| 摘要 |
A position sensor for determining the position of an encoded surface applied to an element. Several embodiments of a position sensor (30, 100, 110, 110', and 200) are disclosed. In each embodiment, light at a reference wavelength and at a test wavelength travel along a common optical path until separated by an interference filter (40, 120, 214). A test beam comprising light at the test wavelength is transmitted through the interference filter toward an encoded surface (44, 216), which reflects a portion and transmits another portion of the test beam. The transmitted portion of the test beam is reflected by a mirror (50, 222) which is disposed adjacent an opposite surface of a rotatable disk (54) or a linear encoder (220) from that on which the encoded surface is applied. The transmitted portion of the test beam is reflected by the mirror along a first optical path (74, 130, 224), while the portion of the test beam that is reflected by the encoded surface travels along a second optical path (68, 138, 230). The relative transmissivity/reflectivity of the encoded surface varies with its position in respect to the point at which the test beam is incident, thereby varying the intensity of the reflected and transmitted portions of the test beam in a predefined manner. A reference beam, which comprises light at the reference wavelength, is reflected by the interference filter along a reference path. The reference beam travels along the reference path and is split by a beam splitter (66, 146, 240). A portion of the reference beam is transmitted toward a mirror (70, 150, 246). The mirror directs the transmitted portion of the reference beam back toward the interference filter, from which it is again reflected along the first optical path. The portion of the reference beam reflected by the beam splitter is also reflected by the interference filter so that it travels along the second optical path, with the portion of the test beam reflected by the encoded surface. Light traveling along the first and second optical paths enters adjacent ends of optical fibers (80, 86) and is conveyed to a sensor assembly (88). A plurality of photodiodes (92, 94, 96 and 98) in the sensor assembly determine the relative intensities of the transmitted and reflected portions of the test and reference beams to define the position of the encoded surface, compensating for light losses in the optical fibers and other parts of the system.
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