| 摘要 |
<p>PROBLEM TO BE SOLVED: To position a table accurately even if there is temperature drift, by performing the positioning by the difference of the detection value of the voltage under the condition that a shading board is shading light and the detection value of it when a work table shades a luminous flux, getting over the shading position of the shading board. SOLUTION: A positioning device is equipped with a work table 12, which crosses luminous fluxes in shading direction in order from one side, in the range of position detection area, between a light receiver 4 and an irradiation light source 3, and a screen board 9 which intercepts one part of the luminous fluxes from one side this side the light receiver 4. The differential value between the detection voltage of the light receiver 4 when being screened by only the screen board 9 and the detection voltage of the light receiver 4 when a table 12 is positioned in the specified position is found, and this is stored as a reference value. The positioning of the work table 12 into the specified position is performed as follows: The differential value between the detection voltage of the light receiver 4 when luminous fluxes is intercepted by only the screen board 9 and the detection voltage of the light receiver 4 at the time of the work table 12 shifting transversely is obtained, and the work table 12 is positioned in the position where the differential value substantially becomes the reference value.</p> |
