Search found 71 matches

by abednego1995
Sat May 30, 2020 5:56 am
Forum: Beginner's corner
Topic: LOMO 2.5 Objective Focusing
Replies: 48
Views: 554

Re: LOMO 2.5 Objective Focusing

Not sure with LOMO, but some manufacturers have different parfocal distances for low power objectives, especially for those under 4x.

Cheers,
John
by abednego1995
Thu May 28, 2020 12:35 am
Forum: Microscopes and optics
Topic: GRIN lenses
Replies: 2
Views: 71

Re: GRIN lenses

Perhaps cost?
Another would probably be field curvature that cant be compensated with the lens itself.

Cheers,
John
by abednego1995
Thu May 28, 2020 12:03 am
Forum: Beginner's corner
Topic: Help! Questions about magnification and the eyepiece.
Replies: 4
Views: 122

Re: Help! Questions about magnification and the eyepiece.

How large is the sensor? If sensor size is available, just divide it by the number of pixels on either axis and you'll get the approximate actual size of each pixel. Next imaging a stage micrometer will get you the total system magnification. A microscope camera should have its pixel size in its spe...
by abednego1995
Wed May 27, 2020 11:19 pm
Forum: Microscopes and optics
Topic: Interference Plane
Replies: 20
Views: 215

Re: Interference Plane

Erm, wouldn't Thorlabs confocal system be a laser scanning confocal?? That's different from a spinning disk confocal.

Ah! Do you have a DM IL??
That slider slot under the head accepting the Hoffman sliders is actually conjugate with the objective BFP...

Cheers,
John
by abednego1995
Wed May 27, 2020 6:47 am
Forum: Microscopes and optics
Topic: Interference Plane
Replies: 20
Views: 215

Re: Interference Plane

Well... in a infinite system with a spinning disk confocal setup you should have the pinhole disk "after" the tube lens (or secondary objective, in Nikon jargon) That pinhole at the primary image plane eliminates light from the other defocused planes and at the same time acts as the illuminating ape...
by abednego1995
Wed May 27, 2020 3:41 am
Forum: Microscopes and optics
Topic: Interference Plane
Replies: 20
Views: 215

Re: Interference Plane

BTW, Nikon does it like this in their "External Phase Contrast" system on their inverted microscopes.
IMG_1642.jpg
IMG_1642.jpg (189.47 KiB) Viewed 155 times
by abednego1995
Wed May 27, 2020 3:26 am
Forum: Microscopes and optics
Topic: Interference Plane
Replies: 20
Views: 215

Re: Interference Plane

The BFP is the Fourier plane of the objective :-) So if the BFP is at the left of L1, it will be relayed to the right of L2. The 4f relay is normally used to Fourier transform the "image" made by the objective by L1, and do a following inverse Fourier transform with L2. If you're relaying the BFP wi...
by abednego1995
Wed May 27, 2020 3:16 am
Forum: Microscopes and optics
Topic: Interference Plane
Replies: 20
Views: 215

Re: Interference Plane

Yes, that 1987 patent would be a valid description of how the U-CPA works. And that 4f relay in the Bertrand position will kind of work... At least the Fourier plane wouldn't be at the center of L1 and L2. If the focal plane f1 to the left of L1 conincides with the objective BFP, the BFP will be rei...
by abednego1995
Wed May 27, 2020 1:29 am
Forum: Microscopes and optics
Topic: Interference Plane
Replies: 20
Views: 215

Re: Interference Plane

>Pete
All manufacturers should publish that BFP location data! Olympus does and as you mention Leitz does... but Nikon doesn't disclose that data (at least on the www.)
by abednego1995
Wed May 27, 2020 1:25 am
Forum: Microscopes and optics
Topic: Interference Plane
Replies: 20
Views: 215

Re: Interference Plane

Yup, the paper from the Zia lab (Fig.1c) illustrates how a 4f-relay is implemented. Fig.1a has a Bertrand lens behind the tube lens, in this case consider the objective+tube lens as a unit functioning as a finite objective. Looking at it in that light will fit in with the 1966 patent by Leitz you sh...
by abednego1995
Tue May 26, 2020 10:45 pm
Forum: Microscopes and optics
Topic: Interference Plane
Replies: 20
Views: 215

