31 15 81 10X W.F. eyepieces

[geo_man]

Hi all, does anyone know what scope Leica 31 15 81 10X WF eyepieces are intended for? Would they work fine on a B&L SZ7 for example?

Thanks in advance!

[Scarodactyl]

They are standard bausch and lomb 10x wf stereo eyepieces, later with the Leica logo put on presumably. Good for sz7s for sure.

[geo_man]

They are standard bausch and lomb 10x wf stereo eyepieces, later with the Leica logo put on presumably. Good for sz7s for sure.

thanks Scarodactyl!

[apochronaut]

Not so fast!

Some of the eyepieces for the SZ7 have different cat. #'s than those for the SZ3,4 and 5. I am not sure exactly what the differences are but the schematics show differences, although the #31-15-71 10X W.F. seems to be common with the 15X W.F. being different.
Things got a little jumbled at AO and B&L in the later years too. They both came under the same corporate ownership and I'm pretty sure that duplication was considered to be the devil.They committed each factory to produce that which was selling the best. They continued with the Stereozooms and cancelled the Stereostars, cancelled the Balplan and continued the series 400/420. They started branding Reichert stuff as B & L and B & L stuff as Reichert. When the entire conglomerate got rebranded Leica, both AO stuff and B & L stuff became Leica.

You have put the # in a format reminiscent of the B & L pattern with the 3 sets of paired numbers separate. At B & L these would have been separated by a hyphen. However, I see Leica 311581 eyepieces around which very much appear to be from the AO factory. I would be suspicious that they are not just the former AO/Reichert 181 eyepieces, remarked with a Leica code. They sure look like it and I would want to try them out before committing to them.

I may have at least one of those around. I can try it out in an SZ 7 and report back. One of the things that can happen with stereo microscope eyepieces though, is that their focal point can induce small collimation problems and in addition their field flattening characteristics can mismatch the objective's requirements. Two cases in point can be found, one each with both AO and B & L. With AO, the Stereostar series uses two different 10X W.F. eyepiece designs throughout the range. When I use the cat.# 145 eyepieces in a 569 microscope, they induce a slight out of collimation sense, that catalogued # 134 eyepieces don't. Clearly , the optics of the # 569 microscope need a slightly different eyepiece than those of the 570 and 580.

With the B & L stereozooms, the catalogue again lists two different eyepieces , this time W.F. 15X, throughout the range. The 31-05-62 for the SZ1,2,3,4 and 5 and the 31-05-68 for the SZ7. It lists 31-15-71 as the 10X W.F. eyepiece for the SZ7 as well as all the others.

[geo_man]

Thanks Phil, I i see these for sale and commonly they are less expensive than B&Ls. I was wondering what scope(s) they are intended for.

[apochronaut]

I cannot find the Leica eyepiece that I mentioned but on reflection, I think it might have had an 80 at the end of a 6 digit #. I might have paired it with a 180. It is possibly in a microscope at the farm.
However, I did trial a set of AO/Reichert 181 eyepieces in a couple of stereozooms. These look physically identical to the 311581 eyepieces with Leica branding. Although 181s produce a nice flat and well corrected field , the field stop isn't coherent with the diameter of the optical pathway. The optical pathway produces an out of focus inside border, thus vignetting the image, kind of like the moon 2 days before full. 181 eyepieces are original equipment in series 400(410/420) transmitted illumination microscopes.
Asssymetrical vignetting is a problem with many eyepieces in stereos used in non-original applications and another reason to search out the original eyepieces.
I did come across a set of 310564 15X W.F. eyepieces with Leica branding. These are clearly a B&L eyepiece with a B&L cat.# converted to a Leica cat.#. I think they did the same with the AO stuff and I am pretty sure the 311581 are 181 eyepieces wearing a new coat.

[Scarodactyl]

Thanks apo, you are totally right. I was looking at a pair on my desk but they are 31 15 71s, not 81s.
Just from googlin' around I see them on Leica SZ6s and GZ4s, so I'd guess they were meant for that line. The SZ6 and SZ7 that Leica made appear to be pretty much identical to the Bausch and Lomb/Cambridge branded ones, and the GZ7 externally looks not much changed from the SZ7. The GZ4/GZ6 however are some sort of weird mutants, and it's unclear how much of it is B&L stereozoom heritage and how much is AO stereo star heritage. I'm not sure how you could even tell, since opening up a stereo star and a stereozoom the insides look pretty darned similar already.
I suspect it would not be a particularly problematic pairing, but it really wouldn't be that significant a savings either.

[geo_man]

Thanks a lot guys, great info!

