Photobiological Safety Research Articles

Human-friendly semitransparent organic solar cells achieving high performance

We systematically evaluated the photobiological safety of mainstream ST-PV devices and fabricated a series of high-performance human-friendly ST-PV devices with LUE values exceeding 5.0% and low skin/eye damage levels for human beings.

Application of Performance Test Method in Korea for LED Optical Medical Device Samples

This study obtained key performance items related to phototherapy and the standards of light-emitting diode (LED) phototherapy devices through the published literature to secure LED phototherapy device safety in South Korea. Based on these items and IEC 62471-1 for the photobiological safety of lamps and lamp systems, a performance test method and wavelength parameters, which are the main performance indicators of the LED phototherapy device, were derived. We conducted a performance test derived from this study using samples with the same performance as the sample that is being developed. The samples comprised a laser and IR LED, red LED, and blue LED. All samples were within ±5%, of the standard threshold. The 455 nm blue LED and 625 nm red LED were close to the set value with a difference of 1 to 2 nm; their wavelengths’ accuracy was within ±0.32%, ±0%, and ±0.219%, depending on the samples’ wavelengths, which was the same or similar to the error range of ±0%. As for laser and IR LED, the difference from the set value was as large as 2 to 7 nm, and their error ranges were close to ±1%, as shown by ±0.615%, ±0.828%, or ±0.591%, which were larger than the values for red and blue LEDs.

Consideration of blue light hazard for virtual reality head mounted displays

Virtual reality (VR) introduces new approaches to creating virtual spaces for empirical studies and design processes. At the same time, VR platforms for research and education purposes in the field of daylight, such as one being built at TU Berlin, have to consider technical limitations. Besides the imperfections caused by simulation tools, VR head mounted displays (VR HMDs) bring additional shortcomings, one of the most obvious being the low maximum luminance compared to daylight. However, considering a typical viewing distance within VR HMDs is about 15 mm, and a usage duration can last up to 8 hours or more, concerns have arisen about the safety of displays with high luminance levels, particularly as a prototype claiming a maximum luminance of up to 6 000 cd/m2 has been introduced in the last years. Therefore, this paper compares the blue light hazard (BLH)-weighted radiances of VR HMDs to given exposure limits provided by the ICNIRP guidelines on limits of exposure to incoherent visible and infrared radiation and by the IEC 62471 (photobiological safety of lamps and lamp systems). The paper concludes with a statement on the BLH safety of VR HMDs.

Spectral Mismatch Effect of Ultraviolet Radiometers in Actual UV-C Measurement.

The management of radiant exposure to ultraviolet (UV) radiation, especially in the wavelength range from 100 nm to 280 nm (i.e. UV-C), is important for virus inactivation or photobiological safety. Recently, many commercial UV radiometers have been used to measure UV-C irradiance for industrial and public applications. The accuracy of the four types of commercial UV radiometers was investigated by comparing the reference irradiance values obtained from the spectral irradiance standard. It was found that the displayed values of the UV radiometers have discrepancies, such that the measured value can be more than twice the actual value in a certain case. The spectral mismatch between the calibration and test sources is a major factor in the discrepancies in the UV-C measurements. With spectral mismatch correction, most corrected values show a tendency to improve the result to approaching the reference values within 20%. Users need to provide spectral information about the source and radiometer used for UV-C measurement.

9.1: Invited Paper: Pupil Size Estimation Model Based on Revised Spatially Weighted Corneal Flux Density and Chromaticity Coordinates

As an important parameter in studies on vision and ophthalmology, pupil size directly controls the amount of the light entering the human eye. Pupilometers or eye tracking systems are used to measure the pupil size in some studies while a pupil size estimation model can be applied when actual measurement is not available, such as in cases of optical design, photobiological safety studies, etc. There are several existing pupil size estimation models, most of which reveal the relationship between pupil size and spatial distribution of luminance. However, the radial asymmetry of spatial luminance weighting function in horizontal and vertical directions and the effect of light chromaticity on the human eye were investigated. In this paper, experiments were conducted to reveal the asymmetry of the spatial weighting function in the horizontal and vertical directions and the effect of chromaticity on the pupil size. A unified pupil size estimation model is proposed based on spatially weighted corneal flux density and chromaticity coordinates.

