Lcd, Oled screen light-emitting principle

Lcd, Oled screen luminous principle introduction.

Terminology.

OLED：Organic Light EmitTIng Diode 

    LCD：Liquid Crystal Display 

DP：dot pitch Dot pitch, the distance between two pixel dots, affects the fine quality of the picture and the viewing distance

PX：pixel Pixels, the most basic display unit elements that make up an image

  VSYNC：VerTIcal Sync

   HSYNC： Width

Synopsis.

LCD screen (liquid crystal screen)
OLED screen (Organic Light Emitting Tube)
Video memory (storage space for storing pixel point data)

LCD screen.

Liquid crystal is a special substance between solid and liquid. It is an organic compound, which is liquid in its normal state, but its molecular arrangement is very regular like a solid crystal, hence the name liquid crystal. If an electric field is applied to the liquid crystal, it will change the arrangement of its molecules, thus changing the direction of light propagation, and with the polarizing light sheet, it has the effect of controlling the light transmission rate, and then with the color_filter, changing the voltage applied to the liquid crystal, it can change the amount of light transmission of a certain-color.

The backlight emits white light, through the polarizer for the initial handsome selection of light, through the glass plate to reach the liquid crystal control circuit, light through the liquid crystal gap, the external voltage applied to the liquid crystal, will change the angle of light deflection, light in the glass plate, through the polarizer, and finally projected on the red, green and blue polarizer, showing different colors, and finally formed a display unit, called pixel points

Display resolution setting on the computer, corresponding to 1920 x 1080 pixels

Monitors （S） 1.27MP35

Resolution（R） 1920×1080 Recommend

Direction （O） Horizontal

LCD itself does not emit light, the backlight is required to provide a light source, light through a series of processing to the output, the output light intensity is much lower than the intensity of the light source, the energy utilization rate is lower, (energy-saving than CRT displays), LCD processing, will lead to a narrower display direction, corresponding to its perspective is smaller, from the side of the screen will not be able to see his display content, color conversion, liquid crystal molecules also need to consume a certain amount of time to rotate, resulting in a low response speed of the screen

Larger screen for outdoor use, using LED dot matrix color display, each pixel, containing red, green and blue LED lights, display principle similar to the LED color lights on the experimental board

OLED screens.

OLED display and LED dot true color display principle is similar, because it uses the pixel unit is “Organic Light Emitting Diode (Organic Light EmitTIng Diode)” pixel density is much higher than the ordinary LED dot matrix display

The use of organic light-emitting layer, directly emitting light to the outside, has a higher light utilization rate and can display a higher brightness

OLED displays do not need backlight, high contrast ratio, thin and light, wide viewing angle, fast response time and other advantages, the price is higher

Pixel: The most basic display unit element of the image, the display pixel refers to the smallest point of his imaging Embedded devices, the display is described as “row pixel value * column pixel value” The color reference color on the display, red, green and blue RGB888 indicates that the color is expressed using 8bit RGB565, corresponding to red 5bit, green 6bit, blue 5bit Color depth indicates the number of bits corresponding to each pixel 16bit or 24bit, 24bit is sufficient for regular use

Point distance: the distance between two pixel points, will affect the fine degree of picture quality and the viewing distance

Touch screen display, divided into two components, display + touch screen

The devices associated with the control color will eventually correspond to the color data storage and the processing of RGB three kinds of data

Without LCD controller, corresponding to the control signal line of the LCD panel

HSYNC, VSYNC two kinds of signals, corresponding to the completion of data transmission, a row and a column of transmission is completed, will issue a signal to the outside

“Frame/second” indicates the refresh characteristics of the LCD, that is, how many frames per second the LCD can refresh the image

Video memory.

Each pixel in the LCD screen is data, in practice, it is necessary to cache the data of each pixel and then transfer it to the LCD screen, this way of storing display data is called memory.

Minimum requirements for the display memory: at least one frame of display data of the LCD screen can be stored.

Using the RGB888 format for storage, for an 800×480 resolution display, the corresponding storage space required is 3 x 800 x 480 = 1152000 bytes.

Using RGB565 format, one frame display data size: 2x800x480=768000 bytes

If there is no discrete video memory on the device, it will consume a lot of CPU resources, and the integrated graphics card will allocate a designated memory area for displaying the screen.