Re: Query about Zeiss long working distance objectives

On Aug 22, 12:45 pm, Victor <microscope...@xxxxxxxxx> wrote:
As a practical matter, in today's microscopes, interchanging
objectives isn't necessarily a good idea, but we're not talking about
today's microscopes, we're talking about 160mm tube length microscopes
and objectives.

Unless either microscope from which the objectives come have eyepieces
that say "plan" on them, then you should feel perfectly free to
interchange objectives from one microscope to another. There is no
optical difference of any kind which would degrade the optical
performance. If they have eyepieces which say "plan" on them, then
they have additional corrections in the eyepieces. When used with
fully corrected objectives, this results in "overcorrection" and
relatively poor image quality.

If a microscope utilizes fully corrected objectives, then adding a
fully corrected objective will not cause any degradation of image
quality of any kind.

These days, it's a lot different, as there are several additional
factors which play into the formation of the image. Some
manufacturers still make fully corrected objectives (Nikon), others
make objectives which are partially corrected in the objective, and
partially corrected in the image forming "Infinity Tube Lens" (Zeiss),
and Leica makes them corrected in the objective, and the infinity tube
lens and the eyepieces. That and vastly different thread sizes and
definitions of "infinity" between manufacturers makes things far more
complex.

To answer your other question, about long working distance objectives,
generally, they work ok, and are parfocal. The reason I say
"generally" is because in many cases, LWD objectives will have a
correction collar on it, and for parfocality to be established, there
merely needs to be a focal point within the range of correction on the
correction collar.

I realize that it's tempting to make blanket statements based on a
negative experience or two, but "Because I put X objective on Y
microscope, and it wasn't optimal, All non-Y objectives will give
negative results", is simply a hasty generalization and not in line
with the more complex reality.

Victor, interesting post! I've never seen an eyepiece with "Plan" on
it. Zeiss, for instance, used to label their eyepieces as Kpl or
Cpl. Perhaps you could explain.

Thanks,

Kevin Cunningham
SMS

.

Relevant Pages

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