Wide color gamut, low non-visual effect, and their stabilities related to luminous properties in four-primary-color display

The circadian effect and photobiological safety of the display should be concerned, as well as the color gamut. By adding another primary color to the traditional blue-green-red (RGB) direct emission display, a four-primary-color display was proposed. The display presents wide color gamut and high stability with variation of primary colors. The optimal color gamut coverage (CGC) in Rec. 2020 standard reaches 98.2 %, and it also maintains above 96.5 % with 20 nm variation of peak wavelengths and full widths at half maximum (FWHMs). At D65 white point, the melanopic efficacy of luminous radiation (MELR) of four-primary-color display decreases to 0.60, which is 29.4 % and 43.9 % less than liquid crystal display (LCD) and organic light-emitting diode (OLED) display, respectively. Presenting ten reference colors, the MELRs of four-primary-color display are also less than other displays in most cases. In addition, the blue light hazard efficiency of radiation (BLHER) of four-primary-color display is slightly less than other displays. At last, the further improvement for the four-primary-color display was discussed.

Utilization of far-red LED to minimize blue light hazard for dynamic semiconductor lighting

ABSTRACT The blue light hazard (BLH) and luminous efficacy of a source () are associated with the photobiological safety and energy saving of light-emitting diodes (LEDs), respectively. In this study, we used genetic algorithm (GA) to optimize the BLH, , and color rendering parameters of five-chip hybrid white LEDs. Based on the optimal results, we used five-chip LEDs to obtain the hybrid white light. Their peak wavelengths were 461.5 (blue), 523.9 (green), 588.2 (orange), 643.3 (red), and 694.2 nm (far-red), respectively. In practice, the blue light hazard efficiency of radiation (BLHER) of the hybrid white light was less than 0.10, which was lower than half of the most common light sources. The ranged from 51.6 to 115.6 lm/W at correlated color temperature (CCT) from 2700 to 6500 K. On average, the CIE general color rendering index (Ra), CIE special color rendering index for the ninth deep red test sample (R9), ANSI/IES TM-30 color fidelity index (Rf), and color gamut index (Rg) of hybrid white light were 91.3, 87.8, 83.3, and 96.7, respectively. The melanopic efficacy of luminous radiation () was tunable in the range of 0.60 to 1.35 mW/lm. These results demonstrated that we used far-red LEDs to fabricate white light with low BLH and relatively high efficiency.

The current state of energy efficiency and light quality of led products

The article presents the results of the energy efficiency study and light quality of LED illuminators (lamps) for general lighting, in particular colorimetric parameters, light flux modulation and photobiological safety. It is shown that two-base LED lamps with G13 base and luminaires for outdoor lighting have achieved energy efficiency class A++. LED lamps with E27 base and indoor lighting fixtures with light diffusers have a light output 25–35% lower and correspond to energy efficiency classes A+, A, B. Correlated color temperature (FTA) of indoor lighting fixtures is mainly in the range of 3000–4500 K, and the total color rendering index Ra – in the range of 71–86 units. The deviation of chromaticity from nominal values can reach 7+ degrees of McAdam ellipses (7+ standard deviations of SDCM comparison color). The angular non-uniformity of color in luminaires with diffuse light diffusers does not exceed 3 SDCM, and for luminaires without light diffusers and with lens optics - can exceed 7+ SDCM.
 It is shown that LED luminaires for indoor lighting have a mainly safe level of flicker and visibility of the stroboscopic effect. In the frequency range up to 80 Hz, the flicker level, which is observed with a probability of 50% lower than incandescent lamps with a power of 60 watts. In the frequency range up to 3000 Hz, the modulation depth corresponds to a level that does not create adverse biological effects.
 LED lamps and illuminators for general lighting entering the lighting market do not exceed the parameters of the insignificant risk danger group of blue light RG1. Lamps and illuminators using diffuse light diffusers belong to the general group RG0 (no risk).
 Conclusions are made on energy efficiency and light quality of LED lamps.

