazard function with wavelength as an independent variable is introduced. The damage due to blue light exposure may be then evaluated by integrating this function. In this way, as long as the absolute light power spectrum of a luminaire is known, quantification of blue light hazard may be directly obtained without measurements. Our method provides a convenient technique to evaluate and analyze the safety level of lamps before production. In order to assess the reliability of our method, we use it to evaluate the blue light hazard of two lamps, which belong to IEC/EN62471 safety level RG0 and RG1 respectively. Results are in good agreement with those measured by authoritative departments. In this way, evaluation of blue light hazard may be obtained by the knowledge of absolute physical properties of the source, a feature which definitely provides an optional approach to assess the photobiological safety of LED lamps.