Terahertz spectral imaging system and security surveillance system employing the same

A tunable terahertz (THz) bandpass filter comprising:

• a visible or infrared (IR) light source for generating a visible or IR light;
• a spatial light modulator receiving the visible or IR light and modulating it to generate spatially structured light patterns;
• and
• a semiconductor plate,
• wherein the spatial light modulator projects the light patterns onto the semiconductor plate, wherein the light pattern is configured to photo-generate carriers in the semiconductor plate to form a metamaterial THz bandpass filter in the semiconductor plate, the metamaterial THz bandpass filter being a metamaterial structure having a predefined transmission spectrum in a THz wavelength range;
• and
• wherein the spatial light modulator is configured to be controlled by an external control device to generate a plurality of different light patterns to form different metamaterial THz bandpass filters with different predefined transmission spectra in the semiconductor plate.

A security surveillance system comprising:

• a visible light imaging camera generating visible light images;
• a terahertz (THz) spectral imaging system generating a plurality of 2-dimensional (2D) THz images each based on THz light of a different frequency range, the THz spectral imaging system including:
• a THz 2-dimensional (2D) imaging camera;
• a tunable THz bandpass filter;
• and
• a control device coupled to the THz 2D imaging camera and the tunable THz bandpass filter,
• wherein the tunable THz bandpass filter has a filter plate disposed in front of the THz 2D imaging camera to filter the THz light before it is received by the THz 2D imaging camera, and
• wherein the control device is configured to tune a transmission spectrum of the tunable THz bandpass filter, and to control the tuning of the tunable THz bandpass filter and the THz 2D imaging camera according to a predetermined timing sequence, to generate the plurality of 2D THz images each based on THz light of a different frequency range;
• a Light Detection and Ranging (LiDAR) system generating LiDAR images representing distances of objects from a sensor of the LiDAR system;
• a central control and data processing system;
• and
• an alarm system,
• where the central control and data processing system is coupled to the visible light imaging camera, the THz spectral imaging system, the LiDAR system and the alarm system, and is configured to:
• perform spectral analysis of the 2D THz images to generate processed THz image indicating presence of any one of a plurality of predefined materials, fuse the visible light images, the processed THz images and the LiDAR images into a fused image, and automatically analyze the fused image using machine learning to generate an alarm based on learned behavior patterns of targets in the fused image.