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Proceedings Paper

Aplanatic THz imaging
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Paper Abstract

Optical systems for THz imaging frequently consist of readily available components - typically a single spherical or parabolic surface. For THz imaging applications, the range is short, due to limitations associated with atmospheric attenuation. For these applications, single spherical and parabolic surfaces are neither stigmatic, aplanatic nor Herschel. As a result, many THz imaging systems exhibit significant image degradation caused by primary aberrations. Further, the short range limitations frequently result in image degradation due to near violation of the paraxial assumption. For improved imaging, an aplanatic system is required. To achieve aplanatism, a minimum of two aspheric surfaces is required. Aplanatism requires stigmatic performance which dictates surfaces that are conic sections of revolution. A minimum of two are required to exhibit stigmatism and meet the sine condition. An improvement of receiver form factor allows for a decrease in optical image distance and an increase in system magnification factor. This significantly improves a number of THz imaging characteristics such as depth-of-field while maintaining the diffraction-limit resolution and reducing the primary objective diameter. Reduction of objective diameter reduces signal strength - principally at the expense of specular reflections. This paper summarizes the results of the optical system design and its incorporation into THz imagers containing THz receivers with improved form factors. Efforts at incorporation of optical zoom will be presented.

Paper Details

Date Published: 15 April 2008
PDF: 8 pages
Proc. SPIE 6949, Terahertz for Military and Security Applications VI, 69490H (15 April 2008); doi: 10.1117/12.777087
Show Author Affiliations
Steven T. Griffin, Univ. of Memphis (United States)
Keith A. Krapels, Office of Naval Research (United States)

Published in SPIE Proceedings Vol. 6949:
Terahertz for Military and Security Applications VI
James O. Jensen; Hong-Liang Cui; Dwight L. Woolard; R. Jennifer Hwu, Editor(s)

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