1. What constitutes a sunlight readable or outdoor readable LCD?
First, the display screen on a sunlight readable/outdoor readable LCD should be bright enough so that the display is visible under strong sunlight. Second, the display contrast ratio must be maintained at 5 to 1 or higher.
Although a display with less than 500 nits screen brightness and 2 to 1 contrast ratio can be read in outdoor environments, the quality of the display will be extremely poor. A good sunlight readable display is typically considered to be an LCD with 1000 nits or greater screen brightness with a contrast ratio greater than 5 to 1. In outdoor environments under the shade, such a display can provide an excellent image quality.
2. What is Luminance?
Luminance is the scientific term for hotopic Brightness which specifies the visual brightness of an object. Luminance is specified in candelas per square meter (Cd/m2) or nits. In the US, the British unit Foot-lamberts (fL) is also frequently used. To convert from fL to nits, multiply the number in fL by 3.426 (i.e. 1 fL = 3.426 nits).
Luminance is a major determinant of perceived picture quality in an LCD. The importance of luminance is enhanced by the fact that the human mind will react more positively to brightly illuminated scenes and objects. Users are typically more drawn to brighter displays that are more pleasing to the eye and easier to read. In indoor environments, a standard active-matrix LCD with a screen luminance around 250 nits looks good. However, a sunlight readable LCD with a screen luminance of 1,000 will look even more beautiful.
3. What is Contrast Ratio (CR)?
Contrast ratio (CR) is the ratio of luminance between the brightest “white” and the darkest “black” that can be produced on a display. CR is another major determinant of perceived picture quality. If a picture has high CR, you will judge it to be sharper and more crisp than a picture with lower CR. For example, a typical newspaper picture has a CR of about 5 to 7, whereas a high quality magazine picture has a CR that is greater than 15. Therefore, the magazine picture will look better even if
the resolution is the same as that of the newspaper picture.
A typical AMLCD exhibits a CR between 300 to 700 when measured in a dark room. However, the CR on the same unit measured under ambient illumination is drastically lowered due to surface reflection (glare). For example, a standard 200 nit LCD measured in a dark room has a 300 CR, but will have less than a 2 CR under strong direct sunlight. This is due to the fact that surface glare increases the luminance by over 200 nits both on the white and the black that are produced on the display screen. The result is that the luminance of the white is slightly over 400 nits, and the luminance of the black is over 200 nits. The CR ratio then becomes less than 2 and the picture quality is drastically reduced.
4. What is a Viewing Angle and why does it matter?
The viewing angle is the angle at which the image quality of an LCD degrades and becomes unacceptable for the intended application. As the observer physically moves to the sides of the LCD, the images on an LCD degrade in three ways. First, the luminance drops. Second, the contrast ratio usually drops off at large angles. Third, the colors may shift. The definition of the viewing angle of an LCD is not absolute as it will depend on your application.
For LCDs used in outdoor applications, defining the viewing angle based on CR alone is not adequate. Under very bright ambient light, the display is hardly visible when the screen luminance drops below 200 nits.
5. Are there thermal management issues with i-Tech backlights?
Any high brightness backlight system will consume a significant amount of power, thereby increasing the LCD temperature. The brighter the backlight, the greater the thermal issue. Additionally, if the LCD is used under sunlight, additional heat will be generated as a result of sunlight exposure. Temperature issues can be handled through proper thermal management design.
6. What is the Optical Bonding sunlight readable displays?
Understanding and controlling reflected light will dramatically improve the performance of a display in any ambient lighting condition
Sunlight viewability of a display depends on the differences between "lumination" and "illumination" of the display. The lumination of the display is its brightness. 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. Illumination is the amount of ambient light shining onto a display. The readability of a display is dependant on the amount of light that is being reflected off of the display.
7. What is Anti-Reflection & Anti-Glare Protection Glass Coating Technology?
We provide two different choices of optical enhancement solutions that include anti-reflective coated and/or anti-glare protection glass. These technologies can be widely used in outdoor and indoor environment by enhancing optical performance of displays.
How does this technology work?
The anti-reflective coatings on the protection glass have excellent performance in tough ambient light conditions. With the normal glass, the strong reflection of the ambient light diminishes visibility and causes problems for viewer. Our special anti-reflective coated protection glass can increase contrast by enhancing light transmission rate over 95% (light reflectance rate less than 5%) and can effectively diminish the mirror images. The multi-layer vapor deposition coating either on one
side or two sides of glass is designed to minimize reflectance and maximize transmittance.
Another solution, with an anti-glare (AG) coated protection glass, a microscopically rough surface laminated onto the topmost of display 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.
Benefits
• Anti-reflective coated protection glass can minimize mirror image and maximize transmittance
• Anti-glare coated protection glass can scatter light directed on the surface and soften the image of direct light sources visible in the reflection of the viewing area
• With two side AR and one side AG coated glass are suggested to provide the best visibility
Applications
• Exhibition Signage
• Outdoor Kiosks
• Public Information POS
• Transportation
For more information please contact us: info@prtronic.at
