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Nikon Optiphot stage issue

 
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Photomicro



Joined: 12 Aug 2017
Posts: 33
Location: UK

PostPosted: Sun Nov 05, 2017 4:04 am    Post subject: Nikon Optiphot stage issue Reply with quote

I have a Nikon Optiphot with an unusual problem with the stage. Put simply, I think it is slightly tilted, from front to back. This is seen in the image in that when the centre is in focus, the top and bottom of the field are not. One is brought into focus by using the fine focus in one direction, the other by moving the other way. There is no issue from left to right, though obviously only the central band is OK.

I have experimented with re-seating the stage on the dovetail, but with no joy.

It occurs to me that there could be some sort of adjustment to correct this, but with so many screws and bolts on such a mechanical stage, am at a loss to see which, and don't want to do any harm. Am hoping someone has seen this before.

It is slight, but once you have noticed it, rather annoying.

Thanks for your time, Mike.
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zzffnn



Joined: 22 May 2014
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Location: Texas USA

PostPosted: Sun Nov 05, 2017 6:13 am    Post subject: Reply with quote

Mike,

Are you sure such a tilt is caused by the stage, not by something else like misaligned nosepiece/ head or objective (which is much more common)? Have you tried reseating / switching to a different nosepiece, head or objective as well?

If it is indeed the stage, here is a temporary patch (that does not eliminate the cause):

You may measure the tilt difference in microns, using your scope's fine focus drive. Then pad/correct the difference with thin metal/plastic sheets of defined thickness. Parfocal rings for objective can correct as little as 10 microns of verticle difference, if I remember correctly; you can simply use those rings as padding sheets under the stage.
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Photomicro



Joined: 12 Aug 2017
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Location: UK

PostPosted: Sun Nov 05, 2017 12:31 pm    Post subject: Reply with quote

Thanks for that, I think you are on the right lines here. The problem is also seen on a Labophot 2, and both have a changeable nosepiece that has a dovetail, which has a registration slot/pin and a screw to tighten. On adjusting this I see it also affects the situation, though I can't get it right.

I notice that on the Labophot, the thing the dovetail slots into is attached to the body via three allen bolts. I wonder of there is some leeway there.

Thanks for pushing me in the right direction, I will think on this some more.

Mike
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zzffnn



Joined: 22 May 2014
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PostPosted: Sun Nov 05, 2017 1:13 pm    Post subject: Reply with quote

Changeable nosepiece is rare for Labophot's, though standard for Optiphot's. I upgraded from Labophot 2 to Optiphot 1, because I wanted changeable nosepiece.

Yes, those three Allen bolts may change the alignment slightly. Please do try them, but don't force too much and try to tighten them the same way and align them visually. Take note on which side is higher and how much higher. You may need to go back and forth many times.
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Choronzon



Joined: 21 Feb 2010
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PostPosted: Sun Nov 05, 2017 4:21 pm    Post subject: Reply with quote

Are you using the same head on the labophot? Switching it between the two?
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Photomicro



Joined: 12 Aug 2017
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PostPosted: Tue Nov 07, 2017 2:59 am    Post subject: Reply with quote

zzffnn wrote:
Changeable nosepiece is rare for Labophot's, though standard for Optiphot's. I upgraded from Labophot 2 to Optiphot 1, because I wanted changeable nosepiece.


I hadn't realised it was, especially as the objectives face rearwards, unlike the Optiphot 1, where they point towards you. One reason why I prefer using the Labophot 2. Also, an allen key is used to loosen, so there is just a discrete opening for this, rather than the obvious knurled knob.

zzffnn wrote:
Yes, those three Allen bolts may change the alignment slightly. Please do try them, but don't force too much and try to tighten them the same way and align them visually. Take note on which side is higher and how much higher. You may need to go back and forth many times.



Yes, sounds like a job for a clear mind, and taken steady, I don't want to make it worse.

Thanks for your support, much appreciated.
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Photomicro



Joined: 12 Aug 2017
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PostPosted: Tue Nov 07, 2017 3:02 am    Post subject: Reply with quote

Choronzon wrote:
Are you using the same head on the labophot? Switching it between the two?


By head, do you mean the nosepiece? (not switched as yet)

or...the binocular head?

Mike
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Choronzon



Joined: 21 Feb 2010
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PostPosted: Tue Nov 07, 2017 10:30 am    Post subject: Reply with quote

Are you switching the viewing head and /or the stage back and forth?
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Choronzon



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PostPosted: Tue Nov 07, 2017 10:49 am    Post subject: Reply with quote

Are you switching the viewing head and /or the stage back and forth?
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Photomicro



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PostPosted: Thu Nov 09, 2017 2:00 am    Post subject: Reply with quote

Choronzon wrote:
Are you switching the viewing head and /or the stage back and forth?


If you mean between the two stands, then no.

Mike
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Choronzon



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PostPosted: Fri Nov 10, 2017 11:08 am    Post subject: Reply with quote

How many microns focus difference are there between top edge and bottom through the eyepieces? Use the markings on the fine knob to measure
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genera



Joined: 05 Oct 2011
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PostPosted: Fri Nov 10, 2017 6:39 pm    Post subject: Reply with quote

Choronzon wrote:
How many microns focus difference are there between top edge and bottom through the eyepieces? Use the markings on the fine knob to measure


This is a very important question. Even on new microscopes, unless the stage has leveling adjustments, some degree of tilt should be expected. If it's only a couple microns you're probably going to have to live with it.

Some possible causes of an abnormally tilted stage:
-- Debris such as hair, dust, grit, or fiber between dovetail reference surfaces.
-- Reference surfaces deformed by impact, usually along an edge but sometimes in the center.
-- Original shims (pads or padding in zzffnn's post), if there were any originally, were improperly reinstalled or completely removed.
-- Something's bent or twisted. It's possible that the microscope was lifted using the stage as a handle.
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Photomicro



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PostPosted: Mon Nov 13, 2017 8:30 am    Post subject: Reply with quote

Choronzon wrote:
How many microns focus difference are there between top edge and bottom through the eyepieces? Use the markings on the fine knob to measure


With a x10 objective, and a plant section, from the top of the image circle to the bottom is about 10 divisions on the fine focus, so around 10 microns according to the manual.
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Pau
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PostPosted: Mon Nov 13, 2017 10:24 am    Post subject: Reply with quote

Photomicro wrote:
With a x10 objective, and a plant section, from the top of the image circle to the bottom is about 10 divisions on the fine focus, so around 10 microns according to the manual.

If you are focusing really in the same plane* this seems in principle too much. Some of my highly hacked microscopes do better

My method to eliminate errors due to the slide thickness is to focus in a very minute and identifiable detail with a 40X and move the stage, or use a high quality bare slide and focus small at dust specs on it at both extremes
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Last edited by Pau on Mon Nov 13, 2017 10:25 am; edited 1 time in total
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Choronzon



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PostPosted: Mon Nov 13, 2017 10:24 am    Post subject: Reply with quote

So that's not too bad. I suspect somebody at one time separated the dovetail block from the bearing block and didn't put the adjusting shim back in from when the factory built the stand. Some have shims on the top, some on the bottom, some have none. It's the only way to adjust perpendicularly on the microscope stand on the Y axis.
Lots of hacks out there.
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