Re: IR filters

[Luis Marques <marques@rtis.ray.com>]

> How much power really is needed? The source laser *must* be down in
> the milliwatt range, and must be reading microwatt levels reflected
> back. It seems like a flashlight pointed at the source would
> completely swamp any reflected signal, let alone requiring megawatt QH
> bulb assemblies . . . Just kinda curious.

Some have asked why you would need soch a powerfull IR source to 'blind'
a LIDAR gun, given the fact that these units should operate in the mili
or micro watt range.  It has to do with beam widths.  The LIDAR gun has
a very narrow beam width.  That means that as the signal gets to the
car, bounces, and returns to the receiver it is maybe 6 ft. wide.  The
intensity of the signal is still very strong, since its power is only
spread over a small area.

The laser jammer OTOH doesn't know where the REO is, so it must shine IR
energy in all forward directions (and backwards if you want to cover
your tail) much like a broad high beam pattern (not ultra-narrow pencil
beams) to make sure it illuminates the laser gun.  So the IR energy of
the jammer is spear over a big area which could be 1000 times larger
than the laser gun's beam, and in comparison, is 1000 times weaker.  For
those of you with a radio background, this is equivalent to the "antenna
gain".  For the rest of us, this is equivalent to your adjustable
spot-flood flashlight.  In spotlight mode, the flashlight is very
bright, but only illuminates a small area.  In floodlight mode, the
light is weaker, but illuminates a much larger area.  Conservation of
energy and all that.  HTH

Luis Marques
'87 4kcsq