Monitors and Projectors
Monitors and projectors are primary output devices for a computer. Figure 1-22 shows different types of monitors.
Figure 1-22 Types of Monitors
The most important difference between these monitor types is the technology used to create an image:
■ CRT: Cathode ray tube monitors are the most common monitor type. Red, green, and blue electron beams move back and forth across the phosphorous-coated screen. The phosphor glows when struck by the electron beam. Areas not struck by the electron beam do not glow. The combination of glowing and nonglowing areas is what creates the image on the screen. Most televisions also use this technology.
■ LCD: Liquid crystal display is commonly used in laptops and some projectors. It consists of two polarizing filters with a liquid crystal solution between them. An electronic current aligns the crystals so that light can either pass through or not pass through. The effect of light passing through in certain areas and not in others is what creates the image. LCD comes in two forms—active matrix and passive matrix. Active matrix is sometimes called thin film transistor (TFT). TFT allows each pixel to be controlled, which creates very sharp color images. Passive matrix is less expensive than active matrix but does not provide the same level of image control. LCD Monitors are becoming the most common type of computer monitor.
■ DLP: Digital light processing is another technology that is used in projectors. DLP projectors use a spinning color wheel with a microprocessor-controlled array of mirrors called a digital micromirror device (DMD). Each mirror corresponds to a specific pixel. Each mirror reflects light toward or away from the projector optics. This creates a monochromatic image of up to 1024 shades of gray between white and black. The color wheel then adds the color data to complete the projected color image.
Monitor resolution refers to the level of image detail that can be reproduced. Table 1-9 is a chart of common monitor resolutions.
|
Display Standard |
Linear Pixels (HXV) |
Aspect Ratio |
|
CGA |
320x200 |
16:10 |
|
EGA |
640x350 |
11:6 |
|
VGA |
640x480 |
4:3 |
|
WVGA |
854x480 |
16:9 |
|
SVGA |
800x600 |
4:3 |
|
XGA |
1024x768 |
4:3 |
|
WXGA |
1280x800 |
16:10 |
|
SXGA |
1280x1024 |
5:4 |
|
WSXGA |
1600x1024 |
25:16 |
|
UXGA |
1600x1200 |
4:3 |
|
HDTV |
1920x1080 |
16:9 |
|
WUXGA |
1920x1200 |
16:10 |
|
QXGA |
2048x1536 |
4:3 |
|
QSXGA |
2560x2048 |
5:4 |
|
WQUXGA |
3840x2400 |
16:10 |
Higher-resolution settings produce better image quality. Several factors are involved in monitor resolution:
■ Pixels. The term pixel is an abbreviation of picture element. Pixels are the tiny dots that comprise a screen. Each pixel consists of red, green, and blue.
■ Dot pitch . Dot pitch is the distance between pixels on the screen. A lower dot pitch number produces a better image.
■ Refresh rate. The refresh rate is how often per second the image is rebuilt. A higher refresh rate produces a better image and reduces the level of flicker.
■ Interlaced/noninterlaced. Interlaced monitors create the image by scanning the screen two times. The first scan covers the odd lines, top to bottom, and the second scan covers the even lines. Noninterlaced monitors create the image by scanning the screen one line at a time from top to bottom. Most CRT monitors today are noninterlaced.
■ Horizontal Vertical Colors (HVC) . The number of pixels in a line is the horizontal resolution. The number of lines in a screen is the vertical resolution. The number of colors that can be reproduced is the color resolution.
■ Aspect ratio. Aspect ratio is the horizontal-to-vertical measurement of the monitor's viewing area. For example, a 4.3 aspect ratio applies to a viewing area that is 16 inches wide by 12 inches high. A 4.3 aspect ratio also applies to a viewing area that is 24 inches wide by 18 inches high. A viewing area that is 22 inches wide by 12 inches high has an aspect ratio of 11.6.
Monitors have controls for adjusting the image quality. Here are some common monitor settings.
■ Brightness is the image's intensity.
■ Contrast is the ratio of light to dark.
■ Position is the vertical and horizontal location of the image on the screen.
■ Reset returns the monitor settings to the factory defaults.
Continue reading here: Interrupt Requests
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