Re: Eyepiece and virtual image

Posted by Joachim Hehl on
URL: http://confocal-microscopy-list.275.s1.nabble.com/PSF-with-DIC-tp3781952p3787176.html

I would say it is in focus. But yes it gets a bit sharper when adjusting the focus. And the wider I go back with the paper the bigger the image is, like a projector.  Maybe you try it out with one of your scopes?

Joachim

On [DATE], "Guy Cox" <[ADDRESS]> wrote:

But is this image truly in focus?  If you adjust the microscope focus, does it get sharper?

                                                              Guy

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From: Confocal Microscopy List [[hidden email]] On Behalf Of Joachim Hehl
Sent: Thursday, 8 October 2009 8:03 PM
To: CONFOCALMICROSCOPY@...
Subject: Re: Eyepiece and virtual image

Dear Guy,
The point is that I neither adjust the focus nor lift the eyepiece. I look through the eyepiece (without my glasses, I am short-sighted), focusing and then I only hold a piece of paper in front of the eyepiece and can see the picture on it. And this also  happens  to my normal-sighted colleagues.
Joachim

On [DATE], "Guy Cox" <[ADDRESS]> wrote:

You can always get a real image from an eyepiece by refocussing so  that the first image is in front of the focal plane of the eyepiece - either  adjust the microscope focus a little or lift the eyepiece slightly in its  tube.  If you see a sharp image without refocussing from your normal  viewing position, it probably means that you - like me - are  long-sighted!

                                                                  Guy



Optical Imaging  Techniques in Cell Biology
by Guy Cox    CRC Press / Taylor  & Francis
    http://www.guycox.com/optical.htm
______________________________________________
Associate  Professor Guy Cox, MA, DPhil(Oxon)
Electron Microscope Unit, Madsen  Building F09,
University of Sydney, NSW  2006
______________________________________________
Phone [phone]     Fax [phone]
Mobile [phone]
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     http://www.guycox.net <http://www.guycox.net/>   

 

 

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From: Confocal  Microscopy List [[hidden email]]  On Behalf Of Joachim Hehl
Sent: Thursday, 8 October 2009 7:36  PM
To: CONFOCALMICROSCOPY@...
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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