A comprehensive resource for safe and responsible laser use
The research was presented by Jason Keleher, Ph.D. and research assistant Daniel Maurer on March 31 2019 at an American Chemical Society meeting in Orlando, Florida. Here is a summary:
"To develop their new approach, the researchers took advantage of liquid crystals -- materials with properties between those of liquids and solid crystals that make them useful in electronic displays. The team placed a solution of liquid crystals called N-(4-methoxybenzylidene)-4-butylaniline (MBBA) between two 1-inch-square panes of glass. MBBA has a transparent liquid phase and an opaque crystalline phase that scatters light. By applying a voltage to the apparatus, the researchers caused the crystals to align with the electrical field and undergo a phase change to the more solid crystalline state.
Liquid crystals sandwiched between two1-inch squares of glass (left images) scatter green and blue light on a wall when the cells are triggered by laser illumination (right images). Image credit: Daniel Maurer, Lewis University
"The aligned crystals blocked up to 95 percent of red, blue and green beams, through a combination of light scattering, absorption of the laser's energy and cross-polarization. The liquid crystals could block lasers of different powers, simulating various distances of illumination, as well as light shone at different angles onto the glass.
"In addition, the system was fully automatic: A photoresistor detected laser light and then triggered the power system to apply the voltage. When the beam was removed, the system turned off the power, and the liquid crystals returned to their transparent, liquid state. "We only want to block the spot where the laser is hitting the windshield and then have it quickly go back to normal after the laser is gone," Keleher notes. The rest of the windshield, which was not hit by the laser, would remain transparent at all times.
"Now that the researchers have shown that their approach works, they plan to scale it up from 1-inch squares to the size of an entire aircraft windshield. Initial results have shown that a sensor grid pattern on 2-inch squares of glass will respond only to the section of glass that is illuminated. The team is also testing different types of liquid crystals to find even more efficient and versatile ones that return to the transparent state more quickly once the laser is removed."
The lasers start at about 0:27 and last until about 0:55 in the video, which is 3 minutes 12 seconds long. A few times, the lasers appeared to go directly into the crowd — or at least towards the camera that captured the show.
As the biplane lands, starting at about 2:29 the laser projector can be seen as a square black box mounted above the top wing.
The show was created by Scandinavian Airshow. The company says "The Catwalk is the ultimate air show aircraft and can in the evening transform into a pyrotechnic platform and perform its amazing night pyrotechnic display." There is no mention of lasers on their Catwalk webpage as of March 12 2019, so this may be a relatively new addition.
As one YouTube commenter wrote, "That's hella ironic if a plane is shooting lasers at you 😂"
From YouTube, via BGR
In March 2019, a YouTube video showed laser tattoo removal damaging a high-end digital camera sensor just by taking a video of the laser pulses on the skin.
The laser beam did NOT directly enter the Sony A7SII lens. And yet with every tattoo removal pulse of the green laser, the camera sensor was obviously damaged. According to the person posting the video, "The repair cost was about as much as a new camera [about $2200] so try to avoid this."
If a laser is powerful enough, just looking at the dot of the laser on a wall can be a "diffuse reflectance hazard." In this case, the reflected laser light was powerful enough to damage the sensor.
This is not a flaw in the laser or the camera. As described elsewhere, camera sensors are generally more sensitive than the eye.
Also as noted, different cameras may have different sensitivities depending on many factors. For example, this page includes four YouTube videos showing laser tattoo removal, without any apparent damage to the video sensor.
Laser pointers and handheld lasers are almost always emit continuous wave light. CW lasers can damage the retina by heating it up, while pulsed lasers create an "acoustic shockwave" which instantly causes a popcorn-like explosion in the retina.
According to this page, a typical tattoo removal laser has a maximum pulse energy of about 1-2 Joules and a pulse width of about 5-10 nanoseconds. It is not known how powerful the laser was in the video.
Everyone in the room should have been wearing laser safety glasses or goggles that reduce the laser light to safe levels. If the camera had been shooting through the safety glasses' lens, the damage likely would not have occurred.
From various sources including Reddit, Digital Photography Review, Petapixel, and SlashGear
The study looked at 77 case reports of laser eye injuries in children. In four of the cases there were reported psychological or behavioral issues.
In addition, the authors had experience with four children with laser eye injuries; in three of these cases there were psychological or behavioral issues.
One of the authors sent a survey to 990 consulting ophthalmologists in the U.K. This found 159 cases of macular injury due to "misuse of a handheld laser device," with 80% of those injured being children or teenagers. In 35% of the cases, the injury was self-inflicted; in 36% it was caused by a third-party. (The remaining 29% seem to be uncategorized although the paper notes that "there were no cases of assault reported." In 67% of the cases where the laser power was known, it was under 50 milliwatts.
