I. Overview of Laser Protective Materials and Products
Laser protective materials are functional materials specifically designed to block or attenuate hazardous laser radiation. Their protective performance is directly related to the visual safety and life health of operators. Based on different protection mechanisms, laser protective materials are mainly divided into two categories: absorbing and reflective. Absorbing protective materials incorporate specific wavelength laser absorbers into substrates (such as PC or acrylic) to convert light energy into heat or other forms of energy; reflective protective materials use optical coating technology to reflect specific wavelength lasers.
A wide variety of laser protective products are made from these materials, including: laser protective eyewear, laser protective face shields/visors, laser protective panels, laser protective screens, laser protective windows, and laser protective curtains. Among these, laser protective panels are widely used as physical barriers for laser cutting, welding, and marking equipment, as well as in laser medical procedures, military exercises, and scientific research. It is important to note that lasers of different wavelengths and powers require products with corresponding protection levels – a material that effectively protects against 1064 nm infrared laser may offer no protection against 532 nm green light. Therefore, targeted testing is particularly critical.
II. What is Optical Density (OD) Value Testing?
Optical Density (OD) is the core quantitative parameter for measuring the attenuation capability of laser protective materials for specific wavelength lasers. Its mathematical definition is:
OD = log₁₀(Incident Light Intensity / Transmitted Light Intensity)
This logarithmic scale means that for every increase of 1 in OD value, the protection capability increases tenfold:
OD 3: Transmittance = 1/1000, suitable for low‑power laser protection.
OD 6: Transmittance = 1/1,000,000, the standard configuration for industrial high‑power laser cutting equipment.
OD 7+: Used in extremely high‑power enclosed environments.
OD value testing is the process of verifying, through professional testing methods, whether the actual optical density of a protective material at its nominal protective wavelength meets the claimed value. This testing is highly wavelength‑dependent – valid data can only be obtained by measuring at the specific wavelength. According to national standard GB 30863, when a laser protector has multiple protection wavelengths, the OD value for each wavelength and/or wavelength range should be provided; if the OD value is a function of wavelength, the minimum OD value within that wavelength range should be given.
III. OD Value Testing Content and Standard Basis
OD value testing must strictly comply with international and domestic authoritative standards, mainly including:
IEC 60825‑4: Dedicated standard for laser protective barriers.
ANSI Z136.7: U.S. standard for testing and labelling.
GB 7247 series: Chinese national standards.
ISO 19818‑1: Requirements and test methods for eye and face laser protectors.
A complete OD value testing process includes the following core steps:
Sample preparation and environmental calibration: The test sample is conditioned in a constant temperature and humidity environment (23 °C ±2 °C, RH < 50%).
Laser source selection: Based on the protective wavelength, select a matching stable laser source (e.g., 1064 nm infrared, 532 nm green, or 10.6 μm CO₂ laser), and set up the optical path using an integrating sphere and high‑precision power meter.
Baseline measurement: Measure the incident power without the sample in place.
Transmittance measurement: Measure the transmitted power after placing the sample.
OD calculation: Calculate the OD value using the formula.
In addition to OD value verification, IEC 60825‑4 also requires:
Laser damage resistance testing: High‑power irradiation for ≥60 seconds to check for ablation, melting, cracking, etc.
Mechanical stability testing: Simulating shock and vibration.
Environmental adaptability testing: Extreme conditions such as high temperature (70 °C), low temperature (‑40 °C), and high humidity (95 %RH).
The measured OD value must be greater than or equal to the nominal value, and different wavelengths must be tested separately.
IV. Test Report Application Process and Timeline
The process for obtaining an OD value test report for laser protective materials generally follows these steps:
Consultation: Contact a testing body to understand the service scope and clarify testing requirements.
Application submission: Fill in the testing application form and provide product specifications or product images.
Sample preparation: Prepare representative test samples (thickness and composition consistent with the actual product) and send them to the laboratory.
Testing: The testing body arranges engineers to conduct OD value testing and supporting test items.
Report issuance: A draft report is prepared, and after client confirmation, the official report is issued.
Timeline: A standard OD value test report can typically be completed within 1 week. The exact timeline may vary depending on the number of samples, testing complexity, and light source configuration. If a non‑standard wavelength laser source is required, prior arrangement with the testing body is necessary.
V. Recommendations for Choosing a Testing Body
When selecting an OD value testing body, the following aspects should be considered:
Whether the body has testing capabilities and accreditations for standards such as IEC 60825‑4, ANSI Z136.7, and GB 7247.
Whether it has laser light sources covering common protective wavelengths (1064 nm, 532 nm, 10.6 μm, etc.) and precision testing equipment.
Whether it has extensive experience in laser protective material testing, particularly in handling the challenge of extremely weak transmitted signals (nanowatt level) at high OD values (>5).
Shenzhen Zhongwei Inspection is a professional laser product testing and certification body with over ten years of experience in the laser industry, long dedicated to laser product safety testing and laser protective material testing. The organisation has comprehensive OD value testing capabilities, providing professional services such as OD value testing and PEL value testing for laser protective materials, covering laser protective eyewear, panels, screens, windows, and other products. Its testing is conducted in accordance with international and domestic standards including IEC 60825‑4 and ANSI Z136.7, with high testing efficiency and short turnaround times. The company has served more than 2,000 customers and is highly recognised in the industry. For enterprises with laser protective material testing needs, such experienced and fully accredited professional testing bodies should be prioritised.
