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 Post subject: Double images
PostPosted: Sun Apr 14, 2019 11:52 pm 
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Posts: 132
Location: Surrey, UK
Does anyone know a way to stop seeing double images when using a binocular microscope?

I always see two of everything, displaced sideways.
With very low mag stereo microscopes it's OK.

I have tried adjusting the interpupillary distance, the eyepiece correction, using my specs and not, and altering the distance from eyes to eyepieces.
And I've tried a lot of microscopes.

Basically there's no point for me to have a binocular scope.


Last edited by ChrisR on Mon Apr 15, 2019 7:12 am, edited 3 times in total.

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 Post subject: Re: Double images
PostPosted: Mon Apr 15, 2019 2:55 am 
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If it persists between different scopes, could it be a case of strabismus?


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 Post subject: Re: Double images
PostPosted: Mon Apr 15, 2019 6:03 am 
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Chris -- To begin you might want to double check the alignment of your scope(s). Likely there are directions online. Basically, you focus on an accurate target and, looking one eyepiece at a time, make sure that target is aligned exactly the same. A quick way with a zoom stereo microscope is to zoom and focus on a penny so the head just fills the frame perfectly at the edges of the penny, with the head perfectly vertical. The image should then be the same in the other eyepiece -- not displaced, not larger or smaller, not rotated. The farther it is off, the harder it is for all of us to merge the images.

If you use corrective lenses -- and remove them to use the microscope -- you may also want to keep them on while doing this or at least make sure the magnifications from each eyepiece are the same.

Lots of stereo microscopes are somewhat to significantly misaligned -- and various people will cope more or less. It could be that if you get a really well aligned scope, you'll be able to get a stereo image at somewhat higher magnifications.


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 Post subject: Re: Double images
PostPosted: Mon Apr 15, 2019 6:21 am 
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Here is an excellent link to microscope binocular collimation

viewtopic.php?f=15&t=5329&p=47942&

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 Post subject: Re: Double images
PostPosted: Mon Apr 15, 2019 8:39 am 
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Hi Chris,
since you can use the stereo microscope without problem it is is a question of the right microscope and eyepieces for you. The eyepieces give a very different image in eye relief and viewing angle.
Can you post pictures of the two microscopes?

Bob


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 Post subject: Re: Double images
PostPosted: Mon Apr 15, 2019 2:07 pm 
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Most stereo microscopes have slightly angled convergent ocular tubes , in order to maintain the natural angle that our eyes take when we view objects at close focus. This degree of convergence is necessary because stereo microscopes simulate the use of our eyes naturally but as though we are using a strong magnifying glass separately with each eye.

Binocular higher power microscopes do not work like this, having both eyes viewing the same image that has been split. Early binocular microscopes were based on a convergent binocular model but when the beamsplitter began to be employed most companies adopted either a Jentsch binocular head or a Seidentopf type, both of which dispense with convergent optics. A person with a slight difficulty maintaining convergence, or as mentioned above having even a mild case of strabismus could find non convergent binoculars difficult and convergent binoculars o.k.
In the early days of the development of split image binocular tubes there was controversy over the best way to make binocular instruments comfortable. Apparently, many early microscopists did not like binocular tubes. Since they all had been trained on monoculars, a certain number in trying out the new technology found them unusable. Spencer, even went to the trouble of offering a head, where one eye of the binocular could be blocked off and even better, where the head could be shifted sideways to create a monocular head. It seems quaint today but in a lab with only one microscope used commonly, it may have been the cat's meow.
Further, for many years Spencer made binocular heads with Jentsch type heads that had conveniently angled eyetubes at the physiological norm of 4 degrees, which maintains a convergence point of 17" at an interpupillary distance of 62mm.
Spencer-AO, continued to mfg. these convergent heads up until the series 20 100 watt microscope, switching to Seidentopf heads subsequently.
If you can find someone with a Spencer or AO binocular made prior to about 1980, either infinity corrected or 160mm, you might find that one of these works better for you but since you are in England, they aren't that common. A check of some available catalogues might reveal whether any of the older U.K. companies did the same. AO and Baker had a working relationship after the war, until AO purchased Reichert in 1962 and even shared optics. Perhaps Baker, previously had similar heads.

The question might come up of why would it have seemed important to have a convertible head in 1920 and yet such difficulties with binocular heads seem uncommon now? The answer lies in the demographics associated with the early microscopist community, who trained on monocular scopes and the demographics of modern microscopists, most of whom trained on binocular scopes. Have you ever tried to show a child a view in the microscope, only to have them say, "I have to use one eye, it makes me cross eyed when I use both eyes" and no matter how you adjust the interpupillary distance they still can't use both eyetubes. Those are the the kids destined to not be microscopists in the era of binocular microscopes , because the microscopes they are trying will not work for their eyes and kids like that get weeded out of microscopy despite the interest level. In 1910, they might still have continued.
A binocular microscope can be critically adjusted to accomodate a unique convergence but it takes a very hands on approach, with the microscope and user present.
It is also one more reason why the first microscopes for children should be stereo microscopes.

