Experimental 2

After a visit from the Leica rep today we finally determined that the rather firmly attached diffuser can be replaced at low cost and, after several less robust methods failed, did indeed wind up assaulting the little fucker with a hammer. In consequence of which, I am able to report at least partial success in the matter of projecting a test pattern through the microscope onto a fluorescent sample.

Behold!

Although the automatic exposure on the camera with which these images were captured is a bit off, the pattern seems to be getting through the low power 10x objective with -- given the Heath Robinson nature of our test rig -- surprisingly adequate focus and resolution. If we blow up the relevant section of the image, you can see that even the 18/mm grating is just about resolved:

Since our tube lens focal length is the same as the internal one¹, we should get a demagnification equivalent to the nominal rating of the objective, in this case 10x, so we're seeing 180 lines/mm at the sample, or a pitch of about 5.5 microns. That's not anywhere near the diffraction limit, but we wouldn't expect that anyway for this objective. It might be enough to get at least some optical sectioning benefit, though.

The story with the 40x objective is not so happy:

We're again losing a lot of detail as the camera makes a hash of exposing the underlit, mostly-dark image, but it's clear the finer grating pitches are getting lost in the melée. Still, this is a very rough test and there are plenty of ways to increase the precision. I reckon we should be able to get the 10/mm grid resolved easily enough -- but that still only gives a 2.5 micron pitch, not really troubling the diffraction limit.

This microscope doesn't have a 100x objective attached at the moment, though I may see if I can borrow one to test with. On this basis, though, I wouldn't expect great results. I think it's going to take (someone else) quite a bit of effort to start getting adequately resolved projections of illumination patterns made up of pixels that are at a 5-10 micron pitch before demagnification.

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1 In the unlikely event that anyone actually cares what this means, say so in the comments and I'll explain it.
Posted by matt at July 25, 2007 08:59 PM