Services / LCD Optical
Improved contrast. Faster perception. Higher performance. Improved Sunlight
The LCD outdoor viewability
The traditional method of making an LCD viewable outdoors
(in bright ambient light) is to increase the intensity of the backlight to approximately 750 to 1000 cd/m2 (nits).
This attempts to make the viewable light greater than the reflected ambient light by shifting the display viewing
to a higher luminance level. There are a number of problems with this approach if it’s the only action taken.
Increasing the backlight brightness raises both the black luminance and the white luminance, which actually reduces
the contrast ratio (all other things unchanged). Lower contrast makes the display harder to read. The real problem
with LCD outdoor viewability is contrast, not brightness. Contrast is the ratio of the white level to the black
level. Or, said another way, a display’s contrast ratio is the difference in light intensity between the brightest
white pixel and the darkest black pixel. In this situation we’re talking about “extrinsic” contrast, meaning a
reading taken from a distance that accounts for ambient light and reflections. (The contrast ratio in a display’s
specifications sheet is “intrinsic” contrast, measured at the surface of the screen in a dark room.) Increasing the
extrinsic contrast ratio improves the outdoor viewability. Some rule-of-thumb values for extrinsic contrast are
shown in Table 1 below.
The objective of outdoor-viewability enhancement is to increase
somewhat the LCD’s luminance level as well as its contrast ratio by reducing the amount of ambient light reflected
by the LCD and anything on top of it (such as a touch screen). Light is reflected from any surface in the
optical path where there’s a change in the index of refraction. The greater the difference, the more light is
reflected from the surface. Air has an index of refraction of 1.0, glass has an index of around 1.5 and plastic
film has an index of around 1.6. This difference between 1.0 and 1.5 or 1.6 results in an average of 4.5% reflected
light per surface (actually it varies from 4% to 5% depending on the difference in refractive index, the wavelength
and other factors).
Figure 1 below diagrams the reflected light from an LCD with a
standard resistive touch screen; Table 2 below shows four different enhancement cases.
Increase TFT AMLCD readability-at-a glance capability by specifying an
optically bonded TFT display from AbraxSys. Combine LED backlight enhancement, optical coatings, or
touchscreens to meet your human interface requirements. AbraxSys' optical bonding facility provides proven
quality systems, extensive in-house optical test verification capabilities, a certified clean room and other
environmental controls. Standard LCD displays are fine for most
indoor applications, but they are challenged in outdoor, rugged or environmentally extreme applications. For
these applications, commercial displays are all but useless. The choices are either make the display washout
less, or make the display brighter; and in some cases, both options. The OEM display manufacturers are not
focused on these extreme markets and applications. This is where AbraxSys helps the display customer.
AbraxSys' line of high performance optically bonded displays are ideal for outdoor or rugged environments
where top performance is
Improves contrast by eliminating mismatched reflective layers
• Improves readability without increasing backlight wattage
• Increased Sunlight Readability by up
Increased Shock and Vibration Durability
• Strengthens the overall integrity of the
scratch resistance up to 300%
• Enables resistance to extreme
• Eliminates the "Greenhouse" effect and going
Optical coatings reduce specular and diffuse reflections
• Less power required for battery powered devices while attaining
• Certified clean room and environmental controls
• Fast, responsive manufacturing in U.S.A.
AbraxSys optical bonding gives the
competitive advantage of eliminating the air-gap between the glass surface and display. When comparing an
optically bonded cover-plate with a traditional cover-plate, the benefits become very clear. Please see the
have been conducted to show the increased benefits of optically bonded panels. Scratch resistance testing was
conducted using AbraxSys' special adhesive. Tests proved that scratch resistance was increased by 300% over
non-bonded display surfaces.
testing proves the increased durability AbraxSys Optical Bonding provides. See the results
Contact an AbraxSys associate today to learn more about our LCD
Optical Bonding capabilities.