The sample stage of an array microscope is tilted in the scanning direction such that the best-focus plane of the array microscope intersects the surface of the sample during the scan. As a result of the tilt, the distance from the sample surface of each miniaturized microscope spanning the array varies from point to point on the surface. Accordingly, the best focal distance for each such point on the sample surface is identified by tracking the quality of its focus as the sample surface travels across the rows of microscopes in the array. Best focus may be detected using any known technique, such as by measuring spatial frequency content and recording the scan position corresponding to maximum mid-range frequency content. This information is used to develop a best-focus axial-position map for use while performing a subsequent measurement scan.