Wearable Optical Low Power Telescope

[mikeincousa]

I hope I am in the right place in the right forum. You look very newbie friendly.

I have multiple vision impairments. Compound optics help me see better near and far. I use a hand-held monocular for reading overhead signs in supermarkets, street signs, etc.

What I hope to do is build a simple Galleian telescope for say 15 to 50 feet.

With that I would like to fix it into a pair of eyeglass frames.

I have no prior experience building telescopes, but I do have some basic knowledge of optics from working with view and other cameras, as well as microscopes.

I think a thinner and shorter design will work better than longer one?

The ability to wear it is the main idea.

I have looked the basics for building a Gallean with two lenses.

But that is as far as I have gone.

So I first ask if what I want to do will work?

Then how do I specify the lenses, separations, etc.?

And last, any design references for such a project?

All thoughts and suggestions will be appreciated.

 

[Demonperformer]

Hi Mike and welcome to SGL.

That sounds like an interesting project, if you can pull it off.

My first thought is that there are glasses that have little loupes that can be swung down for close-up work (been trying to find them on the internet, but all the results I get are more high-tech than that simple design). I think the problem with anything that wasn't moveable like that would cause more problems than it solves. I think you would probably find it easier working with one lens than a whole telescope, something like the system an optician uses to test your eyes? On some kind of sliding system so it can be either out of line of sight for "normal" stuff and slid into place for reading signs?

Not sure how much this helps ... maybe we have some opticians on the forum who can say if this would work in theory and you could then start working on the practicalities?

[Tommohawk]

Hi Mike. You could construct your own spectacle mounted binocular telescope, but there are many such devices available off the shelf. I'm a hospital optometrist and have some catalogues some where. If you give me a while I'll send you some links.

Of course if you just want a project, I can give you some numbers if you like to make your own. The lenses aren't too much of an issue, (although oddly small lenses are more expensive as theyre non standard) but the mechanics might be. The priority is to keep it light otherwise it won't be wearable. 

It might help to know what condition you have. I work with AMD patients so am fairly familiar with low vision requirements. Send me a PM if you prefer. 

[ollypenrice]

Interesting! At least two manufacturers are now offering low power Gallilean binoculars and, I think, you can buy a head adapter for them. I've tried the Vixens and found them very appealing.

https://www.firstlightoptics.com/vixen-binoculars/vixen-sg21x42-widefield-binoculars.html

Olly

[Tommohawk]

Right - back on the PC now and have had a chance to look things up.

Mike - a lot will depend on what you want to achieve. Primarily, do you want to use this device whilst stationery, eg for watching TV, or are you hoping to be able to walk about wearing them? Walking about with any significant magnification may leave you feeling pretty giddy/ nauseous. You will also have a reduced field of view, though that may not affect you too much depending on your underlying eye condition, so that may make navigation awkward.

The Vixen binoculars which Olly mentions have excellent optics, and if a headband mount is available these could work well for TV etc. These have approximately a 28 degree field of view which is great for binoculars - but a bit restrictive for walking. Also a bit bulky.

Similar dedicated low vision devices are available which are more compact and lighter, eg:

Link here

Similar magnification to Vixen SG, but a narrower field of view - 20 degrees. Probably inferior optics though as the lenses are plastic - much lighter though. Less light gathering because the objective is smaller than the Vixen, so the image probably not so bright. This wouldn't matter too much for TV, but not so good for dark sky viewing.

One other thing to consider. If you are very short-sighted or long-sighted or astigmatic that may affect the performance of these devices.

There are other options eg using high power -ve contact lenses, together with "ordinary" spectacles with a +ve lens which together form a Gallilean telescope. This typically has less magnification but a wider field of view. Cosmetically its a better solution, but it does require that you have sufficient vision to enable insertion and removal of the contact lenses. Also if you remove the glasses and just have the contacts in your vision will be awful!

Hope that helps!

 

 

[Tommohawk]

Quick follow on - here's a link showing the magnifications with varying powers of contact lens and spectacle lens. You'll see the magnification is also dependent on the vertex distance - that means the distance from the contact lens to the spectacle lens. Spectacles are usually worn at about 11mm vertex distance - but you can usually fit the glasses so they sit at 17mm fairly easily.

