High-accuracy fabrication of a sinusoidal grid surface over a large area by fast tool servo (improvement of fabrication accuracy in local areas of the grid surface)

This paper describes a diamond turning fabrication system for a sinusoidal grid surface, which is a superposition of periodic sinusoidal waves along the X- and Y-directions. The wavelength and amplitude of the sinusoidal wave in each direction are 100 μm and 100 nm, respectively. The fabrication system, based on fast-tool-servo (FTS), has the ability to generate the angle grid surface over an area of φ150 mm. This paper focuses on the improvement of the fabrication accuracy in local areas. Each of these areas is approximately 1 mm × 1 mm, which can be imaged by an interference microscope. Specific fabrication errors, caused by the round nose geometry of the diamond cutting tool and the data digitization, for the manufacturing process are successfully identified by Discrete Fourier Transform of the microscope images. Compensation processes are carried out to achieve a reduction of the errors. As a result, the fabrication errors in local areas of the angle grid surface are reduced to 1/10.