Nikon’s emboss contrast

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Rossf
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Nikon’s emboss contrast

#1 Post by Rossf » Mon Mar 22, 2021 4:04 am

I snooped over to Nikon website just out of curiosity-has anyone played with this technique-looks like a simplified Hoffman style contrast-some pics looked good -some had that weird purple/yellow hues that modern Nikon phase optics seem to have from what I’ve seen-no offence to Nikon CFI users intended-might be the camera used-the slider looks pretty simple and uses normal objectives apparently-I can imagine modern microscope companies continuing to simplify certain techniques as long as it does the job adequately for cash strapped labs doing routine work -I reckon that oblique gradient slider concept could be a pretty good cheap contrasting add on if it was made with precise X/Y controls on the condenser-can anyone think any other older contrasting methods that could do with simplification or methods that never saw commercial use that could be revamped into an economical alternative as we continue into a probably further cash strapped future!
Regards ross

hans
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Re: Nikon’s emboss contrast

#2 Post by hans » Wed Mar 24, 2021 3:18 am

Interesting, not much info I could find on the Nikon site though. Did you come across anything more technical about how this works?

MicroBob
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Re: Nikon’s emboss contrast

#3 Post by MicroBob » Wed Mar 24, 2021 7:27 am

Here the sliders can be seen: https://www.google.com/url?sa=i&url=htt ... egUIARDCAQ

Looks like a simple job to make them once one has determined the shapes.

hans
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Re: Nikon’s emboss contrast

#4 Post by hans » Wed Mar 24, 2021 7:27 pm

Ah, I missed the pictures of the sliders later in the brochure. It looks like the same rotatable oblique mask is used on the illumination side for all magnifications, then the other slider between the objective and head has different circular apertures, possibly offset from the optical axis, for each magnification? Presumably that smaller slider would need to be positioned in a conjugate of the condenser/objective aperture planes? I only saw emboss contrast mentioned on inverted stands, perhaps because in that case there is already access to an appropriate conjugate plane due to the extra relay optics between the objective and head?

MicroBob
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Re: Nikon’s emboss contrast

#5 Post by MicroBob » Wed Mar 24, 2021 7:37 pm

I would come to th esame conclusions as you but can't add any real information. To try this on an upright microscope an intermediate tube like an optovar (housing) or DIC intermediate tube or Pol intermediate tube could offer access t o the light path. Also Zeiss DIC sockets could be used.
Since these are all not cheap and the experimentation work not quickly done it is the question how good the outcome can be at best.

hans
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Re: Nikon’s emboss contrast

#6 Post by hans » Wed Mar 24, 2021 7:53 pm

With just an intermediate tube, I think there would still be no additional conjugate plane available between the objective back focal plane and exit pupil above the eyepiece?

Looks like they offer external phase contrast with a turret containing phase rings just below the head on similar stands, which would also require a conjugate of the objective BPF in that location:
https://www.microscope.healthcare.nikon ... ti2-series

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Rossf
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Re: Nikon’s emboss contrast

#7 Post by Rossf » Thu Mar 25, 2021 12:12 am

I noticed to the actual Hoffman modulation style objectives have a rotatable modulation ring-probably easier to align the objective modulator than rotate the condenser slit. Overall some pretty cool convergence of different contrasting methods-always liked the idea of external phase rings like on the original Olympus IMT with its phase stick.no need to double up on objectives and the external ring could come in different variants....
Regards
Just curious MicroBob did you end up sending your unwanted Vannox frame somewhere? If so I bet I cost a bit in postage!

crb5
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Re: Nikon’s emboss contrast

#8 Post by crb5 » Thu Mar 25, 2021 2:44 am

Here is a good summary of the many contrast relief techniques https://www.researchgate.net/publicatio ... Microscopy - enough to keep the DIYers happy for weeks to come. Click Download to get the full article

hans
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Re: Nikon’s emboss contrast

#9 Post by hans » Thu Mar 25, 2021 3:26 am

Are any of those analogous to "emboss"? I only skimmed but didn't see anything resembling the slider between the objective and head shown in the Nikon brochure.

crb5
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Re: Nikon’s emboss contrast

