phase contrast centering eyepiece, really required?

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mes0
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phase contrast centering eyepiece, really required?

#1 Post by mes0 » Mon Aug 24, 2015 7:04 pm

Hi all, I picked up a phase contrast kit off ebay today, but it doesn't have a centering telescope...is this actually needed or just a nice thing to have?
Thanks!
Shopping for a nice Scope.

-Currently have monocular olympus students scope.

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gekko
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Re: phase contrast centering eyepiece, really required?

#2 Post by gekko » Mon Aug 24, 2015 7:23 pm

My 2 cents' worth (and I may be uttering heresy here): it is not essential, but very convenient as it enlarges the view of the back focal plane so you can see it better and makes centering easier. With experience, you may not even need to look at the back focal plane of the objective (I find that as you center the annulus more precisely, the [image plane] view gets darker, and the contrast in the image increases). Of course, if your microscope is equipped with a Bertrand lens, then you do not need a centering telescope.

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lorez
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Re: phase contrast centering eyepiece, really required?

#3 Post by lorez » Mon Aug 24, 2015 8:55 pm

My 2 cents' worth (and I may be uttering heresy here): it is not essential, but very convenient as it enlarges the view of the back focal plane so you can see it better and makes centering easier. With experience, you may not even need to look at the back focal plane of the objective (I find that as you center the annulus more precisely, the [image plane] view gets darker, and the contrast in the image increases). Of course, if your microscope is equipped with a Bertrand lens, then you do not need a centering telescope.
I'm going to add a penny to gecko's comments with a couple of comments of my own. It is possible to all gekko says, but the stickler is the experience. You must have a slide that you are familiar with as a reference or a test slide and the best way to get such a slide is by becoming very comfortable with an image that is the result of a perfectly aligned phase set. The only way to get a perfect alignment is with the centering telescope or bertrand lens. A less reliable method is to find a good representative slide and fiddle with the alignment until you get the best image... then get your centering telescope and check your results. My personal preference is the use of the telescope or bertrand lens... do I sometimes take a short cut ?... yes...
(it all depends on my goals)
lorez

mes0
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Re: phase contrast centering eyepiece, really required?

#4 Post by mes0 » Mon Aug 24, 2015 9:18 pm

Thanks guys, that helps.

Working on finding one for ~50.
Shopping for a nice Scope.

-Currently have monocular olympus students scope.

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gekko
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Re: phase contrast centering eyepiece, really required?

#5 Post by gekko » Mon Aug 24, 2015 9:53 pm

Upon reading what I wrote, I realized I didn't make one point clear, that you can look at the back focal plane of the objective directly (without magnification) by removing the eyepiece and squinting down the tube to center the annulus to the phase ring in the objective. A centering telescope just makes the view larger.

mes0
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Re: phase contrast centering eyepiece, really required?

#6 Post by mes0 » Mon Aug 24, 2015 10:07 pm

I'll give it a try once I get the phase contrast set :)
I'll let you know how I make out.

Thanks.
Shopping for a nice Scope.

-Currently have monocular olympus students scope.

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mrsonchus
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Re: phase contrast centering eyepiece, really required?

#7 Post by mrsonchus » Mon Aug 24, 2015 10:32 pm

Hi, I had a phase-contrast equipped Swift Collegiate 'scope and also found that simply peering directly down the eyetube was easily a good enough method of alignment, I found it really rather easy to see and judge.
Personally, whip off the eyepiece and have a look, you'll probably be able to see your adjustments pretty well as you're making them.
Good luck with it. :)
John B

apochronaut
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Re: phase contrast centering eyepiece, really required?

#8 Post by apochronaut » Tue Aug 25, 2015 1:54 pm

Actually, with most eyepieces you can make a telescope by inverting one eyepiece over the one in the adjustable diopter. This should allow you enough focus to get a decent image of the back objective's lenses. Not all eyepieces give a very wide field, some almost a pinhole but huygens work pretty good. Alternately , you can tape a cheap pair of Huygens or Ramsden together and keep the couple handy .

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gekko
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Re: phase contrast centering eyepiece, really required?

#9 Post by gekko » Tue Aug 25, 2015 2:42 pm

Or you can make a centering telescope yourself from two redundant eyepieces (I tried once, but my workmanship was so bad it didn't fit into the eyetube :oops: ):
http://www.microscopy-uk.org.uk/mag/ind ... phase.html

billbillt
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Re: phase contrast centering eyepiece, really required?

