MicrobeHunter.com Microscopy Forum

I found a good deal on a LOMO HT-45LU trinocular viewing head with accessories. This was originally made for the LOMO LUMAM scope.
I almost jumped on it, but looking at the specs for the LUMAM, I see that it was an infinity optical system. This means that the trinoc for it would not be a satisfactory optical match for my 160mm systems.
Correct?
CE

generally Correct. Infinity microscopes contain a tube lens, to focus the light of the objective and even if the trinoc head itself does not contain a tube lens, then the distances between the 160 objective and the eyepieces might not be correct. infinity scopes can therefore have a larger objective to eyepiece distance, which is a problem for the fixed 160mm. to make things worse, different companies have different infinity "standards" (maybe the word standard is not even appropriate here, as they are all different). unless, of course, the trinoc head of your brand of microscope is specifically designed to work for both infinity and 160, which I kind of would doubt...
greets, Oliver.

Thanks very much Oliver, I appreciate your input.
CE

Oliver wrote:...
to make things worse, different companies have different infinity "standards" (maybe the word standard is not even appropriate here, as they are all different).
...
greets, Oliver.

'Standards' are a wonderful thing, every manufacturer should have one!

Al

I couldn't resist, went ahead and bought this LOMO trinoc. It came in the customary nice padded wooden case as do most LOMO microscopes and accessories, with various phototubes and camera adapter rings.
The trinoc itself is a beautiful piece of work, all the optics very clean and clear, complete with a pair of bright 10x 18 eyepieces.
The trinoc fits perfectly on the L-2-2, but does require a bit of re focusing as compared to the stock binoc. The LOMO binocs and the HT-30 and MFN-11 trinocs that I have all have a 1.1x magnification factor built into them, this one is straight 1x, making a visual comparison less than perfect, but so far it looks very favorable.
I'll work on some good comparisons and report back as time allows, just on the off chance that someone might be interested.
This might well ultimately prove to be less than a desirable match, but it is a bit of fun, and a nice break while I work on re-aligning my HT-30 mag changer optics.
CE

Is there something you can measure to confirm compatibility?
Do post Photos!

Sometimes an infinity objective would focus on a 160TL scope and produce a decent image. But you have to check with a resolution target. I did with a Klaus Kemp 8 form test slide and checked at NA 0.65, the mismatch combo failed to resolve the Gyrosigma diatom (which is always resolved by a correct combo).

I figured there would be some such resolution test involving diatoms.
Since this is the viewing head and not the objective, would the mismatch effect be as great?
I won't be terribly upset if this doesn't work out, as I am really just playing around. And maybe learning something too.
CE

This might help ... The Mechanical Tube Length - A Short Introduction

http://www.microscopy-uk.org.uk/mag/art ... on%201.pdf

My guess (and it is only a guess) is that if the amount of refocusing needed is less than 1 turn of the fine focus knob, then you're OK. I think what matters is that the objectives are used at their intended working distance.

And now for a little LOMO porn:


Left to right you see the new HT-45 trinoc, the HT-30 trinoc, the binoc that came on the Multiscope, and the original binoc that came on the L-2-2. In the background is the spiffy padded wooden case that the HT-45 came in.



Here is a little better comparison of the HT-30 to the original binoc. You can see how similar they are.



Underside view showing the optical port on each. Note the much larger diameter lens on the HT-45.
Note that the binoc looks stubbier because it has no eyepieces installed, just caps on the ports. I don't have enough eyepieces to go around.

More later.
CE

75RR, thanks for that link, I'll check it out.

Gekko, ah, sadly I'm pretty sure it took more than one full turn of the fine focus knob to bring it into focus after changing from the binoc. I'll try the comparison again and pay closer attention to this. Thanks for the suggestion.

CE

Crater Eddie wrote:Gekko, ah, sadly I'm pretty sure it took more than one full turn of the fine focus knob to bring it into focus after changing from the binoc. I'll try the comparison again and pay closer attention to this. Thanks for the suggestion.
CE

The distance needed to refocus was a pure guess on my part. As far as I know, the important point is that to get the optimum performance from an objective, it should be used at or "very close to" its specified working distance. Tube length may compensate for some small deviations from the specified working distance (I think, but I don't know to what extent). With optics and prisms between the objective and eyepiece, I don't know how one would even measure tube length. Very careful comparison of full resolution images of a detailed object taken with very careful adjustment of the microscope should reveal problems I think. Hopefully someone knowledgeable will chip in. Good luck.

I think that's what zzffnn was getting at with his mention of the diatom resolution test.
CE

Crater Eddie wrote:I think that's what zzffnn was getting at with his mention of the diatom resolution test.
CE

Yes, I agree that would be a good test, much less expensive than a resolution target and quite effective. However, in addition to resolution, you want to look at image quality (such as crispness, lack of spherical aberration), as pure "dot counting" may not give the whole story. Again, I may not know what I'm talking about here.

This bugged me all day, so tonight I had to look into this further. I focused on a white blood cell (on a properly made and stained blood smear slide) with the 20x APO objective and the stock binocular viewing head in place, noting the position of the focus knobs. Switched to the HT-45 trinocular viewing head and noted that it took over two revolutions of the fine focus knob to bring the cell into focus... this brought the slide very close to touching the objective. I think this is as far as I need to take this experiment, this trinoc is clearly not suited to this scope. I knew it was a mismatch, but there is a difference between seeing it on paper and seeing the actual results. Now that I have proven this to myself I can get back to re aligning my other trinoc. I'll put this one back in it's box and store it on the shelf.. who knows, I might find a stand for it some day.
Thanks everyone for the suggestions. Further comments are still welcome.
CE

Talking out of the top of my head (I've never worked with an infinity microscope), I would suspect that there is a slot in the head for inserting filters and the like. Above the slot, there should be a tube lens. If the tube lens is accessible, and if it is easily removable without causing any damage, it may (or may not) be worthwhile to try to remove it (make sure you remember which side is up and which is down so you can replace it correctly) and see if that makes the trinocular head useable. As I said, this is all guesswork on my part so please decide what to do in the light of this admission . Or, better, wait for someone who knows what they're talking about to chip in before doing anything drastic.

That's a good idea gekko, but in this case the slots for the filters and things are built into the stand or frame of the scope where the trinoc mounts. I have thought about swapping the lens assembly in the dovetail with one from one of the binocs, but that doesn't seem to be possible.
CE

I'll put this one back in it's box and store it on the shelf.. who knows, I might find a stand for it some day.

Sounds like an "almost reasonable justification" to get a matching infinity LOMO if one pops up on ebay one day :)

75RR wrote:Sounds like an "almost reasonable justification" to get a matching infinity LOMO if one pops up on ebay one day

The thought had crossed my mind.
CE

Crater Eddie wrote:That's a good idea gekko, but in this case the slots for the filters and things are built into the stand or frame of the scope where the trinoc mounts. I have thought about swapping the lens assembly in the dovetail with one from one of the binocs, but that doesn't seem to be possible.
CE

Oh well, as I said I was just guessing as to how things are arranged. I think 75RR's suggestion is the rational one (I'm always leery of modifying microscopes or microscope parts involving optics. In my ignorance, I would also wonder if you need the specific Lomo model of infinity microscope that the trinocular head you have matches, or whether any Lomo infinity scope would work (if they have more than one model). I don't know the answer to that.