Would this help with fine focus?

[shawngibson]

Having problems making small adjustments. Would this help?

[lorez]

By the scale of your drawing I would say that such a device would interfere with other components on most of my scopes. I have seen that a larger disc attached to the fine focus knob will help achieve your goal.

lorez

[apochronaut]

I agree with lorez that, providing a larger circumference will exert more control and the lever will be cumbersome. What is the exact nature of the problem you are having? Perhaps the system needs repair to the mechanism. Too much backlash or poor lubrication are usually the causes of FF imprecision. If the focus mechanism itself is cheap and has too coarse a mechanism, that is a whole other problem and applying a Rube Goldberg solution , is unlikely to solve it.

[Charles]

I can see how this would assist in fine focus. Zeiss does make the below accessory for rapid coarse focus, which is similar to your design. This is attached to the coarse focus knob which allows a person to rack the stage down to change specimens and then be able to rack it back up quickly back to the correct focus and would be helpful when having to view numerous slides as in thin sections.

Focus assist.jpg (108.65 KiB) Viewed 7615 times

[gekko]

Shawn, if I understand your idea correctly that the problem is just that the "gearing" of the focus movement is "too fast", I think it would work very well. As lorez has pointed out though, I think a shorter "stick" would be more practical (so, at least, it won't poke you in the eye accidentally ). A larger knob would also work, but the advantage of the "stick" is that you can tell by how much you moved the focus by the change in its angle (visually, as well as by feel). However, if, as apochronaut has pointed out, there is backlash or other mechanical problem or lack of precision in the movement, then this may not help, and may in fact prove to be aggravating in use.
Charles, I may be wrong, but the way I understood it was that the focus is already rapid, and Shawn wants to slow it down.

[shawngibson]

Thanks all. I seem not to have selected "Notify me when a reply is posted". Oops.

Gekko is correct. It may only be an Omax scope, but the fine-focus mechanism feels, and seems to be move, very precisely.

The issue is trying to get small slivers of focus for stacking when dealing with objects often the size of a human hair (or indeed, much smaller); I don't have the fine motor skills in my hand to move the knob 'little enough'.

My stacks tend to be anywhere from 25 to 75, and in one case, 142 images. So I need very fine control with the smaller specimens/greater magnifications (which of course imply very shallow DoF).

Based on the advice given, I'll start with a clamp-on knob that is much larger. If that doesn't bring enough control, I'll add a lever that's as long as possible without interfering with any other parts of the microscope.

Thanks for your help:)

Shawn

[gekko]

I was under the wrong impression that you were talking about a stereo scope. But with a "compound"** microscope, the fine focus should be slow enough, and it is usually calibrated, which allows you to know how much you moved it. Do you think that the number of images in your stacks is excessive? I, for one, think so, for the relatively thin objects you have shown. I don't know this for a fact, but I guess that the sampling theorem would apply to spatial frequencies as it does to temporal ones, in which case, if the focus step is half the size of the details that are resolved by the optics, then you don't gain much by taking smaller steps. Also remember that if your ultimate image is the one displayed on the forum, that is, low resolution, then the resolution there can be much less than in the original capture and may reduce the number of focus steps needed. Hopefully someone will correct me if I'm wrong, or will give a better criterion for the optimum focusing step.

**I use quotations because a stereo scope is also compound, so I don't know what a good word for this is: "biological"? a stereo or dissecting scope is also biological, although both are also used to examine other objects. Any suggestions?

[apochronaut]

Not all fine focus mechanisms are the same and some have just too coarse a gearing to do precise stacks. Stacks done with higher N.A. objectives( .5 and up approx.), need mechanisms that can define in 2 micron graduations at least, otherwise detail will be lost.

[lorez]

Not all fine focus mechanisms are the same

Now is a good time to discuss the mechanics of the fine focus. In the case of the microscope being used in this thread there is (what I call) a "screw, lever, pin" train that translates rotational movement of the knob to the vertical movement of the stage ( and in other designs, the body tube ). The fine focus knob is attached to a screw which has moderately coarse threads ( I have not measured them ). As the screw moves back and forth a flange on the shaft actuates a lever. The design of the lever is such that as the arm moves back and forth a shoulder just above the fulcrum moves vertically. There is a pin on the shoulder that engages a socket on the stage mount ( body tube ) and ultimately moves the it vertically. Both the stage mount and body tube are held against the pin by a spring. The wear point on this system is where the pin meets the block. As with every design, there are modifications that improve as well as those that cheapen.

lorez

[apochronaut]

I was under the wrong impression that you were talking about a stereo scope. But with a "compound"** microscope, the fine focus should be slow enough, and it is usually calibrated, which allows you to know how much you moved it. Do you think that the number of images in your stacks is excessive? I, for one, think so, for the relatively thin objects you have shown. I don't know this for a fact, but I guess that the sampling theorem would apply to spatial frequencies as it does to temporal ones, in which case, if the focus step is half the size of the details that are resolved by the optics, then you don't gain much by taking smaller steps. Also remember that if your ultimate image is the one displayed on the forum, that is, low resolution, then the resolution there can be much less than in the original capture and may reduce the number of focus steps needed. Hopefully someone will correct me if I'm wrong, or will give a better criterion for the optimum focusing step.

