The synthetic aperture method is an attractive technique for terahertz nondestructive imaging without strict restraints on the beam form or the Rayleigh length of focus. However, the limitation of the aperture of the receiver array results in distortion and restricted lateral resolution of the reconstructed image. This paper introduces a nonlinear imaging processing principle, the correlating synthesis method, which has been applied in ultrasonic measurements. Using a pulse reflection mode terahertz time-domain spectrometry system and pulse compression preprocessing, we reconstructed images of metal cylinders. The results of comparisons with a synthetic aperture method verify the efficiency of the correlating synthesis method for improving the lateral resolution and eliminating fake images.
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