Re: Have damaged my x40 objective? Advice from sages welcome. The plot thickens....

[billben74]

Hello all,
I have a bad feeling I damaged my x40.
The problem is in the centre of the field of view.
Anyone of the many knowledgable wonderful forum memebers give advice.

Two pics to show the problem.

Light spot in middle of field of view.

20_03_201619_44_420002ProblemImage1_1024.jpg (42.64 KiB) Viewed 10864 times

And again.

20_03_201619_45_170003ProblemImage2_1024.jpg (36.33 KiB) Viewed 10864 times

I see it through the tubes as well as in photos.

If its damaged I'll get a new one.

[lorez]

Your problem is that the condenser is closed too much. Open it slowly and you will see the spot disappear. I have seen similar images on several Chinese microscopes. The spot is from internal reflection.

lorez

[apochronaut]

So: both eyetubes,trinocular tube, as well? and is it still there, if you lower or raise the position of the condenser? i was typing as you were, sending, lorez. i suspect, you have it but I don't think the anomaly is unique to Chinese microscopes.

[billben74]

Will try.
Thanks guys.

[lorez]

I don't think the anomaly is unique to Chinese microscopes.

I agree, apo, but that is the only place I've seen it.

lorez

[billben74]

That seems to be it
Through the tubes its looks like a translucent sand grain.
I had it Kohlered for x10. I can bring it back by closing down the condener aperture and it does seem to be to do with condenser height.

I hadn't noticed it before. But I can get rid of it now.

While I'm here...
I managed to do this as I was using my x100 and was trying to put oil between the condenser and the bottom of the slide (as well as on top of course). To do this I have to raise my condenser high.
I haven't actually used my x100 much or indeed ever in this "proper" way.

Is this the correct procedure as in this doesn't seem very Kohler? Is there something I am missing here?

[apatientspider]

That seems to be it
Through the tubes its looks like a translucent sand grain.
I had it Kohlered for x10. I can bring it back by closing down the condener aperture and it does seem to be to do with condenser height.

I hadn't noticed it before. But I can get rid of it now.

While I'm here...
I managed to do this as I was using my x100 and was trying to put oil between the condenser and the bottom of the slide (as well as on top of course). To do this I have to raise my condenser high.
I haven't actually used my x100 much or indeed ever in this "proper" way.

Is this the correct procedure as in this doesn't seem very Kohler? Is there something I am missing here?

Hi, billben:

I'm certainly not an authority, but your procedure sounds pretty Kohler to me. I don't know what equipment you are using, but if your substage condenser is one that does not require an auxiliary condenser or its top element removed to focus the field iris of your illuminating system in the object plane when using the 10x objective, then you will find that it focuses very close to the bottom of the slide for all powers, 10x and above. You should also find that the condenser focus doesn't need much further adjustment - if any - as you switch to higher power objectives, unless you focus the objective up or down the depth of field appreciably. Of course, you will have to close the field iris some for each increase in objective power; it will be almost completely closed for the 100x objective while the substage condenser iris will be relatively open.

One caveat: while the condenser's top lens will normally be quite close to the bottom of the slide when the field iris is focused in the object plane - normally about a millimeter or less - if it seems to be actually touching the slide or raising it, then you should check the thickness of the slide itself. It may be too thick for that particular condenser - especially if it is a highly corrected one - or there may be too much distance between the bottom of the slide and the upper part of the specimen you are focused on. In that case you will have to use a thinner slide.

Regards,
Jim

[gekko]

To summarize: To use Koehler, with the microscope focused on your object on the slide, (1) close the field diaphragm, (2) adjust condenser height to get edge of field diaphragm in focus (at the same time as your object remains in focus), (3) center your field diaphragm in the field of view by centering your condenser, (4) open the field diaphragm to just clear the field of view. As Jim said above, this would result in the top of your condenser being very close to the bottom of your slide. Adjust the condenser iris for best compromise between resolution and contrast. You should repeat this procedure every time you use a different objective. It takes only a few seconds to do.

[billben74]

OK guys.
Thanks for input.

The plot thickens.

I will show a image that I believe to be the first part of the kohler method (which I do use each time I turn on the microscope).

FirstPartOfKohlerx10objective.jpg (33.12 KiB) Viewed 10803 times

(I would then open the field iris to be just larger than the field of view)

But here is the weird thing. My condenser's lens is not as you describe. I'll show an image:

6mmBelowSlide.jpg (58.28 KiB) Viewed 10803 times

but its hard to take a clear photo. Take it from me the lens is about 6-7mm below the slide.

This is why I felt the need to raise my condenser to apply the immersion oil of the x100.

Now I know that my microscope's condenser is not the one that was originally designed for this microscope.

