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What you want is a stage/DJ light which takes gobos, and the right gobo. For example: https://www.fullcompass.com/prod/212208-rosco-81115-glass-go...

The light wouldn't be on the ground but above it, projecting down.

Edit: I should add, the gobo would need to be glass, as metal ones would have to interrupt the ring to support it. If the one linked above doesn't work for you, this place looks like it could custom make one to your spec and has a number of supported lamps under the "Gobo Size" drop-down. Explain what you need and they look like they can help you figure it out.

You may also be able find a good deal on lighting in one of the usual marketplaces, but just confirm the fit with the gobo maker so you know what you're looking for.

Thanks, I should have stressed that mounting bulky equipment is not an option. The challenge for this is that device should be relatively small (something you can easily carry in a backback) and work from batteries. The place where it'll be used is not a place you can control over (i.e. ask for electricity plug or mount something on the ceiling or the wall etc).

From my understanding, the 5mw limit doesn't necessarily apply when a laser is scanned and has appropriate interlocks. For example the valve lighthouse (VR base station) is classified as class 1, but contains class 3 laser sources.

I think the scanning laser path is more likely to be what you want. Projection-based solutions will probably end up being a lot larger (and more power hungry), as I think you'd need a reasonable amount of quality optics to make anything resembling a sharp line at 1m distance from anything described as a 'small' gadget.

Thanks for the comment. Scanning laser path is something like LaserCube is offering, right? I talked to them and they warned that it's a class 4 laser and shouldn't be used anywhere accesible to people for safety.

So yes, basically what I'm looking at the moment is a way to verify the intuition about if that's even possible. Or what minimum size/power is needed to do that ring. And it's either a lot of DIY that are beyound my skills and time at the moment, or some good simulation software. I'm playing with Blender + LuxRender, but it's still too slow on my M1 and it's basically bruteforcing ideas instead of proper design.

> LaserCube

Hmm, that looks like a 2D galvo scanner. I was thinking more like a laser pointer and a mirror attached to a motor.

> what I'm looking at the moment is a way to verify the intuition about if that's even possible

You just have to build it! It's definitely possible, and the only question I have is the power of laser needed to be visible in your environment for a given circle size, and a simulation will not tell you that.

The two general ways of doing this would be [A] projection and [B] scanning with a laser.

Projector optics combined with a ring-mask (a "gobo") are a known thing in stage lighting and/or theatere. Getting them that tiny will be a challenge however.

If you are truly invested I'd suggest looking into how very small "pocket" projectors do this, maybe you could even salvage the optics out of a broken one.

Thanks! Can you provide an example of what you mean by pocket projectors? Author of the video I posted in comment actually built the table top projector with this curved mirrors. The closest thing I found at the moment.

The other comment mentions a gobo which is the industrial solution to this. But I am confused: you want to project a ring? There are all sorts of arrangements to achieve this but really you want a bright led, a collimated lens, and a mask. Or just use a gobo, or a light projector showing an image of a ring.

Right, ring is the right word :) (well, in the more perfect setup, I'd love to have more complex but based on the ring shapes, but ring would be a good a start).

LED+collimated lens and a mask sounds OK, but two questions: a) probably also need mirror, right? the device should be small and placed on the floor itself (you can't leave it or mount). b) mask is for, well, masking out the light from the center of the circle? Part of the challenge here is to make the ring as bright as possible (could be used in pretty bright environments), so ideally no light coming out from the optic system should be wasted (masked). Again, not sure it's even possible.

I'd bet there's a professional lighting product that'll do that. Something like the lights they use to project arrows on the floor at IKEA. I don't know enough about that domain to know what they're called, sorry.

There are, but they don't have constraints of being small, mobile and staying on the floor.

Here is one remotely similar stuff, but it's too bulky and more complex (I need static ring basically and gadget that can fit the backpack) https://www.youtube.com/watch?v=xXl3F5AoeQU

Collimate a LED light, and bounce it off a conical mirror or through a conical lens, depending on if you want to have the LED pointing up or down which depends on the size constraints.

You could maybe take a look at this video if you wanted more complex shapes.

https://youtu.be/wk67eGXtbIw

Thanks! I loved that video of Steve, and tried to find how can I actually design such lens like olympic rings myself, but ended nowhere atm.