A high-definition display [on a high-definition display]

High-definition display is the inevitable product of people's pursuit of audio-visual enjoyment. This paper explains the clear expressions and meanings from three aspects, and expounds these expressions and their transformation relations. At the same time, some misunderstandings about HD in people's life are pointed out, and the selection method of HD display products is introduced. Finally, the future display technology is prospected.

Keywords: high definition HDTV

China Library Classification Number: TN949. 1 Document Identification Number: A.

In recent years, high-definition display has gradually become popular in our lives, and the concept of high-definition has been put forward by mobile phones, digital cameras, online movies and televisions. This is the result of the continuous development of display technology, and it is also a sign of the progress of scientific and technological civilization. So it is necessary for us to have a comprehensive understanding of HD display.

1 Understanding of HD

1. 1 definition expression

There are three main terms to express clarity, namely pixel, scan line and resolution. Pixel is the smallest division unit of an image, which is usually used to represent a digital camera. Depending on the number of photosensitive elements on the photoelectric sensor in the camera, one photosensitive element corresponds to one pixel. Resolution refers to the number of pixels that a display can display. Because the dots, lines and surfaces on the screen are all composed of pixels, the more pixels the display can display, the finer the picture will be, and the more information can be displayed on the same screen area. The whole image can be imagined as a big chessboard, and the resolution is expressed by the number of intersections of all warp and weft. Such as: 1920? 080。 Scan line is usually used to refer to the definition of video, TV and other players. This concept comes from television. Generally speaking, we can divide the picture on TV into many scanning lines horizontally. The finer the division, the clearer these pictures are and the more scanning lines there are. Such as: 720P, 1080i. Here p stands for progressive scanning and I stands for interlaced scanning. Interlaced scanning means that a frame of image is divided into two fields, odd field and even field, and the number is horizontally divided scanning lines. Theoretically, progressive scanning with the same number is clearer than interlaced scanning, that is, 1080P is clearer than 1080i.

1.2 conversion method

These parameters representing clarity can be converted. For example, a 720P-p HD movie can be expressed by resolution and converted into pixels. Can be calculated as follows:

720? 6/9)= 1280 Resolution can be expressed as 1280? 20 = 926,5438+600,000 pixels

The definition of PAL TV signal in China can be expressed as 576i, and can also be converted into resolution:

576? /3)=768 Resolution can be expressed as 768? 76 = 442,368 pixels

Here 16:9 and 4:3 represent the aspect ratio of the display screen. In the past, CRT TVs and monitors were all 4: 3, but now LCD TVs, plasma TVs and LCD monitors are all 16:9. Comparing the above data with the 5-megapixel digital camera, we can see how low the resolution of domestic PAL TV signals is and how high the resolution of the 6.5438+0.5 megapixel digital camera is.

The objective expression of 1.3 clarity

Of course, it is wrong to unilaterally pursue the above three high parameters. Generally, the number of pixels per unit display area, that is, ppi, is used to accurately express the size of definition. In fact, the clarity of the image we see is also related to the viewing distance and the size of the image. The viewing distance is too far to see the image clearly; The image is too small to see clearly, and there is no point in discussing the definition. So first of all, in the case of appropriate distance and image size, we will pursue to see more clearly and not blur. For example, in the video on the computer, blur the window to reduce "invisibility" and adjust the window to the optimal size according to your own subjective judgment. Another example is the LED advertising screen on the outdoor big screen. Standing close will have obvious graininess, you can go far and find the best viewing distance.

