>The formula for resolution in bright field is not exact. The problem 
>was solved by Hopkins and Barham, Proc Phys Soc B, 63, 737-744, 
>1950. The effect of condenser on resolution is also shown on the 
>Olympus site, 
>http://www.olympusfluoview.com/java/resolution3d/index.html
>
>Mike


Hi all,

So I went to the Olympus site and found the very nice JAVA (FLASH?) 
interactive resolution demo.

Beautiful!!!

But then I looked a little closer and I am not sure that it is right. 
As I remember, Rayleigh criteria is reached when the peak of the Airy 
disk of one point overlays the first dark ring of the other AIry 
pattern (OK, both peaks overlay the first dark ring of the other 
pattern). At his point one sees about 25% contrast (or a dip in the 
intensity to about 75% of the peak values on the "Airy Function 3D 
Plot").

Now, when you set things on the demo for NA 1.4 and a wavelength of 
450 nm, you get what looks like about 25% contrast on the "Airy 
Function" at a spacing of 0.2 micrometres which seems about right 
although the contrast noted under the Intensity Plot is 31%, not 25%. 
Although it is a bit hard to see, I could convince myself that the 
peak of one Airy figure seemed to lie over the first dark ring of the 
other.

But when you go to NA .75 and a wavelength of 750 nm, at a spacing of 
about 0.6 micrometres I get the 25% contrast on both the "Airy 
Function" and the readout below the "Intensity Plot", but in the 
"Intensity plot" itself, it is very clear that the peak of one Airy 
figure is well outside the first dark ring of the other.

More messing led to other situations where the "Contrast" reading 
was, say, 98% but the "Intensity Plot" showed nothing close to a 
black area between the peaks.

Is this just a math error in the otherwise very beautiful learning 
tool or am I missing something?

Maybe this is why I try to stay away from discussions of "resolution" 
and try to stick to the Contrast Transfer Function" where it becomes 
clear that features that are twice or even 3x the "resolution" in 
size are represented in the image at lower contrast than are larger 
objects.

Cheers,

Jim P.
-- 
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Prof. James B. Pawley,               		            Ph.  608-263-3147 
Room 223, Zoology Research Building,               
FAX  608-265-5315
1117 Johnson Ave., Madison, WI, 53706  
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3D Microscopy of Living Cells Course, June 13-25, 2009, UBC, Vancouver Canada
Info: http://www.3dcourse.ubc.ca/	     Applications due by March 15, 2009
	       "If it ain't diffraction, it must be statistics." Anon.