Here is a curio related to the thread viewtopic.php?f=24&t=1042&hilit=1925+spencer


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 Post subject: Re: Double images
PostPosted: Mon Apr 15, 2019 4:07 pm 
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This might be a good use case for one of Vision Engineering's big projective heads. I have not used one myself but have heard good things.
Oddly, my dad could not use a Nikon smz-10 (I tried with two good copies), but the b&l stereozoom 7 and a few others are fine.


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 Post subject: Re: Double images
PostPosted: Mon Apr 15, 2019 7:46 pm 
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Hi Chris,
The first time I looked through a binocular microscope I had that effect, the technician showing me the microscope told me to move my head well back and concentrate on the two small spots of image in the centre of the eyepieces, then while concentrating on those relax my eyes and let the two merge into one. When the two have merged slowly move the head towards the microscope always maintaining the image in the centre of the eyepieces, and when your pupils get to the eyepoint you should be viewing normally.
I hope this helps.
Peter.


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 Post subject: Re: Double images
PostPosted: Mon Apr 15, 2019 11:04 pm 
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Joined: Tue Jun 14, 2016 11:01 pm
Posts: 132
Location: Surrey, UK
Thanks for all the suggestions!
I don't think it's a microscope fault; I tried several at a Quekett meeting. The one which was different was a stereo with a triple lens-pair turret, possibly from the 60's. It was quite "V" shaped, perhaps its focal axes were convergent.

If I'm incapable of viewing at infinity, how come I can see stars and use binoculars?!

I tried pulling back from a pair of high-eyepoint eyepieces on a Laborlux. The same detail was visible in the vignetted images, and I couldn't align them even playing with the i-p distance.

I need to revisit the odds and ends of scopes I have.


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 Post subject: Re: Double images
PostPosted: Tue Apr 16, 2019 7:03 am 
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ChrisR wrote:
... The one which was different was a stereo with a triple lens-pair turret, possibly from the 60's. It was quite "V" shaped, perhaps its focal axes were convergent.

If I'm incapable of viewing at infinity, how come I can see stars and use binoculars?!

Mmmm ... That's an interesting observation, Chris ... and at first sight perhaps contradictory

Normal [i.e general outdoor viewing] "Binoculars" are typically set parallel.

Further investigation is definitely required.

MichaelG.

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 Post subject: Re: Double images
PostPosted: Wed Apr 17, 2019 8:53 pm 
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ChrisR wrote:
Thanks for all the suggestions!
I don't think it's a microscope fault; I tried several at a Quekett meeting. The one which was different was a stereo with a triple lens-pair turret, possibly from the 60's. It was quite "V" shaped, perhaps its focal axes were convergent.

If I'm incapable of viewing at infinity, how come I can see stars and use binoculars?!

I tried pulling back from a pair of high-eyepoint eyepieces on a Laborlux. The same detail was visible in the vignetted images, and I couldn't align them even playing with the i-p distance.

I need to revisit the odds and ends of scopes I have.


Infinity has nothing to do with what I wrote earlier. It would'nt be a case of not being capable of viewing infinity, in fact viewing at infinity should alleviate the problem more so.
Binoculars have separate optical systems like a stereo microscope, one for each eye, so they function physiologically like a stereo microscope, just a long distance stereo microscope, so they should be easier too. The tubes are more parallel because of the distance at which they are focusing but like through a stereo microscope, each eye has a separate image that it uses and an opportunity to be viewing naturally through a collimated lens system at a comfortable distance. As the point of split between the images gets closer, any issues with ones own collimation should get worse, so a monobjective microscope where the image splitting typically takes place about 5 to 7 inches from the eyes will cause a more severe strain on one's physical optical alignment, exacerbated somewhat by the optical tubes being parallel, instead of convergent.
The pre 1980 Spencer and later AO head, was designed to alleviate this small geometry mismatch somewhat and it may work for you because it provides a geometry more similar to a Greenough stereo microscope. Someone around your Quekett meetings might have a Spencer or AO biological scope with the Jentsch head. Give it a try if found. It might do the trick and at least point out some options.
I recall seeing another older brand of European microscope that also had a Jentsch head with convergent tubes but it hasn't come to me what it was.
I can't find any Baker, CTS or Watson that were that way inclined. Just thought one of those would be easier to lay a hand on, if so.


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 Post subject: Re: Double images
PostPosted: Wed Apr 17, 2019 11:17 pm 
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Location: Surrey, UK
I don't follow, sorry. :? For binoculars and binocular microscopes, am I looking parallel-eyed and focusing at infinity?


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 Post subject: Re: Double images
PostPosted: Thu Apr 18, 2019 4:14 am 
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Posts: 132
Location: Surrey, UK
do I need :
Attachment:
beck.jpg
beck.jpg [ 40.74 KiB | Viewed 217 times ]

?


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 Post subject: Re: Double images
PostPosted: Thu Apr 18, 2019 6:04 am 
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Posts: 848
Hi Chris,
there are binocular tubes with parallel and converging (most stereo microscopes) tubes. It seems that you "inbuilt optics" are only compatible with converging tubes. On compound microscopes these are not very common. Apochronaut probably means a head like this: https://www.ebay.com/itm/283432446941
I thought about it and couldn't think of an other microscope brand using converging tubes. There will be other makers but not very common on the market. So it would probably be the best idea to look for an AO or Spencer microscope with this feature. Maybe write a search-thread in this forum, at least to get a peek through one of these instruments?

