Nano-topography on axisymmetric aspherical ground surfaces

Recently, axisymmetric aspherical lenses are being increasingly installed in optical devices such as digital cameras. As the pixel number of digital image sensors increases, both high form accuracy and fine surface roughness are required, compared with conventional products. However, distortion in an optical image occurs even if an axisymmetric aspherical lens, which has high form accuracy and fine surface roughness, is used. The distortion of the optical image is caused by the surface nano-topography, which is generated in the grinding process. In this paper, the relationship between grinding conditions and the distribution of the nano-topography is investigated. In addition, a fluctuation-free grinding machine was developed to control the nano-topography.