IES LM 79 Flicker and Stroboscopic Testing of Solid State Lighting Products

The IES LM-79 standard is a critical tool in the evaluation of solid-state lighting (SSL) products, ensuring that they meet stringent performance requirements for flicker and stroboscopic effects. Flicker and stroboscopic effects are not only perceptible to human observers but can also pose safety risks, especially in environments where high contrast or rapid changes in light levels occur.

Flicker occurs when the brightness of a light source fluctuates rapidly enough that it becomes perceptible to the human eye. This phenomenon is particularly important in SSL products because they often have complex electronic circuits and power supplies that can introduce variability into the light output. Stroboscopic effects, on the other hand, occur when the frequency of the light source matches or closely approximates the frame rate of a visual system (e.g., a camera or eye). This synchronization can cause objects to appear to move in jerky motions or even disappear from view.

The IES LM-79 testing protocol is designed to quantify and qualify these effects, providing manufacturers with insights into how their SSL products perform under various conditions. By conducting this test, lighting designers, engineers, and quality assurance teams can ensure that their products are safe for use in all environments, from offices to industrial settings.

The testing process involves measuring the intensity of light emitted by the SSL product over time, typically using a photodiode or similar device. The data collected is then analyzed to determine the flicker index and the stroboscopic effect severity. The flicker index provides a quantitative measure of the perceived flicker, while the stroboscopic effect severity assesses how closely the light source frequency aligns with human visual perception.

The apparatus used for IES LM-79 testing includes specialized equipment capable of capturing light output data at high frequencies. This can include digital oscilloscopes and photodiode arrays. The specimen preparation involves ensuring that the SSL product is in its intended operating condition, which may involve powering it with a specific type of driver or under controlled environmental conditions.

The methodology for IES LM-79 testing is rigorous and involves multiple steps to ensure accuracy and reliability. First, the SSL product is placed in a controlled environment where temperature, humidity, and other variables can be precisely monitored and controlled. Next, the equipment used for measurement must be calibrated according to international standards such as ISO 15463-2018.

The testing process itself involves running the SSL product under various conditions that simulate real-world use cases. This may include varying the intensity of the light source, changing the frequency of power delivery, and observing the effects on flicker and stroboscopic phenomena. The data collected during these tests is then analyzed to determine compliance with IES LM-79 standards.

Compliance with IES LM-79 testing ensures that SSL products meet stringent quality control standards, which is crucial for maintaining safety and performance in various applications. For instance, in healthcare environments where high contrast lighting can be critical, flicker-free illumination is essential to prevent visual discomfort or potential accidents.

Scope and Methodology

The scope of IES LM-79 testing encompasses the evaluation of light output characteristics such as luminous flux, color rendering index (CRI), correlated color temperature (CCT), and other relevant parameters. However, the primary focus is on flicker and stroboscopic effects.

Flicker Index Calculation: The flicker index is calculated using the formula: F = Σ(|I(t+Δt) - I(t)| / I(t)) × 100%, where I(t) represents the instantaneous luminous flux at time t, and Δt is a small interval of time.
Stroboscopic Effect Severity: This is determined by comparing the frequency of light emission with the frame rate of human vision. If there's significant alignment between these two rates, it indicates potential stroboscopic effects.

The methodology for IES LM-79 testing involves setting up a controlled environment where the SSL product can be tested under various conditions. The equipment used includes photodiodes, oscilloscopes, and other sensors capable of capturing detailed data on light output characteristics. Calibration according to ISO 15463 is essential to ensure accurate results.

The testing process itself involves running the SSL product in a controlled environment where temperature, humidity, and other variables can be precisely monitored and recorded. The specimen preparation involves ensuring that the SSL product is in its intended operating condition, which may involve powering it with a specific type of driver or under controlled environmental conditions.

Industry Applications

Industrial Environments: In environments where machinery operates at high speeds, flicker can cause visual confusion or misinterpretation of operational signals, leading to potential safety hazards.

International Acceptance and Recognition

The IES LM-79 standard is widely recognized and accepted by various regulatory bodies around the world. It aligns with international standards such as ISO 15463, which provides a framework for the measurement of light output characteristics in SSL products.

In countries like the United States, Canada, and Europe, compliance with IES LM-79 is often a requirement for SSL product certification. This ensures that manufacturers adhere to stringent quality control standards, thereby enhancing consumer safety and satisfaction.

Application Area	Description
Cinematography	Flicker and stroboscopic effects can significantly impact the quality of film. IES LM-79 testing ensures that lighting equipment used in cinematography is free from flicker to maintain smooth and natural-looking motion.
Healthcare	In hospitals, flickering lights can cause discomfort or even exacerbate certain medical conditions. Testing SSL products for flicker helps ensure a more comfortable environment for patients and staff.
Education	Flicker-free lighting is essential in educational settings to prevent eye strain among students and teachers.

Frequently Asked Questions

What does IES LM-79 testing specifically measure?

IES LM-79 testing measures the flicker and stroboscopic effects of solid-state lighting products. It quantifies these effects using metrics like the flicker index, which indicates how perceptible the brightness fluctuations are to human observers.

Why is IES LM-79 testing important for SSL products?

Flicker and stroboscopic effects can cause visual discomfort, safety hazards in certain environments (like healthcare), and even affect the quality of images captured by cameras. Testing ensures that these effects are minimized or eliminated.

What kind of equipment is used for IES LM-79 testing?

The equipment includes photodiodes, oscilloscopes, and other sensors capable of capturing detailed data on light output characteristics. Calibration according to ISO 15463 standards ensures accurate results.

How long does the testing process take?

The duration of IES LM-79 testing can vary depending on the complexity of the SSL product and the specific conditions under which it is tested. Typically, it takes several hours to a full day.

What are the consequences of not meeting IES LM-79 standards?

Non-compliance can lead to safety hazards in critical environments like healthcare and education. It may also result in product recalls or legal issues.

Is IES LM-79 testing expensive?

While the initial setup costs for equipment can be significant, long-term savings come from ensuring compliance with international standards and avoiding potential recalls or legal issues.

Who should undergo IES LM-79 testing?

Manufacturers of solid-state lighting products that are intended for use in environments where flicker and stroboscopic effects could be a concern.

Are there any exemptions from IES LM-79 testing?

Exemptions may apply to products that are inherently stable or those where flicker and stroboscopic effects do not pose a significant risk. However, it is advisable to consult with an accredited laboratory for specific guidance.