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On-Axis Interferometric Measurement For Tool Positioning In Ultra-Precision Single-Point Machining

As part of a programme of research into single-point diamond machining to cut-depths of the order of 100nm using an ultra-precision lathe, it was required to continuously monitor and control the axial position of the tool when used in the facing mode. This was done in combination with interferometric monitoring of the rotating spindle/face-plate. Two versions of combined interferometer and piezoelectric actuator are described in which the tool in-feed and optical axes are colinear. In the second version, the tool position is made with measurement interferometrically with respect to the rotating surface.