In a planar, dielectric barrier discharge system with a very short discharge gap and a large electrode area a glow-mode discharge in helium is ignited. Due to the large aspect ratio the discharge splits up into several current filaments. For an appropriate set of discharge parameters these filaments may arrange regularly or move around erratically. In the case of moving filaments, filament collisions are observed frequently leading to the annihilation of one of the collision partners.In this work the interaction process of two filaments is investigated in detail. Therefore, the surface charge distribution on the dielectric barrier acting as a memory between individual breakdowns is observed via an electro-optical crystal. Beside a pure image of the breakdown as it is seen in the emitted luminescence distribution, there is an additional charge ring around a filament in the negative surface charge distribution. The inner filament structure revealed this way can be associated with different states during the interaction process.