Microscope stage Vs objective Y Axis Movement

[houstontx]

On a traditional microscope, what are the pros/cons of having the stage move in y axis vs the objectives/head?

I have two olympus BH2s, one was modified by the lab to allow the objectives/neck/head to move while stage is immobile, similar to the old AO microscopes. My stock BH2 allows the stage to move in y axis.

The modified unit is cut at the base of the "spine", just above the lamp house port, and two springs are installed for stabilization? backlash reduction? I don't know. A block has been inserted under the condenser carrier so that when focused the neck moves up and down. Don't have pics at the moment.

Do macro setup rules apply here? The forum seems to lean towards keeping the subject immobile...but do same rules apply to a microscope?

[Scarodactyl]

Just as a general note, typically vertical is the Z axis in this context.
For microscopy it depends on what is convenient for your subjects and lighting. You typically don't want your lighting to move relative to the subject while shooting a stack, so you can have issues with reflected illumination and a moving subject unless it is also fixed to the stage. That's irrelevant with coaxial or transmitted illumination and thus for many subjects. Being able to move the head usually comes with a larger travel range which is important for photographing thicker things. For my own bh2/bhm I ended up moving over to a hefty olympus stm measuring stand to be able to use longer objectives and focus on thicker subjects.

[Pau]

Tube moving for focus was the original configuration of most compound microscopes but If you put on complex binocular (and trino) heads and cameras the focus mechanics has to move all this mass. This is why the stage focus movement has been the preferred design of most serious microscopes from 1940s to now.

But if what you have is a heavy complex stage, big sample or another reason to have the stage position fixed (micromanipulators, electrodes...) a fixed stage is more convenient. This is the case with many inverted microscopes and upright electrophysiological models and also industrial ones.
Nowadays all major microscope brands have fixed stage models but the "normal" upright ones move the stage (and condenser with it) to focus

With infinite models, because the length of the infinite space is not critical, both stage and tube can be fixed and only move the objective to focus. This is the case with some AO scopes and few more recent models.

[Lou Jost]

It also depends on whether the subject is dry or in liquid. Better to move the optics if the subject is in liquid, so as not to disturb it.

[iconoclastica]

If the stage moves, and with it the condenser, the conjugal plain of the light source cannot remain ath the substage aperture. Why doesn't that matter?

[Pau]

If the stage moves, and with it the condenser, the conjugal plain of the light source cannot remain ath the substage aperture. Why doesn't that matter?

With typical transillumination of transparent specimens mounted in glass slides and Köhler illumination I find two reasons:
- the sample is very thin, usually less than 50 micron and for high NA observation much less, so the variation of the field aperture focus is irrelevant.
For low magnification objectives Köhler is much less relevant and often the microscope can't be configured for it
- The light emerging from the field base in a Köhler configuration is collimated (parallel bundles more or less like in infinite corrected systems) so again small condenser height variations don't alter its character.

If the condenser remained fixed and the stage moved to focus the sample, the much more critical distance between condenser and sample will be affected. This also will alter much more the field diaphragm focus point

[Macro_Cosmos]

I've seen older upright microscopes that allow nosepiece translations. I personally think it's simply cost and weight. Modern upright microscopes with imaging capabilities are expected to carry a trinocular head (~2kg) and various fittings to accept photo-eyepieces and maintain parfocality. The entire assembly with the camera included probably weighs over 5kg, whereas stage and condenser translations involves a weight of around 2-3kg. Additionally, with adjustments at the nosepiece, how would fluorescence be incorporated? While it's definitely possible to implement nosepiece-only Y-axis translation, I don't think it can be done cheaply. Everything must be centred and rigid to ensure an optimal optical lightpath, adjusting just the nosepiece component could bring misalignment problems.

Inverted microscopes are an entirely different matter. I looked into the cost and decided to stay far away, I don't want a diet of dirt and grass

Just my 2 cents.

[pbraub]

The Olympus BX45 and its successor BX46 are modern examples of fixed stage, moving nospiece designs.
There is also an attachmet (WI-NPA) for the BX51/BX61 (and 53, 63) upright that mounts the nosepiece on the stage mount to allow fixed stage designs (used in the water immersion design BX51wi).