3

I am creating a device which uses IR LEDs to illuminate the human eye, while an IR camera records the pupil dilation.

From my research, I see that there are two standards which are related to the wavelengths (950nm) of my IR LED. These are:

  1. "IEC 62471:2006 Photobiological safety of lamps and lamp systems"
  2. "IEC 60825-1 SAFETY OF LASER PRODUCTS - PART 1: EQUIPMENT CLASSIFICATION AND REQUIREMENTS"

If I use the 1st standard the equation is:

enter image description here

  • My exposure limit is: 18000.7^-0.75 = 4182.63 W/m²
  • And the 40 IR LEDs that I have produce: 40 * 0.011W/sr/0.120² = 30.55 W/m² (at a distance of 120mm)

Therefore, this is well below the limit.

But if I follow Standard 2 for "Maximum permissible exposure (MPE) at the cornea for direct exposure to laser radiation", the equation is this:

enter image description here

where

enter image description here

and C6 = 1 (I am assuming from reading the standard)

  • MPE = 18*7^(0.75)10^(0.002(950-700)) = 244.96 J/m² = 24.49 mJ/cm²
  • Q = 24.49π(0.35²) = 9.427 mJ (Assuming worse case: 7mm pupil)
  • Power Φ = 9.427 / 7 sec = 1.346 mW

and the total radiant flux of 1 of the LEDs is: 35 mW -> This is obviously higher than my calculated limit (assuming that my calculations were correct)

Therefore, my question is simply: Which of these standards does a IR LED (or array of IR LEDs) need to satisfy?

Thank you.

SamGibson
  • 17,870
  • 5
  • 40
  • 59
Scott Bruton
  • 53
  • 5
  • 1
    It seems quite obvious to me that you have a lamp, not a laser. You'd know if you had a laser because the light would only go in a straight line, not in every direction. – user253751 Jul 09 '20 at 13:56
  • 1
    @user253751 No, lasers are coherent, but not necessarily collimated. Diode lasers, for example produce a raw beam with quite a lot of divergence. You need lenses to collimate the beam. – DKNguyen Jul 09 '20 at 14:03
  • @user253751, the datasheet of the IR LED, SFH4243 from OSRAM states: "Depending on the mode of operation, these devices emit highly concentrated non visible infrared light which can be hazardous to the human eye. Products which incorporate these devices have to follow the safety precautions given in IEC 60825-1 and IEC 62471."

    Hence why I looked at these two standards to begin with

     – Scott Bruton Jul 09 '20 at 14:14
  • 1
    I'm on my way out and don't have time to go through the ANSI standard right now, but from memory 1.4mW is very nearly the retina limit for a 1000 nm, point source being collimated into the retina. You have an extended source, which will put vastly less power per area onto the retina (since it will not be focused by the cornea) and so you should be able to use much higher power safely. Do you have a copy of Z136.1? It has a table of permissible exposures for extended sources. – user1850479 Jul 09 '20 at 14:24
  • Hey @user1850479 , Thank you so much for your response. I will have to look for the Z136.1 tables and research them.

    I can find 2 infosheets for the SFH4243-Z. One difference between them. 1: These devices emit highly concentrated non visible infrared light which can be hazardous to the human eye and have to follow IEC 60825-1 and IEC 62471. 2: has ommited this and states: "no endangerment to the eye exists from these devices.

    This is quite confusing :/

    Anyways, the half beam of the LED is ±60°. Would this be classified as a laser still? And would I need to follow IEC 60825?

     – Scott Bruton Jul 10 '20 at 09:58
  • @user1850479

    To give some context to this. Here are the datasheets of the IR-LED. (Remember, I will have 40 of them pointed towards the eye, in a square matrix of around 30 x 30 mm)

    Here are the datasheets:

    1. https://4donline.ihs.com/images/VipMasterIC/IC/OSOS/OSOS-S-A0002483803/OSOS-S-A0002483803-1.pdf?hkey=52A5661711E402568146F3353EA87419

    2. https://www.ttiinc.com/content/dam/ttiinc/manufacturers/osram/pdf/SFH4243-Datasheet.pdf

     – Scott Bruton Jul 10 '20 at 10:00
  • Related question: Dangers of IR LED – maxschlepzig Feb 18 '22 at 19:09

1 Answers1

1

No, IR LEDs (nor any LED for that matter) are not classified as a lasers. The only diodes that are considered lasers are laser diodes.

IEC 60825-1 had previously included LEDs of any type, thus not necessarily classifying them as lasers, but making them the same as lasers in regards to that safety standard. This was done as a temporary measure until a new spec that was generalized to LEDs and other "lamp" light sources could be finished.

With the removal of IEC 62471:2006, LEDs were removed from the IEC 60825-1 standard, which once again only applies to actual laser sources. You do not need to worry about anything in IEC 60825-1 for IR LEDs, or any other non-laser LED. You only need to worry about IEC 62471. I think whoever wrote those datasheets is unaware of this, or is simply trying to cover every potential vector to some kind of liability litigation. IEC 62471 explicitly excludes all lasers from the standard, so a single device cannot fall under both specifications, they are mutually exclusive. Simply put, those LED datasheets are incorrect.

Vishay has a good document on this, including a nice table on the very first page that shows which standards what photon emitting devices do and do not fall under.

It should be noted that IR LEDs have their own specific requirements in the IEC 62471 standard.

From the Vishay pdf:

IEC 62471 AND EU DIRECTIVE 2006/25/EC

For all applications the standard IEC 62471 is applicable. This standard for incoherent sources replaces for LEDs the laser standard IEC DIN EN 60825-1.

In case of IR - Emitters the dominating limit is the cornea/lens risk in the wavelength range from 780 nm to 3000 nm. This limits the irradiance to Ee = 100 W/m2 which is expressed as intensity a value of Ie = 4 W/sr with the measurement condition of that standard with 0.2 m distance in mind (Ie = Ee x r2). Evaluating the other limiting conditions as the thermal retinal risk and blue light hazard result in not limiting higher values for wavelengths λ > 850 nm and therefore are not to be taken into account. Only for λ = 830 nm a little reduction to Ie = 3.77 W/sr is given by the thermal risk.

metacollin
  • 28,520
  • 4
  • 68
  • 120