Positive Phase Contrast Objective Phase Plates

Here you can discuss different microscopic techniques and illumination methods, such as Brightfield, Darkfield, Phase Contrast, DIC, Oblique illumination, etc.
Message
Author
User avatar
patta
Posts: 402
Joined: Sun May 10, 2020 6:01 am
Location: Stavanger Norway
Contact:

Re: Positive Phase Contrast Objective Phase Plates

#31 Post by patta » Thu Jul 08, 2021 7:25 am

Read a bit the AO patent
The "rotated annulus" was made of polarizing film - not of birefrengent materials. The retardation is taken care by a successive whole 1/4 wave quartz plate, who retard differently different polarizations. Interference is obtained after a further polarizer, just as in DIC.
The order is (above the objective):
Polarizer; rotated annulus polarizer; 1/4 wave quartz; polarizer.
So they had polarizing plastic film, but not 1/4 plastic plates.

Cost, I don't know, costs can get enormous, even for simple things, if made in small number, or too many managers are involved in the project, or the costumers need it and there is no competition.

It really looks feasible. Also with the annulus made of birefrengent film (once one's sorts out the Jones matrices..). Since there are so many plates (3 polarizer, 1 quartz) a lot of light will get lost and reflected, so poor image, as Bram noted.

microb
Posts: 729
Joined: Wed Mar 27, 2019 6:39 am

Re: Positive Phase Contrast Objective Phase Plates

#32 Post by microb » Mon Jul 12, 2021 1:41 pm

microb wrote:
Wed Jul 07, 2021 4:54 am
If one puts two orthogonal quarter waveplates together
So putting two quarter waveplates together matching fast to slow axis by adding a 90 degree rotation between them is called a compound waveplate. Zero-order compound quarter waveplates are made to control for frequency and temperature. Nothing is mentioned about taking in different polarized angles.

I'm still trying to understand a term and optic for taking in all light (all pol angles) and retarding it by 1/4 wave. Microscope articles just say 1/4 phase retarding material.

microb
Posts: 729
Joined: Wed Mar 27, 2019 6:39 am

Re: Positive Phase Contrast Objective Phase Plates

#33 Post by microb » Mon Jul 12, 2021 2:23 pm

So I think I found something to read through tonight:

https://arxiv.org/ftp/arxiv/papers/1708/1708.05151.pdf

"Previous Zernike phase-plates, for transmission-electron-microscopy (TEM) have always been
made out of carbon. A critical constraint on those phase-plates is their fast degradation during
use. Here, a Zernike phase-plate consisting out of metal is produced and tested for the first time.
For the new aluminium phase-plate, no charging like for the carbon phase-plate is observed.
Under conditions of use, the stability of the aluminium phase-plate, is excellent. For both materials, a distortion in the image’s Fourier-transformation is observed, when inserting the thin-film
into the beam at the back-focal-plane. This distortion is a negative, spatial-frequency dependent
phase-shift, that is not equal to a focus-change. A phase-shift and an increase of contrast, is
observed for the tested phase-plates.
Different types of self-sustaining metal-films are produced with a technique, invented by Janbroers et al. All metal-films, produced at room-temperature, exhibit a polycrystalline structure,
while carbon-films are amorphous. However, a high crystallinity is unfavored, causing distortions
in the image and an increase of electron-scattering in the phase-plate, due to diffraction. Using
cryo-deposition, metal-films are obtained that combine an amorphous structure with beneficial
properties of metals such as lower charging and prolonged durability. Investigations with TEM,
show a great potential of those cryo-films as material for Zernike phase-plates."

microb
Posts: 729
Joined: Wed Mar 27, 2019 6:39 am

Re: Positive Phase Contrast Objective Phase Plates

#34 Post by microb » Mon Jul 12, 2021 2:31 pm

This article uses Zernike zone plates, but gives materials, but this probably just for x-rays:

