A comprehensive resource for safe and responsible laser use

US: MIT develops laser to deliver secret audio messages

Researchers at the Massachusetts Institute of Technology (MIT) described a way to use a laser beam to deliver a message that could be heard only by the person to whom the beam was directed.

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.

US: Autonomous car lidar said to damage camera sensor

Autonomous cars often use laser lidar (light detection and ranging) systems as one of the vision inputs. One or more lidar systems, often on the roof, scan the car's surroundings to determine distance to the road and roadside objects. The lidar laser is in the infrared part of the spectrum, so it is not visible to human eyes.

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).

New Zealand: Pilots, legislator want total ban on handheld lasers over 1 mW

A bill has been introduced in New Zealand to make it illegal to possess a high-power laser pointer (battery operated, handheld, above 1 milliwatt power) "without reasonable excuse." Currently it is legal to have such a laser pointer as long as it is not in a public place.

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.

Canada: Study first to show prevalence of laser use, injuries among general public

A 2014 health survey by Statistics Canada, reported in January 2019, is the first study to show the prevalence of laser usage and of laser injuries among a large sample of the general public in any country or region. 19,765 individuals were surveyed in the study.

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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Japan: Laser pointer safety symposium held

On January 15 2019, the first "International Symposium on Laser Pointer Safety" was held in Tokyo.

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.