Apparatus and method for control of lasers in order to improve spectrally beam-combined laser beam quality along the plane of the SBC fiber array via spectral-to-spatial mapping of a portion of the spectrally beam-combined laser beams, detection of optical power in each of the spatially dispersed beams and feedback control of the lasers for wavelength-drift correction. The flat display device includes a flat display module, a front cover, an auxiliary support, a back cover set, and a circuit board. The invention also concerns a device and a drill rig. One of the functions includes a navigational component.