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.

Abstract: Methods of compensating for errors in a laser pointing device, particularly for use in three-dimensional applications, by accurately controlling the angle that the laser beam makes in space.A method for rectifying a laser pointing device that aims a laser beam by deflecting the beam through a plurality of optical deflection devices each directed by a galvanometer controlled by an input. In the method, the laser pointing device is established in an accurate angular relationship to at least four fiducial points. The angular errors internal of the laser pointing device are determined by comparing actual galvanometer inputs to nominal galvanometer inputs, assuming no error in the established angular relationship. The actual galvanometer inputs are those that aim the laser beam at the fiducial points (while recognizing the existence of the internal errors), and the nominal galvanometer inputs are those that would aim the laser beam at the fiducial points assuming no internal errors in the laser pointing device.