3.2x Objective wont focus

[jb89]

Hi guys,

I got a 170/- p 3.2x/0.12 objective for my SM-LUX-POL and I cannot get it to focus how I expected it to.

I found this thread: viewtopic.php?t=7382 when looking for a solution so I tried to remove the intermediate polarizer in the head which allows me to focus the 3.2x objective but when switching objectives they are either too low to use(without plezy adapter) or very very high (with plezy adapter)

My polarized light works with or without the filter I have removed in the head, not sure what it's function is besides maybe moving the image in the tube?

The objective itself has no obvious signs of ever having been opened.

Attached is a picture of the part I have removed.

Also, my 100x objective is not parcentric with my other objectives (off by quite a bit), does anyone know where I can get a tool that would work on the square adjustment lugs? they appear to be 1-2mm but I can't think of anything I would be able to use to adjust them.

[MichaelG.]

Also, my 100x objective is not parcentric with my other objectives (off by quite a bit), does anyone know where I can get a tool that would work on the square adjustment lugs? they appear to be 1-2mm but I can't think of anything I would be able to use to adjust them.

This may be of interest:
http://www.microscopy-uk.org.uk/mag/ind ... tools.html

MichaelG.

[jb89]

MichaelG.,

Perfect! Found the keys individually for practically nothing, those should be here soon!

[MicroBob]

Hi,
these older weak objectives are often not parfocal with the stronger ones of the set. When you've bought an objective that was not intended for you microscope it is possible that the coarse adjustment travel is not long enough to use this objective. I wouldn't start changeing other components when it is just the new objective that doesn't work, or you might mix things up unnecessarily.
Can you post pictures of your microscope and all objectives?

Bob

[jb89]

MicroBob,

Thanks for the info, I was completely unaware that they weren't 100% interchangeable.

Currently I have the following:
Leitz SM-LUX-POL

170/- P 3.2/0.12 w/ plezy adapter
170/- 10/0.25 P
160/0.17 NPL FLUOTAR 25/0.55 P
160/0.17 NPL FLUOTAR 40/0.70 P
170/0.17 P 100/1.30 w/ plezy adapter

I attached the images you requested as well

[MicroBob]

The objectibes with the movable collar and the knurl toward the front lens are "quite modern", same age as the microscope. The thwo other ones are older, but I can't say whether they are actually 45 or 37mm parfocal. The Plezy is used to make 37mm objectives parfocal to 45mm objectives while compensating the added 8mm tube lenght.

Leitz very old:
37mm, 170 tube, 18mm eypiece pickup point
Leitz newer:
45mm, 170mm tube, 18mm eypiece pickup point
Leitz last finity system:
45mm, 160mm tube, 10mm eyepiece pickup point.

The last two types can be used together:
- on a 160mm tube with 10mm eypiece pickup point eyepieces
or:
-on a 170mm tube with 18mm eypiece pickup point eyepieces.

Can you leave the plezy away under your 3,2;1 objective?

Bob

[jb89]

The last two types can be used together:
- on a 160mm tube with 10mm eypiece pickup point eyepieces
or:
-on a 170mm tube with 18mm eypiece pickup point eyepieces.

Can you leave the plezy away under your 3,2;1 objective?

Bob

I am pretty sure the two objectives I have with the double knurl are 37mm which is why I have the plezy adapters, I think they are the same generation/era of objectives
The 100x oil works great.

Using the intermediate polarizer installed-
Without the plezy adapter I can get the 3.2x to focus but I have to move the coarse knob very very far up from where the rest of the objectives would be used.
With the plezy no focus in my adjustment range.

Without pol-
With plezy - fairly high from other objectives
without plezy, other objectives crash into slide

[Hobbyst46]

The length of a 45mm parfocal 100X objective is nearly exactly 45mm. From the shoulder to the front lens.

