# Formula for lens periscope

I want to build a periscope.

To my great surprise even after intense googling I could find little relevant information about periscopes anywhere on the internet.

Let's say I want to build a periscope with height h, apparent height h1, diameter d and viewing angle v. What other variables should I define for a periscope?

Source: Wikipedia.

I am looking for a formula/manual/recipe for calculating the lenses and distances as well as any practical advice on building a DIY periscope.

Thanks.

• I think u don't actually require a lens for DIY periscope it will work fine without lens, i had made one 4 my bro without any lens – Vishnu JK Sep 16 '16 at 17:46

What you are trying to do is build the combination is a terrestrial refracting telescope and a periscope.

As the design of the periscope is straight forward so you need to look up terrestrial refracting telescope to get some idea of the linear dimensions between lenses and the focal length of the lenses. There is some simple theory given at this website.

A search of the internet will give you construction details and suggestions for dimensions.

• would it be possible to build a reflecting periscope (using mirrors instead of lenses)? – daniel.sedlacek Sep 9 '16 at 7:02
• If you do not want any magnification then you can use just mirrors or prisms. – Farcher Sep 9 '16 at 7:05
• no magnification is required but I want a large viewing angle, is it the same thing or something else? – daniel.sedlacek Sep 9 '16 at 7:12
• The longer the periscope the smaller will be the viewing angle. The larger The large the aperture the larger the viewing angle. – Farcher Sep 9 '16 at 7:26
• I think that a submarine periscope has a few lenses as well as some prisms inside it? – Farcher Sep 13 '16 at 12:53

Assuming the two prisms are planar reflectors, there's no significant effect from them. If you do your refractor-telescope calculations by measuring the distances along the center of the light path, including the right angle bends, it should all work out. Then you put in the right-angle, planar reflectors (prisms or mirrors) and get the direction you want as an effect independent from magnification and focus. The only other issue of the reflectors is their width relative to the angle of view you want to get. But again, this is independent of the right angles - it's still just distance and width of the tube.

you can get a surface silvered mirror from an old slr camera, as the reflex mirrors are always surface silvered otherwise you get 2 reflections, one from the surface of the glass, and one from the silver. I suppose, if you can be bothered, you could try making your own mirror by vacuum deposition....

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