Difference b/w LCD and CRT
Usual disclaimers apply!
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CRT fitted to B747-400
heavy (ish!), large, as in depth! and require 115v 400hz for power.
LCD fitted to B777
light, only 8.5 inches deep, use 28v for power.
The LCD is the newer technology, and is an advance on the original designs as they have a very wide viewing angle with no loss of definition or illumination.
heavy (ish!), large, as in depth! and require 115v 400hz for power.
LCD fitted to B777
light, only 8.5 inches deep, use 28v for power.
The LCD is the newer technology, and is an advance on the original designs as they have a very wide viewing angle with no loss of definition or illumination.
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Easy really
CRT = TV sets, Normal Computer monitors etc. Thermionic technology, heat, degenerate with time and use etc.
LCD = solid state technology, cool, theoretically does not degenerate with time althoughsome etching does occur.
NG 737 and 777 use LCD not sure about 747-400 busses and earlier Boeings CRT
CRT = TV sets, Normal Computer monitors etc. Thermionic technology, heat, degenerate with time and use etc.
LCD = solid state technology, cool, theoretically does not degenerate with time althoughsome etching does occur.
NG 737 and 777 use LCD not sure about 747-400 busses and earlier Boeings CRT
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Other differences include lower price, better resolution, faster refresh rate, and less image latency available with CRTs, though LCDs are catching up in these regards. Also, none of these is especially important in cockpit displays, because the LCDs are "fast enough."
OTOH, LCDs don't have the [perceived] radiation hazard of CRTs.
I think the bottom line is that LCDs will take over for CRTs wherever practicable, since their performance is constantly improving and their cost decreasing.
OTOH, LCDs don't have the [perceived] radiation hazard of CRTs.
I think the bottom line is that LCDs will take over for CRTs wherever practicable, since their performance is constantly improving and their cost decreasing.
During World War Two, most of the patents for the Cathode Ray Tube (CRT) display system were held by US companies, like RCA. The military application at the time was for radar displays.
The British wanted a display technology under diferent control, and funded development, which eventually lead to the Liquid Crystal Display (LCD).
How it works: Light travels as two waves, an electrical wave, supported by a magnetic wave at 90°, and as such has an orientation. A polarised filter only allows one orientation of the wave to be transmitted. If you set up one piece of vertically poloarised glass, then only vertically polarised light is transmitted, place a second piece of horizontally polarised glass in line, and no light will be able to pass through both sheets of glass.
A liquid crystal is a subtance that exists as a liquid, but has long electrically charged, molecules that tend to line up with each other (due to the electrical charge on the molecule), causing a crystaline efect. Crystals can redirect light.
So if you fill the space between the two sheets of polarised glass with a liquid crystal, then apply an electric charge between them, you can line up the crystals in such a way as to rotate the polarised light by 90°. The places between the glass with the electric charge will transmit light through the two polarised filters, the places without charge will not. All of the light that is transmitted leaves the display polarised. That is how an LCD works.
Now if you put another polarised filter in front of your eyes - i.e. polarised sunnies, the sunnies will block the light leaving the display if the sunnies' filter doesn't match the polarisation of the display.
Ploarised sunnies' chief attribute is that they will completely eliminate glare coming from a flat surface that is of an angle of approximately 53%. They are designed mainly to cut glare from water. A pilot wearing Polaroid lenses sees the world as constantly changing, according to his (or her) angle of bank, as the angle of the glare is altered. They aren't suitable for aviation.
The British wanted a display technology under diferent control, and funded development, which eventually lead to the Liquid Crystal Display (LCD).
How it works: Light travels as two waves, an electrical wave, supported by a magnetic wave at 90°, and as such has an orientation. A polarised filter only allows one orientation of the wave to be transmitted. If you set up one piece of vertically poloarised glass, then only vertically polarised light is transmitted, place a second piece of horizontally polarised glass in line, and no light will be able to pass through both sheets of glass.
A liquid crystal is a subtance that exists as a liquid, but has long electrically charged, molecules that tend to line up with each other (due to the electrical charge on the molecule), causing a crystaline efect. Crystals can redirect light.
So if you fill the space between the two sheets of polarised glass with a liquid crystal, then apply an electric charge between them, you can line up the crystals in such a way as to rotate the polarised light by 90°. The places between the glass with the electric charge will transmit light through the two polarised filters, the places without charge will not. All of the light that is transmitted leaves the display polarised. That is how an LCD works.
Now if you put another polarised filter in front of your eyes - i.e. polarised sunnies, the sunnies will block the light leaving the display if the sunnies' filter doesn't match the polarisation of the display.
Ploarised sunnies' chief attribute is that they will completely eliminate glare coming from a flat surface that is of an angle of approximately 53%. They are designed mainly to cut glare from water. A pilot wearing Polaroid lenses sees the world as constantly changing, according to his (or her) angle of bank, as the angle of the glare is altered. They aren't suitable for aviation.
Last edited by Checkboard; 18th Apr 2002 at 07:01.
Dutch Roller
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Generally the LCD-screens make you somehow less tired, especially on longer flights. I believe this has to do with the higher refesh rates found on LCD. They are much "easier" on the eyes.
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In fact the "refresh rate" doesn't really apply for TFT LCDs as they're persistent - the problem with them is getting them to change in a timely fashion: a 40Hz refresh rate (i.e. images/second) is about as good as consumer models can manage.
Typical... my maiden Pprune post and it's about bloody computers... :o
m.
Typical... my maiden Pprune post and it's about bloody computers... :o
m.
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I don't know what the refresh rate of LCD cockpit displays is, but consumer displays (e.g., laptop computers) are normally 60 Hz. By contrast, good CRT computer monitors run at 85 Hz.
"Persistence" is a problem with LCDs where rapid change is required. For example, in a fast-moving video game, the scene may "blur" as previous images fade from the display more slowly than the every-cycle refresh of the CRT. I don't think this is a real problem for cockpit displays, though, because the required rate of change of information on the display is slower.
"Persistence" is a problem with LCDs where rapid change is required. For example, in a fast-moving video game, the scene may "blur" as previous images fade from the display more slowly than the every-cycle refresh of the CRT. I don't think this is a real problem for cockpit displays, though, because the required rate of change of information on the display is slower.