"The substrate for each of the zone plates was a 100 nm thick silicon nitride membrane
with a plating base consisting of 5 nm chromium and 12 nm gold. H"

https://www.osapublishing.org/DirectPDF ... &mobile=no

User avatar
patta
Posts: 402
Joined: Sun May 10, 2020 6:01 am
Location: Stavanger Norway
Contact:

Re: Positive Phase Contrast Objective Phase Plates

#35 Post by patta » Mon Jul 12, 2021 8:59 pm

Nice find! super-thin metal layers. There are even more other choices of materials, depending on the application:

For sound waves, phase plates can be made of wood. Also birefrengent.
For surface sea waves, phase plates can be made of concrete. Also of sand, but they won't last.
For radio waves, phase plates can be made of copper coils.
Wavy clouds are retarded (or anticipated?) by mountains.
For gravitational waves, phase plates can be made out of galaxies.

microb
Posts: 729
Joined: Wed Mar 27, 2019 6:39 am

Re: Positive Phase Contrast Objective Phase Plates

#36 Post by microb » Tue Jul 13, 2021 12:40 am

patta wrote:
Mon Jul 12, 2021 8:59 pm
For gravitational waves, phase plates can be made out of galaxies.
Well I'm still searching for little bits of galaxy to sputter or cut from a dielectric that give me a visible spectrum Zernike phase plate.

I was hoping some of the papers would have citations back to something but I didn't find anything yet.

User avatar
patta
Posts: 402
Joined: Sun May 10, 2020 6:01 am
Location: Stavanger Norway
Contact:

Re: Positive Phase Contrast Objective Phase Plates

#37 Post by patta » Thu Jul 15, 2021 8:36 am

Yes sputtering galaxies may be challenging... try to look at the manufacturing of diffraction gratings; maybe more details on how-to and materials.
Diffraction grating = phase plate with stripe pattern
And they're usually made for visible light. Holograms can be phase plates too.
Also posts #6 (book link, pag. 87) and #11 plz

Also a note, dielectric = any material (apart from conductors). What matters is just the refractive index and the thickness.
For hard x rays, even metals may behave as dielectrics. (as paper cited previously).
So, any material would do - if you manage to sputter, paint or carve a layer of the right thickness.

The AO Polarnet was a distracting complication. The "candle soot" is a simpler starting point: the soot deposited is a thin layer of dielectric, and at the same time it absorbs some % of the light.

microb
Posts: 729
Joined: Wed Mar 27, 2019 6:39 am

Re: Positive Phase Contrast Objective Phase Plates

#38 Post by microb » Thu Jul 15, 2021 6:41 pm

patta wrote:
Thu Jul 15, 2021 8:36 am
Also posts #6 (book link, pag. 87) and #11 plz
Cool. For some reason I did not see those posts till just now. The forum UI was hiding it from me.

Thanks,
Ted

microb
Posts: 729
Joined: Wed Mar 27, 2019 6:39 am

Re: Positive Phase Contrast Objective Phase Plates

#39 Post by microb » Thu Jul 15, 2021 6:42 pm

hans wrote:
Tue Jul 06, 2021 8:44 pm
This book has a lot of interesting stuff in it.
BramHuntingNematodes wrote:
Mon Jul 05, 2021 11:37 pm
The sample is also assumed to rrtard light by about a quarter wave.
I haven't yet managed to understand the arguments in Bennett's book for why this is true and the "Molecular Expressions" primer and related manufacturer-specific sites don't really explain it in detail. Would be nice to find something in between.
Thanks, Hans. For some reason I did not see those posts till just now. The forum UI was hiding it from me.

Thanks,
Ted

hans
Posts: 986
Joined: Thu May 28, 2020 11:10 pm
Location: Southern California

Re: Positive Phase Contrast Objective Phase Plates

#40 Post by hans » Thu Jul 15, 2021 6:50 pm

patta wrote:
Thu Jul 15, 2021 8:36 am
Diffraction grating = phase plate with stripe pattern
Yes, this is a good analogy, I think.

