Re: How to measure objective transmission curves?

Posted by Mark Cannell on
URL: http://confocal-microscopy-list.275.s1.nabble.com/How-to-measure-objective-transmission-curves-tp590172p590218.html

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Yes Jim!

That's a good method and if the hemispherical lens is well AR coated
then it should let the light out accurately. We used a drop of water on
top of a water lens a while back but that won't work for a horizontal
measuring system. Not sure about the detector angular dependence tho'.
It might be interesting  to compare the 'two lens method'  I suggested
(which will have no detector problems) with your integrating sphere
method...

Anyone here fancy getting a paper in microsc. techniques or optics letters?

Cheers Mark

though. the James Pawley wrote:

> Search the CONFOCAL archive at
> http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>
> Hi all,
>
> If it doesn't sound too commercial, I would like to note that a lot of
> objective transmission curves are published in the 3rd Edition. In
> fact I take some pride in the fact that the earlier editions of the
> Handbook contain some of the first published transmission data on
> commercial objectives.
>
> One trick to get "all the light" out of an high NA is to oil-couple it
> to the flat side of a very small hemispherical lens. Even a small
> glass bead, with half of its thickness sticking out of the oil will do.
>
> But you have to hold your light sensor really close to it, and if you
> aren't careful, because the light diverging from the focus in the bead
> will leave it at such a large angle to the horizontal that a lot of it
> may be reflected from the glass covering your sensor (or miss it all
> together). An optometrical integrating sphere is better.
>
> I just measure transmission of the system (mostly losses in the fiber
> and filters) with the 10x lens and hope that the immersion lenses "are
> what they are".  However, this won't show up a smear on the tube lens
> that only obscures high-NA rays. I use the focusing ability of the
> Bertrand lens (phase lens) to look for this by focusing up and down
> through the optical column.  Amazing how much dust etc. you can see
> this way!!.
>
>