| 摘要 |
<p>Method of producing printing plates by means of a laser beam, said laser beam being scanned by means of a rotating polygonal mirror (32). According to the invention the rotational movement is transferred to the polygonal mirror (32) by means of a magnetic coupling, possible oscillations being dampened by a hysteresis-dampened, i.e. a faraday-dampened, magnetic coupling. The magnetic coupling is formed by intermeshing, radially projecting members, which can be slightly rotated relative to one another and which comprise strong magnets (62) . The resulting rotational accuracy is 6 ppm per rotation. In this manner it is possible to perform a laser scanning at a high speed while maintaining a high accuracy. The rotational shaft of the polygonal mirror (32) is disposed in an air bearing and comprises a cylinder (53) of a relatively heavy material, such as granite.</p> |
