AO 20x comparison

Everything relating to microscopy hardware: Objectives, eyepieces, lamps and more.
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dtsh
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AO 20x comparison

#1 Post by dtsh » Tue Mar 02, 2021 12:51 am

I happen to have in my possession 3 different 20x objectives (34mm infinity) for the American Optical Series 10/20/100/110/120 Series microscopes.
The three objectives are catalog numbers 1022, 1077, and 2556.

In previous attempts to look and compare I had noticed that the 1077 and the 2556 seemed to be close to the same working distance with the 1022 having a slightly longer working distance, which appears to be inconsistent to the documentation.
According to the documentation, the 1022 have a WD of 1.4mm, the 1077 has 0.8mm, and the 2556 is supposed to have 1.5mm. Perhaps I am making some mistake, but it seems to me that the WD for the 2556 is 0.8mm or very close to it as it has a nearly identical working distance as the 1077, both being a little shorter than the 1022.

All objectives yielded a relatively similar FOV. No coverslip was used. The legend on te slide states that each division is 0.01mm.


The images will be presented by catalog number, starting with 1022
20x1022_s.jpg
20x1022_s.jpg (123.75 KiB) Viewed 5460 times

Next is 1077
20x1077_s.jpg
20x1077_s.jpg (125.82 KiB) Viewed 5460 times
And lastly, 2556
20x2556_s.jpg
20x2556_s.jpg (132.88 KiB) Viewed 5460 times

hans
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Re: AO 20x comparison

#2 Post by hans » Wed Mar 03, 2021 2:51 am

Might be worth trying with cover glass to see how much difference it makes for the 1022 and 1077. There is very little difference at 10X 0.25 but the difference is obvious at 40X 0.66. Not sure about 20X 0.5. Do you have any immersion oil? I usually stick a piece of cover glass to the calibration slides with a drop of oil when using them with dry objectives. Before I had immersion oil I used light tool/instrument oil. (Only to stick cover glass to the calibration slide, not for actual immersion objectives.) In this case I think exact refractive index matching should not matter too much because the oil layer is very thin and NA not too high.

hans
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Re: AO 20x comparison

#3 Post by hans » Wed Mar 03, 2021 3:29 am

Regarding working distance, for the objectives that specify 0.17 mm cover glass, it would the clearance between the objective and the surface of the cover glass. Not sure if you were taking that into account already, or if it would be enough to explain the discrepancy you are seeing, though.

dtsh
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Re: AO 20x comparison

#4 Post by dtsh » Wed Mar 03, 2021 4:11 am

hans wrote:
Wed Mar 03, 2021 2:51 am
Might be worth trying with cover glass to see how much difference it makes for the 1022 and 1077. There is very little difference at 10X 0.25 but the difference is obvious at 40X 0.66. Not sure about 20X 0.5. Do you have any immersion oil? I usually stick a piece of cover glass to the calibration slides with a drop of oil when using them with dry objectives. Before I had immersion oil I used light tool/instrument oil. (Only to stick cover glass to the calibration slide, not for actual immersion objectives.) In this case I think exact refractive index matching should not matter too much because the oil layer is very thin and NA not too high.
Good thinking, I'll give it a shot.
hans wrote:
Wed Mar 03, 2021 3:29 am
Regarding working distance, for the objectives that specify 0.17 mm cover glass, it would the clearance between the objective and the surface of the cover glass. Not sure if you were taking that into account already, or if it would be enough to explain the discrepancy you are seeing, though.
I didn't measure the distances for each, but rather was purely comparision. The 1077 and 2556 were nearly equal, I could rotate the turret between the two and the focus was nearly identical; however, for the 1022 I needed to raise turret a little. The docs I have seen stated the 2556 to have a 1.5mm working distance, higher than the other two, but that's not what I found.

