| 摘要 |
PURPOSE:To dynamically measure the radial unevenness of a rotating faces without the influence of rotating jitter due to the rotation of a scanner motor by making two laser beams incident upon a polygon mirror. CONSTITUTION:A laser beam L1 from a laser light source 2 is made incident upon the rotating polygon mirror 1 with an angle and its reflected beam L2 is led into a position detector 3 through a cylindrical lens 7. On the other hand, a beam L3 from a laser light source 4 is transmitted into a half mirror 5 and made incident upon the polygon mirror 1. When the incident light L4 is made vertical to the face of the polygon mirror 1, a reflected beam L5 is made incident upon the half mirror 5 and its reflected beam L6 is made incident upon a trigger generator 6. Thereby, a trigger signal is generated from the trigger generator 6 under said status of the polygon mirror 1 and the face unevenness value of the polygon mirror face can be dynamically measured by observing the output signal of the detector 3. |
