Re: Here is why; and confusing conclusions about tubelength

On Feb 9, 2:50 pm, "Theo Griep" <gr...@xxxxxxxxx> wrote:
Thanks HJ and Kevin,

The reason why I'm trying to use 160mm objectives on a 170mm microscope is
that I have a set of 160mm DIC objectives that I want to use on a Orthoplan.
They can be used on a Orthoplan 'as is' but I was wondering if it would be
better to use them with tubelength 160mm.

Some information about tubelengths (from a Leitz memo) that I found very
useful:
The 170 mm tubelength of a Orthoplan is made up of:
- 152 mm distance between shoulder of objective and its intermediary image
- 18 mm distance between the intermediary image and the upper edge of the
tube; Orthoplan eyepieces are made for this distance of 18mm i.e. they
expect the intermediary image to be at 18mm below the upper border of the
tube

The 160mm of a Dialux 20 is made up of:
- 150 mm distance between shoulder of objective and its intermediary image
- 10 mm distance between the intermediary image and the upper edge of the
tube; Dialux 20 eyepieces are made for this distance of 10mm i.e. they
expect the intermediary image to be at 10mm below the upper border of the
tube

So, using a 160mm instead of a 170mm on an Orthoplan gives an error of
152-150=2 mm just what Kevin wrote. According to Leitz this is acceptable
for all objectives from 16x and up.

According to the above it is easy to see that eyepieces from a Orthoplan can
be used on a Dialux 20 if you 'lift them op' for 18-10=8mm.
And: you cannot use Dialux 20 eyepieces on a Orthoplan (unless you press
them as a whole into the tube for 18-10=8mm).

AND THIS LEADS TO SOME CONFUSING CONCLUSIONS:
- the 160 and 170 on an objective are big nonsense and don't say a thing
about the objective! What should have been inscripted is the distance of the
intermediary image.
- on eyepieces the distance between (the upper border of the tube) and (the
expected intermediary image) should be written; for Orthoplan that would be
"18mm" and for Dialux 20 it should be "10mm".  But you won't find these on
an eyepiece...

So, both objectives and eyepieces are missing the essential data about the
intermediary image distance. Instead, objectives have a nonsense tubelength
value on them.
Ofcourse with infinity corrected systems this problem has been solved.

Last one: so you can use 160mm Zeiss objectives on a Dialux 20? No, not
always, because (as Leitz stated in their document) the older Zeiss
objectives have an intermediary image distance of 147mm. Together with the
old Zeiss eyepieces they made a tubelength of 147+13=160mm but that isn't
the 160mm of the Dialux 20 (150+10=160)......

The tube length for a 170 Leitz was 162mm actually, not that big a
difference.

The real reason you shouldn't use Zeiss objectives with an E. Leitz is
that when a microscope is designed there are about 12 things you have
to correct for. Some makers correct them in the objective, some in
both the objective and the eyepiece and they aren't the same for any
two makers. A Nikon objective looks great on a Nikon microscope, it
looks OK, at best, on an Olympus.

Thanks,

Kevin Cunningham
SMS
.

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