The present invention provides an apparatus and method for correcting an inspection reference pattern image in order to properly inspect a pattern image of a specimen. The reflective pixel array substrate can be made by utilizing five photo masks only. Changes in the amplitude and phase of the detected signal are directly and uniquely related to the transfer function of the device under test. The light fixtures disclosed herein can be used in both high bay and low bay light fixtures. The anion exchange resin is separated from the dispersion after the fluorosurfactant content has been reduced.