THz Active Imaging Systems With Real-Time Capabilities

• Published in: IEEE transactions on terahertz science and technology Vol. 1; no. 1; pp. 183 - 200
• Main Authors: Friederich, F., von Spiegel, W., Bauer, M., Fanzhen Meng, Thomson, M. D., Boppel, S., Lisauskas, A., Hils, B., Krozer, V., Keil, A., Loffler, T., Henneberger, R., Huhn, A. K., Spickermann, G., Bolivar, P. H., Roskos, H. G.
• Format: Journal Article
• Language: English
• Published: IEEE 01-09-2011
• Subjects: Arrays; Demodulating detector array; Detectors; electrooptic terahertz detection; femtosecond systems; Imaging; Lighting; Mirrors; optical parametric oscillator; photonic detectors; photonic systems; photonic-mixer device; Real time systems; submillimeter-wave imaging; submillimeter-wave technology; synthetic-aperture imaging; synthetic-aperture radar; terahertz imaging
• ISSN: 2156-342X; 2156-3446
• DOI: 10.1109/TTHZ.2011.2159559

This paper presents a survey of the status of five active THz imaging modalities which we have developed and investigated during the last few years with the goal to explore their potential for real-time imaging. We start out by introducing a novel waveguide-based all-electronic imaging system which operates at 812 GHz. Its salient feature is a 32-pixel linear detector array heterodyne-operated at the eighth subharmonic. This array in combination with a telescope optics for object distances of 2-6 m reaches a data acquisition speed suited for real-time imaging. The second system described then is again an all-electronic scanner (now for around 300 GHz ), designed for object distances of ≥ 8 m , which combines mechanical scanning in vertical direction, synthetic-aperture image generation in horizontal direction, and frequency-modulated continuous-wave sweeping for the depth information. The third and fourth systems follow an optoelectronic approach by relying on several- to multi-pixel parallel electrooptic detection. One imager is based on a pulsed THz-OPO and homodyne detection with a CCD camera, the other on either continuous-wave electronic or femtosecond optoelectronic THz sources and a photonic-mixing device (PMD) camera. The article concludes with a description of the state of the art of imaging with focal-plane arrays based on CMOS field-effect transistors.