Abstract: A means for the measurement of the alignment error between a plurality of ordinate reference frames and a relatively absolute reference frame determines all three degrees of freedom utilizing a single beam of light with relatively narrow angular extent. The measurement means has a light source, collimator, a plurality of reflecting folding mirrors and a pair of retroreflectors rigidly fixed to each coordinate reference frame. As the collimated light beam strikes a folding mirror it is reflected toward the corresponding coordinate reference frame where it is reflected back by the retroreflectors. The angles of tilt, twist and rotation at which it is reflected are representative of the misalignment of the coordinate reference frame. The folding mirror then reflects the retroreflected beam back toward the source, where the beams are detected.

Abstract: A straight line whose azimuth angle is to be measured, such as the angle of a gap of a magnetic head assembly relative to a disk radius, is imaged on an evaluation plane via a lens and a pair of deflecting mirrors, the first of which is semi-transparent. The mirrors are each inclined at a different angle from a common pivot line. The angular difference is such that the images do not touch and only one end portion of each image from the mirrors lies in the image field. The lateral spacing of these end portions is a function of the azimuth angle. A mask blocking out the center portion of the image may be used to assist in the end portion definition.

Abstract: Disclosed is an apparatus and method which permits a manufacturer to precisely place a desired image on a screen to be used in a screen printing process. This result is accomplished by establishing a predetermined relationship between the screen frame and the image positive from which the image is to be formed on the screen. The method requires providing indicia of translational and rotational orientation on the image positive and aligning the image positive with respect to the screen frame by adjusting the position of the image positive in light of the location of separately-provided reference indicia located in a predetermined position with respect to the screen frame. Aligning the image positive indicia with the reference indicia is most easily accomplished by providing a microscope through which respective pairs of indicia may be observed simultaneously. The disclosed apparatus provides a means for readily performing the above steps.