Fast Active THz Cameras with Ranging Capabilities

We report on the realization of two active, fully electronic THz cameras, both operating at room temperature, but at different frequencies (645 GHz and 300 GHz, respectively). Active illumination together with the frequency-modulated-continuous-wave (FMCW) approach allows us to implement unique features such as phase-sensitive detection, suppression of spurious reflections and high resolution ranging. The measuring of the phase of the THz wave allows for sub-wavelength depth resolution while the ranging capabilities enable us to acquire an absolute depth map of objects under test with accuracy in the mm range. With both systems, we are able to acquire images with more than 55,000 pixels (phase and amplitude) in 9 seconds and the dynamic range exceeds 35 dB. The typical object distance is about 75–150 cm and the image size is in the order of hundreds of cm2 suitable for stand off detection of concealed weapons.

[1]  A. Lee,et al.  Real-time terahertz imaging over a standoff distance (>25meters) , 2006 .

[3]  C. am Weg,et al.  Quasioptical system design , 2009, OPTO.

[4]  David P. Dobkin,et al.  The quickhull algorithm for convex hulls , 1996, TOMS.

[5]  K. Siebert,et al.  Continuous-wave all-optoelectronic terahertz imaging , 2002 .

[6]  Warren J. Smith.  Modern Lens Design , 1992 .

[7]  Alvydas Lisauskas,et al.  Terahertz imaging with GaAS field-effect transistors , 2008 .

[8]  N. Llombart,et al.  Penetrating 3-D Imaging at 4- and 25-m Range Using a Submillimeter-Wave Radar , 2008, IEEE Transactions on Microwave Theory and Techniques.

[9]  I. Mehdi,et al.  600 GHz Imaging Radar with 2 cm Range Resolution , 2007, 2007 IEEE/MTT-S International Microwave Symposium.

[10]  H. Roskos,et al.  On the way to an active terahertz camera: Optic design and its experimental verification , 2007, 2007 Joint 32nd International Conference on Infrared and Millimeter Waves and the 15th International Conference on Terahertz Electronics.

[11]  M. Koch,et al.  Continuous-wave THz imaging , 2001 .

[12]  Hartmut G. Roskos,et al.  Continuous-wave terahertz imaging with a hybrid system , 2007 .

[13]  Pourya Khosropanah,et al.  1.6 THz heterodyne receiver for the far infrared space telescope , 2002 .

[14]  E. Linfield,et al.  Absorption-sensitive diffuse reflection imaging of concealed powders using a terahertz quantum cascade laser. , 2008, Optics express.

[15]  T. Loffler,et al.  Fast active THz-camera with global illumination , 2009, 2009 34th International Conference on Infrared, Millimeter, and Terahertz Waves.

[16]  Ralf D. Geckeler,et al.  Terahertz profilometry at 600 GHz with 0.5 μm depth resolution , 2008 .

[17]  Maya R. Gupta,et al.  Recent advances in terahertz imaging , 1999 .

[18]  Caihua Chen,et al.  Design of a 600 GHz fresnel lens antenna for passive and active imaging , 2007, 2007 IEEE Antennas and Propagation Society International Symposium.

[19]  T. May,et al.  Towards an active real-time THz camera: first realization of a hybrid system , 2007, SPIE Defense + Commercial Sensing.

[20]  Z. Jiang,et al.  Near-field terahertz imaging with a dynamic aperture. , 2000, Optics letters.

[21]  T. Loffler,et al.  Fast active THz camera with range detection by frequency modulation , 2008, 2008 33rd International Conference on Infrared, Millimeter and Terahertz Waves.