Another idea would be to simply use a camera with full-hd- video output and observe on a screen. Many people do this because it fits their needs better. If I were restricted to this method it wouldn't be a big loss for me.

Bob


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 Post subject: Re: Double images
PostPosted: Thu Apr 18, 2019 8:51 am 
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ChrisR wrote:
I don't follow, sorry. :? For binoculars and binocular microscopes, am I looking parallel-eyed and focusing at infinity?

Chris,

This issue is intriguing me, and I suspect that the cause of your problem might be [for want of a better term] psychosomatic.

Please bear with me, whilst I 'think aloud' ...

Yes, in ideal circumstances your viewing through either binoculars or a typical binocular microscope [but not the AO item mentioned above] should be 'relaxed' i.e. parallel-eyed and focusing at infinity.
But this is counter-intuitive when you know that you are looking at something close, and I suspect that your eyes are converging because of that awareness.
Difficult as it may be ... I think you need to train yourself to 'believe' that the view through the [parallel] binocular microscope is that of a large object seen at a distance, not a small object observed closely.

The situation with the splayed eyetubes of the Stereo Microscope that you mentioned is, of course, more intuitive; but it does put the eye muscles under continual stress.

MichaelG.

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 Post subject: Re: Double images
PostPosted: Thu Apr 18, 2019 10:09 am 
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Location: Surrey, UK
Could be, Michael, but I have yet to work out how, as I think I have control over my convergence. :( It's not unique - there are similar tales to be found on the net. Of course those dozen reports could be the only 6 in the world, moaning a lot...

I thought I'd try my "new" SMZ again. I've been using it without noticing a problem. So I took it down (no permanent space..) and yup, focused on some print without thinking. Then closed one eye and realised no light at all was coming out of one eyepiece because the trinoc diverter was in place, probably for the past couple of weeks. I hadn't noticed.
Switched in again, I see 2 images until they "come together", then it's ok.

Though I have about 4 I don't have a bino scope handy, I usually use a monocular, as it happens. I can see one, but not reach it - other side of "stuff" :roll: .


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 Post subject: Re: Double images
PostPosted: Thu Apr 18, 2019 11:12 am 
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ChrisR wrote:
I don't follow, sorry. :? For binoculars and binocular microscopes, am I looking parallel-eyed and focusing at infinity?

m

You are focusing at the subject. Even with binoculars, you are seldom focusing at infinity, only if you are looking into space. With a stereo microscope the ocular tubes are inclined because the subject is very close, so they must be convergent. With a binocular microscope the subject is in fact even closer. Old binocular microscopes, as illustrated above were convergent because they had to be. Once a beam splitter was installed way up the optical tube instead of having long very difficult to collimate convergent tubes, parallel eyetubes could be used but that was an issue of convenience for the manufacturers and they are easier to use for people with a degree of exotropia, so it is a case of robbing Peter to pay Paul. The acceptance of binocular microscopes was very slow because anyone with even a touch of esotropia could find their use difficult. Strabismus is not uncommon, it occurs in 1/50 of the population and there are probably many people with just a touch of it. It could get worse with age, as the muscles get weaker.

In using convergent eyetubes, they more easily fall into line with the physiology of an esotropic person because the point of focus is so close with a binocular microscope fitted with a beamsplitter head. I, myself am slightly exotropic, so I have just slightly more difficulty with convergent heads and stereomicroscopes than with a Seidentopf head for instance. I have collimated a head on an individual microscope in the past and had another person using it say that they were getting a double image with it and couldn't use it.
.


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 Post subject: Re: Double images
PostPosted: Thu Apr 18, 2019 12:14 pm 
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apochronaut wrote:
ChrisR wrote:
I don't follow, sorry. :? For binoculars and binocular microscopes, am I looking parallel-eyed and focusing at infinity?

You are focusing at the subject. Even with binoculars, you are seldom focusing at infinity, only if you are looking into space.

For the avoidance of doubt, Chris
When I wrote "focusing at infinity" I was referring to the relaxed state of your eyes, not to the focus of the optical device.
Your personal 'infinity' could be anywhere; and, if you have corrective lenses, will be different with/without their use.

MichaelG.

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 Post subject: Re: Double images
PostPosted: Thu Apr 18, 2019 5:50 pm 
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Chris, Given that you can use binoculars, a guess is that you'll be able to figure this out. Hopefully someone near you has a number of known-collimated microscopes you can try out over time, without the pressure of viewing at a meeting.

Interpupillary distance is one critical factor - you want it within half a mm or so of just right. If you wear glasses, this distance should be on your prescription and most modern scopes will let you set it, at least approximately.

Very wide field eyepieces often tend to be pretty finicky about the distance of your eyes from the eyepiece, so you might want to start with decent 10x by 18 or 20mm field oculars in a modern scope.

Do you now have a binocular scope at hand?


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