Field of view is also quoted at the bottom of the chart but I think this must also be dependent on the size of spectacle lens used.

Link here.

Cheers,Tom

 

 

[Louis D]

How about just a pair of VR goggles displaying the view from a head mounted camera?  You'd have a wide field of view and the view could be magnified at will with a zoom lens or auxiliary lenses on the camera.  It might even be possible to overlay magnifications of signs your eyes are looking at with the proper image recognition software.  I don't know if such a system exists currently, but if you got it working, I'm sure there would be a market for it.

[mikeincousa]

On 3/6/2018 at 07:22, Louis D said:

How about just a pair of VR goggles displaying the view from a head mounted camera?  You'd have a wide field of view and the view could be magnified at will with a zoom lens or auxiliary lenses on the camera.  It might even be possible to overlay magnifications of signs your eyes are looking at with the proper image recognition software.  I don't know if such a system exists currently, but if you got it working, I'm sure there would be a market for it.

There are some commercial VR solutions but they typically run from $3000 to $7000. The sources and claims are questionable. That is what led me to looking at optical solutions.

 

[mikeincousa]

At first I just saw the last response.

First some background for Tommohawk. I am monocular with an mild but advancing cataract plus a macular pucker. There are some other problems too.

None of the MD's have been able say what is the prime factor for my loss of acuity. The surgeons I have seen rightly advise me to wait for their intervention because of the multiple layers of inherent risks. A few months ago I started a local low vision support group. I have heard some real horror stories of such surgery going way bad.  They likely will keep me out of surgery forever, although I can not say that with 100% certainty right now.

I have seen three optometrists, with one being a low vision specialist. Each has mol left me to fend for myself. I have given up on them.

I have done a lot of research regarding visual optics, ophthalmology, and optometry. I am working through a couple of nice book on Geometric Optics. One research thread led wearing flip up magnifiers over my readers. They work veru well. My Rx's are not that strong. I could sent them if you like.  This print is very easy me to see without the flipper boost, but I really have to lean toward the screen and that pull all the way down my neck and backside.

All this set the course for distant compound optics. My gauge is the distance at which I can crisply resolve license plate letters and numbers. I am at about 6 feet roughly depending on the light. One of the group  participants has a pair of the TV glasses. They seem to put me on the right path. That too adds to my motivation for exploring the G. Telescope ideas. Ideally I would like three optical solutions. One the right Rx for ergonomic screen viewing for my frame, ca gt 20 inches. One with G. telescopes, like the ones  surgeons and dentist use, for reading at a distance where I can engage active reading marking of complex content. And for distance viewing improved facial and sign recognition. To the last I had not thought of the stability issue. Good point. I can make out shapes at a distance but they are steadily becoming less distinct. The hand-held monocular helps a lot for this, but it is not perfect. It works best for overhead store signs.

The Vixen Binoculars look interesting. They track one of many unanswered questions, which is the possibility of using a wide-field-bioptic style lens for widening my field.

One of the above comments spurred me to take a first look at wearable CCTV cameras with live streaming. I am not sure that technology will take me towards my goals. Also it sounds much more complicated then stacking up lenses or purchasing an off-the-shelf solution. 

Way past dinner time and likely TMI too.

Thanks for all the stimulating comments.

Bye for now.

 

 

 

 

 

 

[Louis D]

I don't know if they'd help, but there are several lines of focusable eyeglasses that might broaden the range of distances at which you can focus clearly.  Perhaps these could serve as a base upon which to stack additional lenses.  I gotta say I feel lucky to just be dealing with presbyopia and astigmatism after reading your last posting.

[Tommohawk]

Hi Mike. It sounds to me like you've done plenty of reading around the subject and I suspect you will get to the point where none of the experts will be able to add very much!

Macular pucker - I guess we tend to call it epiretinal membrane (ERM) these days - can be tricky because it causes distortion as well as blur. One good thing is that this usually only affects the central vision, though in some cases it can extend beyond the macula. This means the peripheral vision is typically more or less normal. It may sound like a small mercy but its really important for simply getting around. You mention you have cataract - this is obviously not helping but determining how much vision reduction is due to the cataract and how much to the ERM can be tricky.

