The majority of particles in a beam are located close to the beam axis, called the beam core. However, particles in the tail distribution of the transverse beam profile can never be completely avoided and are commonly referred to as beam halo. The light originating from or generated by the particle beam is often used for non-or least destructive beam profile measurements. Synchrotron radiation, optical transition, or diffraction radiation are examples of such measurements. The huge difference in particle density between the beam core and its halo, and therefore the huge intensity ratio of the emitted light is a major challenge in beam halo monitoring. In this contribution, results from test measurements using a flexible core masking technique are presented indicating way to overcome present limitations. This technique is well-known in e.g. astronomy, but since particle beams are not of constant shape in contrast to astronomical objects, a quickly adjustable mask generation process is required. The flexible core masking technique presented in this paper uses a micro mirror array to generate a mask based on an automated algorithm.