Wide Field of View Inversely Magnified Dual-Lens for Near-Field Submillimeter Wavelength Imagers

Abstract

A wide field of view inversely magnified dual-lens system for sub-millimeter wavelength imagers is presented in this contribution. The antenna is designed for near-field focusing, at a range of 2.1 m from the primary aperture and to work in the frequency range from 200 to 600 GHz. The half power beamwidth is 0.27 • (1 cm in the image plane) at 500 GHz, corresponding to a focused antenna directivity of approximately 55 dBi. The field of view is as large as ±25.4 • (±1 m at the nominal range), corresponding to a scan range of ±100 half power beamwidths. The shapes of the lens surfaces are optimized to minimize the phase aberration loss over the entire scanning range. Moreover, the lenses are designed to be as thin as possible to limit the dielectric absorption loss. The directivity reduction of the edge pattern with respect to broadside is approximately 1 dB with an efficiency of 56%, making this lens an excellent candidate for imaging applications. The dual-lens system can be refocused by displacing the secondary lens and shows an essentially unchanged angular half power beamwidth over a refocusing range of ±50% with respect to the nominal imaging distance. A demonstrator was fabricated and the experimental results at 500 GHz confirm the predicted performance.

Multiplexed readout of kinetic inductance bolometer arrays

“…From the readout point of view, the LASTKID detector array is divided into 66 readout channels with N =132 detectors in each. We note that some previously reported experiments utilizing the KIB technology have been presented in the context of the "CON-SORTIS" radiometer [18][19][20]. Here, we consider in particular the aspects of the readout with respect to the imager performance.…”

A Dual-Band Focal Plane Array of Kinetic Inductance Bolometers Based on Frequency-Selective Absorbers

“…The use of a single frequency selective layer has been chosen as a compromise between the cost and the rejection factor. The quasi-optical system of the imager is a dual-lens architecture described in [14], which allows full body imaging. The f-number, # , (ratio between the focal distance and diameter of the optics), is set to 2.…”

“…The quasi-optical system of the imager consists of an inversely magnified dual-lens structure as shown in Fig. 9 and described in [14]. In order to limit the absorption of out-of-band radiation, two low-pass filter windows are placed in the optical path between the lenses and the FPA.…”

“…In [15], a methodology to evaluate the power received by a distributed absorber under a parabolic reflector was presented. Here this methodology is applied to the combination of the proposed FSA KIBs and near field imaging optics described in [14]. In order to use the spectral analysis tool presented in [15] for this geometry, the plane wave spectrum of the dual lens optics is evaluated using the commercial software GRASP [22].…”

Dual Band Kinetic Inductance Bolometers for Submillimeter-wave Imaging: Experimental and Theoretical Optical Response

“…In order to optimize the performance of an imager based on a focal plane array of FSAs, a spectral Fourier optics (FO) technique as described in [4] is used. The quasi-optical system of the imager consists of the dual lens focusing in the near field as described in [5].…”