making my own telescope type magnifiers?

I've been looking to buy head worn telescope type magnifiers because the Opti-Visor and their ilk all bug my eyes. The optometrist said this is because of two reasons in my case. First is that they don't correct my astigmatism and second because the spacing of the lenses doesn't match the spacing of my eyes. The least expensive of the head worn magnifiers I have found so far is close to $400.00 US. And there appears to be no upper limit in price. So, I'm thinking that by using the Edmunds book "Popular Optics" for the math and design ideas, and buying surplus coated lenses I can make my own. Any suggestions? Thanks, Eric R Snow

Reply to
Eric R Snow
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The ones I've seen for the handicapped used polycarbonate plates in regular glasses frames that the lenses screwed into, probably had some focussing built into them. Shouldn't be that hard to gen up, given the availability of a spare frame or two.

You've got some other options, you could go with jeweler's loupes mounted on glasses, which should fix your eye spacing problem, or one of those large magnifier lights on a parallelogram fixture. Microscope with a TV camera if you need more magnification.

As an aside, I've got severe astigmatism and have never had troubles with my Opti-Visor, even with the supplementary lenses attached. Are you expecting the Opti-Visor to correct your astigmatism without glasses? I've always used mine with my glasses.

Stan

Reply to
stans4

Reply to
joelblatt

No Stan, I don't expect the magnifiers to correct the asigmatism. They need to be mounted after the egeglass lenses. Maybe just splitting an optivisor lens will work. Eric

Reply to
Eric R Snow

Greetings Joe, I am not expecting the lenses to correct for astigmatism. I want to look through the magnifiers mounted after my eyeglasses. My astigmatism is at an angle to the vertical. I thought that this was almost always the case. It's easy to see the correction by holding the glasses in direct sunlight and looking at the image projected on the ground. And each eye is off at a different angle. Which I also thought was the most common. Thanks for the modified opti-visor idea. It might just be the best and cheapest. Eric

Reply to
Eric R Snow

The advantage to the little telescopes is greater standoff distance. A simple magnifier works simply by enabling you to focus with your face closer to the work. With a 5X simple magnifier, your eye is about

2" from the work. A 5X binocular or telescope operates at longer standoff distances up to infinity. The little headmounted binocs are heavier than a simple opti-visor. They're great if you need the standoff distance, like a dentist or surgeon might. If you can get close to the work then the simple magnifier is lighter, much cheaper and does the job.
Reply to
Don Foreman

I have a pair of welding goggles, I modified to take

37mm camera close-up filters. Cut 2 pieces of plastic same size as the goggle filter. Bored a 37mm hole in each, & screwed in a 37mm-37mm adapter so I had aluminum threads to screw the filters into. I had 2 sets of +1, +2, +4, +10 close-up filters. Stacking filters gives +1 to +17, except +8 & +9. Works OK for me, I don't mind the bug-eyed look. When anyone sees me wearing them, the get a good laugh.

Might be a good use for the scratched & unuseable face shields that seem to accumulate.

Reply to
Gary A. Gorgen

A little-known secret is that a good optometrist can make you *anything* you want if you can describe it to him in his terms. I'm amazed that they never seem to solicit this kind of business. My opto has made me several pairs of specialized glasses over the years.

If you go in and tell him you want reading glasses and that you want the working distance to be 6", or whatever and you'd like to try the prescription with his trial lenses, he can do it. It helps to bring in a piece of work so you can look at it with the trial lenses and make sure you're getting what you want.

Reply to
Jim Stewart

Odds are that you're using the strongest of the visors and your eyes are a lot different in distance apart than the distance that the optivisor is set at which I'd suspect is about 60mm or so, the median of normal eye spacing. I'd take a Optivisor lens and respace it to see if that is the problem. The binocs are nothing more than Galiean telescopes, a positive lens for the objective and a negative lens of x shorter focal length, where x is the magnification desired, and spaced properly. Needless to say, larger diameter lenses make for a wider field of view but aberrations start to abound when you go too far. Astigmatism can be corrected with a 0 diopter lens with the correction for astigmatism at the exit pupil of the negative lens.

-- Why do penguins walk so far to get to their nesting grounds?

