Download - Ccd principles(nnm)
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www.stitairdd.org © 2009 N. N. Maurya
CCD is a kind of transducer which converts optical image into electrical signal.
www.stitairdd.org © 2009 N. N. Maurya
+10 V
eeeeeInversion Layer
Light
Reduced
Depletion
Layer
P
Majority Carrier Holes
Now V = 10 volts,
free holes repelled deeper
into the substrate
a depletion layer is formed
below the electrode
Depletion Layer
When CCD Exposed to light photo
electrons appears in inversion layer
(potential well)
& Depletion layer get reduced
Substrate
+10 V
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Charge packetp-type silicon
n-type silicon
SiO2 Insulating layer
Electrode Structure
1. Photons entering the CCD create electron-hole pairs.
2. The electrons are then attracted towards the most
positive potential in the device where they create ‘charge
packets’
3. Each packet corresponds to one pixel
pix
el
bo
un
da
ry
pix
el
bo
un
da
ry
inco
min
g
ph
oto
ns
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Charge packets moves through the CCD device
Charge packets to voltage conversion
Finally delivered to output amplifier
Once the charge has been generated, it accumulates in the potential well, under the capacitor.
The control circuitry shifts the accumulated charge to the end of the row, to the input of a charge amplifier.
www.stitairdd.org © 2009 N. N. Maurya
a b c a
+0.5V +0.5V+8V+4V
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__ _
+0.5V +8V +0.5V +0.5V
a b c a
+0..5V +0.5V+8V+0..5V
a b c a
__ _
ElectrodeInsulation Layer
Depletion Layer
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+2 V +2 V +2 V +2 V +4 V +2 V
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There are three different types of CCD chips used as a pick up device for CCD cameras: Interline transfer type
Frame transfer type
Frame interline transfer type The only different about these types is the way charge is
collected or transferred. CCD cameras with good resolution offers about 4,00,000 pixels or CCD element
www.stitairdd.org © 2009 N. N. Maurya
www.stitairdd.org © 2009 N. N. Maurya
www.stitairdd.org © 2009 N. N. Maurya
www.stitairdd.org © 2009 N. N. Maurya
www.stitairdd.org © 2009 N. N. Maurya
Connection pins
Gold bond wires
Bond pads
Silicon chip
Metal,ceramic or plastic packageImage area
Serial register
On-chip amplifier