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Help Identifying Mitutoyo like objective

 
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aidanmoore



Joined: 24 Sep 2015
Posts: 75
Location: Toronto

PostPosted: Fri Aug 04, 2017 5:07 pm    Post subject: Help Identifying Mitutoyo like objective Reply with quote

Hi,

I recently purchased an eBay microscope with this objective attached. It was not parfocal with the rest of the objectives, so I set up an experiment to find out about the characteristics:

    M26
    just less than 1mm FOV, so probably 20X
    approx 30mm working distance
    seems distortion free on an Eclipse 200 infinity microscope


It has a HUGE front lens for 20X and an enormous working distance. The last picture shows where I had to place my calibration slide on the condenser to get focus on an E200.

I'm wondering what the possibility is that this is a Mitutoyo Plan Apo 20X?

I know there are other Mitutoyo clones, and the WD is not 20mm like I see on eBay, so I'm a bit perplexed.

Would this objective have any use in a macrophotography application?

Thanks Aidan




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Nikon Eclipse 90i Blackmagic 4K studio camera Nikon D5300
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ChrisR
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Joined: 14 Mar 2009
Posts: 8322
Location: Near London, UK

PostPosted: Fri Aug 04, 2017 5:53 pm    Post subject: Reply with quote

Maybe a SLWD?
NA 0.28, WD 30.5:
https://www.edmundoptics.com/microscopy/infinity-corrected-objectives/Mitutoyo-Infinity-Corrected-Long-Working-Distance-Objectives/
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Chris R
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lonepal



Joined: 28 Jan 2017
Posts: 267
Location: Turkey

PostPosted: Sat Aug 05, 2017 5:00 am    Post subject: Reply with quote

I have a 20X and it reallt looks like it but front cover removed.

Edit : But now I realized that it looks like it is shorter than 20X.
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Omer
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Chris S.
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Joined: 05 Apr 2009
Posts: 3243
Location: Ohio, USA

PostPosted: Sat Aug 05, 2017 12:37 pm    Post subject: Reply with quote

Omer, if your 20x is the "regular" one--not the SLWD variant proposed by ChrisR--then the SLWD should, in fact be shorter. The Mitutoyo 20x/0.42 that most of us use is 75mm long, excluding threads; the Mituoyo 20x/0.28 SLWD is 64.5mm long, excluding threads. (Reference)

aidanmoore wrote:
Would this objective have any use in a macrophotography application?

Possibly. If it is indeed a Mitutoyo 20x/0.28 SLWD (or even a decently-made work-alike), and if it has not been bumped in such a way as to ruin it (this occurs sometimes), then very likely you could use it. The caveat is that a 20x/0.28 will have less resolution than the more commonly used 20x/0.42. In the Mitutoyo specifications referenced above, the 0.28 NA lens is said to resolve down to 1.0 micron; the 0.42 lens, 0.7 micron. As a comparison, this particular 20x objective has a numerical aperture more commonly seen on 10x objectives; so it would resolve about the same level of detail as a typical 10x, but magnify it more.

--Chris S.
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aidanmoore



Joined: 24 Sep 2015
Posts: 75
Location: Toronto

PostPosted: Sat Aug 05, 2017 3:09 pm    Post subject: Reply with quote

Hi,

Thanks for the information! I just measured the body as per Chris, and it is exactly 64.50mm lens edge to body end before the threads.

So this does indeed look like a Mitutoyo 20x/0.28 SLWD without the front cover. I'll put this at the end of a Nikon 200mm or 105mm lens and see how it performs with a few stacks.

Thanks again for the clues on how to determine the manufacturer/model.

Aidan
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