Interesting objective lens, 250x

[wporter]

Someone is selling this 250x objective, looks like the same class as used (in lower magnifications) by the Reichert Polyvars, for epi/DIC examination of ICs fabrication. From my own resources, I don't think it was something that was ever offered for the Univar.

https://www.ebay.com/itm/Reichert-Mikro ... 1438.l2649

As a 10x eyepiece would yield 2500x, a bit past the usually accepted maximum usable magnification (!), I wonder if it was for use with a 5x WPK eyepiece, one of which I own. This eyepiece is unusable on the Univar, as it is too long and runs into the prisms in the head before seating. I don't know if it would fit the Polyvar or Polylite or any of the subsequent Reichert/Leica microscopes.

[apochronaut]

I've seen these before. There is no doubt that these must have been made for a specific application where a particularly wide field was not necessary, so 5x oculars were used with this.. I haven't worked it out yet but it seems that there might be some merit , in gaining the maximum primary magnification through the objective.

[wporter]

A little research turned up the use of this objective on the Leica INM200 & INM400 chip analysis microscopes, circa 1996-7. Perhaps it would also fit the Polylite & others, as mentioned by the seller.

The 5x WPK ocular is indeed narrow-field. My visual estimate gives an apparent field about 1/2 of that given by the 10x WPK (field number 24). Like looking into a tunnel!

Good question, Apo, about why the mag increase is done in the objective. Perhaps it is just because the amount of glass to be shaped was smaller than shaping the big chunks of glass in the eyepiece. Makes me think of some of the highly corrected and wide-field oculars in the amateur telescope market a few years ago; seemed like there was a race to produce the biggest & heaviest oculars imaginable, all very expensive.

[apochronaut]

Those would likely be later upgrades of the Polylite or Polyvar made by Reichert but branded Leica.

It's possible the objective is marked according to the old but maybe still current A.S.T.M. standards, that sometimes regulated the markings on Metallograph optics . The direct ancestor of those large thread Reichert objectives for vertical illumination, are the objectives made for the AO model 2400 A and P metallographs. These were of a large thread design( I don't know the parfocality), infinity corrected, flat field achromats. They existed at least as far back as 1951 because I have a 1951 catalogue for the instruments. Those Metallographic optics , were marked with the total magnification of the system 50x, 75x, 100x,200x,500x 1000x and 1500x. The 1500x was a high N.A. oil immersion objective , likely of an actual magnification of 150X with an N.A. of 1.4 of higher, working with a 10x eyepiece.. Even the eyepieces were marked similarly, with the total magnification..

Looking at the 250X objective, the physical aperture of the objective seems quite large for an objective of such a high magnification. It should be about 1/2 the diameter of a 100x objective. If it was in fact a 40x .95 planapo, the magnification when coupled with a 6.3x eyepiece would be 252x. In order for it to be an actual 250X objective , the eyepiece would have to be a 4X in order for the combined system to not stray too far into empty magnification.

[wporter]

At first I was sure that you had it right, about the 250x being the ASTM entire magnification, rather than the objective by itself, but now I'm not so sure:

a) the Leica catalog says the INM400 has "Possible objective magnifications from 1.6x to 250x"

b) my own Reichert 150x plan apo objective has a pointy-end-glass that is wider than the 100x plan fluor objective's (both are 0.95 N.A.). (Looking thru the back end of the objective at a light source, though, the light spot thru the 150x is noticeably smaller than that of the 100x)

If the 250x is actually the objective mag, then maybe they just added another lens to the 150x plan apo to increase the mag, thus getting rid of the complex magnification changer that they had on the Univar, Polyvar, etc. that were typically 1x, 1.6x, 2.5x. (Since they were all infinity systems, could you just take the apo 1.6x mag changer lens and add it to the rear end of the 150x plan apo, thus getting a 240x objective?)

Can't find a Leica INM 400 manual on line, unfortunately.

[apochronaut]

I haven't used a magnification changer on any of the Reichert big microscopes but I used on an Axiomat. While the results were impressive by the sheer size of some items that I was not used to seeing so big, there was in fact a degradation in image quality so bad that the changer was pretty much an irrelevant trinket for the high magnification objectives. It had it's uses for the objectives that had N.A.'s relatively high for their magnification, though.

I would assume that the case is the same on the Reichert instruments. It would seem really odd that they would add the mag. changer factor to an objective.

[MichaelG.]

A little research turned up the use of this objective on the Leica INM200 & INM400 chip analysis microscopes, circa 1996-7.

It doesn't get us much further, but this advert confirms that Leica INM200 is way out of my league.
https://www.fabsurplus.com/sdi_catalog/ ... o?id=86232

MichaelG.
.
Edit: see also p50 of this catalogue
http://промкаталог.рф/PublicDocuments/02-0333-00.pdf
.
Edit: a little more detail here
http://www.promicron.de/media/docs/broc ... uv_eng.pdf
... including this tantalising statement:
"Secondary magnification
Combining the Leica INM 200 with the ergonomic tube FSA-VV allows the use of a secondary magnification system with increments of 1x, 1.6x and 2.5x, resulting in total magnifications of 16x to 6,250x. In connection with the CONFOCAL MODULE, which has an additional magnification factor of 2.25x, total magnifications of > 10,000x are obtainable."

[apochronaut]

O.K... that explains it. it is a confocal and uv objective, where the diffraction limitations of visible light are reduced dramatically.

I further came across two incarnations of the instrument, as the IN200 and the INM200. The IN200 has many aspects that link it to Reichert, even down to the objectives being very Reichertish. Later the objectives adopted a decided Leitz look to them. Badges on an IN200 says made in Germany, while a later badge says Made in Germany as well. The INM200 seems to be the designation for the uv version.

Information gleaned from one University in Italy, covering their equipment complement mentions that the objectives on the microscope are 2.5X to 100X and then mentions that a further feature is UV imaging with a 150X objective.

Leica is an interesting company at this point in time because they still had the factories of 6 companies in production and the machinations and contortions the company went through to organize their holdings and keep research going strong are Herculean. They did get to cherry pick the best concepts from the various branches of the company , though , and bring all that forward. Interesting how much the vertical illuminator light box on that microscope resembles the one on the AO/Reichert Diastar.