Reflective and Transflective Displays - What Are They?

Reflective Diplays

Reflective liquid crystals are unique because they operate without the use of a backlight. Instead, they rely solely on ambient light. This allows the device to consume very little power. In fact, the power consumption is typically reduced up to 60% more so than other liquid crystal displays, such as the transflective displays. Some of the older calculators used the reflective displays.

Reflective displays also have two polarizers and a diffuse reflector behind the display. Sometimes this may lead to a parallax in the desired image on the display. Other reflective liquid crystal displays that are used to display more information on the display only use one polarizer and have diffuse reflectors as pixel electrodes.

Disadvantages Of Reflective LCDs

Although reflective LCDs were very efficient for their purpose, there are some drawbacks when using this type of display. Reflective displays rely on ambient light, which is any sort of outside light, for example sunlight or overhead room light. So, obviously reflective displays are useless in the dark and the usability drastically falls when lighting is scarce or low. The performace of the reflective display, therefore, is dependent upon the amount of ambient lighting, something that the user may not always be able to control.

Performance of pure reflective color lcds is gen. not acceptable, contrast, luminance and color gamut degrade much when light has to pass through 2 color filters (coming in/out). However, purely transmissive LCDs perform great indoors but their contast drops w/increasing ambient light.

Transflective Displays

Transflective displays basically adapt to their surroundings, making them somewhat superior to their reflective counterparts. When color is needed, transflective displays have become very common and often popular to use. A transflective liquid crystal display reflects most of the ambient light that may surround it and adapts to the amount of light within the user’s area.

In the image below, figure 1 shows a transflective LCD panel in a high ambient lighting environment. In this case, the sensor within the panel allows the backlight to be turned off (reflective mode). While figure 2 shows a low lighting environment, which causes the sensor to turn the backlight on for ultimate readability (transflective mode).

Advantages Of Transflective Displays

The displays have a split pixel design, which allows it to operate without a backlight (reflective mode) in good ambient lighting and in poor lighting.

There is a sensor within the display that tells the display to operate in reflective mode or switch to backlight usage. In poor lighting, the backlight is turned on to properly display the image. This allows the display to be useful in both high and low lighting. A well designed transflective color lcd can operate and maintain high contrast ratio, even in full sunlight of 100 klux.

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