Sunlight Readable LCD/ High Brightness LCD Monitor Technology

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 a mere 2 to 1 contrast ratio can be read in outdoor environments, the quality of the display will be extremely poor. At i-Tech, a truly 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.

Luminance is the scientific term for hotopic Brightness?which specifies the visual brightness of an object. In layman's terminology, it is commonly referred to as brightness? 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.

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.

i-Tech sunlight readable LCDs with 1500 nits screen brightness will have a CR over 8 with the same amount of glare under the same strong sunlight, making the picture quality on these units extremely good. For further reading on contrast ratio, please see Tech Note 0101, Page 2, the Display Contrast Ratio.

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.

Most LCD manufacturers define viewing angle as the angles where the CR (contrast ratio)^3 10. For LCDs designed for less demanding applications, the viewing angle is sometimes defined as the angles where the CR^3 5.

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. Therefore, i-Tech defines the viewing angles based on both the CR and the Luminance.

For further details, please refer to data sheets for specific i-Tech sunlight readable LCD modules.

All LCD backlights powered by cold cathode fluorescent lamps (CCFL) require inverters. An inverter is an electronic circuit that transforms a DC voltage to an AC voltage, which drives the CCFLs. i-Tech Technology manufactures inverters for all its products. Additionally, Applied Concepts and ERG also provide inverters for our products as well.

The dimming range or dimming ratio of an inverter specifies its capability of performing backlight luminance adjustment. For inverters used in notebook computers and LCD monitors, the backlight luminance can be adjusted typically over a dimming range of less than 10:1. That is, the luminance is adjusted from 100% down to about 10%.

For very high brightness backlights used in i-Tech Technology sunlight readable LCD modules, the inverters must be able to provide a much wider dimming range. Otherwise, the LCD screen will be too bright during nighttime conditions. Therefore, our inverters provide a typical dimming ratio of 200:1, meaning that the luminance can be adjusted from 100% down to 0.5%.

Dimming capabilities are beneficial because lowering the backlight luminance will result in a lengthening of the backlight life. It also lowers the power consumption and the related thermal management issues.

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.

We provide TFT LCD with reflective mode of illumination without compromising its transmissive illumination. With the imposed reflective function, the modified LCD can reflect the ambient light passing the LCD cell and utilize 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 all lighting conditions including direct sunlight regardless the LCD's original brightness.

The market demands for outdoor LCD applications are expanding, such as mobile navigator/video systems, PDA, personal organizer, Tablet PC, notebook computer, and Kiosk display etc. However, a regular transmissive LCD is very difficult to read under strong ambient light. This limits the outdoor applications of a conventional transmissive LCD.

The high bright LCD and the transflective LCD are the solutions generally utilized for outdoor applications. However, both solutions have some shortcomings. Because of the added lamps, high bright LCD creates some undesirable problems, which include high power consumption, excessive heat generation, increased dimensions, electrical circuit alterations, and shortened LCD lifetime. Thus, it is usually troublesome and costly to accommodate a high bright LCD in systems. Though giving good performance under the direct sunlight, the transflective LCD trades of its indoor performances.

Problems noticed in transflective LCD include narrow viewing angle, discoloration, low brightness, and loss of contrast. Moreover, the transflective LCD is currently limited in choice of sizes and resolutions.

On the other hand, a Transflective LCD is readable everywhere including outdoor environments without extra power consumption and excessive heat generation. The indoor viewing qualities are also enhanced. The modified unit fits right back into its original system with no need of any alteration and extra effort. Thus in your choice of size, resolution, and model, a direct sunlight readable LCD is conveniently incorporated into your device.

i-Tech is a premier supplier of optical bonding and performance added passive enhancements for all flat panel . i-Tech Optical Bonding process produces an optical bond between any display cover glass or touch panel, and any size LCD.

In the world of LCD's, i-Tech takes display enhancement to a new level above all others. Utilizing advanced proprietary optical bonding technology; i-Tech overcomes optical challenges for display product manufacturers at an affordable price. In a wide range of applications, standard liquid crystal appear to "washed out" in high ambient lighting conditions. This wash out is due to excessive reflections and glare caused by bright light.

