Study on Precision Grinding of Micro Aspherical Surface (4th Report)

Abstract

Needs of digital devices increase rapidly in recent years, and the demand for a micro axis-symmetric aspherical glass lens of large numerical aperture is expanding rapidly especially in that device. Moreover blue lasers have been increasingly used to make wavelengths short and the maximum tangent angle of the aspheric shape has increased. Therefore ultra-precision grinding technology of ceramic dies became to be a core technology. Authors have successfully developed the 45 degrees tilted grinding method, and ultra-precision micro aspherical shape has been obtained. The improvement of the form accuracy will be required because the specifications of micro lenses become more and more strict in future. However, the shape correction cannot be done satisfactorily, because the wheel wear is not equal and the grinding point on the wheel moves. In this paper, a new grinding method is proposed to solve the above problems. In this method, three-axes (X, Y, Z) are controlled simultaneously so that the position of the grinding point on the diamond wheel is fixed. Then the grinding system was developed and grinding experiments using micro symmetric aspherical dies of tungsten carbide were carried out.