Chapter 4 ( Display devices) Flashcards
VDU
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Short for Visual Display Unit, VDU is an old term used to describe any device used with computers to convert the computer signals into text and pictures and display them. For example, a flat panel display, and a projector are both examples of VDUs. However, VDU is most commonly used to describe the now archaic standard CRT monitor.
understanding display
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computer sends signal to the video adapter or the video expansion card that is installed in the computer motherboard in an expansion slot on the past they used AGP, PCI slots but now they are using PCIe slots.
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VDU types
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CRT LCD LED OLED projection systems
CRT
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Short for Cathode-Ray Tube, CRT is the electron beams
Within the CRT are three electron guns, red, green, and blue. Each of these guns streams a steady flow of electrons, left to right, for each line of your monitor. As the electrons hit the phosphors on the CRT, the phosphor will glow certain intensities. As a new line begins, the guns will then begin at the left and continue right; these guns will repeat this process sometimes thousands of times until the screen has been completely drawn line by line. Once the phosphors on the CRT have been hit with an electron they only glow for a short period of time; because of this, the CRT must be refreshed, which means the process will be repeated as explained above. If the video card’s refresh rate is not set high enough, you may encounter a flicker or a noticeable steady line scrolling from the top to the bottom of your screen.
two ways to measure a CRT monitor’s image.
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Dot pitch: A Dot pitch is the distance between pixels on a computer display screen measured in millimeters.
Resolution: is measured by the number of horizontal Dots by vertically Dots.
LCD: liquid crystal display
analog and digital
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Short for Liquid-Crystal Display, LCD is a flat display technology used in laptops, cell phones, calculators, digital cameras, and flat screen displays. The LCD is made of two sheets of a flexible polarizing material and a layer of liquid crystal solution between the two. An LCD is available as an active matrix, dual-scan, or passive-matrix display and are most common with laptop computers, like the Dell laptop computer shown in the picture.
TWO major types of LCD
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Active matrix screens
passive matrix screens
and there is Dual scan
Active matrix
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Thin Film Transistor (TFT) and Active-matrix LCD (AMLCD), an active matrix display is a liquid crystal display (LCD) first introduced with the IBM ThinkPad in 1992. With active matrix displays, each pixel is controlled by one to four transistors which can make the screen brighter and more colorful than passive-matrix displays. Active-matrix displays also update the screen faster than passive-matrix, and are capable of being viewed at a greater viewing angles. Because of this improved technology, active matrix screens are often more expensive than their passive matrix counterparts.
Passive matrix
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A passive matrix display is an LCD screen display that contains a series of wires that criss-cross each other.
Dual scan.
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A type of passive-matrix LCD display that provides faster refresh rates that conventional passive-matrix displays by dividing the screen into two sections that are refreshed simultaneously. Dual-scan displays are not as sharp or bright as active-matrix displays, but they consume less power.
LED: short for Light Emitting Diode
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An LED monitor (short for Light Emitting Diode) or LED display is a flat screen, flat panel computer monitor or television. It has a very short depth and is light in terms of weight. The actual difference between this and a typical LCD monitor is the backlighting. The first LCD monitors used CCFL instead of LEDs to illuminate the screen.
Plasma Display
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the word Plasma refers to a cloud of ionized particles , Atoms and molecules with electrons in an unstable state, this electron imbalance is used to create light from the change in energy levels as they achieve balance
OLED: Organic Light-Emitting Diode.
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Organic Light-Emitting Diode, OLED is an LED that is used in flat-panel displays, is much thinner than LCD, and requires less power to run.
a self-luminous diode (it glows when an electrical field is applied to the electrodes) that does not require backlighting or diffusers.
Projection system
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a projector is an output device that can take images generated by a computer and reproduce them on a large, flat surface. For example, projectors are used in meetings to help ensure that all participants can view the information being presented.
Rear projection.
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The projector is built into a cabinet behind a screen onto whish the image is projected in reverse so that an observer in front of a TV can view the image correctly.
Brightness.
Dot pitch
the lux
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brightness is measured in Lumens. A Lumen (lm) is a unit of measurement for the total amount of visible light that the projector gives off. Dot pitch (sometimes called line pitch, stripe pitch, or phosphor pitch) is a specification for a computer display, computer printer, image scanner, or other pixel-based device that describes the distance, for example, between dots (sub-pixels) on a display screen.
The lux ; when the rated brightness of the projector in lumens is focused on a large aria the lux measuring how much the projector light up the surface on which it is focused. The lux is the measurement of light output; more specifically, one lux is equal to one lumen per square meter. The symbol for lux is lx
Cooling down
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never pull the electrical plug from the outlet until the internal fan stop running. because there is a lot of heat generated by the projector bulb that damage the electrons or the bulb itself.
Adjusting Display settings
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sometimes we have to do manually changing display setting, such as for new monitor or graphics adapter support.
Refresh rate
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is a CRT monitor measurement in Hz that indicates how many times per second a monitor screen image is renewed. For example, a monitor with a refresh rate to 75 Hz means the screen is going to redraw 75 times per second.
the refresh rate we select must be supported by both the graphics adapter and the monitor because the adapter drives the monitor. if the monitor support only one refreshing rate it does not matter how many different rate your adapter supports.
Resolution
native resolution?
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is measured by the number of horizontal Dots by vertically Dots.
When resolution increases, images become more crisp due to a higher pixel density.
Resolution increases when the number is small.
Multiple Displays
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is the use of two monitors on one computer.
Microsoft call its multimonitor feature dual view.
Degauss
we do it to get the screen cleared up and we can have a new image in it
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is the reduction of the magnetic field of an object. it is generally impossible to completely neutralize an object magnetic field so reducing it is the objective.
degaussing a monitor is strictly a CRT related.
Video standard
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The video standards is an ability of a video card or video display device that defines the amount of colors that are shown and the resolution. For example, VGA is capable of a maximum of 640 x 480 (16 colors) in Graphics Mode.
Display adapter can divided in five
Monochrome CGA EGA VGA DVI, HDMI, and other modern digital video.
Monochrome
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Term used to describe a visual display or output in one color. For example, a monochrome monitor displays only one color, such as green on a black background.
The firs adapter was MDA
MDA
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Short for Monochrome Display Adapter, MDA is the first text-only video display( it could display text but not graphics and used a resolution of 720x350) standard from IBM capable of displaying at a maximum of 80x25 characters in two colors. Today, MDA is no longer used.
CGA
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Color graphic adapter
It display 16 color text in resolution of 320x200 (40 columns) and 640x200 ( 80 columns)
EGA
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people want more color and high resolution so MBA came up with EGA the enhanced graphics adapter.
EGA could display 16 color out of a platter of 64 as well as a resolution of 640x350 mode.
VGA
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video graphic Arry
Advanced video resolutions and concepts
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restore
Alternatively referred to as a system restore, restore is a term used to describe the process of reverting a computer back to its original configuration or an earlier copy. See our factory settings definition for full information and related links.
