[Ronja] TX Head design question...

[J.D. Bakker]

>Hi All,
>    Just a quick question - Is there any reason why instead of forcing
>the TX led to produce the pulses, a "shutter" cannot be employed instead ?

No fundamental reason, just practical ones. Sourcing shutter 
film/foil which can reliably switch at 10MHz is likely challenging, 
especially in the small quantities that the average Ronja builder 
would need. Common LCD shutters max out at 100Hz-1kHz, so we'd need 
four to five orders of magnitude better performance. If the shutter 
were placed between LED and lens viewing angle and diffraction must 
be accounted for, if the shutter is placed after the lens it needs to 
be physically large (and diffraction is still an issue).

More here:

http://www.liquidcrystaltechnologies.com/tech_support/LCDShutterConsiderations.htm

Have you any suggestions for such a shutter?

JDB.
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