1. What is GB/T 7922-2023?

GB/T 7922-2023 is a recommended national standard of China, titled Measurement Methods for the Color of Lighting Sources. It was issued on May 23, 2023, and implemented on September 1, 2023, replacing the previous version GB/T 7922-2008. It is under the jurisdiction of the National Technical Committee on Color Standardization.

2. Core Information

• Positioning: A fundamental and general standard for measuring the color of lighting sources, specifying measurement methods, result processing, and reporting. It is applicable to various lighting sources such as LEDs, fluorescent lamps, and halogen lamps.

• Core Parameters: Clarifies the measurement and calculation rules for key indicators including chromaticity coordinates, color rendering index (CRI), color tolerance, and correlated color temperature (CCT), following the CIE colorimetry system.

• Application Scenarios: Used in the research and development, quality inspection, engineering design, and acceptance of lighting products to ensure the consistency and traceability of light source color parameters.

• Measurement Requirements: Includes laboratory and field measurement conditions, instrument selection, light source setup, and calculation methods for total spectral radiant flux and tristimulus values.

3. Core Uses

It provides a unified technical basis for color measurement in the lighting industry, supporting product quality control, performance comparison, and compliance assessment, and ensuring that light source color indicators meet design and application requirements.

4. What specific provisions does GB/T 7922-2023 make regarding the measurement methods for the color of lighting sources?

I. Core Measurement Methods and Instrument Requirements

(1) Classification of Measurement Methods

◦ Integrating Sphere Spectroradiometry (4π/2π Geometry): Measures total spectral radiant flux and average chromaticity, suitable for overall parameter measurement of light sources.

◦ Goniometric Spectroradiometry: Measures spatial luminous intensity and chromaticity distribution, with an angular accuracy of ≤±0.5° and step sizes following CIE requirements.

◦ Spectral Radiance Method: Measures the color uniformity of the light source surface, with ≥5 measurement points, to evaluate chromaticity coordinate uniformity.

(2) Key Instrument Parameters

◦ Spectroradiometer: Wavelength range 380–780 nm, bandwidth ≤5 nm, wavelength error ≤±1.0 nm, nonlinearity ≤1.0%, relative indication error ≤±2.0%.

◦ Integrating Sphere: Inner wall reflectance ≥90%, light source surface area ≤2% of the inner wall area for 4π method, and opening ≤1/3 of the sphere diameter for 2π method.

◦ Auxiliary Equipment: High-precision power supply (AC accuracy ≤0.2%, DC ≤0.1%), warm-up time ≥30 min, and acceptable dark current/background noise.

II. Measurement Conditions and Preparation

(1) Environment and State

◦ Environment: Temperature 25℃±5℃, humidity 45%–75%, no strong light or convection, and stable power supply.

◦ Light Source: Aged and stabilized (LED ≥30 min), with luminous flux/power fluctuation ≤2% within 15 consecutive minutes; for dimmable light sources, measurements are required at 10% and 100% output, and for multi-channel sources, measurements are required at full power of each channel and total full power.

(2) Geometry and Installation

◦ 4π Method: The light source is placed at the center of the integrating sphere; 2π Method: The light source is placed at the sphere opening to avoid occlusion.

◦ Goniometric Measurement: Follows CIE geometric conditions with an angular accuracy of ≤±0.5°.

III. Spectrum Acquisition and Data Processing

(1) Acquisition Specifications

◦ Scanning range 380–780 nm, bandwidth ≤5 nm, 3 repeated scans averaged; record voltage/current, temperature/humidity, and time.

◦ The integrating sphere requires self-absorption correction: a(λ)=y_aux,TEST(λ)/y_aux,REF(λ).

(2) Core Parameter Calculation

◦ Tristimulus values, chromaticity coordinates (xy or u'v'), correlated color temperature, color rendering index (Ra and R9–R15), color tolerance, and color gamut coverage (G_φ=S/0.1952×100%).

◦ For dimmable light sources, the chromaticity coordinate shift Δu'v' ≤0.005.

IV. Measurement Provisions for Special Scenarios

(1) Dimmable Light Sources: Mandatory measurements at 10% and 100% output; multi-channel sources require measurements at full power of each channel and total full power.

(2) Color Uniformity: ≥5 surface measurement points using a spectral radiance meter or an open integrating sphere; spatial uniformity using a goniometric spectroradiometer.

(3) Colored Light Sources: Newly added calculation of color gamut coverage to evaluate color performance capability.

V. Report Output Requirements

The report shall include light source information, measurement conditions (environment/geometry/instrument), calibration records, original spectra, calculation results (chromaticity coordinates, color temperature, color rendering index, color tolerance, color gamut coverage, etc.), and compliance conclusions.