Why doesn't my laser set off my laser detector

marv8000

Newly Enlightened
Joined
Feb 3, 2005
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12
Location
Texas
Why doesn\'t my laser set off my laser detector

I have tried both a green laser and a red laser to set off my laser Escort laser detector and it doesn't work. Why? I noticed however, when I move my laser / radar detector in front of my navigation screen it sets off the laser detector. What gives?
 
Re: Why doesn\'t my laser set off my laser detector

It is looking for the "modulation" or pulses in the light beam. Your navigation display probably has dimming capabilities, which would pulse the light, as well as if it was CCFL, it would also appear "modulated".

Laser radars transmit pulsed laser light to measure target range. The time it takes for a laser light pulse to travel (at the speed of light) from the ladar to the target and back is used to compute the distance from the ladar to target and back (distance pulse travels = speed of light x time). Target range from ladar is half of this distance (Range = 0.5 x speed of light x time). The change in target range over time (1/3 second typical) equals target velocity. Laser radar must transmit a minimum of 2 pulses to get at least 2 range measurements at 2 different times to compute speed. In reality laser radars transmit tens to hundreds of pulses per second.

"Ladars use a semiconductor diode (typically 3 diodes) to generate laser light. Most traffic ladars emit laser light around 904 nm wavelength. Other wavelengths are possible; for example aluminum gallium arsenide (AlGaAs) diodes emit light at a wavelength of 850 nm (some fiber optics use this wavelength). Gallium arsenide (GaAs), classified as an injection laser, emits light between 880 nm to 900 nm between the temperatures of -20 and 140 degrees Fahrenheit."
 
Re: Why doesn\'t my laser set off my laser detector

[ QUOTE ]
NewBie said:
It is looking for the modulation in the light beam. Your navigation display probably has dimming capabilities, which would pulse the light, as well as if it was CCFL, it would also appear "modulated".

[/ QUOTE ]

Exactly. That's the only way that it can differentiate from that other huge IR emitter in the sky, the sun. If it didn't restrict it's detection to a pulsed or modulated light source, it would either false-trigger on sunlight or it would be swamped and desensitized by the sun. Either way it wouldn't work.
 
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