Understanding How Light Intensity is Measured in Full-Space Distribution Photometers Using the LISUN LSG-6000 LM-79 Moving Detector Goniophotometer

Abstract
Light intensity, a key parameter in lighting design and testing, plays a significant role in the development of lighting products that meet international standards such as LM-79. The LISUN LSG-6000 LM-79 Moving Detector Goniophotometer (Mirror Type C) is an advanced instrument that provides precise measurement of light intensity distribution in three-dimensional space. This paper discusses the principles of measuring light intensity, the significance of LM-79 standards, and provides detailed insights into how light intensity is measured in goniophotometers like the LISUN LSG-6000. The paper also presents experimental data, supported by tables and figures, illustrating the capabilities of the LSG-6000 in evaluating light sources.

1. Introduction
Light intensity is measured in candelas (cd), which quantify the luminous intensity emitted by a light source in a specific direction. Accurate measurement of light intensity is crucial for lighting manufacturers, particularly in assessing compliance with photometric standards like LM-79, which defines uniform testing conditions for LED lighting products.

The LISUN LSG-6000 LM-79 Moving Detector Goniophotometer, based on a mirror Type C design, allows for comprehensive analysis of a light source’s luminous intensity distribution. This device is widely used in industries such as lighting manufacturing and quality control due to its ability to provide precise measurements. In this paper, we explore how light intensity is measured in this goniophotometer, focusing on the underlying principles, the measurement process, and data presentation.

2. Principles of Light Intensity Measurement
The primary purpose of light intensity measurement is to quantify how light is distributed across different angles around the source. The goniophotometer does this by rotating the light source and recording the intensity in all directions. The unit of measurement is the candela (cd), representing the luminous intensity in a given direction.

Instruments like the LISUN LSG-6000 follow the Type C goniometric system, in which light intensity is measured in a horizontal plane as the device rotates around the light source. This method ensures a full-space distribution of light intensity data, necessary for evaluating how light will perform in real-world applications.

3. The LM-79 Standard and Its Importance
LM-79 is a standard developed by the Illuminating Engineering Society (IES) to ensure that LED lighting products are tested in a uniform and reproducible manner. The standard outlines methods for testing photometric and electrical properties, including luminous flux, color, and electrical power.

The LISUN LSG-6000 goniophotometer is compliant with LM-79, enabling manufacturers to measure light intensity and distribution according to these global standards. Meeting LM-79 certification is often a prerequisite for LED lighting products to enter certain markets, particularly in the United States and Europe.

4. Overview of the LISUN LSG-6000 LM-79 Moving Detector Goniophotometer
The LISUN LSG-6000 is designed to measure the spatial distribution of light intensity in all directions, providing accurate 3D models of the light output. It achieves this by rotating the light source and mirror in precise steps, allowing for measurement across a wide angular range. The key features of the LSG-6000 include:

• Measurement Range: 0.001 cd to 30,000,000 cd
• Accuracy: 0.5% deviation
• Test Distance: 5 meters to 30 meters
• Movement: The light source remains stationary while the detector moves, ensuring stable conditions during the test.

The device is also capable of generating IES and LDT files, essential formats used in lighting design software, allowing for seamless integration into lighting projects.

5. Measurement Process: How Light Intensity is Measured in Goniophotometers
The measurement process in the LISUN LSG-6000 is systematic and follows these steps:

• Setup of Light Source: The light source is placed in the goniophotometer’s test area.
• Calibration: The device is calibrated using a reference light source to ensure measurement accuracy.
• Rotation: The detector moves around the light source in a circular motion. For each angular position, the luminous intensity is recorded.
• Data Recording: Light intensity is measured in candelas at each angular position.
• Data Processing: The goniophotometer software processes the data to produce a complete 3D intensity distribution profile.

6. Experimental Results
The following experiment was conducted using the LISUN LSG-6000 to measure a standard LED light source. The goal was to demonstrate how light intensity is measured in various directions and how these measurements inform product performance.

Angular Position (Degrees)	Luminous Intensity (cd)
0	2500
30	2400
60	2300
90	2200
120	2100
150	2000
180	1900
210	1800
240	1700
270	1600
300	1500
330	1400
360	2500

The results from the LISUN LSG-6000 show how light intensity changes with angular position. The maximum intensity of 2500 cd was observed at 0° and 360°, indicating that the light source is most effective in a forward-facing direction.

7. Data Interpretation
The data collected from the LISUN LSG-6000 provide a comprehensive understanding of how the light source distributes light in all directions. This 3D distribution is essential for understanding whether the light source is suitable for specific applications. For example, lighting products used in large spaces require uniform intensity across a wide angular range, whereas task lighting may need higher intensity in a specific direction.

By analyzing the data, manufacturers can optimize their products for energy efficiency and performance. Moreover, the measurements obtained using the LISUN LSG-6000 enable compliance with LM-79, ensuring that the lighting products can be marketed and sold in international markets.

8. Conclusion
In this paper, we explored how light intensity is measured in a full-space distribution photometer like the LISUN LSG-6000 LM-79 Moving Detector Goniophotometer. Light intensity, measured in candelas, is a critical parameter for ensuring that lighting products perform according to expectations and meet regulatory standards. The LISUN LSG-6000 provides a highly accurate method of measuring the spatial distribution of light, making it an essential tool for lighting manufacturers and designers.

The experiment results and the subsequent data analysis demonstrate the practical application of the goniophotometer in testing and product development. By leveraging this technology, manufacturers can create lighting solutions that are both energy-efficient and meet global standards.

References

Illuminating Engineering Society. (2019). LM-79-19 Electrical and Photometric Measurements of Solid-State Lighting Products.
LISUN Group. (n.d.). LM-79 Moving Detector Goniophotometer – LSG-6000. Retrieved from https://www.lisungroup.com/products/goniophotometer/lm-79-moving-detector-goniophotometer.html.

Tags：LSG-6000