Re: Eye-Piece vs Projection Lens

A normal eyepiece projects the image in infinity ('virtual image'), a
projection eyepiece at a discrete distance on the film/ccd plane ('real
image'). Any deviation from the distance for which it is designed to
project the image, whether objective, tubelens or eyepiece, will
introduce spherical abberation. This can be corrected for by
lengthening the tubelength, in the order of a couple of cm, depending
on the eyepiece magnification. From my experience however, this
spherical abberation is neglectable, generally slide preparation has a
far greater influence on spherical abberation.
I suspect high dry objectives (like a 40/0.95) are the most susceptible
objecives to show this effect, oil immersions less so.

HTH, Rene.

NoSpam wrote:
Dear Group,

For some time I have been wondering how an eye-piece used as a projection
lenses for photomicrography differs from the use of lenses called projection
lenses for the same purpose.

One can for example use a 5x eye-piece in the trinocular tube of a
microscope
to project the image directly into the film plane of an attached dark box.
One
can also purchase a projection lens, usually at a high price, to do the job
of
relaying the image to the film.

The eye-piece, if it is made to match the microscope objective should give a
good picture on the film, should it not?

On the other hand, relay lenses sold by various outlets may not match the
ob-
jective and are frequently very expensive.

It would be therefore be of interest to understand the advantages and
drawbacks
of the use of eye-pieces as relay lenses for photomicrography.

May be somebody can give us an exposition on that subject.

G.R.

.

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