Color CRT monitor
CRT monitors use a combination of fluorescence layers that emit different colors of light to display color graphics. Emitting light groups of different fluorescence layersTogether , you can create a visible color that depends on its proportions. one way to display color graphics is to paint a different layer of phosphor on the screen. Emitted by the electron beam in the fluorescence layerpenetration depth decision. This method is called the
electron beam penetrating method (beam-penetration), it commonly uses the Yu Hong, the green two layers structure. SpeedThe slow electron beam activates the outer red layer only, and the fast electron beam can pass through the red layer and activate the green layer inside. The medium-speed electron beam generates two additional colors by emitting a combination of red and green light: orange and yellow. The speed of the electron, which is the color of any point on the screen, is controlled by the accelerating voltage of the electron beam. Electron beam penetration is a cheap way for random scan monitors to generate color graphics, but there may be fewer color types,and the graphics quality is not as good as other methods.
Shadow Mask Method (Shadow-mask) is commonly used in raster scanning systems (including color TVs) because it produces a much larger color range than electron beam penetration. This approach is based on the familiar principle of combining colors from red, green, and Blue , called the RGB color model . For each pixel location, the shadow mask CRT has three fluorescent color dots: one fluorescence point emits red light, the other emits a green glow, and the third emits Blu-ray. The CRT has three electronic guns, corresponding to each color point one by one, while the shade Grille is located immediately after the screen coated with a fluorescent layer. Because the human eye can combine the light emitted by three points into a combination color. Therefore, three kinds of fluorescent powder emit a small color point of light generated by the pixel position. Figure 2.10 shows a Delta-delta shadow mask method commonly used in color CRT systems. The three electron beams are deflected, focused, and emitted onto the shadow mask. The shadow mask has a series of holes that are distributed according to the fluorescence point pattern. When three electron beams pass through a hole in the shadow mask, a dot triangle is activated to display a small color highlight on the screen. When the fluorescent dots are arranged in a triangular shape and each electron beam passes through the shade mask, only the colored dots corresponding to them are activated. The other configuration of the three electronic guns is arranged by line (In-line). Of these, three electronic guns and corresponding red-green-blue color dots on the screen are arranged along a scan line rather than in a triangular pattern. This type of electronic gun is easily aligned by line arrangement, usually for high resolution color CRT.
Changing the intensity level of the three electron beams can change the color of the shadow mask CRT display . Turn off two of the three guns, and we'll justYou can get the color (red, green, blue) from a single activated fluorescence point. When activating three o'clock with the same electron beam intensity, we will look atto White. Yellow is produced by the same intensity of green and red dots, and the magenta is produced by the same intensity of blue and red dots. And when the blue dot and the green dotwill appear cyan when the level of activation is the same. In some low-price systems, the electron beam can only be turned on or off, so it can only display eightcolor. A higher-level system can set an intermediate intensity level for the electron beam, allowing millions of different colors to be generated.
The color graphics system can be designed according to a variety of CRT display devices. Some cheap home computer systems and TVs.game consoles are designed to be equipped with
color televisions and
RF (radio-frequency, radio frequency) modulators. The role of the RF modulatoris the signal of the analog broadcasting station. This means that the color and luminance information of the graphic must be combined and superimposed to the broadcast frequency carrier signalcome up as the loser of the TV. The circuit in the TV then receives the signal from the RF modulator, extracts the graphic information, anddisplayed on the screen. As we can expect, due to the additional processing of the graphics information from the RF modulator and the TV circuit, it willreduce the quality of the image display.
Synthetic monitors (composite monitor) are TV adapter devices used to allow broadcast circuit bypass. These display devicesThe combination of graphical information is still required, but the carrier signal is not required. It combines the graphic information into a synthetic signal, which is then separated by the monitor,the quality of the graphics is still not too good:.
The color CRT of the graphic system is designed as an
RGB monitor , which uses the shadow mask method and does notThe intensity level of each electron gun (red, green and blue) is obtained directly from the computer system through any intermediate processing. In high-quality gratingin the frame cache of the graphics system, each pixel corresponds to 24 bits, each electronic gun allows a 256-stage voltage setting, so that each pixel has nearlyAvailable in 17 million different colors. RGB color systems with 24 storage bits per pixel are often referred to as
full-color Systems (Full-colorsystem) or
True Color systems (True-color).
Computer graphics (i) video display equipment _4_ color CRT monitor
