Does anyone have recommendations for 3D magnifiers for PCB work?

I suspect that because they are designed for a focal distance of 420mm, then if I used them on top of cheap reading glasses I could get much more magnification at a much shorter focal distance.

The focal length of a lens, f, is the distance at which it will focus parallel rays, for example, sunlight.

Given the focal length and distance from the object, O, you can calculate the magnification, M = image size / object size, of the object as shown in the diagram below.

1 / image_distance = 1 / focal_length - 1 / object_distance

Magnification = image_size / object_size = image_distance / object_distance

https://byjus.com/physics/lens-formula/

If you add a second magnifying lens, the combined focal length will be shorter and magnification greater. The focal length of the combination can be calculated by the following formula:

1 / f = 1 / f1 + 1 / f2 - d / (f1 x f2),

where f is the focal length of the combination. The focal lengths of the 2 lenses are f1 and f2, and the distance of separation is d.

https://physics.stackexchange.com/questions/247617/how-is-focal-length-defined-for-a-two-lens-system-separated-by-a-distance-d

So simplistically using x3.5 reading glasses should bring the focal distance down to about 6", which would be OK.

I'm not sure if that holds when the dental loupes are already a two lens system.

I think a lot of the 3-D effect is resolution, and getting a good viewing angle...what if I may ask is the resolution of your viewer?

I know to get to blueray resolution on my computer screen I had to change the video card in my computer, go to HDMI connections, and buy a new hd monitor....even though I thought I had HD to begin with...and change the DVD drive to a blueray capable reader...So getting digital resolution to a 3D like experience is not so easily done...and to get the best experience you need not only high quality optic magnification, but you need high resolution viewing as well...

https://projectorslab.com/everythings-about-resolutions/

The ultimate setup is an engraver type binocular....but can get very pricey

The digital microscope I have is 1080p, but to get this picture

I had to prop the board on its side because the solder pads are underneath the socket I was trying to fit.

(Bizarrely the PCB has ten solder pads in a mixed up order for a Mini USB connector)

As I said before this device is great for inspection but for rework you need real 3D.

The microscope I prefer for PCB work is the stereoscopic eyepiece-less ones like the Mantis products of Vision Engineering. They cost a pretty penny but IMHO they are worth every pretty penny they cost, particularly if this will be for constant use.

For infrequent, occasional use or you must be more frugal, multiple companies make headband magnifiers.

In the past I spent a lot of time using the older, box-looking Mantis. If I was spending much time at the Mantis I would need to slow down and figure out the best height for my chair and best way to adjust the Mantis arm. Sometimes I would put a board under my ESD pad to raise the work surface by an inch or two. Once you get everything just right you can sit down and be comfortable for hours of 3D magnified work.

(Even a Mantis can not make 0.4mm pitch parts fun to work with.)

Yes I mentioned the Mantis we had at work in my original attempt at this question; I am retired now and certainly can't justify that sort of cost. But I agree that they are fantastically useful instruments: what surprised me most when we got one was that as soon as you could see clearly your hands started to behave OK.

For "cheap" have you simply tried the camera on your mobile device?

Used to work in the PCB load/solder/inspect world and there were some pretty good video imaging units that were hand held or able to be mounted.

Most modern phones have camera capability with auto-focus capability. I've also seen aftermarket options for macro lenses to be applied to phones to give that extra capability.

It depends a lot on the resolution required. If your PCBs are using through-hole components on a 0.1" grid, like I've been making for the last 45 years or so, then the OptiVISOR™ headband magnifiers are excellent. Between work, car, and home, I keep 5 sets of them handy, with 2 or 3 magnifications.

Over the years, I've tried quite a few other brands, but never found any quite as good. Definitely make sure the lens/prisms are glass, or at least have ground surfaces. Plastic lens/prisms are commonly molded, although it is certainly possible to make high precision optical lenses (such as the prescription glasses I'm using right now).

Since you mention 420mm focal distance, I suspect that these would do fine. I more commonly use a focal distance between 100 and 200mm.

If you are working with much finer SMC on a much finer grid, then an optical binocular microscope is what you need, but then your focal distance will be way shorter.

Any microscope that has a flat display, by definition does not provide 3D viewing, and in my experience is useless for soldering or other fine work where you need to accurately position your tools.

"Any microscope that has a flat display, by definition does not provide 3D viewing, and in my experience is useless for soldering or other fine work where you need to accurately position your tools."

Exactly.

Have you researched USB microscopes, have used one on a laptop the check SMD device soldering?

Also used them with mechanical adjustment of really small gear mesh after making replacement gears.

A few years back I did some research on microscopes for printed circuit board work. One useful source of information I found were the Louis Rossmann videos on YouTube. Louis and his employee’s use microscopes all day every day. Louis shares his opinions on microscopes. Actually, Louis shares his opinions on many things so you may need a cup of coffee and a few snacks if you are going to watch his videos.

To find several videos go to YouTube and search for “Louis Rossmann microscope”.

Probably the best single microscope video of his is https://www.youtube.com/watch?v=C_eQrbop-J4.

