Displaying or capturing a video image line by line. Computer monitors and TVs use this method whereby electrons are beamed (scanned) onto the phosphor coating on the screen a line at a time from left to right starting at the top-left corner. At the end of the line, the beam is turned off and moved back to the left and down one line, which is known as the "horizontal retrace." When the bottom-right corner is reached, the gun is returned to the top-left corner, known as the "vertical retrace." For TV signals, these "flyback" periods in which the electron beam is moved to a different line are also called the "horizontal" and "vertical blanking intervals."
Video Is the Reverse
Capturing video images uses the same raster scan sequence as the display, but in reverse. Instead of sending electrons to a material that creates light, light is directed to a material that holds a charge, and the charge is turned into an electronic signal. The first video cameras used a vacuum tube with a light-sensitive plate at one end. Subsequently, CCD and CMOS chips replaced the tube. See CRT, CCD and rasterize.
Raster Scan Tracing
Starting at the top-left of the screen and going to the bottom-right, the electron beam is turned on a line at a time (1), then turned off to go back to the next line (2), then off once again to go back up to the top (3).
Video Is the Reverse
Capturing video images uses the same raster scan sequence as the display, but in reverse. Instead of sending electrons to a material that creates light, light is directed to a material that holds a charge, and the charge is turned into an electronic signal. The first video cameras used a vacuum tube with a light-sensitive plate at one end. Subsequently, CCD and CMOS chips replaced the tube. See CRT, CCD and rasterize.
Raster Scan Tracing
Starting at the top-left of the screen and going to the bottom-right, the electron beam is turned on a line at a time (1), then turned off to go back to the next line (2), then off once again to go back up to the top (3).
 | Reproduced with permission from Computer Desktop Encyclopedia. Copyright (c) 1981-2009 The Computer Language Company Inc. All rights reserved. |
Additional Resources
- RasterStitch 2.31 (Windows)
- RasterStitch is a utility for putting together multiple raster images stitching. Use this program to create a panorama of several photographs or scan and join fragments of a paper document, which dimensions exceed the scanner workspace. Version 2.31 has improved compatibility with MS Windows Vista.
- Software downloads 2009-05-22
- Raster to Vector 9.0 (Windows)
- Raster to Vector converts scanned drawings, maps and raster images (such as BMP, JPG, TIF, GIF, etc) into vector formats (such as HPGL, DXF, EMF, etc). You can scan old plans, archive drawings, or even photos and convert them into useful CAD data.
- Software downloads 2008-03-12
- Before buying an HD display, read this lowdown on 720p vs. 1080i vs 1080p
- Before buying an HD display, read this lowdown on 720p vs. 1080i vs 1080pSecond Rule: Beware the Ringers[B]Speaking of shopping in superstores for these bad boys, one thing I've learned is that you don't want to eyeball the image quality of these displays in a typical showroom setting where florescent...
- Discussion threads 2007-12-10
- Eroiica API 4.6 (Windows)
- Integrated with EDM/PDM/PLM/ERP/CRM/Workflow via its rich API, Eroiica facilitates fast and accurate image scanning, vectorizing, editing, cleanup, manipulation, enhancement, redlining, annotating, and converting of engineering size CAD & raster formats. Functionality: aIntegrate imaging with existing applications using Eroiica API;bImage-enable any document management, PDM or workflow applications system quickly and effectively;...
- Software downloads 2005-07-04
- IconEmpire 2.0 (Windows)
- IconEmpire gives professional and amateur artists the ability to design and edit all the graphics required in the software development cycle, including icons, static and animated cursors, and other interface elements. All these graphics can now be designed using a single application. IconEmpire offers a variety of features that cannot...
- Software downloads 2005-05-28
- Proof Block 12.0 (Mac)
- Proof Block is a plug-in filter for Adobe Illustrator that creates a proof block for routing illustrations to editors and art directors prior to publication. It creates it on its own layer that prints from Illustrator, when you print your proof, but not from page layout applications when placed as...
- Software downloads 2005-05-06
- Proof Block 10.0 (Mac)
- Proof Block is a plug-in filter for Adobe Illustrator that creates a proof block for routing illustrations to editors and art directors prior to publication. It creates it on its own layer that prints from Illustrator, when you print your proof, but not from page layout applications when placed as...
- Software downloads 2001-12-10
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