LED blue light hazard is to evaluate the photochemical damage of the blue radiation to the retina. In practice, we may observe the light source or luminaire emitting surface in different regions from different angles. Therefore, in order to meet a variety of applications, IEC 62471 provides that the blue light hazard classification should be based on the radiation exposure values (weighted irradiance and radiance) of the maximum brightness of light-emitting surface area in the direction of maximum radiation intensity.
The evaluation and measurement standards of LED blue light hazard mainly include IEC / TR 62778, IEC62471, IEC 62471-2, GB / T 20145-2006, etc. IEC 60598-1 adopted IEC / TR 62778 “Application of IEC 62471 for the assessment of blue light hazard to light sources and luminaires “. IEC / TR 62778 is based on IEC 62471, and has been simplified.
1) Measurement of LED light source
The light source is mounted on a five-dimensional position of the control system. After confirming the maximum exposure radiation position of brightness and radiance, the system can adjust the light source and make it aligned to the measurement device, and test to obtain luminance, radiance, and spectral data of a light source, and automatically calculate the weighted radiance LB and Ethr of blue light hazard. Then classify the light blue hazard in accordance with the flow shown in FIG. 1.
Figure 1 The flow of assement for blue light hazard (Quoted from standard IEC/TR 62778)
2) Measurement of LED luminaires
If the hazard information of the light source is known, lighting manufacturers can follow the FIG. 1 to classify the lamps hazards based on the data they provide. If the light source installed in the lamp is on Ethr for RG2 category or a small light source, the system can also be used to measure the dmin, ie. minimum safe distance using.
If the information is unknown, lighting manufacturers can also use the system to measure the lamp’s brightness, radiance and spectral data, and classify the blue light hazard in accordance with IEC 62471 or IEC / TR 62778 standard requirements. And the test conditions of luminous intensity should be as far as possible consistent with the actual application conditions, including working conditions of lamps, measuring distance, measuring the angle of view etc., to carry out effective luminaires’ security classification.
Figure 2 shows the integrated test system for light source and lamps blue hazards. The system has integrated high precision imaging luminance meter and high precision spectroradiometer, which can achieve the accurate measurement of weighted radiance, luminance, hazard weighted irradiance, illuminance, spectral, KB, V, Ethr etc parameters.
Figure 2 IEC/EN62471 Blue light hazard mesurement system
The scalability of this system is very strong, and it can be flexibly configured various types of measuring instruments, to test a full set of optical parameters of biological hazards required by IEC 62471, and classify the hazards rating of tested light source or luminaires. It can meet multiple measurement requirements occasions, such as certification laboratory, a wide variety of lighting manufacturers and so on. Moreover, the system can also test by compared IEC 62471 with IEC / TR 62778 standards, to help luminaries manufacturers to identify the real hazard class depending on the actual applications.