The paper cautions that the actual number of laser injuries seen by the ophthalmologists may be higher: "A limitation was the poor response rate and thus data so obtained do not provide the true incidence and clinical features of such cases."
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The most common laser color reported by pilots is green, representing approximately 90% of reports made to the U.S. Federal Aviation Administration. As of 2019, the most common green is 532 nanometers, produced by low-cost, high-power diode-pumped solid state laser pointers and handhelds.
metaAIR's first offering protects against 532nm green laser light, using holographic "nano-pattern layers". These can precisely reflect 532nm light while allowing high visibility for other wavelengths — crucial for pilots' night vision and for correct color discrimination of cockpit instruments and airport lighting. MTI adds an additional layer to improve color balance and discrimination, as well.
The eyewear is said to have an Optical Density between 2 and 5, meaning that it will attenuate the amount of 532nm light reaching eyes by 100 to 100,000 times. The primary goal is to reduce or eliminate visual interference effects such as flashblindness, glare and distraction. A secondary benefit is that attenuating 532nm light will also help protect against any potential eye injury. (Note that as of February 2019, no documented pilot eye injuries have occurred according to the U.S. FAA, U.K. CAA and Transport Canada after almost 75,000 reports of aircraft illumination. Laser/aviation safety experts consider visual interference to be a more significant safety concern than pilot eye injuries.)
The frame is wider at top, sides and bottom, to block light coming from directions other than the front.
MTI originally developed the holographic laser-reflecting technology for use in windscreens. The goal was to protect pilots without the need for eyewear. However, windscreen modifications require a slow, multi-year process of obtaining governmental and airline approval. In addition, the cost to modify windscreens is much higher than the cost of one or two pairs of eyewear. So eyewear was a natural choice for the first commercially available laser protection product from MTI. According to its metaAIR website, the company may also produce glare shields using the same technology.
MTI is taking pre-orders for its eyewear, distributed by Satair, which will be available "spring 2019."
From MTI's metaAIR website, accessed February 25 2019.
Their paper describing this, "Photoacoustic communications: delivering audible signals via absorption of light by atmospheric H₂O", was published in January 2019. The abstract is as follows:
We describe a means of communication in which a user with no external receiver hears an audible audio message directed only at him/her. A laser transmits the message, which is encoded upon a modulated laser beam and sent directly to the receiver’s ear via the photoacoustic effect. A 1.9 μm thulium laser matched to an atmospheric water vapor absorption line is chosen to maximize sound pressure while maintaining eye-safe power densities. We examine the photoacoustic transfer function describing this generation of audible sound and the important operational parameters, such as laser spot size, and their impact on a working system.
The laser is said to be eye- and skin-safe. The system can currently send a sound up to 60 dB across a distance of 2.5 meters (8 feet). In the future they are hoping for a range of 100-500 meters (328-1,640 feet). It is useful for applications as diverse as notifying one person in a crowd, and for headphone-free listening. MIT is patenting the technology.
From R. Sullenberger, S. Kaushik, and C. Wynn, "Photoacoustic communications: delivering audible signals via absorption of light by atmospheric H₂O," Opt. Lett. 44, 622-625 (2019). A PDF of the article is here. News stories about this appeared in numerous publications including Digital Trends, Photonics.com and The Sun.
In early January 2019, a man attending the CES technology show in Las Vegas claimed his Sony A7RII camera's sensor was damaged by the lidar from a company called AEye. Jit Ray Chowdhury said all photos taken after he snapped pictures of the AEye functioning lidar had two purple spots with lines emanating from them:
AEye said that "cameras are up to 1000x more sensitive to lasers than eyeballs. Occasionally, this can cause thermal damage to a camera's focal plane array."
The company offered to replace Chowdhury's camera. Curiously, Chowdhury said he could not find the camera. As laser expert Jeff Hecht wrote, "without the camera it remains unknown what the nature of the damage was, when it occurred, and what caused it."
Companies using lidar for autonomous vehicles choose systems which are safe for human eyes. However, as the AEye incident indicates, some types of lidar may not be safe for camera sensors. These tend to be systems using pulses of laser light, rather than continuous laser light.
From Ars Technica (initial report) and IEEE Spectrum (additional information on lidar characteristics for eye and sensor safety).
The bill would double penalties for violations from the current 3 months imprisonment or $2000 fine, to 6 months or $4000. And it amends the Crimes Act 1961 to make explicit that interference with a transport facility includes using a high-power laser pointer to reduce the ability of aircraft crew to perform their duties.
The High-power Laser Pointer Offences and Penalties Bill was introduced September 6 2018 by Clutha-Southland MP Hamish Walker.
The president of the New Zealand Airline Pilots Association said "We are asking for a prohibition primarily because the risk outweighs markedly, any utility they are having in society. We don't believe they need to be in the country there is plenty of other alternatives as we are calling for a complete prohibition."
