[OpenSPIM] pinhole location and diameter to clean up the laser beam

[Monika Pawłowska]

I currently use a low-budget laser diode with terrible beam profile, so  
I'm forced to use a pinhole, but in fact I have a third telescope for  
that, before the entire setup. But I suppose you can try the first  
telescope. In the second telescope, which is after the cylindrical lens,  
the beam has the shape of a line, not a point, so that won't work. The  
size should be calculated dependent on your laser. Describing how to do it  
is slightly too long for an email, but by googling "beam cleaning pinhole  
size" I found for instance this:
http://www.academia.edu/5558409/Laser_beam_cleaning_Spatial_filtering_of_laser_beam_

However, if you do this you'll have a circular beam in the middle and  
diffraction rings around it, like here:
https://en.wikipedia.org/wiki/Airy_disk
so you get rid of one problem and introduce another. I suppose you'd have  
to characterize the light-sheet with and without the pinhole to see if it  
helps.

This is from me, maybe somebody has more to add or correct me if I'm wrong.

Regards,
Monika


W dniu .09.2015 o 11:48 Claire Lionnet <claire.lionnet at ens-lyon.fr> pisze:

> Hi everyone,
>
> We've got an openspim almost ready to work here in France. We are just  
> concerned by the not-very-circular laser beam. Did somebody used a  
> pinhole to clean up the beam ? What would be the best location for a  
> pinhole in this setup : in the first or the second telescope ? And what  
> should be its diameter ? (sorry for the basic questions, not an optical  
> engineer !).
> Thanks in advance for your help,
>
> Claire
>


-- 
Dr Monika Pawłowska
Nencki Institute
02-093 Warsaw
Pasteura 3
Poland