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  1. Manu Prakash says:

    Dear ..

    The current Foldscope kits we shipped provide a 150x and a 450x lens. The PLOS one paper we wrote – we described magnifications all the way upto 2000x. Magnification is inversely proportional to radius of the lens; and some of the parts/data we showed in the paper reach that magnification.

    We made a decision at the time of shipping to focus on the two above listed magnifications since we wanted the community to first start using the tool and learn the tricks. The smallest lenses for high magnification are extremely small and we would not have been able to scale the community to the size it is now (50,000 units in hands of people around the world).

    Here is the paper – if you want to add in high mag lenses. We provide all the parts in details. Finally, the next phase – we will also include high mag options as added modules to the base unit. The next phase will also include a focus locking option which allows for easy use of high mag lenses. So keep an eye; and also image with the 480x lens. When you add some digital zoom to it; you will be shocked to see what you can image (individual cilia and sub-cellular features).



    1. Paul Joseph says:

      Hey manu, I just realised that it isn’t possible for you to see the person who posted the post- Lol.
      I was reading your paper it was mentioned in many places that the foldscope can go upto 2000x, ergo the post.
      I thought that it would be possible to put the high mag lens over the low mag lens and possibly get a higher magnification as right now in school I am learning about ray optics and the fact that the effective magnification power of a compound microscope is the product of the individual powers of the lenses- I guess the foldscope doesn’t work like that!

  2. Matt.Rossi says:

    Manu, is it possible/practical to compound the foldscope using the high mag and regular lenses?

  3. Manu Prakash says:

    @matt: in a sense yes. The latest lenses we are developing are actually doublets or triplets (complex compound lenses); but they are not chained in the way you think about usual compound lens setup.

    In projection mode; we have also used a hand lens to actually further magnify a real image. New version of the device will also allow for a more stable projection microscopy (which you can further expand by a eye loop)..



  4. Manu Prakash says:

    @paul: for a single lens imaging system; the effective magnification is inversely proportional to the radius. Spherical surface is just one example; but in this case mag ~ (n-1)/nr where r is the radius. For a sphere is radius 100 microns; refractive index of n=1.77; the magnification is 2180.

    You should dive into the geometrical derivations for these quantities – they are incredibly informative. See the table from our paper here:


    1. Paul Joseph says:

      @manu, thanks so much for taking your time in explaining how attain such high magnification, which has obviously stirred up a few questions in my mind;

      1. If you use a material with a higher refractive index (something like titanium dioxide or zinc oxide maybe?), wouldn’t you be able to theoretically be able to get an even higher magnification?
      2. What material do you currently use for the lenses in the foldscope?
      3. How are you able to fabricate such tiny lenses without any aberrations? Because even the tiniest spec of dust would ruin the image it produces right?

      I have one more doubt, why does the foldscope use ball lenses and not convex and concave lenses?
      -I’m sorry if the last one has a really obvious answer.

      thanks !

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