Due to increasing laser pointer attacks the LFM (Laserzentrum Fachhochschule Münster) carried out specific investigations concerning the hazard potential as well as evaluation of possible preventive measures.
This was done by a selection of 40 laser pointers from suppliers from Far East, featured by wavelengths from 405 nm up to 655 nm ("blue", "green", "red") and output power up to 1000 mW. It was shown that the specified output power was significantly exceeded up to a factor > 20 for most cases.
MPE values (Maximum Permissible Exposure) for eye injury and glare effects were taken from European and US standards (DIN EN 60825-1, ANSI Z136). Based on these MPE’s safety distances were calculated and simulated for the particular eye hazards. Theoretical models were developed taking into account not only beam parameters but also atmospheric absorption and reduced transmission of wind screens from aircrafts/helicopter and vehicles.
Field tests were carried out by using a helicopter from the German Federal Police. During test flights the typical time for eye illumination from a handheld laser pointer at a distance of 500 m was measured to a few 10 ms (inside the helicopter cockpit the human eye was simulated by a 7 mm aperture combined with a power sensor). Further test flights were performed by using filter foils which were applied at the bottom windows from the cockpit. As reported from pilots this measure failed.
Further investigations revealed that radiation from laser pointers shows a strong polarization up to 99 %. It also could be seen that in case of blue and red laser pointer radiation characteristical "hot spots" appear within the intensity profile. Depending on power and duration of the illumination of the human eye either a retina injury or various glare effects may occur. The results show that eye injury may happen up to several 100 m using commercial available laser pointers. Glare effects are still possible even at several 1000 m.
Laser safety goggles nowadays are commercially available for all standard pointer wavelengths. However, a changed perception of the natural visual sensitivity is inherent. Thus applications may be only found for specific professional groups. Active safety goggles are promising in order to overcome these problems; however, these are still in the prototype stage. Also of interest are novel "nano structured films" using "meta materials" offering protection for all available pointer wavelengths at the same time but however, these films are still under investigation within testings.
trafficType of hazard:
prevention, radiationDescription, key words:
laser pointers, pilots, drivers of public transportation