Important Laser Safety Note
Final laser safety product selection should always be reviewed by the on-site Laser Safety Officer (LSO) or other qualified laser safety personnel based on the actual laser system, operating conditions, beam characteristics, reflections, and applicable ANSI standards.
Laser safety windows are not a substitute for laser safety eyewear.
How to Select a Laser Safety Window
When selecting a laser safety window, the following criteria should be evaluated:
Laser wavelength
Required Optical Density (OD)
Laser power or energy
Visibility requirements
Mounting or enclosure requirements
Application environment
The first step is always identifying the wavelength of the laser system being used.
The second step is determining the level of protection required. The recommended Optical Density (OD) is ultimately a function of both:
The laser output
The level the exposure must be reduced to
This allowable exposure threshold is known as the Maximum Permissible Exposure (MPE). The Laser Institute of America (LIA) OD Calculator can help qualified laser safety personnel estimate recommended Optical Density requirements based on laser parameters and ANSI Z136.1 guidance. The calculator should be used as part of a broader laser hazard evaluation process.
If you are unsure which OD is appropriate for your application, consult your Laser Safety Officer (LSO), contact our team, or call us directly to discuss your laser system and operating conditions.
Why Wavelength Matters
Laser safety protection is wavelength-specific.
Different wavelengths interact differently with the human eye and skin, which is why laser safety standards specify different protection requirements depending on the exact laser wavelength being used.
Knowing only the general category of the laser — such as ultraviolet (UV), visible, or infrared (IR) — is not sufficient when selecting laser safety protection.
For example:
A 532 nm laser
A 755 nm laser
A 1064 nm Nd:YAG laser
A 10,600 nm CO₂ laser
all require different types of laser safety protection and often utilize completely different filter technologies.
Laser safety windows should always be selected based on the specific operating wavelength(s), laser parameters, and application environment.
Understanding Optical Density (OD)
Optical Density (OD) refers to the amount of laser radiation attenuated by a protective material at a specific wavelength.
Higher OD values indicate greater attenuation of laser energy.
For example:
OD 1 = 10x attenuation
OD 2 = 100x attenuation
OD 3 = 1,000x attenuation
Different laser safety windows are designed for different wavelength ranges and protection levels.
Laser safety products should never be selected solely by choosing the “highest OD.” Proper selection depends on:
Wavelength
Laser power
Exposure duration
Beam geometry
Reflections
Visibility requirements
Applicable laser safety standards
For a more detailed explanation of Optical Density, see our Optical Density (OD) guide.
What Is Visible Light Transmission (VLT)?
Visible Light Transmission (VLT) describes how much visible light passes through a laser safety window.
VLT affects:
Brightness
Color perception
Visibility
Operator comfort
Situational awareness
A useful comparison is sunglasses:
Some sunglasses block a large amount of light but make everything significantly darker. Other sunglasses maintain better visibility and color recognition while still reducing brightness effectively.
Laser safety windows operate similarly.
Some filters provide extremely high laser attenuation but reduce visibility substantially, while others maintain higher visible light transmission depending on the application and filter design.
Higher VLT is not always “better.” In many laser safety applications, increased attenuation and reduced transmission may be necessary to achieve the required level of laser protection safely.
Different applications may prioritize:
Maximum visibility
Color recognition
Higher attenuation
Broader wavelength coverage
Operator comfort
Reduced visual fatigue
For a more detailed explanation of Visible Light Transmission (VLT), see our article:
Understanding Visible Light Transmission (VLT) in Laser Safety Glasses & Windows
| Acrylic Class 4 | Glass | Low-level "laser-shielding" |
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 |
Custom Sizing | Yes | Yes | Yes |
Price | Higher | Higher | Lower |
Optical Density[ii] | Higher | Higher | Lower |
Optical Density refers to a general trend should look at the specifications of the eyewear before purchase.
Laser Safety Windows Are Not a Substitute for Eyewear
A common misconception is that laser safety windows eliminate the need for laser safety eyewear.
This is not proper laser safety practice.
According to ANSI laser safety guidance and common industry best practices, individuals working around Class 3B and Class 4 laser systems should still wear appropriate laser safety eyewear even when laser safety windows are present.
Laser safety windows are typically part of a larger laser safety system that may include:
Engineering controls
Beam enclosures
Administrative controls
Laser barriers or curtains
Interlocks
Warning systems
Laser safety eyewear
If you have questions regarding your specific setup, contact your Laser Safety Officer or our team directly.
Common Questions About Laser Safety Windows
Is twice the thickness equal to twice the protection?
No.
For many laser safety windows, the attenuation properties are primarily determined by the filter material and dye composition rather than simply the material thickness.
In many cases, different thicknesses are used primarily for:
Structural requirements
Mounting requirements
Mechanical durability
Integration into enclosures or machine systems
Always review the actual Optical Density specifications for the product rather than assuming thicker material automatically provides higher protection.