User avatar
patta
Posts: 402
Joined: Sun May 10, 2020 6:01 am
Location: Stavanger Norway
Contact:

Re: Positive Phase Contrast Objective Phase Plates

#41 Post by patta » Sat Jul 17, 2021 11:43 am

I'm looking at this mad youtube channel
The guy is doing glass etching, photoresist and diffraction plates and much more, with relatively modest equipment, and detailed explanations
https://www.youtube.com/channel/UC26YLK ... TCYxGh8xVQ

BramHuntingNematodes
Posts: 1538
Joined: Tue Jan 21, 2020 1:29 am
Location: Georgia, USA

Re: Positive Phase Contrast Objective Phase Plates

#42 Post by BramHuntingNematodes » Sun Jul 18, 2021 6:13 am

Well, ok that's reasonably sophisticated but here I have some proof of concept of the plastic phase retarding film used to generate phase effects. Here is the phase plate, hastily constructed with a couple of 15mm diameter coverslips and three pieces of the film, the center stripe rotated 90 degrees relative to the outside portion:

Image

I could have been neater there and I think ideally the stripe should be quite a bit more narrow. Here is a look using the phase telescope:
Image

The off-centeredness was not intentional but I also didn't feel that it would hurt. It took a pretty large stripe cut off of the painted diaphragm.

I took some pictures of a sample of polyester fiber, a dramatic phase object. Here too I had severe depreciation of the resolution and general contrast of this objective when inserting the phase plate into its back. Some may work better than others, and this particular objective may not then have been ideal. Also, my ability to take decent cell phone afocal shots is limited. Anyway, two shots, with a single linear polarizer over the light source. The pictures have the polarizer turned 90 degrees from each other.

Image

Image
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

hans
Posts: 986
Joined: Thu May 28, 2020 11:10 pm
Location: Southern California

Re: Positive Phase Contrast Objective Phase Plates

#43 Post by hans » Sun Jul 18, 2021 7:28 pm

Interesting test Bram, definitely looks like there is something going on. To make sure I understand the arrangement... is this film sold specifically as 1/4 wave, or just some random film that happens to be close? So then you have a slit below the condenser to match the strip, and in the phase telescope view that is the really bright part and the dimmer, narrower line to the left of it is some light scattering from the gap between the pieces of film, maybe? And orientations of everything are in 90 degree increments, so, optic axes of film pieces are perpendicular/parallel to the strip, and polarization direction is also either perpendicular or parallel to the strip?

User avatar
patta
Posts: 402
Joined: Sun May 10, 2020 6:01 am
Location: Stavanger Norway
Contact:

Re: Positive Phase Contrast Objective Phase Plates

#44 Post by patta » Sun Jul 18, 2021 8:07 pm

So good! Congratulations, it really seems to work. Less elucubrations, just glue it down!
Can't think anything better or easier. Maybe, with a clean room and a degasser, and several Sundays of patient precise work...

For orientation, here below the simplified "polarnet" from Bennet's book, i think is the same arrangement; the Micoid disk, is Bram's 1/4 film. Apart annulus vs stripe, and the disk placed above the objective; other differences?
Polarnet_basic_Bennet_pag158.jpg
Polarnet_basic_Bennet_pag158.jpg (30.48 KiB) Viewed 7418 times

BramHuntingNematodes
Posts: 1538
Joined: Tue Jan 21, 2020 1:29 am
Location: Georgia, USA

Re: Positive Phase Contrast Objective Phase Plates

#45 Post by BramHuntingNematodes » Sun Jul 18, 2021 8:48 pm

Yes it's 1/4 lambda film from EO. Could probably do a better job with this plate (I looked to find one of the segments still had its prtective covering in place after I had put all the epoxy down and aligned everything, so I tried to pull it out and put it back in as cleanly as I could, introducing the air bubble and who knows what else at least those fibers you see in the first shot are under the plate and not in it), but I wanted to see if would actually function at all. There may be some additional neutral density filtering in the polanret. There is in usual phase contrast.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

