| 摘要 |
PURPOSE:To measure exactly a number of revolution in a bright place without providing with a high accuracy an optical reflecting body by photodetecting a spot image on a projecting plate of a periodical light source light formed by plural reflecting bodies for turning as one body with a rotating body, by plural photodetecting parts connected to an optical fiber, respectively. CONSTITUTION:An irradiating optical beam from a light source 3 driven by a periodical pulse is reflected by plural reflecting surfaces 2 of a heat-cut polygonalpyramidal body for turning as one body with a rotating body 1, and a spot image 7 is formed on spot points A1, A2..., or B1, B2... of an annular projecting plate 6. Subsequently, by an optical fiber 9 corresponding to a photodetecting surface arranged between the points of both groups, a light of the spot image 7 is made incident to a photoelectric converting element 14 through the bundled fibers 9. In this case, the photodetecting surfaces of the points A1, A2... are faded out about simultaneously, also the photodetecting surfaces of the points B1, B2... are faded in about simultaneously, a spot image light of the number corresponding to the number of revolution is photodetected without being influenced by a scattering light or an external light, and the number of revolution is measured exactly in a bright place, too, without providing with a high accuracy an optical reflecting body. |
