Advanced Imaging


Advanced Imaging Magazine

Updated: January 12th, 2011 09:49 AM CDT

Better Outdoor Displays

Using optical index matching silicone gels improves viewing and ruggedness

By Bill Riegler and Michelle Velderrain
NuSil Technology LLC

Portable computing, military environments, and demanding outdoor activities like fire rescue require a reliable and accurate display.

Most commercial, off-the-shelf displays are not produced for direct viewing outdoors. The bright ambient light outdoors can cause high reflection losses and subsequently “display washout.” Companies can increase display brightness, however this typically results in added power consumption and poor aspect ratios.

An alternative and growing trend is use of optical index matching silicone gels to reduce reflection losses and also aid in durability. Commercial displays typically have the display protected by a coverglass with a small air gap between the display and the coverglass. This gap leads to reflection loss as much as 8.5 percent, dependent on the difference of refractive indices between the surfaces. This reflection loss can be decreased by filling the gap with an optical index matching silicone gel, thus greatly increasing viewing outdoors in bright ambient light.

These optical index matching silicone gels are especially designed for protection of sensitive photonics assemblies. The encapsulation materials help improve impact resistance and protect the assembly from such things as dust and mechanical and thermal shock.

Optical silicone gels also are transparent and their softness easily allows the LCD panel to be disassembled for reworking.

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