#10 Post by billbillt » Tue Aug 25, 2015 5:18 pm

Hi gekko,
I also have tried to make one at home.. I don't have the correct combination of oculars to put one together....
BillT

madmicroscope
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Re: phase contrast centering eyepiece, really required?

#11 Post by madmicroscope » Tue Nov 02, 2021 3:39 am

This is a great discussion. I was able to center my Olympus phase contrast (10, 20, 40) without telescope. Just look into the eye tube without eyepiece. Super easy. It works great!!!!!!!

However, I cannot adjust the 100 one. I guess it should match the 100 oil PL lens. However, I cannot see the bright ring. I guess I must missed something.....

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Re: phase contrast centering eyepiece, really required?

#12 Post by apochronaut » Tue Nov 02, 2021 1:43 pm

Looking down the eyetube is possible but it probably helps a lot if you are short sighted. The rings are very small, and the 100X version very very small, that's why you are having trouble seeing it. They just need to be magnified so a magnifying glass with an appropriate focal length also helps, as does stacking eyepieces. The phase telescope is just a glorified focusable magnifying glass, or I suppose a very short focus telescope.

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Re: phase contrast centering eyepiece, really required?

#13 Post by MicroBob » Tue Nov 02, 2021 2:07 pm

madmicroscope wrote:
Tue Nov 02, 2021 3:39 am
This is a great discussion. I was able to center my Olympus phase contrast (10, 20, 40) without telescope. Just look into the eye tube without eyepiece. Super easy. It works great!!!!!!!

However, I cannot adjust the 100 one. I guess it should match the 100 oil PL lens. However, I cannot see the bright ring. I guess I must missed something.....
Did you use immersion oil on objective and condenser (if n.a. >1)?

Adam Long
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Re: phase contrast centering eyepiece, really required?

#14 Post by Adam Long » Tue Nov 02, 2021 2:47 pm

I got away without one fine for a few months, but there's no going back once you've tried one. You can't be sure it is optimized without one. And once you've tried an Optovar/ bertrand lens there is no going back to the telescope...

crb5
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Re: phase contrast centering eyepiece, really required?

#15 Post by crb5 » Tue Nov 02, 2021 3:38 pm

I found that using an inverted 5x eyepiece over a 10x eyepiece gave reasonable magnification and field of view to act as a centering device. Also, I found that the PVC pipe from an old vacuum cleaner, which had a slight taper, provided just the right diameter for a snug fit over the eyepieces. A 5 inch length of pipe enables the distance between the eyepieces to be adjusted to focus on the back focal plane and elsewhere in the optical chain (and revealed the prism in the trinoc head needed a good clean!).

Sansub2
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Re: phase contrast centering eyepiece, really required?

#16 Post by Sansub2 » Wed Nov 24, 2021 5:10 pm

Hi,

I am wondering whether the phase telescope is really needed in my case. I used a cellphone camera to take the picture below (10x zoom). Given that I haven't used phase telescope before and the online images are limited, I don't have a way to compare to make a decision. It is about 70+$ so just wanted to check whether it is worth it. Can someone please share the image they see through the telescope? Appreciate it.

https://www.flickr.com/photos/194300444@N08/51701421907
Last edited by Sansub2 on Wed Nov 24, 2021 7:57 pm, edited 1 time in total.

dtsh
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Re: phase contrast centering eyepiece, really required?

#17 Post by dtsh » Wed Nov 24, 2021 7:40 pm

Sansub2 wrote:
Wed Nov 24, 2021 5:10 pm
Hi,

I am wondering whether the phase telescope is really needed in my case. I used a cellphone camera to take the picture below (10x zoom). Given that I haven't used phase telescope before and the online images are limited, I don't have a way to compare to make a decision. It is about 70+$ so just wanted to check whether it is worth it. Can someone please share the image they see through the telescope? Appreciate it.


https://www.flickr.com/photos/194300444
Alignment could be better, but here are two images showing aligned and misaligned. The misaligned was exactly as the scope was when I put the condenser back into it, so it's an example taken from reality and not someting deliberately misaligned as an example. This was done with a Betrand lens, which is effectively the same thing as a phase telescope, just built into the scope.
misaligned.jpg
misaligned.jpg (54.33 KiB) Viewed 247 times
aligned.jpg
aligned.jpg (53.29 KiB) Viewed 247 times

Sansub2
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Re: phase contrast centering eyepiece, really required?

