TFT LCD Displays | Product Training Module

This TFT LCD Displays article is a multi-part series on the basic options available for color active matrix display modules. This series is brought to you by Focus Display Solutions in Chandler, Arizona.

Aspect ratio for TFT LCD Displays

Aspect Ratio is the ratio of the size of the display in the horizontal vs. the vertical dimensions.

The 4:3 aspect ratio generally reflects older products. The 16:10 aspect ratio had its largest use in the 1995–2010 period, and the 16:9 aspect ratio tends to reflect the most current standard.

Driver Element

The driver element is the method of how each pixel or dot is driven. Driven is another word for how each pixel is energized. There are two methods used to drive LCD displays.

ACTIVE MATRIX

In Active Matrix displays, each dot or pixel is attached to a switch-device, or transistor, which actively maintains the pixel state while other pixels are being addressed; the transistor only has control over one pixel. This allows the pixel to be controlled independently of all the other pixels. This eliminates the needs for duty cycle or refreshing that is necessary for passive displays.

PASSIVE MATRIX

A dot or pixel in a Passive Matrix must maintain its state without a dedicated transistor. The pixel if refreshed for a short period of time and then allowed to ‘fade’. The pixel is then re-energized for a short period of time only to fade again for a short period of time.

Examples of passive displays include character and graphic monochrome displays.

Dot Pitch

Dot pitch is the distance, center of dot to the center of the next dot, between pixels. The smaller the distance between the dots, the sharper the display looks. More pixels on a displays require more drivers to maintain. This increases the cost for TFT LCD displays.

Surface Treatment

The surface of TFT LCD displays contain an anti-reflective (AR) coating to reduce the reflection or glare of ambient light such as the sun. Without this anti-glare feature, the display would look ‘washed out’ or ‘faded’. AR is a coating of magnesium fluoride that lowers the amount of reflected light. This is done by lowering the refractive index of the LCD surface to a value closer to air.

Color Arrangement

There are two main types of color arrangements used on RGB (Red, Green, Blue) color displays. These are stripe-typed and delta-typed. Each pixel, or dot, is made up of three smaller sub-pixels, or sub dots. Each one of these sub-pixels is either red, green or blue. Each sub pixel can be addressed, that is turned ON and OFF independently of the other dots.

Red, Green and blue are the primary colors, every other color can be created by mixing different levels of each of the primary colors.