Why are Some Laser Safety Glasses Dark?

JUN 18

Why are Some Laser Safety Glasses Dark?

By phillips-safety

Depending on your laser, your laser safety glasses may be practically clear or very dark. Why is this?

Why Some Laser Safety Glasses Are Darker Than Others

Laser safety glasses come in a huge variety of colors and styles. Some of our laser safety glasses have clear lenses, lightly colored lenses, dark lenses, and everything in between.

Laser Safety Glasses“Lightness” of laser safety glasses is tied directly to Visible Light Transmission, or VLT. VLT is a percent measure of how much visual light passes through the lens to reach your eye. The higher the VLT, the lighter your lenses — and the easier it is to see while wearing them.

It is obviously easier to work with clearer lenses, but you cannot use clear glasses to protect from all lasers. Some have visible beams, some cause flashes that require some lens tint, and some create intense pulses of light. But why are some laser safety glasses darker than others, and which laser safety glasses require dark lenses (with lower VLT)?

So what makes your VLT low?

  • Visible light is the spectrum of light that your eyes can detect. It contains all wavelengths roughly between 400nm and 700nm, and it encompasses all of the colors of the rainbow. 
  • If your laser operates at a wavelength outside of the visual light spectrum, you can generally get lenses that are either totally clear or nearly clear.
  • If you laser operates at a wavelength that falls within the visible light spectrum, your laser safety glasses will need to block some visible light. This means that it is impossible for the lenses to be clear, and in some cases they must be dark.
  • The broader your coverage is in the visible spectrum, and the higher the optical density, the darker your lenses are going to be.
  • If you are looking for the highest VLT possible in your laser safety glasses, look at our glass filters to see if one of them has the coverage you need. Generally speaking, glass laser safety filters have higher VLT than plastic ones.

The higher your VLT is, the easier it’s going to be for you to work. In some cases, your laser application may require a certain VLT level in your laser safety glasses in order for them to be considered safe to use, according to OSHA. You should check with your Laser Safety Officer (LSO) or your laser’s manual to see if you can find VLT minimums for your laser or application.

VLT does not matter very much in some cases, such as when you are not moving the laser during operation. In these cases, you may be able to save money by going with a filter that has lower VLT. It’s always important to consider your facility’s requirements and the safest practices you can manage when purchasing laser safety glasses; safety should never be sacrificed for VLT.

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If you have any other questions about VLT, lens darkness, or laser safety glasses, leave us a comment or give us a call! Thanks for reading, and stay safe!

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