A comprehensive resource for safe and responsible laser use

Laser use during protests

This page discusses the use (and misuse) of lasers during protests, demonstrations, riots and other civil disturbances. Shown below are protesters in Hong Kong in August 2019.
     
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Why lasers are used at protests

Lasers are used at protests for various purposes:

  • Aiming at authorities to distract or temporarily flashblind them. This might be done to disrupt the authorities' view of the people in front of them (e.g., those holding the lasers). Or it could be more planned, as a diversion to draw authorities' attention from another area of the protest.

  • Aiming at authorities to try to inflict eye or skin injuries. Powerful handheld lasers may cause eye injuries at close range. However, serious or permanent injuries do not generally occur for reasons discussed elsewhere on this page. (Be wary of any official accounts of eye injuries. They may not be accurate unless the patient has been assessed by an expert with experience in laser eye injuries.) As for skin injuries, usually handheld lasers are not powerful enough to injure uncooperative persons' bare skin at any reasonable distance. Also, the person will feel the heat build up and will turn away before any significant burn occurs.

  • Aiming at camera sensors to temporarily flashblind, or permanently disable cameras. This was done in the August 2019 Hong Kong protests to try and shut down facial recognition systems used against protesters.

  • Aiming at buildings, helicopters, crowds, etc. to gain attention. This is the visual equivalent of shouting or chanting. There is no intent to harm or do anything other than to express displeasure against a target such as a police station, or to gain attention for the protest. (Of course, aiming lasers at people and aircraft is potentially hazardous and thus may have unintended consequences.)

Defending against laser attacks

Authorities can defend against lasers in a number of ways:

  • Persons directly illuminated by laser beams can blink, look down or look away. This reduces the amount of time the laser is in the eye and thus reduces any heat buildup. (Injuries from visible laser light are possible when the eye's lens focuses the light onto the retina. Whether an actual injury occurs depends on the power of the laser and the length of time it is in any one place on the retina. Also, by looking away, if there is an injury it would not be in the center of the visual field which is most important for good vision.)

  • Helmet shields can be equipped with tinted laser-absorbing strips that reduce the light brightness. Usually these are effective against the most common laser color used at protests, green, but advanced strips may also protect against other colors. Photos and a description of such a laser-absorbing strip is at a news story here. An advantage of the strip is that the wearer just tilts his or her head down so they are looking out the strip; nothing needs to be put on as is the case with glasses.

  • Laser glare protection eyewear may be used by pilots or others facing constant laser harassment, who need to protect a full visual field (not just a strip). Some police air services and demonstration officers have been issued such anti-laser glasses.

  • Laser-wielding demonstrators generally can be easily identified. The visible laser beam points right back to the person holding it. Police can counter in real-time (arrest) or can use photos/video to later try to apprehend laser attackers.

  • Police can use bright light as well. In the August 2019 protests, the Hong Kong Journalists' Association accused police of aiming "strong flashlights" at journalists to obstruct their reporting.
   

Lasers at protests are unlikely to cause eye injuries

Photos of massed laser beams aimed at police, like the one at the top of the page, can be dramatic. But how effective are lasers in protests?

In terms of causing eye injuries to police, in general lasers are not effective. Even if a person wanted to cause an injury, it is hard to do so by handholding a laser beam on an uncooperative person many yards or meters away who can close his or her eyes, or who can simply look away.

Authorities or the press may try to indicate these are dangerous weapons. During the August 2019 Hong Kong protests, police held a press conference where they showed a laser at a close range (roughly 20 inches or 1/2 meter) being steadily aimed at a motionless sheet of newspaper:



After a few seconds of being held on a dark (light-absorbing) part of the newspaper, smoke appeared:



However, in real-world protest conditions it is much less likely the laser could burn the paper. At longer distances such as from a protester to a police officer it is harder to keep the laser on a single spot so that heat builds up. The target can blink or move. The beam spreads as it travels, lessening the light energy density (a larger beam "dot").

To counteract the police claims, a protester held up a newspaper while dozens of lasers tried to burn it — "without success" according to a news story.



