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Technical Discussions
Ulrich Storz
Ulrich Storz
01:28 Nov-17-2000
low noise, low resolution, high pixel size CMOS sensor

Folks,

for a new application in optical imaging of nervous tissue with voltage
sensitive dyes we are looking for a CMOS sensor with the following
features:

- spatial resolution at least: 64 x 64
- frame rate (at least of a 64 x 64 subframe): > 1kHz
- low noise(comparable to a CCD), AD-rate at least 12 bits,
better 14 bits

Up to now, our membrane potential signals are measured with a single
photodiode. The signals are somehow peculiar because they consist of a
huge offset intensity (either fluorescene or absorbance) to which a
small signal (max. 0.3 % of the offset) is added.
Usually, Photodiode arrays with parallel amplification are used for
that purpose. However, they are extremely expensive and offer only low
resolution (max. 1000 Pixel).
They normally use 12 bits, but offer baseline subtraction either by
AC-coupling or sample- and hold circuits, so that an effective AD-rate
of more that 17 bits is achieved.
For low-light conditions, cooled CCD with large pixels (approx 30 x 30
µm, deep wells (500,000 electrons/msec) and only small pixel numbers
(approx 7000 Pixels) are used, but these are as well extremely
expensive. A CCD Chip often used is the Marconi CCD 039 (80 x 80 pixel,
24 µm x 24 µm pixel size). Check under:

http://www.marconitech.com/products/ccd/ccdprod.html

We have been told that at these frame rates anything else than 10 bits
does not make sense, because shot noise will become dominant then.
For that reason the CCDs and the PDAs used have quite large pixel
dimensions and therefore only low pixel numbers.
I think with high-resolution, small pixel size sensors one could overcome this problem by virtually binning of several
pixels and thereby increase pixel size.

We would like to know if anybody knows a company that can provide a CMOS
device with he needed features.

Ulrich Storz

**********************************
Dipl. Biol. Ulrich Storz
Institute for Zoophysiology
Muenster University
Hindenburgplatz 55
48143 Muenster
Germany

fax.: ++49 - 251 - 832 38 76
tel.: ++49 - 251 - 832 17 26
e-mail: storz@uni-muenster.de
**********************************


 
 Reply 
 
Nikolay Krantov
Nikolay Krantov
03:17 Jan-05-2001
Re: low noise, low resolution, high pixel size CMOS sensor
low-light conditions, cooled CCD with large pixels (approx 30 x 30
: µm, deep wells (500,000 electrons/msec) and only small pixel numbers
: (approx 7000 Pixels) are used, but these are as well extremely
: expensive. A CCD Chip often used is the Marconi CCD 039 (80 x 80 pixel,
: 24 µm x 24 µm pixel size). Check under:

: http://www.marconitech.com/products/ccd/ccdprod.html

: We have been told that at these frame rates anything else than 10 bits
: does not make sense, because shot noise will become dominant then.
: For that reason the CCDs and the PDAs used have quite large pixel
: dimensions and therefore only low pixel numbers.
: I think with high-resolution, small pixel size sensors one could overcome this problem by virtually binning of several
: pixels and thereby increase pixel size.

: We would like to know if anybody knows a company that can provide a CMOS
: device with he needed features.

: Ulrich Storz

: **********************************
: Dipl. Biol. Ulrich Storz
: Institute for Zoophysiology
: Muenster University
: Hindenburgplatz 55
: 48143 Muenster
: Germany

: fax.: ++49 - 251 - 832 38 76
: tel.: ++49 - 251 - 832 17 26
: e-mail: storz@uni-muenster.de
: **********************************




 
 Reply 
 

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