Mine is an ex demo model and the condenser was swapped, I believe along with the condenser "train" (thing holding the condenser that you can move up and down) to allow me to use a darkfield condenser (as the previous one was a horseshoe? and Brunel didn't have a compatable darkfield condenser)

Is there something wrong with my system?


p.s.

I also start by closing the condenser iris. This is shown here.

closeddowncondenseriris.jpg (72.76 KiB) Viewed 10803 times

If I take an eyepiece out each one of the values, 4,10 etc. corresponds to light cone filling the eyepiece for that objective.
I start at lowest (4) then after the procedure I mention above I turn to x10 and then change this to x20 etc for each objective. Sometimes I mess with this a little I find I can control contrast and sometimes get a better image with the condenser iris smaller than this.

[gekko]

It looks to me that you are doing it perfectlly. I don't think that the fact that your condenser is not the original unit makes much difference as far as I know, since (a) you can get Koehler illumination, (b) you can get the field of view illuminated with your objectives, and (c) you can get the objective apertures illuminated. And you still get a bright spot in the middle of the filed of view? Perhaps someone can chip in with their expert opinion.

[billben74]

Sorry no. The bright spot has gone.
Many thanks to you and apatientspider.

No the "new" problem is that my condenser lens is not very close to my slide.
So I can't got from say x40 --> x100 and simply put some oil on the condenser lens.
The lens is 6-7mm from the slide. That would involve a lot of oil.

From what I understand from you and apatientspider going from x40 --> should involve putting an oil drop below the slide. I can't do this. I need to raise my condenser a fair bit first.
(I realise that you have also to put a drop on the cover slip -> this is fine)
Is this a problem with my system?

[gekko]

Sorry no. The bright spot has gone.
Many thanks to you and apatientspider.

No the "new" problem is that my condenser lens is not very close to my slide.
So I can't got from say x40 --> x100 and simply put some oil on the condenser lens.
The lens is 6-7mm from the slide. That would involve a lot of oil.

From what I understand from you and apatientspider going from x40 --> should involve putting an oil drop below the slide. I can't do this. I need to raise my condenser a fair bit first.
(I realise that you have also to put a drop on the cover slip -> this is fine)
Is this a problem with my system?

I see. I can see the problem. Normally you don't need to use oil between the condenser and the slide even when using an oil immersion objective (my guess is that many people normally don't). For oil immersion objectives, oiling the condenser to the slide allows you to illuminate the objective's aperture more fully to get the maximum resolution, though. There is usually no point in oiling the condenser when using dry objectives (except, perhaps, for darkfield when using the 40x objective). What kind of immersion oil are you using? I usually use Cargille Type A, but in your case, you may want to try Type B for the condenser which is more viscous and more likely to work in your situation. Again, I hope others will chip in with their views.

[lorez]

Can you remove the condenser from the mounting yoke and then take a nice clear photo of the substage ? That may help resolve some of your questions.

lorez

[billben74]

Thanks to everyone for their time.

Substage with condenser removed from yolk. Cool I learnt a new name for part of the microscope. Thanks Lorez.

substageNoCondenser.jpg (92.53 KiB) Viewed 10784 times

An even closer look.

SubstageCloseup.jpg (81.84 KiB) Viewed 10784 times

And in case this is useful

substageCondenserRemovedButVisible.jpg (88.1 KiB) Viewed 10784 times

Hope that gives inspiration

Again, many thanks to all.

[lorez]

Good. That's just what we needed. See the shaft protruding from the top right of the condenser mount ? That's the condenser focus stop and it is adjustable by a small allen screw on the right side of the block. It is spring loaded so you may want to hold it when you slightly loosen the allen screw. The plunger may be properly set by placing the condenser in its yoke and racking it up until is's just below the top surface of the stage and then tightening the allen screw. This should take care of your adjustment issues.

I would not bother with oiling the slide to the condenser because the differences in resolution, if any, will be minimal with your microscope . Also, some condensers are not well sealed and are prone to oil seepage.

lorez

[billben74]

Many thanks Lorez. I'm learning lots today. Names of bits of the microscope and what that condenser stop is for.
Cool.

However the problem isn't that I can't move the condenser to a few mm below the stage ( I can).
The problem is that when I Kohler my condenser it is 6-7mm below the slide.

Now I realise that the prevailing wisdom I'm getting Loraz and gekko is that there is little point to oiling below the slide.
But, I am one of those people who like to try these things for themselves. Or more precisely I once read an article on micscape that basically said that if you don't oil below the slide then you condenser is operating at 0.85/0.9NA and that the value of 1.25 is only valid if you have oiled it. Therefore you objective is running at 0.9 N.A.

Now I don't know if this is true.

