Re: How to measure the actual numerical aperture of a microscope objective?

Posted by lechristophe on
URL: http://confocal-microscopy-list.275.s1.nabble.com/How-to-measure-objective-transmission-curves-tp590172p590205.html

Search the CONFOCAL archive at http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal I used to just get a not-too-bad PSF and measure the angle of the light cone in XZ view, that is directly related to the NA as in this method :

http://support.svi.nl/wiki/NaNumericalApertureExperimentalPsfBlurConeImpFaq

One can have surprises in the resulting number (I got around 1.15 from a 1.40 100X objective). However, one has to try to match RI of the mounting medium. By the way, the SVI wiki has many great advices about deconvolution and microscopy.

Christophe




John Oreopoulos a écrit :

Search the CONFOCAL archive at http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal Hello all again,

In my research, I am now faced with a situation where I need to obtain an actual measurement of the numerical aperture (NA) of an Olympus oil immersion objective. Can anyone tell me or point me to a reference that explains a simple method to determine the actual NA of a microscope objective? If the measurement is difficult and not simple (ie requiring sophisticated optical instruments and opto-mechanical apparatus), can someone tell me how reliable the number written on the barrel of the objective is or what it's actual uncertainty is? 

The NA written on my objective is 1.45. How accurate is this number?

Thanks in advance for any help!

John Oreopoulos, BSc,

PhD Candidate

University of Toronto

Institute For Biomaterials and Biomedical Engineering

Centre For Studies in Molecular Imaging

Tel: W:416-946-5022