The finished product
The projector has 4 main components:
1. A 3D printed base to hold the flashlight upright
2. Flashlight (Glarylight XHP70.2, ~£20, USB-C rechargeable)
3. The barrel, which is also 3D printed. This tube fits between the flashlight and the lens, with a slot for the slides/film, holding it a precise distance from the back of the lens.
4. A camera lens. I've found the 50mm canon to work well.
The flashlight has a built in diffuser lens, which can focus the light into a straight, extremely bright beam. The beam passes through the film, and then the camera lens. These lenses usually take light from a wide area (the world) and focus it into a small area (the camera's sensor). We're simply reversing that process here. Keep scrolling for the full schematic.
Assembly
3D printed parts designed in openscad. I also made a cap that can be twisted on instead of the lens to turn the assembly into a lamp rather than a projector.
Printing the base
Printing the barrel
Printing the cap
Here is a white version in lamp mode that I made as a present for a friend
i decided to paint it
The pattern etched into it is a “Girih”, an ancient islamic geometric pattern meaning “knot” in Persian. Girihs adorn many of the holiest sites in the world, including Al Aqsa Mosque in Palestine, Topkapi Palace in Istanbul, Alhambra in Spain, the Tomb of Hafez in Iran.
This particular design is from the best kebab shop in London, Antepliler Kebab, Haringey N4 1HA.
While the original version of this projector uses mounted slides, I also made a variant that takes film directly. It has two thin slits on either side and an interior support rail that guides the film through. This way, if you shoot on positive film (e.g. Ektachrome E100), you can put the film strip directly into the projector, and pull it through slowly to create a slide show.
The Canon 50mm lens was given to me by the kind folks at Nicholas Cameras in Camden, go check them out! The top of the barrel is a Canon FD mount, so should fit a variety of lenses that use the same standard. I also made a variant that fits Olympus lenses; all STL files are available on github if you want to print your own.