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."
