35 mm Slide Viewer, customizable

Many of us keep a large number of 35 mm film slides from a distant past. There were some simple and inexpensive gadgets to see the slides without a projector. Today is difficult to get one. Online you can find some slide viewers far more complex, heavy and expensive. For this reason I designed my own slide viewer and built it using a small lens from my junk box. It is likely that you can get a different lens and for this reason my design is customizable.

You can use a lens savaged from a small magnifying glass or a loupe or a scraped optical device (mine came from a cheap ramsden eyepiece that belonged to a small telescope). The lens should have a focal length between 45 and 65 mm. The focal length is the distance between the lens and an object to see it well focused. As for the diameter anything from 10 to 38 mm can be used.

The viewer consists of three pieces: a body, the back piece and the lens holder or focuser. The back piece is always the same. There are two focusers, one with a diameter of 25 mm, for lenses from 10 to 23 mm and another with a 40 mm diameter to be used with lenses from 24 mm to 38mm. In the focuser openscad file you have to put the appropriate diameter. Find the focuser position to see a slide well defined before glueing it to the body piece. For the body you have to choose one depending of your lens focal length and the focuser diameter. The diffuser can be made with a piece of a very smooth translucent plastic. Rigid plastics will be difficult to insert in the back piece. A simple solution is to cut a piece of plastic from the side of a juice bottle, but it is not smooth enough and you have to add a piece of tracing paper glued to the plastic in the interior face.

Don't use cyanoacrylate (super glue) to bind the pieces, its vapors may fog your lens (plastic or glass). If you use silicone adhesive it will not be too difficult to disassemble the viewer for maintenance. Of course you can use epoxy, but it will be very difficult to disassemble the viewer.

Have fun with the viewer!