The accuracy is defined as relative angular error (inclination) of the mirror facets. There are overall tracking accuracy expressed in arc-seconds, peak to peak, and adjacent facet to facet tracking accuracy also expressed in arc-seconds. Dynamic pyramidal angle error will have an effect on the scanning image in the cross scan direction. If there is no pyramidal angle error on the facet of the mirror, the incident beam, which is perpendicular to the facet, will be reflected back on the same plane. When a pyramidal angle error is introduced at an angle Į, the incident beam is reflected back at an angle of 2Į. Users should know this doubling angle error and be aware of it when specifying the acceptable pyramidal angle error.