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Infinity objective
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Joaquim F.



Joined: 28 Apr 2010
Posts: 190
Location: Tarragona, Spain

PostPosted: Sun May 02, 2010 5:27 pm    Post subject: Teles Reply with quote

Hello, now I know why the lateral areas in the pictures do not come out as sharp as they should. Rik, thank you very much for the explanation!
In the Nikon literature is recommended a distance of 10 - 20 cm between the microscope objective lens and tube, and warn of image degradation over distance, the problem with the Teles is that it is not known which is the distance to the optical center, may be the position of the diaphragm? but in that case you cannot mount the microscope objective at very much distance without vignetting.
Probably the solution, apart from the original Nikon lens, is using a lens with a standard design, something like an enlarger or process lens?
The diagram from Edmundoptics show a 30mm frontal aperture for the 200mm Nikon tube lens, that is something like a f/6.7 optics, is not necessary a large aperture lens, in my Nikon 200/4 can close to f/8 without great apparent changes in DOF or resolution, and vignetting too with a short extension.

best regards

joaquim
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Last edited by Joaquim F. on Tue May 04, 2010 3:48 pm; edited 2 times in total
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Chris S.
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Location: Ohio, USA

PostPosted: Sun May 02, 2010 9:43 pm    Post subject: Reply with quote

Rik, I'm not sure whether your insightful answer was in response to my post or Chris R.'s, but regardless, thanks for it!

May I apologize for being thick and ask you to enlarge upon your analysis in relation to Figure 2, labeled "Finite and Infinity Optical Systems," at this Website: http://www.microscopyu.com/articles/optics/cfintro.html

In this diagram, the tube lens in the infinity system need have no greater diameter than the infinity objective, which to me makes intuitive sense. And a great many inexpensive lenses should be at their optical best when just that portion is used--it would appear to be quite easy to select a lens with a large enough aperture not to involve using its edge portion.

I'm sure I'm missing something. (And for me the point is moot, since I have a pretty good set of finite objectives--but I always appreciate having my misunderstandings corrected.)

Thanks again,

--Chris S.
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rjlittlefield
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Joined: 01 Aug 2006
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Location: Richland, Washington State, USA

PostPosted: Mon May 03, 2010 12:50 am    Post subject: Reply with quote

Chris S. wrote:
May I apologize for being thick and ask you to enlarge upon your analysis in relation to Figure 2, labeled "Finite and Infinity Optical Systems," at this Website: http://www.microscopyu.com/articles/optics/cfintro.html

Sure -- their illustration is drawn wrong!

In their illustration, different portions of the objective are being used for different points on the object.

If drawn correctly, the entire objective is used for all points on the object. The resulting parallel bundles are all aligned with each other at the exit pupil of the objective, but then diverge from each other in proportion to each object point's distance from the optical axis.

Like this:


My earlier posting was in response to your question, by the way. It's a good question -- produces much insight.

--Rik
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Chris S.
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PostPosted: Mon May 03, 2010 10:30 pm    Post subject: Reply with quote

Thanks, Rik--your explanations are great! That NikonU illustration has been in my head for quite some time--it never seemed quite right, but I didn't see what was wrong with it. Got it, now--thanks again.

--Chris
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rjlittlefield
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PostPosted: Mon May 03, 2010 10:56 pm    Post subject: Reply with quote

Chris, you're very welcome. As I've said before, I learn a lot in trying to write these explanations.

By the way, I have to give credit here to the LINOS Photonics WinLens program. I have found it very valuable in helping to test ideas and to prepare illustrations. The program is fairly simple to use, and since it's in the business of tracing rays instead of fudging to illustrate a concept, it doesn't let me get away with hand-waving arguments.

--Rik
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Pau
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Joined: 20 Jan 2010
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Location: Valencia, Spain

PostPosted: Tue May 04, 2010 9:06 am    Post subject: Reply with quote

Rogelio, I've just bought an infinite nikon 10X 0.30 Mplan, inspired in your tests.
Tank you for pioneering this aproach. When I receive and test it I will post my findings.
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RogelioMoreno



Joined: 20 Nov 2009
Posts: 2962
Location: Panama

PostPosted: Tue May 04, 2010 11:28 am    Post subject: Reply with quote

Joaquim, Chris and Pau thank you.

