| A conceptual systems level analysis has been performed for the direct high resolution snapshot imaging of broadband millimeter sources using a depleted aperture imaging system (interferometer). Traditionally, millimeter wave arrays have used conventional radio-frequency type technology to indirectly image sources in the Fourier plane. Instead, here, technology has been developed to directly image millimeter waves in the image plane utilizing optical upconversion.;To minimize the maximum sidelobes of the point spread function of the imaging system, an antenna array composed of two concentric rings is chosen. This design ensures uniform and isotropic spatial frequency coverage in a short integration time. Utilizing electro-optic modulators, incoming millimeter energy is converted into the infrared, which is fed to a microlens array via optical fibers. Direct imaging is then performed on an infrared detector array via Fizeau (image-plane) beam combination.;Right through the optical axis of the imaging system, homothetic mapping is preserved, i.e., the entrance and exit pupils are replicas of each another, scaled by a constant factor. This ensures direct snapshot imaging over a wide bandwidth with high angular resolution, high sensitivity, and a wide field of view. Since the Fizeau setup allows access to large fields, mosaicing wide fields is possible. |