[jb89]

My 100x is 37mm but has a plezy to bring it to 45mm like the other objectives

The 3.2x will focus without the plezy about 40mm higher than the other objectives

[Hobbyst46]

...The 3.2x will focus without the plezy about 40mm higher than the other objectives

Please bear with a dumb question. Is the 40mm an abbreviation for 40millimeters (4cm) or 40 micrometers? because 40 micrometers is not so bad for parfocality in this case, given the depth of field of a 3.2X objective. 4millimeters would be bad but possible. 40millimeters sounds weird.

[jb89]

4cm, maybe even 5, it is a very very long way from being equal with the rest.

I can try and get measurements when i get home.

I just can't think of what it could be let alone how to fix it(aside from getting a new objective) but I would certainly prefer for that to be a last resort.

[MichaelG.]

The 3.2x will focus without the plezy about 40mm higher than the other objectives

That is fairly typical for a relatively simple low power objective

I can see no reason for adding a plezy to the 3.2x
... was it supplied to you like that, or was this your experimentation ?

MichaelG.

[MicroBob]

As I wrote at the begin of the tread: This might be just normal. If the image is ok and you can live with unconvenience leave it as it is. Newer objectives would be parfocal.

these older weak objectives are often not parfocal with the stronger ones of the set.
Bob

[jb89]

MichaelG., I had just assumed the plezy would be necessary because of the age/style of the objective being the same as my 100x.


MicroBob, I must have misinterpreted what you had said, I also thought that it would have meant that I would have needed the 3.2x closer instead of further away.


Is it possible that I am seeing the image at 3.2x with the 10x eyepieces as opposed to 32x? I didn't think of it until now but when I had the slide under it I could see a much broader field of view than I had expected. I will get some measurements when I get home.

The image is nice but it is wildly inconvenient, I will try to figure it out and verify the functionality the best I can but I will also keep my eyes peeled for a more modern objective ( the P's are pricey).

I really appreciate the help guys, I am an absolute novice with microscopy and I'd be at a complete loss without you!

[Hobbyst46]

Is it possible that I am seeing the image at 3.2x with the 10x eyepieces as opposed to 32x? I didn't think of it until now but when I had the slide under it I could see a much broader field of view than I had expected...

No, the 3.2X is the magnification of the objective itself, irrespective of the eyepiece. With a 10X eyepiece the total mag will be 32X, with a 20X eyepiece the total mag will be 64X, etc. The expected diameter of the FOV of an 3.2X objective is typically 6-7mm.

[jb89]

Alright that sounds about right then, I guess I've just never seen anything very low power magnification so it seemed strange

[MichaelG.]

MichaelG., I had just assumed the plezy would be necessary because of the age/style of the objective being the same as my 100x.


MicroBob, I must have misinterpreted what you had said [ ... ]

Time for some very basic optics, I think ...
The simpler low power objectives can [to a good approximation] be considered a 'thin lens'

Remove the plezy and look into your 3.2x ... I think you will see just one lens at the end of the tube
... I'm not sure of the distance from the mounting to that lens; so it would be helpful if you could roughly measure it.

The basic 'thin lens equation' ( 1/u + 1/v = 1/f ) will then allow you to calculate the nominal working distance.

Note: The modern 'parfocal' low-power objectives contain more lens elements ... because it's a difficult thing to do.

MichaelG.

.
P.S. You might find this useful:
http://www.microscopy-uk.org.uk/mag/art ... on%201.pdf

[MicroBob]

I have an EF 4 objective, a tiny little thing. I can try to test it for parfocality later. The EF series were standarf stuff for your age of microscope but nice semi plan achromats and don't go for much mone when auctioned on ebay. Of cause there is always a dealer who demands silly money for one....
The Zeiss West 3,2 achromat is not as good as the rest of the series. This was probably intended as a cheap seeking objective that had to stay cheap.
This might be the case with your objective too.

@Michael,
thank you for the optics lesson, this way the behaviour of the objective is easier to understand.

Bob

[MicroBob]

I have a "Leica" EF 4 and it is parfocal with 45mm objectives. It is probably the same as the Leitz EF 4.

