Electro-optical correlation arrangement for fast 3D cameras: Properties and facilities of the electro-optical mixer device

For advanced performances related to 3D metrology in production, security and traffic control, the Institut fur Nachrichtenverarbeitung is currently engaged in the investigation of a new 3D-camera system based on rf-modulation interferometry (RFMI), other than triangulation. The new 3D-camera system proposed in this paper uses the techniques of optical rf-modulation of the active illumination source and the correlation of these signals reflected from a target within a large aperture. This method yields all phase-correlation functions, relating to each voxel of the 3D-scene in parallel. Hence, the system delivers a fast parallel measurement and evaluation process by completely using a two-dimensional transmitting and receiving path. To full fill this concept, we have set up a binocular system using a modified Pockels-cell arrangement and a modulated laser transmitter. Since the electro-optical modulator plays a key important role in realizing the whale system, we would discuss the modified arrangement of stacked birefringent KD*P crystals that incorporates the properties of large aperture and high frequency modulation in the region of some tenth of megahertz. Additionally, an optical reference path is introduced to compensate for the fluctuation of the light source, thus enhancing the capability of the system. The experimental results of this reformed system will be presented in this paper, e.g., the standard deviation of lambda/2500 being obtained.