Frequently
Asked Questions
About LCD Displays
1. What is
a Pixel?
2. What is Dot Pitch?
3. How does Touch Screen Technology
work?
4. What is a NIT?
5. How do I know how many NIT's
I require for my application?
6. What is considered a true
sunlight readable or outdoor readable LCD?
7. What is Luminance?
8. What is Contrast Ratio (CR)?
9. What is a Viewing Angle
and why does it matter?
10. Are there thermal management
issues with high bright LCD's?
11. Display Modes: An overview
of screen resolutions
12. A clear understanding
of today's video signals
13. How do your FlashView Ad Players work?
14. How do I load content onto FlashView ad players?
15. What's the difference between FlashView Touch and push buttons?
16. How do I add content for buttons or touch segments?
17. I don't see exactly what I need. Do you provide customization?
18. I only need a few screens. Do you require a minimum order size?
19. How long will it take to get my order?
20. What is the warranty on your products?
1.
What is a Pixel?
Often referred to as dot, as in "dots
per inch", "Pixel" is short
for picture elements, which make up an image,
similar to grains in a photograph or dots
in a half-tone. Each pixel can represent a
number of different shades or colors, depending
on how much storage space is allocated for
it. Pixels per inch (ppi) are sometimes the
preferred term, as it more accurately describes
the digital image. The actual physical size
of a pixel depends on the resolution set for
the display screen. If your display is set
for the maximum resolution, the physical size
of the pixel is equal to the dot pitch of
the display. If your display is set to something
less than the maximum resolution, then a pixel
will be larger than the actual size of the
screen dot, i.e. a pixel will use more than
one dot.
2.
What is Dot Pitch?
The dot pitch, also known as the pixel pitch
is the distance between a red (or green or
blue) dot and the closest red (or green or
blue) dot on a color monitor or LCD screen.
On desktop monitors, the dot pitch is typically
from 0.25 to 0.31mm, while large presentation
monitors may go up to 1.0mm. On LCD monitors,
the dot pitch is typically from 0.16 to 0.29mm.
In general, the smaller the dot pitch, the
crisper the image. A 0.28 dot pitch means
dots are 28/100ths of a millimeter apart.
A dot pitch of 0.31 or less provides a sharp
image, especially on text.
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3.
How does touchscreen technology work?
Selecting a Touch Screen Technology
The three most common touch screen technologies
include resistive, capacitive and SAW (surface
acoustic wave). Each technology offers its
own unique advantages and disadvantages as
described below. Resistive and capacitive
touch screen technologies are the most popular
for industrial applications. They are both
very reliable. If the application requires
that operators can wear gloves when using
the touch screen, then resistive is the recommended
technology as capacitive doesn't support gloves.
If operation with gloves is not required,
then capacitive technology is the preferred
choice due to better optical characteristics.
Resistive
A resistive touch screen typically uses a
display overlay consisting of layers, each
with a conductive coating on the inner surface.
The conductive inner layers are separated
by special separator dots, evenly distributed
across the active area. Pressure causes internal
electrical contact at the point of touch,
supplying the electronic interface (touch
screen controller) with vertical and horizontal
analog voltages for digitization. For CRT
applications, resistive touch screens are
generally spherical (curved) to match the
CRT and minimize parallax. The nature of the
material used for curved (spherical) applications
limits light throughput such that two options
are offered: Polished (clear) or antiglare.
The polished choice offers clarity but includes
some glare. The antiglare choice will minimize
glare, but will also slightly diffuse the
light throughput (image). Either choice will
demonstrate either more glare (polished) or
more light diffusion (antiglare) than associated
with typical non-touch screen displays. Despite
the tradeoffs, the resistive touch screen
technology remains a popular choice, often
because it can be operated while wearing gloves
(unlike capacitive technology). Note that
resistive touch screen materials used for
flat panel touch screens are different and
demonstrate much better optical clarity (even
with antiglare). The resistive technology
is far more common for flat panel applications.
Capacitive
A capacitive touch screen includes an overlay
made of glass with a coating of capacitive
(charge storing) material deposited electrically
over its surface. Oscillator circuits located
at corners of the glass overlay will each
measure the capacitance of a person touching
the overlay. Each oscillator will vary in
frequency according to where a person touches
the overlay. A touch screen controller measures
the frequency changes to determine the X and
Y coordinates of the touch. Because the capacitive
coating is even harder than the glass it is
applied to, it is very resistant to scratches
from (SIC) sharp objects. It can even resist
damage from sparks. A capacitive touch screen
cannot be activated while wearing most types
of gloves (non-conductive).
