Abstract: A method of registering one image (6) of a reticle plate (5) formed by a projection lens (21) of an optical system on a coated substrate (1) with features created previously on the substrate by an earlier image projection, comprises forming a reference pattern (7) on the substrate and monitoring the changes in position, caused by relative movement of the reticle plate (5) past the substrate (1) in a scan (or x-) direction, of the reference pattern relative to the optical system prior to forming the said one image on the coated substrate. The method is characterised in that the reference pattern (7) is interrogated by optical means (8, 9, 10, 11) operating through the projection lens (21) as the reticle plate (5) approaches a position in which an image (6) thereof will be in register with said features created previously to permit creation of said image correctly on the coated substrate without stopping the movement in the scan direction.

Abstract: An integrated circuit for measuring conductor misalignment comprises: a set of 2n+1 conductor pairs where n is a predetermined positive integer; each conductor pair includes a U-shaped conductor having a central axis; each conductor pair also includes a rectangular shaped conductor having a central axis and which is narrow enough to fit between the legs of the U-shaped conductor provided their central axis are aligned; and the rectangular shaped conductor of each conductor pair has its central axis a distance .delta.+k.DELTA.d from the central axis of the U-shaped conductor where .DELTA.d is a fixed increment, k is an integer between +n and -n that differs for each conductor pair, and .delta.is a misalignment between the central axis of each conductor pair.