Electricity & Electronics, 10th Edition Page 409 (409 of 528)

Chapter 23 Television and Video Display Units 409
use HDTV terminology but do not produce the desired
HDTV effect. For example, a television system may be
capable of receiving a transmitted HDTV broadcast, but
incapable of displaying the higher resolution HDTV
image.
Digital Camera Technology
Traditional analog television uses vacuum tube
imaging to capture images, while HDTV uses the
charged coupled device (CCD). The CCD is an inte-
grated circuit consisting of an array of photo sensors that
convert light from a camera's focused image to electrical
energy, Figure 23-35. The level of electrical energy is
directly proportional to the level of light captured by the
photo sensors. The CCD converts the individual packets
of electrical charge into a series of analog signals repre-
senting the level of light amplitude at each photo sensor
location. An analog-to-digital converter (ADC) converts
the series of analog signals to digital signals. The digital
pattern can then be sent to a block of computer memory
to be stored as a still image, recorded to CD or DVD,
transmitted across a computer network, or broadcast
using the existing assigned television bands.
For full-color images and higher resolutions, three
sets of CCD sensors are used. A beam splitter inside the
camera separates the incoming light into three colors:
blue, red, and green, Figure 23-36. Each color is sent
to a corresponding CCD. The three images are then
CCD Array
CCD Array
Beam splitter
Captured light
from image
Figure 23-36. A three-CCD system.

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Chapter 23 Television and Video Display Units 409
use HDTV terminology but do not produce the desired
HDTV effect. For example, a television system may be
capable of receiving a transmitted HDTV broadcast, but
incapable of displaying the higher resolution HDTV
image.
Digital Camera Technology
Traditional analog television uses vacuum tube
imaging to capture images, while HDTV uses the
charged coupled device (CCD). The CCD is an inte-
grated circuit consisting of an array of photo sensors that
convert light from a camera's focused image to electrical
energy, Figure 23-35. The level of electrical energy is
directly proportional to the level of light captured by the
photo sensors. The CCD converts the individual packets
of electrical charge into a series of analog signals repre-
senting the level of light amplitude at each photo sensor
location. An analog-to-digital converter (ADC) converts
the series of analog signals to digital signals. The digital
pattern can then be sent to a block of computer memory
to be stored as a still image, recorded to CD or DVD,
transmitted across a computer network, or broadcast
using the existing assigned television bands.
For full-color images and higher resolutions, three
sets of CCD sensors are used. A beam splitter inside the
camera separates the incoming light into three colors:
blue, red, and green, Figure 23-36. Each color is sent
to a corresponding CCD. The three images are then
CCD Array
CCD Array
Beam splitter
Captured light
from image
Figure 23-36. A three-CCD system.

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408 Electronic Communication and Data Systems
The FCC’s approval in 1996 of a digital television
standard was the first step toward an improved and a
higher quality picture. Although the switch to digital has
progressed slowly, with more and more television stations
switching to digital broadcasts and many digital television
formats emerging, high definition television (HDTV) has
become the dominant digital television technology.
HDTV allows for higher resolutions and a wider dis-
play screen than an analog display system. HDTV uses
digital broadcasting techniques, allowing more informa-
tion-rich data to be transmitted by airwaves than by ana-
log broadcasts. Digital broadcasting can broadcast multi-
ple channels in the same bandwidth as that used for one
analog channel. Broadcasting multiple channels is
referred to as multicasting. Multicasting allows not only
for the image to be broadcast, but also for two to four
channels to be broadcast in the same single-channel
bandwidth. The additional channels can be used to trans-
mit additional images, resulting in “picture-in-picture”
and information such as stock prices, weather reports,
sports scores, or background information about the actors
in the movie being viewed. Any information found on the
Internet can be incorporated into the display screen.
When additional information is transmitted along with
the video image, it is referred to as datacasting. You will
soon likely be able to integrate a digital camera into the
system so that you can see the baby sleeping in the next
room while watching your favorite television show.
To be considered a complete HDTV system, three
major system components are required, Figure 23-34:
• A digital camera to record the images at the higher
resolution.
• A digital receiver (HDTV tuner) to convert received
broadcasts into image and sound.
• A display unit capable of producing images at the
high definition TV resolution.
If any of the three major parts are missing, the
HDTV system is incomplete and will not produce an
HDTV picture. There are many television variations that
Figure 23-34. Major components required for a
complete HDTV system.
Captured light
from an image
Photo sensor
Level of
electrical charge
Storage
device
Memory
Broadcast
CCD Array
Analog Digital
Analog-to-digital
converter
Figure 23-35. A CCD as it captures an image.