SAW (Surface Acoustic Wave)
A SAW touch screen uses a solid glass display
overlay for the touch sensor. Two surface
acoustic (sound) waves, inaudible to the human
ear, are transmitted across the surface of
the glass sensor, one for vertical detection
and one for horizontal detection. Each wave
is spread across the screen by bouncing off
reflector arrays along the edges of the overlay.
Two receivers detect the waves, one for each
axis. Since the velocity of the acoustic wave
through glass is known and the size of the
overlay is fixed, the arrival time of the
waves at the respective receivers is known.
When the user touches the glass surface, the
water content of the user's finger absorbs
some of the energy of the acoustic wave, weakening
it. The controller circuitry measures the
time at which the received amplitude dips
to determine the X and Y coordinates of the
touch location. In addition to the X and Y
coordinates, SAW technology can also provide
Z axis (depth) information. The harder the
user presses against the screen, the more
energy the finger will absorb, and the greater
will be the dip in signal strength. The signal
strength is then measured by the controller
to provide the Z axis information. Today,
few software applications are designed to
make use of this feature.
Touch Screen Controllers
Most manufacturers offer two controller configurations--ISA
Bus and Serial-RS232. ISA bus controllers
are contained on a standard printed circuit
plug-in board and can only be used on ISA
or EISA PC. Depending on the manufacturer
they may be interrupt driven, polled or be
configured as another serial port. Serial
controllers are contained on a small printed
circuit board and are usually mounted in the
video monitor cabinet. They are then cabled
to a standard RS232 serial port on the host
computer.
Software
Most touch screen manufacturers offer some
level of software support which include mouse
emulators, software drivers, screen generators
and development tools for Windows, OS/2, Macintosh
and DOS. Most of the supervisory control and
data acquisition (SCADA) software packages
now available contain support for one or more
touch technologies.
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4.
What is a NIT?
A NIT is a measurement of light in candelas
per meter square (Cd/m2). For an LCD monitor
it is brightness out of the front panel of
the display. A NIT is a good basic reference
when comparing brightness from monitor to
monitor. Most desktop LCD's or Notebook LCD's
have a brightness of 200 to 250 Nits. These
standard LCD's are not readable in direct
or even indirect sunlight as they become washed
out.
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5.
How do I know how many NIT's I require for
my application?
Applications will vary depending on the location
of the LCD and how much ambient light is available
that could cause the display to become washed
out or unreadable. As a rule of thumb; notebooks
and desktop LCD's which are generally used
in office light conditions are in the 200-250
nit range. For indoor use with uncontrolled
or indirect sunlight it is recommended that
a display of 500 - 900 nits be used. If the
application is outdoors or in direct sunlight
then at least 1000 nits and up should be considered.
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6.
What is considered a true sunlight readable
or outdoor readable LCD?
First, the display screen on a sunlight readable/outdoor
readable LCD should be bright enough so that
the display is visible in direct or strong
sunlight. Second, the display contrast ratio
must be maintained at 5 to 1 or higher.
Although a display with less than 500 nits
screen brightness and a mere 2 to 1 contrast
ratio can be read in outdoor environments,
the quality of the display will be dreadfully
poor and not get the desired information across
effectively. A true sunlight readable display
is normally considered to be an LCD with at
least 1000 nits of screen brightness and a
contrast ratio greater than 5 to 1. In outdoor
environments under the shade, such a display
can provide an excellent image quality.
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7.
What is Luminance?
Luminance is the term which specifies the
visual brightness of an object. It is another
term for NIT. Like NIT, it is measured in
candelas per square meter (Cd/m2) or nits.
Luminance is an influential factor of perceived
picture quality in an LCD. The importance
of luminance is enhanced by the fact that
humans will react more positively to a brightly
illuminated screen. In indoor environments,
a standard active-matrix LCD with a screen
luminance of around 250 nits will look good.
In the same scenario an LCD with a luminance
of 1,000 nits or more will look utterly captivating.
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8.
What is Contrast Ratio (CR)?
Contrast ratio (CR) is the ratio of luminance
between the brightest "white" and
the darkest "black" that can be
produced on a display. CR is another influence
of perceived picture quality. If a picture
has high CR, you will consider it to be sharper
and crisper than a picture with lower CR.