Commercially available LCDs, especially when protected by a separate cover glass or plastic shield, can not deliver enough brightness to make the display functional in outdoors or in other high ambient light applications. The exclusive Optical Bonding process from i-Tech provides a significant reduction of ambient light reflections at an affordable price, compared to other display enhancement technologies.

Optical Bonding seals either a top cover glass or touch screen directly to the face of the display bezel. Our bonding process eliminates the air-gap between the display and the cover glass, vastly reducing reflective light, which causes visual washout of the display image. Optical Bonding also enhances structural integrity by supporting the LCD assembly with the cover glass. The bond maintains perfect display uniformity while providing shock protection, unlimted humidity protection, and elimination of fogging caused by trapped moisture accumulating in typical air-gap assemblies.

Optical Bonding provides the best reduction of ambient light washout of any commercially available enhancement technology.

Optical Bonding has a lower cost than most other competing technologies.

Optical Bonding offers superior ruggedization, enhancing the display durability under vibration, shock and other environmental extremes.

Optical Bonding Technology

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.

Light travels through a variety of transparent materials; such as air, glass, plastic, and even water. These material's abilty to transmit light is measured by their "indices of refraction". As light transfers from one material to another, such as air to glass, the differences the index of refraction will cause reflection. In the case of an air-to-glass interface, the reflection will be slightly less than 5% of the ambient light. All surfaces that have an index mismatch will reflect and the reflection is cumulative. In the case of a standard glass or plastic window, there are three surfaces with an index mismatch which will create a total relfection of nearly 15% of the ambient light. If the total reflection (in nits) is close to the displays brightness, the contrast of the display will be reduced to the point where the display's readabilty is reduced to unacceptable levels.

Optical Bonding from i-Tech is a solid, transparent bond which optically couples the front cover glass or touch screen directly to the face of the display. This internal bond eliminates reflection from the two internal layers. The outer surface of the window is 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 300-500 nits of brightness will be viewable in daylight or indirect lighting conditions. At 500-800 nits brightness, most displays will be completely sunlight viewable.

Aside from the optical quality, Optical Bonding elminates the air-gap which prevents heat build-up from the "greenhouse" effect and prevents fogging from moisture or contamination from dirt or particles. It also offers shock protection and other damage to the LCD itself.

Value-add backlights and edge lights

What is this 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.

Technology/ Function Diagrams

Products use this technology

These coating glass solutions we provided are now available for full range displays from 6.4? to 37? by customized request.

Data Sheet

Clearing Point - The temperature at which the liquid crystal fluid changes from a nematic into an isotropic state. In practice, a positive image LCD will turn totally black at this temperature and will therefore be unreadable. Because the clearing point is different for every fluid type, ask for design assistance from your supplier if high temperature operation is critical in your application.

Also, for most cases, both TN, HTN and STN utilize the phase known as nematic for display purpose. Within this phase, the liquid crystal has a "rod shape" exists within the solution which has fast response and has excellent electro-optic properties. This phase, however, only exists within a limited temperature range. The higher end of this temperature range is known as clearing point, above which, the liquid crystal lost its birefrigerance properties and cannot bend the light path anymore. Thus the polarizer will then be the only factor which affect incoming and out coming light. When the LCD is cooled down to below its clearing point, the display should be working again. The temperature for the clearing point varies greatly from material to material and you should contact our engineers regarding what you have. Normally a safe margin should be used to avoid clearing point when designing the display.

Front OSD and Dimming Knob to control Backlight brightness from 0 to 100%

Isotropic Stage The point where the fluid heats or cools to where it is no longer in the twisted nematic state. Since the molecules can no longer twist light, all incoming light is absorbed.

Isotropic Stage

Now I-tech's standard light sensor design has five-steps brightness settings, Lightest, Lighter, Normal, Dark, and Darkest.

Each step has its own illuminate range according different environment illumination. This technology makes the use of visual application more friendly and intelligently.

TouchScreen Solutions is a specialist manufacturer of touchscreens, optical filters to enhance the performance of electronic displays, and transparent composites.

Touch sensor is based on projected capacitive technology which enables the device to sense through a protective screen in front of the display.

By utilising TouchScreen Solutions’s traditional lamination expertise, touchscreens are designed to provide the highest levels of light transmission, excellent readability and unsurpassed protection against a wide range of physical threats. The touchsacreens are accurate, highly dependable and have a rapid response time

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