Patent ID: 8610901
Filing Date: 2013-12-17
Classification: G01B

Abstract:
1. A method for determining a flatness characteristic for a reflective facet of a polygon assembly, comprising: a) rotating a polygon assembly comprising a plurality of reflective facets in a dynamic test setup at a speed the polygon assembly is expected to experience during operation of system equipment with a raster output scanning subsystem comprising the polygon assembly; b) selectively directing a light beam from a light source toward the rotating polygon assembly such that at least a portion of light from the light beam is reflected by consecutive reflective facets of the plurality of reflective facets during revolutions of the polygon assembly, reflected light from the corresponding reflective facet of the rotating polygon assembly passing through a first focusing lens that directs a first spot light toward a target having a plurality of spaced-apart bars arranged to form a grating pattern that blocks a first portion of the reflected light and allows a second portion of the reflected light to pass through to a second focusing lens, the second focusing lens directing a second spot light toward a light sensor, the light sensor detecting an intensity of the second spot light; and c) measuring the intensity of the second spot light over time during revolutions of the polygon assembly to obtain a plurality of intensity measurements for each reflective facet; wherein a linear position of the first focusing lens is adjustable from a first linear position closest to the polygon assembly to a second linear position farthest from the polygon assembly.