Electro-optical shaft angle transducer having a rotatable refractive optical element

Abstract

A shaft angle transducer uses a rectangular prism to refract a light beam in proportion to the angular displacement of a shaft and then measures the refraction with a pair of light sensors. A fixed light source projects a light beam through a cylindrical lens and the prism to produce a patch of light on the fixed light sensors. An aperture shapes and sizes the light patch to nearly match the dimensions of one of the light sensors. The prism rotates with the shaft and refracts the light beam in proportion to the rotation angle. As the patch translates across the surface of the light sensors, more light impinges on one light sensor and correspondingly less light impinges on the other light sensor. The difference between the signals produced by the two light sensors produces an output signal that approximates the angular displacement of the shaft from a null position. The distance through which the light patch translates depends the on angular displacement of the prism and is immune to radial or axial translation of the prism.

Dependencies are inferred from the claim text.