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With
VarTech's proprietary optical stack, controlling reflected
light significantly improves the optical performance of an LCD display
in any ambient lighting condition. To view an LCD monitor in high
ambient light environments and/or direct sunlight one must consider
two important factors "luminance" and "illumination". The luminance of an LCD display is its brightness. Brightness is
traditionally referred to as a "nit" (Candela per meter/2), a unit of measure, which is the amount of light energy
coming out of the display. Illumination is the amount of ambient
light shining onto a display. The readability of a display is dependant
on the amount of light that is being reflected off the display.
Light has
the ability to travel through a variety of transparent materials;
such as air, glass, plastic, and even water. The material's ability
to transmit light is measured by its indices of refraction. As
light transfers from one material to another, such as air to glass,
the differences of the index of refraction will cause reflection.
In the case of an air-to-glass interface, the reflection will
be slightly less than 5% of the ambient light. All surfaces that
have an index "mismatch" will reflect cumulatively.
In the case of a standard glass or plastic protective overlay
window, typically used in front of the delicate LCD, there are
three surfaces with an index mismatch which will create a total
reflection of nearly 15% of the ambient light. If the total reflection
(in nits) is close to the displays brightness, the contrast of
the display will be reduced to the point where the display's readability
is reduced to unacceptable levels.
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The two images below
are representative of the reflective loss experienced by an LCD without
a VBOND layer between the LCD enhancement and the display glass of the
LCD.
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Any VarTech monitor
integrated with our VBOND process is equipped with a UV protected solid,
transparent bond. This procedure permanently bonds the front protective
glass overlay or touch screen directly to the frontal face of the display.
VarTech's unique optical bond eliminates reflection from
the two internal layers and utilizes an adhesive that matches the index
of refraction of the flat panel and the overlay. As well, the outer
surface of the protective window is chemically treated with anti-reflecting
coatings which matches the front surface of the glass with the index
of refraction of air. This combination reduces the total reflection
of the display and front cover glass to less than 2% of the ambient
light. A reduction of reflection of this level, all but eliminates reflective
loss in most ambient lighting conditions. With reductions of this level,
displays with 250 to 450 nits of brightness (cd/m2), traditionally not
viewable in direct sunlight, will now be readable in very high ambient
brightness or indirect lighting conditions. This method also removes
all air gaps, therefore reducing the number of internal reflecting surfaces
which can lead to significant degradation of the LCD's
optical performance.
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The Image
to the right is representative of the IMPROVED reflective loss
experienced when a VBOND is applied between the face of the LCD
and the LCD Enhancement.
VarTech's
VBOND process has many other benefits as well. By providing this
durable adhesion between the flat panel and the overlay we greatly
improve the displays' ability to resist shock, vibration
and moisture. Additionally, with the eliminated air-gap we (1)
prevent heat build-up from a "greenhouse" effect, (2)
prevent fogging from moisture, and (3) eliminate any contamination
from dirt or obtrusive particles.
Additionally,
since VarTech supports a number of industrial, marine and military
markets there exists a number of add-on choices which can be integrated
into the VBOND process to address our customer¡¦s
specific environmental needs. These features include:
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Contrast Enhancement
filters
Vandal Shields chemically strengthen the display glass
EMI Filters enable LCD compliance with FCC and MIL-STD 461
Touch Screens
Transparent thermal heaters to extend LCD operational temperatures
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