A three dimensional printing system includes a plurality of light engines, an alignment article, a camera, and a controller. The plurality of light engines define a corresponding plurality of build fields which overlap and define a build plane. The alignment article carries an alignment calibration image and is configured to be mounted in the three dimensional printing system with the alignment calibration image proximate to the build plane and in facing relation with the plurality of light engines. The alignment calibration image defines a dark field with an array of reflective alignment targets. The camera is mounted to be in facing relation to the alignment calibration image. The controller is configured to operate at least the light engines and the camera to individually align the light engines to the alignment calibration image.