| 摘要 |
PURPOSE:To reduce the size and weight of the rotating polygon mirror device by rotating the polygon mirror 5 around a hemispherical revolving shaft. CONSTITUTION:The hemispherical revolving shaft 4 is integrally molded to the revolution center of the polygon mirror 5 and spiral grooves 4a are formed on the surface thereof at the time of working said mirror. Magnets 7 are embedded in the polygon mirror 5 so as to enclose the revolving shaft 4. This revolving shaft 4 is sandwiched by an upper bearing 2 (provided with a hemispherical recess) and a lower bearing 3 and plural pieces of coils 6 are installed to enclose the circumferences of these bearings. A dynamic pressure is generated by the spiral grooves 4a formed on the revolving shaft 4 and the polygon mirror 5 starts rotating without contacting while the mirror is supported by the upper bearing 2 and the lower bearing 3 when the rotation of the polygon mirror 5 is started by the effect of the coils 6 supplied with current and the magnets 7. The thickness, size and weight of the polygon mirror are thereby reduced. |
