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New approach to optical assembly and cementing

A novel method of projecting a reference axis in space for use in optical assembly of centered elements such as assembly in a barrel or in cementing multi-element lenses is presented. An axicon grating, a set of concentric, uniformly spaced circles, when illuminated with a point source of light creates a line of bright spots surrounded by concentric rings in both transmission through, and reflection from, the grating. This axis is easily interrogated with an autostigmatic microscope to gauge the distance a center of curvature, or other lens conjugate, lies from the axis created by the grating.