An increased number of LCD-based products are being utilized in high ambient light conditions, typically outdoors in direct sunlight. The need has become significantly greater for them to not only be able to withstand extensive operational temperatures, sometimes down to -40°C, but as well be adequately readable when exposed to extreme optical conditions such as direct and/or indirect sunlight, glare and reflection.
Most “off-the-shelf” LCD flat panels are not properly equipped to handle most rigors of outdoor conditions. The traditional approach has been the integration of additional CCFL, cold cathode fluorescent lamps, to increase luminance levels. This method, while producing the desired readability effect, has five significant drawbacks. First, the use of added CCFL increases the amount of heat needed to be dissipated away from the monitor. This is typically accomplished through the use of an extensive and costly thermal management system. Second, added backlights will increase the amount of power required to sufficiently operate the display system. For example, a non-actively enhanced display might use 30 watts of power, while an actively enhanced approach using added CCFL might increase power consumption up to 85 watts. Third, driving the enhanced backlights to optimal potential will significantly reduce the expected life of the backlights. This could result in costly repairs when backlights begin to fail.
Fourth, the use of enhanced wattage CCLF backlights, as we mentioned, is used to increase the luminance of an LCD. Imagine, as an example, that a typical LCD monitor has a white luminance of 200 nits and a contrast ratio of 300:1 (black luminance of 0.66 nits) and the newly integrated backlights then enhances by ten times the white luminance to 2,000 nits. A display’s brightness, typically referred to as a Nit (Candela per meter/2) is the amount of light energy coming out of the display. While the display is unarguably brighter, the increased brightness will not have much effect in direct sunlight if the “black luminance” is correspondingly increased from 0.66 nits to 6.6 nits (contrast ratio of 300:1). Finally, added CCFL backlights significantly increases the amount of electro magnetic interference (EMI). This can be an important issue if the monitor will be positioned near other mission critical electronic devices.
Another approach is the use of passive enhancement technology such as transflective films. A transflective LCD is by definition a compromise. Throughout outdoors environments, some of the ambient light is reflected by the screen. As the ambient light gets brighter, the screen is supposed to look better and in reality it will only look its best in direct sunlight and of course this isn’t at all feasible in real world life. Indoors, however, only a fraction of the backlight is transmitted through the LCD, so the screen tends to look dim and low-contrast, with muted colors. Although transflective films are designed to reflect ambient light back out of the LCD display to augment its performance in direct sunlight, transflective panels have insufficient transmissive luminance (typically ~200 nits) to be considered usable in diffuse lighting conditions where direct sunlight is not available (e.g., cloudy or rainy days).
VarTech Systems has developed a ground-breaking LED backlight technology. This new technology creates an amazingly bright LCD display without increased heat from higher wattage CCFL integration. LED backlight technology when coupled with a liquid crystal display (LCD) provides the best of both worlds – a high brightness LCD monitor with low power consumption.
VarTech’s LED backlighting was developed for displays requiring a luminance level of at least 800 nits as required for outside viewing. When compared to the practice of adding higher wattage backlights to achieve a high brightness LCD (CCFL), LED backlight technology increases the reliability of the high bright monitor and extends the lifetime of the display system. This new technology by VarTech creates a sunlight readable monitor with inherit protections against environmental factors such as shock, vibration and frigid temperatures. LED backlighting technology enables all these benefits while maintaining reasonable thermal levels of the LCD.
VarTech has coupled this technology with the usage of harsh duty, very wide operational temperature LCD cells, typically with a -50C to +100C clearing range. Additionally, each panel is engineered with VarTech’s proprietary Enhanced Light Transmission Technology (ELTT) and Optical Bonding (VBOND), a UV protected solid, transparent bond. This procedure permanently bonds the front protective glass overlay or touch screen directly to the frontal face of the display. VarTech’s unique optical bond eliminates reflection from the two internal layers and utilizes an adhesive that matches the index of refraction of the flat panel and the overlay. As well, the outer surface of the protective window is chemically treated with anti-reflecting coatings which matches the front surface of the glass with the index of refraction of air. This combination reduces the total reflection of the display and front cover glass to less than 2% of the ambient light. A reduction of reflection of this level, all but eliminates reflective loss in most ambient lighting conditions. With reductions of this level, displays with 250 to 450 nits of brightness (cd/m2), traditionally not viewable in direct sunlight, will now be readable in very high ambient brightness or indirect lighting conditions. This method also removes all air gaps, therefore reducing the number of internal reflecting surfaces which can lead to significant degradation of the LCD’s optical performance. For more information regarding our VBOND process, please click here.
Currently VarTech’s new LED backlight technology has beeen successfully implemented into our new All-Weather series products and can achieve complete sunlight readability luminance levels ranging from approximately 800 to 1500 nits at low power consumption levels. With VarTech’s new LED high bright technology, a 15” 1000 nit LCD will consume approximately 24W of power compared to our equivalent 15” actively enhanced CCFL solution which consumes 65W. Additionally, VarTech’s LED backlighting systems do not require heaters as needed by CCFL solutions for use within extreme low temperature ranges. This is beneficial in many outdoor applications that operate in frigid temperatures and immediate LCD response time operation is critical. The LCD can immediately be turned to full brightness without any lag time which can typically be caused by the use of integrated heaters.
VarTech’s LED backlight enhancement offers a number of key benefits over traditional CCFL enhanced solutions: