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

[B.Nagaraja Naidu]

The following was posted to CCD-world:

Dear Roy Tucker,

If you are using same bias supplies for all four channels, you can try
using 
different supplies for individual channels. Like for example, use separate 
VDD supplies for each channel, separate supplies for VRD and so forth. If
not eliminated completely, it will at least reduce the cross-talk
significantly.  

Naidu


On Wed, 22 Mar 2000, 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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