(1)Targets and condition requirements
Visibility≥30km
Humidity≤80%
For vehicles with 2.3m×2.3m dimension
Reflectivity=0.3
Ranging ability≥20km
(2)Analysis and verification
The main parameters that affect ranging ability are peak power of lasers, divergence angle, transmitting and receiving transmittance, wavelength of laser, etc.
For this laser rangefinder, it takes≥1MW peak power of lasers, 0.8mrad divergence angle, 1570nm wavelength, transmitting transmittance≥90%, receiving transmittance≥80% and 67mm receiving aperture.
It is a laser rangefinder for small targets, ranging ability can be calculated by the following formula. Ranging formula for small targets:
: Detectable optical power
: Transmitting power of laser rangefinder(1MW)
: Transmitting transmittance(0.9)
: Receiving transmittance(0.8)
: Optical receiving area(67mm receiving aperture)
: Effective reflection area of targets(5.29㎡)
: Target reflectivity(0.3)
: Atmosphere attenuation coefficient(0.03)
: Visibility(according to testing condition)
: Distance to targets
As long as detectable optical power that reflected by targets is larger than minimum detectable power, a laser rangefinder is able to range distance to a target. For a laser rangefinder with 1570nm wavelength, generally, the minimum detectable power(M.D.S) of APD is 5×10-9W. Under 30km visibility with 22km distance to targets, the minimum detectable power is lower than M.D.S of APD(5×10-9W), therefore, under a condition with 30km visibility, a laser rangefinder can range distance for (2.3m×2.3m) targets up to 21~22km(might be close or less than 22km).
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