Device and method for precise angular measurement by mapping small rotations into large phase shifts

摘要

A device and method for measuring a precise angular position of an element rotatable relative to a base. The device includes a rotating disk having a first track and a second track, each track being made up of alternating lines of high and low transparency. The rotating disk is rotated continuously about the axis of rotation of the element. Aligned opposite the first track and parallel to the rotating disk is an optical grid, fixed relative to the base, having alternating lines of high and low transparency. A measuring disk attached to the element is aligned coaxially with the rotating disk. The device also features two photoelectric sensors and which generate signals corresponding to variations in measured optical transmissivity. One photoelectric sensor generates a reference signal corresponding to variations in optical transmissivity through a combination of the first track and the optical grid. The other photoelectric sensor generates a measurement signal corresponding to variations in optical transmissivity through a combination of the second track and the track of the measuring disk. These signals are then processed by a processor to calculate information relating to the precise angular position of the element relative to base.