Therefore, the pursuit of high definition should be based on people's subjective feelings. People are different, and technical parameters can only be used as a reference. As can be seen from the above calculation results, the photos taken by the 5-megapixel digital camera have exceeded the resolution of all mainstream displays, so the display will merge several pixels into one pixel, which will forcibly reduce the resolution of the photos. So when you look at the photos taken by the16 megapixel camera on the computer, the highest resolution is only the resolution of the monitor. If imaging paper is made, it is related to the technical level of development or printing, and also to the quality of imaging paper. A normal size image paper, with 5 million pixels and160,000 pixels reflected on the photo, is clearer to the human eye and makes no difference, because the size of the image paper is smaller. As big as the star paintings of professional photographers, the gap can be reflected. Therefore, 5 million pixels is enough for home cameras, and the minimum number of digital cameras on the market now is100000. For the market, manufacturers make the pixels of digital cameras higher and higher, and other comprehensive performances of high pixels are also good. We are forced to pay for more unnecessary photosensitive elements.

1.4 How to watch HD video?

The camera takes pictures, so the definition can be high. Video is continuous, and the amount of information is much greater than that of photos. High-definition video requires high memory capacity and CPU processing speed. At present, the camera with the highest definition on the market is 1080P, so the high-definition video we see on the network will not exceed 1080P, and the resolution of video display devices such as televisions, projectors and computers will not exceed 1080P. In addition to network resources, there are Blu-ray discs, but there must be Blu-ray players. There may also be the legendary HDTV, and HDTV set-top boxes are also needed. In short, high-definition signal, high-definition decoding and high-definition display are indispensable to see high-definition, and the final playback effect will depend on the ability of the worst of these three links. There is also a signal interface that will also affect the definition, and the highest definition is HDMI. Some people buy HDTV, but the effect is not as good as the old TV at home, because the TV signal is still there. Even digital TV only changes the form of the signal, but not the signal itself. Because the signal ratio is 4:3 and the TV ratio is 16:9, people's faces are enlarged. At the same time, the TV screen is bigger than before, and the details can be seen more clearly, just like you can see the spots on a person's face, so the effect is worse.

So when will HDTV become popular? It can only be said that high-definition signals come from high-definition cameras, and the price of high-definition cameras is several times that of PAL cameras, and the cost of upgrading other equipment is higher.

2 Reasonable choice of clarity

2. 1 human eye resolution limit

The resolution of high-definition video will one day reach the limit of human resolution, just like ordinary photos taken by digital cameras. In fact, there is no difference between 720P and 1080P video played by the projector. For small screen display, it is easier to exceed the resolution limit of human eyes. Apple recently launched the iphone4 mobile phone, claiming that the display resolution of the mobile phone screen has exceeded the resolution limit of the human eye. Whether it exceeds the standard or not, we are not sure without professional testing. However, the display screen that exceeds the resolution limit of human eyes, whether it is done now or not, can be done in the future, and the resolution development is meaningless.

2.2 product selection

If you are concerned about clarity, you can choose to display electronic products in the following ways. First, surf the Internet, such as Taobao. Check the product parameters, because there is no payment in the store, the salesperson will not let you open the original package to read the instructions. In commodity parameters, no matter which method is used to express clarity, it can be converted into pixels by the above calculation method, and then divided by the size of the display screen to get ppi, which records the ppi, model, brand and price of many similar commodities. Second, prepare a USB flash drive with several HD videos in it, go to the store, find the corresponding products, play the same HD video respectively, and compare the effects. If there is no difference between low ppi and high ppi, then it is meaningless to choose high ppi. If you want to buy a TV, you must first consider a healthy and reasonable viewing distance. Divide the distance from the living room sofa to the TV cabinet or the opposite wall by 4 to get a data, which should be the diagonal length of the TV screen you want to buy. Determine the size of the TV, and choose the ppi reasonably according to the steps mentioned in the first and second items above.

3 the prospect of display technology

With the development of sound technology, display technology will gradually realize realism, and finally it will be like being there. The development of 2D HD will be meaningless, because it exceeds the resolution limit of human eyes, and 3D display will have a real sense of scene. The arrival of this era must be realized through the development of computer technology, electronic technology and communication technology. Let's wait and see.

refer to

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[3] Qingyun. Feel the feast of HD [J]. Modern Computer (Popular Edition), 2007(9).

[4] Brilliant. New display technology: 265438+eyes of the 20th century [J]. Business Weekly, 2009 (1).