Rear projection material for the small-time projectionist.

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BramHuntingNematodes
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Rear projection material for the small-time projectionist.

#1 Post by BramHuntingNematodes » Wed Mar 10, 2021 4:17 am

Always looking for a new way to look at things-- cameras are nice but I like the immediacy of the eyepieces. Projection is something of a compromise. Finding the right screen material, though, was difficult. Screens that are available, even for business conference rooms, are all much too big for my purposes. I'm trying to rig up something like the old TV-type slide viewer. Maybe I should just have gotten one of those old Tasco toys and torn it apart. Anyway, I tried many types of paper, but none were smooth enough or had close to homogenous enough transmission to work. I have settled since on drafting film, which is a kind of plastic paper used for tracing and in technical drawing. It works pretty good!

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Water lily stem cross section


Projection setups are pretty easy to come by, and not just for B&L, although the B&L prisms you see now and then should work for any scope. In fact, the entirety of the optics in the thing are just a porro prism fixed to a flat plate which can tilt over a very small range of motion. With these old scopes, you could easily just tilt the entire setup horizontal and forego the prism, which is exactly how several of the "projection microscopes" of the past worked. Well that and an arc-feed lamp as this application is pretty flux-hungry. The monocular scope excels, as do 5x eyepieces along with 4x-20x objectives.

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1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

BramHuntingNematodes
Posts: 1538
Joined: Tue Jan 21, 2020 1:29 am
Location: Georgia, USA

Re: Rear projection material for the small-time projectionist.

#2 Post by BramHuntingNematodes » Wed Mar 10, 2021 4:37 am

Another thought is that this material would be good to make various diffusion filters
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

MicroBob
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Re: Rear projection material for the small-time projectionist.

#3 Post by MicroBob » Wed Mar 10, 2021 6:52 am

Hi Bram,
the later versions of the Zeiss Lollo boob - projection screen had an oscillating screen surface that reduced the apparent graininess of the image. A good source for a screen surface could be a microfiche reader, they are often scrapped today.
And I see you have an Invertoskop too! What are you doing with it and how do you like it? I recently got one and built a small cabinet with one drawer for it so the eyepieces move up to an acceptable level. I built a condenser lens for it with about 40mm focal length. This makes it usable up to the 40:1 objective.

Bob

MichaelG.
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Re: Rear projection material for the small-time projectionist.

#4 Post by MichaelG. » Wed Mar 10, 2021 7:32 am

Glad to see you found a suitable modern product, Bram

If I recall correctly; Kodatrace was widely specified for such purposes.

MichaelG.
Too many 'projects'

BramHuntingNematodes
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Joined: Tue Jan 21, 2020 1:29 am
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Re: Rear projection material for the small-time projectionist.

#5 Post by BramHuntingNematodes » Wed Mar 10, 2021 5:04 pm

Thanks MicroBob. I'm not exactly clear on how the oscillating screen works-- is it spun in an elliptical path? Maybe a technical drawing would help. I'll try to look it up.

The Invertoscop yeah I got that for $20 a steal even with no optics. I have since built a condenser holder and a light source for it and until recently had the old B&L 60s phase stuff on there. I also acquired some long WD phase lens I think made for Motic and so moved the B&L setup to another Dynoptic I acquired from my old Alma Mater UGA. Since then on the Zeiss I have been fooling around with an old Tiyoda turret condenser and a motley crew of assorted fixed tube length phase lenses trying to see what works. I have made some coverslip-bottom dishes by drilling out some cheap dishes with a forstner bit and then epoxying cover slips underneath the hole. That works well and can support a little colony of critters from the bird bath. Don't use it much for nematode observation, though. It's more of an experimental stand at this point.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

MicroBob
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Re: Rear projection material for the small-time projectionist.

#6 Post by MicroBob » Wed Mar 10, 2021 5:40 pm

The Zeiss projection screen was officially named Glarex. The screen rotated. Here is an image:https://forum.mikroscopia.com/topic/132 ... rex-zeiss/
Apparently they were common in medical routine work. There were different versions for the Standard line and the Phomi and Universal.

BramHuntingNematodes
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Re: Rear projection material for the small-time projectionist.

#7 Post by BramHuntingNematodes » Wed Mar 10, 2021 7:21 pm

Yes it appears J W Gordon wrote about this screen mechanisim in the 1903 JRMS in a review of Helholz:
https://www.biodiversitylibrary.org/ite ... 6/mode/1up
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

Chas
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Re: Rear projection material for the small-time projectionist.

#8 Post by Chas » Wed Mar 10, 2021 10:05 pm

Very nice projector:-)
Re. the inverted slides; there are very large diameter circular coverslips sold on ebay [from China] I bought some and they were pretty clean.

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