Fig. 4: Drone rotor image reconstruction via QCS imaging.
From: 10-km passive drone detection using broadband quantum compressed sensing imaging

a A photograph of the drone. b Photon-counting imaging using the SPAD array. c, d Sub-pixel scanning photon-counting images of the drone in the “power off” and “power on” states, respectively. e QCS imaging at 530 Hz. R and D represent the overall radius and blade length of the drone rotor, respectively. f The spectrum of each pixel on blade length D in (e). g The time-domain waveforms reconstructed correspond to the spectra in (f). The inset shows the duty cycle of each waveform. h The reconstructed drone rotor pattern