Passive imaging at millimeter wavelengths is a constant struggle for increased sensitivity and angular resolution. Aperture synthesis is a particularly attractive technique for attacking these problems since it offers a high resolution from a given total antennas area and greater flexibility in the positioning of the antenna elements. This in turn can lead to a greater total collecting area and hence greater sensitivity than might be achievable with a single scanned antenna and with the additional benefit of electronic scanning. The high loss of millimeter-wave transmission lines means that received signals must be frequency translated to a more suitable frequency prior to transport to correlators. Although down conversion enables transmission by coaxial cables, up conversion onto optical carriers enables very low-loss optical fibers to be used for transmission and electronically programmable delay lines. In this paper we describe proof-of-principle experiments that demonstrate the application of optical up-conversion in aperture synthesis and also the direct formation of an image on a conventional optical camera from millimeter-wave signals modulated onto an optical carrier.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.