JPH05241090

PURPOSE:To provide a polygon mirror whose working is facilitated, having a small number of man-power for assembling and also whose rotational performance is extremely good. CONSTITUTION:In the polygon mirror constituting a radial dynamic pressure between the inner peripheral surface of a ceramic ring and the outer peripheral surface of a fixing shaft by making the fixing shaft on a fixing body side pass through the ceramic ring 1 as to a rotating body having such a structure that a mirror surface forming body 3 is fixed to yokes 2 and 5 fixed on the ceramic ring 1, and also constituting a thrust dynamic pressure bearing of both end surfaces of the ceramic ring and the counter surface of a thrust plate fixed to the fixing body side so as to be opposite to both end surfaces of the polygon mirror, the rotating body is integrally formed by casting the ceramic ring 1, the yokes 2 and 5 and the mirror surface forming body 3 with a mirror surface forming material such as aluminium material and they are integrally formed.