Fig 1.
Proposed signal preprocessing procedure of the THz see-thru imaging.
Fig 2.
Image normalization techniques to compensate for non-uniformities in the measurement environment and transmitter/detector array characteristics.
Fig 3.
Conceptual illustration of the region-of-interest (ROI) extraction process.
Fig 4.
Image resizing for equalizing horizontal and vertical resolution scaling in THz images with different horizontal and vertical resolutions.
Fig 5.
Configuration of the THz imaging system used to validate the proposed preprocessing method.
Fig 6.
Photographs of the samples under inspection.
Fig 7.
Beam profiles of the conveyor belt without samples.
Fig 8.
THz raw image of Sample A.
Fig 9.
Processed image of Sample A using the compensation method for distortion and extraction of ROI.
Fig 10.
Processed image of Sample A using the overall proposed method.
Fig 11.
THz raw image of Sample B.
Fig 12.
Processed image of Sample B using the compensation method for distortion and extraction of ROI.
Fig 13.
Processed image of Sample B using the overall proposed method.
Fig 14.
THz raw image of Sample C.
Fig 15.
Processed image of Sample C using the compensation method for distortion and extraction of ROI.
Fig 16.
Processed image of Sample C using the overall proposed method.
Table 1.
Image quality improvements achieved using the proposed preprocessing method.
Fig 17.
Processed images with FID algorithm for raw and preprocessed THz images for three samples.