Re: How to distinguish 160 vs 170 mm eypieces?

On Jan 21, 2:38 am, da...@xxxxxxxxx (Dave Martindale) wrote:
shiraz14 <shira...@xxxxxxxxxxxxxx> writes:
Yes, the Pol scopes (& parts for Pol scopes) generally have a wide
number of slots (for insertion of analyzers, compensators, etc) but
these are common slots and do not suit my purpose. I need this slot to
be integrated into the trinoc head (just below the sliding prism
assembly and where the light rays converge, at the point of exit from
the infinity system), so that the slider inserted sits exactly in the
rear focal plane of the image formed by the specimen.

I'm not sure what you mean by "the real focal plane of the image formed
by the specimen".  Do you mean the real image of the specimen that is
formed by the objective?  That is found inside the eyepiece barrel, at
about the same location as the eyepiece field stop.  That's true for
both infinity and finite-tube-length scopes.

On an infinity system, the light rays from one point on the specimen are
parallel in the scope body tube.  The tube lens starts these rays
converging, but the plane of convergence is inside the eyepiece.  There
is no place inside the trinocular head where you can place a reticle or
an edge and have it be in focus at the same time as the specimen.

What are you trying to do?

        Dave

Hi Dave,

Firstly, thank you for your valuable input. Also, as a correction to
any possible misconceptions to my last post, NA was stated to be a
dimensionless constant as it was interpreted in the context of a
particular lens used to image a specific specimen under a stated
tecnique. Note however that NA is actually a variable (think those of
us who are relatively familiar in microscopy would know this ... this
is just for the clarification of any potential misinterpretation of
the information presented in the last post) ... factors influencing NA
include the optical technique used, mountant applied, objective,
condenser & eyepiece iris diaphragms (if any), etc.

As for the clarifications, here they go:

"rear focal plane" (not "real focal plane") = conjugate image plane as
observed by the viewer during simple conoscopy.

I presume you obtained the information for the image plane being in
the eyepiece barrel from the Molecular Expressions website - although
Molecular Expressions serves as a useful resource for microscopy, the
information provided there serves only as a preliminary guide to
microscopy fundamentals ... in reality, an infinite number of image &
focal planes exist (which may be sited at any point along the optic
train) - raising and lowering (including synthesis and elimination) of
focal (& image) planes may be achieved through the insertion of
apochromatic auxiliary lenses, etc, and any potential gain/loss in
magnification be compensated through the coupled use of a
corresponding reducing lens-pair system. For my purpose, I'd need to
have the rear focal plane lying directly below the prism assembly but
within the trinocular head, if this is not possible (due to space
constraints), then at least within an intermediate module sited
between the head and the IL axis.

Thank you and wishing you All the Best,
Shiraz
.

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