[OpenSPIM] Slit aperture function

[phil laissue]

Dear SPIM folks,

i) A big Thank You to the many people involved in setting up this fantastic
source! It gave me a lot of confidence in building my own light sheet,
knowing there's a great reference like this - excellent instructions,
theoretical background, software and all - seriously genius!

ii) Apologies in advance, this might expand a bit - but I would like to get
some clarification on the slit, and its influence on the light sheet. So
the slit truncates the expanded Gaussian beam (1), already forming a light
sheet (2). The cylindrical lens then focusses this sheet in one dimension.
An a- or apochromatic objective lens can be used after that (3) for further
focussing. Alternatively, a cylindrical lens can be used on its own to
create a light sheet (4) (stop me if I'm off).
Now, the questions are these:
   a) A wide open slit shortens the Rayleigh range. But it also seems to
have less uniformity not only along the axis of propagation, but also
perpendicular to it (i.e. travelling along the waist), since the slit
aperture produces an 'Airy line' with higher order diffraction patterns
causing minima and maxima. Is there any description of this in the
literature?
   b) Conversely, if a thicker (= larger waist) light sheet with less
intensity is acceptable, the slit can be closed narrowly, and the central
zeroth order maximum expands. Is this, as appears to me, the most uniform
part of the light sheet? I couldn't find any information on the aperture of
the slit.
   c) There is a host of different formulae for calculating the theoretical
dimensions of a light sheet (e.g. 5,6). The openSPIM calculator widget of
Peter and Tobias mentions two slits, horizontal and vertical. Which formula
underpins this? And why two slits?

I currently don't use a slit for my meso-/macroscopic setup for corals, but
am intrigued by this (and discussed it with some SPIMmers here, without
really getting anywhere).

With many, many thanks

Philippe


(1) Saghafi et al., J. Biophotonics 3, No. 10-11, 686-695 (2010)
(2) Siedentopf & Zsigmondy, 1903
(3) discussed e.g. in this forum, Tue Jul 2 07:25:13 CDT 2013, "About the
cylindrical lens"
(4) e.g. Voie et al., 1993 (OPFOS)
(5) http://silver.neep.wisc.edu/~shock/tools/ray.html
(6) http://www.calctool.org/CALC/phys/optics/f_NA


_____________________________________
Philippe Laissue, PhD, Bioimaging Manager
School of Biological Sciences, Room 4.17
University of Essex, Colchester CO4 3SQ, UK
(0044) 01206 872246 / (0044) 07842 676 456
plaissue at essex.ac.uk
privatewww.essex.ac.uk/~plaissue
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://openspim.org/pipermail/openspim/attachments/20140408/c5aba54c/attachment-0002.html>