I allow it's entirely possible I'm doing something very wrong, but if I am I don't know what it is. I'll try to get some images with a coverslip tomorrow.

hans
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Re: AO 20x comparison

#5 Post by hans » Wed Mar 03, 2021 4:59 am

dtsh wrote:
Wed Mar 03, 2021 4:11 am
The 1077 and 2556 were nearly equal, I could rotate the turret between the two and the focus was nearly identical...
This is establishing that the parfocal distance (nominally 34 mm) is the same. Could try measuring working distance directly using the scale on the fine focus knob while carefully lowering the objective from the focused position until it just touches the cover glass, or calibration slide for the no-cover objective. This diagram might help clarify how the terms are defined:
https://www.olympus-ims.com/en/microsco ... _distance/

apochronaut
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Re: AO 20x comparison

#6 Post by apochronaut » Wed Mar 03, 2021 1:24 pm

The microscope mfg. doesn't have as much control over the production of the glass as they would like. Especially, where the prime ingredients are mined. Where an objective design is made over the course of many years, glass batch differences are bound to occur and the internal shimming of an objective is specific, in order to adjust for those differences. One result of that is a degree of working distance variance and it can be quite large. I happen to have quite a few # 1019 objectives here and one or two have quite a variance in w.d and even with the similar ones, there are few that are the same. This is common for other objectives too. As noted recently, B & L had an adjustment built into their objectives for such.
The lack of a coverslip will also change the w.d. of an objective that is designed to use one and visa versa.

dtsh
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Re: AO 20x comparison

#7 Post by dtsh » Wed Mar 03, 2021 1:43 pm

hans wrote:
Wed Mar 03, 2021 4:59 am
dtsh wrote:
Wed Mar 03, 2021 4:11 am
The 1077 and 2556 were nearly equal, I could rotate the turret between the two and the focus was nearly identical...
This is establishing that the parfocal distance (nominally 34 mm) is the same. Could try measuring working distance directly using the scale on the fine focus knob while carefully lowering the objective from the focused position until it just touches the cover glass, or calibration slide for the no-cover objective. This diagram might help clarify how the terms are defined:
https://www.olympus-ims.com/en/microsco ... _distance/
(smacks hand to forehead) OMG, I understand how parfocal works and what it means, or at least conceptually. Of course that's how it works and I feel a little foolish. Those moments when something you "know" crosses from the realm of conceptual understanding to real-world experience.

I'll do some measurements today, let's see what other cobwebs we can remove from my mind.


Thanks for the info apochronaut.

dtsh
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Re: AO 20x comparison

#8 Post by dtsh » Wed Mar 03, 2021 11:53 pm

Now that I've embarassed myself, let me see if I can at least pull it out of the fire and provide some slightly more accurate information.

For starters, working distance is as reported; facts being what they are, there's one more datapoint in support of me being a fool.

The same objectives, this time with an oiled coverslip.

First up is the 1022
20x1022_s.jpg
20x1022_s.jpg (123.75 KiB) Viewed 5323 times

Next is the 1077
20x1077_s.jpg
20x1077_s.jpg (125.82 KiB) Viewed 5323 times
And lastly, the 2556
20x2556_s.jpg
20x2556_s.jpg (132.88 KiB) Viewed 5323 times

apochronaut
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Re: AO 20x comparison

#9 Post by apochronaut » Thu Mar 04, 2021 12:11 am

That would seem as it should , I would think, relating cover to no cover objectives. The fog starts to form at about .40 and by .50 it's pretty evident. .... There seems to be a bit of pincushion distortion with them all and it is skewed a little...... Camera lens?

dtsh
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Re: AO 20x comparison

#10 Post by dtsh » Thu Mar 04, 2021 3:39 am

apochronaut wrote:
Thu Mar 04, 2021 12:11 am
That would seem as it should , I would think, relating cover to no cover objectives. The fog starts to form at about .40 and by .50 it's pretty evident. .... There seems to be a bit of pincushion distortion with them all and it is skewed a little...... Camera lens?
Camera being a cellphone on an adapter, probably.
I can also see it's in need of cleaning.

hans
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Re: AO 20x comparison

#11 Post by hans » Thu Mar 04, 2021 6:54 pm

I opened the images in tabs to compare while flipping back and forth but they are the same ones as in the first post -- files got mixed up?

dtsh
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Re: AO 20x comparison

#12 Post by dtsh » Thu Mar 04, 2021 7:21 pm

hans wrote:
Thu Mar 04, 2021 6:54 pm
I opened the images in tabs to compare while flipping back and forth but they are the same ones as in the first post -- files got mixed up?
Fail again, yes they are the first ones.
One more time, that's a second datapoint for anyone else counting. :P
In my defense I was in a hurry to get out hte door. I should know better than to try and do something when rushed.