This is not to say that laser light is completely safe, or that it should be deliberately aimed at anyone's head. Hong Kong police said "three of our officers received medical treatment after protesters shined laser guns at them." The nature of any injury was not reported.

Anyone hit by a beam, and concerned about injuries or aftereffects, should read the page "If you are hit by a laser beam."
   

Lasers can block or damage cameras

Laser pointers aimed at surveillance cameras can temporarily flashblind the camera, or can damage the sensor. The photo below shows flashlights (white on left side) and lasers (green in middle and right) being aimed towards a news camera. People near the lights are obscured. The one laser at right that is aimed most directly into the camera is blocking a view of many persons on the right side.



For blocking the view to be effective, the laser's light would need to stay on the camera lens. In most cases, as soon as the laser is taken away, the view returns.

If the laser is powerful enough, the sensor can be damaged. This may take the form of dark spots where the laser was brightest, or of horizontal or vertical lines where the laser damaged an entire row of pixels. Since the "injury" is localized, the rest of the camera sensor may continue to work.

Demonstrators would not know whether a given camera was damaged, unless they could somehow see its output.

Persons in the area where laser pointers are being used should take care with a camera. This includes smartphone lenses, and still and video cameras. A single direct hit from a powerful laser may permanently damage the sensor. This damage can occur even if the camera is turned off if there is no physical shutter on the lens, as with smartphones and some mirrorless cameras. Journalists may wish to use lower-cost cameras to take photos or videos when laser beams are coming towards them. This avoids damaging expensive top-of-the-line equipment.

It should be noted that camera sensors are more sensitive to bright light damage than the human retina. So the fact that a camera sensor was damaged does not automatically mean that an eye would also be injured by the same laser under the same conditions.

Are lasers "offensive weapons"?

As to whether laser pointers should be classed as "offensive weapons," that would depend on the potential or intended use.

To give an analogy, kitchen knives are widely available and are not considered to be weapons when used at home for cooking or cutting objects. But if a person carries a kitchen knife to a rally — or worse, pulls it out and aims it towards an officer — then it could be considered as an "offensive weapon."

In addition, the nature of the "weapon" should be considered. If a person has a butter knife on them (e.g. a legal 1 or 5 mW laser pointer), this is different than having a steak knife or carving knife (higher powered handheld laser).

Finally, the nature of the target should also be considered. If cameras are important to police, and they can be blocked or damaged by laser light, then this could also be considered as "weapon" use. The intent is to deny police one of their crowd control tools. (As to whether surveillance camera information is misused, that is a political question that might differ in each case or jurisdiction.)

On the other hand, if lasers are used simply to make a dramatic point, such as aiming them at a building, this is not a "weapon" but instead goes back to the purpose of a laser pointer: to point out or draw attention to objects of interest. This assumes the lasers are not deliberately aimed at occupied windows or cameras on a building, but are just used to make patterns on a building as shown below.


     

Lasers compared to knives as weapons

The graphic shown here describes general similarities between lasers and knives.
  • Both are useful tools which can become weapons when used with ill intent.
  • Both come in many different types, which can have very different damage potential.

For example, low-powered pointers are safe for household use by adults, while higher powered handheld lasers should only be wielded by someone knowledgeable and cautious about their danger.

Knifes cause much more harm than lasers

However, there are also significant differences between lasers and knives as weapons.

As the text at the bottom of the graphic indicates, knives are much, much more hazardous than lasers.

For one thing, laser safety distances such as the NOHD are usually very conservative. Laser beams do spread out with distance; this reduces the energy in any one area. For this reason, noticeable or significant injury does not occur until much closer to the laser device than the conservative, "safe" distance.

For another thing, it is usually easier to defend against a laser attack. A person can close their eyes or look away to reduce or eliminate any harmful eye injuries.

About the pictures

The lasers pictured in the graphic give a general idea of the output. But note that a single type of laser such as the "Laser 303" shown for the 500 mW illustration, can come in powers from 10 to 1000 mW. For this reason, don't use the illustrations to determine the power of a laser you might have.

Also, the information printed on a laser about its power output may be wildly inaccurate.

Police and the press should be especially aware that the information printed on a laser device may be inaccurate.
     

Details and additional information