A Study on the Photobiological Safety of LED Masks

LED masks have made a significant impact on the beauty care sector. These products use low level light therapy to treat damaged skin and encourage skin regeneration. However, there are no specific safety standards for LED masks. Therefore, consumers may incur risks, such as skin damage and eye burns. In this study, selected LED masks were investigated based on their number of LED modules and wavelength bands (blue, yellow, and red light). The irradiance and radiance were measured according to the measurement criteria of IEC62471, which is an international standard for photobiological safety. This standard was used to derive the results and to find the corresponding hazards to humans. The products use blue light, and the inclusion of a separate eye protection device was checked. The application of an automatic output blocking system was checked when the product is used for a particular period. This study aims to present a domestic photobiological safety standard management plan and guidelines for the use of LED masks according to the test results.

Investigation of photobiological safety of blue light of LED image projector of household use

Abstract
 Light emitted in the wavelength range of 400–500 nm causes a very significant photochemical effect on the retina. At certain doses of blue light energy can cause damage to the retina, so the study of the safety of blue light projectors used in domestic conditions is an urgent task. The aim of this work is to study the photobiological safety of light image projectors with light emitting diodes. The paper analyzes the requirements for photobiological safety of tube systems and methods for assessing the danger of blue light of projectors that use LED light sources. The information is provided on the equipment for measurement of spectroradiometric and photometric parameters of beams of projectors, as well as features of radiance and irradiance measurement of lamp systems in which lens optics is used.
 The results of research of photobiological danger levels of blue light of image projectors intended for use in household conditions are presented. It is shown that at a distance of 1 m from the projector (the distance for which the level of photobiological safety of blue light is normalized), the investigated type of projector belongs to the risk group RG1 (insignificant risk). When the distance is reduced to 0.5 m and 0.2 m, the risk of blue light increases to the RG2 group (medium risk).
 The features of the requirements for photobiological safety of blue light of image projectors used in everyday life, educational institutions and in other conditions are analyzed. In particular, the risk group at a distance of 1 m from the collimator lens should not exceed RG1, and it is recommended to put an additional label on the projector indicating the risk group RG1 and mark this information in the user manual.
 Conclusions are made on the compliance of the studied low-power image projectors with the safety conditions of blue light, established by the international standard IEC 62471-5 (Photobiological Safety of Lamps and Lamp Systems – Part 5 Image Projectors).

Image Acquisition Device for Smart-City Access Control Applications Based on Iris Recognition.

In this work, we present an eye-image acquisition device that can be used as an image acquisition front-end application in compact, low-cost, and easy-to-integrate products for smart-city access control applications, based on iris recognition. We present the advantages and disadvantages of iris recognition compared to fingerprint- or face recognition. We also present the main drawbacks of the existing commercial solutions and propose a concept device design for door-mounted access control systems based on iris recognition technology. Our eye-image acquisition device was built around a low-cost camera module. An integrated infrared distance measurement was used for active image focusing. FPGA image processing was used for raw-RGB to grayscale demosaicing and passive image focusing. The integrated visible light illumination meets the IEC62471 photobiological safety standard. According to our results, we present the operation of the distance-measurement subsystem, the operation of the image-focusing subsystem, examples of acquired images of an artificial toy eye under different illumination conditions, and the calculation of illumination exposure hazards. We managed to acquire a sharp image of an artificial toy eye sized 22 mm in diameter from an approximate distance of 10 cm, with 400 pixels over the iris diameter, an average acquisition time of 1 s, and illumination below hazardous exposure levels.

Optimization of the dynamic light source considering human age effect on visual and non-visual performances

The spectral transmittance of ocular media on the short-wavelength light is higher for young observers than elders. It is essential to concentrate on the photobiological safety of children and circadian effect of elders when designing the light sources. In this study, we optimized the peak wavelengths and ratios of four-channel light emitting-diodes (LEDs), to fabricate the dynamic white light which performed well on photobiological safety, circadian effect, and color rendition for observers of different ages. Based on the optimal results, we selected the four monochromatic LEDs of 461.0, 525.0, 589.0, and 660.0 nm, and then fabricated the practical white light. The correlated color temperature (CCT) of the dynamic white light is tunable from 2700 to 6500 K. For 1-year-old observers, the blue light hazard efficiency of radiation (BLHER) is less than 0.237. For 70-year-old observers, the melanopic efficacy of luminous radiation (MELR) reaches 0.987 mW/lm and its tunability is optimized to be 2.10. The general color rendering index (Ra), special color rendering index (R9), color fidelity index (Rf), and color gamut index (Rg) are more than 89.3, 79.1,81.7, and 93.6, respectively. At last, we also discussed the impacts of the peak wavelength variation on the performances of hybrid white light.

