Introduction to Photobiological Safety IEC62471

Classification of Photobiological Safety Levels

According to the international standard IEC62471, optical radiation affecting the eyes and skin covers the wavelength range of 200–3000 nm.

Based on different levels of hazard, JJR Laboratoryclassifies the photobiological radiation safety of LEDs and other non-laser products into four risk groups:

- Exempt Group (No Risk)

Under the limit conditions specified by the standard, there is no photobiological radiation hazard.

- Risk Group 1 (Low Risk)

Under normal conditions of use and normal human exposure behavior, there is no photobiological radiation hazard.

- Risk Group 2 (Moderate Risk)

Based on natural human aversion responses—such as eye avoidance of high-brightness glare or discomfort from thermal radiation—no photobiological radiation hazard will occur.

- Risk Group 3 (High Risk)

Even momentary exposure can cause radiation hazards.

Currently, for LED lighting products, the primary concern is retinal blue-light photocheMICal damage.

For LEDs not intended for general illumination, ULtraviolet (UV)and infraRED (IR)radiation hazards may also be involved.

Key Analysis of IEC/TR 62778 Blue Light Hazard Assessment

2.1 Overview of IEC/TR 62778:2014

JJR Laboratoryhas extensive experience in the safety evaluation of lighting products and a deep understanding of the application of IEC62471and IEC/TR 62778standards.

- IEC62471is a comprehensive standard covering all potential health hazards from artificial optical radiation, including UV, visible light, and IRspectra.

- Within this standard, JJR focuses particularly on retinal blue-light hazards, a spectrum that may cause potential retinal damage, mainly originating from the blue portion of visible light.

For evaluating the maximum permissible exposure time (tmax):

- The value depends on the light source and observation distance.

- For general lighting luminaires, the evaluation distance is usually set at the point where illuminance is 500 lx, but not less than 200 mm.

- Considering real-world variations in illuminance, JJR sets the test distance at 200 mmin the IEC/TR 62778 report and defines the measurement field of viewas 0.011 rad.

According to IEC62471:

- If the measured field of view is ≥ 0.011 rad, JJR uses the large source method(Section 4.3.3) to calculate tmax.

- If the field of view is < 0.011 rad, the small source method(Section 4.3.4) is used for tmax calculation.

JJR continues to provide professional and reliable support for lighting product safety assessments.

IEC/TR 62778, while specifying measurement conditions different from IEC62471, mainly addresses two key issues:

1. Transmission of photobiological safety informationfrom the light source component to higher-level lighting products using the component.

2. Recommendationson observation distance and hazard classification based on spectral calculations and optical considerations in blue-light hazard analysis.

2.2 Spectrum, Color Temperature, and Blue Light Hazard

Accurate spectral measurement is essential for calculating exposure limit values.

IEC62778:2014 Implementation Rules:

- Builds upon IEC62471, emphasizing the transfer of blue-light hazard informationfrom light sources to luminaires.

- Primarily measures light sources, but luminaires can also be measured directly.

- Redefines three safety levels:

- RG0 unlimited

- RG1 unlimited

- Ethr for RG2(threshold irradiance for RG2)

Key points:

1. Ethr for RG2applies when the blue-light hazard weighted radiance may exceed RG1 limits or when radiance cannot be measured.

2. Ethrrepresents the illuminance value at the boundary between RG1 and RG2, used to determine the minimum safe usage distance (dmin).

The installation distance of the luminaire should generally be greater than dmin.

IEC/EN62471 Standard Requirements and Testing Overview

IEC/EN62471mainly measures wide-band optical radiation and calculates results by integrating:

- Human eye and skin response time,

- Viewing angle,

- Sensitivity, and other related parameters.

Applicable Products

- UV sterilization and disinfection products

- Various light sources, modules, lamps, pulsed/strobe lighting devices, and electrical appliances

These are tested for:

- Spectral distribution,

- Spectral radiance,

- Spectral irradiance,

- Effective UV radiation ratio (mW/klm),

and for photobiological hazard classification.

Test Wavelength Range

Optical radiation in the 200–3000 nmrange is evaluated for the following parameters and hazards:

1. Irradiance(radiant flux per unit area, W·m⁻²)

2. Radiance(irradiance per unit solid angle, convertible from irradiance)

3. Skin and Eye UV Hazard

4. Near-UV Hazard for the Eye (315–400 nm)

5. Retinal Blue-Light Hazard

6. Retinal Blue-Light Hazard (Small Source)

7. Retinal Thermal Hazard

8. Retinal Thermal Hazard (for weak visual stimuli, 780–1400 nm)

9. Eye Infrared Radiation Hazard (780–3000 nm)

10. Skin Thermal Hazard (380–3000 nm)