Do Laser Marking Glasses Require a Specific Visible Light Transmission (VLT)?

Laser marking is a delicate and intense process that poses serious risks to the human eye. Laser safety glasses are an essential protective measure for anyone operating or working near laser marking machines. But one key factor is often considered when choosing the right safety glasses: Do laser marking glasses require a specific visible light transmittance (VLT), also known as light transmittance? In this article, we explain the importance of VLT, how it affects usability, and how to balance safety, comfort, and visibility in the workplace.

What is Visible Light Transmittance (VLT)?

Visible light transmittance (VLT) refers to the percentage of visible light that passes through the lenses of laser safety glasses. It determines how light or dark your field of vision will be when wearing the glasses.

High VLT (50-80%): The lenses are lighter and more visible in dim conditions.

Low VLT (10–30%): Darker lenses, typically used with high-powered lasers or in outdoor environments.

Why Visible Light Density (VLT) is Critical for Laser Marking Eyewear

1. Safety First

Laser marking eyewear must primarily protect the eyes from specific laser wavelengths – typically in the UV, visible, or near-IR range. The optical density (OD) of the glasses determines their level of protection, while the VLT affects the amount of ambient light visible when worn.

2. Operational Visibility

If the VLT is too low, users may experience eye fatigue, poor workpiece visibility, and increased error rates. This is particularly problematic for precision marking tasks or in dimly lit environments. On the other hand, a VLT that is too high may mean insufficient filtering of the intense laser light, risking eye damage.

Ideal Balance: Protection + Visibility

Choosing laser marking eyewear requires balancing two key factors:

Laser protection: Make sure the glasses are matched to the laser wavelength (e.g. 1064nm, 532nm, 355nm) and have a suitable OD rating, typically OD5-OD8 and above for industrial applications.

Appropriate VLT: Choose a VLT that provides a clear view without compromising safety. In a well-lit environment, a lower VLT is acceptable; in a dimly lit environment, a higher VLT is usually preferred for good visibility.

How to choose the right laser marking glasses

1. Check the laser type and wavelength (e.g., fiber, CO₂, or Nd:YAG laser). If you are using a fiber laser (1064nm), you need to choose protective glasses that can protect against 1064nm fiber lasers, such as LP-YHP-2 laser safety glasses from LaserPair; if you are using a CO2 laser, you need to choose protective glasses that can protect against CO2 lasers, such as  LP-CHP laser safety glasses from LaserPair.

2. Verify the OD level: The OD value (optical density) refers to the protection of laser safety glasses against lasers. The higher the OD value, the stronger the protection. If the laser power used is higher, you need to choose an OD value that matches the power.

3. Certification standards: It is recommended to choose laser safety glasses that meet ANSI Z136, EN207 or national standard GB

4. Consider the working environment: lighting conditions determine the ideal VLT.

5. Choose suppliers with brand endorsements, such as Thorlabs, LaserPair, NoIR, etc.

Conclusion

Yes, laser marking glasses do require a specific visible light intensity (VLT), but it is not a one-size-fits-all solution. While the main purpose is to block harmful laser radiation, good visibility is also essential for accuracy and productivity. Choosing laser safety glasses with a balanced optical density and light transmittance ensures the safety and efficiency of laser marking operations.