20x 1022 (with coverslip)
20x1022_cs_s.jpg
20x1022_cs_s.jpg (110.31 KiB) Viewed 5241 times
20x 1077 (with coverslip)
20x1077_cs_s.jpg
20x1077_cs_s.jpg (109.51 KiB) Viewed 5241 times
20x 2556 (with coverslip)
20x2556_cs_s.jpg
20x2556_cs_s.jpg (121.35 KiB) Viewed 5241 times

I'm looking into getting things setup with the trinocular tube, but I wanted these through the eyepiece as I was concerned that the cropped image from the trinocular would lose the outer portion of the FOV.

hans
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Re: AO 20x comparison

#13 Post by hans » Mon Mar 08, 2021 7:54 pm

The plan correction of the 1022 relative to the 1077 is pretty obvious, I had been curious about that. Haven't tried any of the 34 mm achromats yet.

apochronaut
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Re: AO 20x comparison

#14 Post by apochronaut » Mon Mar 08, 2021 10:22 pm

dtsh wrote:
Thu Mar 04, 2021 7:21 pm
hans wrote:
Thu Mar 04, 2021 6:54 pm
I opened the images in tabs to compare while flipping back and forth but they are the same ones as in the first post -- files got mixed up?
Fail again, yes they are the first ones.
One more time, that's a second datapoint for anyone else counting. :P
In my defense I was in a hurry to get out hte door. I should know better than to try and do something when rushed.

20x 1022 (with coverslip)
20x1022_cs_s.jpg

20x 1077 (with coverslip)
20x1077_cs_s.jpg

20x 2556 (with coverslip)
20x2556_cs_s.jpg


I'm looking into getting things setup with the trinocular tube, but I wanted these through the eyepiece as I was concerned that the cropped image from the trinocular would lose the outer portion of the FOV.
I have been using the #1054(437) eyepiece in the top of the standard photo tube and setting the sensor corners at the field stop but I have the camera mounted so it can lower and raise on a helical screw, so if wanted, the entire image circle can be put on the sensor.

dtsh
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Re: AO 20x comparison

#15 Post by dtsh » Tue Mar 09, 2021 2:19 am

apochronaut wrote:
Mon Mar 08, 2021 10:22 pm
dtsh wrote:
Thu Mar 04, 2021 7:21 pm
I'm looking into getting things setup with the trinocular tube, but I wanted these through the eyepiece as I was concerned that the cropped image from the trinocular would lose the outer portion of the FOV.
I have been using the #1054(437) eyepiece in the top of the standard photo tube and setting the sensor corners at the field stop but I have the camera mounted so it can lower and raise on a helical screw, so if wanted, the entire image circle can be put on the sensor.
Thank you for that information. I have been beginning to explore in that regard; however it would seem the phototube I have, while it seems to be the right length, it just a bit too narrow for AO eyepieces to fit, though the non-AO ones do fit.
The camera is without a lens, with the 437 eyepiece projecting directly onto the sensor, yes?

apochronaut
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Re: AO 20x comparisones

#16 Post by apochronaut » Tue Mar 09, 2021 12:26 pm

If you mic a range of eyepieces, of various brands they will come out to somewhere between 23.13 to 23.19 . The AO 181 eyepieces are quite narrow at 23.12 usually, with corresponding narrow tubes in the eyepiece ports. Some eyepieces will not fit in them. Older AO eyepieces ; 176 for instance mic. at about 23.15, two examples of # 437 mic. at 23.19. The 176 will just nicely slide in quite tight into a series 400 head, the 437 needs precision and some force to get in.

However, the series 10/20 and 100 photo tube has a rather large eyepiece port at 23.22, so the # 1054/437 focusing eyepiece fits in nicely. That is the only photo tube I know of for those microscopes, available as a factory made version and an aftermarket version : the ones that have the 13/16" photo port.
What kind of photo tube are you referring to?
Last edited by apochronaut on Tue Mar 09, 2021 10:52 pm, edited 2 times in total.

dtsh
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Re: AO 20x comparisones

#17 Post by dtsh » Tue Mar 09, 2021 1:54 pm

apochronaut wrote:
Tue Mar 09, 2021 12:26 pm
If you mic a range of eyepieces, of various brands they will come out to somewhere between 23.13 to 23.19 . The AO 181 eyepieces are quite narrow at 23.12 usually, with corresponding narrow tubes in the eyepiece ports. Some eyepieces will not fit in them. Older AO eyepieces ; 176 for instance mic. at about 23.15, two examples of # 437 mic. at 23.19. The 176 will just nicely slide in quite tight into a series 4 head, the 437 needs precision and some force to get in.

