Automatic aperture size measurement apparatus and process

Apparatus for automatically measuring aperture size of a slotted apertured material having a plurality of slots each having a longitudinal axis including a comparator mask means having a plurality of alternate light transparent and opaque sectors, means for supporting and transporting said slotted apertured material and comparator mask means, means disposed on opposite sides of said slotted apertured material and comparator mask means for providing and detecting a light beam directed to pass therethrough, and a computer means coupled to said means for supporting and transporting said slotted apertured material and said comparator mask means and responsive to said means for detecting said light beam for providing a signal representing light transmission of said slots, said apparatus characterized by the improvement of a size control means having a rhombic-shaped aperture with a diagonal axis disposed within said light beam with said aperture and said slotted apertured material and said comparator mask means movable with respect to one another along said diagonal axis whereby the rate of change of light passing through said slots is relatively uniform with diagonal movement uniformity.

In a process for automatically measuring aperture size of a slotted apertured material having a plurality of slots each having a longitudinal axis including the steps of ovelaying said slotted apertured material with a comparator mask having a plurality of alternately spaced light transparent and opaque sectors;

• positioning a light source and a light detector on opposite sides of said slotted apertured material and overlaying comparator mask to provide a light beam directed therethrough and utilizing light transmitted through said slotted apertured material and comparator mask to provide a detected signal for calculating the width of said slotted apertured material, said process characterized by the improvement including the step of restricting said light beam impinging said light detector to a rhombic-shaped configuration having a diagonal axis normal to said longitudinal axis of said slots to provide a relatively uniform rate of change of light transmission with movement of said slotted apertured material and said light beam with respect to one another along said diagonal axis.