Last night I did some test with the Nikon CFI60 10/0.25 and the CFN 10/0.3 WI (without the WI tipping).

Single shot (50% crop) with Nikon CFI60 10/0.25 and 110mm between the objective shoulder and the Vivitar 200mm lens:



Single shot (50% crop) with Nikon CFI60 10/0.25 and 50mm between the objective shoulder and the Vivitar 200mm lens:



Single shot (50% crop) with Nikon CFN 10/0.30 WI:


Rogelio
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rjlittlefield
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PostPosted: Tue May 04, 2010 11:52 am    Post subject: Reply with quote

At this scale, I see slight differences in framing and exposure, but nothing that would make me prefer one over another. Are there significant differences when you look closer?

--Rik
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RogelioMoreno



Joined: 20 Nov 2009
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PostPosted: Tue May 04, 2010 2:51 pm    Post subject: Reply with quote

rjlittlefield wrote:
At this scale, I see slight differences in framing and exposure, but nothing that would make me prefer one over another. Are there significant differences when you look closer?

--Rik


Rik, there are not significant differences, a little more small details with the Nikon CFI60 10/0.25 and 110mm between the objective shoulder and the Vivitar 200mm lens.


Rogelio
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rjlittlefield
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PostPosted: Tue May 04, 2010 3:06 pm    Post subject: Reply with quote

Excellent -- the Vivitar not only holds up to a larger gap, but actually seems to work a little better that way. This is very encouraging.

--Rik
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Joaquim F.



Joined: 28 Apr 2010
Posts: 190
Location: Tarragona, Spain

PostPosted: Tue May 04, 2010 4:36 pm    Post subject: Tube lens Reply with quote

Hi, I found this diagram of a zeiss tube lens, it may be as simple as it seems?

http://fermionlattice.wdfiles.com/local--files/zeiss-microscopes/zeisstubelens

Regards

Joaquim
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ChrisLilley



Joined: 01 May 2010
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Location: Nice, France (I'm British)

PostPosted: Mon May 10, 2010 1:46 pm    Post subject: Re: Tube lens Reply with quote

Joaquim F. wrote:
Hi, I found this diagram of a zeiss tube lens, it may be as simple as it seems?

http://fermionlattice.wdfiles.com/local--files/zeiss-microscopes/zeisstubelens
Joaquim


If it is that simple, would an achromatic +5 diopter close up lens (+5D = 200mm) also function as a tube lens?

(Hi. First post. Have been lurking and reading for a couple of weeks).
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rjlittlefield
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PostPosted: Mon May 10, 2010 2:30 pm    Post subject: Re: Tube lens Reply with quote

ChrisLilley wrote:
If it is that simple, would an achromatic +5 diopter close up lens (+5D = 200mm) also function as a tube lens?

Welcome aboard!

It will certainly work to some extent. You might have to reverse it to get best quality, since those lenses are normally designed to have the short conjugate on the front.

I am a little surprised at the simplicity of the Zeiss tube lens. This appears to be a singlet or possibly a cemented doublet (internal surfaces not shown), plus a retaining ring. I wonder if there is more lurking behind the apparent simplicity of the design. Aspheric, perhaps?

--Rik
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ChrisLilley



Joined: 01 May 2010
Posts: 680
Location: Nice, France (I'm British)

PostPosted: Mon May 10, 2010 2:49 pm    Post subject: Reply with quote

I had guessed at an achromatic doublet, since a singlet would surely give significant aberrations. Given the relatively recent date, a moulded aspheric is of course a possibility.

(Thanks for the welcome!)
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Pau
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Joined: 20 Jan 2010
Posts: 4954
Location: Valencia, Spain

PostPosted: Tue May 11, 2010 3:52 pm    Post subject: Reply with quote

Just received and preliminary tested a Nikon CF Plan 10X 0.30 infinity/0 WD 16.5.
Following the Rogelio's setup, I focused it to the camera sensor whith an Olympus OM 200mm f4. The objective was mounted in a Zeiss Standard microscope whithout head and the camera and lens vertically suspended over it.

Here my first test images and findings
http://www.photomacrography.net/forum/viewtopic.php?p=59281#59281

Rick, thanks for your diagrams and explanations: I finally understood what an infinite objective is.
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