![raster scan raster scan](https://image.slidesharecdn.com/lecture-rasterrandomscansystems-110726115809-phpapp02/95/lecture-rasterrandomscansystems-2-728.jpg)
Also, after reaching the end of a line, the beam has to return to the start of the next raster line.
![raster scan raster scan](https://image.slidesharecdn.com/rasterscandisplays-170213151554/95/raster-scan-displays-ppt-9-638.jpg)
![raster scan raster scan](http://image.slidesharecdn.com/rasterscanandrandomscan-100120060025-phpapp02/95/raster-scan-and-random-scan-1-728.jpg)
#RASTER SCAN FULL#
Most PC monitors redraw an entire screen full of raster lines 50 to 90 times per second.Īs Figure 3-1 shows, the electron beam scans an area larger than the actual view area of the display screen, but the electron beam is active only when the beam is in the viewable area. The phosphor fades in a while, but if the lines are redrawn repeatedly, our persistence of vision creates an illusion of a steady image. Thus, a line of the image is generated by controlling the intensity of the beam as it scans across the screen. The glowing dot on the screen represents a picture element, or pixel. The phosphor on the screen glows in proportion to the intensity of the electron beam. Raster line Figure 3-1: A Typical Raster-Scan Display. An electron beam in the monitor generates the raster lines by sweeping back and forth on a phosphor-coated screen, as illustrated in Figure 3-1. The image that appears on the monitor is made up of many horizontal lines, known as raster lines. More expensive laptops use active-matrix LCD-display screens. On laptop computers, the display screen is a liquid crystal display (LCD). The display screen is typically a phosphor-coated glass tube on which an electron beam traces the output image. The monitor is the physical device that contains the display screen where the graphic and text output appears. All video cards operate on the same principle: They store an image in video memory (also called video RAM or VRAM for short) and generate the appropriate signals to display the image on the monitor's screen.