Photobiological safety of lamps and lamp systems in agriculture

Purpose: The article aims to study the photobiological safety of ultraviolet radiation of UV lamps in agriculture. Design/methodology/approach: The research and analysis of the lighting characteristics of samples of LUF 80 and LE 30 lamps, which are the most widely used in the agrarian complex. Findings: Experimental studies have shown that the photobiological safety of LUF 80 lamps belongs to the low-risk group RG1, while LE 30 lamps show high risk and are thus assigned to group RG3. Research limitations/implications: It is advisable to continue studying the characteristics of lamps and lamp systems for various fields of agriculture on the market in Ukraine to assess their compliance with safety requirements. Practical implications: The application of the proposed approach allows increasing the level of labor safety in commercial greenhouses or any other industry by choosing the suitable lamps for agriculture that at present are not regulated by additional safety measures. Originality/value: The originality of the article is showing the results of the experimental data of the studies of light-technical characteristics of ultraviolet lamps for agriculture.

Spatially-Resolved Multiply-Excited Autofluorescence and Diffuse Reflectance Spectroscopy: SpectroLive Medical Device for Skin In Vivo Optical Biopsy

This contribution presents the development of an optical spectroscopy device, called SpectroLive, that allows spatially-resolved multiply-excited autofluorescence and diffuse reflectance measurements. Besides describing the device, this study aims at presenting the metrological and safety regulation validations performed towards its aimed application to skin carcinoma in vivo diagnosis. This device is made of six light sources and four spectrometers for detection of the back-scattered intensity spectra collected through an optical probe (made of several optical fibers) featuring four source-to-detector separations (from 400 to 1000 µm). In order to be allowed by the French authorities to be evaluated in clinics, the SpectroLive device was successfully checked for electromagnetic compatibility and electrical and photobiological safety. In order to process spectra, spectral correction and metrological calibration were implemented in the post-processing software. Finally, we characterized the device’s sensitivity to autofluorescence detection: excitation light irradiance at the optical probe tip in contact with skin surface ranges from 2 to 11 W/m², depending on the light source. Such irradiances combined to sensitive detectors allow the device to acquire a full spectroscopic sequence within 6 s which is a short enough duration to be compatible with optical-guided surgery. All these results about sensitivity and safety make the SpectroLive device mature enough to be evaluated through a clinical trial that aims at evaluating its diagnostic accuracy for skin carcinoma diagnosis.

Blue-Light Hazard of Light-Emitting Diodes Assessed with Gaussian Functions.

The high blue proportion of phosphor-conversion white-light emitting diodes (pc-LEDs), especially of those with higher correlated color temperatures (CCT), raises concern about photochemically induced retinal damages. Although almost all general lighting service LEDs are safe, other applications exist, like spotlights for theatres or at construction sites, that can pose a severe blue-light hazard (BLH) risk, and their photobiological safety must be assessed. Because of required but challenging radiance measurements, a calculative approach can be supportive for risk assessment. It is the aim of this work to exploit Gaussian functions to study LED parameter variations affecting BLH exposure. Gaussian curve approximations for color LEDs, the BLH action spectrum, and the spectral luminous efficiency for photopic vision enabled analytically solving the BLH efficiency, , and the BLH efficacy of luminous radiation, . It was found that sigmoidal functions describe the CCT dependence of and for different color LEDs with equal spectral bandwidth. Regarding pc-LEDs, variations of peak wavelengths, intensities, and bandwidths led to linear or parabolic shaped chromaticity coordinate correlations. and showed pronounced CCT dependent extrema that might be exploited to reduce BLH. Finally, an experimental test of the presented Gaussian approach yielded its successful applicability for color and pc-LEDs but a minor accuracy for blue and green LEDs.