Re: Interference Plane

One needs to know where the conjugate planes reside. In your case assuming Koehler illumination is set up, conjugate planes would be like this; light source>condenser iris (condenser side prism interference plane)> objective exit pupil (objective back focal plane, objective side prism interference p...
by abednego1995
Sun Apr 26, 2020 1:51 am
Forum: Microscopes and optics
Topic: A permanent grease for sealed microscope components: Krytox
Replies: 7
Views: 1262

Re: A permanent grease for sealed microscope components: Krytox

Excellent stuff! I just got a 2oz tube of 206, and
it works wonders. I've went as far as relubing most of my objectives with correction collars, no sticking again! (hopefully)

BR,
John
by abednego1995
Mon Apr 13, 2020 3:01 pm
Forum: Illumination Techniques
Topic: Epi DIC woes
Replies: 31
Views: 954

Re: Epi DIC woes

Are the prisms matched to the objective?
Shear amount should be tuned to be a tad under the objective resolution limit.

BR,
John
by abednego1995
Mon Apr 06, 2020 4:49 am
Forum: Microscopes and optics
Topic: DIC Prism Design
Replies: 5
Views: 333

Re: DIC Prism Design

Excellent reference, the original document by Nomarski is rather cryptic (my French is horrible.) Kusaka describes the essence of prism design in the patent. One thing worth noting is Fig.7A-8. The shear amount is physically dictated by the wedge angle alpha (as in Fig.3), and the focal length of th...
by abednego1995
Wed Feb 05, 2020 8:44 am
Forum: Microscopes and optics
Topic: Making my own Leitz Heine oil cap - questions about adhesives and optics
Replies: 26
Views: 7506

Re: Making my own Leitz Heine oil cap - questions about adhesives and optics

With these kind of hemispheric top lenses, you have to consider "how thick" your slide glass will be. Note the tight tolerances for oil DF condensers.

BR,
John
by abednego1995
Mon Jan 27, 2020 2:30 am
Forum: Illumination Techniques
Topic: Making DIC Prisms
Replies: 14
Views: 4134

Re: Making DIC Prisms

Viktor, thank you for the Paolo Pozzi reference. I had some difficulty in determining objective BFPs on my bench so this method is excellent.

BR,
John
by abednego1995
Sun Jan 19, 2020 7:37 am
Forum: Beginner's corner
Topic: Nikon Optiphot Fluorescence illumination - BF?
Replies: 15
Views: 1922

Re: Nikon Optiphot Fluorescence illumination - BF?

Some corrections and follow ups. Finite CF metallurgical objectives (M Plans) by Nikon are tube length(TL) 210mm. TL160mm pre-CF metallurgical objectives exist, but they are the short barreled variety and will have parfocality problems. Regarding the mounting thread, M Plans are RMS so they will mou...
by abednego1995
Fri Dec 27, 2019 5:13 am
Forum: Microscopes and optics
Topic: Objective FN versus Ocular FN - Compound Microscope
Replies: 11
Views: 1302

Re: Objective FN versus Ocular FN - Compund Microscope

The field iris should be set to the smallest FN in the system. If you use a FN22 ocular on a FN26.5 head, it would be FN22. Many heads (and objectives) will allow fields up to nearly 30mm only limited by the ocular tube diameter themselves but whether that periphery would be pretty is a different ma...
by abednego1995
Sun Nov 24, 2019 12:58 am
Forum: Beginner's corner
Topic: Nikon Optiphot replacement bulb
Replies: 9
Views: 1454

Re: Nikon Optiphot replacement bulb

You’ll need a vertical facing filament to fill the aperture at high numerical apertures.

