[OpenSPIM] Open SPIM

[Johannes Schindelin]

Dear John,

On Tue, 4 Jun 2013, Peter Gabriel Pitrone wrote:

> The lightsheet with the stated optics is around 7-10 um. We are working
> on a lightsheet thickness calculator that we will put on the wiki as
> soon as it it finished.

To enhance on that comment until the time when Dr Jan chimes in, this is
how we measure the light-sheet thickness: we use the same mirror as for
the light-sheet calibration described here:

	http://openspim.org/Light-sheet_Calibration

(unfortunately, the description of the last steps of that page have not
yet been completed.)

In the last steps, what we do is to use an improvised transmission light
(we really use a reading light and shine that through the sample chamber)
to get the mirror into focus both with the transmission light and the
light-sheet by having the mirror (also called grid on the page because it
is a gridded mirror) at 45 degrees such that the light-sheet is reflected
directly into the camera.

At that stage, the light-sheet thickness can be measured exactly by
calibrating the pixel spacing with the known grid spacing and the simply
counting the number of pixels of the width (because the light-sheet is now
directed directly into the camera, parallel to the detection axis).

The height of the light-sheet is configurable to a certain extent: you can
make it narrower or larger by adjusting the iris in the last part of the
illumination axis. Of course, you still want it to be relatively uniform
over the height; we found it reasonable uniform in the field of view we
use (and we made it a little larger than that). Although I have to admit
that we never came around to *really* quantify this.

Ciao,
Johannes