Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!rpi!sci.ccny.cuny.edu!phri!cooper!gene From: gene@cooper.cooper.EDU (Gene (the Spook) ) Newsgroups: sci.electronics Subject: Re: Bad News- Lasers replace Radar guns Message-ID: <2057@cooper.cooper.EDU> Date: 19 Jan 90 23:06:48 GMT References: Distribution: na Organization: The Cooper Union (NY, NY) Lines: 49 in article , mikemc@mustang.ncr-fc.FtCollins.NCR.com (Mike McManus) says: > In-reply-to: besler@egrunix.UUCP's message of 17 Jan 90 16:03:38 GMT > > > In article <349@egrunix.UUCP> besler@egrunix.UUCP (Brent Besler) writes: >> (Discussing laser speed detectors...) >> It can't be used while moving currently since it can't determine the police >> cars speed yet. > > Why is that? How do the current radar models work with respect to telling the > speed of the officer's car? Wouldn't it be similar? For a semi-educated guess, how 'bout this: The way mobile radar works is that you spit out a beam and collect two inputs. The first is the signal reflected from stationary objects, such as trees, signs, etc. If the squad car is moving at 55mph, the reflected signal should be 55mph. The second signal would be that of the alleged speeder. If, for example, the target is going 70mph, the reflected signal should indicate 15mph. By taking the difference, you can calculate the alleged speeder's speed. With a laser ranging system, I guess that you have to "paint" the target with a laser beam and read the interference pattern to determine the target's speed. Both systems work because of the doppler effect, but the laser can read only one interference pattern (so far). Interestingly enough, it seems as though the laser-type system is like that of laser-guided missiles, from what I've read. Also, call Cincinnati Microwave (of Escort and Passport fame) and ask for their "Why Radar Guns Are Inaccurate" (or something to that effect) booklet. So next time Smokey gets missile-lock on you and you know you weren't speeding, you'll have *some* defense, once you know how radar guns work. Incidentally, does anyone know the author or publisher of "The Ticket Book" which was written by an ex-cop??? I'd like to get my hands on a copy, but My local bookstores can't/won't help me on the basis of such skimpy info. Thanx! Spookfully yours, Gene Traffic court: Where else in the United States are you guilty until proven innocent?