Alignment turning is the only method by which all relevant parameters of a mounted lens can be aligned, in particular the gap between two apex points and the contact surface.
In addition, a large number of different cell sizes can be processed. And finally, high precision turning machines achieve excellent production accuracies of up to 0.5 μm. The alignment turning method is described in the figures below (Fig. 3). In alignment turning, first the lens cell is fixed in an adjustable alignment chuck with the lens in place. Then the position of the optical axis of the lens to the spindle axis is measured with the OptiCentric® system. Using this alignment chuck, the lens is then aligned so that its two centers of curvature are located as closely as possible to the axis of rotation of the spindle.
Then the spindle is rotated and the contact surfaces of the cell are machined with a sharp (diamond) turning tool, resulting in a precisely machined surface of the cell, aligned parallel to the spindle axis. In addition to the outer surface of the cell, it is also possible to machine the front and rear contact surface during the turning process. To do this the turning tool is moved perpendicular to the spindle axis instead of along the optical axis.