IR Illuminator without visible glow
- Thread starter Dometrius
- Start date
-
- Tags
- ir illuminator
Yes, I can imagine the engineering it took back then in making a high voltage Xenon lamp flash at that frequency, it is a piece of cake to get LEDs to modulate even much faster than that, appear to dim using PCM, etc. It appears 3M sold the Opticom division to another company after I retired in 2004.
They'd squeal like a photographic flash strobe as the high voltage charged up the capacitor then pop when it would discharge and the tube would flash. Squeal-pop-squeal-pop-squeal-pop at 8x per second. They were a small version of some much larger REIL (Runway End Identification Lighting) I worked on at some county airports. You could hear those babies from 100 feet away if no planes were running nearby.
In the early 70's I once saw some info where General Electric was using something similar to communicate LOS over decent distances mainly between stationary objects like tall buildings, etc. By the pictures I think it was about 2 feet in diameter. It may have used some sort of modulation of the light to mimic serial code like mark-space with lots of timing protocol, I don't know. The ad or image didn't elaborate, just me speculating, After 45 years I cannot recall even if I knew at the time.
Today's LEDs can modulate so quickly and with such precision that a serial number can be broadcast by the vehicle via the IR emitter and the receiver logs it and time/date stamps it with the vehicle ID for legal purposes in case the municipality needs to know which vehicle preempted the signal, at what time and in what state the traffic signals were when preempted, etc.
OK...no more "Opticom" from me!
Last edited:
Fastb
Known around here
@TonyR ,
In the 90's, a fellow engineer said he knew someone who mounted a light (details murky) behind the front grille that mimicked the lights on emergency vehicles. He claimed the light caused the traffic lights to always give the car a green light.
I asked "Is that was legal?
He said "The gov't can't outlaw light."
"Then why don't more people put those lights on their car?"
"Not enough people know about it."
I was skeptical. TonyR, does this sound like hogwash? Were copycat lights a problem with the emergency vehicle traffic light system?
Fastb
In the 90's, a fellow engineer said he knew someone who mounted a light (details murky) behind the front grille that mimicked the lights on emergency vehicles. He claimed the light caused the traffic lights to always give the car a green light.
I asked "Is that was legal?
He said "The gov't can't outlaw light."
"Then why don't more people put those lights on their car?"
"Not enough people know about it."
I was skeptical. TonyR, does this sound like hogwash? Were copycat lights a problem with the emergency vehicle traffic light system?
Fastb
For the most part, yes. But not completely.....
When the model 168 Phase Selector (the receiver and decoder) was introduced circa 1973, it wasn't extremely sophisticated and some rogue techs and engineers that new how to make a copycat model 792 emitter function to 'fool' it sprung up, but not many as far as I knew. Back then, there was no eBay or Craig's List and 3M relied on a VERY tight and strict marketing system. They and people that made warning lights, strobes and sirens for emergency vehicles (people like Federal, Whelen, etc.) would sell ONLY to municipalities and it was a pretty rock solid marketing system.
The more sophisticated model 188 phase selector and matching model 492 emitter came out circa 1992 and it became next to impossible to preempt a signal with a copycat emitter, even if it emulated the older model 792, due to the method in which specific ID's embedded into the 492 emitter had to be entered beforehand into the model 188 phase selector via PC with proprietary software; if the 188 did not find that ID from an emitter, it would not preempt the traffic signal.
But it took several years for the old 168's to disappear and I guess some of the copycat emitters functioned for a short time. Also, when eBay popped up circa '97 a few copycat emitters also may have shown up in cars but they didn't get to enjoy them long, maybe a year at best. I personally never was aware of any counterfeit or copycat units working even in 'Silicon Valley'.
And speaking of eBay and traffic signals, I worked on the traffic signals at Hamilton and Greylands/April , which is where their main office is in San Jose, CA, several times in the 29 years I spent there.
EDIT: The practice of preempting the signals by unauthorized people or vehicles is/was VERY illegal, and language was placed into CA law years ago, as I had read it many times (not sure what year it was written in). But we all know how effective making something illegal works, right? Not 100% compliance , for sure.
Last edited: