to study about computer monitors

7/30/2019 To Study About Computer Monitors

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Basic Hardware

To Study about Computer Monitors


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A Monitor or Display (also called Screen or visual display unit) is an electronic visual

display for computers. The monitor comprises the display device, circuitry and an enclosure.

The display device in modern monitors is typically a thin film transistor liquid crystal

display (TFT-LCD) thin panel, while older monitors use a cathode ray tube (CRT) about as

deep as the screen size.

Originally, computer monitors were used for data processing while television receivers were

used for entertainment. From the 1980s onwards, computers (and their monitors) have

been used for both data processing and entertainment, while televisions have implemented

some computer functionality. The common aspect ratio of televisions, and then computer

monitors, has also changed from 4:3 to 16:9 (and 16:10).

TECHNOLOGIES

Multiple technologies have been used for computer monitors. Until the 21st century

most used cathode ray tubes but they have largely been superseded by LCD monitors.

1. Cathode Ray Tube

The first computer monitors used cathode ray tubes (CRT). Until the early 1980s,

they were known as video display terminals and were physically attached to the computer

and keyboard. The monitors were monochrome, flickered and the image quality was

poor. In 1981, IBM introduced the Color Graphics Adapter, which could display four colors

with a resolution of 320 by 200 pixels. In 1984 IBM introduced the Enhanced Graphics

Adapter which was capable of producing 16 colors and had a resolution of 640 by 350.

CRT technology remained dominant in the PC monitor market into the new

millennium partly because it was cheaper to produce and offered viewing angles close to

180 degrees.
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2. Liquid crystal

There are multiple technologies that have been used to implement liquid crystal

displays (LCD). Throughout the 1990s, the primary use of LCD technology as computer

monitors was in laptops where the lower power consumption, lighter weight, and smaller

physical size of LCDs justified the higher price versus a CRT. Commonly, the same laptopwould be offered with an assortment of display options at increasing price points: (active or

passive) monochrome, passive color, or active matrix color (TFT). As volume and

manufacturing capability have improved, the monochrome and passive color technologies

were dropped from most product lines.

TFT-LCD is a variant of LCD which is now the dominant technology used for computer

monitors.

The first standalone LCD displays appeared in the mid-1990s selling for high prices.

As prices declined over a period of years they became more popular, and by 1997 were

competing with CRT monitors. Among the first desktop LCD computer monitors was the Eizo

L66 in the mid-1990s, the Apple Studio Display in 1998, and the Apple Cinema Display in

1999. In 2003, TFT-LCDs outsold CRTs for the first time, becoming the primary technology

used for computer monitors. The main advantages of LCDs over CRT displays are that LCDs

consume less power, take up much less space, and are considerably lighter. The now

common active matrix TFT-LCD technology also has less flickering than CRTs, which reduces

eye strain. On the other hand, CRT monitors have superior contrast, have superior response

time, are able to use multiple screen resolutions natively, and there is no discernible flicker

if the refresh rate is set to a sufficiently high value. LCD monitors have now very high

temporal accuracy and can be used for vision research.

3. Organic Light-Emitting Diode

Organic light-emitting diode (OLED) monitors provide higher contrast and better

viewing angles than LCDs, and are predicted to replace them. In 2011, a 25-inch OLED

monitor cost $7500, but the prices are expected to drop.
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MEASUREMENTS OF PERFORMANCE

The performance of a monitor is measured by the following parameters:

Luminance is measured in candelas per square meter (cd/m2 also called a Nit). Aspect ratio is the ratio of the horizontal length to the vertical length. Monitors usually have the

aspect ratio 4:3, 5:4, 16:10 or 16:9.

Viewable image size is usually measured diagonally, but the actual widths and heights are moreinformative since they are not affected by the aspect ratio in the same way. For CRTs, the

viewable size is typically 1 in (25 mm) smaller than the tube itself.

Display resolution is the number of distinct pixels in each dimension that can be displayed.Maximum resolution is limited by dot pitch.

Dot pitch is the distance between subpixels of the same color in millimeters. In general, thesmaller the dot pitch, the sharper the picture will appear.

Refresh rate is the number of times in a second that a display is illuminated. Maximum refreshrate is limited by response time.

Response time is the time a pixel in a monitor takes to go from active (white) to inactive (black)and back to active (white) again, measured in milliseconds. Lower numbers mean faster

transitions and therefore fewer visible image artifacts.

Contrast ratio is the ratio of the luminosity of the brightest color (white) to that of the darkestcolor (black) that the monitor is capable of producing.

Power consumption is measured in watts. Delta-E: Color accuracy is measured in delta-E; the lower the delta-E, the more accurate the

color representation. A delta-E of below 1 is imperceptible to the human eye. Delta-Es of 2 to 4

are considered good and require a sensitive eye to spot the difference.

Viewing angle is the maximum angle at which images on the monitor can be viewed, withoutexcessive degradation to the image. It is measured in degrees horizontally and vertically.
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SIZE

For any Rectangular section on a round tube, the diagonal measurements are also the diameter of the tube.

The area, height and width of displays with identical diagonal measurements vary dependent on aspect ratio.