It is also helpful to do YouTube searches on "Louis Rossmann The Tools I Use and Why I Bought Them" and "Louis Rossmann Tools We Use - Tools You Need".

YouTube posted a commercial for the following when I did my search. Now, that is a microscope! https://discover-echo.com/revolution?gclid=CjwKCAiAp8iMBhAqEiwAJb94z1Cd5kE7umdlj_VL_5FF-eKqnfvm3mYGM5Ukadv45N_ArNNh0-g3kxoC3e4QAvD_BwE

WARNING: Louis Rossmann is a New Yorker. He has a computer repair shop on the streets of New York. Louis talks like a New Yorker. Whenever he needs a adjective, adverb or pronoun he uses the same multi purpose, four letter word. I went to school with New Yorkers and I once worked for a Navy Chief. I can handle it. If, by chance, you have tender ears or your feeling are easily hurt then Louis Rossmann’s videos might not be for you.

The Amscopes are certainly cheaper than the vision engineering Mantis range. I'd have to try one to be convinced that they are as good.

I can easily put up with his swearing, but what drives me to distraction is his constant use of "ex" when he means "times": the only reason we use the letter "x" in typed stuff is because there is no "times" key on the keyboard; to start pronouncing it as "ex" instead of "times" just seems stupid to me.

Had good luck time ago using a good analog camera module adapted to an old zoom telephoto film camera lens, giving input to a big -at the time- 32 inch LCD TV. The interesting thing about my implementation was that the camera stands between me and the monitor and despite that, it actually is NOT in the way. How was that accomplished? Well those of you from the film era might remember that a telephoto lens cannot focus very close by design or magnify for that matter. This can be rectifyied by a simple trick. Just by increasing the distance from lens to sensor. We are talking about 10-15 cm depending on the magnification you want to accomplish. The unique thing about this is that you can have huge magnification (like a MACRO implementation) plus the camera can be FAR away from the object (enough not to be in the way of my sight to TV monitor. The unexpected high depth of field was an added benefit. At zero picture latency you have full eye to hand coordination potential, could see all IC markings clearly even wiped ones etc. Just don't try this with a USB camera module. Don't ask me how I know (LOL). Dissadvandages? Of course, using this system you loose most of the incoming light so the object needs to be a bit better illuminated at the point of interest, but that was not a difficult problem to solve. 1W white leds was right around the corner and you could easily control the beam. I think similar logic is used on some camera microscopes nowdays, but still if you want the canera to be higher (above your head for example) and still focus, you must modify the lens-sensor distance. And I repeat, forget USB cameras they are mostly cr#p on video and latency is unacceptable. Just before covid I bought a HD camera with HDMI plus analog connector, did the same mod and now I project on a 43' TV 50 cm away and all is OK. My VGA resolution... eyes is the limiting factor. By the way, I think anything "3D" is overrated and on cheap implementations is a huge stress for your eyes. S.M.

Hoping you feel like showing off a little and posting some pictures of this equipment setup.

Not really (LOL), had to wipe a pound or so of dust from the original one on the top shown with the modern version for size comparison. Still the lens looks OK.

Its sensor is attached to a tube end that can slide inside the bigger black tube at the first lens to adjust magification and focusing distance.Its length is an overkill, as is you can use it from 6 feet away but never came to cut it a bit shorter. Lens controls are also nesesary to get optimum results.

Now about depth of field that my friend dkwarner mentioned, it really depends on aperture setting. The narrower the aperture the greater the depth of field, but also the need for stronger lighting of the workpiece arises.

Now imagine each of those standing above your head shooting the work area and showing at the screen with minimun latency. The newer device definition is of course better but the old one was pretty respectable considering what are you are using it for. I could try to take photos of them working if you are interested, but it may take some time to get the old one working. Can't even find its power supply now. S.M.

I used that combination of a telephoto lens and about 15 cm of extension tubes (with a film camera) about 60 years ago, to take pictures of something happening a few inches down inside a ≈1" tube. It works!

On the other hand, The results have poor depth-of-field and are essentially 2D.

I sure could have used some of those white LEDs back then...

Thanks to everyone who contributed. On looking more carefully at the EEEKit magnifiers: you only get the higher magnification for one eye, and even at the lower magnifications you're stuck with having to get very close to the subject (just like +3.5 reading glasses).

So, I decided to try the Dental loupes: they are really good; because they are effectively binoculars you are able to work at a comfortable distance, but your perception is that the subject is larger and closer. But I don't think I will be able to add the extra magnification with reading glasses.

Here's an example everyone can relate to:

This is very strong and thick top stitch thread

together with a fairly small needle

One of those needle threading devices is useless because you can't get two thicknesses of the thread through the width of the eye

But using the loupes I was easily able to thread it

For those of you that think that stereo vision is not important: find a needle and thread combination which you can just manage OK. Now try it with one eye closed.

I need to use reader glasses nowadays and i have found that by putting on 2 pairs at once i can see an enlarged view. I do need to put my head closer to the object ( or vice versa ) but it is a quick and simple solution.

Yes: although I used threading a needle as an example above, I am perfectly happy putting on +3.5 reading glasses to thread a needle. But if you're working on something for a long time you really want to do it at a comfortable distance.