#18 Post by Sansub2 » Wed Nov 24, 2021 7:53 pm

Thanks dtsh for the response. Your image looks much clearer and closer than what I get. Is it 10x or 20x objective? Can you please help with 40 and 100 image?

I keep reading about the Betrand lens. I bought a 2x one from aliexpress but it was not much of a help. If I have to buy, can you please let me which one would be better choice - telescope or Bertrand?

dtsh
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Re: phase contrast centering eyepiece, really required?

#19 Post by dtsh » Wed Nov 24, 2021 9:28 pm

Sansub2 wrote:
Wed Nov 24, 2021 7:53 pm
Thanks dtsh for the response. Your image looks much clearer and closer than what I get. Is it 10x or 20x objective? Can you please help with 40 and 100 image?

I keep reading about the Betrand lens. I bought a 2x one from aliexpress but it was not much of a help. If I have to buy, can you please let me which one would be better choice - telescope or Bertrand?
As for Bertrand vs phase telescope, it is my understanding that a Bertrand lens works the same as a phase telescope, but it's designed to work with a particular microscope; mine fits between the head and the body (inifinity system). In general, I think a phase telescope is more useful; not only does it perform the intended purpose, but you can use it in other microscopes as well - something I can't say about the Bertrand. The advantage of the Bertrand, or at least the ones I am familiar with, is that the lens swings in and out of the optical path allowing very quick and easy alignment without looking for or fumbling with other parts. Another nice advantage of the phase telescope is that you can use it to inspect a microscope for delamination, debris, etc by adjusting the telescope (you can do the same with a Bertrand, just it's limited to the scope it's installed on). I have a phase telescope as well that I use with my AO One-Fifty Phase as it does not have a Bertrand. Of the two, if I had neither, I would get a phase telescope as it seems to me a more generally useful tool. I believe my phase telescope is a LOMO; brand doesn't really matter so long as it's the appropriate diameter to match the eyepiece tube. I think I paid around $35.00 for it on eBay after waiting and watching a little while.
It is entirely possible that a Bertrand only works with infinity systems, I don't know as all of my phase microscopes are inifinite tube length.

Here is an image from the 40x, it is much the same only the rings appear to get thinner and thinner as the magnification goes up. My 100x is in storage as I don't often use it, instead optining for 10ph, 20ph, 40ph with 10x plan achromat and a 40x plan fluor.
40x_aligned.jpg
40x_aligned.jpg (35.22 KiB) Viewed 232 times

Sansub2
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Re: phase contrast centering eyepiece, really required?

#20 Post by Sansub2 » Wed Nov 24, 2021 10:03 pm

Thank you so much for taking time and explaining it in detail dtsh. Really appreciate it.

Based on the clear images you have provided, it seems it is a must (not a nice to have) to have a phase telescope. Thanks again to guide me on this. I will look for a good deal to appear in ebay.

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Re: phase contrast centering eyepiece, really required?

#21 Post by BramHuntingNematodes » Thu Nov 25, 2021 3:34 am

In my experimentation with manufacturing phase diaphragms and using several different systems I would say having that having the diaphragm match the phase ring as closely as possible helps minimize artifacts. The apodized phase lenses I believe use an outer ring of neutral density to further reduce halos and require a close match of the ring of light to the outer edge of the phase ring to work correctly. So anything that helps obtain a bit of precision in the positioning is a great help.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

Sansub2
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Re: phase contrast centering eyepiece, really required?

#22 Post by Sansub2 » Fri Nov 26, 2021 6:27 am

Thanks Bram. Have setup search in ebay to get the phase telescope. Hope to get one soon.

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Re: phase contrast centering eyepiece, really required?

#23 Post by farnsy » Sat Nov 27, 2021 7:40 pm

apochronaut wrote:
Tue Nov 02, 2021 1:43 pm
The rings are very small, and the 100X version very very small, that's why you are having trouble seeing it.
I have a hard time getting a good view of my 100X rings even with the phase telescope. Are there higher magnification telescopes or another convenient workaround to make this job easier?

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