Research of the photobiological safety of led lamps and luminaires for general lighting

The paper analyzes the methods of assessing the photobiological safety of LED light sources according to international standards. It provides information on test equipment for determining the spectral composition of radiation and photometric parameters on the basis of which LED products are classified by risk groups of blue light. LED lamps and luminaires for general lighting in various spheres including household, public and office premises, outdoor lighting, etc. are studied. The level of danger of blue light is assessed at a distance at which the illuminance of 500 lux is formed, as well as at a distance of 200 mm (the most unfavorable conditions) according to the recommendations of international standards IEC 62471, IEC/TR 62471-2 and IEC/TR 62778. The results of the study of certain industrial samples of LED lamps and luminaires available on the Ukrainian market are presented.It is shown that the vast majority of LED products for general lighting have photometric parameters that do not exceed the group of insignificant risk RG1. All studied lamps in which low-power LEDs and bulbs with light scattering coating are used belong to the general group RG0 (no risk). Luminaires with low-power and medium-power LEDs, that have diffuse light diffusers, also correspond to the risk group RG0. Only luminaires with bright small-sized LEDs that don’t have the light diffusers (angular size less than 11 mrad) exceed the limits of the RG1 low-risk group. The number of such lamps does not exceed 10% of the studied products. At a distance at which an illumination of 500 lux is formed, the danger of blue light does not exceed the RG1 group. When the photobiological safety of blue light was measured from a distance of 200 mm, part of the luminaires with RG0 were moved to the group RG1, and luminaires from the group RG1 were moved to the group RG2. For luminaires belonging to the group RG2, the limit distances at which the luminaires still belong to the group RG1 were calculated.It was noted that a set of test equipment for determining the spectral composition of radiation and photometric parameters, as well as the software used to process the measurement results, significantly increases the productivity of assessing the photobiological safety of LED products. It was proposed that regulatory documents and catalogs for LED lamps and luminaires should declare the maximum luminance of these lamps.

INCREASING THE LEVEL OF PHOTO BIOLOGICAL SAFETY OF THE EMISSION SPECTRUM OF AN LED LIGHT SOURCE

The subject of research is the emission spectra of light sources based on LED structures. The purpose of the work is to formulate proposals to improve the photo biological safety of LED lighting systems. The article solves the following tasks: analyzing the situation in the field of photo biological safety of light sources based on LED structures, proposing a concept for improving it in sources based on LED modules with a two-component phosphor. Methods such as comparative analysis, spectrometric method are used. The following results were obtained. A brief analysis of the factors affecting the photo biological safety of artificial light sources based on LED modules and a review of modern technological developments aimed at improving it is carried out. Since the implementation of these developments has a limited volume in the structure of the production of LED modules and a high cost, the concept of increasing the photo biological safety of light sources using cheap white light modules with a two-component phosphor and additional color modules to fill the gap in the spectral characteristic of white light has been proposed. A simple criterion is proposed for calculating the required ratio of white and color modules based on their spectral characteristics to activate the natural mechanism of eye protection due to pupil constriction. The work investigated color modules at wavelengths 480 nm, 492 nm and 503 nm. It has been shown that color modules with a shorter peak wavelength are needed less in relation to the number of whites to create a safe emission spectrum. The paper also estimated the fraction of the emission power with a wavelength of less than 450 nm in the emission spectra of the three investigated variants of combinations of white and color modules and four SunLike modules with different color temperatures. The share of the blue part of the spectrum in the emission power distribution of SunLike LED modules turned out to be higher than in traditional modules with a two-component phosphor at similar color temperatures. Conclusions. The proposed method increases the photo biological safety of the spectrum of LED light sources to the level of natural illumination due to adequate regulation of the pupil diameter and does not increase the total fraction of the emission power in the region λ ≤ 450 nm, which is dangerous for vision. This fraction is even less than in SunLike modules at close values of color temperature, since their emission spectrum is expanded to the region of shorter wavelengths and starts from λ ≈ 370 nm). Considering that the CVC characteristics of color and white LEDs are close, but not identical, their series connection leads to a redistribution of the emission power. In addition, LEDs from different manufacturers differ in energy efficiency and electrical parameters, therefore calculations in practice need to be adjusted in each specific case.

