Shaft position encoder

Abstract

A new type of optoelectronic encoder conformed in one embodiment as a translucent cylinder having a reflective opaque coating on the lateral and end surfaces thereof, the cylindrical segment being further broken down into a set of lateral strips separated by a plurality of peripheral grooves. Portions of the reflective opaque coating are then removed, and the surface polished over selected areas of each strip to produce the desired light apertures. A first end of this cylinder has the opaque coating removed and is then polished to receive light. A second end is secured to a selected rotary shaft for measurement and selection of position of the latter, and is in effect an extension of the shaft. A bank of conventional phototransistors is then deployed over the cylinder, each respective phototransistor being exited by a light ray from the aperture associated therewith in the subjacent strip of the cylinder, thus indicating the position of the selected shaft. In a similar manner the other embodiment of the invention utilizes a plurality of optical fibers arranged in a longitudinal group in a cylindrical casting, each fiber being turned proximate one another to assume a radial position at a predetermined station of the cylindrical casting. Disposed in alignment with these cylinder stations are, once more, a plurality of conventional phototransistors, which when intermittently illuminated by rays of light from the fiber ends indicate specific shaft positions. In both embodiments the light source is provided by way of a light emitting diode or a laser beam shining directly into the polished end of the cylinder, the fibers in the second embodiment acting as wave guides to direct the light to the radially directed fiber ends.