A CCD converts an optical image into electrical signals by creating charge packets corresponding to each pixel when photons strike the CCD. The charge packets are shifted through the CCD to an output amplifier. There are three main types of CCD chips used in cameras - interline transfer, frame transfer, and frame interline transfer - which differ in how they collect and transfer charge. A high-resolution CCD camera can have up to 4 million pixels or CCD elements.

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CCD is a kind of transducer which
converts optical image into electrical
signal.

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+10 V
eeeee
Inversion 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 packet
p-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
pixel
boundary
pixel
boundary
incoming
photons

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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.

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a b c a
+0.5V +0.5V+8V+4V
_
_ _
_
_ _
+0.5V +8V +0.5V +0.5V
a b c a
+0..5V +0.5V+8V+0..5V
a b c a
_
_ _
Electrode
Insulation Layer
Depletion Layer

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+2 V +4 V +2 V +2 V +2 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

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Connection pins
Gold bond wires
Bond pads
Silicon chip
Metal,ceramic or plastic packageImage area
Serial register
On-chip amplifier