Optical Field Imaging Echo Demodulation Ratio Method to Suppress the Image Quality Degradation Caused by Light Intensity Disturbance

Laser optical field imaging system transmits multiple laser beams to scan the target for imaging. When the new optical field imaging theory is applied in practical engineering,the inevitable multi beam intensity jitter effect will cause fluctuation in intensity amplitude. In the subsequent reconstruction of spectrum components based on the spectrum iteration theory,the fluctuation in light intensity amplitude will cause the reconstruction spectrum error,which will lead to degradation of imaging quality in further. Aiming at the problem of image quality degradation of optical field imaging caused by laser beam intensity disturbance,an approximate calculation method based on the demodulation ratio of light field echo signal is proposed in this study. First,the interference light field signals with different frequencies in optical field echo signal are demodulated. The demodulated optical field echo signal is affected by random fluctuations of the beam intensity amplitude. The phase closure coefficient is calculated based on the multi beam phase closure theory and an isospectral sampling array is constructed. Then, according to the principle of isospectral iterative reconstruction, the high-order spectral components can be obtained by iteratively solving the lower order spectral components in turn. In this study,the influence model of the light intensity perturbation factor on reconstructed spectrum component error is established,and the influence mechanism of light intensity perturbation on image quality is revealed. Due to the amplitude fluctuation effect of beam intensity, the disturbance factor of beam intensity fluctuates randomly,which affects the accuracy of spectral signal reconstruction and reduces the imaging quality. In order to eliminate the influence of light intensity disturbance on image quality,the influence of light intensity disturbance factor on reconstructed spectral signal should be suppressed. In the weak turbulence scene,the scale coefficient of the disturbance factor of multi-beam intensity can be approximated by the demodulation component of laser echo signal. The light intensity perturbation factor is calculated by the scale coefficient of demodulation echo signal. The value of laser beam intensity perturbation factor is substituted into the spectrum reconstruction model. Finally, the spectrum of eliminating light intensity disturbance factor is obtained. The target image is obtained by performing an inverse Fourier transform of signal spectrum component,and the image index of target is calculated to evaluate the reconstructed image quality. The demodulation ratio of optical field imaging method is analyzed and verified based on the simulation experiment. The simulation experiment results show that the demodulation ratio method suppresses the light intensity disturbance and improves the reconstruction image quality. The demodulation ratio method can effectively suppress the degradation effect of light intensity disturbance and improve the image quality. The validity of the demodulation ratio method is verified based on the desktop experimental platform. The experimental results show that the image sharpness is significantly improved,and the three image quality evaluation indexes of the reconstructed image Strehl ratio,peak signal-to-noise ratio and structural similarity are all improved,which further proves the effectiveness of the demodulation ratio method. The imaging error correction model of light intensity perturbation factor is proposed and the corresponding demulation ratio solution is proposed in optical field imaging system. This study provides an effective theoretical guidance for the suppression of light intensity perturbation factor and the improvement of image quality in actual optical field imaging. The research shows that the proposed demodulation ratio method can effectively suppress the influence of beam intensity disturbance on image quality,and effectively reduce the requirements of beam intensity stability and multi-beam intensity consistency for optical field imaging,thus reducing the difficulty of optical field imaging engineering. The research can provide technical support for experimental research and application transformation of optical field imaging technology.