For example, a typical newspaper picture has
a CR of about 5 to 7, whereas a high quality
magazine picture has a CR that is greater
than 15. Therefore, the magazine picture will
look better even if the resolution is the
same as that of the newspaper picture.
A typical AMLCD exhibits a CR of approximately
300 to 700 when measured in a dark room. The
CR on the same unit measured under ambient
illumination is drastically lowered due to
surface reflection (glare). For example, a
standard 200 nit LCD measured in a dark room
has a 300 CR, but will have less than a 2.0
CR under intense direct sunlight. This is
due to the fact that surface glare increases
the luminance by over 200 nits both on the
"white" and the "black"
that are produced on the display screen. The
result is the luminance of the white is slightly
over 400 nits, and the luminance of the black
is over 200 nits. The CR ratio then becomes
less than 2 and the picture quality is drastically
reduce and not acceptable.
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9.
What is a Viewing Angle and why does it matter?
The viewing angle is the angle at which the
image quality of an LCD degrades and becomes
unacceptable for the intended application.
Viewing angles are usually quoted in horizontal
and vertical degrees with importance dependent
on the specific application. As the observer
physically moves to the sides of the LCD,
the images will degrade in three ways. First,
the luminance drops. Second, the contrast
ratio usually drops off at large angles. Third,
the colors may shift. Most modern LCD's have
acceptable viewing angles even for viewing
from the sides.
For LCD's used in outdoor applications, defining
the viewing angle based on CR alone is not
adequate. Under very bright ambient light
conditions the display is hardly visible when
the screen luminance drops below 200 nits.
Therefore, the viewing angles are defined
based on both the CR and the Luminance.
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10.
Are there thermal management issues with high
bright LCD's?
Yes -any high brightness backlight system
will consume a significant amount of power,
thereby increasing the LCD temperature. The
brighter the backlight, the greater the thermal
issue. As well, if the LCD is used under direct
sunlight additional heat will be generated
as a result of sunlight exposure. Temperature
issues have been handled through proper thermal
management design incorporating passive and
active cooling methods. This is extremely
important in maintaining overall reliability
and long-term operation.
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11.
Display Modes: An overview of screen resolutions
The term display mode or the more commonly
used screen resolution refers to the characteristics
of a computer display. Screen real estate
is usually measured in pixels. In particular,
the maximum number of colors and the image
resolution in pixels measured horizontally
and vertically. There are several display
modes that are used today from a small amount
of data up to extremely large amounts that
are jam-packed into the display area.
A Brief
History
The earliest displays for personal computers
were monochrome monitors that were used in
text-based computer systems in the 1970s.
In 1981, IBM introduced the Color Graphics
Adapter (CGA). This display system was capable
of rendering four colors, and had a maximum
resolution of 320 pixels horizontally by 200
pixels vertically. While CGA was ok for simple
tasks it certainly could not display adequate
graphics.
In
1984, IBM introduced the Enhanced Graphics
Adapter (EGA). It allowed up to 16
different colors and offered resolution of
up to 640 x 350. This improved the appearance
over earlier displays, and made it possible
to read text easily. Nevertheless, EGA did
not offer sufficient image resolution for
use in graphic design either.
In 1987, IBM introduced the Video Graphics
Array (VGA) display system. This has
become the accepted minimum standard for PC.
The VGA standard is still used today in some
applications.
In 1990, IBM introduced the Extended Graphics
Array (XGA) display as a successor
to its 8514/A display. A later version, XGA-2
offered 800 x 600 pixel resolution in true
color (16 million colors) and 1024 x 768 resolution
in 65,536 colors. These two image resolution
levels are perhaps the most popular in use
even today.
Recently, new display technology has given
the ability to display vast amounts of pixels
into a given area. The table shows display
modes and the resolution levels (in pixels
horizontally by pixels vertically) that are
commonly found today.
The 4 x 3 settings are most common with standard
PC type monitors whether they are LCD or CRT's.
In recent times larger displays have become
available in the letterbox or landscape style.
These are typically used for multimedia and
home theatre applications. The letterbox style
displays usually operate efficiently at a
16:9 aspect ratio. This therefore changes
the overall resolution of the display as noted
in the table.
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12.
