microsystem 70 illumination

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stillcool
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microsystem 70 illumination

#1 Post by stillcool » Sun Mar 18, 2018 4:19 pm

i am in the process of restoring one of these scopes. I have replaced the bulb unit with an led in exactly the same position. i can adjust the 45/ mirror in the base to centre the stopped down light on the base of the condenser (with iris closed) however when you try and centre the condenser to place your light in the middle of the field of view there is not enough movement in the adjusters to get it centered and the light is quite badly off centre. The adjusters are well freed off and all the return springs are good.

I cant see how this can be adjusted using the available adjustments.

any ideas or comments?

if anyone has a copy of a manual for this scope i would appreciate a link to it

regards from (not so) sunny Scotland

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75RR
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Re: microsystem 70 illumination

#2 Post by 75RR » Sun Mar 18, 2018 5:52 pm

Hi stillcool, welcome

if you can post some photos of the conversion perhaps someone can spot the problem
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MichaelG.
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Re: microsystem 70 illumination

#3 Post by MichaelG. » Sun Mar 18, 2018 6:24 pm

Have a look at this page first:
http://www.microscopy-uk.org.uk/mag/ind ... son70.html

At the bottom of the page, there is reference to the 'Little Imp' CDs

Thanks to the generosity of Steve Gill, these are now freely downloadable via
http://www.microscopy-uk.org.uk/Little-Imp/index.html

Enjoy !!

MichaelG.
Last edited by MichaelG. on Sun Mar 18, 2018 9:51 pm, edited 1 time in total.
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apochronaut
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Re: microsystem 70 illumination

#4 Post by apochronaut » Sun Mar 18, 2018 9:44 pm

75RR wrote:Hi stillcool, welcome

if you can post some photos of the conversion perhaps someone can spot the problem

75RR is right. Pictures would help. Usually, led conversions are not straightforward. Microscope illuminators can be anywhere from moderately to critically engineered illumination systems and more often than not led conversions require more fiddling than they are worth.

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Re: microsystem 70 illumination

#5 Post by stillcool » Thu Mar 22, 2018 12:14 pm

[*]Update
this is a very very basic and simple mod that places the LED in exactly the same place as the original bulb element without any mods to the actual scope.

the led unit has been sleeved up to be a firm fit in the lampholder.

I also spotted that the microscope has a 6 position objective turret and that the whole problem of centering is fixed by slightly off-setting the objective from the preset "knotch".

im wondering whether the turret itself is causing the problem.
i cant see any adjustment for the turret centering
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MichaelG.
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Re: microsystem 70 illumination

#6 Post by MichaelG. » Thu Mar 22, 2018 2:13 pm

stillcool wrote:[*]Update
this is a very very basic and simple mod that places the LED in exactly the same place as the original bulb element without any mods to the actual scope.

the led unit has been sleeved up to be a firm fit in the lampholder.

I also spotted that the microscope has a 6 position objective turret and that the whole problem of centering is fixed by slightly off-setting the objective from the preset "knotch".

im wondering whether the turret itself is causing the problem.
i cant see any adjustment for the turret centering
May I suggest a quick check [unless, of course, you have done this already]:
Re-install the filament lamp; and see if the problem, and the ability to cure it by off-setting the turret, persists.

If it does ... then yes, I think it's probably the turret at fault.
If not ... then perhaps the LED position is not as 'exact' as you believe.

Clutching at straws ... MichaelG.
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75RR
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Re: microsystem 70 illumination

#7 Post by 75RR » Thu Mar 22, 2018 3:57 pm

Have you got any details on that LED?
A pdf brochure perhaps as the Cree LEDs have?

I ask because it would be interesting to know its viewing angle and actual size.
... i can adjust the 45/ mirror in the base to centre the stopped down light on the base of the condenser (with iris closed) ...
Does the light from the LED illuminate all of the condenser's iris or just the centre?

The element of my tungsten bulb covers over 80% of the closed condenser's iris, while the element of the my LED which is a bit bigger covers all of it as seen from below using a mirror.
This is because they are about the same size.
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photomicro
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Re: microsystem 70 illumination

#8 Post by photomicro » Thu Mar 22, 2018 4:06 pm

Some of the original bulbs had a frosted end. Is the bulb you show original?

There were several versions of lighting system available for the MS70, as shown in the handbook.

My handbook is physical, and not sure if it is the same as the Little Imp one. I will look.

Mike

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Re: microsystem 70 illumination

#9 Post by apochronaut » Thu Mar 22, 2018 4:27 pm

If you have to move the nosepiece in order to get the led emitter centered, then your illumination beam is off center. Your led housing looks substantial enough, to modify it so it can be centered. Perhaps a slightly oversize collar, where it enters the back of the microscope with 3 nylon thumbscrews in it. Then you could change it's lateral position and angle somewhat.

Moving the registration of the nosepiece is a no-no unless you know it has gotten out of registration. The objective needs to be kept absolutely level so the axis through the optical path is perpendicular to the stage, otherwise the image will be of uneven focus and likely display flare on one side.

