To determine what laser safety window to buy, the following is needed:
1) Wavelength of the laser
2) Find out what protection level is needed premised on your laser's output. Do this by looking for the recommended Optical Density (OD), asking your Laser Safety Officer, or feel free to give us a call at 1-888-752-7370 and we can assist. The needed OD is ultimately a function of both the laser being used, and what the laser needs to be reduced to or what is known as the Maximum Permissible Exposure ("MPE") based on several parameters mentioned here.
Below we've illustrated what the laser safety lens fundamentally needs to accomplish for proper laser safety:
Optical Density: Refers to the amount of light attenuated[i] by a lens and ultimately let through to hit the eye. Different lasers (and corresponding wavelengths) have different impact on the human eye (the ANSI has created standards and published them based on research). If you are having trouble knowing the appropriate optical density needed for your glasses or laser safety protection, please give us all call at 1-888-752-7370 or 952-405-6947. We have included a diagram to aide a buyer in common industry notation. Please note, some assumptions have been made (the photons depicted are not drawn to scale, and finally please be sure to reach out if there is any uncertainty).
Visibility Light Transmission (“VLT”) – Color and visibility of specific color ranges often are significantly affected by laser glasses and goggles. Think distortion when wearing sunglasses to block the sun, (often less expensive) sun glasses do an effective job of blocking the sun, however everything is much more difficult to see because not a lot of light generally is coming through. Other times with (typically more expensive) sunglasses, the sun is blocked and everything else looks very similar to how it would without the glasses. The image below is a relative comparison of visual light transmission.
|Higher VLT||Lower VLT|
Below is a table to display generalize trade-offs of different laser safety windows:
|Acrylic Class 4
|Class 4 Lasers||Yes||Yes||No|
|Typical Classification of Laser||Ultra-Violet, Visible Light, Near and Far Infrared (IR)||Infrared||Low-level Ultra-Violet, Low-Level Visible Light|
[i] Outside of the context of laser safety, optical density more commonly refers to the refractive index, and the term absorbance is used in lieu of what we are referring to here as "optical density".
[ii] Optical Density refers to a general trend, and when selecting should look at the specifications of the eyewear before purchasing
Question: If I have a window, why do I need laser safety glasses ?
Answer: We get asked if the laser is full enclosed is it fine to only have a window; laser safety standards still say no. According to laser safety standards and best practices, when working with a class 3B or class 4 laser, one should always wear appropriate laser safety eye protection. If you have questions about your particular system, please give us a call.
Question: Is twice the thickness twice the protection?
Answer: No, for most windows (and assume all of them unless you call and we say otherwise), a certain amount of dye is in each laser safety window and the specifications are the same regardless of the thickness. Different thicknesses are simply to enable the window to fit into different places. If you have any questions, be sure to reach out.
To view our selection of laser safety windows, click here.