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Redmi 7/7A

[Discussion] [How it Works #5] Type of Display and How They Work!

2019-05-13 01:17:36
1184 48

Dear Mi Fans!

This is a new series about all the components of your smartphones and how they work inside your device!
Almost all modern smartphones are equipped with Display. But not everyone knows how they work! Today you'll know more about this smartphone detail.

The quality of the displayed image on the screen of the mobile device depends on the technology on which the display is produced. Currently the most popular display types are TFT, OLED, AMOLED (including Super AMOLED and Ultra AMOLED), IPS (Super IPS) and Super LCD.

  • TFT (Thin Film Transistor) is a thin-film transistor technology that is used in active-matrix displays. For each pixel of the image there are three transistors (each of which corresponds to one of the three primary colors — red, green, or blue), as well as a capacitor supporting the required voltage. The main drawback of TFT screens is high power consumption.
  • OLED (Organic Light Emitting Diode) is an organic electro-luminescent display. Such displays have high brightness and contrast, and besides they do not need additional illumination and consume less energy. The main disadvantage is the expensive production technology.
  • AMOLED (Active Matrix Organic Light Emitting Diode) is an enhanced version of OLED technology. AMOLED displays have an active matrix with organic LEDs. This allows the screen to bend a little without the risk of breaking, and also gives the screen a very small thickness and low weight. The main advantages of this type of screens are high brightness and contrast, low power consumption, as well as rich color reproduction of the image.

Some devices use advanced versions of AMOLED technology - Super AMOLED and Ultra AMOLED. According to manufacturers, such displays work even more economically, have improved color reproduction and are less “blind” in the sunlight.

  • IPS and Super IPS are varieties of TFT displays. Such screens are characterized by large viewing angles, perfect black color and excellent color reproduction.
  • Super LCD is an improved version of LCD screens. Such screens have increased viewing angles and lower power consumption.
Currently, for the production of consumer monitors are used two of the most basic, so to speak - the root, the manufacturing technology of matrices - LCD and LED.
  • LCD is an abbreviation of the phrase "Liquid Crystal Display",
  • LED stands for “Light Emitting Diode”, which in our language is read as a light-emitting diode, or simply LED.

All other types are derived from these two pillars of the display industry and are refined, modernized and improved versions of their predecessors.

Liquid Crystal Display, that is, LED - it was this technology in the late 1990s that made it possible to transform monitors and televisions from large boxes with harmful electron-beam tubes for people inside into thin elegant devices. It also opened the way to create of thin displays for compact gadgets such as: laptop, PDA, smartphones and other devices.

Liquid crystals - a substance that is both fluid, as a liquid, and anisotropic, like a crystal. The latter quality means that with different orientations of liquid crystal molecules, optical, electrical, and other properties change.

Crystalline, liquid crystalline, liquid: the crystals are transferred to another state of aggregation under the influence of temperature.

In displays, this LCD property is used to control the light conductivity: depending on the signal from the transistor, the crystals are oriented in a certain way. In front of them is a polarizer that “collects” light waves into the plane of crystals. After them, the light passes through the RGB filter and becomes red, green or blue, respectively. Then, if not blocked by the front polarizer, it appears on the screen as a subpixel. Several of these light streams are interconnected, and on the display we see a pixel of the expected color, and its combination with neighboring pixels is capable of producing a gamut of the sRGB spectrum.

LCD pixel circuit

When the display is turned on, the backlight is carried out by white LEDs located around the perimeter of the display, and is evenly distributed over the entire area thanks to a special substrate. Here we run into problems with LSD monitors or displays. For example, to the pixels, which should be black, the light still comes. In the old and low-quality displays, the "black glow" is easily discernible.
It happens that the crystals “get stuck”, that is, they do not move even when receiving a signal from the transistor, then a “broken pixel” appears on the display, this can be seen when there are noticeable points on the screen in a certain color. Due to the specifics of the light source, white light can be seen at the edges of LCD monitors, and LCD smartphones cannot be absolutely frameless, although both generations of Xiaomi Mi Mix and Essential Phone are striving for this.
However, in the specifications of the devices we see not LCD, but mysterious TN, TFT, IPS or even Retina. Now we will try to figure it out in such a confusing terminology.

LED Display is one of the main screen displays that are being commercially used. The biggest advantage of the LED display is its efficient and low-energy consumption, which is especially needed for handhelds and chargeable devices such as mobile phones and tablets. An LED display consists of a number of LED panels that, in turn, consist of several LEDs. LEDs have numerous advantages over other light-emitting sources that can be used alternatively. Aside from being power efficient, LEDs produce more brilliance and greater light intensity. LED Display is different from the vacuum fluorescent display used in some consumer electronics such as car stereos, videocassette recorders, etc., and, hence, these two should not be confused with each other.

TN, or TN + film
TN, or TN + film. In fact, Twisted nematic is a “basic” technology that implies the polarization of light and the twisting of liquid crystals into a spiral. Such displays are inexpensive and relatively easy to manufacture, and at the dawn of their presence on the market they had the lowest response time - 16 ms - but they were characterized by low contrast and low viewing angles. Today, technology has made great strides forward, and the TN standard has been replaced by the more advanced IPS.

