Abstract: Electro-optical apparatus measures the average relative phase of an incident wave fringe pattern. The subject fringe, e.g., an interferometric pattern, passes through three sections of an optical mask, one characterized by fixed transmissivity and the other two by quadrature-displaced spatial fringe patterns. The light passing through each section is separately collected and detected to average the respective incident wave/mask section interactions. The phase of the incident fringe pattern relative to the mask is then determined by arithmetically processing the detected signals.In accordance with one aspect of the present invention, the subject fringe pattern is time modulated and the quadrature-shifted mask signals A-C coupled to obviate the requirement for the third, fixed transmissivity mask section.

Abstract: A noncontacting data-transmission system for transmitting data between rotating and nonrotating members includes at least one light source capable of transmitting modulated light signals disposed in one of the members. At least one light detector arranged along the same optical axis as the source and along an axis coincident with the axis of rotation of the rotating members is located in the other of the members. A lens having an optical center lying on an axis coincident with the axis of rotation of the rotating member is interposed between the light source and detector. The detector is located at the conjugate of the light source, such that an image of the light source is formed by the lens at the detector. The central portion of the lens may be modified, such as by forming a central opening in the lens, such that only an annular portion of the lens is utilized to form the image of the light source on the detector.