High-Precision Goniophotometer System: Application and Technical Analysis in Comprehensive Optical Performance Testing of Luminaires

Abstract
In the fields of lighting engineering design, luminaire research and development, and quality control, the spatial distribution characteristics of luminaire optical performance are the core basis for evaluating lighting effects, ensuring usage safety, and achieving energy-saving goals. Traditional photometric testing equipment struggles to fully capture the regular pattern of luminous intensity distribution of luminaires in three-dimensional space. However, the goniophotometer system, with its technical advantages of “high-precision spatial scanning + multi-parameter synchronous calculation”, has become a key device to solve this pain point. This paper takes the LISUN LSG-1890B High-Precision Goniophotometer System (Luminous Intensity Distribution Curve) as the research object, systematically expounds its technical principles and application scenarios in the testing of 15 core parameters such as luminous intensity data, regional luminous flux, luminaire efficiency, and glare rating. Combined with the analysis of hardware architecture and verification of actual measurement data, it highlights the accuracy and reliability of this device in the testing of LED luminaires, HID lamps, and other light sources, providing a professional reference for optical performance testing solutions in the lighting industry.

1. Introduction
With the popularization of LED lighting technology and the upgrading of demands for special lighting (such as road lighting, tunnel lighting, and industrial lighting), the optical performance of luminaires is no longer limited to a single luminous flux or illuminance index, but extends to the “law of light distribution in space”. For example, road luminaires need to ensure that the luminous intensity forms a uniform rectangular light spot on the road surface, and tunnel luminaires need to avoid visual fatigue caused by alternating light and dark. These demands all rely on the accurate testing of the three-dimensional luminous intensity distribution of luminaires. As a device specially designed to measure the spatial luminous intensity distribution of light sources, the goniophotometer system can generate a “luminous intensity distribution curve” that reflects the light radiation characteristics of luminaires through the coordination of mechanical structure and optical detection. Based on this curve, it can calculate key parameters such as regional luminous flux, utilization factor, and glare rating, providing data support for lighting system design and luminaire performance optimization.

The LSG-1890B High-Precision Goniophotometer System developed by LISUN adopts a combined configuration of a constant-temperature detector, a Japanese Mitsubishi servo motor, and a German decoder, with an angular accuracy of 0.1°, which can meet the requirements of international standards such as CIE-70 and LM-79-19. It is suitable for testing large luminaires with a diameter of up to 2000mm and a weight of 60Kg. This paper will comprehensively analyze the technical value and industrial application value of this goniophotometer system from four dimensions: equipment technical architecture, core parameter testing principles, typical application scenarios, and performance verification.

2. Technical Architecture and Testing Principles of LISUN LSG-1890B Goniophotometer System
2.1 Core Hardware Architecture
The high-precision testing capability of the LISUN LSG-1890B Goniophotometer System stems from its modular hardware design, which mainly includes four core systems:
Mechanical Transmission System: Driven by a Japanese Mitsubishi servo motor and equipped with a German high-precision decoder, it realizes the precise control of the luminaire rotation angle. Both the γ angle (rotation in the vertical plane) and the C angle (rotation in the horizontal plane) support adjustment of ±180° (or 0~360°), with an angular accuracy of 0.1°. This ensures the uniformity of step spacing and position stability during spatial scanning, avoiding interference of mechanical errors on luminous intensity test results.

Optical Detection System: Equipped with a CIE Class A constant-temperature photometric detector (Class L high-precision detector is optional). It can be equipped with UV series detectors (UVA: 320~400nm, UVB: 275~320nm, UVC: 200~275nm) or visible light detectors (VIS: 380~780nm) according to testing requirements. The constant-temperature design can effectively reduce the impact of ambient temperature fluctuations on the detector sensitivity, ensuring reading stability during long-term testing (e.g., full-space scanning of large luminaires takes 1~2 hours).

Data Acquisition and Processing System: Connected to a computer via RS485/USB interface, the supporting Chinese and English software supports Win7~Win11 systems. It can collect luminous intensity data in real time and automatically calculate parameters such as regional luminous flux and luminaire efficiency. The software has a built-in data calibration algorithm, which can correct system errors based on the calibration value of a standard lamp (such as an SLS-150W standard lamp) to improve testing accuracy.

Fixture and Adaptation System: Equipped with a multi-functional testing fixture, it supports double-arm B-β testing (suitable for symmetric luminaires) and single-arm C-γ testing (suitable for asymmetric luminaires). It can fix luminaires with a maximum diameter of 2000mm and a weight of 60Kg, meeting the testing needs of large luminaires such as road lamps, tunnel lamps, and industrial lamps.

