Patent ID: 7361922
Filing Date: 2008-04-22
Classification: G01N,G01S

Abstract:
1. A differential absorption lidar apparatus, comprising: light signal generation means for generating a first CW light signal with a first wavelength having a large absorption coefficient regarding a target, and a second CW light signal with a second wavelength having a small absorption coefficient regarding the target; a first light intensity modulation means for subjecting the first CW light signal output from the light signal generation means to intensity modulation with a first CW modulation signal having a first frequency in a baseband, and subjecting the second CW light signal output from the light signal generation means to the intensity modulation with a second CW modulation signal having a second frequency in a baseband; radiation means for multiplexing the first and second CW light signals output and subjected to intensity modulation by the first light intensity modulation means, forming the multiplexed light signals with two wavelengths in a predetermined beam size and beam shape, and radiating the multiplexed light signals in an air; and reception means for directly detecting scattered light from the target present in the air and converting the scattered light into an electric signal; and signal processing means for extracting only components with the first and second frequencies from the electric signal output from the reception means, and detecting a concentration of the target from a difference in one of an amplitude and an electric power between the two signals.