Potential Limelight Safety Issue 2023

OK, thanks for the input. Good thing to consider.

This is now my favorite quote and the best thing I have heard in FRC


If you are concerned that the lights on a robot pose a safety risk, I refer you to R203, specifically part m in the blue box:

high intensity light sources used on the ROBOT (e.g. superbrightLED sources marketed as ‘military grade’ or ‘self-defense’) may only be illuminated for a brief time while targeting and may need to be shrouded to prevent any exposure to participants. Complaints about the use of such light sources will be followed by re-inspection and possible disablement of the device.

Ohh goodie… this discussion again…


My team has always used the least light possible so we know many other teams are unnecessarily blasting their LEDs.

Using a recent PhotonVision Beta on a LL2+ I can turn the camera exposure to about 2.5, camera brightness 6 and LED brightness 20. The full cone target is shown and I can almost look at the LEDs.

In case anyone is wondering as I did and hasn’t been able to test - that diamond pattern on the new tape is very distinctive and blur will be needed to “erase” it. The aluminum pole is NOT retroreflective in any way like the tape. If the LED brightness is turned way up (too far up) you get a thin green vertical line from the center of the pole. The line is gone with reasonably lower brightness.

I remember the LL2+ software allows turning off some of the LEDs. We’ll be doing that. The horizontal range of the camera is reduced somewhat but we expect to be aimed almost straight on and my experiment now shows almost no difference with all the LEDS and half of them. Apparently older LL require that you cover the LEDs to turn them down or off.

We’ll try the light shield mentioned above, too.


You can aim to the middle row tape also while scoring on the top row, just like in 2019 there was tape only on the lower level.

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to be honest didnt think about this till I saw your scientific diagram which makes things very difficult with the amount of cone nodes. I am a little confused why this may have not been thought of before realeasing the game. They may just change the material of the panel so drivers can see better when limelight is in their eyes.


So was able to find an exposure limit of 1candela/cm2 for NIR before there’s any risk. SourceLinked From
I was not sure what light intensity the IR would be, so I assumed it would not exceed the limelight, which is 400lumens with FOV of 60x50deg.
At 4’, that creates a total area of 1944in2 (929cm2)
400lumen/12.57 => 31.8 candela
So 4’ light intensity is 0.034can/cm2…far below any risk threshold.
Intensity is square of the distance, so at 1’ (1/4th distance=16x intensity), still below threshold at 0.54can/cm2. At 6inches, you just start to get to a point where excessive exposure would begin to do damage to retina and iris.

If using FIR, exposure limits change some.


Not going to happen - do you have any idea how expensive that would be? There is no need to be shining a light up towards the drivers eyes. All vision targets are low, so shine the light only where you really need it. Problem solved!

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This is a topic that has come up a few times. I am still concussed, so am unable to find the specific rule, but in the past, safety glasses needed to be clear to count as safety glasses.

One thing that could help though would be this. We have used it in the past to great effect. This combined with a good downward angle has the possibility to solve the problem.

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wear safety glasses (only ANSI-approved, UL Listed, CE EN166 rated, AS/NZS certified, or
CSA rated non-shaded) while in and around the playing FIELD and in the pit area. Lightly tinted
lenses are permitted provided eyes are clearly visible to others, but reflective lenses are
prohibited. Accommodations will be made for participants that require tinted safety glasses. The
only exception is for teams in their first 10 minutes of their load in and for the first 10 minutes
pits are open each day of the event as long as they’re not working on the ROBOT or setting up
their pit.


Good to know. Thanks for the tip

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@RPostWVU Thank you. The clickbait title to this thread made me think it was some kind of joke. But clearly some of the posters are actually worried about permanent eye damage.

As a trained Laser Safety Officer (LSO). I can assure everybody there is no risk of permanent damage to your eyesight from a Limelight used normally. It is not a laser. Yes, if you stick your face right up to it and stare you’re getting close to risk.

It can flash blind you so that you see spots in your vision for several seconds to minutes afterward. Not permanent. Yes, it can trigger the startle response. It probably would not in this situation, but a bright light suddenly when you’re not expecting it can scare the bejesus out of you and cause an involuntary reaction causing you to drive your robot into a wall. It can also trigger a pain response. Your eyes don’t actually have heat based pain sensors. Instead they use light brightness as a proxy. Most people feel pain from green far before there is any real risk. The eye is extra sensitive in the green region of the spectrum so these issues are magnified there.

You can also put sunglasses on the limelight itself to decrease the light level.


I don’t know if anyone has said this already but would it be possible to wear green light blocking glasses? Sun glasses would block out too much light and make it hard to see so I feel like these are the best option.

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I’m surprised no one has mentioned this yet, but it’s pretty simple to turn off the limelight’s lights when vision tracking isn’t needed. (Just turn them on only when the vision tracking button is pressed.) This doesn’t help the fact that it may blind people behind the driver station when aligning with the poles though.

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Are there IR blocking glasses that wouldn’t alter the way you view the field (i.e. make it darker, change the colors of everything, etc.)?

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The issue is the only time you need the lights on is when the robot is facing the drivers right in front of the alliance stations. It can be off all the other times… Ya know, when it’s not facing the drivers and thus not flashing them. Just like why put the vision objects right there. Just bad placement and not enough testing

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FWIW, I think enforcement of this rule varies. I’m very used to seeing team members and volunteers at events who look like they’re wearing sunglasses. But perhaps exemptions have been granted for these folks as per the rule.


I’d be surprised if the Volunteering Parents at the pit entrance can differentiate “ANSI-approved, UL Listed, CE EN166 rated, AS/NZS certified, or
CSA rated non-shaded” safety glasses from just random safety glasses. If your eyes are covered they are usually content

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