planicity Leitz vs Olympus

[Rene]

Hi guys, for some years I have an Olympus BHC microscope with super widefield tube with SWK 10x/26.5 eyepieces. This enormous FOV really suck you in the slide, which for pondlife is absolutely great!
I found however my Leitz 170mm objectives performing a lot better on this scope than the original short barrel Olympus lenses, even in DIC. Unfortunately, planicity wasn't that great, especially notable with these super widefield eyepieces. So I took the plunge towards the corresponding Leitz eyepieces Periplan GW10x/26 from the Aristoplan 160mm era (the Oly BH also is 160mm TL). With better results than expected! Example images attached with Leitz 170mm PlFl 4x/0.14, Oly BHC, intermediate tube 1.25. Handheld shooting through the eyepieces with an iphone (just for demonstration purposes). Eyepieces: Olympus SWK 10x/26.5 vs Leitz Periplan GW 10x/26.

Best wishes, René

[JB]

Hi Rene,

Thanks for showing this! That's quite a difference, even though the field isn't that large with a 1.25x intermediate tube.

The effect you see is probably due to the way field flatness is corrected in Leitz optics. For Leitz plano objectives, Periplan eyepieces do part of the astigmatism correction that results in a flat field: http://www.science-info.net/docs/leitz/memos/Astigmatism-Curvature-Field-memo-6-1-62.pdf

Best wishes,

Jon

[mlippert]

Leitz - and also old Zeiss - field flatness is actually a total mystery to me. I've seen dozens of objectives and eye piece combinations that gave flat and non flat fields. I have a periplan that gives a nice flat field with the famous Zeiss 63x APO and NPL Fluotars but I've seen other periplan eye pieces give a completely warped field with the same objectives. On our 'new' Laborlux S, the periplans give not too great field flatness with the same objectives and it starts to get weird as soon as i change the IPD.
Is there anywhere a source that explains what was done when?
If the 170's give a nice field it might be because of exactly the extra light path in binocular tubes.

[JB]

Hi,

Which Periplans were they, exactly? The most likely problems are wrong tube length (10 mm vs. 18 mm parfocal Periplans) or defects (like a missing field lens at the base of the Periplan).

There is no one source to get a quick overview but you can read through some of the old broschures and get a pretty good idea: http://www.science-info.net/docs/leitz/

[Rene]

Thanks for the link Jon.
Remark (6) mentions total correction of astigmatism and field curvature within  plan-objectives, which means that the eyepiece has to be neutral in those aspects. So I suppose remark (4) about the correction of curvature is about the field curvature of the  eyepiece itself. However, the remark about overcorrection of astigmatismus within the eyepiece would mean that the image of the objective needs to be undercorrected, akin to the correction of chromatic abberation. Questions, questions...

Mysteries indeed Michael. What do you mean by changing IPD? Changing tubelength? Never realised it could be related to field curvature.
In any case, there is no extra light path needed for 170mm Leitz objectives, as that is an issue to do with the microscope stand versus the eyepieces (see Jon's reply). I'm using a 160mm (Oly) stand with corresponding Periplan 160mm eyepieces, and not the old 170 mm Periplan eyepieces of yesteryear. Also, the objectives on my system are parfocal, so I suppose the setup is pretty much in optimal conditon.

Thanks for the input, regards,

René


(apologies for my use of English in this forum. For me reading in Deutsch is fine, but thinking and writing in Deutsch is a different matter. Replies in Deutsch are however greatly appreciated!)

[Rene]

Oh and it cannot be only difference of field curvature between Oly and Leitz eyepieces. When refocussing at objects at the extreme edge of field, the Oly eyepieces  still give a fuzzy image. As correction of chomatic abberation between Leitz and Olympus is about the same, it must be something different. It might indeed have something to do with correction of astigmatismus.

Tricky business. I'm happy my gamble paid off (those GW Periplans were expensive eyepieces!)

Best wishes,
René

[Rene]

Thanks for showing this! That's quite a difference, even though the field isn't that large with a 1.25x intermediate tube.

That's right Jon, so I couldn't help myself and tried it just now without the DIC intermediate tube. Tried it at 1.0x with several Pl lenses also with a NPl 6.3/0.2, and the image is flat as a pancake. Diatoms become slightly oval at the edge though, and these periplans also show a slight overcompensation of chromatic abberation (fringing). But sharp nonetheless.

Best wishes,
René