BramHuntingNematodes
Posts: 1538
Joined: Tue Jan 21, 2020 1:29 am
Location: Georgia, USA

Re: Positive Phase Contrast Objective Phase Plates

#46 Post by BramHuntingNematodes » Sun Jul 18, 2021 8:53 pm

Oh yeah, also I didn't use an analyzer. That might be a useful addition.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

hans
Posts: 986
Joined: Thu May 28, 2020 11:10 pm
Location: Southern California

Re: Positive Phase Contrast Objective Phase Plates

#47 Post by hans » Sun Jul 18, 2021 9:52 pm

patta wrote:
Sun Jul 18, 2021 8:07 pm
For orientation, here below the simplified "polarnet" from Bennet's book...
Glad you pointed this out, I never noticed polanret was described in that book and didn't think to look when it came up earlier in the thread.
BramHuntingNematodes wrote:
Sun Jul 18, 2021 8:53 pm
Oh yeah, also I didn't use an analyzer. That might be a useful addition.
Abbreviating ZQWP (zonal quarter-wave plate) and ZPOL (zonal polarizer)... so with polarizer and ZQWP you are getting control of phase but not amplitude and would need some additional absorbing layer, but other than metallic thin films the zonal absorption might be difficult to implement without also adding undesired phase shift? From what I've read so far Bennett's book mainly talks about the ZPOL case, and in that case the analyzer (and variable birefringence) is necessary to get independent control of both phase and amplitude via polarization. But Bennett does mention a ZQWP system with 45 degree (rather than 90 degree) rotation between the zones that allows amplitude control, described in paper:
W. G. Hartley - A Variable Phase-Contrast System for Microscopy
In another class of polanret systems for obtaining variable amplitude ratios with a fixed phase difference or with highly restricted variations in the phase difference, both the conjugate and the complementary area are not polarized linearly. A unique system of this class has been described briefly by Hartley (1947). In Hartley's method the micoid disk in Fig. III. 14 consists of two quarter-wave birefringent elements. One of these covers the conjugate area; the other covers the complementary area. The direction of vibration of the fast ray in the conjugate area is fixed at 45° with respect to the direction of vibration of the fast ray in the complementary area. As in Fig. III. 14, a substage polarizer and an analyzer complete the system. Suppose that the transmission direction of the polarizer is made parallel to the direction of vibration of the fast ray in the conjugate area. Then linearly polarized light emerges from the conjugate area whereas circularly polarized light emerges from the complementary area. Rotation of the analyzer varies the transmitted component of the undeviated light only such that the amplitude ratio h falls in the range 0 ≦ h ≦ 1.0. In a similar manner, amplitude ratios in the range 1 ≦ h ≦ ∞ are obtained by rotating the analyzer when the transmission direction of the polarizer is set parallel to the direction of vibration of the fast ray in the complementary area. If only the equivalent of A-type or B-type diffraction plates is wanted, it is advantageous to cement the polarizer into the assembly of the micoid disk.

User avatar
Dmi3n
Posts: 121
Joined: Thu Feb 06, 2020 4:14 pm
Location: Russia, Kaliningrad

Re: Positive Phase Contrast Objective Phase Plates

#48 Post by Dmi3n » Sun Jul 25, 2021 8:59 pm

There also was similar Carl Zeiss Jena device, called Interphako. The principle is relaying objective exit pupil further in order to place phase plate there, so basically it is phase contrast for non-phase objectives. Also there was LOMO КФ-3 device for МИМ-8 metallographic microscope with the same principle. However, these things are WAY harder to manufacture and set-up than conventional Ph objectives. I think that nowadays phase contrast itself is replaced by DIC in serious research so there is really no pount in producing such expensive device for obsolete method.
Gear list:
CZJ NfPk and Polmi A w/ 45mm apo objectives, Phv, Epi Pol, trinocular
Gamma Hungary 3D-condenser
LOMO ОИ-28 Fluorescence Attachment
Set of Leitz Photar macro lens
Nikon D500 DSLR
LOMO МС-2 microtome

