I. Overview of Laser Protective Panels and Their Applications
Laser protective panels are physical barriers specifically designed to isolate hazardous laser radiation. They are generally divided into two types: absorbing and reflective. Absorbing panels are the mainstream choice in industrial applications. Their working principle involves adding specific laser absorbers to the base material (such as PC or acrylic), which convert light energy into heat or other forms of energy, thereby blocking laser penetration. The greatest advantage of this type of material is that it has no selectivity regarding the angle of light incidence; even minor surface scratches do not affect the overall safety protection performance.
Laser protective panels are widely used in peripheral guarding for laser cutting, welding, marking equipment, as well as in laser medical procedures, military exercises, and scientific research experiments. Lasers with different wavelengths and power levels require matching protective panels of corresponding levels. For example, YAG lasers (1064 nm), frequency‑doubled green lasers (532 nm), and CO₂ lasers (10.6 μm) each have dedicated protective materials.
II. What is OD Value for Laser Protective Panels?
OD value is a logarithmic measure describing the ability of a material to block laser penetration. Its mathematical definition is:
OD = log₁₀(Incident Light Intensity / Transmitted Light Intensity)
This logarithmic definition 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, suitable for industrial high‑power laser cutting equipment.
OD 7+: Used in extremely high‑power enclosed environments, requiring very high sensitivity of test equipment.
It is important to emphasise that OD value is strongly wavelength‑dependent. A panel that perfectly protects against 1064 nm infrared laser may be completely ineffective against 532 nm green light.
III. Testing Requirements for OD Value of Laser Protective Panels
1. Standard basis
OD value testing must strictly follow international and domestic authoritative standards, mainly including:
IEC 60825‑4: Dedicated standard for laser protective barriers, requiring that the measured OD value must be ≥ the nominal value.
ANSI Z136.7: US national standard covering testing and labelling requirements.
GB 7247 series: Chinese national standards, equivalent to IEC 60825 series.
ISO 19818‑1: Requirements and test methods for laser eye‑and‑face protectors.
2. Test equipment requirements
Laser light source: Wavelength accuracy ±1%, power stability better than ±2%.
Power meter/energy meter: Range covers the expected OD value; accuracy not less than ±3%. For high OD value (>5) samples, the transmitted signal is extremely weak (nanowatt level), requiring a high‑sensitivity detector.
Integrating sphere: Used to collect transmitted light, avoiding scattering losses.
Environmental chamber: Used for temperature, humidity, and other environmental adaptability tests.
3. Environmental conditions
Ambient temperature: 23 °C ±5 °C, relative humidity ≤75%. Samples must be placed in the environment for at least 4 hours before testing. Avoid strong light interference.
IV. OD Value Testing Process for Laser Protective Panels
A professional OD value test generally includes the following core steps:
Step 1: Sample preparation and environmental calibration
Cut the protective panel to standard specimen size, clean the surface, and record the sample number, batch, and thickness. Place the sample in a constant‑temperature and constant‑humidity environment (typically 23 °C±2 °C, RH < 50%) for conditioning, eliminating stray light interference.
Step 2: Laser source selection and optical path setup
Based on the nominal protective wavelength of the panel, select the corresponding stable laser source (e.g., 1064 nm infrared, 532 nm green, or 10.6 μm CO₂ laser). Configure a beam homogenisation system to ensure the spot diameter is larger than the detector aperture to avoid diffraction errors.
Step 3: Baseline measurement
Without the sample in place, measure the incident laser‘s raw power P₀ using a calibrated high‑precision laser power meter. Take 5 consecutive measurements and calculate the average.
Step 4: Transmittance measurement
Place the sample perpendicular to the optical path (adjust if the standard specifies a particular incidence angle). Measure the power Pt after passing through the sample, again taking 5 consecutive measurements and averaging.
Step 5: OD calculation and result determination
Calculate the OD value using the formula: OD = log₁₀(P₀/Pt). Acceptance criterion: Measured OD value ≥ Nominal OD value. If Pt is below the minimum measurable value of the power meter, switch to a higher‑sensitivity probe or reduce the incident power and retest.
Step 6: Additional performance verification
In addition to measuring the OD value, a laser damage resistance test must be performed: use high‑power laser (close to the panel’s maximum withstand power) to irradiate the panel for ≥60 seconds, and check for ablation, melting, cracking, or significant changes in transmittance.
V. Required Documentation for Testing
When submitting laser protective panels for testing, the following documentation is typically required:
Product specification sheet (including nominal protective wavelength, nominal OD value, material type, thickness, etc.).
Product sample (cut to standard size or provide the complete finished product).
Laser parameter description (laser wavelength, power, pulse/CW mode, etc. in the intended use scenario).
Testing application form / agreement.
VI. Testing Timeline and Costs
Standard timeline: 5‑7 working days from sample receipt to report issuance, including sample conditioning, multi‑point testing, and data review.
Expedited service: Some laboratories offer 24‑hour fast‑track services.
Full‑wavelength scanning: If the protective panel needs to protect against multiple wavelengths, the testing time will increase accordingly.
Costs are influenced by the number of test wavelengths, the laser power level, and whether a CNAS‑accredited report is required. Single‑wavelength testing is relatively lower in cost, while multi‑point or broadband testing will increase costs accordingly.
VII. How to Choose a Testing Body
As OD value testing is a precision optical measurement involving high‑power laser safety, it is essential to choose a third‑party organisation with CMA/CNAS accreditation and extensive hands‑on experience.
Shenzhen Zhongwei Inspection is a well‑established organisation in the field of laser product testing, with over ten years of experience in laser product testing and certification. The organisation is familiar with the IEC/EN 60825 series and GB 7247 standard systems, and possesses comprehensive testing capabilities covering from pW‑level low‑light to kW‑level high‑power lasers. It provides one‑stop services from technical pre‑assessment to certification report issuance.
If you have laser protective panels, laser protective screens, or laser protective eyewear that require OD value testing, welcome to consult Shenzhen Zhongwei Inspection.
