LASER: The invisible danger

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Blinding law enforcement officers with a laser during protests is becoming increasingly popular. This trend can be observed more and more frequently at various so-called "demos" in the USA and Europe. What may sound harmless at first is not. The cheap but extremely powerful lasers from the Far East can burn your retinas. So how can you protect yourself? Revision has a guide for you:

LASER SPECIFICATIONS

There are three key specifications for laser products to consider when looking for eye protection from lasers. The power level of the device (measured in milliwatts), the color of the laser it emits (expressed as its wavelength in nanometers), and the beam divergence (measured in minutes of angle or milliradians.) We will cover power and color in more detail. Beam divergence indicates how tightly focused the laser beam is. Wider beams pose less of a threat.

POWER

Handheld lasers used in street protests range from mostly harmless keychain laser pointers with low power to high-intensity handheld lasers that can match the power of lasers used by the military to mark targets miles away.

How do you know the level of danger you are in when being illuminated by lasers? The bottom line is, you simply don't know, and the protesters shining light beams at you probably don't even know how strong their lasers are. Here is our article on laser classes.

Because it is more expensive to manufacture a less powerful laser that meets safety standards than a more powerful one that does not, it is common to order a 3mW laser over the internet. Unfortunately, you may receive a laser ten times stronger than indicated. Therefore, you can safely assume that any laser shining on you is strong enough to be dangerous.

POTENTIAL INJURY

The worst injury is the irreversible burning of the retina by a strongly focused light. The more common but equally serious danger posed by lasers is the loss of situational awareness.

A laser in the eye has the same effect as any other bright light source. It initially triggers a reflex that makes you blink. If you continue to stare into the laser, you will be blinded and have trouble seeing. If you continue to stare at the beam, you will temporarily see bright spots known as afterimages. These effects are not as severe as permanent blindness, but situational awareness is the last thing you want to lose, especially in the potential danger of flying bricks and homemade pyrotechnics.

INVISIBLE DANGER

The good news: You have an involuntary blinking reflex. The bad news: The blink reflex only occurs when the offending light is in the visible spectrum, and cheap lasers are often contaminated with invisible IR and near-IR light.

This means that a weak, visible 5mW laser may emit hundreds of mW of light in the near-IR spectrum. If your eyes start itching and burning for no apparent reason, it's a sign that the light is burning your retina.

HOW TO STOP A LASER?

At the most basic level, the color of a laser is its Achilles' heel. Want to stop a red laser? Put a red-absorbing filter in its path. Generally, laser protection lenses look opposite to the color they absorb. Of course, there is more to blocking a laser, but an important consideration when looking for laser eye protection is knowing the color of the light you want to block. Manufacturers of laser eye protection specify this as a specific wavelength or range in nanometers (nm).

LENS DESIGN CONSIDERATION

Creating a lens that stops a laser involves choosing a dye that absorbs light at the same wavelength as the laser. This can be done in the form of a coating applied after manufacturing a glass or polymer lens, or by mixing the dye into the base material of a polymer lens before shaping it. The latter method of construction results in a much more durable form of laser protection, as the dye is impregnated into the lens and cannot be scratched off.

Most laser protection lenses are manufactured for use in a laboratory or production line where there is no requirement for ballistic eye protection. There are only a few companies manufacturing laser eye protection that also provide ballistic protection in the mil-spec spectral range.

CHOOSING THE RIGHT LENS

It would be great to have a lens that blocks all laser wavelengths, but that doesn't exist. A lens that would block all laser colors would have to filter out all light colors (wavelengths). This can be done, but then you won't see anything. Since each lens can only provide laser protection at a certain wavelength or range, it is crucial when selecting a protective lens to know which color lasers you will be facing.

Consider carefully at which time of day you will be using the laser eye protection. Night is the right time for chaos, so the lenses should not be too dark. The indication of how much light a lens allows to pass through is called visible light transmission (VLT). VLT indicates how much (daylight) light a lens lets through as a percentage. Higher percentages allow more light through.

Another crucial specification is the optical density (OD) of a lens. OD indicates how much laser light is blocked by the lens. It is generally given as a number from 0 to 7, with higher numbers providing the greatest protection. Each additional OD absorbs ten times as much laser light, so a lens with OD 3 absorbs ten times as much light as a lens with OD 2.

Practically speaking: The higher the OD, the more laser energy a lens can absorb. The higher the VLT, the more light penetrates the lens.

BEWARE OF IR-ONLY LENSES

Before heading out with the protective goggles supplied with your IR target lasers, make sure these lenses also provide protection in the visible light spectrum. These IR protection glasses generally only stop lasers in the IR/near-IR spectrum and may not necessarily provide protection against visible lasers.

OUTLOOK

In short, it is difficult to protect oneself from glare from all laser sources at this time while still maintaining situational awareness. Essentially, there will be nothing left to see since everything would be filtered out. Those who want to protect themselves sacrifice a part of their visual perception.

Current research and development in the field of tactical eye protection against lasers focus on finding a compromise solution that provides full-spectrum laser protection, unimpeded vision, and ballistic protection at mil-spec level. Revision already offers a wide range of different laser protection lenses.

REVISION online: www.revisionmilitary.com