Optical metrological scale and laser-based manufacturing method therefor

摘要

A reflective metrological scale has a metal tape substrate and a scale pattern of elongated side-by-side marks surrounded by reflective surface areas of the substrate. 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 and darkened to provide an enhanced optical reflection ratio with respect to surrounding surface areas. A manufacturing method includes the repeated steps of (1) creating a scale mark by irradiating the substrate surface at a mark location with 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.