Re: Eyepiece and virtual image

Posted by Carol Heckman on
URL: http://confocal-microscopy-list.275.s1.nabble.com/PSF-with-DIC-tp3781952p3788757.html

Joachim-
According to my understanding, some oculars produce the virtual image and some do not.  If not, then you can see the image projected on a sheet of paper.
Carol
Center for Microscopy & Microanalysis
Bowling Green State University
________________________________________
From: Confocal Microscopy List [[hidden email]] On Behalf Of Joachim Hehl [[hidden email]]
Sent: Thursday, October 08, 2009 5:35 AM
To: [hidden email]
Subject: Eyepiece and virtual image

Dear all,

I have a –maybe stupid- and not confocal but “basic optic” question:

As you can read in all textbooks concerning microscopy and geometric optics the objective produces a real, inverted and magnified image since the distance from the object to the object front lens is bigger than one but less than two focal lengths of that given objective.
This intermediate image is then  magnified by the eyepiece. Since the intermediate image lies exactly in the front focal plane of the eyepiece the result is a virtual, true sided and magnified image which occur in the infinite space.  Our eye with its optical components is then producing a real image on the retina.
So far, so good.
By definition, a virtual image can not be captured on a screen. BUT: When I hold a piece of paper in front of the eyepiece in a distance bigger or smaller than the  back focal plane of the eyepiece (the distance I use when I look through it with my eyes) I am able to capture a pretty sharp image of my object on the paper. Why is this? I should not since it is a virtual image?
Thanks for your input!

Joachim


Joachim Hehl
LMC-Light Microscopy Centre, ETH Zurich Hönggerberg
Schafmattstrasse 18, HPM F16.1
CH-8093, Zurich, Switzerland

Web: www.lmc.ethz.ch
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