Hole in CCD chip?

Greetings all.

I have a question about CCD chips. I have very little knowledge of how
they work electronically and I was just wondering (obviously for
purposes other than astrophotography): Is it possible to precisely cut
a hole in the middle of a CCD chip and still function, albeit without
the center pixels?

This would be used to measure reflection angles off crystal surfaces
with a laser, but to avoid refractive effects, the laser would have to
go through the center of the chip and reflect back to another part of
the chip, where its distance from the hole would be measured by
computer.

Basically, is each pixel an independent electronic entitity or are
they intricately connected so that if one pixel is removed, that
destroys a larger-scale circuit?

Thanks,
George

George Wilkie wrote:
Greetings all.

I have a question about CCD chips. I have very little knowledge of how
they work electronically and I was just wondering (obviously for
purposes other than astrophotography): Is it possible to precisely cut
a hole in the middle of a CCD chip and still function, albeit without
the center pixels?

This would be used to measure reflection angles off crystal surfaces
with a laser, but to avoid refractive effects, the laser would have to
go through the center of the chip and reflect back to another part of
the chip, where its distance from the hole would be measured by
computer.

Basically, is each pixel an independent electronic entitity or are
they intricately connected so that if one pixel is removed, that
destroys a larger-scale circuit?

At the very least you'd lose all the pixels "upstream" from the hole,
since the charge from each pixel is handed from pixel to pixel
"bucket-brigade" style until it reaches the edge row for clocking
through the on-chip amplifier. There might be other issues related to
heating of material sin neighboring pixels during the cutting
as well. You might want to look at CMOS detectors for this.
Their pixels are individally addressable, but I wonder whether
there are connections that would still be broken in
one or both directions.

Is there a reason that the beam can't barely miss the detector's edge and
still pick up the desired diffracted radiation? You might be able
to use two edge-butted devices to give a corner:

XXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXX

XXXXXX
XXXXXX
XXXXXX

with a smallish spacing in between that the alser could go through.

Bill Keel

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"gw" == George Wilkie writes:

gw I have a question about CCD chips. I have very little
gw knowledge of how they work electronically and I was just
gw wondering (obviously for purposes other than
gw astrophotography): Is it possible to precisely cut a hole in
gw the middle of a CCD chip and still function, albeit without
gw the center pixels?

The answer is "no". You'll be cutting through who knows what in the
way of electronics, shorting who knows what else and generally ruining
the whole chip.

gw Basically, is each pixel an independent electronic entitity or
gw are they intricately connected so that if one pixel is
gw removed, that destroys a larger-scale circuit?

Yes, you would destroy parts that would likely render the entire chip
non-functional.

roland
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PGP Key ID: 66 BC 3B CD
Roland B. Roberts, PhD RL Enterprises
6818 Madeline Court
Brooklyn, NY 11220

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"George Wilkie" wrote in message
om...
Greetings all.

I have a question about CCD chips. I have very little knowledge of how
they work electronically and I was just wondering (obviously for
purposes other than astrophotography): Is it possible to precisely cut
a hole in the middle of a CCD chip and still function, albeit without
the center pixels?

This would be used to measure reflection angles off crystal surfaces
with a laser, but to avoid refractive effects, the laser would have to
go through the center of the chip and reflect back to another part of
the chip, where its distance from the hole would be measured by
computer.

Basically, is each pixel an independent electronic entitity or are
they intricately connected so that if one pixel is removed, that
destroys a larger-scale circuit?
It destroys a larger scale circuit.
Your best bet, would be to have a small front silvered mirror, with a hole
in this, and place the CCD at right angles to your incoming light path.

Best Wishes

On 24 May 2004 12:37:56 -0700, (George Wilkie) wrote:

I have a question about CCD chips. I have very little knowledge of how
they work electronically and I was just wondering (obviously for
purposes other than astrophotography): Is it possible to precisely cut
a hole in the middle of a CCD chip and still function, albeit without
the center pixels?

