Talk:Raster scan

From Wikipedia, the free encyclopedia
Jump to: navigation, search

I really don't see how the main photo on this page has any relevance to raster scanning. Would someone elaborate, or rather find another image to use? —Preceding unsigned comment added by (talk) 01:58, 19 February 2010 (UTC)

Does anyone know if there are any names for the rastering directions? We have the 'scan lines', usually travelling horizontally, and being incremented vertically. But what if the scan lines are vertical? What are the directions called? The 'scan line direction' and the what?MrTribble 15:08, 16 November 2007 (UTC)

In TV and CRT displays, definitely horizontal and vertical. In most cases, scan lines are [called] horizontal, and directions are left-to-right, top-to bottom. Vertical scan lines were used in the (precision) CRT bearing indicator for naval fire-control radar, probably WW II and Korean War era (perhaps later). In general, the fast scan would be "line", and the slow, "frame", I'd say. As well, fast and slow [scan rates] would distinguish the two.

Purely for fun, no insults intended, I used to say that oscilloscopes in the Middle East scanned (swept) from right to left.

The USA's National Bureau of Standards (now NIST) experimented with an area scan (i.e., not a line scan, as in laser bar-code scanners), but with diagonal scan lines (!). Deflection waveforms were triangular, frequencies similar, but chosen to be as inharmonic as possible, so to speak, so they covered the whole area. I have forgotten why it didn't succeed; possibly hard to watch.

I really wanted to clear up the misconception, perhaps widespread, that in CRT raster displays, once a scan line is complete, there's a "jump". No way! No need, and totally unnecessary. I probably explained more CRT scan theory than necessary as a background for trying to clear up the misconception. At least, I moved it to the Theory section!

I'm guessing that the original author is Czech, and quite fluent in English; I changed his text just a little, and added some initial clarification. In signal-processing terms, I'd say that a camera "captures" an image.

I was careful not to change any of his remarkable historical notes; I stayed strictly away from them!

As to references and citations: I'm now close to closing out this incarnation :), have limited energy, too much else that really ought to be done, and preparing proper references would probably take weeks. An apology is not enough, but explaining might not be out of order. Best regards,Nikevich (talk) 08:39, 16 March 2009 (UTC)