Everything about TFT LCD displays

What are TFT LCD displays? What is worth knowing about them?

It is a type of liquid crystal displays using special thin-film transistors. This technology allows for the construction and easy control of high-resolution displays, as well as for obtaining much higher image quality. Displays of this type are almost ubiquitous – they are commonly used in computer and television screens, mobile phones, household appliances or even industrial devices.

In this article, you will learn about the most important parameters of TFT LCD displays, and you will also find a set of information that will help you choose the right display for your needs.

What is TFT technology?

Układ pikseli w typowej matrycy TFT LCD

Photo 1. Arrangement of pixels in a typical TFT LCD matrix (microscopic image). The small notches in the corner of each sub-pixel are where the thin-film transistors are located.

In typical passive liquid crystal displays, each image element (segment or pixel) is directly controlled by an electrical signal. This makes it possible to easily control individual segments independently of others. This solution works well in simple displays used, for example, in watches or calculators. In the case of high-resolution displays, however, it is impractical – such a display has poor contrast and a long response time. Therefore it applies active matriceseach pixel has a small control transistor. In addition to improving the image quality, they allow you to easily address individual pixels and refresh the image progressively – line by line. The transistors also prevent the discharge of charge from the pixels, so they retain their state even when they are not receiving a signal at that moment.

 

What parameters do TFT LCD displays have?

Below is a summary of the most important parameters of TFT LCD displays:

Matrix type

There are many types of TFT displays, each with different characteristics. The most popular are:

  • IPS (in-plane switching) – characterized by very good color reproduction and the ability to observe the image from any angle,
  • TN (twisted nematic) – cheaper, but have much worse color reproduction and limited viewing angles.

 

More information on this subject can be found in our article: TFT displays – characteristics, types, application .

Resolution and pixel density

Resolution is one of the basic parameters of displays – it determines the number of pixels the matrix has. The number of pixels (or lines) horizontally and vertically is given. Higher resolution allows more detail to be placed on the displayed image. Resolution is also related to pixel densitywhich is most often specified in pixels per inch (ppi). High density allows for a sharper and clearer image, especially when we observe the display from a short distance.

Dimensions and shape

TFT LCD displays come in many sizes and shapes. Most often they are defined by specifying the diagonal length of the display area (in inches) and the aspect ratio of the long edge to the shorter one (e.g. 16: 9). However, the aspect ratio is often overlooked as the same information can be read from the resolution or dimensions of the screen.

The dimensions of the frame and the touch panel (if any) are also important when selecting the display – they are usually given in millimeters. It is also worth using the diagrams and technical drawings included in the catalog card.

Brightness

The maximum brightness of the display is given in cd / m², commonly known as a rivet. Brightness has a significant influence on the readability of the display, especially in bright surroundings – for example in direct sunlight. As a benchmark, a typical computer display achieves a brightness of approx. 250cd / m².

Our company’s offer includes high-brightness displays, ensuring a clear image in all lighting conditions – for example, LCD TFT 7.0 ″, RGB 800×480 pixels display with a maximum brightness of 850cd / m².

 

Viewing angles and orientation

Some types of LCD displays have limited viewing angles – the image seen from certain angles loses contrast or becomes difficult to read. For this reason, the range of angles over which the image should be viewed is defined. These angles are defined in relation to the display axis. Moreover, in order to increase the functionality of the display, the range of viewing angles is often slightly tilted from the axis. This deviation is given as hourly orientation. For example, 12:00 o’clock means that the observed image should be slightly above the position of the display terminals, 6:00 o’clock – from the bottom.

Color range

A parameter that defines the color range of a given display. It is defined by specifying what percentage of a given color space (e.g. sRGB , Adobe RGB) is able to display a given matrix. The wider the range of colors, the more vivid and attractive the image is for the viewer. It is also of great importance in the case of professional displays used for graphics or video processing, where faithful image reproduction is important.

Interface

The display matrix can be controlled in many ways. Each display has a connector that supports a given communication interface. These include, among others:

  • SLEEPS – Serial interface, most often found in small displays with low resolution. It is easy to implement and requires a small number of connections, but low bandwidth limits the refresh rate. An example of a display with SPI communication is offered by us LCD TFT 0.96 ″, 80x160px .
  • RGB – A special type of parallel link that operates without a buffer. It has a separate line for each bit of the displayed color, but there are buses with a width of 16, 18 or 24 bits. It allows for a much higher refresh rate.
  • LVDS – Differential serial interface. Found on some computer and television displays.
  • MIPI – High bandwidth differential interface. It uses one differential pair to transmit the clock signal and 1 to 4 pairs for data transmission. Most often used in mobile devices – tablets, mobile phones.


How to Choose the Right TFT LCD Display?

Display offer LCD is very diverse. When selecting a display, it is crucial to consider what features and capabilities we expect. Do we want fast image refresh necessary to display animation or video? Is image quality and detail more important? Will the display be used in sunlight? If you have any questions, our specialists are at your disposal – feel free to contact us via contact form. It is also worth getting acquainted with the wide range of LCD displays in our product catalog .

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