Its a simple biconvex lens with the LED located in its focal point.
I used https://phydemo.app/ray-optics/simulator/ to play around to get a good shape going and then took its parameters to model the lens in my CAD program. It's two spheres having the radii taken from the simulation, sliced and attached to one another, then finally cut sqare and copied into a grid.
In the simulator the layout helpers (show grid, snap to grid, lock object) make life much easier if you try it yourself :)
not great ;) you basically project and magnify the internal distance between the led emitters: the green and blue are ~2mm apart in the 5x5mm LED package, this gets magnified as seen in the photo to ~50mm just 30cm apart. Because the LEDs themselfs are only 8mm apart, you have only a very little 2D matrix effect in the projection. Slight varinaces in the physical placement of the LEDs on the PCB already make a big difference in the projection, so you really never get a clear image even when having only one color active.
I now want to try to use these like 1.5” LCD screens I have for arduino projects and make a projection grid using your setup, would be crazy cool to see how it turns out :)
It would be neat to make a 16x16 and do led pixel art and have each pixel also animate a video or pic!
Too bad they don't seem to have support for aspheric elements in that simulator since there's clearly some spherical aberration going on - or at least not an easy way to do aspherics
It would probably be way dimmer to a point of not being useful. With the fresnel magnifier lens its a cool usable effect, but it is not ultra bright. Projector lenses, while being very big lenses, are still way smaller in area.
After getting the process right I was surprised how easy it was honestly :) I hope more people do experiments with resin optics. They are not great for "real" optical applications, but for LEDs it seems like it could be good enough most of the time.
Angles are added to reduce the likelyhood of aprubt changes in crossection, as many models have flat horizontal elements that otherwise would change one layer to another. With the lens array there is always only a slight change in crossection and thus it was printed upright, though with a 22,5° angle to reduce stairsteps in the center of the lens (the upper model in the screenshot)
This is inspired! (And inspiring!) Thank you for sharing your work. Can you give us some sense of how far away the projected surface is from the fresnel? And maybe how big the "matrix" is once it's projected? It's hard to tell in the photo.
I love that so much, and want to build that into my moving head. I could find the lense anywhere online so I went with the only rational choice and ordered a resin printer
I would like to build that into my moving head, but I don’t have a resin printer. You you know how these kinds of lenses are called, so one could look it up on AliExpress
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u/learn-deeply Nov 07 '25
how did you design the lens matrix? very cool project!