2
Contrast Enhancement
The objective of contrast enhancement is to provide
good display readability in the end use ambient light.
The concept is to employ both luminance and chromi-
nance contrast techniques to enhance the readability.
This is accom plished by having the OFF dots blend into
the display background and the ON dots stand out vividly
against this same background. Therefore, these display
devices are assembled with a gray package and matching
encapsulating epoxy in the dots.
Contrast enhancement may be achieved by using one of
the following suggested lters:
Standard Red and AlGaAs Red (HDSP-5300/H150)
Panelgraphic RUBY RED 60
SGL-Homalite H100-1605 RED
3M Louvered Filter R6610 RED or N0210 GRAY
HER (HDSP-5500)
Panelgraphic SCARLET RED 60
SGL-Homalite H100-1670 RED or H100-1250 GRAY
3M Louvered Filter R6610 RED or N0210 GRAY
Yellow (HDSP-5700)
Panelgraphic YELLOW 27 or GRAY 10
SGL-Homalite H100-1720 AMBER or H100-1250 GRAY
3M Louvered Filter A5910 AMBER or N0210 GRAY
Green (HDSP-5600)
Panelgraphic GREEN 48
SGL-Homalite H100-1440 GREEN or H100-1250 GRAY
3M Louvered Filter YG6610 RED or N0210 GRAY
For further information on contrast enhancement please
see Application Note 1015.
Mechanical
Specially developed plastics are used to optimize the
displays optical performance. These plastics restrict the
solvents that may be used for cleaning. Only mixtures of
Freon (F113) and alcohol should be used for vapor clean-
ing processes. Total immersion time in the vapors is two
minutes. Some suggested mixtures are Freon TE, Arklone
A or K, or Genesolv DI-15 or DE-15. A 60°C (140°F) water
cleaning process may also be used. This process includes
a neutralizer rinse (3% ammonia solution or equivalent),
a surfactant rinse (1% detergent solution or equivalent),
a water rinse, and a thorough air dry. Room temperature
cleaning may be done with Freon T-E35 or T-P35, Ethanol,
Isopropanol, or water with a mild detergent.
Cleaning agents from the ketone family (acetone, methyl
ethyl ketone, etc.) and from the chlorinated hydrocarbon
family (methylene chloride, trichloro ethylene, carbon tet-
rachloride, etc.) are not recommended for cleaning LED
parts. All of these various solvents attack or dissolve the
encapsulating epoxies used to form the package of plastic
LED parts.