**I use quotations because a stereo scope is also compound, so I don't know what a good word for this is: "biological"? a stereo or dissecting scope is also biological, although both are also used to examine other objects. Any suggestions?

Technically, a transmitted light microscope is " diasopic" and an incident light microscope is "episcopic". In some old catalogues I have and have seen, they did not use the term stereoscopic microscope. That seems to have come along after the 1930's mostly. The term used was "low power binocular microscope", I suppose to distinguish it from high power binocular microscopes. There doesn't seem to be any rules, Gekko but there are some conventions that seem to be more accepted; compound biological,epi microscope, transmitted light microscope, incident light microscope. Stereo microscope is reserved for one that provides a 3-D view and inspection microscope would be 1/2 the former. I tend to use diascopic, episcopic and stereoscopic.

[shawngibson]

Compound microscope, sorry. So, in a nutshell, my 'fine' tuning is not "fine" at all?

Having said that, if I were to put $4,000 Cdn into a stereo scope (NOT a compound), could I get very good optics, a movable stage, and very fine control of the focusing knobs; and hopefully, some light options, i.e. polarizing?

I find, at this point, life is more interesting at a level which encompasses, say, a drosphila eye, or an entire beetle head. That seems to be the 'scope' which intrigues me.

I'm less interested in tardigrades and blood cells than I thought I was...

[lorez]

If you want to spend $4000 Cdn into a stereo microscope... CALL ME !!!

If you are just getting started you can get a heck of a lot of microscope in the older B&L, Olympus, Nikon, and AO lines for a lot less. Then you can send me the balance for all the good advice.

lorez

[shawngibson]

>>I was under the wrong impression that you were talking about a stereo scope. But with a "compound"** microscope, the fine focus should be slow enough, and it is usually calibrated, which allows you to know how much you moved it.

Many of my issues revolve around placing a small insect on a compound microscope (freshly dead, no cover). There's a tremendous amount of DoF there. when I get to 40x, and sometimes even 10x, my hands can't move in the small manner required.

Clearly I'm using the wrong sort of microscope, no?

[shawngibson]

If you want to spend $4000 Cdn into a stereo microscope... CALL ME !!!

If you are just getting started you can get a heck of a lot of microscope in the older B&L, Olympus, Nikon, and AO lines for a lot less. Then you can send me the balance for all the good advice.

lorez

I'm just getting started, but I have been a photographer and painter for decades, so my eye is good. My microscopic techniques, not so much.

I want to manipulate small, sometimes almost-microscopic, specimens, on a stage, which I can move, and change upper and lower light sources.

Clearly I have no clue what I'm doing yet lol!
Shawn

[lorez]

You can do all that you mention, quite handily, with the scopes I've mentioned. The B&L stereo 7 microscope is a good place to start. Olympus and Nikon also have some great instruments as well. Lighting can be customized to your desires. The LED is offering tons of easy options.

I have a B&L stereo 7 on a boom stand and it is about as versatile as can be. The stand has a long arm and tall post with a large steel table that makes almost any specimen viewable. You do need a lot of bench space. Smaller versions are just as suitable for your goals.

lorez

[gekko]

>>I was under the wrong impression that you were talking about a stereo scope. But with a "compound"** microscope, the fine focus should be slow enough, and it is usually calibrated, which allows you to know how much you moved it.

Many of my issues revolve around placing a small insect on a compound microscope (freshly dead, no cover). There's a tremendous amount of DoF there. when I get to 40x, and sometimes even 10x, my hands can't move in the small manner required.

Clearly I'm using the wrong sort of microscope, no?

If you want to manipulate small critters using a high power microscope [thank you, apochronaut!], I suggest that you consider an inverted microscope, which has advantages for the kind of mamupulation you may be thinking about, yet also had distinct disadvantages relative to an upright high power microscope. Perhaps others will chip in with more informed advice.

[lorez]

Perhaps others will chip in with more informed advice.

I only have an opinion here. I also have a couple of inverted scopes, an AO 1810 and an Olympus CK which I had a good time restoring (repairing), but I find that I can do more with the stereo scopes than I can with the inverted scopes (with the exception of phase contrast) so the stereo scope is my go to choice for the appropriate specimens. I should mention that my main use is to isolate specimens for a closer look with a diascopic upright compound microscope.

lorez

[apochronaut]

$4,000 is enough to expand your equipment to the point where you could have a very complete system that can do most of the conventional microscope applications; in both diasopic and episcopic imaging . You would be busy for years, just learning how to use them well.

There is a very nice AO/Reichert Epistar on ebay right now you could land for about 1,000 CDN. It has almost all the better optics that they offered for that instrument. Missing only the 60x .80 epi.The instrument is in very very good condition. The objectives are all L.W.D. Brightfield and darkfield.
For another 1500.00, you could easily land any number of Diascopic trinocular scopes, with darkfield, phase and possibly D.I.C. too, if you have a patient outlook and wait and watch carefully.
On top of that, you could keep your eyes peeled for a Wild M5A or M3Z, with a transmitted base for 1500.00 or less too and you would be a very happy microscopist, indeed.

[75RR]

If you haven't come across this forum yet you may want to take a look before you "invest" $4000 in anything!

http://www.photomacrography.net/forum