Reply to
Bob May

Thanks Don. Then it really may be best to just cut apart an Opti-Visor to make it adjustable for my eyes. Besides cheaper it's faster too. Eric

Reply to
Eric R Snow

Boy Jim, that seems like a great idea. More expensive but then I can get exactly what I want. ERS

Reply to
Eric R Snow

I am so happy with the "access glasses" (upside down bi-focals, with the mid range spot at the top of reading lenses) meant for data entry operators that my optometrist prescribed for me four years ago, that I asked him for exactly the same thing in full safety glasses, side shields and all. These new glasses reside at my workshop door beside the full face shield. Gerry :-)} London, Canada

Reply to
Gerald Miller

Hi Eric,

I stumbled across this site awhile back while looking for magnifiers:

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Their catalog has some pretty nifty looking stuff and it may give you some more ideas. I don't know anymore about them though, just what I saw/read in the pdf catalog...

Reply to
Leon Fisk

I realize it's way out of your price range, but check out the Zeiss surgical loupes. They use a prismatic rather than Galilean type magnifiction. This allows for higher magnification without additional weight or length.

I had a pair of these a few years ago and shopped around quite a bit. Zeiss seemingly defied the laws of physics as their lenses produce brighter, larger field of view, deeper depth of view and sharp to the edges of view more than any other loupe at any given magnification or focal length. ...even those costing more $$$ (Zeiss was about $1500 in 1999).

The ones on eBay for ~$300-500 (sold for dentistry, generally) are ok for the money. Certainly much better than Opti-visor.

Reply to
skuke

You can make a fine pair of your own "telescopes" with, say, pairs of achromats from

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(Anchor is what used to be the Edmund surplus operation,
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sells only costly commericial grades now).

What you want to make is not a telescope, but a long-working-distance microscope. Here are some optical principles involved in designing your own.

The working distance of any microscope is between 1 and 2 times the objective's focal length. So if you use, say, an dia=40mm f=150mm achromat for the objective, you can get a working distance (s0) of, say,

250mm or so. The image distance above the objective (s1) is then determined by the equation 1/s0 + 1/s1 = 1/f, for example, 375mm. So you have 250mm+375mm = 625mm ~= 2 ft from the object to the eyepiece.

Now that's a rather long set of eyeglasses, but you can choose lenses and working distances to fit your whims.

For the eyepieces you can use ordinary microscope eyepieces (decent cheap imports available on eBay) or you can make your own wide-field Plossl's from pairs of the same achromat lenses. A pair of 40mm x 150mm achromats will get you about a 75mm focal length (3.4X) and whopping wide field and eye relief.

So you'd need 3 achromats at about $20/each for each eye.

That's the optics ... the mounting in tubes is up to your metalworking abilities.

Reply to
Richard J Kinch

A bit heavy for eye worn but take the smallest pair of prism binoculars that you can find. Remove one object glass (the big front lens) carefully noting which is the inside side.

Mount this lens just in front but not touching the other object glass. What was the inside face of this extra lens should this time face outwards.

You've now got a well corrected telescopic magnifier. The two object glasses make a 1:1 image at the eyepiece focal plane. The magnification will depend on the eyepiece fitted - usually about 10:1. The working distance depends on the size of the parent binocular - about 3" for a small binocular, about 7" for a larger one.

You can do the same trick with opera glasses but the magnification will be low and the field of view small.

Jim

Reply to
vj

Won't that give an inverted image?

Reply to
Don Foreman

Not if you add a relay lens, as in a rifle scope, or a prism, as in binoculars.

Reply to
Richard J Kinch

Perhaps I missed those details in your previous post describing "how to do it". Another nitpick: I thought binocs use a pair of Porro (or similar) prisms per tube.

I think the lenses my dentist uses are more like field glasses or opera glasses: an objective and a negative (diverging) eyepiece. No relay lenses or prisms. They are very small, short (about 25 to 30 mm) and lightweight. They clip-mount to his spectacles. They offer arm's-length working distance with magnifications of 2X and

3.5X.
Reply to
Don Foreman

That would be a Galilean telescope. Very simple to make (which is why Galileo used it) but very narrow field of view and lots of aberrations. I suppose a dentist doesn't need a wide field of view to work on a tooth, but a machinist typically needs to see more of what he is working on.

I used to go to a dentist who used a flip-visor magnifier, but the working distance was rather up front and personal. I imagine the only benefit to the scopes is getting more working distance, so his face isn't right in yours.

Reply to
Richard J Kinch

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