Video 10 1 Section Objectives After completing this section you will be able to Describe the components of the video subsystem Differentiate among monitor types including laptop displays Define basic monitor theory and terminology Describe issues regarding video memory Install a video adapter and associated software 10 2 Video Overview Video should be considered a subsystem that consists of the monitor the electronic circuits which send the monitor instructions the connecting cable 10 3 Video Overview Video subsystem Video Figure 10 1 10 4 Types of Monitors Different ways of classifying monitors Color or Non color Analog or Digital Type of video adapter used 10 5 Types of Monitors Monochrome First type to be produced Project a single color white amber or green on black background Text only output no graphics Grayscale Display varying shades of black and white Used by artists and CAD designers Color Display up to millions of colors for text and graphics 10 6 Types of Monitors Digital Accept digital signals from the video adapter First monochrome and first two types of color monitors Limited number of colors Analog Utilize analog waveforms to generate colors Color variations are limitless Note Video adapter must match the type of monitor 10 7 Types of Monitors Video adapters monitor types Video Table 10 1 10 8 Monitor Terminology and Theory Monitor size No industry standard but traditionally defined as the diagonal length of the picture tube or CRT Most common sizes are 15 inch 17 inch and 21 inch CRT Cathode Ray Tube Main part of the monitor Covered by the monitor case which may not allow all of it to be viewed VIS Viewable Image Size Listed by many manufacturers as the viewable area of the CRT to clarify the monitor size 10 9 Monitor Terminology and Theory Electron gun Directs a beam of electrons at a phosphorous dot on the back of the monitor tube Some monitors have 3 one each for the colors red green and blue Other monitors utilize only 1 to direct the 3 color beams When the beam hits the phosphor the dot glows on the front of the screen All figures icons and letters are made up of these glowing dots Dot triad or dot trio 3 phosphorous dots grouped together at each location on the screen Consists of 1 dot each for red green and blue Electron beam hits the dot s with varying intensity causing the phosphor to glow and create different color intensities 10 10 Monitor Terminology and Theory Shadow mask A metal plate with holes that keeps the electron beam directed or focused at the proper dot Pixel short for picture element One dot on the screen created by the convergence of the phosphorous dot trio Smallest displayable unit on the monitor screen 10 11 Monitor Terminology and Theory Video theory of operation Video Figure 10 2 10 12 Monitor Terminology and Theory Picture cell The single image created by 3 different colored phosphorous dots Dot pitch The distance between like colored phosphorous dots on adjacent dot triads Measured in millimeters Commonly include 39mm 35mm 28mm 26mm 25mm The lower the monitor s dot pitch the smaller the distance between the dot triads The lower the number the better the picture quality 10 13 Monitor Terminology and Theory Dot pitch Video Figure 10 3 10 14 Monitor Terminology and Theory Aperture grill Used in monitors and televisions as an alternative method to the shadow mask using very fine vertical wires instead of holes Allows more electrons to reach the screen producing deeper color intensities Requires horizontal stabilizing wires to keep the fine vertical wires from vibrating or moving and these can be viewed on bright images Minimum acceptable dot pitch for the aperture grill is 25mm Some dot pitch descriptions include Grill pitch horizontal mask pitch and mask pitch 10 15 Monitor Terminology and Theory Aperture grille Video Figure 10 4 10 16 Monitor Terminology and Theory Resolution The maximum number of pixels of a monitor Illustrated by two values separated by an x meaning by Example of a monitor resolution is 640 x 480 640 of pixels that fit horizontally 480 of pixels that fit vertically Depends on the combination of the monitor and adapter 10 17 Monitor Terminology and Theory Refresh Rate The maximum number of times a screen is scanned or redrawn in one second measured in Hz Horizontal scanning frequency HRR or Horizontal Refresh Rate The speed which the beam traverses the screen and draws one line Measure in kilohertz kHz as determined by the video adapter Range from 35 to 90 kHz 10 18 Monitor Terminology and Theory Vertical scan rate VRR or Vertical Refresh Rate The number of times the electron beam draws from the top left corner to the bottom right corner and back again to the top left drawing the entire screen Determined by the capabilities of the video adapter and the monitor Multi scan monitor also multi synch or multiple frequency Can lock onto different vertical and horizontal scanning rates Interlacing A monitor that uses interlacing scans first odd numbered pixel rows then returns for the even ones on each vertical refresh Causes a flickering screen but is less expensive than non interlaced which scans all horizontal rows on each vertical refresh 10 19 LCD Liquid Crystal Display LCD Liquid Crystal Display A video technology used with laptops and flat screen monitors The two types of LCD are passive matrix and active matrix Passive matrix least expensive Made up of rows and columns of conductors with the pixels located at each intersection Each pixel has 3 cells in a color monitor one each for red green and blue Not as bright as active matrix displays 10 20 LCD Liquid Crystal Display Active matrix more expensive Have a transistor for each pixel Number of transistors determine maximum resolution Also known as TFT Thin Film Transistor which use three transistors per pixel one for each color Brighter than passive matrix Flat panel Monitors for desktop computers that use LCD technology Viewing area the same as the LCD measurements Take up less desktop space and use less power than CRTs 10 21 LCD Liquid Crystal Display Flat panel versus regular sized monitor Video Figure 10 5 10 22 Video Ports DVI Digital Video Visual Interface Interface used on an AGP PCI E adapter with the better flat panel monitors DVI port is a 24 pin connector Single link connection Allows video resolution up to 1920x1080 Dual link connection The use of more pins sends more single allowing for higher resolution DVI D Type of DVI used for digital connectivity