BramHuntingNematodes
Posts: 1538
Joined: Tue Jan 21, 2020 1:29 am
Location: Georgia, USA

Re: Positive Phase Contrast Objective Phase Plates

#49 Post by BramHuntingNematodes » Fri Aug 13, 2021 2:41 am

Going to try to work on this a bi this weekend. I have worked up a new gizmo which I hope will help with the plate assembly: a clean box.

Image
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

microb
Posts: 729
Joined: Wed Mar 27, 2019 6:39 am

Re: Positive Phase Contrast Objective Phase Plates

#50 Post by microb » Fri Aug 13, 2021 3:59 am

I think you've been talking about this in another thread.

It sounded like you wanted to add rings on the top lens of some non-PH objectives but do the rings in such a way as to have 50% transparency edges to help hide the phase contrast halo issue.

I was think of putting the rings on a BK7 window, and have a 4F set-up where I could swap or have a turret to swap the phase plates. That seems like an easier first test on materials and 1/4 wave retardations.

BramHuntingNematodes
Posts: 1538
Joined: Tue Jan 21, 2020 1:29 am
Location: Georgia, USA

Re: Positive Phase Contrast Objective Phase Plates

#51 Post by BramHuntingNematodes » Fri Aug 13, 2021 4:15 am

Oh no this is different from the apodizing experiments of another poster. Here we are trying to assemble a phase plate with phase retarding film set at right angles plus polarizing filter on the light source. Proof of concept worked ok now on to refinement.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

microb
Posts: 729
Joined: Wed Mar 27, 2019 6:39 am

Re: Positive Phase Contrast Objective Phase Plates

#52 Post by microb » Fri Aug 13, 2021 5:35 pm

BramHuntingNematodes wrote:
Fri Aug 13, 2021 4:15 am
Oh no this is different from the apodizing experiments of another poster. Here we are trying to assemble a phase plate with phase retarding film set at right angles plus polarizing filter on the light source. Proof of concept worked ok now on to refinement.
Sorry. I should have checked. I thought you were the original poster of that other thread.

Could you post a diagram of what the idea is with the three layers of film? I thought there would be the 25% surrounding rings: inner and outer. And then the middle 50% -- which I guess would also have the 1/4 wave retarder.

microb
Posts: 729
Joined: Wed Mar 27, 2019 6:39 am

Re: Positive Phase Contrast Objective Phase Plates

#53 Post by microb » Fri Dec 03, 2021 11:29 pm

So still trying to figure a way to do phase contrast with standard objectives. This technique uses a beam splitter with a hole punch in a mirror to run two light paths that are merged after a neutral density filter takes half that light and changes its amplitude and phase:
"Although in a conventional Zernike microscope
the amplitude and phase of the reference beam relative to the test beam are fixed, in our system the
amplitude of the reference beam can be adjusted by
the neutral density filter placed before mirror M1,
and the phase of the reference beam can be adjusted
by means of moving the PZT stage."

https://www.researchgate.net/publicatio ... microscope
Attachments
Diagram-of-the-adjustable-phase-contrast-microscope.png
Diagram-of-the-adjustable-phase-contrast-microscope.png (114.12 KiB) Viewed 5337 times

BramHuntingNematodes
Posts: 1538
Joined: Tue Jan 21, 2020 1:29 am
Location: Georgia, USA

Re: Positive Phase Contrast Objective Phase Plates

#54 Post by BramHuntingNematodes » Sat Dec 04, 2021 7:07 am

hmm that's a setup I haven't seen before.

I oughtta get back to this little experiment.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

Post Reply