Huygens sketched a lantern that threw painted slides on a wall and then half-disowned it as a toy for scaring people. Kircher printed a similar box. The photographic slide projector of the nineteenth century is the same conjugate: object outside the focal length, real inverted image on a screen.
One convex lens is enough for the idea. This bench leaves the “slide” as a luminous object and lets you slide the lens until the screen sharpens.