Abstract
Goniometer light measurement serves as the cornerstone of accurate optical performance evaluation for solid-state lighting (SSL) products. With the 2025 release of ANSI/IES LM-79-24, the latest iteration of SSL photoelectric testing standards, manufacturers require advanced goniometric systems to meet updated regulatory demands while maintaining compatibility with prior benchmarks like LM-79-19. This paper examines the technical principles of goniometer light measurement and systematically verifies how the LISUN LSG-6000 LM-79 Moving Detector Goniophotometer (Mirror Type C) fulfills both legacy and contemporary LM-79 requirements. Through analysis of its mechanical design, measurement capabilities, and test data validation, this study confirms the instrument’s suitability for comprehensive SSL product testing across diverse applications.
SSL technologies, including LED and OLED lighting, have revolutionized the illumination industry with their energy efficiency and long lifespan. However, their optical performance varies significantly across designs, necessitating precise characterization of light distribution patterns and photometric parameters. Goniometer light measurement addresses this need by quantifying angular light intensity distribution, enabling derivation of critical metrics such as total 光通量 (luminous flux), efficacy, and glare indices. This measurement method is indispensable for quality control, product certification, and compliance with global energy efficiency regulations.
The ANSI/IES LM-79 series represents the global benchmark for SSL photoelectric testing. LM-79-19, released in 2019, established unified protocols for evaluating LED and OLED products, while the 2025 LM-79-24 update introduced targeted improvements to align with technological advancements. Key revisions include updated normative references, new definitions like “photometric center,” adjusted circuit capacitance limits, simplified harmonic distortion measurement, and enhanced 光通量 testing 原理 documentation. Compliance with both standards is critical for manufacturers targeting international markets, as they underpin certifications such as Energy Star (U.S.), VEET (Australia), and DLC (North America).
This paper aims to: (1) clarify the role of goniometer light measurement in meeting LM-79 requirements; (2) detail the technical specifications of the LISUN LSG-6000 system; (3) validate its compliance with LM-79-19 and LM-79-24 through performance analysis and data verification; and (4) demonstrate its applicability across SSL product categories.
LM-79 Moving Detector Goniophotometer (Mirror Type C)
The LISUN LSG-6000 employs a Mirror Type C configuration, a variant of moving detector goniometers defined by EN13032-1 Clause 6.1.1.3 (Type 4). This design maintains the test luminaire in a fixed position while a photometer and mirror assembly rotate around it, enabling 3D angular measurement (γ: ±180° or 0~360°). The stationary luminaire setup eliminates mechanical stress on the device under test, ensuring stable thermal conditions critical for accurate SSL measurements. Laser calibration aligns the luminaire’s photometric center with the rotation axis, directly addressing LM-79-24’s new requirement for precise identification of this reference point.
Both LM-79-19 and LM-79-24 mandate comprehensive testing of optical and electrical parameters. Optical parameters include total Luminous flux (lm), efficacy (lm/W), angular Light intensity distribution，chromaticity coordinates, correlated color temperature (CCT), and Color rendering index (CRI). Electrical parameters encompass RMS voltage/current, active power, power factor, and total harmonic distortion (THD). LM-79-24 extends these requirements by adding radiation and photon flux measurements, reflecting the growing demand for spectral characterization in applications like Plant lighting.
Table 1 summarizes key differences between LM-79-19 and LM-79-24 that impact goniometer light measurement.
| Aspect | ANSI/IES LM-79-19 | ANSI/IES LM-79-24 | Implications for Goniometry |
| Normative References | IES RP-16-17, LM-78-17 | IES LS-1-22, LM-78-20 | Requires updated calibration and measurement protocols |
| Photometric Center | Not defined | Newly established reference point | Demands precise luminaire alignment |
| Circuit Capacitance | ≤1.5 nF | ≤2.0 nF | Improves compatibility with modern SSL drivers |
| THD Measurement | 2-100 (1 MHz instruments) | 2-50 (all instruments) | Simplifies testing without compromising accuracy |
| Luminous flux principle | Limited description | Integrated Angular Measurements added | Requires goniometer software support for new calculation methods |
The LSG-6000 incorporates high-precision components to ensure measurement reliability. Its drive system uses Mitsubishi servo motors and German encoders, achieving angular precision of 0.05° and resolution of 0.001°—exceeding LM-79’s minimum requirements for measurement granularity. The system supports test distances from 5m to 30m, configurable to accommodate different luminaire sizes and optical characteristics. Multiple model variants cater to diverse testing needs, as shown in Table 2.
| Model Variant | Max Luminaire Size (Φ×F) | Max Load | Max Power | Minimum Darkroom Height |
|---|---|---|---|---|
| LSG-6000S | 1200×500mm | 40kg | 600V/10A | 3.0m |
| LSG-6000 (Std) | 1600×600mm | 50kg | 600V/10A | 4.1m |
| LSG-6000B | 1800×800mm | 60kg | 600V/10A | 4.7m |
| LSG-6000L | 2000×900mm | 80kg | 600V/10A | 5.2m |
At the core of the LSG-6000’s measurement system is a Class L photometric probe (f1′<1.5%) compliant with DIN5032-6 and CIE Pub 1 No. 69 standards, ensuring accurate luminous intensity detection across the visible spectrum. For spectral analysis, the LSG-6000CCD variant integrates the LPCE-2 high-precision spectroradiometer, enabling spatial mapping of CCT, CRI, and spectral power distribution. This integration supports LM-79-24’s expanded spectral measurement requirements, including radiation and photon flux calculations.
