Research On LED Photobiosafety Detection Technology

Light radiation could take physiological and physical effects on the human body,referred to as photobiological effects.According to the mechanism of photobiological effects,it includes the visual effect of light,the non-visual effect of light,and the radiation effect of light.Appropriate photobiological effects is beneficial to the human body,while excessive photobiological effects is harmful to the human body.Therefore,the safety of photobiological effects should be studied.The studies about safety of the radiation effect of light is called photobiosafety.Different types of light radiation will produce different types of photobiosafety hazards.The retinal blue light hazard generated from the 400nm-500nm band of light is the most typical.Various light sources and illuminators have potential photobiosafety issues,especially the LED.Due to the high brightness,small size,wide application and large proportion of blue light in the spectrum,the photobiosafety problem of LED has become a common concern of producers and users of light sources.In this study,a series of research and discussion on the photobiosafety detection technology of LED is provided,which provides theoretical and experimental basis for the measurement,calculation and evaluation of actual photobiosafety in LED lighting environment.The main contents and results of this study are as follows:1.The concept and mechanism of photobiological effects are summarized,and the concepts,mechanisms,effects and evaluation methods of photobiosafety are reviewed and elaborated.The main contents of the measurement standards related to the blue light hazard in photobiosafety are summarized,the evolution process of the standard system is analyzed,and the principle of the evolution of the blue light hazard measurement standard,which is that its measurement object becomes more and more practical,is pointed.The advantages and disadvantages of the radiance measurement standard method or alternative method and irradiance measurement standard method for blue light hazard measurement are compared,which indicates that the standard method of radiance measurement has the most applicability.The analysis pointed out that the "most unfavorable principle" for photobiosafety measurement leads to two problems:1.The measurement results couldn’t fully reflect the degree of damage in practical applications;2.The measurement operation becomes complicated.2.Through theoretical analysis and experimental verification,the related characteristics of blue light hazard are studied,and the radiation characteristics and spectral characteristics of the extended blue light weighted radiance LB are summarized.The radiation characteristics of LB are essentially determined by the light distribution curve of the light source,and are actually related to the measurement field of view,the measurement distance,and the measurement angle.The spectral characteristics of the light source are essentially determined by the spectrum of the light source,and the law is that the blue light hazard performance KB,v of the mixed spectrum is necessarily between the KB,v corresponding to the original spectrum.Mathematical models or empirical formulas for calculating the relationship between LB and radiation distance,LB and light distribution curve,KB,v and color temperature are proposed.According to the radiation characteristics and spectral characteristics of LB,three algorithms are proposed,including a method for expanding the conversion between blue light weighted radiance LB and intrinsic blue light weighted radiance LBS,a method for calculating the relative intensity B(φ)of LB,and a simulation algorithm for the spatial distribution LB(φ,s)of LB.To apply the LB(φ,s)simulation algorithm could simplify the measurement and calculation of blue light hazard in actual light environments.3.Based on the review and summary of the existing blue light hazard measurement system and the blue light hazard measurement requirements in the actual light environment,a portable blue light hazard measurement system design scheme is proposed.The measurement system separates the brightness with a CMOS image sensor and the spectrum with a micro spectrometer.The information acquisition,calculation and result output are completed by the host computer.With this basic design scheme,the measurement system function and performance design are completed.In the process of construction and debugging of the prototype system,the spectral response correction method,image uniformity correction method and gray-brightness conversion algorithm of brightness measurement are proposed,and the system calibration is completed based on the above methods.Through verification experiments and uncertainty analysis,it is verified that this portable blue light hazard measurement system could achieve the designed functions and performance.This design is a measurement system design that is generally applicable to photobiosafety measurement.4.Based on the research results of blue light hazard characteristics and the function of portable blue light hazard measurement system,a blue light hazard measurement method based on actual light environment is proposed.The main idea of the measurement method based on the actual light environment is to measure and evaluate the blue light hazard of the light environment in the actual use scene of the light source,the luminaire or the illumination system with "light" as the core.This measurement method emphasizes that the measurement results reflect the intensity of the blue light hazard that the human eye could receive when facing the actual light environment.This measurement method simplifies the measurement operation and its measurement results are more instructive for the protection of blue light hazard in actual environment.5.Appling the blue light hazard measurement method based on the actual light environment,the blue light hazard of LED lighting products and effectiveness of blue light hazard protection products are measured.The results show that the blue light generated by the daily illumination source or display is weak,so it doesn’t require special protection,and the blue light protection products are effective,which means they could be used when necessary.6.Sterilization with UV radiation is an important application of photobiological effects.The influencing factors and application conditions of UVC LED sterilization ability are studied,Escherichia coli cells are sterilized by UVC LED at different exposure times and exposure distances,and the sterilization rates are calculated.The experiment results indicate that the sterilization ability of UVC LED decreases exponentially with the decrease of UV dose,which is affected by UV radiation flux,exposure time and exposure distance.The empirical formula for calculating the sterilization rate of UVC LEDs is concluded.