I am working on a project where I need to project a single image onto an object, Originally I was looking at the digital projector route but due to cost and complexity this has been ruled out. I found a company where I can get digital images on to 35mm film held in glass and in a slide which is very cheap at only £4.50.

Now I need to design the optics of the projector and am unsure about this mainly because I'm unsure where I can get the lenses (and which ones I need) from to see what limitations there are in terms of the focal length, size of lens, projection size that I can get , I have tried searching online but I think I am using the wrong terms for finding what I'm after as I have only been able to find glasses (spectacles), binoculars, telescope, camera, lenses as well as the massively expensive digital projector lenses at over $1000.

I would like to find lenses which are like camera ones where they have a threaded fitting so I can easily and accurately mount them, as well as being fairly compact in size realistically the projected image will only be going less than 60cm to the object, if you know of anything that will work for this it would be great?

  • What's the goal: are you trying to take a photograph of the object with the projected image, or is it a longer-term display? – crunch May 14 '15 at 9:11
  • yes a photo or video will be taken after the image has been projected i am aware of digipod and light blaster however i am more interested in the scientific and mathematical uses rather than photography, i thought this would be best place to ask for questions on lenses. – user39772 May 14 '15 at 9:20
  • I was going to suggest light blaster. At a guess, have a look at ebay. Camera lenses with an M42 mount use a threaded (screw) fitting. Try looking for a 50mm or 35mm lens. – crunch May 14 '15 at 10:17
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    Why is it necessary to build your own projector? You could get a 35mm slide projector off eBay, even a nice one should cost under $500. – David Rouse May 14 '15 at 12:57
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    I'm voting to close this question as off-topic because the OP stated in a comment: "... i am more interested in the scientific and mathematical uses rather than photography," – Michael C Jun 4 '17 at 2:01

I have found Edmund Optics/Scientific to be a good source of different types, quality, and grades of optical supplies for prototyping.

I have also used LEGO™ blocks for building various types of cheap lens mounts and component assemblies. The parts are standard, and can be modified for any kind of custom piece.

Sugru™ is another wonderful material for prototyping which turns into a dimensionally stable stiff rubber.

Glass transparency precision mounts in different formats is available under the brand Gepe™ including hi-heat resistant plastic.

Have fun and good luck.


All you need is an enlarger lens. Procure a 50mm enlarger lens on line. For your project, it need not be an enlarger lens, any 50mm camera lens will do this trick. Your problem is mounting the lens. You light the slide using a bright lamp situated behind it. To achieve uniform lighting on the slide, use milk glass commonly available at any glass (window) shop. If you need more help just tells us. Why 50mm? We mount a projection lens with a focal length about equal to the diagonal measure of the slide. This gives a projected image with uniform brightness. Any shorter and the projected image will be vignette. You can use a longer lens but the distance slide to projected image will likely become difficult for you. Do find a 50mm lens. Old enlarger lenses are plentiful.

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