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Date: | Wed, 28 Nov 2007 18:00:03 +0200 |
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Search the CONFOCAL archive at
http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
Nuno Moreno wrote:
> Search the CONFOCAL archive at
> http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>
> Hi!
>
> If it is for cell imaging you might consider a BT camera.
>
> Forcing the previous point, which I thing is very important:
>
> I'm having the same problem with an ORCA AG with ImagePro Plus. What I
> have now is a small program called by macros that controls an external
> shutter via TTL, which makes a delay till it opens the shutter. I found
> out that the driver takes almost 500ms to get the camera taking a
> picture which is unacceptable! However this solution is far from being
> elegant and sometimes the pseudo synchronization fails! Is this a
> Hamamatsu problem? With a Hamamatsu BT1024 which has a QE>90% it
> happends the same thing with metamorph.
>
> Regarding to the previous commercial response, does anyone have a
> cheaper and more flexible solution?
>
The way to do this is by directly controlling the shutter from the chip-exposure
line of the camera. This bypasses the software completely. Most high end cameras
have such a control line, although it goes by various names. I know that the
PCO sensicam series, Roper Coolsnap series, Orca AG (probably the other Orcas
also), QImaging, all have such a line. I use it with a Uniblitz shutter. You
still have to worry about the the 5-10ms shutter opening and closing time. In a
camera like the PCO (again, probably in others) the camera can be set up to
start integrating after a delay time set by the user. This increases your sample
exposure by 10-20ms, but that is really not bad compared to the 1-2 seconds that
some software controlled systems waste before closing the shutter.
Of course, if you connect the control line directly to a system like CoolLed or
an AOTF, you can get very fast switching.
You may need to build a little bit of digital logic. For example, when doing a
live preview for focusing, we want the shutter to remain open continuously. But
when using the chip expose line, the shutter will cycle rapidly as the camera
switches between integration and image transfer. Therefore, we set it up so that
in live preview mode the Uniblitz system was commanded to stay open independent
of the hardware control line. I also added an external switch that could force
the input to the Uniblitz control to be on (ie, I OR'ed the camera control line
with a manually switched voltage). This was a matter of a few NAND gates on two
74LSxx series integrated circuits (your electronics shop will certainly have
these).
I know that this solution is used in other labs, so maybe I am missing something
in this thread about the difficulty that is being discussed.
--aryeh
--
Aryeh Weiss
School of Engineering
Bar Ilan University
Ramat Gan 52900 Israel
Ph: 972-3-5317638
FAX: 972-3-7384050
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