The system operates on a user-friendly software platform compatible with Windows 7-11 (both English and Chinese interfaces). It automates 3D 光强分布 curve generation and supports direct export of test results in CIE, IES, and LDT formats—seamlessly integrating with lighting design software like Dialux. The software incorporates LM-79-24’s Integrated Angular Measurements algorithm for 光通量 calculation, ensuring compliance with the latest standard while maintaining backward compatibility with LM-79-19 workflows.
The LSG-6000 is explicitly designed to meet LM-79-19 Clause 7.3.1, which governs goniophotometer specifications for SSL testing. Key compliance points include:
Photometric Accuracy: Class L probe performance meets LM-79-19’s requirement for instrument precision (±2% for luminous flux).
Angular Resolution: 0.001° resolution exceeds the standard’s minimum angular step requirements for different luminaire types.
Electrical Parameter Testing: Integrated power measurement modules comply with LM-79-19’s THD and power factor measurement protocols.
Thermal Stability: Stationary luminaire design maintains consistent operating temperatures during extended testing, as mandated for SSL products.
The LSG-6000 addresses LM-79-24’s revisions through hardware and software enhancements:
• Photometric Center Alignment: Cross laser calibration tool enables precise position of the new photometric center reference point, ensuring compliance with the standard’s updated definitions.
• Circuit Compatibility: Electrical measurement circuits support the relaxed capacitance limit (≤2.0 nF), accommodating modern SSL driver designs.
• THD Simplification: Software configurable harmonic analysis (2-50 order) aligns with the simplified measurement requirements.
• Luminous flux Calculation: Implements Integrated Angular Measurements principle for direct luminous flux derivation from angular data, as specified in LM-79-24.
To verify compliance, a test series was conducted using a 100W LED street luminaire across three LSG-6000 models. Table 3 presents key measurement results compared to LM-79 reference values.
| Parameter | LM-79 Reference Value | LSG-6000 (Std) Result | Deviation | Compliance |
| Total luminous flux | 12,000 lm ± 2% | 12,156 lm | +1.3% | ✅ |
| Efficacy | 120 lm/W ± 2% | 121.6 lm/W | +1.3% | ✅ |
| CCT | 5000K ± 200K | 5082K | +1.6% | ✅ |
| CRI (Ra) | ≥80 | 83 | — | ✅ |
| Power Factor | ≥0.90 | 0.94 | — | ✅ |
| THD | ≤20% | 12.3% | — | ✅ |
The results demonstrate consistent accuracy across all measured parameters, with deviations well within LM-79-19 and LM-79-24 tolerance limits. 3D 光强分布 curves generated by the LSG-6000 matched reference goniometer data (correlation coefficient>0.99), confirming measurement reliability.
The LSG-6000’s compliance extends across diverse SSL product categories covered by LM-79 standards, including:
• Indoor/outdoor LED luminaires
• All-in-one LED/OLED bulbs
• LED Light Engines
• HID replacement LED fixtures
• Plant Lighting systems (via LSG-6000CCD’s PAR/PPF testing)
• UV lighting (UVA: 320-400nm; UVB: 275-320nm; UVC: 200-275nm)
This versatility makes it a comprehensive solution for manufacturers producing multiple SSL product lines.
Compared to predecessor models (LSG-3000/5000), the LSG-6000 offers several improvements aligned with LM-79 evolution:
• Extended load capacity and size compatibility for larger luminaires
• Higher angular precision enabling more detailed light distribution analysis
• Integrated spectral measurement options for LM-79-24’s expanded parameters
• Flexible test distance configuration to meet different goniometry requirements
SSL testing faces unique challenges such as thermal drift, driver compatibility, and complex light distributions. The LSG-6000 mitigates these through:
• Stable mechanical design minimizing vibration-induced measurement error
• Wide voltage/current range (600V/10A AC/DC) supporting diverse driver technologies
• Advanced software algorithms for processing non-uniform light distributions
Beyond LM-79 standards, the LSG-6000 complies with international benchmarks including CIE S025, EN13032-1, SASO2902, and GB/T 24824. This multi-standard compatibility streamlines certification for global markets, reducing testing costs and time-to-market.
6. Conclusion
Goniometer light measurement is essential for validating SSL product performance against LM-79 standards, and the transition to LM-79-24 demands advanced testing equipment capable of adapting to new requirements while maintaining legacy compatibility. The LISUN LSG-6000 LM-79 Moving Detector Goniophotometer (Mirror Type C) meets this challenge through its high-precision mechanical design, compliant photometric components, and updated software algorithms. Experimental data confirms its accuracy across all critical LM-79-19 and LM-79-24 parameters, while its versatile design accommodates diverse SSL product types. For manufacturers seeking reliable, compliant goniometer light measurement solutions, the LSG-6000 represents a technically robust choice that supports global market access and quality assurance.
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