No, the hole will cut the gate clock lines and no charge will get transported
past the cut rows. You will also lose the columns the hole cuts through.
Finally, if there is any kind of ABG structure you will cut through those gate
clocks, too.

You might consider a mosaic of 4 CCD dice mounted 2x2 almost touching, leaving a
center hole.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Well

there is one way to sorta create a "hole" on a ccd.....

have your primary optical system focused on a "diagonal" mirror....ie the
mirror lies at or very near the focal plane......

The diagonal mirror has DOES have a real hole in it.....

Then you use yet another series of lenses or mirrors to reimage the first focal
plane onto the CCD.....now the ccd has an image plane with a "hole/blank image
space" on it.... and the light/image that passed through the real hole is
available for whatever purpose that was intended in the first place...

Of course there are problems and issues with doing it this way or other related
ways as well as performance trade offs....but you can get the functional
equivalent of a CCD with a "hole" in it.... but probably still easier and
cheaper than butting up 4 CCDs or trying to make a CCD with a real hole in
it....

take care

Blll

George Wilkie wrote:
Basically, is each pixel an independent electronic entitity or are
they intricately connected so that if one pixel is removed, that
destroys a larger-scale circuit?

You will destroy larger scale circuitry.

How about putting a tiny 45° angled mirror in the center of the ccd and
sending the laser in from the side? This would give you a laser beam coming
straight from the center of the ccd, and there would be a "hole" in the
shadow of the mirror, without actually breaking the CCD.

Bart

It's like drilling a hole in your head. It would destroy it. Maybe, can be
MFG. that way, if there is an aplication for it.
Placing the pixels in a circuler array.
But, I'm not a CCD expert either.

Julius

"George Wilkie" wrote in message
om...
Greetings all.

I have a question about CCD chips. I have very little knowledge of how
they work electronically and I was just wondering (obviously for
purposes other than astrophotography): Is it possible to precisely cut
a hole in the middle of a CCD chip and still function, albeit without
the center pixels?

This would be used to measure reflection angles off crystal surfaces
with a laser, but to avoid refractive effects, the laser would have to
go through the center of the chip and reflect back to another part of
the chip, where its distance from the hole would be measured by
computer.

Basically, is each pixel an independent electronic entitity or are
they intricately connected so that if one pixel is removed, that
destroys a larger-scale circuit?

Thanks,
George

As the others have mentioned, the circuitry on the chip will be damaged by
such an operation.
What you want to do is either use a small mirror to reflect the light or a
beamsplitter cube (single surface rather than a pellicle or plate double
surface) to put the laser light into the proper path.

--
Bob May
Losing weight is easy! If you ever want to lose weight, eat and drink less.
Works every time it is tried!

"Szaki" wrote in message
news:7aKsc.58142$gr.5707108@attbi_s52...
It's like drilling a hole in your head. It would destroy it. Maybe, can be
MFG. that way, if there is an aplication for it.
Placing the pixels in a circuler array.
But, I'm not a CCD expert either.

Julius
Yes, such a sensor can be built. There are some used in particular
applications. The sensors used in some of the better autofocus SLR's for the
focussing system, almost meet the requirements, but I have never seen these
sold as a seperate item. Most of these only have a relatively small number
of pixels.

Best Wishes

"George Wilkie" wrote in message
om...
Greetings all.

I have a question about CCD chips. I have very little knowledge of how
they work electronically and I was just wondering (obviously for
purposes other than astrophotography): Is it possible to precisely cut
a hole in the middle of a CCD chip and still function, albeit without
the center pixels?

This would be used to measure reflection angles off crystal surfaces
with a laser, but to avoid refractive effects, the laser would have to
go through the center of the chip and reflect back to another part of
the chip, where its distance from the hole would be measured by
computer.

Basically, is each pixel an independent electronic entitity or are
they intricately connected so that if one pixel is removed, that
destroys a larger-scale circuit?

Thanks,
George