#10 Post by crb5 » Thu Mar 25, 2021 7:33 pm

hans » Wed Mar 24 Are any of those analogous to "emboss"? I only skimmed but didn't see anything resembling the slider between the objective and head shown in the Nikon brochure
There are a lot of variations which are briefly discussed in this article. Their Fig 3A shows a slider in the objective. Also of interest are ways of introducing a mask or phase plate at a plane conjugate to the back focal plane of the objective (pupil projection), which might be of interest to those with microscopes lacking access to the back of the objective. Sections from their article include:

Hoffman modulation contrast One of the so-called ►schlieren
imaging modes. It employs an asymmetric slit diaphragm in the
condenser and a graded-transmittance filter (“modulator”) in the
objective. “Nikon Advanced Modulation Contrast” (NAMC) and
Olympus’s “Relief Contrast” are its near-identical, double-slit variations;
cf. ►relief contrast. Leica’s “Integrated (or Intermediate)
Modulation Contrast” (IMC) allows for the modulator to be easily
removed from the optical path as it is placed outside the objective
(an ►optical-relay setup). A more simple variant, “Emboss Contrast”
has been introduced by Nikon.


Pupil-projection (optical-relay) setup A system in which the objective
back focal plane (approx. the exit pupil in low-power objectives)
is optically relayed (duplicated) to a more accessible location. A
►phase plate may then be placed in an external, detachable unit
rather than in the objective lens itself. This is of advantage when
switching, for example, between total internal reflection fluorescence
(TIRF) and phase-contrast modes as the need to exchange
the objective lens is eliminated. Such systems are offered by Leica
(“Integrated [or Intermediate] Phase Contrast,” IPH) and Nikon,
and used to be available on Zeiss microscopes.

hans
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Re: Nikon’s emboss contrast

#11 Post by hans » Thu Mar 25, 2021 11:03 pm

Ah, should have tried ctrl-f... so presumably the circular apertures in the Nikon emboss "modulator" are offset from the optical axis, since all the other related techniques involve a modulator that is not symmetric around the optical axis? Regarding "pupil projection", I don't think there is an easy way to achieve that for the visual path on any of my microscopes, but I did experiment a while back with my afocal setup with Nikon DX 35mm 1:1.8G lens. In that case at maximum aperture the lens can be moved back just enough to have the pupil approximately at the surface of the first element without too much vignetting. So that gives an option, but camera-only, and there is quite a bit of reduction (~0.15X) going from objective BFP to eyepiece exit pupil which may add difficulty due to the small size of the required masks. Do you have any microscopes where you can access the BFP in the objective or a conjugate?

crb5
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Re: Nikon’s emboss contrast

#12 Post by crb5 » Fri Mar 26, 2021 1:25 am

I also assumed that the apertures in the Emboss Contrast objective slider were offset to give an enhanced oblique effect. In the absence of an objective turret with access to the back of the objectives, I did try sticking some electrical tape over the edge of the back aperture of a 10x objective (as in Axelrod’s schlieren paper: https://link.springer.com/article/10.1007/BF02788132), but it did not seem to improve the shadow effect much over simple oblique illumination with just the offset mask in the condenser filter. So far, the best DIY option I have found is Dodt contrast with a mask sitting on top of the lamp housing to give illumination from one side and a diffuser (translucent scotch tape covered plastic filter) in the condenser filter holder. The diffuser spreads the oblique illumination effect over a wider field of view. Without it, the oblique illumination effect occurs just in a narrow band between the bright field and dark field illumination. Many years ago, when I had access to a Zeiss Axiovert microscope, I did set up another Axelrod classic arrangement (https://www.osapublishing.org/ao/abstra ... 28-24-5237) where a central stop was projected onto the back focal plane of a 1.4 NA objective, to achieve total internal reflection fluorescence (TIRF) excitation by peripheral illumination using a mercury lamp source. However, it is much more efficient to focus a laser beam at the periphery of such an objective to achieve TRIF, and is the basis of commercial systems today.

hans
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Re: Nikon’s emboss contrast

#13 Post by hans » Fri Mar 26, 2021 2:51 am

Yeah in the Axelrod schlieren arrangement I don't really understand the point of adding a flat side to the objective aperture. Seems like an unmodified objective aperture with illumination in an arc gives essentially the same situation as illustrated in fig. 1 except there would be some modulation effect for gradients in the perpendicular direction as well, depending on angular extent of the illumination?

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