making my own telescope type magnifiers?

My dentist uses what look from catalog pictures like keplerian telescopes mounted in holes in plastic eyeglass lenses. He said that the magnification was 3.3X. The working distance seems to be about 9" to a foot. If I recall, he said that this cost something like $1,000, so I assume that the optics are quite good.

Joe Gwinn

Reply to
Joseph Gwinn
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I don't know how they work, but they certainly had good field of view and no evident aberrations. He specificially mentioned wide field of view as being very important to him. I looked thru them. Had a hard time giving them back!

Maybe there is a relay lens in there, but I don't know how they'd fit all that in a tube maybe 30mm long. There certainly were no prisms.

Reply to
Don Foreman

That is not much tube length for the optical function you describe, especially if Galilean. The length of any such instrument has to be at least several times the limiting aperture for adequate performance (that is, an f-number around 2 or more). What was the diameter, roughly speaking, of the objective lens in this 30mm tube?

You've got me curious now. Did you have any make or model type of information on these things? Or a Web link perhaps?

Reply to
Richard J Kinch

Answering my own question, is this the sort of thing you're describing:

A Galilean design:

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A Keplerian design:

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Reply to
Richard J Kinch

Answering myself again, here is a link to search eBay for"

(dental,dentist,medical,surgical) loup*

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I guess with these things, 10 degrees counts as "wide field" at 2.5X. Consider that ordinary binoculars would have about 20 degrees at that magnification.

Reply to
Richard J Kinch

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I dunno, Richard. He seems happy with them and they looked pretty good to me as well, though I think I'd find the weight annoying.

Reply to
Don Foreman

Easy enough to test. Roll a 1" diameter paper tube about 6" long. Hold it up to your eye and that tunnel view is about an (unmagnified) 10 degree field at its end.

At 2.5X one could theoretically have a comfortable 25 degree field, which would spread to 60 some degrees in your view.

Galileans scopes have a pronounced "keyhole" narrow-view effect by their nature. You're looking through a negative eyepiece and seeing a minified image of the objective lens aperture.

Reply to
Richard J Kinch

Some of the low vision aids are very interesting, too. A local optician specializes in them. She has about 50 different items in stock, and nothing was cheap. The most expensive are the TV/Monitor reading aids. I was looking for a cheap "C" mount macro lens for a viewer for my bench. I have plenty of NTSC color monitors and a couple cameras to repair.

Reply to
Michael A. Terrell

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