title: Moire null topography with uniform accuracy by double computer-generated gratings.
abstract: A method of moire null testing with two computer-generated gratings is proposed. Based on our theoretical analysis, it is concluded that uniform accuracy is possible only when the lateral derivative of the moire kernel of the project grating is a constant. Moreover, the design of the kernels of the two gratings is believed to give an equidistant straight fringe background. Therefore, the defect of the tested object from the standard shape can be easily found directly from the fringe shift, with uniform accuracy. Computer simulations as well as experimental results of the test of a toroid surface are presented.
authors.forename: J
authors.initials: J
authors.lastname: Zhang
authors.forename: L
authors.initials: L
authors.lastname: Liu