[Hobbyst46]

I have a very small 3,2 Zeiss (west) objective, very old, very small, RMS thread, total height <20mm including the thread. Possibly achromat. The NA is not marked. Yet, it is parfocal with 45mm DIN objective on my 160mm tube system. The lens is deeply recessed within the barrel, perhaps a single lens as MichaelG suggested or a doublet. But quite useless for me, since I am using the Plan 2.5x0.07. So if anyone is interested in this 3,2X - only for a small shipping fee...

[75RR]

The Zeiss West 3,2 achromat is not as good as the rest of the series. This was probably intended as a cheap seeking objective that had to stay cheap.

Agree with MicroBob, it does however make for a very fine loupe. Perfect for checking that I have managed to clean the objectives and the condenser properly at the end of a session.

[MichaelG.]

... The lens is deeply recessed within the barrel, perhaps a single lens as MichaelG suggested or a doublet. ...

Yes, very probably a doublet [either as two air-spaced elements, or cemented]; but for the purposes of understanding jb89's situation, I would be happy to consider that a single 'thin lens'

MichaelG

[MichaelG.]

So if anyone is interested in this 3,2X - only for a small shipping fee...

That's remarkably generous of you, if it's the same as the one shown by 75RR

MichaelG.
.
https://spectraservices.com/460100-9904.html

[75RR]

So if anyone is interested in this 3,2X - only for a small shipping fee...

That's remarkably generous of you, if it's the same as the one shown by 75RR

MichaelG.
.
https://spectraservices.com/460100-9904.html :o

You would need to hold down two jobs to afford to be a "valued" regular customer ;)

https://www.ebay.co.uk/itm/Zeiss-460100 ... _cvip=true

[Hobbyst46]

Sorry folks, the objective at my disposal is shown below, probably a previous design so older age than the prestigious black one shown by 75RR. What is more, how could I possibly compete with the winning bid of ~7.6 BP, when the shipping fees to many locations in the US/EU is ~ 10$ via EcoPost. Perhaps I could save a few cents by small parcel service instead of EcoPost.
BTW if the "hold down two jobs" etc... was meant to bring me down to earth, I am really sorry - I did not consider myself especially generous, just do not need the objective but had no idea about the true super-low cost of such objectives on eBay. I know that a Zeiss Plan 2.5X can be quite costly.

[75RR]

BTW if the "hold down two jobs" etc... was meant to bring me down to earth, I am really sorry - I did not consider myself especially generous, just do not need the objective but had no idea about the true super-low cost of such objectives on eBay. I know that a Zeiss Plan 2.5X can be quite costly.

The "hold down two jobs" comment was directed at spectraservices' silly pricing!

The auction price on the other hand is very low, as auctioned items sometimes are.

[MicroBob]

[sometimes are.

and sometimes not...

I think the objective is easily woth the shipping cost if someone looks for a simple seeking objective.

BTW: Zeiss may actually have managed to introduce delamination in a doublet design- who nows?

[Hobbyst46]

BTW: Zeiss may actually have managed to introduce delamination in a doublet design- who nows?

Thanks for the reminder, Bob. I checked it with the stereoscope and found that (a) there appear to be two separate lenses/elements in it, and (b) it is neither delaminated or molded. So, the asking price is not a penny less from the lowest official shipping cost of the objective... (2-4$ to the UK, Germany or North America)

The less merry situation is that the question of the OP has remained unanswered as yet...

[jb89]

Sorry for the delay in responding, I had a 24 hour shift at work.

My objective has at least two lenses, (the rear one may be a filter for polarization?)

Assuming the objective is a 37mm parfocal lense I would expect it to focus approximately 37mm from the turret, 8mm shorter than my other objectives but in reality it will only focus about 60mm from the turret leaving the other objectives extremely far off.

I would also expect that adding the plezy would bring it from 8mm short to approximately 45mm parfocality when in actuality I don't have enough range in my coarse focus to bring the objective into focus.

I think it may just be in my best interest to grab a cheap more modern low power objective, strain free at this magnification isn't very important to me I suppose.

The attached images are of my objective and of the point that it is focused properly(without the plezy adapter)

[75RR]

I wonder if it is a stand alone - that is an objective designed to be placed in a single objective nosepiece.