Production of an Encoder Plate by Magnetic Lithography

By using the magnetic lithography technique previously reported, an optical grating can be easily formed not only on a plane, but also on a convex or concave surface. The optical characteristics of this relief-type grating depend on its cross-sectional shape. To apply this technology to encoder plates, it is important to investigate the factors determining the shape of a grating produced by magnetic lithography. In order to improve the encoder's performance, proper application of magnetic lithography must control the cross-sectional shape of the grating to produce a grating that has no Fraunhofer zeroth-order diffraction light spot. Results show that there is good repeatability in the grating characteristics in production. The conditions for development of such gratings are investigated.