This document summarizes charge coupled devices (CCDs). CCDs are light-sensitive integrated circuits that convert light into electrical charge. They are used in digital cameras, video cameras, and astrophotography to capture light and convert it to digital data. The document describes the different types of CCDs and explains their working principle. It details the three phases of image capture - clearing, exposure, and readout. Applications and advantages of CCDs are also discussed.

1. RAGHU ENGINEERING COLLEGE
(AUTONOMOUS)
DAKAMARRI
M UDAY KUMAR
17981A04B8
ECE-C
TECHNICAL SEMINAR ON
CHARGE COUPLED DEVICES

2. OBJECTIVE
• Study and observe working and application of
charged coupled devices

3. INTRODUCTION TO CCD’s
• CCDs are used to convert light into a digital
value
• The CCD captures light and converts it to
digital data that is recorded by the camera.
• It can be defined as a light-sensitive integrated
circuit imprinted on a silicon surface to form
light-sensitive elements called pixels, and each
pixel is converted into an electrical charge.

4. TYPES OF CCD’S
There are different CCDs such as
• Electron multiplying CCDs,
• Intensified CCD,
• Frame-transfer CCD
• Buried-channel CCD.

5. WORKING
• They transfer incoming photons into an electrical
charge in the CCD chip
• The photons are received in a photoactive region
of silicon
• A lens is used to focus the light onto the silicon
• A charge is accumulated in the capacitors
proportional to the light intensity
• Each photo site corresponds to an
individual pixel in the final image and photo sites
are often referred to simply as pixels.

6. • Each “photo sites” will refer to the CCD chip
and “pixels” will refer to an image.
• When a photon of light strikes the surface of
certain metal materials the energy imparted
by the photon can release an electron from
the metal.
• In a CCD, this electron is stored within the
walls of a photo site

7. HOW TO GET DATA FROM CCD’S
• Photo sites are read out, one row at a time,
into a serial register along the bottom of the
CCD array.
• The serial register then transfers the charge
from each photo site to an output node.
• From there the charge is sent to the camera’s
electronics unit where the electrons are
digitized.

8. 8
CCDs can be used to collect an image in one of three ways,
either one pixel at a time, one row at a time, or as an entire area
at once.

9. How is an image made with a CCD
chip?
• There are three main phases:
 Clearing phase
Exposure or integration phase
 Readout phase
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10. How a CCD chip registers image?
• The telescope projects an image on the CCD chip. High
intensity areas will produce more charge in the pixels than
low intensity areas.
• The amount of charge in every pixel makes the image.
• The computer can read this charge and convert it to an
image
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oThe value in
every pixel gives
the charge,
which is related
to the light
intensity.

11. Clearing phase
• Mostly you don’t have a
shutter in your camera, this
means that there is always
light falling on the CCD chip.
• When you want to make an
image, all existing charge has
to be removed from the pixels.
• The lowest line will move the
charge to a clearing line,
where it will be removed.
• When all lines are shifted
away, there is no charge left
anymore
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12. Exposure or integration phase
• The lens projects the image on the CCD chip, so charge
will accumulate in the pixels.
• The longer you wait, the more light will be registered
by the chip.
• This phase controls the exposure time, also called:
integration time,
• because the chip integrates the amount of light in a
certain period. With lunar and planetary photography
it usually takes a few tenths of a second, but it can take
minutes or even hours

13. Readout phase
• To get the image in your computer, it
will have to read the amount of charge
of every pixel.
• There is a device, the charge detection
node, in the CCD chip that is able to
measure the charge of a pixel
• When all pixels of the line are
measured, all lines are shifted one line
down.
• Then again the lowest line can be
measured. This will be repeated until
all lines are measured.
• The computer can read the
measurements through the camera
electronics 13

14. Applications
• CCDs are used in digital cameras, optical
scanners and video cameras as light-sensing
devices.
• CCD cameras used in astrophotography.
• CCDs are typically sensitive to infrared light,
which allows infrared photography, night-vision
devices , video recording/photography.
• CCD are use to take exposures of galaxies and
nebulae
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15. Advantages
o Relative simple
o More sensitive than photographic film
o Cheaper to replace if failure
o Modularity-easy upgrades
o Detector costs simple
o No chemical processing is needed
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16. DISADVANTAGES
• CCD sensors consume much much more power.
• HD video-less pixel rates.
• CCDS are expensive as they require special
manufacturing.
• CCD sensors may be wired/wireless-mastering the
use requires some effort and learning period

17. REFERENCE
• https://www.elprocus.com/know-about-the-
working-principle-of-charge-coupled-device/
• https://en.wikipedia.org/wiki/Charge-
coupled_device