What does "NM" mean on laser safety glasses?

When you take a closer look at laser safety glasses, you’ll notice markings on the lenses such as “180–540 nm” or “OD 7+ @ 1064 nm.” But what does “nm” actually mean? And why is it so important when choosing the right laser safety glasses? In this article, we’ll explain what “nm” means, its importance in laser protection, and how to choose laser safety glasses based on wavelength specifications.

What does “nm” mean?

“nm” is short for nanometer, a unit of measurement used to describe the wavelength of light or electromagnetic radiation.

● 1 nanometer = one billionth of a meter (10⁻⁹ meters)

● Lasers are often measured in nanometers because most laser wavelengths are in the ultraviolet (UV), visible, and infrared (IR) light spectrums.

Why is “nm” important for laser safety glasses?

Laser safety glasses are designed to block specific wavelengths of laser light, not just any bright light. The “nm” value on the lens or packaging indicates the wavelength the glasses are designed to protect against. Glasses with "OD 7+ @ 1064 nm" on the lenses of laser safety glasses mean they provide protection at optical density 7 or higher at the 1064 nm wavelength, which is typically used for Nd:YAG lasers or for 1064nm fiber lasers.

What is OD (optical density)? How does it relate to nanometers (nm)?

OD (optical density) measures how effectively a lens blocks laser light of a specific nanometer wavelength.

The higher the OD value, the more light is blocked. For example:

● OD 4 blocks 99.99% of lasers

● OD 6 blocks 99.9999% of lasers

When choosing laser safety glasses, be sure to match:

● Laser wavelength (in nanometers)

● OD protection level at the same wavelength

How to read the markings on laser glasses

Laser safety glasses usually have markings like:

200 - 450nm OD 4+

630 - 660nm OD 4+

800 - 1100nm OD 6+

This means:

● The glasses provide OD4+ protection from 200 to 450 nanometers

● Provide OD4+ protection from 630 to 660 nanometers

● Provide OD6+ protection from 800 to 1100 nanometers

This applies to devices that emit lasers in the UV, blue laser, red laser, and near-infrared bands.

How to choose the right laser safety glasses

① Confirm the laser wavelength: Different laser devices have different working wavelengths, and you must choose laser glasses that match the working wavelength used. For example: If the working wavelength of the laser device is 694nm, you can choose our LP-RHP, LP-RHP-2 laser safety glasses from LaserPair. If the working wavelength of the laser device is 1064nm, you can choose our LP-YHP-2 laser glasses.

② Check the OD value: The optical density (OD value) indicates the degree of attenuation of the laser glasses to the laser. The higher the OD value, the stronger the attenuation of the laser and the better the protection level. You must choose a sufficient protection level according to the laser power and ensure that the glasses provide sufficient optical density (OD) within a specific nanometer range

③ Comply with national or international safety certifications: such as ANSI Z136, EN 207 standards;

Conclusion

The "nm" on laser safety glasses stands for nanometers, indicating the wavelength of laser radiation that the glasses are designed to block. Knowing this value is crucial for eye safety, especially when using medical, industrial or cosmetic laser equipment.