OPTICALLY TRANSMISSIVE SUBSTRATE HAVING A FIDUCIAL MARK AND METHODS OF ALIGNING OPTICALLY TRANSMISSIVE SUBSTRATES

摘要

An article comprises an optically transmissive substrate comprising a plurality of functional elements and an integral fiducial mark. The substrate has a critical angle for total internal reflection, and a length and a width defining a reference plane. The substrate comprises an integral fiducial mark disposed on the major surface. The integral fiducial mark comprises at least one substantially ellipse-like feature formed by first and second frustoconical surfaces that together with a reference line that is normal to the reference plane define respective first and second half angles. The first and second half angles are less than or equal to 90 degrees minus the critical angle for total internal reflection expressed in degrees. A method comprises: providing an optically transmissive substrate according to the present disclosure; precisely detecting a position of the fiducial mark with aid of a machine vision system; and optionally precisely aligning the substrate.