The invention relates to a substrate comprising an optical position mark for being read-out by an optical recording head for emitting light of predetermined wavelength, preferably red or infra-red light, more in particular of 635 nm light, the optical position mark having a mark height, a mark length and a predetermined known position on the substrate, the optical position mark extending along a longitudinal direction and being arranged for varying a reflection coefficient of the position mark along said longitudinal direction, wherein the optical position mark comprises: a first region having a first reflection coefficient and a first width; a second region neighboring the first region and forming a first region pair, the second region having a second reflection coefficient and a second width, and the second reflection coefficient being different from the first reflection coefficient, wherein the first region comprises sub-wavelength structures in comparison with a wavelength of the predetermined wavelength light.