But the guy writing the article sure believed it. Sadly I just looked and couldn't find the one I remember reading but I did just find one that agreed with this idea
e.g.
http://www.microscopy-uk.org.uk/mag/ind ... pjoil.html

So at the risk of being awkward:

I would still be interested trying to use see for myself if the image is better with oil above and below or if it doesn't make enough difference that I care.
But I haven't tried.

And there in lies my problem. When kohlered (on my x10/ x40 -> its not quite the same on x10/x40 but its close) the condenser is 6-7mm below the slide. Meaning that to oil it I have to raise it (probably to a non-kohlered position).

Is this a "malfunction" of some sort. Shouldn't the condenser be nearer to at least allow the attempt at oil on both sides?

Sorry if this is annoying.

[gekko]

I understand your desire. But oiling the condenser when using the dry objectives is not normally done and is not useful (just messy). For oil-immersion objectives, as lorez said, you will not gain much if at all, but I understand your desire. The only solution I see is replacing the condenser with one that was designed for your microscope, or you can try using a more viscous immersion oil as I suggested above and see if that would work. You can also glue a "collar" to the top of the condenser to try to hold the oil in place, I guess. Of course, you can also raise the condenser sufficiently to keep the oil from running down, but that would defeat the purpose. Or, the best and easiest way would be if you have a positive lens (say, from non-prescription reading glasses, or a camera close up auxiliary lens or the like), you can put it below the condenser on the field lens. If it is about the right strength (diopter), it should allow you to raise the condenser sufficiently and maintain Köhler illumination.

[75RR]

I would contact Brunel, I suspect they were unaware of this when they adapted the condenser and condenser carrier.

I am with you on this, regardless of whether you decide to regularly oil your condenser to the slide or not, it is something you should be able to do while achieving köhler.

I don't recommend any DIY solutions unless Brunel turns you down flat.

[billben74]

Thanks very much for your input 75RR and gekko.
Will try to contact brunel, but will keep other solutions in mind if need be.

Cool. On a fixing mission. This is good.

[mrsonchus]

Just a thought, the oil between the condenser and slide underside is to exclude air from the light-path and achieve a continuity using an oil to give a continuous light-path of the same (ideally) RI as glass? So, how about a little square of slide-glass, or a series perhaps of circular cover-slips oiled together in a sort of 'optical shim' arrangement and placed (lightly oiled-on) directly onto the condenser's lens, allowing the top of the 'optical shim' to get close enough to the slide's underside to allow oiling the air gap as normal, achieving a continuous litht-path of;
condenser-top-->'optical-shim'-->oil-->slide's underside-->slide glass-->specimen/mountant-->cover-slip-->oil-->x100 objective's lens....

Would this give the same optically-continuous light-path as if the condenser was close enough to be oiled directly to the slide's base and the cover-slip oiled to the x100's lens?

Essentially a kind of 'condenser top lens extension'? Maybe worth a try?

Probably rubbish as I know nothing except that I use my x100 without oiling the condenser and it is superb. but I too have a constant hankering to try oiling the condenser to the slide's underside, just seems so messy whilst I already have superb x100 performance....

Sorry if this is a stupid suggestion....

p.s. Sadly in my experience enquiries of this nature are virtually ignored by Brunel - they never seem to be able to give a definitive answer to such questions and take an age to actually reply in this situation - save yourself the bother & frustration of trying to contact them re this... They're superb in lots of most-important ways but this scenario is familiar to me with them and they're pretty awful in this respect.

[gekko]

I agree with 75RR and John B that the best solution is to get the original condenser for your microscope (John B's idea of a stack of cover glasses and immersion oil is an interesting one and it should work, but it is rather cumbersome and messy if I may say so). Failing to get the right condenser, the next best solution in my opinion is to reduce the focal length of the current condenser by adding a camera close up supplementary lens or equivalent under the condenser as I mentioned above (you can put it in the filter tray below the condenser or rest it on top of the field lens). As an example of the type of thing I have in mind:
http://www.ebay.co.uk/itm/Close-up-lens ... Sw5VFWOizJ
These usually come in sets of 3 or 4 with increasing powers. You can use one or more, depending on how many you need to get the condenser close enough.

[75RR]

p.s. Sadly in my experience enquiries of this nature are virtually ignored by Brunel - they never seem to be able to give a definitive answer to such questions and take an age to actually reply in this situation - save yourself the bother & frustration of trying to contact them re this... They're superb in lots of most-important ways but this scenario is familiar to me with them and they're pretty awful in this respect.

billben74 may not have any luck with Brunel but he should try. This is no small thing. They aught to not only get back to him on this but also fix the problem.
One should not sing the praises of a company that does not respond to inquiries of this nature.
In fact they should come with a warning label. After all their microscopes are not cheap.

