CCD-world: cross-talk in multi-channel CCDs

[Barry Starr]

The following was posted to CCD-world:

Hi Roy,

Photon-forager, I like that, maybe Photon-phorager or Foton-forager...

Anyway back to the matter at hand...

The first thing I'd ask is have you tested your acquisition system
performance separately from the CCD.  If you still have the problem it's
not the device (or only the device at least at the level your currently
experiencing) if it goes away then either it's the CCD or your interface
to the CCD.  Split the chain if you can to see what's your offending
party....

Regarding decoupling of video amplifiers, often the addition of more
capacitance does not improve your decoupling due to the resonant
frequency issues of non-ideal capacitors.  Often you need to parallel
0.01uf ceramics with 1uF tantalums (surface mount best, extremely short
leads mandatory) to get solid wideband decoupling.  There is a wonderful
application note by Analog Devices AN-202 "An IC Amplifier User's Guide
to Decoupling, Grounding and Making Things Go Right for a Change" by
Brokaw that's a classic (great title as well).  But there's a  load of
good info for Analog Devices, Burr-Brown, and Linear Technology
application notes in this area.


Good Luck,

Barry

Roy Tucker wrote:
> 
> The following was posted to CCD-world:
> 
> Dear Fellow Photon-Foragers,
> 
>         I am participating in the up-grading of the GONG
> (http://www.gong.noao.edu) video data system which includes a new camera
> (Silicon Mountain Designs 1M60-20) with a Thomson THX7887A imager
> (frontside 1024 square array, four channels of 1024 x 256, 14 um pixels, 60
> frames per second, 12 bits per pixel). Our data acquisition algorithm
> consists generally of co-adding images for 60 seconds into three or six
> accumulation buffers in synchrony with the angular orientation of rotating
> optical elements in the system. Co-adding 600 or 1200 12-bit numbers
> produces approximately 23-bit results.
> 
>         We are noticing a low-level (far below the 12-bit resolution of an
> individual image) cross-talk between the four output channels of the
> camera. The phenomenon is non-linear in that it does not appear until a
> threshold luminance level is reached. Our initial hypothesis that there
> were insufficient bypass capacitors associated with the video amp power
> supply rails and CCD bias voltages appears to have been disproven by an
> experiment involving the installation of larger caps. There appeared to be
> no beneficial effect.
> 
>         Although not a serious problem, we would like to reduce or eliminate the
> effect if possible. Before proceeding further with our testing, we thought
> it might be wise to consult the CCD engineering community to see if anyone
> else has seen such an effect and if they could indicate to us if it is due
> to the CCD support electronics or an inherent property of this particular
> CCD imager or multi-channel CCDs in general.
> 
>         Thank you very much for your attention.
> 
>                                         Best regards,
>                                           Roy Tucker
> 
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-- 
_____________________________________________________________________________

Barry Michael Starr                                    
starr at cfht.hawaii.edu
Canada France Hawaii Telescope                          Ph: 808-885-3139
PO BOX 1793  Kamuela, HI 96743                          Fax:
808-885-7288
_____________________________________________________________________________
- -- CCD-world -- --
CCD-world is fully moderated. Send posts to CCD-world at astro.ku.dk
Standard replies will go to the list; address personal replies manually.
For more information, please go to:  http://www.not.iac.es/CCD-world/