Usability in bright environments is one of the critical characteristics of the display intended for use in industrial environments. Many industrial LCDs are designed to be installed outdoors or in brightly lit facilities. When choosing the best solution for your application, it is important first to dig into each possibility, and then decide which one is the most suitable for your particular application.

Main Factors Affecting Outdoor Readability

Have you ever thought about why you cannot see the display in the sunlight? We have listed some major factors that affect your display's readability and corresponding solutions to solve potential problems. One of the major problems in outdoor usage is the reflection of light that can be specular or diffuse depending on the nature of the interface. There are several panel enhancement methods that allow increasing screen usability in sunlight: transflective screen, apply dimming, use AR/AG glass, light sensor or optical bonding.

Technologies to Optimize Screen Usability

Manufacturers use various techniques to fine-tune the LCD screen for such demanding applications. The right combination of applied techniques is the key to success. Let’s take a closer look at each method.

• Transflective LCD technology – This method can be applied to certain selected regular TFT LCDs. With the imposed reflective function, the modified LCD can reflect the ambient light passing the LCD cell and utilizing the reflected light beams as its illumination. The stronger the ambient light is, the brighter the LCD will appear. As a result, the modified LCD is viewable under lighting conditions, including direct sunlight.
• Hyper dimming – Under some specific user conditions, it will be necessary for the monitor to be adjusted to a lower brightness level than normal. The hyper dimming technology provides the wider brightness adjustment level combined with excellent appearance to meet the dim-to-black requirement. The high sensitivity of fully adjustable backlight control makes the product ideal for day and night environment.
• AR/AG glass – The anti-reflective (AR) coating on the protection glass performs well in tough ambient light conditions. With the normal glass, the strong reflection of the ambient light diminishes visibility and causes problems for the viewer. Anti-reflective coated protection increases the contrast by enhancing the light transmission rate over 95 percent and can effectively diminish the mirror images. The multi-layer vapor deposition coating either on one side or two sides of the glass is designed to minimize reflectance and maximize transmittance. Another solution is an anti-glare (AG) coated protection glass, a microscopically rough surface laminated onto the top layer of the display that can diffuse glare. The chemically etched glass that has a slightly textured finish can reduce reflection by scattering light directed on its surface. It can soften the image of direct light sources visible in the reflection of the viewing area.
• Light sensor – Light sensor detects the change of illumination outside, and then sends the signal to MCU via I2C interface. The MCU asks the inverter to switch the brightness if the outside illumination changed over the default. The MCU transmits pulse width modulation (PWM) signal to the inverter, and then the inverter changes the brightness of the panel.
• Optical bonding – Reflection of light may be specular, mirror-like or diffuse depending on the nature of the interface. Optical bonding helps to reduce the reflection problem. By using the adhesive whose refractive index is very close to glass and panel (polarizer glass), we can reduce the reflection that occurs when light is transmitted through glass and panel.

Summary

When choosing a LCD solution for your application, it is important to consider the operating environment first. Based on the usage scenario, you can figure out which technology better suits your application. Winmate Inc.'s sunlight readable display solutions are available for industrial operating.