Systems and methods for calibrating a solid-imaging system (10) are disclosed. A calibration plate (110) having a non-scattering surface (140) with a plurality (150) of light-scattering fiducial marks (156) in a periodic array is disposed in the solid-imaging system. The actinic laser beam (26) is scanned over the fiducial marks, and the scattered light (26S) is detected by a detector (130) residing above the calibration plate. A computer control system (30) is configured to control the steering of the light beam and to process the detector signals (SD) so as to measure actual center positions (xA, yA) of the fiducial marks and perform an interpolation that establishes a calibrated relationship between the angular positions of the mirrors and (x,y) locations at the build plane (23). The calibrated relationship is then used to steer the laser beam in forming a three-dimensional object (50).