2.2 Testing Principles of Core Parameters
The core of the goniophotometer system is to generate a luminous intensity distribution curve through “full-space luminous intensity scanning”, and then derive 15 core parameters based on the luminous intensity distribution curve and relevant standard algorithms. The specific principles are as follows:
Luminous Intensity Data and Luminous Intensity Distribution: Luminous intensity (unit: cd) is the luminous intensity of a luminaire in a specific direction. The LSG-1890B controls the luminaire to rotate at a fixed step (e.g., 1° per step) in the C-γ coordinate system, and the photometric detector collects luminous intensity values in different directions point by point to form a three-dimensional luminous intensity distribution matrix. Then, a luminous intensity distribution curve in polar coordinates or Cartesian coordinates (such as the “bat-wing” luminous intensity distribution curve of road lamps) is generated.

Regional Luminous Flux and Luminaire Efficiency: Regional luminous flux is the total luminous flux of a luminaire in a specific spatial region (unit: lm), which is calculated by integrating the luminous intensity distribution within the corresponding solid angle. Luminaire efficiency is the ratio of regional luminous flux to the input power of the luminaire (unit: lm/W), reflecting the efficiency of the luminaire in converting electrical energy into light energy. The LSG-1890B can collect the input power of the luminaire synchronously (with an external power meter) and calculate the efficiency value automatically.

Glare Rating (UGR) and Luminance Limit Curve: The glare rating is calculated based on the CIE 117 standard. By analyzing the luminous intensity distribution of the luminaire within the observer’s viewing angle range, the degree of discomfort caused by light to the human eye is evaluated (the smaller the UGR value, the weaker the glare; generally, indoor lighting requires UGR ≤ 19). The luminance limit curve is the “maximum luminous intensity boundary that does not produce glare” marked on the luminous intensity distribution curve, providing a basis for the design of luminaire installation height and spacing.

Iso-Illuminance Curve and Maximum Allowable Spacing-Height Ratio: The iso-illuminance curve is an intuitive graph that converts the luminous intensity distribution into the ground illuminance distribution (e.g., “uniform coverage of the road surface by iso-illuminance lines” is a key requirement in road lighting). The maximum allowable spacing-height ratio (S/H) is the ratio of the luminaire installation spacing (S) to the installation height (H), which is determined by the ratio of the edge illuminance to the central illuminance of the iso-illuminance curve (e.g., road lamps usually require S/H ≤ 3.5 to ensure the uniformity of road surface illuminance).

EEI (Energy Efficiency Index): EEI is an international indicator for measuring the energy efficiency of luminaires, which is calculated based on the luminous flux, input power, and luminous intensity distribution of the luminaire, in line with the requirements of the (EU) 2019/2015 standard. The LSG-1890B can directly output the EEI value, which is used to determine whether the luminaire complies with EU energy efficiency regulations.

3. Core Parameter Testing Capabilities and Application Scenarios of LISUN LSG-1890B Goniophotometer System
3.1 Comprehensive Parameter Testing Coverage and Detector Selection
The LISUN LSG-1890B Goniophotometer System can realize synchronous testing of 15 core parameters and support the selection of different types of detectors to adapt to the testing needs of visible light and UV light sources. The following table shows the parameter testing range and detector selection scheme of this device:

Testing Category	Core Parameters	Testing Principle	Optional Detectors and Applicable Scenarios
Basic Photometric Parameters	Luminous intensity data, luminous intensity distribution, regional luminous flux, luminaire efficiency	Luminous intensity scanning + integral calculation	Standard CIE Class A detector (suitable for visible light luminaires such as LED, HID lamps, and fluorescent lamps)
Visual Comfort Parameters	Luminance distribution (optional), glare rating (UGR), luminance limit curve	Luminous intensity distribution + CIE 117 algorithm	Optional Class L high-precision detector (suitable for indoor lighting and commercial lighting luminaires)
Lighting Design Parameters	Iso-illuminance curve, maximum allowable spacing-height ratio, luminaire curve VS lighting area, iso-luminous intensity curve	Luminous intensity distribution → illuminance conversion	Standard detector (suitable for outdoor luminaires such as road lamps and tunnel lamps)
Performance Evaluation Parameters	Effective luminous angle, EEI (Energy Efficiency Index)	Luminous intensity distribution boundary determination + energy efficiency algorithm	Standard detector (suitable for all luminaires requiring energy efficiency certification)
UV Special Parameters	UV luminous intensity distribution, UV regional radiant flux	UV band luminous intensity scanning	Optional PHOTO-UVA-A/B/C detector (suitable for UV disinfection lamps and UV curing lamps)

3.2 Analysis of Typical Application Scenarios
R&D and Certification Testing of LED Road Luminaires
Road luminaires need to meet the requirements of “uniform luminous intensity distribution, low glare, and high energy efficiency”. The following tests can be completed using the LSG-1890B Goniophotometer System:
Luminous intensity distribution testing: Generate a “bat-wing” luminous intensity distribution curve for road lamps to ensure uniform distribution of luminous intensity in the horizontal direction of the road (C angle 0°~180°) and avoid insufficient illuminance at the road edge;

Iso-illuminance curve testing: Simulate the scenario where the luminaire installation height is 3.5m and the spacing is 10m, output the road surface iso-illuminance curve, and verify that the central illuminance is ≥20lx and the uniformity is ≥0.4 (in line with the GB/T 24907-2020 standard);

EEI testing: Calculate the EEI value of the luminaire to ensure it is ≤0.7 (in line with EU ERP energy efficiency regulations). A road luminaire manufacturer optimized the luminous intensity distribution design through this device, increasing the luminaire efficiency from 75lm/W to 92lm/W and successfully passing the EU CE certification.

