Patent ID: 8466943

Claim:
A method of producing precision marks for a metrological scale, employing apparatus including: a scale substrate to be marked at repeated instants by a laser and thereby forming a metrological scale; a laser operable so as to provide light pulses for forming scale markings at the substrate; a displacement device for causing relative displacement between the substrate and the location at which the light is incident on the substrate; and a controller for controlling the relative displacement and the laser, the method comprising the steps, in any suitable order, of: operating the displacement mechanism so as to cause relative displacement between the substrate and the light; using the controller to control the relative displacement and to operate the laser so as to produce light pulses at the substrate; characterised in that: the laser produces a plurality of ultra-short output pulses of a fluence at the substrate such that the metrological scale marks are formed by laser ablation, wherein the plurality of ultra-short output pulses have a duration such that the scale markings are formed on the scale substrate by a laser ablation mechanism in which the molten stage is omitted.