DIRECTIONS FOR IMPROVEMENT OF STANDARDS ON LED TECHNIQUE AND LIGHTING WITH ITS USE

One of the main tasks of high-quality lighting is to provide comfortable visual work and adequate perception of illuminated objects by obtaining light with a wide range of correlated color temperatures with high color rendering quality. The paper analyzes the shortcomings of national regulatory documents on establishing tolerances for the color of lamps and fixtures using LEDs and evaluating their quality in color reproduction. Instead of using Mac Adam ellipses on the SIE 1931 (x, y) color chart for establishing the color requirements it is recommended to use circles on the 1976 SIE (u ', v'), and evaluate the color rendering quality using the CRI method, additionally apply the CQS and TM 30-18 methods. Due to the fact that the spatial color of LED luminaires can be inhomogeneous, it is recommended to indicate both the average color and color in a certain direction, as well as an indicator of the color heterogeneity. The necessity of developing standards for protection against unwanted non-visual biological effects, as well as other negative effects of artificial light, in particular, excessive brightness, pulsation of the light flux, photobiological hazards, etc., is substantiated. Considering the importance of the influence of light pulsation on the quality of lighting, before the development of CIE or IEC standards, it is recommended that national standards for LED lamps and luminaires include the requirements for description of pulsation parameters and measurement methods in accordance with the recommendations of IEEE 1789-2015 standard, which is the most advanced today. For the design of ergonomic lighting, it is proposed to provide information on lamps and luminaires related to their maximum brightness. When developing new criteria for lighting, taking into account the visual impact, it is already possible to use the knowledge accumulated by this time, in particular, for creation of biologically active and biologically dimmed light by changing the spectral composition of radiation and illumination. Proposals related to the limits of the correlated colour temperature, brightness, level of pulsation for lighting of children and educational institutions, residential premises and the like are also considered. Recommendations on the development of new national standards of Ukraine harmonized with international ones are also provided. Keywords: сolor rendering index, percent flicker, correlated colour temperature, illumination, photobiological safety

Development and Effect Analysis of UVB-LED General Lighting to Support Vitamin D Synthesis

Ultraviolet rays from sunlight are involved in vitamin D synthesis, which is essential in maintaining health. Most in vivo vitamin D synthesis occurs via exposure to sunlight, whereas a small portion is obtained through diet. Therefore, appropriate exposure to sunlight is recommended to satisfy vitamin D requirement. However, vitamin D deficiency still poses a serious issue to numerous people. To resolve this problem, artificial lighting has been studied to provide rays of UV light with characteristics similar to that of sunlight. The present study introduced vitamin D synthesis stimulating UVB-LED light via the general diffusion lighting type to indoor dwellers. However, despite the strides of advancement made in this type of lighting, studies on UVB with relation to vitamin D synthesis are limited. This study aimed to suggest UVB-LED lighting for indoor dwellers and confirm the effectiveness of vitamin D stimulation through animal testing. For this, a UVB-LED providing safe UVB dosage was developed based on the photobiological safety (IEC 62471) of lighting. Next, a comparison study of the suggested lighting and general lighting was executed in an isolated system. The study continued for two weeks and the vitamin D levels within the animal test subject (Rat, Wistar, male) were measured. At this time, the lighting was turned on for 06:00~22:00 considering the sunrise timing and average lighting time for modern people, and blood was collected from the caudal veins of the rats and analyzed for the amount of 25-hydroxyvitamin D [25(OH)D]. Analysis results showed that the amount of 25-hydroxyvitamin D [25(OH)D] in blood was higher, on average, by 6.8% (0.97 ng/mL) and 7.3% (0.9 ng/ml) in rats reared under UVB-LED lighting on the seventh and fourteenth experimental days, respectively, than those under general lighting. It was, therefore, confirmed that vitamin D synthesis in the human body can be supported by the proposed lighting in this study.

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.