Device for interferometric measurements with compensation for tilt and position of measured cylindrical objects

摘要

An interferometric system for measuring cross-sectional dimensions of glass fibers and other elongate objects includes: a transmitting optics module for generating two laser beams, and causing the laser beams to intersect and interfere with one another over a measuring volume; several photodetectors to collect the light scattered by the glass fiber positioned in the interference region; and signal processing circuitry to deduce the fiber diameter using phase shifts between the signal pairs and fiber velocity using the frequency of the signals. The system further offers: elimination of the 360 DEG limitation on the product of sensitivity (degrees per micron) and range (microns), accompanied by an increase in accuracy using three or more detectors; uniform sensitivity over a large measuring volume, using fringe flare to compensate for changes in the effective angular separation of the detectors, due to fiber displacement within the measuring volume; and insensitivity to fiber tilt using large-area detectors for receiving the light scattered by the fiber.