Acer S191HQL Service Manual page 15

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1.4.4 Defects:
1.4.4 Defects:
1.4.4.1 Defect T erminology:
Dark Spots / Lines: Spots or lines that appear dark in the display patterns and are usually the result of
contamination. Defects do not vary in size or intensity (contrast) when contrast voltage is varied. Contrast
variation can be achieved through the use of varying gray shade patterns.
Bright Spots / Lines: Spots or lines that appears light in the display patterns. Defects do not vary in size or
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:
Definition of White Variation (δW):
Surface luminance is the luminance value at center 1 point(1) across the LCD surface 50cm from the surface
with all pixels displaying white.For more information see FIG 8
The variation in surface luminance , 
For more information see Figure 8.
WHITE
Minimum (P1,P2 .....P9)

= --------------------------------------------- *100
WHITE
Maximum (P1,P2 .....P9)
is defined as