Cheers,
John
by abednego1995
Tue Sep 10, 2019 2:00 am
Forum: Microscopes and optics
Topic: Help for dismantling Leitz objective
Replies: 4
Views: 812

Re: Help for dismantling Leitz objective

That objective has a safety spring nose, so it's essentially a lens holder inside a outer tube pressed against a forward flange with a spring. You have to access the inner lens assembly from the rear (mount side) loosening the ring screws. Though you'll eventually get inside to the elements you susp...
by abednego1995
Tue Sep 10, 2019 1:51 am
Forum: Microscopes and optics
Topic: Optiphot nose piece question
Replies: 13
Views: 1582

Re: Optiphot nose piece question

That reverse revolver adapter is a late addition to the original Optiphot. Though the revolver is reversed, there's no supplemental lenses (neither in the revolver, nor the stand limb) in the Optiphot2,and Labophot2 due to a redesigned thinner limb compared to the original Optiphot. Thus no addition...
by abednego1995
Mon Jul 15, 2019 2:23 am
Forum: Microscopes and optics
Topic: How to make a lambda wave plate?
Replies: 16
Views: 2468

Re: How to make a lambda wave plate?

Try mica. It used to be the material of choice :-)

Cheers,
John
by abednego1995
Tue Jul 02, 2019 1:10 am
Forum: Beginner's corner
Topic: Darkfield - is resolution lost?
Replies: 62
Views: 8611

Re: Darkfield - is resolution lost?

Darkfield is inherently lower resolution than brightfield, and also is not a faithful representation of the specimen image, due to the loss of the zero-order light in the fourier-reconstructed (via interference) final image. Carl Partly agree, partly not. Please correct me if I'm not understanding ...
by abednego1995
Thu Jun 20, 2019 1:58 am
Forum: Camera systems and imaging
Topic: What are higher-magnification projective eyepieces good for?
Replies: 18
Views: 5092

Re: What are higher-magnification projective eyepieces good for?

"Well, why not get a 10x rather than a puny 2.5x when you can!"

I think that's the rationale behind it, and many would eventually come down to lower mags when they realize what resolution is :-)

Cheers,
John
by abednego1995
Sat Jun 15, 2019 9:01 am
Forum: Microscopes and optics
Topic: Focusing by Changing the Tube Length
Replies: 6
Views: 1083

Re: Focusing by Changing the Tube Length

That's exactly how modern inverted microscopes work.
Just shift the revolver plus objectives in relation to the specimen.

As long as the objective exit pupil is within accepting range of the tube lens entrance pupil, the separation between them does nothing with magnification.

Cheers,
John
by abednego1995
Wed Jun 12, 2019 10:43 am
Forum: Illumination Techniques
Topic: dIY DIC
Replies: 38
Views: 10242

Re: dIY DIC

Yup, Viktor, I think your getting that effect in your beforementioned setup. As you mention, in it's most primitive form DIC employs a pinhole condenser. PlasDIC improves on it by using a rectangular slit allowing somewhat higher NA information to pass through (though direction limited). So little i...
by abednego1995
Wed Jun 12, 2019 6:35 am
Forum: Illumination Techniques
Topic: dIY DIC
Replies: 38
Views: 10242

Re: dIY DIC

I had a bit of an email conversation with that seller regarding another plasDIC system he was selling. It , like the older Leitz in this link was a retrofit and a kind of crude one at that. There was a sticker that said DIC on the slider and it was cockeyed. There was no polarizer. He didn't answer...
by abednego1995
Wed Jun 05, 2019 12:21 am
Forum: Microscopy accessories
Topic: Need help, please, identifying accessories.
Replies: 12
Views: 2001

Re: Need help, please, identifying accessories.

The first Leitz unit is a incident illumination unit for the Ultropak. Without the objectives I'm not sure how much it will fetch, but the illuminator itself is quite rare. Nice find.
by abednego1995
Tue May 14, 2019 3:43 am
Forum: Microscopes and optics
Topic: MitutoyoBD Objective Threads
Replies: 3
Views: 1821

Re: MitutoyoBD Objective Threads

Wow, that's great precision there! Wonder if it's sturdy enough to support the heavy BD's when used as an adapter.
by abednego1995
Mon May 13, 2019 1:17 am
Forum: Microscopes and optics
Topic: WYKO Mrau Interferometer Objective
Replies: 1
Views: 942

Re: WYKO Mrau Interferometer Objective

That's interesting, why not use monochromatic light? That would greatly increase band-band contrast, and moreover if using a narrow band filter or source you can easily determine height difference with the wavelength.

Cheers,
John