With double layered windows (double glazed), the ability to use triangulation between laser TX and rx means it may be possible to capture vibrations from the inner glass panel.
Infra-red absorbtive/scattering glass makes the most sense, or external curtain materials, but we are int purpose built locations at this point.
a poor mans solution should be THE semi opaque glass we use in kitchen that has those INCLINED trangular cut surfaces throughout while the granular surface on the other side. Any light (though depends on the wavelength) would bounce to the extreme right or left. Moreover, without a small bug in the windows itself (say a prism) it would be difficult to capture the reflected beem anyways. or yes as u suggested, scattering glass. a double layered window with distinct difference in refractive index of exterior & interior glass "might" be a better solution. I experimented a simple solution. A 3v DC motor pressed in the glass window to cause a small noise & glass vibration would almost completely remove the chances for evasdroping. (but hey it was a extermely simple amature solution to defeat my own amature equpment anyways. Any coment on this, welcome!) -bipin _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.grok.org.uk/full-disclosure-charter.html Hosted and sponsored by Secunia - http://secunia.com/