Advantages - low response time, low cost.
Disadvantages - small viewing angles, low contrast, poor color reproduction, inertia, power consumption

IPS (in-plane switching). Unlike TN, the liquid crystals in the IPS matrix do not twist into a spiral, but turn all together in the same plane parallel to the display surface. This allowed us to increase comfortable viewing angles to 178 ° (that is, actually up to a maximum), which is why you do not feel color distortion even when the smartphone or computer monitor (laptop) is turned sideways to you, to significantly increase the contrast of the image, to make the black color much deeper and more realistic while maintaining comparative safety for the eyes, although there is still a lot of controversy about this.

Advantages - viewing angles, color rendition.
Disadvantages - the price is too high compared with TN, the response time is rarely below 16 ms.

Comparison of TN matrix and IPS

  • Maximum viewing angles.
  • High energy efficiency (low energy consumption).
  • Accurate color reproduction and high brightness.
  • The ability to use high resolution, which will give a greater density of pixels per inch (dpi).
  • Good behavior in the sun.

  • Higher price than TN.
  • Distortion of colors with a large tilt of the display (yet, the viewing angles are not always the maximum for some types).
  • Saturation of color and insufficient saturation.

Today, most phones use IPS-matrices. Gadgets with TN displays apply except in the corporate sector. If a company wants to save money, it can order monitors or, for example, telephones for its employees at a lower price. They can be equiped with TN-matrices, in them, but no one gonna buy such devices for personal use.

A breakthrough in the LED display market occurred when it became possible to use thin-film transistors and capacitors to control each pixel (more precisely, subpixel) separately, and not a group. In such a system, which is called an active matrix (active matrix, AM), one transistor is responsible for the beginning and end of the signal transmission to the capacitor, and the second for the signal transmission from the diode to the screen. Accordingly, if there is no signal, the diode does not glow, and the output is the deepest black color, because the glow is absent in principle. Due to the fact that the diodes themselves, which lie practically on the surface, shine, the viewing angles of the AMOLED matrix are maximum. But if you deviate from the axis of view, the color may be distorted - go to red, blue or green, or go at all in RGB waves.
Such displays are distinguished by high brightness and contrast of the picture. Previously, this was a real problem: the first AMOLED screens were almost always “out of sight”, their eyes could get tired and sore. In some displays, pulse-width modulation (PWM) was used so that the dark image does not “go away” into a purple hue, which also turned out to be painful for the eyes. Because of their organic origin, the diodes sometimes burned out within two to three years, especially when displaying a constant picture for a long time.

AMOLED technology has several advantages over conventional displays:
  • improved image quality of the picture,
  • large color gamut of the image
  • increased speed (about 0.01 ms),
  • low power consumption
  • almost maximum viewing angle without loss of image quality,
  • small display thickness
  • do not need additional lighting.

The name Super AMOLED was invented by Samsung marketers for their displays. The technology of image transmission has not changed and remained, as in the usual AMOLED. The main difference lies in the integration of the touchscreen in the screen, rather than superimposing it on top, as it was before. Due to this integration, an extra layer of air has been eliminated. According to Samsung developers, this made it possible to reflect 5 times less sunlight than conventional AMOLED.

Another difference between Super AMOLED and AMOLED is the subpixel layout. Super AMOLED uses PenTile RGBG location instead of traditional RGB RGB. The transition to such an arrangement, Samsung explained that the human eye perceives the blue color worse, and the blue pixels are less durable in the screens, so they tried to reduce them. After the release of models of phones with this arrangement of subpixels, buyers began to complain about the not high-quality display of the picture and therefore Samsung had to return to the traditional RGB layout, calling such a screen already Super AMOLED Plus.

Based of the foregoing, we can summarize that:
If you need, let's say, a good tablet, not only for work, but also show high quality photos, then the ideal choice would be a model with IPS technology.
If you plan to use an electronic device, for example a phone, just for communication -  then choose a modelwith TFT display.

[How it Works #4] Type of Touchscreen and How They Work!

Thanks to Administrator @Elaine2046


Number of participants 9 Experience +77 Pack Reason

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2019-05-13 01:17:36
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Beta Team-China

Dorarch | from MI MAX 3


Thanks for sharing
2019-05-13 03:12:27

Pro Bunny

Andler1968 | from MI 8 SE


Thanks. Very good explaination
2019-05-13 03:20:35
Very good explaination.
2019-05-13 03:23:14
Thanks for sharing
2019-05-13 03:30:17

Wizard Bunny

hackersb | from app


Nice detail thread
2019-05-13 03:39:40

Pro Bunny

Humminglights | from Mi MIX 2


Thanks for the Information
2019-05-13 04:52:45
Thanks for sharing this informative thread

2019-05-13 04:56:54

Pro Bunny

Baal05 | from Redmi 5A


Very good, thanks for sharing
2019-05-13 05:30:58

Grand Master Bunny

Ian Adoe | from Redmi Note 5A


nice explanation
2019-05-13 05:44:02


ph.eliezer | from Redmi 5


Awesome article
2019-05-13 05:44:34
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