Projecting an image *into* the view through a microscope

Beatsy · Post by **Beatsy** » Tue Apr 21, 2020 11:01 pm

On a microscope, assuming a standard upright or a stereo, is it possible to project an image from underneath the specimen such that it is visible and in focus with the specimen (through the eyepiece)? I don't mean projected *onto* the specimen per se as the image should be visible even if the slide is empty at that location. The image must move with the specimen and stay perfectly aligned (designs often larger than the FoV), so I imagine some condenser-like gizmo that is moved with the slide sitting on it's upper surface. I can only spare about 70mm-80mm vertical space under the specimen so it needs to be fairly shallow device physically. There is no need for normal brightfield illumination at the same time (no ordinary condenser fitted). All specimen lighting is EPI and from above or oblique. Having said that, there will be light from the device (projecting the image) anyway. That likely provided by external flat panel under everything. Or EPI with a Janso.

I'm musing on an alternative approach to the microfilm templates and reticle inserts I use for diatom arranging. These, grids and shapes. sit directly under the coverslip the diatoms are being arranged on. By definition the designs sits 0.17mm away from the focal plane (on the other side of the coverslip) and gets a bit too fuzzy for accurate alignment at very high mag (when placing very small diatoms). It's this I'd like to improve.

It would be handy, but not essential, if the gizmo could project the image from a larger design on film at a much reduced size in the specimen focal plane. A "zoomable" design would be heaven, but also not essential and 1:1 is acceptable as I currently make the templates "life size" anyway. It could be slightly more accurate to design and print them larger and reduce when projecting.

Thanks in advance for help and ideas.

Edit: Small details that might help

I expect opaque specimens to block the projected image and semi-transparent ones to dim and/or distort it.

With the stereo (used for general diatom searching, picking and arranging - among other general uses) I have a wide-open optical table under the scope and a large x,y stage sat on that with two or three micromanipulators around it. A device that could sit on the stage to be moved around would be ideal.

I expect parallax differences between eyepieces on the stereo. That's fine, I get them now using templates. I just judge alignment with my dominant eye (only) and keep the area in question at or very near the centre of the FoV when visually checking it.

The other setup is a dedicated Labophot - used for hi-resolution searching and picking from diatom strews, and occasionally for arranging very small forms, or designs that need to be particularly accurately aligned. Only one hydraulic micromanipulator on that There is plenty of room under the stage and quite a lot of travel on the condenser carrier - so said device would have to fit in there. It would be a bonus if it could provide transmitted light too (i.e. be a condenser), but that's not essential.

viktor j nilsson · Post by **viktor j nilsson** » Wed Apr 22, 2020 1:28 am

Why not print the pattern on paper and use a drawing attachment to superimpose it over the specimen?

This link was recently posted over at microbehunter in response to Robert Berdan's question about drawing attachments:
http://www.microscopy-uk.org.uk/mag/art ... hments.pdf

(Sorry if this wasn't relevant, I don't have time to read your question carefully)

Ichthyophthirius · Post by **Ichthyophthirius** » Wed Apr 22, 2020 3:10 am

Hi,

You would have to place the template in one of the specimen conjugate planes. The drawing tube is a good idea. You would have to move the template by hand.

There are two other conjugate planes: the eyepiece diaphragm and the epiilluminator field diaphragm, in black print here: https://www.researchgate.net/profile/Sa ... -front.png

You could try to modify the epi-illuminator to place a translatable microfilm template close to the field aperture.

Or you could see if you can fit it into an eyepiece with a translatable graticule. The idea is do make something like this https://www.meade.com/series-4000-ploss ... additional with an X-Y-adjustable graticule from a microscope eyepiece (needs to be lifted to get to the diaphragm plane) or an eyepiece with disc turret like Zeiss "46 40 75."

In this post https://www.mikroskopie-forum.de/index. ... #msg167270 , a micrometer scale was projected into the microscopic image using a Zeiss photochanger "47 30 51" https://www.mikroskopie-forum.de/index. ... #msg167013

Something similar might be possible using a Zeiss discussion cube with illuminated pointer "47 30 47" https://www.mikroskopie-forum.de/index. ... 1#msg58211

You can use Google translate to read the German posts.

Regards, Ichty

Beatsy · Post by **Beatsy** » Wed Apr 22, 2020 4:44 am

Thanks both, but the projected template *REALLY* has to move with the specimen(s) as the stage is translated. Aligning templates by hand is simply not viable. I know because I tried it.

I may have confused things by saying I don't need "normal brightfield illumination". I meant in the Koehler sense. There *will* be light from the projected template, of course, but I only need that light to see the template. Proper lighting of the forms will come from EPI lighting (in addition to the projected light).

I'm hoping a condenser with a lens in front (or something) to shift the conjugate planes might project a usable image. Much like the filament is projected in critical illumination vs Koehler - but conjugate with the viewing plane at the eyepiece. I can't put the template in any of the usual illumination path places though because it doesn't move with the stage. Hence seeking a "self-contained" solution that can sit between the moving stage and the specimen - and move with the stage, carrying the specimen with it.

Pau · Post by **Pau** » Wed Apr 22, 2020 5:05 am

Hmmm... maybe cutting the microscope in two parts, one containing the illuminator, condenser and stage and the other the objectives, tube and eyepieces and then moving one part relatively to the other one with a solid X-Y system.

It's major surgery -kind of Franskescope- , maybe easier to do with an inverted model. Not a modification I would be able to attempt.

In that case you can place your template at the field aperture level and focus it on the specimen

Ichthyophthirius · Post by **Ichthyophthirius** » Wed Apr 22, 2020 6:02 am

Just a poorly thought-through idea: What about a forensic comparison microscope or something to that same optical effect? https://www.leica-microsystems.com/prod ... ica-fs-cb/ (not this one, obviously)

Template and object imaged at the same magnification and the stages mechanically coupled. Would have the advantage of allowing 1:1 movement of the template.

Otherwise, whenever you image the template, the optics must have a 1x magnification or you can't directly couple template and slide.

Beatsy · Post by **Beatsy** » Wed Apr 22, 2020 6:06 am

Pau wrote:Hmmm... maybe cutting the microscope in two parts, one containing the illuminator, condenser and stage and the other the objectives, tube and eyepieces and then moving one part relatively to the other one with a solid X-Y system.

That's effectively what I have with the stereo. It and the stage are attached separately to an optical table. The microscope optics sit still except for vertical movement when focusing. The stage moves independently in x and y. Manipulators are also separately bolted to the optical table and "reach onto" the specimens on the stage. The whole thing is rock-solid stable thanks to the rigidity of the table top. I just want a kind of "light box" to drop on the stage as a carrier for the slide and to project the template (when it's positioned under the objective of course - it can be moved right out of view when picking forms off a separate keeper slide - for instance).

David Sykes · Post by **David Sykes** » Wed Apr 22, 2020 3:48 pm

Research "aerial image cinematography" or similar.
I played with it many decades ago but not with projected images that small.
A condenser lens near but behind the aerial image focuses the light source into the entrance pupil of the lens so that you get an evenly illuminated field.

David Sykes · Post by **David Sykes** » Sat Apr 25, 2020 2:31 pm

David Sykes wrote:Research "aerial image cinematography" or similar. .

Not surprisingly vast majority of hits are for taking aerial photos.

"aerial image optical printers" is more relevant.
This diagram shows the basic concept :-

https://tinyurl.com/yagxngl7

If the condenser lens was not there the camera would only see the part of the aerial image in line with the projector lens.

Projecting an image into the view through a microscope

Projecting an image into the view through a microscope