[PeteM]

Phil, Would you happen to know what differences if any are between the AO/Reichert/Leica 176, 180, 181, 191 eyepieces spec'd for various compound microscopes?

[apochronaut]

They all look so similar, don't they. It's easy to assume one is as good as another, since they are all marked 10X W.F. You can add to the mix the 176A, which look so much like the 180 that superficially they seem like they are an older version. Close but not quite.

If you go back to the mid-60's, plan objectives were only available at the very top end of any microscope company's product line. Most average scopes still used a huygens eyepiece, which offered their well known but limited corrective capacity, coupled to standard achromats and only when you started forking out the cash, could you conceivably get a flat field, a wide field and excellent corrections at more than a 12-13mm f.o.v. To get plan performance everybody used the concept of plan compensation. While possible, it was very expensive to make an objective that offered complete plan performance, and even more difficult to get all the objectives in a series to agree with one another. By bringing the objectives as far as they could without breaking the bank, a microscope manufacturer could then use a common corrective eyepiece in order to complete the job. Ideally, each objective would have benefitted from it's own paired eyepiece but for practical purposes, microscope systems generally averaged the performance of the eyepiece with the objective series but had to up the anti when it came to offering plan optics.

Plan is a variable concept, and could have any field width associated with it, limited by the objective design, eyepiece design and also the choice of eyepiece tube diameter. Most companies, within the confines of their 23.2mm eyepiece tube models, took the idea no further than 17-18mm, even until the 90's in some cases. To take it further required a radical re-thinking of their systems, something that eventually occurred at all of the major companies by the early 90's, when the wholesale shift to infinity correction and wider and longer objectives took place.

AO ( and B & L too) started their radical rethinking of field width and planarity within the framework of a standard microscope, a lot farther back. In the 1950's in fact. By the late 50's AO already had a 20mm f.o.v. using a 23.2mm tube on a standard scope and by 1967, they evolved an economical series of plan objectives, with W.F. However, most of the technology, theory and testing practices of the time were not a lot different from the 19th century, so over time the plan objective line improved and so too were the eyepieces corrected appropriately in order to match the increased perfection of the objectives. Thus, the 176,176A,180,181 and 191 all designed to do pretty much the same thing but in different ways, are with few exceptions, not cross compatible.

Although the 50's era cat.# 146 10X W.F. 20mm f.o.v. eyepiece does compensate a fair amount for off axis aberrations with the last generation of AO 160mm tube objectives, there is no claim of the system being plan.

The first commercially offered version of planachros from AO was around 1966. The cat.# 176 10X W.F. 19mm f.o.v. eyepiece was the first of the their eyepieces specifically tuned to compensate for plan performance and it applies curvature of field and off axis colour correction as an assistance to the fledgling plan objectives of the day. Somewhat later AO added the 176A eyepiece, which is catalogued as a 10X W.F. eyepiece for use with the non-plan achromats. When the early series 10 plan system came out, it seems that 19mm was the cutoff point at which they felt they had done their job. The optical tube allows only for a 19mm f.o.v. with the compensating # 176 eyepiece. If you put the #180 20mm eyepieces in, you will get vignetting. The 176A on the other hand, seems to pick the image up in a different location in the pathway, allowing for 20mm to be realized. Why that eyepiece was targeted at the achromats only, I don't know because I use them routinely in the 10/20 series with both planachros and planapos and I find them superior to the 176, mainly due to a slightly wider field but also due to slightly easier optical centering.

Cat. # 180 came along with the 20mm optical path of the series 100/120. The improved objectives, cat.#'s 1021,1029,1309,1311, 1128, 1129 had anywhere from slightly better edge colour correction and curvature of field, to a lot better, so the colour correcting and field flattening characteristics needed to be less with the 180, than either the 176 or 176A, and as well it offers a 20mm field. By 1984, the cat.# 1309 and 1311 advanced planachros couple with the 180 eyepieces offered colour correction previously only capable with fluorites and with perfectly flat 20mm fields.

Both the series 10/20 and 100/120 relied on a compensating telan lens to do some of the correcting in the system in addition to the eyepieces. By the time the series 400 D.I.N. objectives came out around 1985, the job of the telan lens became less correcting and mostly converging. The increased objective barrel capacity gave room for more complete corrections in the objective so the image leaving the objective is as perfect as it can be for it's class. The eyepiece to complement that system needed to have significantly less curvature correction and much less off axis colour correction. Their role is as more of a magnifier. Using the incorrect eyepiece, the 180 for instance, destroys the coherence of the system. They also don't fit.

