Correlation methods of identifying defects in imaging devices

Abstract

An automated system for determining artifacts in images indicating defects in an imaging device being tested employs a constant radiation source which supplies radiation of spatially uniform intensity to the imaging device to be tested. The imaging device then creates a flood image A.sup.(0). A region of interest (ROI) mask means for all pixel values of flood image A.sup.(0) sets values to zero outside of the imaging devices field of view to produce a flood image A.sup.(1). An image normalization means normalizes flood image A.sup.(1) to have an average value of zero producing a normalized flood image A. A correlation means performs an autocorrelation of normalized flood image A to produce a correlation field which is then masked to select portions of the correlation field. The correlation values of the selected regions are summed, the squares of the correlation values are summed and the resulting sums are normalized for mask shape and flood image intensity to determine and quantify the presence of specific artifacts. These normalized summed values may be compared to predetermined thresholds to determine if the artifacts have a magnitude above an acceptable level. Based upon the results of the comparison, a corrective action may be taken such as removing the imaging device from a manufacturing line or adjusting the imaging device and retesting it.