[mrsonchus]

I agree with 75RR and John B that the best solution is to get the original condenser for your microscope (John B's idea of a stack of cover glasses and immersion oil is an interesting one and it should work, but it is rather cumbersome and messy if I may say so). Failing to get the right condenser, the next best solution in my opinion is to reduce the focal length of the current condenser by adding a camera close up supplementary lens or equivalent under the condenser as I mentioned above (you can put it in the filter tray below the condenser or rest it on top of the field lens). As an example of the type of thing I have in mind:
http://www.ebay.co.uk/itm/Close-up-lens ... Sw5VFWOizJ
These usually come in sets of 3 or 4 with increasing powers. You can use one or more, depending on how many you need to get the condenser close enough.

Those lenses seem a really simple solution that is also very flexible if they may simply be placed over the field-lens - I may invest in a set of them myself at that price - Thanks Gekko for that idea.

[gekko]

Those lenses seem a really simple solution that is also very flexible if they may simply be placed over the field-lens - I may invest in a set of them myself at that price - Thanks Gekko for that idea.

John B, I'm sure you don't need them for your microscope, but they can be useful as an inexpensive but effective way to convert your regular camera lens into a macro lens (provided, of course, that they are the right size.)

[billben74]

Many thanks again. It is very heart warming to be part of such a helpful community.

I tried doing a huge blob of oil, but the gap was just to big.

I'm afraid I have a similar feeling that John's trepidation about Brunel in this sort of matter .
My basic take on this is that they are overworked, especially Helen who knows the most and can (when she has time) fix most things that can be fixed. She was trying to solve many problems with her swap of the condenser for me and I did get a fair bargin (US people would disagree but we don't have the same second hand market...sadly), well except for the condenser perhaps.

Anyway this will probably not stop me from trying.
One possible compromise approach maybe to see if either of their superior (N.A. 1.3, nikon and aplantic 1.4 zweis) second hand condensers might actually work with mine. I realise this is fraught with possible issues but I may be able to get some answers to questions about if this might work (as I would be proposing to buy, not whine).
As you have all seen my condenser is basic. If I can solve via an upgrade (cheap one, actually) then maybe that might work.
Otherwise I may,
a) go for the camera lens. I don't mind having macro attachments for my canon anyway if they are nice and cheap.
b) apply pressure for an actual fix.
But for b) I'll have to try for a political approach if I want it to actually work.
Start with the purchase angle...


As I have peeked a lot of interest --> thanks all. I'll report back.

On a completley unrelated plus side my school's lab technition was about to chuck out a whole medicine cabinent of lovely, lovely stains that I rescued.
Sudan Black, Neutral Red, Gentitian Violet, malacite green, enough saffarin to last years. And more chrome alum than I know what to do with and even more but I can't remember all of them.
Ahh... lovely lovely stains....

[mrsonchus]

Many thanks again. It is very heart warming to be part of such a helpful community.

....................

I'm afraid I have a similar feeling that John's trepidation about Brunel in this sort of matter .
.............. but we don't have the same second hand market...sadly), well except for the condenser perhaps.
....................


As I have peeked a lot of interest --> thanks all. I report back.

Exactly Bill - the 'UK experience' is somewhat dissimilar to the US I think...
That's the point which gives us here in the UK a slightly pessimistic but realistic (for the UK) take on this - we simply don't have the supply or suppliers over here - all things microscope are hard to find, expensive compared to US prices and scarce - Brunel is one of the very few suppliers we have over here that will even give amateurs such as us the time of day let alone take time to sell us small amounts of equipment and reagents etc - as for spares - in our dreams only sadly....
They have their limitations but Brunel are a very good company indeed - it's all relative, we take what we can get.

p.s. the Chrome-alum may be used to make a very good (i.e. strong) slide-subbing mixture - I made my own a while ago now and it works very well, although now I have moved over to high-spec slides and no longer need to sub them..

[gekko]

a) go for the camera lens. I don't mind having macro attachments for my canon anyway if they are nice and cheap.

Just make sure they match the filter thread of your camera lens . It just occurred to me that if you have a hand magnifier you might try that, at least to get you going or to check the feasibility of the idea (but if it is too powerful, then you may not be able to raise the condenser high enogh without hitting the slide).
Unfortunately, condensers are not usually interchangeable (each manufacturer has their own mechanical arrangement). I don't see why they cannot supply you with the original condenser. Anyway, I don't think that the close-up lens idea (if it gets you going) would result in any image deterioration so you can leave them there permanently (but if someone who reads this thinks otherwise, please correct me!)

[billben74]

Thanks gekko.
The problem is, I believe, that they changed the yoke as well as the condenser.
Or at least the system that held the previous condenser as they had no darkfield condensors that fit the yoke that the microscope had before. So they changed this as well as the condenser.
So both my condenser and my dark field condenser fit this system.
BUt the original won't any more.

I'll look it the camera lens first.