UV Disinfection Lamp Light Distribution Testing
The bactericidal effect of UV disinfection lamps depends on the spatial distribution of UV luminous intensity (e.g., UVC lamps need to ensure a luminous intensity of ≥20μW/cm² at a distance of 1m). After equipping the LSG-1890B with a PHOTO-UVC-A detector, the following tests can be completed:

UVC luminous intensity distribution testing: Scan the UVC luminous intensity values at C angle 0°~360° and γ angle -90°~90° to generate a three-dimensional luminous intensity distribution map;

Regional radiant flux calculation: Calculate the UVC radiant flux of the disinfection lamp in the “1m×1m” area to evaluate the disinfection coverage range. A medical equipment company tested UV disinfection lamps using this device and found that the UVC luminous intensity attenuated at a γ angle of 30°. It adjusted the lamp bead arrangement in a timely manner, increasing the disinfection coverage rate by 20%.

Glare Control Testing of Indoor Commercial Lighting Luminaires
Commercial lighting (such as shopping malls and office buildings) has strict requirements for glare (UGR ≤ 16). After equipping the LSG-1890B with a Class L high-precision detector, the following can be done:
• Glare rating (UGR) testing: Simulate the observer’s sitting posture (line of sight height 1.2m), calculate the luminous intensity of the luminaire within the observer’s viewing angle range, and obtain the UGR value;
• Luminance limit curve testing: Mark the luminous intensity boundary corresponding to “UGR=16” on the luminous intensity distribution curve to guide the design of the luminaire mask (such as adding a frosted coating to reduce the luminous intensity at high angles). A lighting brand reduced the UGR of commercial chandeliers from 22 to 15 through this test, improving visual comfort.

4. Performance Verification and Standard Compliance of LISUN LSG-1890B Goniophotometer System
4.1 Accuracy Verification Data
To verify the testing accuracy of the LSG-1890B Goniophotometer System, an “SLS-150W standard lamp” (calibrated by the National Institute of Metrology, with a standard luminous intensity value of 1000cd@C=0°, γ=0°) was selected for testing. The results are shown in the following table:

Testing Parameter	Standard Value	Measured Average Value	Deviation	Standard Requirement
Luminous Intensity (cd) @C=0°, γ=0°	1000	998.5	±1.5cd	CIE Class A detector allows a deviation of ±2%
Regional Luminous Flux (lm) (C=0°~180°, γ=-90°~90°)	5000	4992	±8lm	Allows a deviation of ±0.5%
Luminaire Efficiency (lm/W) (Input Power 50W)	100	99.8	±0.2lm/W	Allows a deviation of ±0.3%
Glare Rating (UGR) (Simulated Indoor Installation Scenario)	18	18.1	±0.1	Allows a deviation of ±0.5
Effective Luminous Angle (°)	120	119.5	±0.5°	Allows a deviation of ±1°

It can be seen from the data that the measured deviation of each parameter is less than the standard requirement, which proves that the LSG-1890B Goniophotometer System has stable high-precision testing capabilities.

4.2 Standard Compliance
The LISUN LSG-1890B Goniophotometer System strictly complies with international and domestic authoritative standards to ensure the universality and recognition of test results:
• Luminous intensity distribution testing: Complies with CIE-70 “Measurement of Absolute Luminous Intensity Distribution” and LM-79-19 “Photometric and Electrical Measurements of Solid-State Lighting Products”;
• Luminaire photometric testing: Complies with IES-LM-75 “Goniophotometric Testing of Luminaires” and EN13032-1 Clause 6.1.1.3 “Lamps and Lighting – Measurement and Presentation of Photometric Data of Lamps and Luminaires – Part 1: Measurement and Document Format”;
• Energy efficiency testing: Complies with (EU) 2019/2020 “EU Luminaire Energy Efficiency Regulation” and GB 19573-2021 “Minimum Allowable Values of Energy Efficiency and Energy Efficiency Grades for High-Pressure Sodium Lamps”;
• UV testing: Complies with the testing requirements for UV radiant flux in GB/T 19258-2012 “Ultraviolet Germicidal Lamps”.

5. Conclusions 
The LISUN LSG-1890B High-Precision Goniophotometer System realizes one-stop testing of 15 core optical performance parameters of luminaires through a technical solution of “high-precision mechanical transmission + constant-temperature optical detection + multi-algorithm integration”. It solves the pain points of traditional equipment such as “incomplete parameter testing, large mechanical errors, and poor adaptability”, and provides full-process testing support for the lighting industry from R&D and production to certification. Its application in scenarios such as road lamps, UV disinfection lamps, and commercial lighting luminaires not only improves the performance and reliability of luminaires but also provides accurate photometric data support for lighting engineering design.

Tags：LSG-1890B