Holographic imaging at 70 GHz

Lensless Fourier transformation (LFT) holograms of a (1 by 0.75 cm) rectangular aperture of a millimeter wave horn approximating a point source and of an extended object in the form of a back-illuminated opaque letter A have been formed using 70-GHz coherent millimeter wave radiation. A spiral scan format was utilized to record the net irradiance in the hologram plane with the aid of a millimeter wave crystal detector. Images retrieved from demagnified transparency film records of this irradiance distribution exhibit the general characteristics of LFT holograms and confirm the resolution capabilities of the holographic imaging process.