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]. 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 Figure: CO Emission Map [4]. It is now routine for astronomers to provide spectral maps of many species in star forming regions such as the Orion Nebula.

Figure: CO Emission Map. 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]. 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.

References

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