Ccd principles(nnm)


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


+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


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


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.


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

__ _

ElectrodeInsulation Layer

Depletion Layer


7

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


8

+2 V +4 V +8 V +2 V +2 V +2 V


9

+2 V +4 V +8 V +2 V +2 V +2 V


10

+2 V +2 V +8 V +2 V +2 V +2 V


11

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


12

+2 V +2 V +4 V +8 V +2 V +2 V


13

+2 V +2 V +2 V +8 V +2 V +2 V


14

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


15

+2 V +2 V +2 V +4 V +8 V +2 V


16

+2 V +2 V +2 V +2 V +8 V +2 V


17

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


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


Connection pins

Gold bond wires

Bond pads

Silicon chip

Metal,ceramic or plastic packageImage area

Serial register

On-chip amplifier

Ccd principles(nnm)

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