A calibration and part inspection method for the inspection of ball grid array, BGA, devices. One or more cameras image a precision pattern mask with dot patterns deposited on a transparent reticle. The precision pattern mask is used for calibration of the system. A light source and overhead light reflective diffuser provide illumination. A camera images the reticle precision pattern mask from directly below. An additional mirror or prism located below the bottom plane of the reticle reflects the reticle pattern mask from a side view, through prisms or reflective surfaces, into the camera. By imaging more than one dot pattern the missing state values of the system can be resolved using a trigonometric solution. The reticle with the pattern mask is removed after calibration and the BGA to be inspected is placed with the balls facing downward, in such a manner as to be imaged by a single camera, or optionally, via additional cameras. The scene of the part can thus be triangulated and the dimensions of the BGA are determined.