Retroreflection

[KSMITH1@mailgw.sanders.lockheed.com]

Mike Miller says:

> From: "Mike Miller" <JoMi@msn.com>
>Date: Fri, 18 Oct 96 18:10:37 UT
>Subject: RE: Radar alert 
>
>Why wouldn't the highly reflective surface of the rear view mirror do the same 
>thing as a CD hanging there?
>
>mike miller

What you want is a retroreflector, not a reflector.  A flat mirror reflects 
light at twice the angle the input light was to the normal to the mirror 
surface.  A retroreflector reflects the light back upon itself.  Road signs are 
usually based on tiny spheres that perform this action with some beam spreading.
(One brand name is Scotchlite.)  Tail light reflectors are made up of many tiny 
corner cubes that, via three bounces, send the light back.  For a CD to be 
better than a white surface, it must have some retroreflective property, perhaps
related to the tendency of the tiny pits to diffract the light.

To design an efficient countermeasure, consider where the light is comming from 
vs. where you want it to go.  Design your reflector/retroreflector accordingly.

***                 ...Kirby    (Kirby A. Smith)                 ***
***              ksmith1@mailgw.sanders.lockheed.com             ***
***              [=]   kirby.a.smith@lmco.com                    ***
***  Opinions expressed herein are entirely those of the author. ***