Eye pain/ache when operating my laser projector

[s4y]

Hi all, first post here! I recently got my first ILDA laser, a used Goldenstar D-RGB1000 with an upgraded scanner, and I've been having loads of fun writing code to drive it and do audio-reactive visuals. I have a few questions, but one is front of mind:

When the laser is in use, I feel a dull eye ache that persists until some amount of time after I shut it down. It's faint enough that it could all be in my head, but consistent enough that I'm suspicious. (I've forgotten about it a few times and not used the laser for a few weeks, then powered it up and, bam, "why do my eyes feel funny?) I am not looking into the beam, a reflection of the beam, etc . My best guess would be some kind of non-visible radiation like IR — is anything like that known to happen, especially for inexpensive or questionable laser projectors?

I'm probably going to hold off on using it more until I understand what's happening.

[swamidog]

Hi all, first post here! I recently got my first ILDA laser, a used Goldenstar D-RGB1000 with an upgraded scanner, and I've been having loads of fun writing code to drive it and do audio-reactive visuals. I have a few questions, but one is front of mind:

When the laser is in use, I feel a dull eye ache that persists until some amount of time after I shut it down. It's faint enough that it could all be in my head, but consistent enough that I'm suspicious. (I've forgotten about it a few times and not used the laser for a few weeks, then powered it up and, bam, "why do my eyes feel funny?) I am not looking into the beam, a reflection of the beam, etc . My best guess would be some kind of non-visible radiation like IR — is anything like that known to happen, especially for inexpensive or questionable laser projectors?

I'm probably going to hold off on using it more until I understand what's happening.

you're just getting eyestrain from the brightness of the reflected light. try turning the laser output down or projecting onto a dark surface.

[james]

"writing code to drive it"

I'm intrigued. Do tell.

[NobleGas]

you're just getting eyestrain from the brightness of the reflected light. try turning the laser output down or projecting onto a dark surface.

My thoughts as well.

[buffo]

When the laser is in use, I feel a dull eye ache that persists until some amount of time after I shut it down.

As several people have posted above, it's probably due to the high brightness / high contrast of the laser. You can try reducing the output power, increasing the ambient light level in the room, or displaying on a dark surface that is less reflective.

Another possible cause is image flicker. If you are trying to scan a very complicated frame (more than about 1200 points or so), the image will begin to flicker as your frame rate drops. Some people are particularly sensitive to this sort of flickering and in those people it's common for them to get a headache after watching a show with a low frame rate.

If you're old enough to remember the Commodore Amiga line of computers, you might remember that the high-resolution graphics modes of the early Amiga computers all used an interlaced video signal which produced a pronounced flicker on a standard monitor. (Unlike TVs of the time which used long-persistence phosphor coatings, a 60 Hz CRT monitor uses short-persistence phosphors; the resulting flicker as alternating frames are displayed is readily apparent to the human eye.) That flickering would cause eye strain and headaches in some people just like a flickering laser show will.

My best guess would be some kind of non-visible radiation like IR — is anything like that known to happen, especially for inexpensive or questionable laser projectors?

The laser sources in that projector are all direct-injection diode lasers, so no, there's no chance of any IR radiation showing up in the output. Not a bad guess though!

To be fair - even if the projector did contain an older DPSS laser that leaked lots of IR it still wouldn't be enough to cause pain simply from viewing the spot on the wall. Direct beam exposure is another matter, of course, but at that point the blindingly-bright visible portion would be just as bad.

I'm probably going to hold off on using it more until I understand what's happening.

I admire your concern for safety. But in this case you should be fine. Try increasing the light level in the room while turning down the projector power level. If you can also find a dark surface to use as your projection screen (something like a black bed sheet, for example), I think you'll find that the problem will go away.

By the way, Welcome to PhotonLexicon! Please tell us more about the software you've been working on. It sounds intriguing!

Adam