GB/T 39771.2-2021 in English

Analysis of the core content of the standard

GB/T39771.2-2021, as the second part of the LED light radiation safety series standard, focuses on standardizing the light radiation safety test method of semiconductor light emitting diodes in the wavelength range of 300nm-780nm. The standard evaluates the possible photobiological hazard risks of LED products through accurate measurement of key parameters such as irradiance and radiance.

Key Control Points of Test Environment

Detailed explanation of core test parameters

1. Application of action spectrum function

The standard specifies three types of key action spectrum functions:
- SUV(λ): UV hazard to eyes and skin (300-400nm)
- B(λ): Retinal blue light hazard (300-700nm)
- A(λ): Aphakic retinal UV hazard

2. Test field of view specification

Different hazard types correspond to specific field of view requirements:
Retinal blue light hazard test needs to distinguish between two field of view conditions: 0.011rad (small light source) and 1.4rad (extended light source)

3. Incident aperture standard

All eye-related tests must use a 7mm circular aperture (simulating the human pupil), with an allowable deviation of ≤3%

Key points for implementing the test method

Irradiance test process

1. Use a spectral radiation analyzer that meets the requirements of Appendix A
2. Ensure that the detector cosine response error is <5%
3. The test distance is strictly maintained at 200mm±1mm
4. Calculate the weighted irradiance value according to the formula

Radiance test key

• The imaging method must be used to locate the maximum radiation area
• The optical system must meet the wavelength 300-700nm transmission requirements
• The CCD array detector needs to be spectrally calibrated

Safety distance calculation method

By measuring the EB or LB values at different distances, a distance-radiation value relationship curve is established to determine the critical distance when the Class 0 limit is reached. For small light sources, the inverse square law of distance can be used to simplify the calculation:
Safety distance = test distance × √(measured value/limit)

Recommendations for standard implementation

1. Equipment selection guide

Recommended configuration:
- Double monochromator system with spectral bandwidth ≤ 5nm
- Integrating sphere radiation source with temperature control
- Standard lamp set certified by CNAS

2. Test quality control

• Use standard source for daily system verification
• Establish equipment status monitoring log
• Participate in inter-laboratory comparison

3. Common problem handling

Problem: It is difficult to determine the maximum radiation direction of multi-chip LEDs
Solution: Use two-dimensional scanning Angle photometer for spatial radiation distribution mapping