You also mention other visual complications - not sure what that might be? Also you say you are monocular - not sure does that mean your other eye has no vision or very reduced vision? Or maybe only one eye? Again PM me re this if you prefer.

Treatment for cataract is usually simple of course, though there is an increased risk of post-operative macular inflammation if you have ERM.  Also if an eye with significant cataract and ERM has cataract surgery the resulting post-op vision from that eye if often much brighter than the vision from the fellow eye which can cause problems. From what you say this may not be an issue.

Treatment for ERM (membrane peel) isn't always straightforward and there are certainly cases wher the surgeon is pleased with the outcome but the patient isn't.

If you only have one good eye the risks are obviously greater with either procedure.

Thinking about your specific visual requirements.

1. For PC / screen work there are 2 separate issues - you need to see print clearly and it needs to be at a range that is comfortable from an ergonomic perspective.

TBH I think the best solution here is probably to have ordinary spectacles with a focal range which suits your screen, to correct for any basic long-sight/astigmatism/presbyopia and then simply increase the font size. It should be possible to do this using one or another of the Windows adjustments. Not sure about Mac. This coupled with a larger screen is likely to be the best solution especially if your vision is OK to read this size font without the flip-up mag.

Using a magnifier lens mounted on spectacles like your flip-up type will require a closer position (as youve discovered) and isn't really great.

Using compound optics or a telescope type device could work in terms of providing magnification, but would likely be uncomfortably heavy and places higher demand on the eyes in terms of tracking accuracy - you would need to move/rotate the eye/head less to scan text which is more demanding and calls for greater precision.

There are some instances where the Windows access solution isnt so good but it should work for most things. I have an app which has diabolically small font which I can't adjust and I routinely set Windows to 125% to help with this. Some graphics seem to render a bit odd but for most apps its fine.

2. For closer work you have a range of options, but generally this is easier. Your flip up magnifiers or a stand magnifier or just simple spectacles with a close focus. I have good vision but routinely use a headband magnifier with built in illumination for cleaning telescope components/sensors.

The Gallilean telescopes to which you refer such as those used by surgeons are good - but pricey. The main advantage is they give good magnification without getting too close. From what you say a monocular device may be adequate? Its probably possible to purchase a monocular which you could fix to spectacles. But for occasional detailed work its often easier to just get closer.

3. For distance vision - this is probably the greatest challenge. For sedentary work some kind of spectacle or head mounted device can work well, but maybe a bit clumsy/heavy. VR devices are OK but again pricey - at least for the time being. There are VR type devices into which you insert a mobile phone and use the phone screen which may work well, but I don't know the latest on these.

For walking and general getting around I think you'll find that any device which offers significant magnification will make you feel pretty unstable. Also for getting around peripheral vision is key - your's is probably good from what you say - and you will restrict this with any kind of telescope device. Probably a -ve contact lens with +ve spectacles to form a telescope is the best solution - but typically the magnification is only 1.5x or thereabouts.

I hope thats of some help, though I think you probably knew 99% of it!

By the way you say you have found "a nice book on geometric optics". That's a result - all the ones I read were uniformly awful!!

Let me know if there's anything I can help with.

Cheers

Tom

 

 

[mikeincousa]

Thanks for you comments Tom.

In short Tom, as of this morning, I reached a point where I would like to start homing in on specifics of designing and building Galilean Telescope and Spotting scopes. I have collected several articles that I will need to study in-depth. This is one start point http://galileo.rice.edu/lib/student_work/astronomy96/mtelescope.html

Two immediate questions.
Will a pair of lenses like in the top figure produce an erect image or will I need some sort of erecting prism or eye piece to get a proper image with right side up and and not reversed.

Can you suggest some places where I can start sourcing lenses and other parts?

For your other vision topics I will PM you.

 

[Louis D]

8 hours ago, mikeincousa said:

Will a pair of lenses like in the top figure produce an erect image or will I need some sort of erecting prism or eye piece to get a proper image with right side up and and not reversed.

After reading this Wikipedia article on refractors, using a concave lens as the eyepiece results in an upright image, though with a narrow field of view.