However, the series 10/20 and 100 photo tube has a rather large eyepiece port at 23.17, so the # 1054/437 focusing eyepiece fits in nicely. That is the only photo tube I know of for those microscopes, available as a factory made version and an aftermarket version : the ones that have the 13/16" photo port.
What kind of photo tube are you referring to?
I am certain it is not the tube designed and sold by AO, but it does seem to be the correct length. I'll try to get out into the machine shop and see what I can come up with or see if I can acquire one somewhere.
phototube.jpg
phototube.jpg (101.83 KiB) Viewed 5157 times

apochronaut
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Re: AO 20x comparison

#18 Post by apochronaut » Tue Mar 09, 2021 7:19 pm

I've not seen a photo tube like that before. Aspects of it look to be the real McCoy , though, particularly, the part that fits into the trinocular port. What does the ocular end mic. at?
Note my edit above. I meant series 400 not 4.

dtsh
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Re: AO 20x comparison

#19 Post by dtsh » Tue Mar 09, 2021 9:16 pm

apochronaut wrote:
Tue Mar 09, 2021 7:19 pm
I've not seen a photo tube like that before. Aspects of it look to be the real McCoy , though, particularly, the part that fits into the trinocular port. What does the ocular end mic. at?
Note my edit above. I meant series 400 not 4.
I get 23.19mm with a pair of calipers.
Ah clearer understanding with 400 vs 4 as I have already noticed that in the 400, AO eyepieces (176, 146, 147, 437, etc) are just slightly larger than most everyone else's and thus fit quite tightly.
The black section is an upper and lower that thread together with what appears to be an M24x0.75 thread (could be Imperial).

Edit: I have found that my cheap barlow for the rpi HQ camera fits, so have been exploring a little with that as I learn more in regard to photography.
I also have a C mount tube, DSLR, and a DSLR to C mount adapter, however my first bits of fooling with that I was struggling to get focus acceptable anywhere near parfocal, but I didn't try too hard.

apochronaut
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Re: AO 20x comparison

#20 Post by apochronaut » Tue Mar 09, 2021 11:28 pm

The factory tube is just under 123mm from the shoulder where it rests against the wider part of the port( on a gasket) to the lip. The inside diameter of the eyepiece tube section is 23.22mm.
Parfocality is easy to obtain with the factory tube. What is important to keep in mind with non original tubes is that the angle of the rays inside the tube are such that they can easily reflect off of the interior of a tube that is too narrow causing flare and loss of contrast. There is a known example of an after market tube with that condition, which even though the interior is well blacked, produces a very poor, low contrast image. The problem occurs way down the line, just as the rays enter the tube.
The I.D. of the factory tube at the entrance point is 9/16" but that is just a very thin sub mm lip which acts as a baffle. From there the tube widens out to about 5/8". The interior is flat black.The knock off tube, actually has a wider entrance of 5/8" but it lacks the all important baffle. I have found that an add on baffle can be applied with a bit of flocking. Having a large diameter main tube might help some by ruling out re-reflection but the problem begins at the entrance to the tube and thus ruling out re-reflection would not be a benefit, if there was nothing to reflect in the first place.
I'm not sure how yours was built. Just looking down the tube at any light source will tell you. It should look like the proverbial exit to a train tunnel.

dtsh
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Re: AO 20x comparison

#21 Post by dtsh » Wed Mar 10, 2021 2:30 am

It would appear then that this tube is no bueno, as it is 125.5mm from the shoulder of the flange that rests atop the trinocular port to the top of the eyepiece tube shoulder.
The C mount also apprears to be incorrect according to psneely's site as it is 94.2mm from shoulder to top; the C mount can at least be adapted with an extension.

