raster laser?

[Steve Stutman]

Hi,


High BW laser deflection is often done with "Bragg cells". They are 
acousto-optic.

You input signals at NN Mc. and the cell essentially changes its 
refractive index. As beam shines through, it is deflected.

Not inexpensive. When you design a display for human use, psychopyhsics 
very important.

You need to think about energy/unit time, deflection, persistence, 
retinal sensitivity, etc.

Many clever people spent their lives working on phosphors.

Sooner or later you get back to Farnsworth and Logie-Baird equivalents.

Back when much of the stuff on this list was new, there was a project 
involving  30 Mc. BW laser deflection for writing directly on wafer.

Not sure of current speeds, BW, but bound to be faster.

BR,


Steve





ionder Mouse wrote:

>>Somehow I got subscribed to an optics catalog.  This got me to
>>thinking.  How hard would it be to cause a laser beam to sweep with
>>the speed and accuracy to be a substitute for a CRT?
>>    
>>
>
>Quite easy.  Barcode scanners do it regularly in one dimension; you
>just need to add another, much slower, scan in the other dimension....
>
>How hard would it be to do it affordably, safely, etc?  That's another
>question.  Note that horizontal scan frequences in the high tens of KHz
>are common; you'll have to be scanning something like that fast on the
>"fast" axis.  Given (say) a 20-faced mirror spinner (which might be
>good enough, though it might prove not linear enough), a scan rate of
>80KHz (what the display I'm using right now is doing) means this
>thing's RPM would be 80,000 (scans/sec) * 60 (sec/min) / 20 (scans/rev)
>= 240,000.  240K RPM is pretty bleedin' fast!  Perhaps you can find a
>video card that can do something like 1024x768 at 20?  Most video cards
>are concerned with achieving high, not low, refresh rates....
>
>Does anyone know of any electrically controlled optical deflection
>technology that has sub-microsecond reaction times?  I seem to recall
>seeing that some crystals change their refractive index with applied
>voltage; if I'm not misremembering, and if they change fast enough,
>that might do.
>
>I'd actually prefer to use such a thing not as a raster display, but as
>a vector display - hence the interest in electrically deflecting the
>beam.  I'd like to play vector videogames on a big white wall - either
>classic games under something like MAME, or my own....
>
>  
>
>>The upshot?  Take an old terminal with nasty screen burn.  Cut off
>>the gun end of the bottle, clean off the old phosphor.  Apply new
>>phosphor of some kind, then mount the laser rasteriser where the old
>>gun was.
>>    
>>
>
>Neat idea.
>
>  
>
>>Projecting raster images on the side of a building would be fun too.
>>    
>>
>
>But you'd need to crank the laser intensity way up.  Even then it might
>not be usable except at night. :)
>
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