Acer H236HL Service Manual page 15

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intensity (contrast) when contrast voltage is varied. Contrast variation can be achieved through the use of
varying gray shade patterns.
Polarizer Scratch: When the unit lights, lines appear light (white) with display patterns dark and do not vary in
size. Physical damage to the polarizer does not damage the glass.
Polarizer Dent: When the unit lights, spots appear light (white) with display patterns dark and do not vary in size.
Physical damage to the polarizer does not damage the glass.
Rubbing Line: Horizontal or diagonal lines that appear gray with the display patterns dark and may have
resulted from an "out of control" rubbing process on the polyimide or "waves" on the BEFs or prism sheets .
Newton Ring: The "rainbow" effect caused by non-uniform cell thickness.
Mottling: When the unit lights, variation / non - uniformity (splotch) appears light (white) with the display and
might vary in size.
Dim Line: When the unit lights, line(s) in the minor (vertical) or major (horizontal) axis appear dim, but not
completely on or off.
Cross Lines Off: When the unit lights , lines in both the minor and major axis do not appear.
Bright/Dark Dot: A sub - pixel (R, G, B dot) stuck off / on (electrical).
1.5 Optical Characteristics:
1.5.1 Brightness uniformity:
The brightness uniformity has to be better than 75% and is calculated according to
to the following formula:
With Y1 to Y9 as the brightness values with all pixels white at the 9 measurement
Positions. Contrast and Brightness set to Max.
1.5.2 Contrast ratio (CR):
1.5.2.1 General CR:
The values specified are at an approximate distance 50cm from the LCD surface at a viewing angle of  and 
equal to 0 °.
Contrast ratio(CR) is defined mathematically as :It is measured at center point(1)
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