ligra is an open source image projector build from scratch and based off of flea market parts by Jana Marie Hemsing. ligra is not necessarily a PCB-project nor a single thing, but rather an idea of how to design your own image-projection system. It is an introduction on how to create light-graffiti, how to share messages at large.

It’s not strictly a Gobo, rather a way of building a system that may resemble one, but may also resemble a video projector or an abstract source of art.

I have mostly used it with 2D printed stencils, usually used with so called “overhead projectors”, one can of course also use metal-stencils, coloured effect-foils, 3D printed stencils and even LCDs, or really anything that may project an image. Get creative!

ligra essentially functions as a backwards camera, well, most projectors do. This becomes more visible when we talk about its inner workings, it’s heart and most fixed element is the lens, a Canon FD lens in our case. But instead of using it to project and image onto a 35mm film slide, we will project light through a ruffly 35mm film slide-sized, image forming medium (i.e. a 2D printed stencil). This light will enter the lens from the back, projecting an image onto a scene with the properties of the lens (focal length, aperture and focus). Given the quality of even early lenses, we can expect some sharp and crisp projections.

See the details and files on GitHub.