Optical metrological scale and laser-based manufacturing method therefor

摘要

A reflective metrological scale has a scale pattern of elongated side-by-side marks surrounded by reflective surface areas of a substrate, which may be a nickel-based metal alloy such as Invar(R) or Inconel(R) and may be a thin and elongated flexible tape. Each mark has a furrowed cross section and may have a depth in the range of 0.5 to 2 microns. The central region of each mark may be rippled or ridged and may be darkened to provide an enhanced optical reflection ratio with respect to surrounding reflective surface areas. A manufacturing method includes the repeated steps of (1) creating a scale mark by irradiating a surface of the substrate at a mark location with a series of overlapped pulses from a laser, each pulse having an energy density of less than about 1 joule per cm², and (2) changing the relative position of the laser and the substrate by a displacement amount defining a next mark location on the substrate at which a next mark of the scale is to be created.