What are the four main parameters of LCD screen

- Oct 17, 2019-

1. Contrast


The control ic, the optical filter and the directional film selected at the time of manufacture of the lcd are related to the contrast of the panel, and the contrast ratio can reach 350:1 for a general user, but the contrast level in the professional field can not meet the requirements of the user. With a contrast of 500:1 or even higher relative to the crt display, only a high-grade liquid crystal display can achieve such a degree. 


In the market Samsung, ASUS, lg, and so on, now the lcd monitor can reach the level of 1000:1 contrast, but because the contrast is difficult to measure accurately by the instrument, it is the time to go to see it in person. 


LCD screen

2. Luminanc


Lcd is a substance that is between the solid and the liquid and is itself non-luminous and requires the use of an additional light source. Therefore, the number of lamps is related to the brightness of the liquid crystal display. 


The earliest liquid crystal display has only two upper and lower lamp tubes, and now, the lowest of the universal type is the four-lamp, and the high-end is a six-lamp. 


The four-tube design is divided into three types of arrangement: one is one lamp tube at four sides, and the disadvantage is that the black shadow is present in the middle, and the method for solving the problem is that the upper and the lower four lamp tubes are arranged in a flat way, and the last one is in the form of a "u" type, In fact, two light tubes are generated in a phase of a two-lamp phase. 


The six-tube design actually uses three lamp tubes, and the Chinese manufacturers bend the three lamp tubes into the "u" type, and then are placed in parallel so as to achieve the effect of six lamp tubes. 

LCD screen


3. Response time


Response time refers to the reaction speed of liquid crystal display to input signal, that is, the reaction time of liquid crystal from dark to bright or from bright to dark (brightness from 10% ≤ 90% or 90% ≤-> 10%), usually in milliseconds (ms). 


To make this clear, we have to start with the perception of dynamic images in the human eye. There is a phenomenon of visual residue in the human eye, and the picture of high speed movement will form a brief impression in the human brain. Cartoons, movies and so on until now the latest game is the application of the principle of visual residue, so that a series of gradual images in front of people quickly and continuously display, then form a dynamic image. The acceptable display speed is generally 24 pictures per second, which is the origin of the movie 24 frames per second. If the display speed is lower than this standard, people will obviously feel the pause and discomfort of the picture. 


According to this index, the display time of each picture needs to be less than 40 Ms. In this way, for LCD, response time 40ms has become a barrier, higher than 40ms display will appear obvious picture flicker phenomenon, let people feel dazzling. If you want the image to not flash, it is best to reach a speed of 60 frames per second. 


4. Visual angle 


The visual angle of lcd is a problem that gives the person a headache, and when the back light source passes through the pole piece, the liquid crystal and the alignment layer, the output light has directivity. 


That is, most of the light is emitted vertically from the screen, so when viewing a liquid crystal display from a large angle, it is not possible to see the original color, and even to see full white or full black. 


To solve this problem, manufacturers are also working on the development of wide-angle technology, so far, there are three more popular technologies, namely, tn film, ips (in-plane-switching) and mva (multi-domain vertical alignment).