Let Horizontal sweep = 15.75Khz Let Vertical sweep = 60 hz Num lines = horizontal/vertical = 15750/60 = 262.5 These numbers are for standard North America broadcast television Half line allows next field (next lines) to be offset by one half line (even & old fields). 7-bit converters can display 2M colors (128x128x128) 8-bit converters can display 16M colors (256x256x256) Infinite number of colors available (generally, finite # are generated – 256K, 16M, 24M) Typically a DAC (digital-to-analog converter used) – 6-bit DAC for each video signal to generate 64 different voltage levels between 0V and 0.7V (64 red, 64 green, 64 blue = 256k different colors available) 15-pin connector (red,green,blue, red gnd, green gnd, blue gnd, horizontal retrace, vertical retrace, pin 9 blocked,color detect, monochrome detect) Speed of DAC is critical – most displays require an operating conversion time of 25ns to 40ns max. Sweep down the screen, (drives vertical deflector) Vertical Retrace moves beam back to top left cornerĨ Color Monitors (cont) Analog RGB Monitor Analog signals (0-0.7v) The vertical sweep controls how fast each screen is displayed. Sweep across screen (slow), drives horizontal deflector Horizontal Retrace (fast), moves beam back to left edge of screen. 26 average – higher numbers >more distance Horizontal and vertical frequencies – the speed at which horizontal lines are drawn and the time it takes to draw all lines on the screen.ħ The horizontal sweep controls the number of lines on the screen Horizontal oscillator Horizontal amplifier 15.75 Khz CRT Vertical Sync Vertical oscillator Vertical amplifier 60 hz Video amplifier Video InputĦ Video Monitor Clarity determined by several factors:ĭot pitch – distance between adjacent pixels. Active lines Retrace linesĤ Raster line – horizontal line of video information that is displayed on screenĦ40x480 display has 480 raster lines, 640 pixels per line.

Horizontal retrace is when beam returns to left edge Vertical retrace is when beam returns to upper left corner.

Non-interlaced – has less flickerĢ Cathode Ray Tubes Most common display type Phosper Vertical Deflectionģ Raster Scan Beam directed in lines (scan lines) across screen.ĭots are created by turning the beam on & off. After the last row is drawn, the gun turns off and moves to the upper left corner of the screen to start all over again (vertical retrace) Interlaced monitor scans every other line until it reaches the bottom, returns to the top and scans all other lines. Horizontal retrace – the time period when the gun is off between rows. Starting at the top of the screen, the gun fires electrons from the left side to the right in a horizontal row, briefly shuts off, and returns to the left side of the screen to begin a new row. 1 Video Monitor Uses raster scanning to display imagesīeam of electrons illuminates phosphorus dots on the screen called pixels.

Do lcd screens raster scan