The 181 eyepieces are noticeably slightly smaller by 2 thou. than the 180 eyepieces. Years ago I noticed this and very briefly thought it was a case of Q.C. on that instrument, which was my first encounter with one; but no, the difference is deliberate. My best guess is that since W.F. 10X eyepieces were so common , were increasingly similar in appearance and especially the cat.#180 & 181 look identical unless you read the #, and their system in order to perform to it's peak needs optimal eyepieces; AO decided to close off the possibility of anyone interchanging eyepieces, the single most common problem affecting used microscope performance outside of outright dirt and damage.
I wonder how many microscope technicians have been asked to fix a dramatic loss in quality of an instrument, only to find out some duh in the lab or at school had swapped in the wrong eyepieces.

The 191 are basically the same corrections as the 180 but since they were made for the ATC 2000, they may be a little more corrected to the standard achromats in the 45mm parfocal barrels that were the basic objectives for that instrument. The ATC 2000 was pitched at the small lab and scholastic market and also had facility for locked in eyepieces, so there is a set screw groove in the 191 that doesn't exist in the 180 and they have the 2 thou narrower barrel. Since the ATC 2000 also could use planachros, it may be that the 191 with the locking ring were used for the achromats and if the planachros were installed, 181s without the locking ring were used. I haven't spent a lot of time comparing them to the 180s, or 181s, with a full range of AO/Reichert objectives. They pick the image up a little farther up the tube, than the 181s but seem identical to the 180s, when used one each in a binocular. All of the above eyepieces when compared side by side in the same instrument, will show varied focal points and some difference in relative magnification. The 10X on the barrel is 10X, only when used in the correct application, another distortion potentially caused by swapping eyepieces or in fact objectives of any kind from optical system, to optical system.

[PeteM]

Thanks, Phil. Very informative.

[wabutter]

I know this discussion goes back a bit, but I recently joined the group so I didn't way in. I wanted to take a moment to clarify a few points in the long explaination from Apochronaut.

The AO and B&L eyepieces retained there original design even after the Cambridge Instruments acquired B&L. Later versions of the Stereozoom were re-branded as Cambridge Instruments GZ series. AS was mentioned, B&L had a larger market share than AO in the Stereo line so the StereoStar was phased out. The Microstar dominated the market for the hospital laboratory segment over the Balplan, so the Balplan was phased out. The production moved to Buffalo NY from Rochester as did the tooling. A 311581 was the same eyepiece as the 31-15-81. The implementation of the Reichert-Jung name was generally applied to former AO products as the AO brand was not purchased by Cambridge.
When AO introduced the Series 10/20 product as the first infinity corrected laboratory microscope in biology, in the 60's it changed the way the way eyepieces were designed. The 176 and subsequent eyepieces for the compound microscope were not compensating eyepieces. The primary compensation was handled in the Tele-lens. Later iteration of microscopes addressed changes in field size relative to the flatness of field for the objectives. Early AO Plans supported an 18mm FOV like the 176 offered. As the 110/120 were introduces the FOV moved up to 20mm. and so on. The Tele-lens still did the compensation work though. By the time the 410/420 was introduced in the late 1980's the DIN standard barrel length was employed and even higher amounts of correction were handled in the objective. The 180 and 181 eyepieces assured that the right flatness of field could be achieved with the newest iteration. Keep in mind that even an achromat objective can be made into a flat field of view if the eyepiece FOV is reduced enough.

Keep in mind, one of the big marketing push that Nikon used in after moving to an infinity platform was the Chrome Free optics. Essentially, uncompensated eyepieces that were used with the infinity objective program they introduced. Eventually moving to a new 60mm barrel length with the Eclipse product line that offered more correction in the objective.

After the CI/Leitz merger, Leica moved to a two stereo product line program. CMO from Heerbrugg and the Greenough design from Buffalo, eventually moving that to a Singapore production base.

Apochronauts comments are spot on though. It is generally best to use optical components that were and are designed for the platform they originated from. This will ensure the highest compatibility, optical performance and correct compensations.

Regards,
Wayne

[Scarodactyl]

I am pretty sure the GZ line was phased in after the Leica merger, not under Cambridge. I have only seen normal stereozooms with the Cambridge branding, and you see normal stereozooms branded Leica as well, with the later mutants (GZ series, etc) only occurring under the Leica name. [Though to be fair I think b&l had already set themselves on that trajectory with the Stereozoom 6 before anyone bought them out.]

[wabutter]

You are probably right. I lose track of time and in the 1980's it was rapid fire M&A with Cambridge. From the AO/Cambridge to the Cambridge/Leitz move only covered three years. Also LKB and a few others were added to the mix on the specimen prep side of the business. In any case the GZ line was an extension of the StereoZoom line and the tooling moved to Buffalo during the Cambridge era.
Wayne