On two-dimensional display devices such as computer monitors the display size or

viewable image size is the actual amount of screen space that is available to display

a picture, video or working space, without obstruction from the case or other aspects of the

unit's design. The main measurements for display devices are: width, height, total area and

the diagonal.
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The size of a display is usually by monitor manufacturers given by the diagonal, i.e.

the distance between two opposite screen corners. This method of measurement is

inherited from the method used for the first generation of CRT television, when picture

tubes with circular faces were in common use. Being circular, only their diameter was

needed to describe their size. Since these circular tubes were used to display rectangular

images, the diagonal measurement of the rectangle was equivalent to the diameter of the

tube's face. This method continued even when cathode ray tubes were manufactured as

rounded rectangles; it had the advantage of being a single number specifying the size, and

was not confusing when the aspect ratio was universally 4:3.

The estimation of the monitor size by the distance between opposite corners does

not take into account the display aspect ratio, so that for example a 16:9 21 in

(53 cm) widescreen display has less area, than a 21 in (53 cm) 4:3 screen. The 4:3 screen has

dimensions of 16.8 in 12.6 in (43 cm 32 cm) and area 211 sq in (1,360 cm2), while the

widescreen is 18.3 in 10.3 in (46 cm 26 cm), 188 sq in (1,210 cm2).

ASPECT RATIO

Until about 2003, most computer monitors had a 4:3 aspect ratio and some had 5:4.

Between 2003 and 2006, monitors with 16:9 and mostly 16:10 (8:5) aspect ratios became

commonly available, first in laptops and later also in standalone monitors. Reasons for this

transition was productive uses for such monitors, i.e. besides widescreen computer game

play and movie viewing, are the word processor display of two standard letter pages side by

side, as well as CAD displays of large-size drawings and CAD application menus at the same

time. In 2008 16:10 became the most common sold aspect ratio for LCD monitors and the

same year 16:10 was the mainstream standard for laptops and notebooks. In 2010 the

computer industry started to move over from 16:10 to 16:9.

In 2011 non-widescreen displays with 4:3 aspect ratios were only being

manufactured in small quantities. According to Samsung this was because the "Demand for

the old 'Square monitors' has decreased rapidly over the last couple of years," and "I predict

that by the end of 2011, production on all 4:3 or similar panels will be halted due to a lack of

demand."

RESOLUTION

The resolution for computer monitors has increased over time. From 320200 during

the early '80s, to 800600 during the late '90s. Since 2009, the most commonly sold

resolution for computer monitors are 19201080. Top-end consumer products are limited

to 25601600 at 30 inches. Apple introduced 28801800 with Retina MacBook Pro at

15 inches on June 12, 2012.
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CRTVS.LCD-THE PROS AND CONS OF EACH

Resolution & Viewing Quality - Resolution on a CRT is flexible and anewer model will provide you with viewing resolutions of up to 1600 by 1200 and

higher, whereas on an LCD the resolution is fixed within each monitor (called a

native resolution). The resolution on an LCD can be changed, but if you're running it

at a resolution other than its native resolution you will notice a drop in performance

or quality.

Both types of monitors (newer models) provide bright and vibrant color display.

However, LCDs cannot display the maximum color range that a CRT can. In terms of

image sharpness, when an LCD is running at its native resolution the picture quality

is perfectly sharp. On a CRT the sharpness of the picture can be blemished by soft

edges or a flawed focus.

A CRT monitor can be viewed from almost any angle, but with an LCD this is often a

problem. When you use an LCD, your view changes as you move different angles and

distances away from the monitor. At some odd angles, you may notice the picture

fade, and possibly look as if it will disappear from view.

Refresh Rate - Some users of a CRT may notice a bit of an annoying flicker,which is an inherent trait based on CRTs physical components. Today's graphics

cards, however, can provide a high refresh rate signal to the CRT to get rid of this

otherwise annoying problem. LCDs are flicker-free and as such the refresh rate isn't

an important issue with LCDs.

Dot Pitch - Dot pitch refers to the space between the pixels that make upthe images on your screen, and is measured in millimeters. The less space between

pixels, the better the image quality. On either type of monitor, smaller dot pitch is

better and you're going to want to look at something in the 0.26 mm dot pitch or

smaller range.

Screen (viewable) Size - Most people today tend to look at a 17-inchCRT or bigger monitor. When you purchase a 17-inch CRT monitor, you usually get

16.1 inches or a bit more of actual viewing area, depending on the brand andmanufacturer of a specific CRT. The difference between the "monitor size" and the

"view area" is due to the large bulky frame of a CRT. If you purchase a 17" LCD

monitor, you actually get a full 17" viewable area, or very close to a 17".

Physical Size - There is no denying that an LCD wins in terms ofits physical size and the space it needs. CRT monitors are big, bulky and heavy. They

are not a good choice if you're working with limited desk space, or need to move the

monitor around (for some odd reason) between computers. An LCD on the other

hand is small, compact and lightweight. LCDs are thin, take up far less space and are

easy to move around. An average 17-inch CRT monitor could be upwards of 40pounds, while a 17&-inch LCD would weigh in at around 15 pounds.
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Price - As an individual one-time purchase a LCDmonitors is going to be more expensive. Throughout a lifetime, however, LCDs are

cheaper as they are known to have a longer lifespan and also lower power

consumption. The costs of both technologies have come down over the past few

years, and LCDs are reaching a point where smaller monitors are within many

consumers' price range. You will pay more for a 17" LCD compared to a 17" CRT, but

since the CRT's actual viewing size is smaller, it does bring the question of price back

into proportion. Today, fewer CRT monitors are manufactured as the price on LCDs

lowers and they become mainstream.

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