Looks like it's time for some fabrication.

hans
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Re: AO 20x comparison

#22 Post by hans » Wed Mar 10, 2021 3:35 am

Are these photo tube and eyepiece dimensions generally all the same between the 10 and 110?

apochronaut
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Re: AO 20x comparison

#23 Post by apochronaut » Wed Mar 10, 2021 1:17 pm

dtsh wrote:
Wed Mar 10, 2021 2:30 am
It would appear then that this tube is no bueno, as it is 125.5mm from the shoulder of the flange that rests atop the trinocular port to the top of the eyepiece tube shoulder.
The C mount also apprears to be incorrect according to psneely's site as it is 94.2mm from shoulder to top; the C mount can at least be adapted with an extension.

Looks like it's time for some fabrication.
Which C-mount are you referring to? The 1056T that was made for the 34mm parfocal infinity bodies? I get it at around 103mm. C-mounts are different anyway. They are not made to take a photo eyepiece, so parfocality is determined more by the location of the optic used.
Hans. The actual distance that matters is from the telan lens to the photo lens focal point not the length of the trinocular tube but that shoulder to lip meaurement of the tube is useful as a reference to determine an ideal diy tube length, since the telan lens to the trinocular port shoulder is a fixed distance. Is the telan lens to trinocular port shoulder the same distance for the 10/20 head and the 100 series head? I never measured it but the same trinocular tube is catalogued for each( cat.# 1044).
There is also a dedicated photo tube head, with a built in telan lens of it's own, cat.# 1040. The tube has some vertical adjustment by virtue of releasing three hex set screws in the cast mount and sliding the tube up or down. It works very nice with a teaching bridge.

dtsh
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Re: AO 20x comparison

#24 Post by dtsh » Fri Mar 19, 2021 2:28 pm

I'm down to assembly of a new photo tube, before I finalize everything, can anyone confirm Eldred Spell's measurements (as found on psneeley's site) of 4.861" for the shoulder-to-shoulder length?
My measurement here suggest that it's correct, but it would be nice to have it confirmed by other than just my measurements.

Interestingly, I was initially testing with the 437 eyepiece and found it would come into focus at a different length than reported. Some further bumbling about and it would appear that the focal point for the 437 is slightly higher than the 176, 180, or 184 eyepieces (5.75mm higher (+/-0.25mm) by my measurement). A quick look at the AO Series 10 catalog (1974) lists the 437 and I had read (I know, I know, the internet is always right) that it was the correct projection eyepiece, but I'm a tad confused by this. Can anyone shed some light on this for me?
Last edited by dtsh on Fri Mar 19, 2021 3:12 pm, edited 1 time in total.

Greg Howald
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Re: AO 20x comparison

#25 Post by Greg Howald » Fri Mar 19, 2021 3:02 pm

Ok. I admit it. You folks are way beyond my understanding or ability, but... Since you are being so exacting in what you are trying to do it seems to me that cover glasses can vary in thickness even if they come out of the same container so be sure to use the same cover glass in all tests so that it is a constant instead of an unknown variable. And have fun.
Greg

dtsh
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Re: AO 20x comparison

#26 Post by dtsh » Fri Mar 19, 2021 7:31 pm

Greg Howald wrote:
Fri Mar 19, 2021 3:02 pm
Ok. I admit it. You folks are way beyond my understanding or ability, but... Since you are being so exacting in what you are trying to do it seems to me that cover glasses can vary in thickness even if they come out of the same container so be sure to use the same cover glass in all tests so that it is a constant instead of an unknown variable. And have fun.
Greg
It's the exact same coverglass, the only effective change is rotating the turret and minor adjustment of focus.

Interestingly enough, I discovered today that the 1022 has some delamination. I discovered it by accident, while adjusting the photo tube for focus I glanced down the open tube and saw some specs, my first thought was on the telan lens as I haven't thouroughly cleaned this head, but when I rotated the turret as part of diagnosing, the specs moved with the objective.
I removed the objective and examined it under the stereo and could see what I am 99% certain is delamination in the second lens group up from the bottom. This makes 2 nice objectives I have which need lenses recemented (1311 and now a 1022), so I may try my hand at that once all the other stuff is out of my way. I pulled out a spare 1022 and it appears fine, so I have swapped for the damaged one.

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