In Wellington in August 2018, a $20 million control tower was opened. On its first day of operation, several staffers reported a laser being aimed in their eyes. Some had to lie down after experiencing nausea.
A police database of incidents found 311 reports in 2018 using the keyword "laser."
From the High-power Laser Pointer Offences and Penalties Bill and NewstalkNB.
It showed that 48 percent of Canadians over the age of 12 either used or were exposed to lasers, annually.
Of those who reported using a laser product, 1.1% reported discomfort or injury.
[LaserPointerSafety.com analysis: Based on 2016 Canadian census data, there were 29,312,165 Canadians age 15 or older — data was not available on age 12+. If 48% of these 29 million Canadians used or were exposed to lasers, that would be just over 14 million people. If 1.1% of them experienced discomfort or injury, that would be about 155,000 Canadians with laser discomfort or injury.]
Returning to the Statistics Canada study, of the discomfort/injury cases:
- 41% were for skin injuries "such as rash, itch or pain," while 59% were for eye injuries "such as itchiness, pain, visible floating objects, blurred vision, burn, flash blindness, excessive watering or loss of sight."
- In 64% of cases, the discomfort or injury lasted less than two days; in 34%, it lasted more than two days.
- The discomfort/injury was caused by the person's own use of the laser in 25% of cases, and by someone else's use in 75% of cases.
- 39% of the discomfort/injury cases were caused by cosmetic treatments, 26% were caused due to laser pointers, and 34% were caused by "other" which included surveying tools, entertainment lasers, materials processing, and scanners.
The study analyzed published eye injury case reports since 1999, and concluded:
"…the majority involved the misuse of a handheld battery-operated laser product by an adult or a child. Most of these injuries were the result of irresponsible use or deliberate staring at a laser by a child, or the result of the inappropriate use of a high-powered laser device (Class 3B or 4) in an 'uncontrolled environment'....In the cases reported in 2014 that included long-term follow-up injury reporting, about one-half of the ocular injuries resolved within one to two weeks, with the other 50% of patients sustaining longer-term visual impairments."
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There were two main goals: 1) Raise awareness of problems caused by laser pointers and consumer lasers such as home cosmetic lasers, and 2) Try to find ways to mitigate and regulate these lasers, both for Japan and hopefully for other countries as well.
The symposium was sponsored by the Optoelectronics Industry and Technology Development Association. OITDA is a standardizing body developing the optoelectronics related standards which concern Japanese domestic standards such as JIS and the international standards such as ISO or IEC. OITDA also founds its own OITDA standards system that complements the domestic and the international standards.
The symposium was presented in the Roppongi Hills Auditorium, on the 49th floor overlooking the city and Mt. Fuji. There were approximately 40 attendees. Simultaneous translation from Japanese to English, and English to Japanese, was provided. There were four invited speakers:
- Professor Yuichi Hashishin of Kindai University spoke on "The current situation of the safety of laser pointers in Japan." He presented various cases and statistics about laser eye injuries and laser illumination of aircraft. For example, from 2012 through 2015 there were less than 40 pilot reports of laser illuminations in Japan, though this number did jump to 194 reports in 2016. He also was concerned about lasers being pointed at cars, trucks, buses, trains and other vehicles, feeling that perhaps a number of fatal automobile accidents were due to lasers but of course the victims could not confirm this.
- Next to speak was Patrick Murphy of LaserPointerSafety.com. He briefly reviewed current laser eye injury and pilot illumination concerns. He then presented suggestions for action, based on this page at his website.
- Dr. Martin Lindgren of the Swedish Radiation Safety Authority (SSM) discussed Swedish regulations concerning handheld lasers. He presented information on current problems, including that laser illuminations of pilots had risen from five in 2008, to around 140-150 from 2011 to 2015, with a decline to 62 in 2018. He described an ongoing 4-year research project to determine the probability of eye injury from handheld lasers at a distance; results may be available in 2020. Finally, he discussed Swedish law which includes a requirement for a license to own a handheld laser over 1 milliwatt.
- The final speaker was Atsutomo Hama of Nichia Corp., who presented "History of management of high-power laser diodes." Nichia sells high-powered multi-watt blue diodes used in projectors, lamps and other applications. Nichia wants to avoid these diodes being stolen or being removed from products so they can be put into hazardous handheld lasers. He described some of the methods Nichia uses, including a 2D code (similar to a QR code) put onto each diode to help track its manufacturing and sale.
There were a few questions for each speaker, but no additional discussion among the attendees. OITDA's Kenji Murata, who helped organize the symposium, indicated that there was additional funding for two more years.
Report by Patrick Murphy who attended the symposium as a guest of OITDA.