KINETIC FLUID BEARING TYPE SCANNER UNIT

PURPOSE:To obtain high rotational precision by forming center holes at both ends of a rotating shaft and boring a case so that the center shaft of a center pressing base or adjusting jig is inserted into the center hole of the rotating shaft. CONSTITUTION:When a motor stator 20 begins to be powered on, a motor rotor 19 rotates the rotating shaft 12, a disk 15, and a polygonal mirror 17. This polygonal mirror has its outer peripheral surface worked into about 4-12 flat specular surfaces and reflects laser light from an incidence window 13A out of the window. At this time, two herringbone groups of a sleeve 11C produce pressure as the relative speed to the rotating shaft 12 increases, and the rotating shaft 12 is centered to maintain high rotational precision. Further, the spiral groove 16A of a thrust bearing 16 generates pressure with the lower end surface 15A of the disk 15 and rotates stably without contacting. Consequently, the constitution with the high rotational precision is obtained.