Raster - Revision history

Jnc: Recast to make less CRT-specific

2021-09-20T13:41:21Z

Recast to make less CRT-specific

Jnc: +cat

2018-12-13T15:18:33Z

+cat

Jnc: typo

2018-10-07T21:17:41Z

typo

Jnc: Laser printers do it too

2018-10-07T21:12:47Z

Laser printers do it too

Jnc: A good start

2018-09-16T16:26:16Z

A good start

New page

A '''raster''' [[display]] is one which uses, or takes as an input [[signal]], a scan across the screen (usually a [[cathode ray tube|CRT]]) consisting of multiple horizontal lines (the rasters), laid down from the top to the bottom of the screen, with a short, constant vertical distance between them.

After scanning across the screen on one raster, the beam must then return to the other edge where it started, during which nothing is shown on the display (it is said to be 'blanked'); this is known as the 'horizontal retrace'. Likewise, when it gets to the bottom of the screen, it must return to the top, which is called the 'vertical retrace'.

This technique for covering the screen was first used in televisions, and was later adopted by [[video terminal]]s and other [[video display]]s.

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-A '''raster''' [[display]] is one which uses, or takes as an input [[signal]], a scan across the screen (usually a [[cathode ray tube|CRT]]) consisting of multiple horizontal lines (the rasters), laid down from the top to the bottom of the screen, with a short, constant vertical distance between them.
+A '''raster''' [[display]] is one which produces a rectangular array of parallel, closely-spaced lines of output (the rasters). It takes as its input [[signal]] a scan across the screen in precisely the form needed to produce that output in real time, i.e. it consists of a sequence of horizontal line segments, arranged from the top to the bottom of the display (with a short, constant vertical distance between them).
-After scanning across the screen on one raster, the beam must then return to the other edge where it started, during which nothing is shown on the display (it is said to be 'blanked'); this is known as the 'horizontal retrace'. Likewise, when it gets to the bottom of the screen, it must return to the top, which is called the 'vertical retrace'.
+After scanning across the display on one raster, the means for producing the display of each line segment must then return to the other edge where it started, during which time nothing is shown on the display (it is said to be 'blanked'); this is known as the 'horizontal retrace interval'. Likewise, when it gets to the bottom of the display, it must return to the top, which is called the 'vertical retrace'.
-This technique for covering the screen was first used in televisions, and was later adopted by [[video terminal]]s and other [[video display]]s. A similar technique is used by [[laser printer]]s.
+This technique for displaying an image was first used in televisions using [[cathode ray tube|CRTs]], where the [[electron]] beam was scanned across the screen which formed the front face of the CRT, with the input signal being instantaneously used to control the intensity (i.e. brightness) of the beam as it scanned. This method was later adopted by [[video terminal]]s and other [[video display]]s; a similar technique is used by [[laser printer]]s. The general form of the interface (a series of line segments) is used in other display technologies.
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-[[Category: Device Basics‎‎]]
+[[Category: Device Basics]]

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 After scanning across the screen on one raster, the beam must then return to the other edge where it started, during which nothing is shown on the display (it is said to be 'blanked'); this is known as the 'horizontal retrace'. Likewise, when it gets to the bottom of the screen, it must return to the top, which is called the 'vertical retrace'.
-This technique for covering the screen was first used in televisions, and was later adopted by [[video terminal]]s and other [[video display]]s. A similar technique is used by [[laser print]]s.
+This technique for covering the screen was first used in televisions, and was later adopted by [[video terminal]]s and other [[video display]]s. A similar technique is used by [[laser printer]]s.
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