Opening up an objective!

Everything relating to microscopy hardware: Objectives, eyepieces, lamps and more.
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Andrew2007
Posts: 15
Joined: Sat Dec 14, 2019 1:19 pm

Opening up an objective!

#1 Post by Andrew2007 » Thu Aug 27, 2020 11:56 am

Hello

I'm in the process of restoring an old NIkon Model S, I've fixed the fine adjustment nylon gear that was split which I know was a common fault but someone who previously owned the microscope decided to open up one of the objectives and the invidual lenses haven't been fitted correctly as the image is blurred, the brass tube that holds the lenses in place is chewed up so I know someone has been messing with it.

Rather than going through all of the possible permutations in which the lenses can be fitted is there any way to get this information, surely Nikon must have a drawing.

It's a DLL20 - 0.4 objective.

Thanks

apochronaut
Posts: 6272
Joined: Fri May 15, 2015 12:15 am

Re: Opening up an objective!

#2 Post by apochronaut » Thu Aug 27, 2020 12:29 pm

They probably do but objectives are fine tuned for the centering of the elements in a jig and as well need to be adjusted for spherical aberration. Older objectives were for sure shimmed internally and the shim thicknesses are unique to each objective. Unless you were the first person to open the objective up and know the registration of the elements in the objective, you have a poor chance of bringing it back to it's former glory.

abednego1995
Posts: 137
Joined: Thu Dec 15, 2016 6:32 am

Re: Opening up an objective!

#3 Post by abednego1995 » Thu Aug 27, 2020 1:03 pm

The horror! The horror!

Andrew2007
Posts: 15
Joined: Sat Dec 14, 2019 1:19 pm

Re: Opening up an objective!

#4 Post by Andrew2007 » Thu Aug 27, 2020 4:50 pm

apochronaut wrote:
Thu Aug 27, 2020 12:29 pm
They probably do but objectives are fine tuned for the centering of the elements in a jig and as well need to be adjusted for spherical aberration. Older objectives were for sure shimmed internally and the shim thicknesses are unique to each objective. Unless you were the first person to open the objective up and know the registration of the elements in the objective, you have a poor chance of bringing it back to it's former glory.
I must admit that I know very little about the subject, would they rotate each lens in a jig relative to the other lenses in order to give the best performance before inserting them as one assembly into the objective housing?
abednego1995 wrote:
Thu Aug 27, 2020 1:03 pm
The horror! The horror!
I know! :shock: I've got over the shock now, I couldn't use it the way it was. :)

apochronaut
Posts: 6272
Joined: Fri May 15, 2015 12:15 am

Re: Opening up an objective!

#5 Post by apochronaut » Thu Aug 27, 2020 7:10 pm

Yes, the components were rotated to find the ideal center then usually scribed down the side, so in some cases the centering alignment can be registered, if you know what the scribed line was registered to in the barrel, or if you registered it on the way out. Sometimes it makes little difference, sometimes more. The real problem is when the separation shims get lost or rearranged. Two identical objectives can have completely different shim thicknesses between the same two lens cells. Some objectives can have 5 or 6 shims, all of different thicknesses and then another the same might have 2 or 3.
If an objective has been obviously opened and is not working right, then either the problem was not found or repaired or possibly the components tumbled out and the shim sequencing or centration( is that a word ?) were not carefully observed during reassembly.

It helps to have a good working example of an objective that has never been opened to compare one to that has been previosly opened.

Element 56
Posts: 330
Joined: Thu Oct 13, 2016 3:48 pm
Location: Lancaster County, PA

Re: Opening up an objective!

#6 Post by Element 56 » Thu Aug 27, 2020 9:06 pm

Are you positive that it's not just dirty? Maybe the would be repair guy smudged one of the inside lenses during reassembly?

You can find these lenses often enough for little money. I put together a set for less than $100 off eBay. In the meantime if it can't be used you might as well try your hand at a rebuild. It's usually pretty obvious how the lenses should be arranged. Spacers and shims maybe not so much. You will need to do some trial and error fitting but you might find that you can get it usable for the time being.

Kirby

Andrew2007
Posts: 15
Joined: Sat Dec 14, 2019 1:19 pm

Re: Opening up an objective!

#7 Post by Andrew2007 » Sat Aug 29, 2020 9:04 pm

Thanks apochronaut and Element, it's much appreciated. ;)

I certainly don't have anything to lose in trying to assemble it so I'll give that a go.

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