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Re: microsystem 70 illumination

#10 Post by stillcool » Thu Mar 22, 2018 4:34 pm

the beam hits the base of the condenser dead centre, tested using the iris fully closed. this was adjusted using the mirror adjustment screws, also swapping back to the bulb produces almost identical results . the led unit is not actually directional and is relying on the optics for focus, intensity etc. as does the bulb.

i may try taking the condenser to bits in case something wrong there.

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Re: microsystem 70 illumination

#11 Post by 75RR » Thu Mar 22, 2018 5:38 pm

If the problem is with both illumination systems then one possibility is that the condenser is seriously off centered.
If you then aimed the light beam at the off centered condenser - both would then be off.
If so, it is likely that attempts to center the condenser from the position it is at with the centering screws, leaves the light beam off centered.
The solution would be to first try and center the condenser as much as you can and then adjust the light beam towards the center of the condenser iris.
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Re: microsystem 70 illumination

#12 Post by apochronaut » Thu Mar 22, 2018 7:43 pm

Ditto on that. Usually microscopes have enough slack in the condenser mounting screws , so that you can center them. I have however seen the odd one where the +- specs of the body, mount, drill holes, yoke and condenser body all conspired to be either all minus or all plus and even with the best of efforts centering was only so so. By the wear on the screws, I could see that others had done their best too.

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Re: microsystem 70 illumination

#13 Post by stillcool » Fri Mar 23, 2018 5:49 am

hmm, the condenser mount itself seems totally solid and undamaged, the adjustment system, springs one side screws the other, also seems free and the adjusters do actually work, they're just offset.

if the condenser adjustment had another 1/2mm movement it would centre.

i think ill strip the condenser in case there is a lens squint or something.

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Re: microsystem 70 illumination

#14 Post by MichaelG. » Fri Mar 23, 2018 6:19 am

stillcool wrote:the beam hits the base of the condenser dead centre, tested using the iris fully closed. this was adjusted using the mirror adjustment screws, also swapping back to the bulb produces almost identical results .
Sorry if this appears negative, but I have a suspicion that this adjustment ^^^ may be the root cause of your problem:
Here is my Logic ... The instrument is specified as using a 'prefocus' bulb; and therefore, I suggest, the mirror adjustment was a 'factory preset' not really intended to be disturbed by the user.
When you adjusted it, to optimise the illumination from your LED, you were compensating for the alignment of the LED, but the better approach would probably have been to to make the torch [flashlight] body tilt-able within its new sleeve.

The 'almost identical' results, seen when you swapped back to the bulb, may show that the filament lamp is more forgiving of slight mis-alignment than the LED.

It's just a hypothesis ... I look forward to the discussion.

MichaelG.
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stillcool
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Re: microsystem 70 illumination

#15 Post by stillcool » Fri Mar 23, 2018 9:27 am

examining the bulb filament in detail shows a plain glass end and flat filament, i doubt there is any directional focus going on there. the led is the same, pointed at a white wall it gives a fairly even "wash" with little variation.

I have a laser colliminator that im going to see if I can mount to get the optics in the base lined up

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Re: microsystem 70 illumination

#16 Post by MichaelG. » Fri Mar 23, 2018 9:52 am

stillcool wrote:examining the bulb filament in detail shows a plain glass end and flat filament, i doubt there is any directional focus going on there. the led is the same ...
Yes, that's what I would expect to see
... it's the 'centration' [for want of a better word] of the LED in its housing that I would be checking first.

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Re: microsystem 70 illumination

#17 Post by Hobbyst46 » Fri Mar 23, 2018 10:52 am

Maybe my experience is irrelevant, and in that case, I apologize in advance!

Recently, on my Zeiss GFL microscope, I noticed an apparent centration problem. The light source (LED retrofit), collector, field aperture are all pre-fixed and cannot be moved. I tried to tamper with the condenser, but that was futile. I finally revealed that the condenser rack movement had a slack due to (as yet unknown) wear. After I replaced the condenser rack the illumination is OK.

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Re: microsystem 70 illumination

#18 Post by apochronaut » Fri Mar 23, 2018 2:51 pm

stillcool wrote:hmm, the condenser mount itself seems totally solid and undamaged, the adjustment system, springs one side screws the other, also seems free and the adjusters do actually work, they're just offset.

if the condenser adjustment had another 1/2mm movement it would centre.

i think ill strip the condenser in case there is a lens squint or something.

Sorry, I didn't realize the microscope had a centerable condenser. Some don't or at least offer two options; a basic non centerable version that must be pre-centered in the mount and a centerable option.

Is it possible you adjusted the mirror while the condenser was fairly off center? That might cause the problem. If you go back and start over, rough adjusting the condenser first by looking down the optical tube with a low power objective. Close the iris and center the iris as close as possible visually, then adjust the mirror second , you might be able to center the beam then. ....just a thought based on a few problems I have had with some well used orphan microscopes.

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Re: microsystem 70 illumination

#19 Post by stillcool » Fri Mar 23, 2018 4:54 pm

very valid point Apo. will try that tomorrow

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