how safe are NIR LEDs?

[orangefish 0]

Hello,

 

I am looking for information on the safety of NIR LEDs commonly used in consumer night cameras now a days. Any resource which describes this in detail?

 

Or if anyone has insights into the safety factors compared to the distance between LEDs and eyes, that would be great too.

 

 

 

Thanks.

[scorpion 0]

http://scorpiontheater.com/irlab.aspx

 

http://en.wikipedia.org/wiki/Light-emitting_diode

 

http://en.wikipedia.org/wiki/Infrared

 

Fiber optic communication systems present a possible or potential hazard to the eyes of engineers and technicians who work with or maintain these systems. To investigate this hypothesis, the retinas of macaque monkeys were exposed to near infrared cw radiation and to GaAs lasers modulated at 22 MHz and 1600 Hz. Trained animals (two) were exposed monocularly under normal physiological conditions to modulated GaAs lasers for several months, on a 5 day/week basis, 1000 sec/day. No loss of visual function or funduscopically visible damage was detected. One of these animals was sacrificed and examined histologically for damage. No differences were detected between the foveae of the exposed and control eyes in this monkey. The radiant exposure in J . cm^-2 required to produce minimal lesions was determined on anesthetized animals for cw radiation at three wavelengths (820, 860, 910 nm) and for radiation at 830 nm from a GaAs laser modulated at a digital rate of 44 Mbit/sec. It required from 6 to 8.4 mW of GaAs radiation entering the eye for periods ranging from 400 to 3000 sec to produce a detectable lesion. Since the spot size on the retina was <50 µm in diameter, it is difficult if not impossible to imagine how the human eye could remain focused on such a source for an appreciable time, even if 8 mW were entering the pupil. Extrapolation to man is always dangerous, but these experiments do not suggest that engineers and technicians operating and maintaining fiber optic communication systems are subject to an ocular risk unless they use magnification optics

 

_____________________________________________________________

Appendix H of this Standard refers manufacturers to ANSI RP27.1 and RP27.3 to apply Safety Standards for LED’s.

 

 

Questions have arisen as to whether laser or incoherent radiation exposure limits ( ELs) should

be applied to LED emitters. Based upon current exposure limits from the International

Commission on Non-Ionizing Radiation Protection (ICNIRP), most LEDs - particularly surfaceemitting

LEDs — pose no clear hazard to the eye. Current surface-emitting LEDs produce

exposure levels at the retina which are less than 1% of the levels that are known to cause retinal

injury even when the LEDs are viewed at extremely close distances (e.g., at 10 cm) (Sliney and

Wolbarsht 1980). At typical viewing distances of 0.5 to 2 m, the levels are less than 0.1% of

retinal injury levels. Even lengthy exposures of the cornea and lens of the eye pose no hazards

whatsoever. From a safety standpoint, LEDs have been treated both as lasers (e.g., in IEC

standard 60825-1-2001 and in ANSI Z-136.2-1997, and as lamps (CIE 1998; ANSI/IESNA 1996).

Because of some confusion relating to the actual risk, ICNIRP organized a panel of experts to

review the potential hazards of current diode emitters and they reported their findings in 1999

(ICNIRP, 1999). This tastk group noted that laser diodes are constructed with miniature resonant

cavities with gain, produce a very narrow spectral bandwidth, can generally achieve shorter pulse

durations, are not limited in radiance, and can emit much higher radiant powers than LEDs.

Light-emitting diodes of low to moderate brightness (luminance) are used in many types of visual

displays, as indicator lights and many related products. Higher power LEDs and IREDs are used

as signal lamps and in a wide variety of domestic and industrial products, and can compete with

laser diodes in limited optical communications systems, i.e., in local-area networks (LANs). They

are generally not competitive with laser diodes because of their radiance limitations. These

differences in output characteristics define both their uses and their potential eye hazards. Most

current LEDs--and all surface emitting LEDs--have very limited radiance and do not pose any

realistic eye hazard, despite the fact that they have been included in some laser safety standards

in the past few years (IEC, 2001).

After a careful review of all possible emission characteristics of surface-emitting LEDs and

IREDs, the ICNIRP concluded that these would be judged safe by applying the ICNIRP Exposure

Limits (ELs) for incoherent radiation. This conclusion applies as well if one follows the

recommendations of CIE TC 6-38 (Lamp Safety) for realistic viewing conditions. This conclusion

applies to any LED device which does not have optical gain. Only as a result of applying

extraordinarily "worst-case" assumptions and simplifications that are built into some current

product safety standards, can anyone arrive at the conclusion that an LED or IRED poses a

retinal hazard. On the other hand, the use of laser ELs and IEC 60825-1 measurement

techniques to evaluate LEDs could result in an understatement of the lenticular risk if the source

is very large and the lens becomes overheated. Thus, the ICNIRP recommended that safety

evaluations and related measurement procedures for LEDs follow the guidelines for incoherent

sources (ICNIRP 1997). This approach provides the most accurate assessment of incoherent

sources without problems originating from certain underlying assumptions about lasers that

remain incorporated into the limits developed for collimated laser beams. They also conclused

that diode lasers and VCSELs be treated in all safety evaluations and safety standards as lasers.

 

_____________________________________________________________

 

ICNIRP STATEMENT

http://www.icnirp.de/documents/led.pdf

 

ICNIRP GUIDLINES

http://www.icnirp.de/documents/broadband.pdf

[roygbiv 0]

Was looking into this myself recently but could find no definitive answer.

Problem with that report is the date. LEDs have increased in output

dramatically since then. It looks like the technology is improving so fast

that the safety committees can't keep up.

[mr.surveillance 0]

I think all is fine unless you stare at the leds for a prolonged time. I used to make IR flashlights for use with night vision, you could damage the image intensifier if you pointed the IR flashlight at it too much, especially at close range.

 

Don't stare at the light, whether you can see it or not.

 

This is fairly old:

Infrared Light and Eye Safety:

In principle there could be danger for the eye, because infrared light is not registered by the eye, and thus the pupil won't close in order to protect the retina from bright IR light sources. This is the same situation as with UV light, which will cause snow blindness eventually, but in contrast to UV light, IR light contains much less harmful energy due to its longer wavelength.