| CPC G01S 7/493 (2013.01) [G01S 7/4913 (2013.01); G01S 17/34 (2020.01); G01S 17/95 (2013.01)] | 1 Claim |
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1. A laser radar device comprising:
an optical oscillator oscillating laser light;
an optical modulator modulating the laser light oscillated by the optical oscillator;
an optical antenna radiating the laser light modulated by the optical modulator to an atmosphere, and receiving scattered light from a radiation target as received light;
an optical receiver performing heterodyne detection on the received light received by the optical antenna; and
a signal processor calculating for a range bin a spectrum of a received signal obtained by the heterodyne detection by the optical receiver, calculating a signal to noise ratio of the range bin, and integrating the spectrum of the range bin and spectra of one or more range bins adjacent to the range bin when the signal to noise ratio is less than or equal to a threshold value, wherein the signal processor includes:
a range bin divider dividing the received signal into range bins each having a set fixed time gate width;
a fast Fourier transform processor calculating a spectrum of the received signal for each of the range bins, by performing Fourier transform on the received signal divided by the range bin divider at a fixed number of set sampling points;
an SNR calculator obtaining the signal to noise ratio with respect to distance, from the spectrum calculated by the fast Fourier transform processor;
a resolution changer performing integration of a spectrum of a range bin being one of the range bins and spectra of one or more range bins adjacent to the range bin while maintaining the time gate width, when the signal to noise ratio calculated by the SNR calculator for the range bin is less than or equal to the threshold value;
a wind speed calculator calculating a wind speed value of the radiation target from a spectrum obtained as a result of the integration performed by the resolution changer;
a wind vector calculator calculating a wind vector from the wind speed value calculated by the wind speed calculator;
an SNR model calculator calculating the number of range bins to be integrated from the signal to noise ratio calculated by the SNR calculator and a signal to noise ratio estimated by a link calculation formula; and
a wind speed model calculator calculating a wind speed gradient using the wind speed value, the wind speed value being calculated by the wind speed calculator from the spectrum calculated by the fast Fourier transform processor, and estimating a wind speed value by a local wind model when the wind speed gradient calculated is greater than or equal to a threshold value,
wherein the resolution changer integrates spectra of the range bins in accordance with the number of range bins to be integrated calculated by the SNR model calculator and in such a manner that Doppler shift components corresponding to wind speed values estimated by the wind speed model calculator match each other.
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