c-krebs wrote:zzffnn wrote: Any reason why you don't consider the 3 technically more resolving phase systems, such as Leitz Heine/Pv, Reichert Polyphos/Anoptral and Zeiss equivalents? Those are much more rare and expensive than AOs though.
Answered your own question there Fan!
I like phase contrast, have used it in the past (Nikon), but I am not hugely enthusiastic about using it regularly for photography of the type of subjects I like. But every once in a while I wish I had a scope set up for it. I still have the Nikon parts needed, and a very nice Labophot sittiing around but lack the workspace right now. It is just that I really do like that AO 20, and every time I see it languishing in a box I get the urge to set it up again. There is no time urgency here, and I was simply wondering if the components were available (and reasonably priced) if I was patient.
Charles,
Thanks for the link to that older post, and the quote from "apochronaut". Our understanding of the other manufacturers tube lenses is the same with the exception of the Nikon CFi optics, which I am nearly certain do not do any chromatic correction with the tube lens. I'll need to ask him which AO stand he used to try an Olympus objective. I've never tried a 45mm parfocal distance objective in the AO 20 34mm parfocal stand, so I do not know if they will allow focus. Perhaps he used one of the last versions that had the 45mm parfocal distance.
I've done a lot of cross referencing of information, testing components and observing of designs and ever since AO purchased C. Reichert in 1962, there has been a reasonably consistent development of the infinity corrected system that AO introduced in the early 60's. Reichert followed suit beginning in the early 70's, although the Zetopan had excellent market acceptance as a 160mm tube microscope system and they clung to that, possibly longer than they should have. Between 1961 and the early 90's both Reichert and AO marketed both short bodied infinity objectives and 45mm D.I.N. infinity corrected objectives, as achromat, planachromat, planfluorite and planapo. There were also a few semi-plan, made in the Austria factory. One of these is notable, in that it was a single example of a specific objective that due to it's existence and the lack of any other , plus a need to fill a void in various model's systems, was called on to fill a number of roles. It therefore serves as one example where a specific objective crosses over several microscope systems. It was also used in at least two 45mm systems unchanged, except for being integrated with a lengthening adapter to convert it from a 34mm objective to a D.I.N. objective and later hidden in a sleeve with an adapter to be 45mm, as an option for a U.S. based cell analysis system mfg. The original objective, in it's 34mm incarnation was an option for the AO series 100 as well as for the Reichert Diavar 2, made in Vienna. What this indicates is that the Reichert infinity system and the AO infinity system were harmonious. Using 45mm Reichert objectives on an AO infinity stand, originally designed for 34mm objectives presents little problem. The 10/20 series has a rather long dovetail guide, for the stage, so it can be dropped 11 mm easily. This might cause a small problem getting certain condensers in and out but I usually unlock the stage and slide it up a bit anyway, to avoid scraping the top lens against metal components.
Then there are the planfluorites. I have seen two of the 100X 1.30. One, made as an option for the series 400, which was a D.I.N. microscope and another in the design of the later Polyvar objectives, also D.I.N. which did not have etching; they were paint marked, look very different but internally are identical.
So, it seems that the AO infinity platform, originating in the 1960's was the central pillar upon which , AO, Reichert and early Leica infinity microscopes were based. Later in the life of the AO and Reichert instruments, whether Buffalo or Vienna made, the name on them became Leica.
Leica , just as Reichert before it and then Cambridge is a name based on a corporate decision of marketability. E. Leitz, by the time of the takeover by Wild to form Wild/Leitz had clung to 170mm as an optical tube length for decades, unwilling to recognize it's obsolescence. They eventually adopted the WIld 160mm tube system. As a union they suffered from the onslaught of the recently emerged Japanese microscope makers and were in a poor financial state. I have heard , that bankruptcy was imminent. Merging with the also financially strapped Cambridge Instruments group in the late 80's was a marriage of convenience. There was a ready made infinity corrected platform on which to build and a ready made name on which to sell; Leica Microsystems, wholly cut away from the camera mfg. . It doesn't now matter, whether Leica Microsystems is in fact owned by a venture capital company based in Washington D.C. and in terms of ownership and connection it is completely divorced from Leica camera, it is a name that sells.
There appear to be two Leica infinity systems, the HCX and the HC. In literature, Leica states that the best way to make an optical system is to effect corrections at their source. This implies that the current HC objectives yield fully corrected images. This seems to be the design ethic that they inherited. The HC objectives all have large barrels and 25mm threads, primarily I presume to assist in the ease of providing very large fields. The first Leica HCX objectives were conventional 20mm objectives, some of the earliest of which were made in Buffalo for the Leica series 400 and 2000 and were essentially the older AO objectives with the Leica name on them. A long time ago, I had a conversation with a rep from Leica and he was indicating the usefulness of what he called the Buffalo objectives as replacements for Leica microscopes. Based on this I assume that the Leica HCX optical system is little changed from the original AO platform. It would make sense. If it worked and was in the system already, why change it? I don't know about the HC system but aside from the thread size and other refinements of correction commensurate with improvements of their time, it would seem likely, based on the literature that both the HCX and HC are fully corrected at source . I would be interested in info from anyone who has managed to convert an HC objective to be used on an older 20mm stand. It is probably little done but the opposite may be more common; HCX objectives on an HC stand.
I have read numerous times that the Leica tube length is 200mm. By extension does this mean that the AO tube length is 200mm? An easy way to find out is to calculate the magnification ratio using AO objectives compared to those from another system, such as Olympus, that do have a known tube length.
I don't have any Olympus objectives. I have tried one Chinese objective , that was designed for an Olympus and it seems perfectly compatible on an AO stand. As far as your AO 20 goes Charles, have you tried any of those AO objectives on your Olympus stand or do you just have the stand alone? As far as putting D.I.N. objectives on the 20, it doesn't seem to be a problem with AO/Reichert objectives. The head in the 20 is a little restrictive, in terms of the size of the field , with 19 being about as high as you can go but all of the other AO heads have the same dovetail, so if you wanted a bigger field, you could put a Microstar IV or series 100 head on the 20.
As far as the AO phase condensers go, the series 100 and 400 had the same dovetail. I'm pretty sure the Leica 2000 did as well. The 10/20 had a similar dovetail to the 160mm series 4 and the 15/35, that preceded the infinity era. Despite that, the actual 15/35 and 4 phase carousel is different, so the series 10/20 has a pretty unique phase condenser, incorporating the older dovetail with the newer condenser design. The model 60 may use the same one too, although I haven't looked at one but it makes sense.
Annuli are pretty much the same for all of the infinity scopes and if you found a condenser, and they are missing, some of the dealers have them in stock still. I am unsure of how difficult , it would be to convert one of the later condensers to a 20. Probably, just fitting a yoke from a later series would suffice. Since you have invested in Olympus, I am almost dead certain that Olympus D.I.N. objectives would work in the 20. Perhaps an Olympus phase condenser could easily be converted too.
If you do proceed and decide to go with an AO condenser, I would recommend aiming for the D.I.N. objectives, made for the series 400. Despite the fact that they were painted and often the paint is worn off, so they look tatty, there were significant improvements in achromats in the late 80's, through the 90's, so despite the newest AO 34mm phase objectives being good, the D.I.N. objectives are better.
. I am thinking of resurrecting it and trying to get a phase contrast condenser and objectives. So additional questions... which of the objectives for the AO 20 (brightfield) were most highly regarded. (Conversely, any of them considered "duds"). Is the #1240 turret phase condenser tough to find? The phase objectives?
