CPS@cup.portal.com (CHRIS PATRIC SMOLINSKI) (05/31/91)
Some of us at work were speculating on just how those new police speed checking systems work - the ones that use lasers. There was a segment oon the local news about them (and typical of local news, it was generally useless and non-revealing). Anyone have any hard facts on how they work? Best we came up with was a IR near visible (say 900nm) wavelength, pulse modulated. Still not sure how well that would reflect off all cars. Any ideas? - CHRIS
kludge@grissom.larc.nasa.gov ( Scott Dorsey) (05/31/91)
In article <42808@cup.portal.com> CPS@cup.portal.com (CHRIS PATRIC SMOLINSKI) writes: >Some of us at work were speculating on just how those new police speed >checking systems work - the ones that use lasers. There was a segment >oon the local news about them (and typical of local news, it was generally >useless and non-revealing). This is a wild guess intended to begin speculation. It should not be considered any more than that: How about sending your laser signal through a beamsplitter. Most of the signal goes off to the car and is reflected back. Probably a set of lenses on the incoming path will be required to prevent a lot of extraneous stuff from being reflected back too. Then the incoming signal is heterodyned with the reference signal that the beamsplitter forked off. An interference pattern is generated, which is scanned into a computer and voodoo occurs and the speed is read out on a display. --scott
mackay@eecae.ee.msu.edu (James F. MacKay) (05/31/91)
CPS@cup.portal.com (CHRIS PATRIC SMOLINSKI) writes: >Some of us at work were speculating on just how those new police speed >checking systems work - the ones that use lasers. At a presentation about 2 years ago, a man (I forgot his name) said his company had working laser systems but for stationary police only. They would not work while the officer was moving. Have they fixed this problem?
john@newave.UUCP (John A. Weeks III) (06/03/91)
In article <1991May31.135308.27239@msuinfo.cl.msu.edu> mackay@eecae.ee.msu.edu (James F. MacKay) writes: > CPS@cup.portal.com (CHRIS PATRIC SMOLINSKI) writes: > > Some of us at work were speculating on just how those new police speed > > checking systems work - the ones that use lasers. > At a presentation about 2 years ago, a man (I forgot his name) said > his company had working laser systems but for stationary police only. > They would not work while the officer was moving. Have they fixed > this problem? The Wisconsin State Patrol has been using an optical system since 1980. Their system requires the patrol car to park in a pre-specified spot and aim the optical system at a specially installed delineator post in the median strip of the highway. The delineator post has an orange reflector on it. The distance from the optical emitter to the reflector is critical and must be recalibrated on a regular basis. The State Patrol in Wisconsin also operates weekend speed 'comando' teams that set up temporary optical speed measurement ranges in areas that are targeted for enforcement. They normally have one person operating the speed reader with a camera to record the evidence, and up to 8 squads to make the arrests. They can issue several hundred tickets in a shift thanks to the hot foot motorists from Minnesota and Illinois (states that don't enforce speed limits) who rely upon radar detectors. Wisconsin has also experimented with 'Electric Bridges', bridges that have instrumentation built in to record vehicle weight and speed. This systems works well on highways with lower traffic volumes because the readings are accurate only when one car at a time is on the bridge. I hear that this information is used mainly for traffic surveys and rarely for enforcement. -john- -- ============================================================================= John A. Weeks III (612) 942-6969 john@newave.mn.org NeWave Communications, Ltd. ...uunet!tcnet!newave!john