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410 Electronic Communication and Data Systems
overlaid, producing a picture rich in color. Since the full
array of each CCD is used for each color, the three-CCD
camera is capable of higher HDTV resolutions.
HDTV Picture Quality
The most impressive attribute of HDTV is the pic-
ture's visual quality. To compare the HDTV image to the
analog television image, we must first convert the typical
analog image to an equal digital resolution.
The National Television Standards Committee
(NTSC) formulated the standards for analog television
and video in the United States. The NTSC standard calls
for 525 scan lines at a 60 Hz refresh-rate based on the
interlace technique. NTSC is not compatible with most
computer video systems and must be converted before it
can be displayed. The Advanced Television Systems
Committee (ATSC) was established in 1983. The com-
mittee spent years developing standards that were eventu-
ally adopted by the FCC for digital television broadcast-
ing and receivers. These standards have been designed to
eventually replace the NTSC standards.
There are 18 scanning formats described in the
ATSC standards. Variations in the standards are derived
from concerns about interlace scanning and progressive
scanning, frame rates, and aspect ratio. Earlier, in the sec-
tion about the analog television system, you learned
about interlacing. Interlace scanning is a two-step process
of transmitting the odd lines of the scan and then going
back over the image, filling in the even lines to make a
complete image, Figure 23-37. Progressive scanning is
the capture and transmission of the entire image at one
time. Each line is placed on the screen progressively in
one sweep.
Frame rate is how often the image is updated on the
screen. Currently, three frame rates (in frames per sec-
ond) exist: 60, 30, and 24. Aspect ratio is the relationship
of the horizontal to vertical screen presentation measure-
ments. Aspect ratio standards can be either 4:3 or 16:9.
The 16:9 is a wide-screen aspect ratio similar to common
movie theaters. The 4:3 aspect ratio is a standard televi-
sion rectangle. The various factors of aspect ratio, frame
rates, and scanning method combine to form the 18 dif-
ferent screen standards. Figure 23-38 lists the 18 ATSC
digital TV compression formats.
HDTV has a vertical scanning rate equal to 720p
(progressive) and 1080i (interlaced) vertical lines. The
actual display may have a higher vertical scan rate than
the 1080i standard. This is especially important as the
size of the display area increases.
To compare the quality of analog television to
HDTV, you must convert scan lines to maximum number
of pixels. A pixel is the smallest unit of an image on a
graphic display. It can be thought of as a single dot in the
entire image.
Analog television approximates a screen composed
of 480 × 440 pixels, producing 211,200 total pixels.
HDTV approximates a screen composed of 1920 × 1080
pixels, producing 2,073,600 total pixels and by far a
greater detailed image than the analog system.
The Moving Picture Experts Group developed the
MPEG2 image compression standard to increase the
amount of video data transmitted in an HDTV system. By
compressing the broadcast video data, more information
could be broadcast in the same amount of bandwidth. The
MPEG2 compression technique can reduce the image
information by as much as 97 percent, but an average of
50 percent is typical. The compression technique is based
on the fact that the majority of the video images on a tel-
evision screen do not change from frame to frame. For
example, a news broadcast has a persistent image, such as
a background, with very little movement requiring new
data. Parts of the image that are persistent do not need to
Odd Rows
240 lines 30 × /sec
All lines scanned at once
480 lines 60 × /sec
Even Rows
240 lines 30 × /sec
A
B
Figure 23-37. Interlaced and progressive scanning.
A—Interlaced scanning captures and transmits the odd
lines first, and then the even lines. B—Progressive scan-
ning captures and transmits the whole image at once.

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Page 16Section 1 Fundamentals of Electricity and Electronics click to expand contents

Page 102Section 2 Basic Circuits click to expand contents

Page 124Section 3 Motors, Generators, and Power Distribution click to expand contents

Page 208Section 4 Advanced Electronic Circuits click to expand contents

Page 354Section 5 Electronic Communication and Data Systems click to expand contents

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