A clear understanding of today's video signals
Understanding
the differences between Composite Video, S-Video
and Component Video
With the growth of home theatre, video cameras
and the consumer electronics market many of
today's computers and peripherals (especially
LCDs) have multiple video input options available
to them. Here is a clearer picture of what
these signals represent.
Composite
video, also referred to as baseband or
RCA video, is the most common of all video
signals. A composite video signal consists
of an analog waveform that conveys the image
data in a conventional National Television
Standards Committee (NTSC) television signal.
Composite video contains chrominance (hue
and saturation) and luminance (brightness)
information, along with synchronization and
blanking pulses, all together in a single
signal.
Composite video is the standard that connects
almost all consumer video equipment through
a phono-jack, also known as an RCA connector.
In composite video, interference between the
chrominance and luminance information is inevitable
resulting in poor quality video when signals
are weak. The cable has 3 jacks: yellow, white,
and red. One jack sends the audio (left),
the second the stereo (right), and the third
the video, respectively. The picture quality
is decent but pales in comparison to S-Video.
S-Video
(Super-Video, Super-VHS) and sometimes referred
to as Y/C Video was introduced in the 1980s
and solved some of the problems that were
inherent with composite video. S-Video provides
better color separation and a much cleaner
signal by keeping the transmitted luminance
and chrominance video signals separated. Today,
S-Video signals are generally connected using
4-pin mini-DIN connectors using a 75 ohm termination
impedance. S-Video provides for a high quality
method of delivering a clean crisp video signal.
Component
video improves the picture quality even
more than S-Video. Component refers to video
transmitted as three separate signals (subsignals
if you prefer) to represent all colors. The
first component video was RGB since the three
signals represented pure red, pure green,
and pure blue content respectively. Today,
most video experts use the term "component
video" as short for "analog component
video" consisting of the three signals
Y (luminance), Pr or R-Y, and Pb or B-Y. For
NTSC or PAL (interlaced video formats) the
Y signal is the same as that used to construct
composite video or that found in S-Video.
The most common connection from DVD players
is three RCA-type jacks.
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13.
How do your FlashView ad players work?
Our FlashView ad players have an integrated media players that run off of flash memory cards. No PC, DVD player, or network is needed. Simply load your content, images and/or videos, onto a flash memroy card and plug it in. There is no special software required so they are simple to setup and use. You can display slideshows or videos, and many of our FlashView ad players have interactive options as well.
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14.
How do I load content onto FlashView ad players?
Videos, images, and videos with audio can be added simply by dropping the files onto a flash memory card. No special management software is required. Just be sure to format the files according to the ad player's rrequirements. For example, the FlashView 1000 and 2000 series require maximum video resolution of 720x405, AVI, DivX, or Mpeg format, and a video frame rate of 30 frames per second. Be sure to properly convert your original videos to these specs to avoid playback issues. When in doubt, check the user's guide or call us for help.
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15.
What's the difference between FlashView Touch and push buttons?
Our segmented touch screen is fully interactive and users can touch a programmed screen interface to activate content. The segmented touch membrane is very affordable compared to resistive screens and gives the same impression of quality. You specify the number of touch segments you want, from 2 to 8 segments. Aside from the touch interface, the ad players work exactly the same.
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16.
How do I add content for buttons or touch segments?
Simply add folders on the flash card and name them “1”, “2”, “3”, etc. These folders correspond to the buttons or the touch segments. Drop your content into the appropriate folder. When a customer pushes a button or touches the screen, the Ad Player will open the appropriate folder and play the content. The ad player will then return to the attraction video or default menu screen.
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17.
I don't see exactly what I need. Do you provide customization?
Yes! We offer a wide array of customization for all our prodects, far too much to detail on our website. If you don;t see exactly what you want, call and talk to one of our sales engineers. We are happy to help with any request and can usually provide exactly what you are looking for.
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18.
I only need a few screens. Do you require a minimum order size?
There are no minimums required to purchase from us. Whether you want 1, 100, or thousands, we are happy to help.
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19.
How long will it take to get my order?
We keep many of our most popular items in stock with standard configurations, so many items, like FlashView ad players, can ship same day. Most of our clients require customization or large quantities, so we build those products to order. Since our manufacturing plant is in China, it usually takes about 4 weeks to buils, ship, and recieve products to our warehouse.
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20.
What is the warranty on your products?
We back all out industrail grade products with a 1 year warranty against manufacturing defects. All warranty claims are handles by Industrial Image, so please contact us if you have any questions.
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