Understanding an Olympus u-cpa bertrand lens

[microb]

Since U_CPA's as linked below are rather hard to find or very expensive, I'd like to set up a test optics path to build my own. Supposedly it's just a convergence lens, but in Leica there are two lenses with one fixed on top and the bottom adjustable in a 1cm range.

Is it correct to say that the Bertrand lens is focusing at around ~5mm above the top of the objective and then creating parallel rays up to the tube lens? If a company like Leica does two lenses in an infinity set-up, it seems that the fixed one on top closer to the tube lens is just a magnifier but the rays heading up to the tube lens would be parallel.

So to test, could an extra Olympus tube lens be inserted up-side-down into the light path below the microscope's real tube lens, positioned 180mm away from the top of the objective, and have a valid Bertrand lens set up shooting an image up to the tube lens?

https://microscopecentral.com/products/ ... trand-lens

[MichaelG.]

I think my problem would be understanding why Leica uses two lenses.

Here is Hallimond's patent of 1947
https://worldwide.espacenet.com/publica ... cale=en_EP

The Olympus configuration differs mechanically, but appears optically similar.

MichaelG.

[microb]

The Leica set up is probably a distraction from the main question. The U-CPA has a mirrored path to put a long travel path on the Bertrand lens. Not having seen the insides of a U-CPA, what kind of lens is best? And to test, could one use any converging lens on an infinity microscope where the Bertrand lens has a position equal to its focal length from the objective's top. The rays then become culminated as they go up into the tube lens. So could a U-TLU be turned 180 to become a Bertrand lens 180mm from the objective?

Attached is an image of what looks like a patent for a U-CPA like design.

As a side note, below is a description of a two lens Bertrand set up. But it doesn't seem to match the Leica DMR Bertrand lens setup.

(https://patents.google.com/patent/US3572885A/en?)
FIG.4, however, shows a device according to our invention which uses the structure and functions of the elements shown in FIG. 3. in FIG. 4, an image of the object 1 is produced by means of the objective 2 and the additional lens 9 in the plane of the diaphragm 6a which is again located immediately adjacent the Bertrand lens 5. It should particularly be noted that the insertion of the additional lens 9 according to our invention eliminates any necessity of vertically displacing the object (refocusing), since the focal length of lens 9 is calculated-i- into account the focal length of the objective-as to always produce the object image in the plane of said diaphragm 6a. The (conoscopic) image of the exit pupil 7 is, as before, produced in the intermediate-image plane 3 and may be ob served through the ocular 4. The formation of the image of the exit pupil 7 is practically not influenced by the additional lens 9. Of course, as in the prior art, the Bertrand lens and diaphragm are removed during orthoscopic viewing. How ever, with the present invention, the additional lens 9 is also removed during orthoscopic viewing. These three elements are all inserted during conoscopic viewing.

[MichaelG.]

Thanks for that 'microb'

... I still can't help, but at least I'm better informed than I was.

MichaelG.

[microb]

This paper gives descriptions and references to tube lens design and also the Thorlabs parts they used to make Bertrand lenses.

http://www.zia-lab.com/sites/default/fi ... A_2015.pdf

[MichaelG.]

Wow! ... Thanks for sharing that.

Will have to read it tomorrow though

[long day today, drove to Anglesey to visit 'South Stack Cliffs' etc. 300 mile round trip]

MichaelG.