A method and system are disclosed for observing and aligning a beam of light in the sample chamber of a charged particle beam (CPB) system, such as an electron microscope or focused ion beam system. The method comprises providing an imaging aid inside the sample chamber with a calibration surface configured such that when illuminated by light, and simultaneously illuminated by a CPB, the intensity of the secondary radiation induced by the CPB is different in regions also illuminated by light relative to regions with lower light illumination levels, thereby providing an image of the light beam on the calibration surface. The image of the light beam may be used to align the light beam to the charged particle beam.