Talking about Digital Imaging (II) Display

Digital image processing cannot be done without a monitor. Here to talk about the monitor not only refers to the computer monitor, its definition also includes televisions, projection monitors, liquid crystal displays, plasma displays and so on. TVs can also output digital images, not necessarily computer monitors. Both the liquid crystal display and the plasma display are ultra-thin displays, and the appearance is not different, but the principle is completely different. Because of the limitation of the format, the author only talks about electron tube displays (such as traditional televisions and computer monitors), projection displays (which can be found in large electrical appliance stores), and liquid crystal displays. Plasma display information can be found on the NEC agent or NEC website. . Figure 1: The display is a bridge between information and human contact. It cannot be done without it. Courtesy Barco Graphics Cathode Ray Tube
This technology is used in general televisions and computer displays. CRTs have low production costs and are the most popular displays today, but they may be replaced by other ultra-thin displays in the future. The CRT is much larger than the other two displays. See Figure 2. Two popular CRT designs are the Shadow Mask and the Aperture Grill. Both have their own advantages, when the performance of black, the former has a better effect; when the performance of the horizontal line, the latter has a better output; both of the pixel size is similar, the former consists of small dots of pixels, the latter by the small The square points make up the pixels, both providing a similar resolution. Generally speaking, traditional TV sets have only 400,000 pixels of optical resolution, but the most common computer monitors also have 500,000 pixels, and some of them have more than 1 million pixels, and even a 2 million-pixel computer monitor is not special. The resolution of the monitor is determined by the point size and dot pitch. Figure 2: The Mitsubishi electron tube monitor uses a vertical stand screen design. The television is much larger than the computer monitor, so use a magnifying glass to observe their differences. Figure 叁: The left side is a backlit mask technology. Behind the screen is a black metal mask with small round holes that can control the exact position of the light beam to shoot the correct position of the screen and provide the ideal black effect. On the right is the vertical support technology without a black mask. The black stand controls the light spot and produces a black effect. Liquid Crystal Display
It is the slimmer design among the best, taking up very little space, but the production of LCD screens is very expensive. Seat-mounted LCD monitors are only two inches thick, LCD screens used in laptop computers are less than half an inch, and even more than 40 inches are only four inches thick. LCD monitors have become more and more popular and prices have continued to decline. In addition to being a computer monitor, it has also been used in mobile camcorders, digital cameras, even ultra-thin TVs and recently introduced LCD electronic photo frames. Hong Kong’s new airport also installed a giant LCD display board to keep pace with the times. The LCD is a semi-liquid, semi-solid material (eg, ferroelectric) sandwiched between upper and lower transparent voltage plates. The voltage controls the direction of alignment of the liquid crystals to control the light transmittance, ie, to generate images. Figure 4: Schematic diagram of the liquid crystal display control light. Figure 5: Large LCD TVs sold in a large electrical shop in Hong Kong. Figure 6: Apple G3 computer with a new design of the LCD display. Projection Monitor/TV
The projection display, also called back projection display, is the same technical principle as the liquid crystal projector. It also uses the light source and optical components to project the image on the high resolution liquid crystal display in the projector onto the large screen. Although the quality is lower than that of LCD monitors, it is only five times the price of LCD monitors. A 42-inch LCD monitor is now about HK$120,000, while a projection monitor of the same size only costs about HK$25,000. The resolution of a typical projection monitor is 800,000 pixels, which is twice the resolution of a conventional TV. Projection monitors can be used in home theaters, exhibitions, or online conferences. Although projection TVs or LCD TVs can output high-resolution images, Hong Kong has no high resolution broadcasting (HDTV, which has been implemented in Japan) or digital broadcasting (DTV, which has been implemented in many countries, such as the United States, Canada, Europe, Taiwan and India. And so on, and Japan will start tomorrow), the local broadcast with analog signals, the screen is only about 400,000 pixels, so high-resolution TV will only get 400,000 pixel image quality when used locally. Figure 8: High-resolution projection system - (1) High-brightness projection tube; (2) High-quality optical lens system; (3) High resolution LCD panel and (4) Defective width lens project the image on the TV screen. Table 1: Simple Comparison of Three Displays reference
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