V.E.  Imaging


Astronomical:  By far the most successful and established form of imaging in the SMM/THz is astronomical imaging. Since astronomical applications are inherently passive and the cost of astronomical photons very high, it is not surprising that the astronomical community has taken the lead.  However, since they deal with a much more slowly varying object they have concentrated on sensitivity more than speed and have developed both heterodyne [1] (for looking at narrow line emission) and bolometer and photoconductors (for looking a broad thermal and synchrotron)[2, 3] emission.  Especially the latter have focused on low temperature systems and often arrays.


With these technologies astronomers have long made images of dust and other emissions and soon after spectral line radiation was discovered elaborate maps of these emissions were made as well.  The most detailed of these is the survey of CO line emission at 115 GHz of the Milky Way, shown in Fig. V.E-1 [4]It is now routine for astronomers to provide spectral maps of many species in star forming regions such as the Orion Nebula.


Figure V.E-1 An image of the Milky Way taken in the 115 GHz emission of CO.

Terrestrial:  It has been known since the early days of electromagnetic science that the SMM/THz represents a useful compromise between the ability to penetrate materials and diffraction limited resolution, the first serious effort to develop this application did not happen until the Army’s Near MilliMeter Wave program [5, 6].  By now imaging in the SMM/THz has become a topic of such wide interest that there are many comprehensive reviews [7-9].  It should perhaps be remarked that there is a large and rapidly growing public application that is nipping at the edge of the SMM/THz:  collision avoidance radar for automobiles.  In the next sections we will use as illustrations points chosen from the complex design space of SMM/THz imaging.


V.E.1  Passive terrestrial systems

    V.E.1.a  Outdoors at relatively low frequency

    V.E.1.b Indoors and at high frequency

    V.E.1.c  Passive arrays

V.E.2  Active systems

    V.E.2.a  Speckle

        V.E.2.a.i Impact of Modulated Mode Mixing on Image Speckle - Additional Detail

           A.  The images

           B.  Speckle contrast

               B.1  Image of a simple object – a knife covered with cloth

               B.2  Image of a complex object – the atrium of the OSU Physics Building

               B.3  Mode mixed image of a complex object – the atrium of the OSU Physics

               B.4  Overview

           C.  Conclusions

     V.E.2.b Arrays

     V.E.2.c Proximate Imaging


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[1] N. Whyborn, The Far Infrared and Submillimeter Universe, ESA SP-401 (1997) 19-24.

[2] A. Poglitsch, C. Waelkens, N. Geis, The Photoconductive Array Camera and Spectrometer (PACS) for FIRST, in: J.B. Breckinridge, P. Jacobsen (Eds.) UV, Optical, and IR Space Telescopes and Instruments, SPIE, Munich, 2000, pp. 221-232.

[3] M. Griffin, B. Swinyard, L. Vigroux, The SPIRE Instrument for FIRST, in: J.B. Breckinridge, P. Jacobsen (Eds.) UV, Optical, and IR Space Telescopes and Instruments, SPIE, Munich, 2000, pp. 184-195.

[4] T.M. Dame, D. Hartmann, P. Thaddeus, Ap. J., 547 (2001) 792-813.

[5] P.W. Kruse, Why the military interest in near-millimeter wave imaging?, in: G.A. Tanton (Ed.) Millimeter Optics, SPIE, 1980, pp. 94-97.

[6] S.M. Kulpa, E.A. Brown, Near-Millimeter Wave Technology Base Study, in, Harry Diamond Laboratories, Adelphi, MD, 1979.

[7] R. Appleby, R.N. Anderton, Proc. IEEE, 95 (2007) 1683-1690.

[8] R. Appleby, H.B. Wallace, IEEE Ant. Prop., 55 (2007).

[9] E.N. Grossman, A. Luukanen, A.J. Miller, Terahertz Active Direct Detection Imagers, in: R.J. Hwu, D.L. Woolard (Eds.) Terahertz for Millitary and Security Applications II, SPIE, 2004.